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RSS2014 Vol. 26, No. 05
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2014,
26: 050101.
doi: 10.11884/HPLPB201426.050101
Abstract:
For the highly-enriched uranium components with reflector can avoid fissile material measurements skillfully, according to the theory of source-driven noise analysis method, this paper analyzes the highly-enriched uranium components with reflector in different material and thickness and obtains time-correlation incidence count distribution and neutron net multiplication. The results show that for the same reflector, the thicker the reflector is, the better the reflectivity is; for different material reflectors, the denser the reflector is, the more the neutron net multiplication is.
For the highly-enriched uranium components with reflector can avoid fissile material measurements skillfully, according to the theory of source-driven noise analysis method, this paper analyzes the highly-enriched uranium components with reflector in different material and thickness and obtains time-correlation incidence count distribution and neutron net multiplication. The results show that for the same reflector, the thicker the reflector is, the better the reflectivity is; for different material reflectors, the denser the reflector is, the more the neutron net multiplication is.
2014,
26: 050201.
doi: 10.11884/HPLPB201426.050201
Abstract:
As an important component of segment amplifier system，SG-Ⅲ laser facilitys power conditioning system (PCS) consists of 108 power conditioning modules (PCMs)，which are divided into six segments．With the maximum energy stored in each PCM reaches 1.2 MJ，PCS stores 110 MJ energy，and 130 MJ maximally．Each PCM produces a pulse current for driving ten groups of Xenon flshlamps，20 flshlamps in total，and provides pumping energy for segment amplifier system．The current pulsewidth is 610s，and the peak value is 0.25 MA．PCMs function requirements，compositions and structure，and design methods are introduced，as well as function requirements and design methods of the key components．Performance of the first 36 PCMs applied to SG-Ⅲ laser facility proves that the specifications of PCS meet the design requirements and can make sure the small signal gain coefficient of segment amplifier reach 5.0% per centimeter, and PCS can provide adequate pumping energy for amplifier and fit the bill of lasers．
As an important component of segment amplifier system，SG-Ⅲ laser facilitys power conditioning system (PCS) consists of 108 power conditioning modules (PCMs)，which are divided into six segments．With the maximum energy stored in each PCM reaches 1.2 MJ，PCS stores 110 MJ energy，and 130 MJ maximally．Each PCM produces a pulse current for driving ten groups of Xenon flshlamps，20 flshlamps in total，and provides pumping energy for segment amplifier system．The current pulsewidth is 610s，and the peak value is 0.25 MA．PCMs function requirements，compositions and structure，and design methods are introduced，as well as function requirements and design methods of the key components．Performance of the first 36 PCMs applied to SG-Ⅲ laser facility proves that the specifications of PCS meet the design requirements and can make sure the small signal gain coefficient of segment amplifier reach 5.0% per centimeter, and PCS can provide adequate pumping energy for amplifier and fit the bill of lasers．
2014,
26: 051001.
doi: 10.11884/HPLPB201426.051001
Abstract:
On the basis of analyzing the point diffraction wavefront error, the influence of the optical structural parameters, including the numerical aperture of objective lens, the size of pinhole and the numerical aperture under testing, on the point diffraction intensity also have been discussed in the paper. We have optimized the optical structural parameters gradually and obtained the parameters matching reference table. By comparing the measurement results by PDI system and Zygo interferometer, the difference of root mean square error is about /1000, and the interference pattern by PDI system have good contrast and brightness, which verify the rationality of the selected optical structural parameters.
On the basis of analyzing the point diffraction wavefront error, the influence of the optical structural parameters, including the numerical aperture of objective lens, the size of pinhole and the numerical aperture under testing, on the point diffraction intensity also have been discussed in the paper. We have optimized the optical structural parameters gradually and obtained the parameters matching reference table. By comparing the measurement results by PDI system and Zygo interferometer, the difference of root mean square error is about /1000, and the interference pattern by PDI system have good contrast and brightness, which verify the rationality of the selected optical structural parameters.
2014,
26: 051002.
doi: 10.11884/HPLPB201426.051002
Abstract:
Quasi regenerative amplifier is put forward, which is based on the improvement upon the regenerative amplifier. In the amplifying system, the large-aperture amplifiers are used and the beam is imaged in the amplifier to keep the shape of the beam in the course of amplifying. Experiments on the feasibility of this amplifying concept show that this kind of amplifying system even based on low-gain amplifiers can achieve high system gain and can output high-energy pulses.
Quasi regenerative amplifier is put forward, which is based on the improvement upon the regenerative amplifier. In the amplifying system, the large-aperture amplifiers are used and the beam is imaged in the amplifier to keep the shape of the beam in the course of amplifying. Experiments on the feasibility of this amplifying concept show that this kind of amplifying system even based on low-gain amplifiers can achieve high system gain and can output high-energy pulses.
2014,
26: 051003.
doi: 10.11884/HPLPB201426.051003
Abstract:
By ultrasonic vibration, the carbon-water nanofluids were made from the carbon nanotubes and a certain proportional dispersant in deionized water. Comparing with thermal conductivity and dynamic viscosity, the effects of the mass fraction were analyzed. The test results indicate that the thermal conductivity of multi-wall and single-wall carbon nanofluids are improved with the increasing of carbon particles concentration, but compared with multi-wall carbon nanofluids, the viscosity of single-wall carbon nanofluids greatly increases. Based on the measured results, the multi-wall carbon would be more applicable to heat transfer enhancement.
By ultrasonic vibration, the carbon-water nanofluids were made from the carbon nanotubes and a certain proportional dispersant in deionized water. Comparing with thermal conductivity and dynamic viscosity, the effects of the mass fraction were analyzed. The test results indicate that the thermal conductivity of multi-wall and single-wall carbon nanofluids are improved with the increasing of carbon particles concentration, but compared with multi-wall carbon nanofluids, the viscosity of single-wall carbon nanofluids greatly increases. Based on the measured results, the multi-wall carbon would be more applicable to heat transfer enhancement.
2014,
26: 051004.
doi: 10.11884/HPLPB201426.051004
Abstract:
A 4-channel model of coherent beam combination is established according to Fraunhofer diffraction theory, and the influence of tilt phase error on coherent beam combination with different duty ratios is studied. By using Eulers rotation, tilt angles of sub-beams are transformed into tilt phase errors, and then introduced into the combination model. Far-field intensity distribution of the combined beam with different duty ratios and tilt angles is calculated, and the influence of duty ratio and tilt angle is analyzed. Simulation results show that far-field intensity in the Airy disk decreases with increasing tilt angle, which means degraded combination effect. The dependencies of power in the bucket (PIB) and factor on tilt angle with different duty ratios are calculated. It is demonstrated that both of the two criteria degenerate when tilt angle increases. It is concluded that to reach the required criteria, tilt angles of sub-beams should be reduced within certain limit by utilization of correction component such as fast steering mirror.
A 4-channel model of coherent beam combination is established according to Fraunhofer diffraction theory, and the influence of tilt phase error on coherent beam combination with different duty ratios is studied. By using Eulers rotation, tilt angles of sub-beams are transformed into tilt phase errors, and then introduced into the combination model. Far-field intensity distribution of the combined beam with different duty ratios and tilt angles is calculated, and the influence of duty ratio and tilt angle is analyzed. Simulation results show that far-field intensity in the Airy disk decreases with increasing tilt angle, which means degraded combination effect. The dependencies of power in the bucket (PIB) and factor on tilt angle with different duty ratios are calculated. It is demonstrated that both of the two criteria degenerate when tilt angle increases. It is concluded that to reach the required criteria, tilt angles of sub-beams should be reduced within certain limit by utilization of correction component such as fast steering mirror.
2014,
26: 051005.
doi: 10.11884/HPLPB201426.051005
Abstract:
The paper investigates a fiber-coupled method based on single emitter diode laser mounted on copper sub-heatsink by steps and mirror model. The output beam collimated with aspherical cylindrical lens and cylindrical lens in the fast and slow axis directions could be coupled into a fiber of 100 m core diameter and 0.22 numerical aperture. The measurement result shows that the continuous wave(CW) fiber output power can achieve 21.8 W, brightness is 1.83 MW/(cm2sr) and the total coupling efficiencies are 70.32% at operation currents of 7.0 A.
The paper investigates a fiber-coupled method based on single emitter diode laser mounted on copper sub-heatsink by steps and mirror model. The output beam collimated with aspherical cylindrical lens and cylindrical lens in the fast and slow axis directions could be coupled into a fiber of 100 m core diameter and 0.22 numerical aperture. The measurement result shows that the continuous wave(CW) fiber output power can achieve 21.8 W, brightness is 1.83 MW/(cm2sr) and the total coupling efficiencies are 70.32% at operation currents of 7.0 A.
2014,
26: 051006.
doi: 10.11884/HPLPB201426.051006
Abstract:
According to the theoretical model of K9 glass irradiated by pulsed CO2 laser, a numerical simulation was performed to calculate thermal stress distribution in K9 glass sample irradiated by pulsed CO2 laser. The time characteristic of the thermal stress was demonstrated. On the basis of the analysis of damage results, an optimal radius was presented to express the laser-induced damage resistance of K9 glass. The simulation results indicated that the damage effect was dominated by circular stress. Moreover, this thermal stress would diffuse as shock wave and oscillated obviously inside of the K9 glass sample. The simulation results also showed that the effect of laser irradiation on samples can be affected considerably by the change of radius of the sample. Finally, the universality of the proposed optimal radius of K9 glass was validated.
According to the theoretical model of K9 glass irradiated by pulsed CO2 laser, a numerical simulation was performed to calculate thermal stress distribution in K9 glass sample irradiated by pulsed CO2 laser. The time characteristic of the thermal stress was demonstrated. On the basis of the analysis of damage results, an optimal radius was presented to express the laser-induced damage resistance of K9 glass. The simulation results indicated that the damage effect was dominated by circular stress. Moreover, this thermal stress would diffuse as shock wave and oscillated obviously inside of the K9 glass sample. The simulation results also showed that the effect of laser irradiation on samples can be affected considerably by the change of radius of the sample. Finally, the universality of the proposed optimal radius of K9 glass was validated.
2014,
26: 051007.
doi: 10.11884/HPLPB201426.051007
Abstract:
For process of optical components having defects such as sharp projections, pits and scratches at the micro, abrasive waterjet impinging with low mass concentrations is proposed. Starting from the elastic contact, the critical velocity of plastic contact between components and waterjet particles is deduced. The critical impinging velocity of ductile to brittle transfer is introduced. Thus the velocity range of the ductile removal is clearly defined. Combined with specific parameters, K9 and fused silicas velocity range of the ductile removal are simulated. Using the single particle impinging removal model, these two materials' impinging removal in ductile removal manner is simulated. The results show that the critical velocity of plastic contact for fused silica is higher than K9s, but the velocity of ductile to brittle transfer is reversed. Thus, the velocity range of ductile removal for fused silica is a subinterval of that for K9. The impinging removal of these two materials increases with the increase of impinging velocity. However, the harder fused silica is less resistant to impinging than K9 and it is easier to be removed by impinging.
For process of optical components having defects such as sharp projections, pits and scratches at the micro, abrasive waterjet impinging with low mass concentrations is proposed. Starting from the elastic contact, the critical velocity of plastic contact between components and waterjet particles is deduced. The critical impinging velocity of ductile to brittle transfer is introduced. Thus the velocity range of the ductile removal is clearly defined. Combined with specific parameters, K9 and fused silicas velocity range of the ductile removal are simulated. Using the single particle impinging removal model, these two materials' impinging removal in ductile removal manner is simulated. The results show that the critical velocity of plastic contact for fused silica is higher than K9s, but the velocity of ductile to brittle transfer is reversed. Thus, the velocity range of ductile removal for fused silica is a subinterval of that for K9. The impinging removal of these two materials increases with the increase of impinging velocity. However, the harder fused silica is less resistant to impinging than K9 and it is easier to be removed by impinging.
2014,
26: 051008.
doi: 10.11884/HPLPB201426.051008
Abstract:
A mathematical model was developed in describing flow behaviors of a microchannel cooler of solid-state laser. The model was solved numerically using the commercial software, Fluent, and the effect of microchannel size and structure on the transition Reynolds number (Rec) was analyzed. Comparison between model prediction and experimental data in literature shows a good agreement, which verifies the reliability of the model. The results also show that the equivalent diameter has little effect on Rec. The magnitude of the transition Rec depends largely upon the contraction ratio. The Rec s under different contraction ratios were determined.
A mathematical model was developed in describing flow behaviors of a microchannel cooler of solid-state laser. The model was solved numerically using the commercial software, Fluent, and the effect of microchannel size and structure on the transition Reynolds number (Rec) was analyzed. Comparison between model prediction and experimental data in literature shows a good agreement, which verifies the reliability of the model. The results also show that the equivalent diameter has little effect on Rec. The magnitude of the transition Rec depends largely upon the contraction ratio. The Rec s under different contraction ratios were determined.
2014,
26: 051009.
doi: 10.11884/HPLPB201426.051009
Abstract:
The precision of flat measured by relative interference is limited by the precision of standard transmission flat. The absolute measurement method can improve the measure precision by removing the error of standard transmission flat. The absolute measurement of plat with multiple translation method is an effective way to test plat surfaces with high accuracy. The surface under test can be expressed by polynomial function. Different surface profile is obtained by orthogonally shifting the tested flat in two directions orthogonal，then the absolute surface is gained by fitting of polynomial coefficients using the least squares. The theory formula of multiple translation method is deduced，and the error caused by number of sampling points, times and interval of translation are analyzed using the simulation. The results of simulation show that the root-mean-square(RMS)of residual figure error is 5.11810-13.Thus the method can realize high accuracy measurement of flat surfaces.
The precision of flat measured by relative interference is limited by the precision of standard transmission flat. The absolute measurement method can improve the measure precision by removing the error of standard transmission flat. The absolute measurement of plat with multiple translation method is an effective way to test plat surfaces with high accuracy. The surface under test can be expressed by polynomial function. Different surface profile is obtained by orthogonally shifting the tested flat in two directions orthogonal，then the absolute surface is gained by fitting of polynomial coefficients using the least squares. The theory formula of multiple translation method is deduced，and the error caused by number of sampling points, times and interval of translation are analyzed using the simulation. The results of simulation show that the root-mean-square(RMS)of residual figure error is 5.11810-13.Thus the method can realize high accuracy measurement of flat surfaces.
2014,
26: 051010.
doi: 10.11884/HPLPB201426.051010
Abstract:
We built a chromatic confocal microscope for micro metrology. Based on dispersive aberration principle and optimization of lens glasses, a dispersive objective was designed, of which the dispersive aberration was linear to wavelength. The linear dispersive aberration could help to balance the sensitivity of chromatic confocal microscope. Designed dispersive objective is of large dispersive aberration, small longitudinal aberration and long working distance. Influence of system parameters on optical sectioning was analyzed and simulation results were exhibited. Chromatic confocal microscope was built, calibrated and tested. Experimental results show that the measuring range is 1 mm, the resolution is better than 0.5 m and the measuring error in full range is less than 2 m. To test the performance of microscope, profile of standard height was scanned and thickness of transparent plate was measured.
We built a chromatic confocal microscope for micro metrology. Based on dispersive aberration principle and optimization of lens glasses, a dispersive objective was designed, of which the dispersive aberration was linear to wavelength. The linear dispersive aberration could help to balance the sensitivity of chromatic confocal microscope. Designed dispersive objective is of large dispersive aberration, small longitudinal aberration and long working distance. Influence of system parameters on optical sectioning was analyzed and simulation results were exhibited. Chromatic confocal microscope was built, calibrated and tested. Experimental results show that the measuring range is 1 mm, the resolution is better than 0.5 m and the measuring error in full range is less than 2 m. To test the performance of microscope, profile of standard height was scanned and thickness of transparent plate was measured.
2014,
26: 051011.
doi: 10.11884/HPLPB201426.051011
Abstract:
In order to effectively solve the security risk from energy extraction of high saturation fluency materials such as Yb-doped materials, a noval time-multiplexing amplification technology is given. By lasers polarization characteristics and the free space propagation delay, laser pulse serials with various pulse parameters is obtained and the experiment is carried out. Comparing time-multiplexing amplification with single-pulse amplification, it indicates that the gain has no significant difference. For our laser fluency, subpulse interval from 14 ns to 22 ns has little influence on laser gain. It fully illustrates that when keeping certain total laser fluency, time-multiplexing amplification can reduce the subpulses fluency and the risk of optical element. So the storage energy can be effectively extracted.
In order to effectively solve the security risk from energy extraction of high saturation fluency materials such as Yb-doped materials, a noval time-multiplexing amplification technology is given. By lasers polarization characteristics and the free space propagation delay, laser pulse serials with various pulse parameters is obtained and the experiment is carried out. Comparing time-multiplexing amplification with single-pulse amplification, it indicates that the gain has no significant difference. For our laser fluency, subpulse interval from 14 ns to 22 ns has little influence on laser gain. It fully illustrates that when keeping certain total laser fluency, time-multiplexing amplification can reduce the subpulses fluency and the risk of optical element. So the storage energy can be effectively extracted.
2014,
26: 051012.
doi: 10.11884/HPLPB201426.051012
Abstract:
An optimized stability control system is revealed basing on the research of the working environment of massive high power laser facilities. The Ethernet and EtherCAT bus serve as the basic framework. An open and heterogeneous computer control system is designed with software basing on a three-layer structure with CORBA middleware and C/S call mode. The system can overcome the adverse electromagnetic environment and dispersed objectives in the kJ laser facility. All the objects can be controlled under certain sequence to satisfy the demands of physical experiments.
An optimized stability control system is revealed basing on the research of the working environment of massive high power laser facilities. The Ethernet and EtherCAT bus serve as the basic framework. An open and heterogeneous computer control system is designed with software basing on a three-layer structure with CORBA middleware and C/S call mode. The system can overcome the adverse electromagnetic environment and dispersed objectives in the kJ laser facility. All the objects can be controlled under certain sequence to satisfy the demands of physical experiments.
2014,
26: 051013.
doi: 10.11884/HPLPB201426.051013
Abstract:
The timing sequence between different pulses in SG-Ⅲ laser facility is controlled with three arbitrary waveform generators. External clock and external trigger, which are provided by the synchronization system, are used to make sure that all the three arbitrary waveform generators can work synchronously. The temporal waveform and phase change after reboot of the arbitrary waveform generator can be corrected through close-loop control. The verification experiment shows that the three arbitrary waveform generators can work synchronously using this technology, which ensures the synchronization error control of the SG-Ⅲ laser facility.
The timing sequence between different pulses in SG-Ⅲ laser facility is controlled with three arbitrary waveform generators. External clock and external trigger, which are provided by the synchronization system, are used to make sure that all the three arbitrary waveform generators can work synchronously. The temporal waveform and phase change after reboot of the arbitrary waveform generator can be corrected through close-loop control. The verification experiment shows that the three arbitrary waveform generators can work synchronously using this technology, which ensures the synchronization error control of the SG-Ⅲ laser facility.
2014,
26: 051014.
doi: 10.11884/HPLPB201426.051014
Abstract:
During the assembly of large plano-optics, astigmatism will be generated when the assembly manner is improper. This astigmatism has the same character in local surface and full-aperture surface. The flat stitching interferometer has the ability to measure both the local surface and the full-aperture surface. Therefore, we employ a flat stitching interferometer to inspect local the surface during assembly, by which the astigmatism is controlled. Experiments show that the local surface precision of the flat stitching interferometer arrives at 50 nm (PV) and the space rate reaches 5 mm-1, enabling intermediate frequency detection. On the other hand, the flat stitching interferometer can measure the full-aperture of optics by scanning. The test uncertainty is 100 nm and the difference relative to large aperture interferometer is less than 0.04（=632.8 nm）.
During the assembly of large plano-optics, astigmatism will be generated when the assembly manner is improper. This astigmatism has the same character in local surface and full-aperture surface. The flat stitching interferometer has the ability to measure both the local surface and the full-aperture surface. Therefore, we employ a flat stitching interferometer to inspect local the surface during assembly, by which the astigmatism is controlled. Experiments show that the local surface precision of the flat stitching interferometer arrives at 50 nm (PV) and the space rate reaches 5 mm-1, enabling intermediate frequency detection. On the other hand, the flat stitching interferometer can measure the full-aperture of optics by scanning. The test uncertainty is 100 nm and the difference relative to large aperture interferometer is less than 0.04（=632.8 nm）.
2014,
26: 051015.
doi: 10.11884/HPLPB201426.051015
Abstract:
With the method of exciting surface wave of photonic-photonic, a new compound structure made up of surface modified photonic is designed. Using plane wave expansion method and super cell technology, mode dispersion relations of coupled surface for this structure was studied. Furthermore, numerical simulation of light beam in this structure by finite-difference time-domain (FDTD) method, and analysis of its physical mechanism were carried out. It is found that beam splitting is obtained for incident light of a certain frequency range. This finding can be used to design a beam splitter.
With the method of exciting surface wave of photonic-photonic, a new compound structure made up of surface modified photonic is designed. Using plane wave expansion method and super cell technology, mode dispersion relations of coupled surface for this structure was studied. Furthermore, numerical simulation of light beam in this structure by finite-difference time-domain (FDTD) method, and analysis of its physical mechanism were carried out. It is found that beam splitting is obtained for incident light of a certain frequency range. This finding can be used to design a beam splitter.
2014,
26: 051016.
doi: 10.11884/HPLPB201426.051016
Abstract:
For the measurement of the time profile and the contrast information of the ultrashort laser pulse, based on the third-order intensity correlation principle, using optical pulse replication, a measurement method is proposed. Theoretical analysis is made about the measurement method. The simulation was done with split-step Fourier and Runge-Kutta methods. By measuring the pulse with pieces of windows and piecing the windows together, the measuring range can be enlarged. Thus a high resolution and large window measurement is achieved. The pre-pulse and main pulse are separated into different windows to avoid the use of gradient attenuator, and provides high-contrast measurement capability.
For the measurement of the time profile and the contrast information of the ultrashort laser pulse, based on the third-order intensity correlation principle, using optical pulse replication, a measurement method is proposed. Theoretical analysis is made about the measurement method. The simulation was done with split-step Fourier and Runge-Kutta methods. By measuring the pulse with pieces of windows and piecing the windows together, the measuring range can be enlarged. Thus a high resolution and large window measurement is achieved. The pre-pulse and main pulse are separated into different windows to avoid the use of gradient attenuator, and provides high-contrast measurement capability.
2014,
26: 051017.
doi: 10.11884/HPLPB201426.051017
Abstract:
The distribution of the optical field generated by focusing an astigmatic elliptical Gauss beam using an axicon is studied and the formula of the optical field diffracted by the axicon is derived from Fresnel diffraction integral theory. The intensity of the optical field distribution is calculated by numerical integration. Comparing the field intensity generated by elliptical Gauss beam with the field intensity generated by impinging circular Gauss beam on an axicon, we find that the beam generated by an astigmatic elliptical Gauss beam also has the interesting property of non-diffraction in a certain propagation distance and the similar distribution of on-axis intensity of Bessel-Gauss beam generated by circular Gauss beam, however, the intensity of the optical field perpendicular to optical axis is not cylindrically symmetrical. The maximum non-diffracting lengths of elliptical Bessel-Gauss beam on meridional and sagittal planes are also calculated according to the maximum non-diffractive length formula of spherical wave generating quasi-Bessel beam, and the non-diffracting length of the whole beam is limited by the size of minor axis of incident elliptical spot on the axicon.
The distribution of the optical field generated by focusing an astigmatic elliptical Gauss beam using an axicon is studied and the formula of the optical field diffracted by the axicon is derived from Fresnel diffraction integral theory. The intensity of the optical field distribution is calculated by numerical integration. Comparing the field intensity generated by elliptical Gauss beam with the field intensity generated by impinging circular Gauss beam on an axicon, we find that the beam generated by an astigmatic elliptical Gauss beam also has the interesting property of non-diffraction in a certain propagation distance and the similar distribution of on-axis intensity of Bessel-Gauss beam generated by circular Gauss beam, however, the intensity of the optical field perpendicular to optical axis is not cylindrically symmetrical. The maximum non-diffracting lengths of elliptical Bessel-Gauss beam on meridional and sagittal planes are also calculated according to the maximum non-diffractive length formula of spherical wave generating quasi-Bessel beam, and the non-diffracting length of the whole beam is limited by the size of minor axis of incident elliptical spot on the axicon.
2014,
26: 051018.
doi: 10.11884/HPLPB201426.051018
Abstract:
The principle of distributed fiber Bragg grating (FBG) addressing system based on frequency modulation continuous wave (FMCW) multiplexing technology was studied. The influence of FBG multiplexing distance when it is an integer multiple or a non-integer multiple of the minimum distance that the system is able to distinguish on the signal spectrum was analyzed through the simulation experiment. An FBG multiplexing experimental platform based on FMCW was established, when the sensing distance is 1000 m, we verify that the difference frequency signal keeps a linear relationship with the scanning cycle and the scanning range; when the FBG multiplexing distance is an integer multiple of the minimum distance that the system is able to distinguish, within the measurement range of 1100 m, the maximum error of the system is 243 Hz, the maximum relative error is less than 5%; thus FBG sensor addressing can be achieved.
The principle of distributed fiber Bragg grating (FBG) addressing system based on frequency modulation continuous wave (FMCW) multiplexing technology was studied. The influence of FBG multiplexing distance when it is an integer multiple or a non-integer multiple of the minimum distance that the system is able to distinguish on the signal spectrum was analyzed through the simulation experiment. An FBG multiplexing experimental platform based on FMCW was established, when the sensing distance is 1000 m, we verify that the difference frequency signal keeps a linear relationship with the scanning cycle and the scanning range; when the FBG multiplexing distance is an integer multiple of the minimum distance that the system is able to distinguish, within the measurement range of 1100 m, the maximum error of the system is 243 Hz, the maximum relative error is less than 5%; thus FBG sensor addressing can be achieved.
2014,
26: 051019.
doi: 10.11884/HPLPB201426.051019
Abstract:
Precise control of pulse laser light dose is the key to guarantee processing product technology and quality. After analyzing the existing light dose feedback control algorithm, based on grouping pulse, a new grouping pulse dose monitoring feedback control algorithm was proposed to effectively improve the precision and the speed of light dose monitoring and feedback control. A light dose monitoring system was designed to monitor the light dose and control the feedback in real time. Compared with the StarLab laser energy measurement made by Ophir, in the case of the total energy less than 500 laser pulses, the energy measurement error of the system is less than 0.15%. Light dose monitoring experiment was carried out on a set of pulse laser machining system, the max repetition frequency of which is 10 kHz, the single pulse max energy of which is 5 mJ, the max energy fluctuations of which is 10% in constant voltage. In the monitoring of the system, in the case of the target light dose within 150 mJ/mm2, light dose control accuracy and repeated accuracy can be controlled within 1.90% and 0.100 mJ/mm2 respectively, at the same time, the control speed of the light dose feedback increased 4 times.
Precise control of pulse laser light dose is the key to guarantee processing product technology and quality. After analyzing the existing light dose feedback control algorithm, based on grouping pulse, a new grouping pulse dose monitoring feedback control algorithm was proposed to effectively improve the precision and the speed of light dose monitoring and feedback control. A light dose monitoring system was designed to monitor the light dose and control the feedback in real time. Compared with the StarLab laser energy measurement made by Ophir, in the case of the total energy less than 500 laser pulses, the energy measurement error of the system is less than 0.15%. Light dose monitoring experiment was carried out on a set of pulse laser machining system, the max repetition frequency of which is 10 kHz, the single pulse max energy of which is 5 mJ, the max energy fluctuations of which is 10% in constant voltage. In the monitoring of the system, in the case of the target light dose within 150 mJ/mm2, light dose control accuracy and repeated accuracy can be controlled within 1.90% and 0.100 mJ/mm2 respectively, at the same time, the control speed of the light dose feedback increased 4 times.
2014,
26: 051020.
doi: 10.11884/HPLPB201426.051020
Abstract:
A combination of dual tree complex transform and the image processing algorithm of semi-blind deconvolution was proposed to eliminate the factors which make the image worse. Firstly, the retinal image obtained from the adaptive optics system was decomposed with dual tree complex transform into two parts. The low frequency image was processed by the algorithm of semi-blind deconvolution with some constraints. And the optical transfer function was used as initial parameter estimate which was constructed with the residual aberration of image system. The high frequency image was processed by denoising. Finally, the goal image was obtained by combining the processed images. The experimental results show that the retinal image quality is improved with this method, the image objective quality evaluation parameters are increased more than 5 times compared with the original image, and the average power spectrum is improved about 6 times in the spatial frequency range(70~90()-1) of retinal cells, which show that the method can contribute to satisfying the requirement of observation of human retinal image.
A combination of dual tree complex transform and the image processing algorithm of semi-blind deconvolution was proposed to eliminate the factors which make the image worse. Firstly, the retinal image obtained from the adaptive optics system was decomposed with dual tree complex transform into two parts. The low frequency image was processed by the algorithm of semi-blind deconvolution with some constraints. And the optical transfer function was used as initial parameter estimate which was constructed with the residual aberration of image system. The high frequency image was processed by denoising. Finally, the goal image was obtained by combining the processed images. The experimental results show that the retinal image quality is improved with this method, the image objective quality evaluation parameters are increased more than 5 times compared with the original image, and the average power spectrum is improved about 6 times in the spatial frequency range(70~90()-1) of retinal cells, which show that the method can contribute to satisfying the requirement of observation of human retinal image.
2014,
26: 051021.
doi: 10.11884/HPLPB201426.051021
Abstract:
We simulated the amplification process during the broadband optical parametric amplification, and we proposed an improved design for high conversion-efficiency during broadband optical parametric amplification based on our simulation result. We carried out an experimental research based on our design. After our research on the key technologies, such as spatial shaping, temporal shaping, superfluorescence suppression, bandwidth matching, we increased the conversion efficiency with suppression of the superfluorescence. The conversion efficiency with our one-stage optical parametric amplification could reach 30%.
We simulated the amplification process during the broadband optical parametric amplification, and we proposed an improved design for high conversion-efficiency during broadband optical parametric amplification based on our simulation result. We carried out an experimental research based on our design. After our research on the key technologies, such as spatial shaping, temporal shaping, superfluorescence suppression, bandwidth matching, we increased the conversion efficiency with suppression of the superfluorescence. The conversion efficiency with our one-stage optical parametric amplification could reach 30%.
2014,
26: 051022.
doi: 10.11884/HPLPB201426.051022
Abstract:
In order to improve the performance of the general broad area high power 940 nm InGaAs/GaAs semiconductor laser diode (LD), we design a new type quantum well LD with an asymmetric waveguide and cladding structure. High material quality with low internal loss of 0.44 mm-1 has been achieved using low pressure metal organic chemical vapor deposition (LP-MOCVD) method. Broad-area lasers were fabricated with the wafers grown on GaAs substrates. For the 940 nm devices with 100 m-wide stripe and 2000 m-long cavity under 25 ℃ continuous wave (CW) operation condition of 10 A, the typical threshold current is 251 mA, the slope efficiency is 1.22 W/A , and the maximum output power reaches 9.6 W. The laser diode yielded a maximum power conversion efficiency over 70%.
In order to improve the performance of the general broad area high power 940 nm InGaAs/GaAs semiconductor laser diode (LD), we design a new type quantum well LD with an asymmetric waveguide and cladding structure. High material quality with low internal loss of 0.44 mm-1 has been achieved using low pressure metal organic chemical vapor deposition (LP-MOCVD) method. Broad-area lasers were fabricated with the wafers grown on GaAs substrates. For the 940 nm devices with 100 m-wide stripe and 2000 m-long cavity under 25 ℃ continuous wave (CW) operation condition of 10 A, the typical threshold current is 251 mA, the slope efficiency is 1.22 W/A , and the maximum output power reaches 9.6 W. The laser diode yielded a maximum power conversion efficiency over 70%.
2014,
26: 051023.
doi: 10.11884/HPLPB201426.051023
Abstract:
The inconsistency of multi-channels digital to analog conversion circuit output seriously affects the simulation quality of the infrared detector simulator. In order to solve this problem, a novel method called two-point inconsistency calibration model (TICM) is proposed by introducing a two-point non-uniformity correction algorithm into the inconsistency problem. By analyzing the sample data of the infrared detector simulator, correction factors are obtained, and the TICM is implemented on the core processor FPGA (field-programmable gate array). The images before and after inconsistency correction are obtained by simulating the output signal of 320256 mid-wave infrared cooling detector. The result shows that the maximum fluctuation of the column average gray level is up to 15 initially, but after the inconsistency correction, it decreases to 5. There is about a 66.7% increase in output performance by using TICM. Thus, the established inconsistency calibration model is a good solution to the inconsistency problem of multi-channels digital to analog conversion circuit output and provides a foundation for quantitative simulation of the infrared detector simulator.
The inconsistency of multi-channels digital to analog conversion circuit output seriously affects the simulation quality of the infrared detector simulator. In order to solve this problem, a novel method called two-point inconsistency calibration model (TICM) is proposed by introducing a two-point non-uniformity correction algorithm into the inconsistency problem. By analyzing the sample data of the infrared detector simulator, correction factors are obtained, and the TICM is implemented on the core processor FPGA (field-programmable gate array). The images before and after inconsistency correction are obtained by simulating the output signal of 320256 mid-wave infrared cooling detector. The result shows that the maximum fluctuation of the column average gray level is up to 15 initially, but after the inconsistency correction, it decreases to 5. There is about a 66.7% increase in output performance by using TICM. Thus, the established inconsistency calibration model is a good solution to the inconsistency problem of multi-channels digital to analog conversion circuit output and provides a foundation for quantitative simulation of the infrared detector simulator.
2014,
26: 052001.
doi: 10.11884/HPLPB201426.052001
Abstract:
Imaging velocity interferometer system for any reflector (VISAR) is a typical facility for diagnosing shock wave velocity in ICF experiments. Due to the using of lighting laser in the system, the obtained velocity streak images are affected by laser speckle, and the velocity analysis is influenced for this reason. The formation reason of the laser speckle in the system and the effect in velocity analysis are introduced in the paper. A low pass filter located at the Fourier frequency plane of the imaging system is used to filter the high frequency speckle noise. An optical path of the interferometer used in the VISAR is put forward and the real path is simulated. The results shown in the paper indicate that the filter used in the system obviously suppresses the speckle noise in the imaging VISAR.
Imaging velocity interferometer system for any reflector (VISAR) is a typical facility for diagnosing shock wave velocity in ICF experiments. Due to the using of lighting laser in the system, the obtained velocity streak images are affected by laser speckle, and the velocity analysis is influenced for this reason. The formation reason of the laser speckle in the system and the effect in velocity analysis are introduced in the paper. A low pass filter located at the Fourier frequency plane of the imaging system is used to filter the high frequency speckle noise. An optical path of the interferometer used in the VISAR is put forward and the real path is simulated. The results shown in the paper indicate that the filter used in the system obviously suppresses the speckle noise in the imaging VISAR.
2014,
26: 052002.
doi: 10.11884/HPLPB201426.052002
Abstract:
A type of mixed KB-KBA microscope for dynamic imaging diagnostics at multi-keV was proposed to obtain large field, high spatial resolution, high light efficiency and spectral resolution. It consists of two spherical mirrors with single-layer in tangential direction to obtain high spatial resolution and a spherical mirror with periodic multilayer in sagittal direction to ensure high light efficiency and spectral resolution. The problems of low effective solid angle, uneven brightness and limited effective object field existing in traditional single-layer and periodic multilayer KBA microscope for dynamic imaging diagnostics at multi-keV were solved. The optical design of mixed KB-KBA microscope at 2.5 keV and 4.3 keV was carried out by the ray-tracing model under the consideration of thin-films reflectance, and the spatial resolution better than 5 m within 1.4 mm object field in tangential direction and effective solid angle larger than 210-7 sr were achieved.
A type of mixed KB-KBA microscope for dynamic imaging diagnostics at multi-keV was proposed to obtain large field, high spatial resolution, high light efficiency and spectral resolution. It consists of two spherical mirrors with single-layer in tangential direction to obtain high spatial resolution and a spherical mirror with periodic multilayer in sagittal direction to ensure high light efficiency and spectral resolution. The problems of low effective solid angle, uneven brightness and limited effective object field existing in traditional single-layer and periodic multilayer KBA microscope for dynamic imaging diagnostics at multi-keV were solved. The optical design of mixed KB-KBA microscope at 2.5 keV and 4.3 keV was carried out by the ray-tracing model under the consideration of thin-films reflectance, and the spatial resolution better than 5 m within 1.4 mm object field in tangential direction and effective solid angle larger than 210-7 sr were achieved.
2014,
26: 052003.
doi: 10.11884/HPLPB201426.052003
Abstract:
A kind of broadband thin film polarizer with large angle tolerance has been designed and fabricated. This polarizer has high extinction ratio in the incidence angle range of 53-60 and wavelength region of 1044-1088 nm. The coating design is H/L type multilayer, and employs HfO2 and SiO2 as the high and low refractive index materials. The electronic beam evaporation method is employed to evaporate the metal hafnium and SiO2 without ion beam assistance. Laser damage characteristic is investigated. The results show that the laser induced damage threshold (LIDT) of the P polarization is 20 J/cm2, and the relevant damage morphology indicates that the damage is initiated from nanosize absorbers located at the coating and substrate interface or shallow subsurface; the LIDT of the S polarization is 45 J/cm2, and the damage is initiated from nodules or contamination particles.
A kind of broadband thin film polarizer with large angle tolerance has been designed and fabricated. This polarizer has high extinction ratio in the incidence angle range of 53-60 and wavelength region of 1044-1088 nm. The coating design is H/L type multilayer, and employs HfO2 and SiO2 as the high and low refractive index materials. The electronic beam evaporation method is employed to evaporate the metal hafnium and SiO2 without ion beam assistance. Laser damage characteristic is investigated. The results show that the laser induced damage threshold (LIDT) of the P polarization is 20 J/cm2, and the relevant damage morphology indicates that the damage is initiated from nanosize absorbers located at the coating and substrate interface or shallow subsurface; the LIDT of the S polarization is 45 J/cm2, and the damage is initiated from nodules or contamination particles.
2014,
26: 052004.
doi: 10.11884/HPLPB201426.052004
Abstract:
A new ray-based model of crossing-beam energy transfer (CBET) is developed. This model can be used in dynamic kinetic codes for evaluating CBET in line. By defining laser intensity in grid through inverse bremsstrahlung absorption formula of laser, every single ray of probe laser beam can obtain (or lose) energy from the intensity of pump laser beam. Since CBET is dependent on the history of every single laser ray and the coupling between probe laser and pump laser is strong, the coupling equations are difficult to be solved. Calculating iteratively can solve the problem well. This in-line CBET model can be generalized to the situation where there are energy transfers among three or more laser beams easily. Inverse bremsstrahlung absorption and laser plasma interaction could also be involved in the model.
A new ray-based model of crossing-beam energy transfer (CBET) is developed. This model can be used in dynamic kinetic codes for evaluating CBET in line. By defining laser intensity in grid through inverse bremsstrahlung absorption formula of laser, every single ray of probe laser beam can obtain (or lose) energy from the intensity of pump laser beam. Since CBET is dependent on the history of every single laser ray and the coupling between probe laser and pump laser is strong, the coupling equations are difficult to be solved. Calculating iteratively can solve the problem well. This in-line CBET model can be generalized to the situation where there are energy transfers among three or more laser beams easily. Inverse bremsstrahlung absorption and laser plasma interaction could also be involved in the model.
2014,
26: 052005.
doi: 10.11884/HPLPB201426.052005
Abstract:
A surface profile measurement visualization method of large aspheric lenses based on doubly-connected edge list (DCEL) are proposed, and a software system is designed and developed to realize it. Firstly, an improved data structure based on DCEL is proposed to load 3D model. The graphics units which compose the basic part of the software are modeled based on DCEL data structure. Secondly, the scene node which composes the display part of software is created by aspheric surface profile according to surface equation. And the measurement path is generated and displayed by the software. An experiment was performed on the noncontact measurement platform. The data were integrated and smoothed to compare with the equation of aspheric surface contour and then the peak-valley value and RMS value of the surface were calculated. The experiment indicates that the surface profile measurement visualization method is correct and stable.
A surface profile measurement visualization method of large aspheric lenses based on doubly-connected edge list (DCEL) are proposed, and a software system is designed and developed to realize it. Firstly, an improved data structure based on DCEL is proposed to load 3D model. The graphics units which compose the basic part of the software are modeled based on DCEL data structure. Secondly, the scene node which composes the display part of software is created by aspheric surface profile according to surface equation. And the measurement path is generated and displayed by the software. An experiment was performed on the noncontact measurement platform. The data were integrated and smoothed to compare with the equation of aspheric surface contour and then the peak-valley value and RMS value of the surface were calculated. The experiment indicates that the surface profile measurement visualization method is correct and stable.
2014,
26: 052006.
doi: 10.11884/HPLPB201426.052006
Abstract:
The spectra of Ni plasma induced by femtosecond laser pulses at sub-atmospheric pressure environment have been studied experimentally in air and argon gas, respectively. The results show that the spectra of laser-induced plasmas are composed of continuous spectra and atomic line spectra in these two surrounding gases. The spectra at lower surrounding pressure show higher resolution due to the decrease of electron density, compared to that at higher pressure. Besides, the intensity of line spectra undergoes the transition from slow increase to rapid decrease. Additionally, the effect of the composition of the surrounding gas on the intensity is also briefly discussed.
The spectra of Ni plasma induced by femtosecond laser pulses at sub-atmospheric pressure environment have been studied experimentally in air and argon gas, respectively. The results show that the spectra of laser-induced plasmas are composed of continuous spectra and atomic line spectra in these two surrounding gases. The spectra at lower surrounding pressure show higher resolution due to the decrease of electron density, compared to that at higher pressure. Besides, the intensity of line spectra undergoes the transition from slow increase to rapid decrease. Additionally, the effect of the composition of the surrounding gas on the intensity is also briefly discussed.
Ultrafast time resolution 2D imaging technology based on photoelectron pulse quasi-linearly dilation
2014,
26: 052007.
doi: 10.11884/HPLPB201426.052007
Abstract:
In order to record the ultrafast light pulse signal, a technology based on photoelectron pulse quasi-linearly dilation was presented. The photoelectron pulse went in the acceleration region on the calculated time to be accelerated by a high frequency varying electrical field, and then came into the uniform speed drift region to be quasi-linearly dilated. Using the gated Micro-channel Plate (MCP) detector whose time resolution was 100 ps on the recording surface to accept the electron pulse，the time resolved 2D imaging could be achieved. The system spatial resolution and image distortion were improved by an axial focusing magnetic field. For an electron beam whose energy was 4 keV and emit angle was 0.1, the optimal intensity of the focusing magnetic field was 0.057 T which could lead a 5 lp/mm resolution at the center of the photocathode while lower at the edge. Based on this technology, when the drift distance was 50 cm, the dilation magnification came to be 10, thus the temporal resolution of the 2D imaging system could be reduced to 10 ps.
In order to record the ultrafast light pulse signal, a technology based on photoelectron pulse quasi-linearly dilation was presented. The photoelectron pulse went in the acceleration region on the calculated time to be accelerated by a high frequency varying electrical field, and then came into the uniform speed drift region to be quasi-linearly dilated. Using the gated Micro-channel Plate (MCP) detector whose time resolution was 100 ps on the recording surface to accept the electron pulse，the time resolved 2D imaging could be achieved. The system spatial resolution and image distortion were improved by an axial focusing magnetic field. For an electron beam whose energy was 4 keV and emit angle was 0.1, the optimal intensity of the focusing magnetic field was 0.057 T which could lead a 5 lp/mm resolution at the center of the photocathode while lower at the edge. Based on this technology, when the drift distance was 50 cm, the dilation magnification came to be 10, thus the temporal resolution of the 2D imaging system could be reduced to 10 ps.
2014,
26: 052008.
doi: 10.11884/HPLPB201426.052008
Abstract:
The beryllium-copper capsule is one of the candidate ignition capsules in National Ignition Facility Project. Precision match and bonding is the crucial process in the preparation for this capsule. In this paper, the technique is researched for the Cu materials as a substitute for Be, and the optimum parameters are achieved(temperature under 600 ℃, pressure less than 6 MPa, processing period more than 60 minutes). Finally, the Cu capsule is matched, with a surface roughness less than 50 nm and an asymmetry of diameters less than 20 m. Using scanning electron microscope, cracks and flows have not be detected in the section of the joint. The strength of bonding meet the requirements of the following machining.
The beryllium-copper capsule is one of the candidate ignition capsules in National Ignition Facility Project. Precision match and bonding is the crucial process in the preparation for this capsule. In this paper, the technique is researched for the Cu materials as a substitute for Be, and the optimum parameters are achieved(temperature under 600 ℃, pressure less than 6 MPa, processing period more than 60 minutes). Finally, the Cu capsule is matched, with a surface roughness less than 50 nm and an asymmetry of diameters less than 20 m. Using scanning electron microscope, cracks and flows have not be detected in the section of the joint. The strength of bonding meet the requirements of the following machining.
2014,
26: 052009.
doi: 10.11884/HPLPB201426.052009
Abstract:
The emulsion droplets generation process in co-flowing microfluidic channels was studied by using a volume-of-fluid (VOF) numerical way. The diameter of emulsion droplets was controlled by the parameters including velocity ratio, surface tension and viscosity. Simulation results demonstrated that the diameter could be tuned by logarithm of velocity ratio in linear ways. The diameter increases with the increase of surface tension but becomes steady when surface tension is above 0.03 N/m. And the viscosity of disperse phase has negligible impact on droplet diameter. Furthermore, divinyl benzene (DVB) emulsion droplets with a diameter of 0.5 mm to 3.0 mm were produced in a self-made polydimethylsiloxane (PDMS) microfluidic slab where polyvinyl alcohol (PVA), DVB solution were set as the continuous phase and disperse phase respectively.
The emulsion droplets generation process in co-flowing microfluidic channels was studied by using a volume-of-fluid (VOF) numerical way. The diameter of emulsion droplets was controlled by the parameters including velocity ratio, surface tension and viscosity. Simulation results demonstrated that the diameter could be tuned by logarithm of velocity ratio in linear ways. The diameter increases with the increase of surface tension but becomes steady when surface tension is above 0.03 N/m. And the viscosity of disperse phase has negligible impact on droplet diameter. Furthermore, divinyl benzene (DVB) emulsion droplets with a diameter of 0.5 mm to 3.0 mm were produced in a self-made polydimethylsiloxane (PDMS) microfluidic slab where polyvinyl alcohol (PVA), DVB solution were set as the continuous phase and disperse phase respectively.
2014,
26: 052010.
doi: 10.11884/HPLPB201426.052010
Abstract:
Molecular dynamics (MD) and grand canonical Monte Carlo (GCMC) method were used to study the diffusion and the solubility coefficients of H2, D2, T2 in brominated butyl rubber (BIIR). Using the free volume theory, the mechanism of the diffusion of small molecules in brominated butyl rubber was discussed, and the trajectory of gas motion was obtained. It was shown that in terms of hydrogen and hydrogen isotopes, the smaller the mass was and the faster the kinematic velocity was, the higher the diffusion coefficient was. The solubility coefficients of H2, D2, T2 were close. Moreover, the permeability coefficients obtained by the simulation were in good agreement with the experimental data. They provided some theoretical basis for improving the barrier properties of materials, simultaneously the fact that tritium also had good barrier properties to vulcanized brominated butyl rubber was forcasted.
Molecular dynamics (MD) and grand canonical Monte Carlo (GCMC) method were used to study the diffusion and the solubility coefficients of H2, D2, T2 in brominated butyl rubber (BIIR). Using the free volume theory, the mechanism of the diffusion of small molecules in brominated butyl rubber was discussed, and the trajectory of gas motion was obtained. It was shown that in terms of hydrogen and hydrogen isotopes, the smaller the mass was and the faster the kinematic velocity was, the higher the diffusion coefficient was. The solubility coefficients of H2, D2, T2 were close. Moreover, the permeability coefficients obtained by the simulation were in good agreement with the experimental data. They provided some theoretical basis for improving the barrier properties of materials, simultaneously the fact that tritium also had good barrier properties to vulcanized brominated butyl rubber was forcasted.
2014,
26: 052011.
doi: 10.11884/HPLPB201426.052011
Abstract:
SiC ceramic materials are well-known for its excellent thermo-mechanical properties, and its advantages compared with hollow glass microspheres make it one of the candidates for ICF target application. SiC ceramic microspheres were fabricated by drop-tower technique by using polycarbosilane (PCS) as raw material. The reaction mechanism of precursor pyrolysis and the effects of irradiation and carbonization on the SiC hollow microspheres were investigated. The results show that the ceramic yield at 850 ℃ is 65%, and the temperature at which the PCS begins to decompose is from 400 ℃ to 800 ℃. Bridge structure of SiCSi or SiOSi was formed in the irradiated products, and in the process of pyrolysis, SiH bonds, CH bonds and SiCH3 groups were partly broken down, the structure of SiCSi was formed. In addition, the influence of irradiation is to maintain the spheres frame during carbonization at high temperature and to increase the surface finish quality and evenness of hollow SiC ceramic microspheres.
SiC ceramic materials are well-known for its excellent thermo-mechanical properties, and its advantages compared with hollow glass microspheres make it one of the candidates for ICF target application. SiC ceramic microspheres were fabricated by drop-tower technique by using polycarbosilane (PCS) as raw material. The reaction mechanism of precursor pyrolysis and the effects of irradiation and carbonization on the SiC hollow microspheres were investigated. The results show that the ceramic yield at 850 ℃ is 65%, and the temperature at which the PCS begins to decompose is from 400 ℃ to 800 ℃. Bridge structure of SiCSi or SiOSi was formed in the irradiated products, and in the process of pyrolysis, SiH bonds, CH bonds and SiCH3 groups were partly broken down, the structure of SiCSi was formed. In addition, the influence of irradiation is to maintain the spheres frame during carbonization at high temperature and to increase the surface finish quality and evenness of hollow SiC ceramic microspheres.
2014,
26: 052012.
doi: 10.11884/HPLPB201426.052012
Abstract:
In this paper, the factors of dynamic stability of the removal function were analyzed. In order to improve the precision of magnetorheological finishing (MRF), an automatic positioning system of aspherical optics was designed. A new approach was used for evaluating dynamic characteristics of removal function. At the same time, a verification experiment was carried out on 400 mm400 mm square aspheric, the PV of the surface precision was 0.331 and the GRMS value was 0.008 /cm. The ability of aspherical optics of the magneto-rheological processing was verified.
In this paper, the factors of dynamic stability of the removal function were analyzed. In order to improve the precision of magnetorheological finishing (MRF), an automatic positioning system of aspherical optics was designed. A new approach was used for evaluating dynamic characteristics of removal function. At the same time, a verification experiment was carried out on 400 mm400 mm square aspheric, the PV of the surface precision was 0.331 and the GRMS value was 0.008 /cm. The ability of aspherical optics of the magneto-rheological processing was verified.
2014,
26: 053001.
doi: 10.11884/HPLPB201426.053001
Abstract:
Frequency locking and phase locking is the key issue for the research of high power microwave combination. An initial phase inducing method for high power microwave oscillator is put forward and investigated. The phase locking can be achieved in the condition of a wider frequency detuning and a lower power input by using this new approach. The phase of GW level high power microwave is controlled with jitter less than 15 by a weak signal with an injection power ration less than -40 dB and a pulse width of about 10 ns. The method can be extended to other types of high power oscillator such as relativistic magnetron, transition-time oscillator, Cherenkov radiation oscillator and so on.
Frequency locking and phase locking is the key issue for the research of high power microwave combination. An initial phase inducing method for high power microwave oscillator is put forward and investigated. The phase locking can be achieved in the condition of a wider frequency detuning and a lower power input by using this new approach. The phase of GW level high power microwave is controlled with jitter less than 15 by a weak signal with an injection power ration less than -40 dB and a pulse width of about 10 ns. The method can be extended to other types of high power oscillator such as relativistic magnetron, transition-time oscillator, Cherenkov radiation oscillator and so on.
2014,
26: 053002.
doi: 10.11884/HPLPB201426.053002
Abstract:
The resonant conductance of the slot is variable with the changing of the broad wall dimension of the waveguide. In this paper, the variable rule of the resonant conductance of the slot in a wide side dimension adjustable slot-waveguide is studied, as well as the influence of the slot width, the cutting depth, and the duct thickness. Fitting equations are obtained by suitable theoretical model, and they can satisfy the requirement of engineering design. Besides, electric field radiation of waveguide slots varying with the dimension adjusting of the wide side wall is analyzed.
The resonant conductance of the slot is variable with the changing of the broad wall dimension of the waveguide. In this paper, the variable rule of the resonant conductance of the slot in a wide side dimension adjustable slot-waveguide is studied, as well as the influence of the slot width, the cutting depth, and the duct thickness. Fitting equations are obtained by suitable theoretical model, and they can satisfy the requirement of engineering design. Besides, electric field radiation of waveguide slots varying with the dimension adjusting of the wide side wall is analyzed.
2014,
26: 053003.
doi: 10.11884/HPLPB201426.053003
Abstract:
Based on photonic technique, an approach to the symbol rate estimation of the remote distributed microwave signal reception is proposed and demonstrated experimentally. Firstly, the received microwave signal is applied to modulating the light wave under the carrier-suppressed double sideband (CS-DSB) modulation in the remote terminal, generating two optical sideband signals carrying the microwave signal. Then the two sidebands are transmitted to the central station through optical fiber links, and one of them is filtered out in the optical domain. After the photoelectric detection (PD), the microwave signal symbol rate can be obtained by analyzing the spectrum of the electrical signals. The proposed approach is verified via both simulations and experiments. In the simulations, the symbol rate of 0.8 GBaud or 6 GBaud is successfully extracted for pseudo-random binary signal (PRBS) with the carrier frequency at 60 GHz. At the same time, the symbol rate of 3 GBaud is extracted for PRBS signals with 25 GHz carrier frequency. In the experiments, the symbol rate at 3 GBaud or 5 GBaud is achieved when the carrier frequency is 25 GHz. The proposed approach has the advantages such as wide instantaneous bandwidth, low loss for remote transmission, availability for distributed monitoring, and strong immunity to electromagnetic interference, which would play an important role for the microwave signal analysis and estimation.
Based on photonic technique, an approach to the symbol rate estimation of the remote distributed microwave signal reception is proposed and demonstrated experimentally. Firstly, the received microwave signal is applied to modulating the light wave under the carrier-suppressed double sideband (CS-DSB) modulation in the remote terminal, generating two optical sideband signals carrying the microwave signal. Then the two sidebands are transmitted to the central station through optical fiber links, and one of them is filtered out in the optical domain. After the photoelectric detection (PD), the microwave signal symbol rate can be obtained by analyzing the spectrum of the electrical signals. The proposed approach is verified via both simulations and experiments. In the simulations, the symbol rate of 0.8 GBaud or 6 GBaud is successfully extracted for pseudo-random binary signal (PRBS) with the carrier frequency at 60 GHz. At the same time, the symbol rate of 3 GBaud is extracted for PRBS signals with 25 GHz carrier frequency. In the experiments, the symbol rate at 3 GBaud or 5 GBaud is achieved when the carrier frequency is 25 GHz. The proposed approach has the advantages such as wide instantaneous bandwidth, low loss for remote transmission, availability for distributed monitoring, and strong immunity to electromagnetic interference, which would play an important role for the microwave signal analysis and estimation.
2014,
26: 053101.
doi: 10.11884/HPLPB201426.053101
Abstract:
The Finite Conductivity Wall module is verified and validated in terahertz folded waveguide traveling wave tube simulation compared with commercial software including attenuation result of cold test and gain result of hot test. The calculated results agree with each other well. Max relative error of attenuation in cold test is about 3%~4%, and max relative error of gain in hot test is about 2% with the optimal working voltage drifting relative error about 2%. In addition, the influence of geometric structural parameters on the attenuation result of cold test is also analyzed and discussed in detail.
The Finite Conductivity Wall module is verified and validated in terahertz folded waveguide traveling wave tube simulation compared with commercial software including attenuation result of cold test and gain result of hot test. The calculated results agree with each other well. Max relative error of attenuation in cold test is about 3%~4%, and max relative error of gain in hot test is about 2% with the optimal working voltage drifting relative error about 2%. In addition, the influence of geometric structural parameters on the attenuation result of cold test is also analyzed and discussed in detail.
2014,
26: 053102.
doi: 10.11884/HPLPB201426.053102
Abstract:
As a key part of terahertz vacuum electronic device, metal grating cant be fabricated using traditional methods due to its tiny dimension. The photoetching process of metal bi-grating for radiation source at some terahertz band was presented. The influence of the procedure (including substrate preparation, spin-coating, pre-bake, exposure, post-bake and developing) on photoetching was analyzed experimentally. The problems such as film drop and crack, films combination and the photoresist remaining at gaps which were caused by thick film and high aspect ratio, were solved by the optimizing the process parameters. Finally, a good film microstructure with steep side wall and smooth surface was achieved, with a thickness of 700 m and an aspect ratio of 14. The work presented in this paper provides a technological guide to the similarly related project.
As a key part of terahertz vacuum electronic device, metal grating cant be fabricated using traditional methods due to its tiny dimension. The photoetching process of metal bi-grating for radiation source at some terahertz band was presented. The influence of the procedure (including substrate preparation, spin-coating, pre-bake, exposure, post-bake and developing) on photoetching was analyzed experimentally. The problems such as film drop and crack, films combination and the photoresist remaining at gaps which were caused by thick film and high aspect ratio, were solved by the optimizing the process parameters. Finally, a good film microstructure with steep side wall and smooth surface was achieved, with a thickness of 700 m and an aspect ratio of 14. The work presented in this paper provides a technological guide to the similarly related project.
2014,
26: 053201.
doi: 10.11884/HPLPB201426.053201
Abstract:
The Helmholtz coil is widely used in the device for dozens of Tesla quasi static pulsed magnetic field generation. Based on the quasi-static pulse magnetic field generator for magnetically applied pressure-shear experiments, the thermal and stress of the Helmholtz coil are researched by means of the finite element software ANSYS. The calculated results show that the maximum stress is about 0.5 GPa in the coil pair and 0.2 GPa in the copper wires, and that the displacement of the coil wire is less than 0.05 mm and that the temperature increase in the coil pair is about 150 ℃ when a discharge current flows through the magnet coil pair with a peak current of 14.37 kA and a rising time of 1.34 ms, which can produce 10.7 T magnetic field in the center of the coil pair. These calculated results provide a basis for the optimization design and reinforcement of the coil structure, the copper wire with a tensile strength of 0.5 GPa and insulating layer which can withstand temperature more than 200 ℃ is chosen as the coil wire, and that the zylon fiber with a tensile strength of 5.8 GPa is chosen as the reinforcement around the copper wire, and the corresponding Helmholtz coil structure is designed. This coil pair is used for discharging test and the results show that the coil pair is strong and reliable, and it can be repeatedly used in case of meeting design parameters.
The Helmholtz coil is widely used in the device for dozens of Tesla quasi static pulsed magnetic field generation. Based on the quasi-static pulse magnetic field generator for magnetically applied pressure-shear experiments, the thermal and stress of the Helmholtz coil are researched by means of the finite element software ANSYS. The calculated results show that the maximum stress is about 0.5 GPa in the coil pair and 0.2 GPa in the copper wires, and that the displacement of the coil wire is less than 0.05 mm and that the temperature increase in the coil pair is about 150 ℃ when a discharge current flows through the magnet coil pair with a peak current of 14.37 kA and a rising time of 1.34 ms, which can produce 10.7 T magnetic field in the center of the coil pair. These calculated results provide a basis for the optimization design and reinforcement of the coil structure, the copper wire with a tensile strength of 0.5 GPa and insulating layer which can withstand temperature more than 200 ℃ is chosen as the coil wire, and that the zylon fiber with a tensile strength of 5.8 GPa is chosen as the reinforcement around the copper wire, and the corresponding Helmholtz coil structure is designed. This coil pair is used for discharging test and the results show that the coil pair is strong and reliable, and it can be repeatedly used in case of meeting design parameters.
2014,
26: 053202.
doi: 10.11884/HPLPB201426.053202
Abstract:
The multi-non-uniform grid model of parabolic equation method is presented to solve the radio wave propagation problems with multiple sources in three-dimensional space. Multiple simulation spaces are constructed with different non-uniform grid for each source in corresponding coordinate system. In addition, a parallel technique is employed into multi-non-uniform grid model for the parallel computing of multiple sources problems in three-dimensional space. The radio wave propagation problem with four sources is simulated. The results show that the electromagnetic distribution characteristics of multi-source can be accurately solved via this multi-non-uniform grid model, and in this case, the parallel technique makes the calculation speed of parabolic equation 2.41 times faster, which greatly improves the solution efficiency of 3D multi-source problems.
The multi-non-uniform grid model of parabolic equation method is presented to solve the radio wave propagation problems with multiple sources in three-dimensional space. Multiple simulation spaces are constructed with different non-uniform grid for each source in corresponding coordinate system. In addition, a parallel technique is employed into multi-non-uniform grid model for the parallel computing of multiple sources problems in three-dimensional space. The radio wave propagation problem with four sources is simulated. The results show that the electromagnetic distribution characteristics of multi-source can be accurately solved via this multi-non-uniform grid model, and in this case, the parallel technique makes the calculation speed of parabolic equation 2.41 times faster, which greatly improves the solution efficiency of 3D multi-source problems.
2014,
26: 053203.
doi: 10.11884/HPLPB201426.053203
Abstract:
The burnout effect of RS flip-flops under the injection of HEMP is studied by using our two-dimensional mixed-mode circuit and semiconductor device simulator. The simulation results show that the burnout region is in the channel between gate and drain terminals in the n-channel enhancement mode MOSFETs of the RS flip-flop. The results also show that the power threshold for burnout decreases when the pulse width increases. The difference of the thresholds is not significant when the pulse width is larger than 80 ns. A theoretical model based on the simulation results and the heat equation to assess the relationship between pulse width and burnout threshold of RS flip-flops is proposed and the validity of the model is verified by the simulation results.
The burnout effect of RS flip-flops under the injection of HEMP is studied by using our two-dimensional mixed-mode circuit and semiconductor device simulator. The simulation results show that the burnout region is in the channel between gate and drain terminals in the n-channel enhancement mode MOSFETs of the RS flip-flop. The results also show that the power threshold for burnout decreases when the pulse width increases. The difference of the thresholds is not significant when the pulse width is larger than 80 ns. A theoretical model based on the simulation results and the heat equation to assess the relationship between pulse width and burnout threshold of RS flip-flops is proposed and the validity of the model is verified by the simulation results.
2014,
26: 054001.
doi: 10.11884/HPLPB201426.054001
Abstract:
In order to unfold the measured recoil electron spectrum generated by gamma ray in a deuterated liquid scintillator, standard gamma sources were used to measure the -ray response of BC537 detector and the -ray response function for the BC537 detector was calculated by Geant4 codes which was based on the Monte-Carlo method. The effects of the aluminum container and the beam radius on the detection efficiency were investigated as a function of the beam energy by Geant4 simulation. The simulated response function shows a good agreement with the experimental data at different energies. With the response function and the recoil electron spectrum of three reference -ray sources, an iterative unfolding algorithm was used to unfold the -ray spectrum, and the results further verify the practicability of the simulated response function.
In order to unfold the measured recoil electron spectrum generated by gamma ray in a deuterated liquid scintillator, standard gamma sources were used to measure the -ray response of BC537 detector and the -ray response function for the BC537 detector was calculated by Geant4 codes which was based on the Monte-Carlo method. The effects of the aluminum container and the beam radius on the detection efficiency were investigated as a function of the beam energy by Geant4 simulation. The simulated response function shows a good agreement with the experimental data at different energies. With the response function and the recoil electron spectrum of three reference -ray sources, an iterative unfolding algorithm was used to unfold the -ray spectrum, and the results further verify the practicability of the simulated response function.
2014,
26: 054002.
doi: 10.11884/HPLPB201426.054002
Abstract:
In order to fabricate high reflective multilayer mirrors for 6.7 nm wavelength near B absorption edge, a series of Mo, B4C, Mo2C thin films and Mo/B4C, Mo2C/B4C multilayers were deposited using direct current (DC) magnetron sputtering technology. The thickness for all of the thin films is 30 nm, and the bi-layer number for both multilayer is 30. The period thickness is 3.5 nm, which were measured by grazing incidence-X-ray reflection(GIXR). Surface profiles before and after deposition were measured with a stylus profiler and the stresses were calculated by Stoney formula. The results indicate that all of the thin films show compressive stress, in which the B4C layer shows the biggest stress, and the compression stress of Mo2C layer is larger than that of the Mo layer. Both of the multilayer films show the compressive stress. Mo2C/B4C periodic multilayers have a smaller stress than Mo/B4C multilayers with a sharp interface and are a good material combination for extreme ultraviolet multilayer optics with a large number of bilayers.
In order to fabricate high reflective multilayer mirrors for 6.7 nm wavelength near B absorption edge, a series of Mo, B4C, Mo2C thin films and Mo/B4C, Mo2C/B4C multilayers were deposited using direct current (DC) magnetron sputtering technology. The thickness for all of the thin films is 30 nm, and the bi-layer number for both multilayer is 30. The period thickness is 3.5 nm, which were measured by grazing incidence-X-ray reflection(GIXR). Surface profiles before and after deposition were measured with a stylus profiler and the stresses were calculated by Stoney formula. The results indicate that all of the thin films show compressive stress, in which the B4C layer shows the biggest stress, and the compression stress of Mo2C layer is larger than that of the Mo layer. Both of the multilayer films show the compressive stress. Mo2C/B4C periodic multilayers have a smaller stress than Mo/B4C multilayers with a sharp interface and are a good material combination for extreme ultraviolet multilayer optics with a large number of bilayers.
2014,
26: 054004.
doi: 10.11884/HPLPB201426.054004
Abstract:
In order to explore the mechanism of micro-hollow cathode discharge, the temporal and spatial characteristics of rectangular micro-hollow cathode discharge at 1.3 104 Pa are investigated using a two-dimensional fluid model. The current, electric potential, electric field, charged particle density and mean electron energy are calculated temporally. The results show that the whole discharge consists of four stages, the pre-discharge stage, the transition stage from axial electric field to radial electric field, the transition stage to the hollow cathode effect and the stable discharge stage. Hollow cathode effect exists at the stable stage. Strong electric field and high mean electron energy exist in the cathode fall while high density and quasi-neutral plasma in the negative glow. The peak value of electron density can achieve 1014 cm-3, and the electron temperature levels range from several eV to tens of eV.
In order to explore the mechanism of micro-hollow cathode discharge, the temporal and spatial characteristics of rectangular micro-hollow cathode discharge at 1.3 104 Pa are investigated using a two-dimensional fluid model. The current, electric potential, electric field, charged particle density and mean electron energy are calculated temporally. The results show that the whole discharge consists of four stages, the pre-discharge stage, the transition stage from axial electric field to radial electric field, the transition stage to the hollow cathode effect and the stable discharge stage. Hollow cathode effect exists at the stable stage. Strong electric field and high mean electron energy exist in the cathode fall while high density and quasi-neutral plasma in the negative glow. The peak value of electron density can achieve 1014 cm-3, and the electron temperature levels range from several eV to tens of eV.
2014,
26: 055001.
doi: 10.11884/HPLPB201426.055001
Abstract:
A high power long pulse folded coaxial spiral transmission line pulse modulator was researched. The pulse modulator combined the spiral and folded transmission line methods together to generate long pulse, which made it more compact in structure. The voltage at the load was theoretical analyzed using the method of solving telegraph equation and the voltage at the load was calculated using the PSpice software under different condition. Finally, experiments were carried out. At the gas breakdown voltage of 720 kV, a quasi-square pulse with a voltage of 360 kV, a current of 24 kA and a pulse width of 264 ns was obtained at the load.
A high power long pulse folded coaxial spiral transmission line pulse modulator was researched. The pulse modulator combined the spiral and folded transmission line methods together to generate long pulse, which made it more compact in structure. The voltage at the load was theoretical analyzed using the method of solving telegraph equation and the voltage at the load was calculated using the PSpice software under different condition. Finally, experiments were carried out. At the gas breakdown voltage of 720 kV, a quasi-square pulse with a voltage of 360 kV, a current of 24 kA and a pulse width of 264 ns was obtained at the load.
2014,
26: 055002.
doi: 10.11884/HPLPB201426.055002
Abstract:
Based on circuit theory, an electrical mathematical model of multi-level induction coil gun is established. The influencing factor of armature force is analyzed. The results indicate that the armature force is determined by the drive coil and the armature current and the mutual inductance gradient. Principle of designing multi-level induction coil gun is presented. According to the principle, the optimum launch control strategy of induction coil gun is presented, and is approved practicable by theory. At last, taking ten level induction coilgun as an example, trigger formula of multi-level induction coilgun is presented, and experiments are done to verify the calculation method. Amending the trigger formula, the simulation results agree well with the experimental results.
Based on circuit theory, an electrical mathematical model of multi-level induction coil gun is established. The influencing factor of armature force is analyzed. The results indicate that the armature force is determined by the drive coil and the armature current and the mutual inductance gradient. Principle of designing multi-level induction coil gun is presented. According to the principle, the optimum launch control strategy of induction coil gun is presented, and is approved practicable by theory. At last, taking ten level induction coilgun as an example, trigger formula of multi-level induction coilgun is presented, and experiments are done to verify the calculation method. Amending the trigger formula, the simulation results agree well with the experimental results.
2014,
26: 055003.
doi: 10.11884/HPLPB201426.055003
Abstract:
Planar wire arrays Z pinches were conducted on Qiangguang generator (1.5 MA, 100 ns). The loads in the experiments varied their row widths (6-24 mm) and wire numbers (10-34). The scaling of the implosion times, radiation yields and power with the parameter of the loads, such as array masses, inter-wire gaps, and array widths were investigated. The images of the soft X-ray camera show that the trailing mass, precursor column, and R-T instability exist during the implosion phase, and kink instability will occur and rapidly develop after stagnation. The experimental results show that the product of the line mass and the square row width is a critical factor. This factor can affect the implosion times and the X-ray products of wire arrays with different parameters, the optimum range is 200~400 gcm for Qiangguang generator. The results also imply that the inter-wire gap should be smaller than 1 mm. The maximum X-ray total energy is 22 kJ with the peak power 630 GW while the maximum K-shell product is 3.9 kJ with 158 GW.
Planar wire arrays Z pinches were conducted on Qiangguang generator (1.5 MA, 100 ns). The loads in the experiments varied their row widths (6-24 mm) and wire numbers (10-34). The scaling of the implosion times, radiation yields and power with the parameter of the loads, such as array masses, inter-wire gaps, and array widths were investigated. The images of the soft X-ray camera show that the trailing mass, precursor column, and R-T instability exist during the implosion phase, and kink instability will occur and rapidly develop after stagnation. The experimental results show that the product of the line mass and the square row width is a critical factor. This factor can affect the implosion times and the X-ray products of wire arrays with different parameters, the optimum range is 200~400 gcm for Qiangguang generator. The results also imply that the inter-wire gap should be smaller than 1 mm. The maximum X-ray total energy is 22 kJ with the peak power 630 GW while the maximum K-shell product is 3.9 kJ with 158 GW.
2014,
26: 055004.
doi: 10.11884/HPLPB201426.055004
Abstract:
In fabrication of vacuum electronics device, one of the most important steps is electroplating nickel coating on irregular parts. Ni coatings on the surface of irregular parts were prepared by moving-cathode electroplating technology. The effects of cathode movement on the propertieselectrodeposition rate, micro morphology, porosity and inner stress of Ni coatingwere investigated by XRF，CLSM， and bending-cathode methods. The results show that cathodic moving speed above 1.5 m/min can significantly reduce the pinholes phenomenon of coating, but not completely. Cathode movement would not affect the electrodeposition rate of the irregular parts, but it would make the crystalline particles of the coatings bigger, thus increase the surface roughness; cathode movement could reduce the porosity and the internal stress of the coatings remarkably but with little relationship to the moving speed.
In fabrication of vacuum electronics device, one of the most important steps is electroplating nickel coating on irregular parts. Ni coatings on the surface of irregular parts were prepared by moving-cathode electroplating technology. The effects of cathode movement on the propertieselectrodeposition rate, micro morphology, porosity and inner stress of Ni coatingwere investigated by XRF，CLSM， and bending-cathode methods. The results show that cathodic moving speed above 1.5 m/min can significantly reduce the pinholes phenomenon of coating, but not completely. Cathode movement would not affect the electrodeposition rate of the irregular parts, but it would make the crystalline particles of the coatings bigger, thus increase the surface roughness; cathode movement could reduce the porosity and the internal stress of the coatings remarkably but with little relationship to the moving speed.
2014,
26: 055005.
doi: 10.11884/HPLPB201426.055005
Abstract:
A compact fast raising-edge X-ray system is designed according to the principle Marx generator. Marx and X-ray tube are integrally designed , and both of them are encapsulated in a stainless steel barrel of diameter of 15 cm, length 1.2 m. Marx generator is designed based on wave erection principle that has 15-stage, theoretical energy of 90 J and theoretical output voltage of 600 kV in coaxial structure. For a charging voltage of 30 kV per stage, the raising time of output pulse is below 10 ns at 360 kV into a 75 load with 40 ns pulse width. With a flash X-ray tube integrated directly into the generator as a load, the formed flash X-ray system could generate a dose of 2.5810-5 C/kg at 30 cm away for flash X-radiography with pulse width 35 ns. The size of x-ray source is 2 mm. The X-ray system has a stable performance, and it is easy to operate. It is the ideal tool for high-speed radiation photography.
A compact fast raising-edge X-ray system is designed according to the principle Marx generator. Marx and X-ray tube are integrally designed , and both of them are encapsulated in a stainless steel barrel of diameter of 15 cm, length 1.2 m. Marx generator is designed based on wave erection principle that has 15-stage, theoretical energy of 90 J and theoretical output voltage of 600 kV in coaxial structure. For a charging voltage of 30 kV per stage, the raising time of output pulse is below 10 ns at 360 kV into a 75 load with 40 ns pulse width. With a flash X-ray tube integrated directly into the generator as a load, the formed flash X-ray system could generate a dose of 2.5810-5 C/kg at 30 cm away for flash X-radiography with pulse width 35 ns. The size of x-ray source is 2 mm. The X-ray system has a stable performance, and it is easy to operate. It is the ideal tool for high-speed radiation photography.
2014,
26: 055101.
doi: 10.11884/HPLPB201426.055101
Abstract:
Abstact: The spectrometry ring (SRing) is one of the rings of the next generation accelerator complex High Intensity Heavy Ion Accelerator Facility (HIAF) of Institute of Modern Physics of the Chinese Academy of Sciences. The SRing will be in operation mode as a time-of-flight mass spectrometer for short-lived nuclei. The SRings circumference is 188.7 m, the maximum magnetic rigidity is 13 T.m. The SRing is consisted by magnet systems, injection/extraction storages, stochastic cooling systems and detectors. It aims at stochastic precooling of both rare isotope and measuring nuclear masses in an isochronous mode. In order to fulfill its purpose, the ion optics can be set to different ion optical modes. This paper discusses the considerations of the injection/extraction storages of these two different modes.
Abstact: The spectrometry ring (SRing) is one of the rings of the next generation accelerator complex High Intensity Heavy Ion Accelerator Facility (HIAF) of Institute of Modern Physics of the Chinese Academy of Sciences. The SRing will be in operation mode as a time-of-flight mass spectrometer for short-lived nuclei. The SRings circumference is 188.7 m, the maximum magnetic rigidity is 13 T.m. The SRing is consisted by magnet systems, injection/extraction storages, stochastic cooling systems and detectors. It aims at stochastic precooling of both rare isotope and measuring nuclear masses in an isochronous mode. In order to fulfill its purpose, the ion optics can be set to different ion optical modes. This paper discusses the considerations of the injection/extraction storages of these two different modes.
2014,
26: 055102.
doi: 10.11884/HPLPB201426.055102
Abstract:
High-current ion source (IS) is one of the most important subsystems of accelerator driven sub-critical system (ADS), its parameters will determine the performance of the injector beam. So is the low energy beam transport (LEBT) subsystem. In order to confirm the IS and LEBTs effect, a remote control system based on the experimental and physics industrial control system (EPICS) is introduced in this paper. According to the characteristics of the devices interface and the user requirement, a programmable logic controller (PLC) and serial port servers are used as the hardware of the control system. The supervisory control software which is programmed with LabVIEW can control all equipments in the system. All of the parameters such as device status and variables are published on network in form of EPICS process variables (PVs) with the help of LabVIEW DSC module. The designed control system has a simple structure and it works reliably, which has played an important role for the IS and LEBT system testing.
High-current ion source (IS) is one of the most important subsystems of accelerator driven sub-critical system (ADS), its parameters will determine the performance of the injector beam. So is the low energy beam transport (LEBT) subsystem. In order to confirm the IS and LEBTs effect, a remote control system based on the experimental and physics industrial control system (EPICS) is introduced in this paper. According to the characteristics of the devices interface and the user requirement, a programmable logic controller (PLC) and serial port servers are used as the hardware of the control system. The supervisory control software which is programmed with LabVIEW can control all equipments in the system. All of the parameters such as device status and variables are published on network in form of EPICS process variables (PVs) with the help of LabVIEW DSC module. The designed control system has a simple structure and it works reliably, which has played an important role for the IS and LEBT system testing.
2014,
26: 059001.
doi: 10.11884/HPLPB201426.059001
Abstract:
In order to solve the weak edge detection of traditional industrial CT images shortcomings of poor detection effect and low speed, a detection method of step fuzzy inference algorithm and another method of improved defuzzification algorithm were researched. Compared with overall reasoning method, the step fuzzy inference algorithm selected similarity, gradient and consistency as blur characteristics. And the reasoning process used Mandani reasoning to conduct step fuzzy reasoning, which was based on simplified inference rule tables. Improved defuzzification algorithm was proposed in the solution process. According to membership function figure, the two methods were verified by experiments. The results showed that the step fuzzy inference algorithm was better in the weak edge detection, while the improved defuzzification algorithm greatly increased the computing speed on the premise of accuracy.
In order to solve the weak edge detection of traditional industrial CT images shortcomings of poor detection effect and low speed, a detection method of step fuzzy inference algorithm and another method of improved defuzzification algorithm were researched. Compared with overall reasoning method, the step fuzzy inference algorithm selected similarity, gradient and consistency as blur characteristics. And the reasoning process used Mandani reasoning to conduct step fuzzy reasoning, which was based on simplified inference rule tables. Improved defuzzification algorithm was proposed in the solution process. According to membership function figure, the two methods were verified by experiments. The results showed that the step fuzzy inference algorithm was better in the weak edge detection, while the improved defuzzification algorithm greatly increased the computing speed on the premise of accuracy.
Development of a hidden explosives security check instrument based on associated particles technique
2014,
26: 059002.
doi: 10.11884/HPLPB201426.059002
Abstract:
In response to the growing terrorist activities, a security check instrument for explosives detection based on associated particles technique (APT)/neutron time of flight(TOF) has been developed. This paper describes the instruments working principle and the development of his process. The instrument can be remotely controlled from any PC-compatible computer. Inside is an APT neutron generator with a 33 matrix of semiconductor detectors of associated alpha-particles, the shielding protection system of neutron and gamma-ray, support platform, arrayed NaI(Tl)-based detectors of gamma-rays, fully-digital data acquisition electronics, data analysis and decision-making software, and transmission device. The common explosives and chemical warfare agents were detected by security check instrument. Results show that the instrument can meet the needs of practical application. The instrument is mainly used to detect explosives in luggage at check routeway, and it can also be trained to detect other hazardous materials, such as chemical/toxic/drug materials, if their chemical composition is in any way different from that of the surrounding materials.
In response to the growing terrorist activities, a security check instrument for explosives detection based on associated particles technique (APT)/neutron time of flight(TOF) has been developed. This paper describes the instruments working principle and the development of his process. The instrument can be remotely controlled from any PC-compatible computer. Inside is an APT neutron generator with a 33 matrix of semiconductor detectors of associated alpha-particles, the shielding protection system of neutron and gamma-ray, support platform, arrayed NaI(Tl)-based detectors of gamma-rays, fully-digital data acquisition electronics, data analysis and decision-making software, and transmission device. The common explosives and chemical warfare agents were detected by security check instrument. Results show that the instrument can meet the needs of practical application. The instrument is mainly used to detect explosives in luggage at check routeway, and it can also be trained to detect other hazardous materials, such as chemical/toxic/drug materials, if their chemical composition is in any way different from that of the surrounding materials.
2014,
26: 059003.
doi: 10.11884/HPLPB201426.059003
Abstract:
Al+SiC powders were pulse-laser (Nd-YAG) cladded on AZ91D magnesium alloy. The microstructure, chemical composition and phase analyses of the cladding layer were studied by scanning electron microscopy (SEM), energy dispersive spectrometer (EDS) analysis, and X-ray diffraction (XRD) measurement. It can be seen that the composite coating is mainly composed of SiC and b-Mg17Al12 phases, and as well as metal phases of Mg and Al. The laser cladding showed very good bonding with the magnesium alloy substrate. It was found that with increasing SiC mass fraction, the spacing of the dendritic and cellular structure became larger. The surface hardness of cladding coating is higher than that of substrate, and the increase of SiC mass fraction can increase the surface hardness as the coating with 40% SiC particles shows a maximum hardness of about 180 HV, while that of 10% SiC particles is 136 HV. Sliding wear tests conducted in a pin-on-disc wear testing apparatus showed that the composite coating with SiC particles and in situ synthesized Mg17Al12 phase remarkably improved the wear resistance of the AZ91D magnesium alloy. The wear volume loss shows a decrease as the mass fraction of SiC increases from 10% to 30%, the coatings with about 20% to 30% SiC exhibit the best wear resistance.
Al+SiC powders were pulse-laser (Nd-YAG) cladded on AZ91D magnesium alloy. The microstructure, chemical composition and phase analyses of the cladding layer were studied by scanning electron microscopy (SEM), energy dispersive spectrometer (EDS) analysis, and X-ray diffraction (XRD) measurement. It can be seen that the composite coating is mainly composed of SiC and b-Mg17Al12 phases, and as well as metal phases of Mg and Al. The laser cladding showed very good bonding with the magnesium alloy substrate. It was found that with increasing SiC mass fraction, the spacing of the dendritic and cellular structure became larger. The surface hardness of cladding coating is higher than that of substrate, and the increase of SiC mass fraction can increase the surface hardness as the coating with 40% SiC particles shows a maximum hardness of about 180 HV, while that of 10% SiC particles is 136 HV. Sliding wear tests conducted in a pin-on-disc wear testing apparatus showed that the composite coating with SiC particles and in situ synthesized Mg17Al12 phase remarkably improved the wear resistance of the AZ91D magnesium alloy. The wear volume loss shows a decrease as the mass fraction of SiC increases from 10% to 30%, the coatings with about 20% to 30% SiC exhibit the best wear resistance.
2014,
26: 059004.
doi: 10.11884/HPLPB201426.059004
Abstract:
A beam hardening correction method based on indexing projection and weight function is proposed to remove the cupping artifacts of low-energy X-ray industrial CT images and to improve the identification capability and quantitative analysis. Firstly, it is concluded from theoretical analysis that cupping artifacts is dominated by beam hardening occurring when X-ray continuous spectrum passes through the object to be measured. Then, projection data and line attenuation coefficient of different thickness are acquired through scanning ladder model. The hardening model function and weight function correction model function which determines the power function are obtained by fitting curve. Furthermore, we scan the measured round workpiece to get the projection data under different indexing. Finally, for each index projection data, the projection data of cupping artifacts are corrected by combining the weight function and current indexing projection data. A correction experiment is carried out in the actual CT images including cupping artifacts. The result indicates that the SNR of gray image using the proposed method has increased by 3.29% with no amplification of noise, which shows that the proposed method more effectively eliminates the cupping artifacts and keeps better image edges as compared with the polynomial fitting method.
A beam hardening correction method based on indexing projection and weight function is proposed to remove the cupping artifacts of low-energy X-ray industrial CT images and to improve the identification capability and quantitative analysis. Firstly, it is concluded from theoretical analysis that cupping artifacts is dominated by beam hardening occurring when X-ray continuous spectrum passes through the object to be measured. Then, projection data and line attenuation coefficient of different thickness are acquired through scanning ladder model. The hardening model function and weight function correction model function which determines the power function are obtained by fitting curve. Furthermore, we scan the measured round workpiece to get the projection data under different indexing. Finally, for each index projection data, the projection data of cupping artifacts are corrected by combining the weight function and current indexing projection data. A correction experiment is carried out in the actual CT images including cupping artifacts. The result indicates that the SNR of gray image using the proposed method has increased by 3.29% with no amplification of noise, which shows that the proposed method more effectively eliminates the cupping artifacts and keeps better image edges as compared with the polynomial fitting method.
2014,
26: 059005.
doi: 10.11884/HPLPB201426.059005
Abstract:
To improve the carburized layer quality and wear performance of 12CrNi3A steel, a composite technology of laser shock processing and carburization was put forward. The results of ball milling experiment showed that the specific wear rate of specimen treated by carburization after laser shock processing reduced by 51% compared with that treated by carburization only, and was reduced by 13% compared with that treated by laser shock processing after carburization. It shows that the composite technology of carburization after laser shock processing can improve the wear resistance of 12CrNi3A steel effectively. The cause of the improvement of wear resistance is the increasing of micro-hardness and the diversification of the microscopic structure, when the coefficient of friction is in a invariant state. The mechanism of wear resistance improvement was analyzed using micro-hardness and scanning electron microscope (SEM). The results indicate that the laser shock processing can promote the process of carburization. The structure of carburized layer is compact and a large number of fine carbide particles are formed in the surface treated by carburization after laser shock processing, which leads to the increasing of the second phase strengthening and solution strengthening in the carburized layer, and the micro-hardness and wear resistance are improved. But the laser shock processing after carburization only affects the surface deformation, and the improvement of micro-hardness and wear resistance is limited compared with carburization.
To improve the carburized layer quality and wear performance of 12CrNi3A steel, a composite technology of laser shock processing and carburization was put forward. The results of ball milling experiment showed that the specific wear rate of specimen treated by carburization after laser shock processing reduced by 51% compared with that treated by carburization only, and was reduced by 13% compared with that treated by laser shock processing after carburization. It shows that the composite technology of carburization after laser shock processing can improve the wear resistance of 12CrNi3A steel effectively. The cause of the improvement of wear resistance is the increasing of micro-hardness and the diversification of the microscopic structure, when the coefficient of friction is in a invariant state. The mechanism of wear resistance improvement was analyzed using micro-hardness and scanning electron microscope (SEM). The results indicate that the laser shock processing can promote the process of carburization. The structure of carburized layer is compact and a large number of fine carbide particles are formed in the surface treated by carburization after laser shock processing, which leads to the increasing of the second phase strengthening and solution strengthening in the carburized layer, and the micro-hardness and wear resistance are improved. But the laser shock processing after carburization only affects the surface deformation, and the improvement of micro-hardness and wear resistance is limited compared with carburization.
2014,
26: 059006.
doi: 10.11884/HPLPB201426.059006
Abstract:
To solve the problem of huge amount of data sets and narrow triangles existed in triangular mesh model, a feature-preserving and high quality triangular mesh simplification and optimization method was studied. The method was divided into two stages: mesh simplification and mesh optimization. Firstly, it adopted quadric error metric based surface variation to compute the edge collapsing cost, and iteratively simplified mesh model according to the cost, which could efficiently preserve the features on the surface. Secondly, the local narrow triangles were optimized by a weighted second-order umbrella operator, and the quality of mesh model was improved by this way. The experiment results show that this method works well for preserving detailed information of feature regions whilst reliably producing high-quality and low geometrical error simplified mesh.
To solve the problem of huge amount of data sets and narrow triangles existed in triangular mesh model, a feature-preserving and high quality triangular mesh simplification and optimization method was studied. The method was divided into two stages: mesh simplification and mesh optimization. Firstly, it adopted quadric error metric based surface variation to compute the edge collapsing cost, and iteratively simplified mesh model according to the cost, which could efficiently preserve the features on the surface. Secondly, the local narrow triangles were optimized by a weighted second-order umbrella operator, and the quality of mesh model was improved by this way. The experiment results show that this method works well for preserving detailed information of feature regions whilst reliably producing high-quality and low geometrical error simplified mesh.
2014,
26: 054003.
doi: 10.11884/HPLPB201426.054003
Abstract:
A fast back-projection method is established. This method does not need to search all image space, but just to check and search the pixels inside the scope determined by scatter events. So the computational speed of image reconstruction is greatly improved. This method is applied to data from a simulation prototype of a neutron scatter camera with five detector elements. The results show that the reconstruction result is the same as the true point source at azimuth, and it takes only 3 seconds to process 1000 scatter events by this method, the angular resolution of reconstruction result is 8.0. The influence of the reconstruction parameters on runtime and resolution was analyzed,and the conclusion indicates that this method is of advantage to reconstruction the distribution of neutron sourcefor neutron detection in large field of view.
A fast back-projection method is established. This method does not need to search all image space, but just to check and search the pixels inside the scope determined by scatter events. So the computational speed of image reconstruction is greatly improved. This method is applied to data from a simulation prototype of a neutron scatter camera with five detector elements. The results show that the reconstruction result is the same as the true point source at azimuth, and it takes only 3 seconds to process 1000 scatter events by this method, the angular resolution of reconstruction result is 8.0. The influence of the reconstruction parameters on runtime and resolution was analyzed,and the conclusion indicates that this method is of advantage to reconstruction the distribution of neutron sourcefor neutron detection in large field of view.
