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RSS2016 Vol. 28, No. 12
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2016,
28: 121001.
doi: 10.11884/HPLPB201628.160113
Abstract:
The advantages and disadvantages in nonuniformity correction method (NUC) based on calibration and scene of infrared focal plane array (IRFPA) were analyzed respectively. On this basis, a combined non-uniformity correction method was presented. According to the temperature of focal plane substrate at the moment of power on, previously stored gain and bias correction parameters were extracted from the FLASH for the corresponding temperature interval to eliminate the non-uniformity of detector preliminarily. After preliminary correction, a self-adaptive non-uniformity correction algorithm was presented in order to eliminate residual noises. The images after preliminary correction were decomposed by non-subsampled contourlet transform(NSCT), and the Bayesian threshold was used to estimate the signal and noise variance point by point. As a result, the residual non-uniformity noise was figured out and then got rid of. Experimental results show that such an algorithm could improve both the correction accuracy and the environmental adaptability effectively.
The advantages and disadvantages in nonuniformity correction method (NUC) based on calibration and scene of infrared focal plane array (IRFPA) were analyzed respectively. On this basis, a combined non-uniformity correction method was presented. According to the temperature of focal plane substrate at the moment of power on, previously stored gain and bias correction parameters were extracted from the FLASH for the corresponding temperature interval to eliminate the non-uniformity of detector preliminarily. After preliminary correction, a self-adaptive non-uniformity correction algorithm was presented in order to eliminate residual noises. The images after preliminary correction were decomposed by non-subsampled contourlet transform(NSCT), and the Bayesian threshold was used to estimate the signal and noise variance point by point. As a result, the residual non-uniformity noise was figured out and then got rid of. Experimental results show that such an algorithm could improve both the correction accuracy and the environmental adaptability effectively.
2016,
28: 122001.
doi: 10.11884/HPLPB201628.160137
Abstract:
Axial X-ray radiations of four types of wire-arrays were diagnosed via 1-D streak camera system on JL-Ⅰ. Because of the influence of Rayleigh-Taylor instability, wire-arrays mostly had the behavior that X-ray rose up later near both cathode and anode than that of the middle, X-ray near anode rose up later than that of cathode and the intensity of X-ray close to anode seemed weaker than that of cathode. With the comparison of different types of wire-arrays, the optimized mass per unit length of a 20 mm diameter wire-array on JL-Ⅰ was about 0.9 mg/cm. Further, there was a correlation between axial radiation synchronization and radiation power.
Axial X-ray radiations of four types of wire-arrays were diagnosed via 1-D streak camera system on JL-Ⅰ. Because of the influence of Rayleigh-Taylor instability, wire-arrays mostly had the behavior that X-ray rose up later near both cathode and anode than that of the middle, X-ray near anode rose up later than that of cathode and the intensity of X-ray close to anode seemed weaker than that of cathode. With the comparison of different types of wire-arrays, the optimized mass per unit length of a 20 mm diameter wire-array on JL-Ⅰ was about 0.9 mg/cm. Further, there was a correlation between axial radiation synchronization and radiation power.
2016,
28: 122002.
doi: 10.11884/HPLPB201628.160440
Abstract:
A multi-energy-point emission spectrum measurement system can be implemented on primary test stand (PTS) facility based on multilayer covering from 50 eV to 1500 eV quasi monochromatically. The information of spectrum structure and total energy of this Z-pinch plasma X-ray radiation source can be obtained from this system. The multilayer working at 13 nm is required to operate under a grazing incidence angle of 60 given the facility condition. The highest reflectivity can be achieved by the conventional Mo/Si multilayer, but it will display a large bandwidth, which cannot satisfy the quasi-monochromatic requirement for the multilayer. This paper proposes that taking Mo and C together as the absorbing materials to combine with Si to form Si/Mo/C multilayer, which can significantly reduce the bandwidth with a slight decrease of the reflectivity. This kind of Si/Mo/C multilayer was fabricated by direct current magnetron sputtering technique. The grazing incidence X-ray reflectivity (GIXR) has shown the multilayer with a clear and complete structure. The EUV reflectivity measurement at the synchrotron radiation light source has demonstrated this Si/Mo/C multilayer with a reflectivity of 56.5% and a bandwidth of 0.49 nm (3.7 eV).
A multi-energy-point emission spectrum measurement system can be implemented on primary test stand (PTS) facility based on multilayer covering from 50 eV to 1500 eV quasi monochromatically. The information of spectrum structure and total energy of this Z-pinch plasma X-ray radiation source can be obtained from this system. The multilayer working at 13 nm is required to operate under a grazing incidence angle of 60 given the facility condition. The highest reflectivity can be achieved by the conventional Mo/Si multilayer, but it will display a large bandwidth, which cannot satisfy the quasi-monochromatic requirement for the multilayer. This paper proposes that taking Mo and C together as the absorbing materials to combine with Si to form Si/Mo/C multilayer, which can significantly reduce the bandwidth with a slight decrease of the reflectivity. This kind of Si/Mo/C multilayer was fabricated by direct current magnetron sputtering technique. The grazing incidence X-ray reflectivity (GIXR) has shown the multilayer with a clear and complete structure. The EUV reflectivity measurement at the synchrotron radiation light source has demonstrated this Si/Mo/C multilayer with a reflectivity of 56.5% and a bandwidth of 0.49 nm (3.7 eV).
2016,
28: 123001.
doi: 10.11884/HPLPB201628.160459
Abstract:
Based on the operating principle of the original high-power mTM0n-TEM/TM01 mixed mode converters, which are specially designed on the certain TM0n mode content and relative phase, the investigation on purification of high-power TM0n mixed modes is carried out in this paper. With this method, TM0n mixed modes at GW level with any mode content and relative phase can be converted into pure TEM mode or TM01 mode. The original high-power mTM0n-TEM/TM01 mixed mode converters are optimally redesigned by the method proposed in this paper, the improved mode converters not only keep the original power capacity and bandwidth property, but also have a simplified structure.
Based on the operating principle of the original high-power mTM0n-TEM/TM01 mixed mode converters, which are specially designed on the certain TM0n mode content and relative phase, the investigation on purification of high-power TM0n mixed modes is carried out in this paper. With this method, TM0n mixed modes at GW level with any mode content and relative phase can be converted into pure TEM mode or TM01 mode. The original high-power mTM0n-TEM/TM01 mixed mode converters are optimally redesigned by the method proposed in this paper, the improved mode converters not only keep the original power capacity and bandwidth property, but also have a simplified structure.
2016,
28: 123002.
doi: 10.11884/HPLPB201628.160159
Abstract:
Based on two cascaded polarization modulators, a stable frequency-sextupled microwave signal generation approach with high spectral purity is presented. Without optical filter, a frequency-sextupled microwave signal of any wave-band was obtained by adjusting the direction of polarizers, the voltage and the phases of radio frequency driven signals. A simulation system was set up based on an OptiSystem platform, and the quality of the generated frequency-sextupled signal, using 4 GHz signal as an example, was verified. Further, the influences of non-ideal radio frequency driven voltage and phases on the quality of the generated frequency-sextupled signal were analyzed as well. The results show that the designed system can generate frequency-sextupled signal with maximum optical sideband suppression ratio and radio frequency spurious suppression ratio of 21.3 dB, 15.2 dB, respectively. In order to obtain the higher quality microwave signal, the non-ideal deviations from ideal driven voltage and phase difference should be controlled within 5%.
Based on two cascaded polarization modulators, a stable frequency-sextupled microwave signal generation approach with high spectral purity is presented. Without optical filter, a frequency-sextupled microwave signal of any wave-band was obtained by adjusting the direction of polarizers, the voltage and the phases of radio frequency driven signals. A simulation system was set up based on an OptiSystem platform, and the quality of the generated frequency-sextupled signal, using 4 GHz signal as an example, was verified. Further, the influences of non-ideal radio frequency driven voltage and phases on the quality of the generated frequency-sextupled signal were analyzed as well. The results show that the designed system can generate frequency-sextupled signal with maximum optical sideband suppression ratio and radio frequency spurious suppression ratio of 21.3 dB, 15.2 dB, respectively. In order to obtain the higher quality microwave signal, the non-ideal deviations from ideal driven voltage and phase difference should be controlled within 5%.
2016,
28: 123003.
doi: 10.11884/HPLPB201628.160434
Abstract:
This paper presents a simulation study on intense relative multi-beams(IRMBs) electron explosive emission and structure optimizing of cathodes in the relative klystron amplifier(RKA) diode with PIC simulation software. Three new kinds of structures for multi-beam cathodes are introduced. The result shows that, the traditional structure cathode could only get the injection coefficient of IRMBs up to 82%, while the new structure cathode could increase it to more than 95%, even 99%. This research gives a solution to the problem of low injection coefficient in the multi-beams RKA.
This paper presents a simulation study on intense relative multi-beams(IRMBs) electron explosive emission and structure optimizing of cathodes in the relative klystron amplifier(RKA) diode with PIC simulation software. Three new kinds of structures for multi-beam cathodes are introduced. The result shows that, the traditional structure cathode could only get the injection coefficient of IRMBs up to 82%, while the new structure cathode could increase it to more than 95%, even 99%. This research gives a solution to the problem of low injection coefficient in the multi-beams RKA.
2016,
28: 123201.
doi: 10.11884/HPLPB201628.160421
Abstract:
Based on electromagnetic topology and equivalent circuit method, this paper presents an analytic method for the fast prediction of the load response of the transmission line in an enclosure with apertures, irradiated by an external plane wave. In the method, the whole electromagnetic coupling problem is firstly decomposed into two relatively simple sub problems: a) the external plane wave irradiates an empty enclosure with apertures and generates interior coupling EM field, and b) the coupling field irradiates the isolated transmission line and generates the load response. Then, the coupling field is computed by equivalent circuit method, and the load response of the transmission line is computed by BLT equation. The validity of the analytic method is verified by CST simulation tool. The results show that the analytic method can calculate the load response of the transmission line fast and efficiently, and costs much fewer computing resources compared with numerical methods. In addition, the analytic method offers designers feasibility to study influence parameters on the load response of the transmission line, while it is difficult with numerical methods.
Based on electromagnetic topology and equivalent circuit method, this paper presents an analytic method for the fast prediction of the load response of the transmission line in an enclosure with apertures, irradiated by an external plane wave. In the method, the whole electromagnetic coupling problem is firstly decomposed into two relatively simple sub problems: a) the external plane wave irradiates an empty enclosure with apertures and generates interior coupling EM field, and b) the coupling field irradiates the isolated transmission line and generates the load response. Then, the coupling field is computed by equivalent circuit method, and the load response of the transmission line is computed by BLT equation. The validity of the analytic method is verified by CST simulation tool. The results show that the analytic method can calculate the load response of the transmission line fast and efficiently, and costs much fewer computing resources compared with numerical methods. In addition, the analytic method offers designers feasibility to study influence parameters on the load response of the transmission line, while it is difficult with numerical methods.
2016,
28: 123202.
doi: 10.11884/HPLPB201628.160437
Abstract:
With the double-cavity cascade system, the induced voltage of output port is measured. The statistical result of the experimental data matches basically with the calculated result, which verifies the practicability of the random topology model. With this model, the statistical characteristics of electromagnetic pulse coupling on the complex system with different pulse parameters, as well as different topology structures are discussed. Research shows that, both pulse widths and pulse number have some resonant characteristics with induced voltage of peak probability. And the lower pulse frequency is, the higher coupling efficiency will be. The serial topology structure is most beneficial to the protection and reinforcement of system.
With the double-cavity cascade system, the induced voltage of output port is measured. The statistical result of the experimental data matches basically with the calculated result, which verifies the practicability of the random topology model. With this model, the statistical characteristics of electromagnetic pulse coupling on the complex system with different pulse parameters, as well as different topology structures are discussed. Research shows that, both pulse widths and pulse number have some resonant characteristics with induced voltage of peak probability. And the lower pulse frequency is, the higher coupling efficiency will be. The serial topology structure is most beneficial to the protection and reinforcement of system.
2016,
28: 124001.
doi: 10.11884/HPLPB201628.160148
Abstract:
Boundary of different materials is one of the focus in flash X-ray radiography, low signal-to-noise ratio and microcosmic structure block the exact distilling of material boundary. In this paper, Markov random field method is researched, Markov model is used to describe the relativity between different pixels, to reduce the number of false target root in noise; through the variance of pixels in template with hollow center the energy cliques function is described, the segment result of microcosmic structure and segment precision of flash X-ray radiography are improved. Simulation shows the modified MRF method in this paper can get better segment result.
Boundary of different materials is one of the focus in flash X-ray radiography, low signal-to-noise ratio and microcosmic structure block the exact distilling of material boundary. In this paper, Markov random field method is researched, Markov model is used to describe the relativity between different pixels, to reduce the number of false target root in noise; through the variance of pixels in template with hollow center the energy cliques function is described, the segment result of microcosmic structure and segment precision of flash X-ray radiography are improved. Simulation shows the modified MRF method in this paper can get better segment result.
2016,
28: 124002.
doi: 10.11884/HPLPB201628.160079
Abstract:
It is of great importance to reduce secondary electron yield (SEY) of metals in order to improve performance of electronic vacuum devices. This paper focuses on the experimental study on SEY suppression of copper. First, by using the Casino software, the SEY of square hole array surface was simulated under normal incident primary electron with energy of 0.5, 3 keV respectively. The aspect ratio and porosity dependence of the intrinsic SEY (ISEY), backscattered SEY (BSEY) and total SEY (TSEY) were obtained. Second, by using the photolithography process in semiconductor industry, various circular hole arrays were fabricated on copper foil and their surface morphology were characterized using a laser scanning microscope, their SEY were measured on SEY test platform. Simulation results show that: with increasing aspect ratio and porosity, the SEY suppression effect can be enhanced; when aspect ratio is becoming large enough, the SEY tend to be saturated; the SEY suppression effect is more obvious when incident energy is low. Measurement results show that the micro-hole array surface can effectively suppress the SEY of copper and experimental results agrees qualitatively with simulation results.
It is of great importance to reduce secondary electron yield (SEY) of metals in order to improve performance of electronic vacuum devices. This paper focuses on the experimental study on SEY suppression of copper. First, by using the Casino software, the SEY of square hole array surface was simulated under normal incident primary electron with energy of 0.5, 3 keV respectively. The aspect ratio and porosity dependence of the intrinsic SEY (ISEY), backscattered SEY (BSEY) and total SEY (TSEY) were obtained. Second, by using the photolithography process in semiconductor industry, various circular hole arrays were fabricated on copper foil and their surface morphology were characterized using a laser scanning microscope, their SEY were measured on SEY test platform. Simulation results show that: with increasing aspect ratio and porosity, the SEY suppression effect can be enhanced; when aspect ratio is becoming large enough, the SEY tend to be saturated; the SEY suppression effect is more obvious when incident energy is low. Measurement results show that the micro-hole array surface can effectively suppress the SEY of copper and experimental results agrees qualitatively with simulation results.
2016,
28: 124003.
doi: 10.11884/HPLPB201628.160067
Abstract:
Ring-coded aperture imaging system is used to diagnose low intensity pulsed radiation source, which performs high resolution and high signal-to-noise ratio (SNR). Through Geant4 Monte Carlo toolkit, this paper simulates the system to get six point spread function (PSF) of point sources centered at different distance and the coded image of neutron source made up of a group of lines. Sectioned restoration algorithm is one of the methods to solve image restoration of space-variant point spread function. Firstly, the reconstructed image is divided to rectangle section or circle section. Each sub-section is restored by RL iterative method. Then, the boundary regions which bring obvious noise are removed. Those pixels are superposed by adjacent sections with weighting coefficient, which is the proportion of the distance between pixels and boundary. At last, the sub-frames are spliced together to construct integrated image. Computer simulations indicates the modified method is effective for removing the boundary distortion, which can diagnose the distribution of radiation source.
Ring-coded aperture imaging system is used to diagnose low intensity pulsed radiation source, which performs high resolution and high signal-to-noise ratio (SNR). Through Geant4 Monte Carlo toolkit, this paper simulates the system to get six point spread function (PSF) of point sources centered at different distance and the coded image of neutron source made up of a group of lines. Sectioned restoration algorithm is one of the methods to solve image restoration of space-variant point spread function. Firstly, the reconstructed image is divided to rectangle section or circle section. Each sub-section is restored by RL iterative method. Then, the boundary regions which bring obvious noise are removed. Those pixels are superposed by adjacent sections with weighting coefficient, which is the proportion of the distance between pixels and boundary. At last, the sub-frames are spliced together to construct integrated image. Computer simulations indicates the modified method is effective for removing the boundary distortion, which can diagnose the distribution of radiation source.
2016,
28: 124004.
doi: 10.11884/HPLPB201628.160121
Abstract:
To satisfy the progressive requirements of test, a neutron standard test beam based on the reactor neutron source China Mianyang Research Reactor(CMRR) was proposed, and its conceptual design is shown in the paper. This instrument would be used to test the performance of components designed for spectrometer and develop some quantitative analysis of special materials. At first, it was simulated by VITESS software. Then some adjustment about its physical parameter was optimized based on the simulation results. In this system, the monochoromator was designed with vertical focusing function which could provide neutrons with continuous wavelength (0.1-0.3 nm). Between the monitor and the slit, the collimator was removable. While it is removed, the neutron flux at sample stage was up to 6.15106 n/(cm2s). With the collimater, the neutron flux at sample stage was reduced to 2.07106 n/(cm2s), but the resolution of NSTB was up to 0.2%.
To satisfy the progressive requirements of test, a neutron standard test beam based on the reactor neutron source China Mianyang Research Reactor(CMRR) was proposed, and its conceptual design is shown in the paper. This instrument would be used to test the performance of components designed for spectrometer and develop some quantitative analysis of special materials. At first, it was simulated by VITESS software. Then some adjustment about its physical parameter was optimized based on the simulation results. In this system, the monochoromator was designed with vertical focusing function which could provide neutrons with continuous wavelength (0.1-0.3 nm). Between the monitor and the slit, the collimator was removable. While it is removed, the neutron flux at sample stage was up to 6.15106 n/(cm2s). With the collimater, the neutron flux at sample stage was reduced to 2.07106 n/(cm2s), but the resolution of NSTB was up to 0.2%.
2016,
28: 124005.
doi: 10.11884/HPLPB201628.160414
Abstract:
The picosecond laser pulse neutron source experiment was demonstrated on Xingguang-Ⅲ facility. A good neutron signal was measured by liquid scintillator detector. The neutron energy distribution with time was obtained by time-of-flight method, and the charge between different energy intervals was acquired by the ratio of the integral of oscilloscope voltage and time to oscillator input resistance. Geant4 calculation model for liquid scintillator detector under experimental and calibration cases were established, and the neutron sensitivity was obtained by the ratio of the collected optical photons. Neutron energy spectrum for picosecond laser pulse neutron source was calculated, and the neutron yield below 1 MeV in the direction of liquid scintillator detector was 1.04108 sr-1.
The picosecond laser pulse neutron source experiment was demonstrated on Xingguang-Ⅲ facility. A good neutron signal was measured by liquid scintillator detector. The neutron energy distribution with time was obtained by time-of-flight method, and the charge between different energy intervals was acquired by the ratio of the integral of oscilloscope voltage and time to oscillator input resistance. Geant4 calculation model for liquid scintillator detector under experimental and calibration cases were established, and the neutron sensitivity was obtained by the ratio of the collected optical photons. Neutron energy spectrum for picosecond laser pulse neutron source was calculated, and the neutron yield below 1 MeV in the direction of liquid scintillator detector was 1.04108 sr-1.
2016,
28: 124101.
doi: 10.11884/HPLPB201628.160135
Abstract:
Threecommercial 3-dimension printers were used to fabricate micro target components with metal and resin materials. A titanium metal target frame was fabricated by EOSINT M290 3D printer by the means of Laser Sintering. Resin target frames,microcavityand cylinder were fabricated by Object 30 Pro 3D printer throughPolyjetmeans using polypropylene resin as printing material. The surface ofmicrocavity, cylinder and slice designed with periodic pattern were fabricated by Freeform Pico 3D printer through the means of stereo lithography apparatus applying wax resin as printing material. The size and surface morphology of samples were characterized by optical microscope and laser scanningconfocalmicroscope. The results show that the line roughness of titanium metal target frame is 7.3-17.79mand it decreased to 0.87-1.66mafter polishing. The root mean square roughness (RMS) of resin frame is 2.88m. The RMS of the end surface ofmicrocavityand cylinder is 2.03m; the deviation between measured value and designed value of streak pattern period on themicrocavityand cylinder side is 1.40% and that of amplitude is 55.50%. The RMS of slice component is 4.87m, the deviation of modulation pattern period is 0.80% and that of the amplitude is 3.60%. Application of commercial 3D printer to fabricate micro target components, with high efficiency and low cost provides a new approach for the manufacturing of target components used in inertial confinement fusion experiment.
Threecommercial 3-dimension printers were used to fabricate micro target components with metal and resin materials. A titanium metal target frame was fabricated by EOSINT M290 3D printer by the means of Laser Sintering. Resin target frames,microcavityand cylinder were fabricated by Object 30 Pro 3D printer throughPolyjetmeans using polypropylene resin as printing material. The surface ofmicrocavity, cylinder and slice designed with periodic pattern were fabricated by Freeform Pico 3D printer through the means of stereo lithography apparatus applying wax resin as printing material. The size and surface morphology of samples were characterized by optical microscope and laser scanningconfocalmicroscope. The results show that the line roughness of titanium metal target frame is 7.3-17.79mand it decreased to 0.87-1.66mafter polishing. The root mean square roughness (RMS) of resin frame is 2.88m. The RMS of the end surface ofmicrocavityand cylinder is 2.03m; the deviation between measured value and designed value of streak pattern period on themicrocavityand cylinder side is 1.40% and that of amplitude is 55.50%. The RMS of slice component is 4.87m, the deviation of modulation pattern period is 0.80% and that of the amplitude is 3.60%. Application of commercial 3D printer to fabricate micro target components, with high efficiency and low cost provides a new approach for the manufacturing of target components used in inertial confinement fusion experiment.
2016,
28: 124102.
doi: 10.11884/HPLPB201628.160161
Abstract:
With the development of microelectronics technology, small size, high integration density and low voltage devices are increasingly used in avionics. Many researchers found that the particle radiation caused by the charged particles in upper atmosphere have a significant impact on avionic devices. In consideration of the potential safety hazard by single event upsets and the urgent demand of airborne equipment localization, this paper reports the research and analysis of the single event upset problems of FPGA devices applied in the airborne electronic equipment. Firstly, the flight experimental data of mainstream FPGAs at the aviation flight altitudes are analyzed. Then, further demonstration is made about whether these FPGA devices meet the needs of civil aviation. The analysis results show that single event upset is an indispensable problem according to the conditions of mainstream FPGA chip with the small size and working voltage. Even the FPGA devices are working at the air flight altitude or near the ground, the failure caused by single event upset would make them unable to meet the safety requirements of civil aviation equipment.
With the development of microelectronics technology, small size, high integration density and low voltage devices are increasingly used in avionics. Many researchers found that the particle radiation caused by the charged particles in upper atmosphere have a significant impact on avionic devices. In consideration of the potential safety hazard by single event upsets and the urgent demand of airborne equipment localization, this paper reports the research and analysis of the single event upset problems of FPGA devices applied in the airborne electronic equipment. Firstly, the flight experimental data of mainstream FPGAs at the aviation flight altitudes are analyzed. Then, further demonstration is made about whether these FPGA devices meet the needs of civil aviation. The analysis results show that single event upset is an indispensable problem according to the conditions of mainstream FPGA chip with the small size and working voltage. Even the FPGA devices are working at the air flight altitude or near the ground, the failure caused by single event upset would make them unable to meet the safety requirements of civil aviation equipment.
2016,
28: 124103.
doi: 10.11884/HPLPB201628.160428
Abstract:
The fabrication induced by ultrafast laser illumination on solid surface has been widely illustrated in the field of laser physics. A new nanoscale-structure fabrication method based on the local surface plasmon resonance of the quantum dots (QDs) which are adhered on the substrate is demonstrated. By illuminating a K9 substrate which has been coated by Cu2S QDs with femtosecond laser, a series of grating-like and sub-wavelength period strips are achieved. The interval between each strip is nearly 34 nm when the central wavelength, pulse duration and illumination power of the laser are 1300 nm, 50 fs and 230 mW respectively. Moreover, the mechanism of inducing period strips has been demonstrated by the simulated near field distribution of the adhered QDs on substrate. The result shows that the period strips result from the interference between femtosecond laser and localized plasmon induced by QDs. This preparation method can not only reduce the laser threshold of nanoscale-structure fabrication of transparent medium, but also improve the processing technology of the micro-nano structure on the surface of the transparent substrate.
The fabrication induced by ultrafast laser illumination on solid surface has been widely illustrated in the field of laser physics. A new nanoscale-structure fabrication method based on the local surface plasmon resonance of the quantum dots (QDs) which are adhered on the substrate is demonstrated. By illuminating a K9 substrate which has been coated by Cu2S QDs with femtosecond laser, a series of grating-like and sub-wavelength period strips are achieved. The interval between each strip is nearly 34 nm when the central wavelength, pulse duration and illumination power of the laser are 1300 nm, 50 fs and 230 mW respectively. Moreover, the mechanism of inducing period strips has been demonstrated by the simulated near field distribution of the adhered QDs on substrate. The result shows that the period strips result from the interference between femtosecond laser and localized plasmon induced by QDs. This preparation method can not only reduce the laser threshold of nanoscale-structure fabrication of transparent medium, but also improve the processing technology of the micro-nano structure on the surface of the transparent substrate.
2016,
28: 125001.
doi: 10.11884/HPLPB201628.160128
Abstract:
In field-distortion gas spark switch, discharge channel between two electrodes can be conducted rapidly in argon gap, as abundant metastable atoms excite in argon. In this paper, a series of experiments to support the superiority of spark gap using argon gas mixtures were accomplished. The discharge characteristics of gas mixtures(SF6-Ar and N2-Ar) in spark gap were obtained under DC voltage. On this basis, we can get the optimized argon percentage of gas mixtures and figure out the breakdown characteristics of gas mixtures in spark gap. The spark gap using SF6-Ar can reach a lower jitter when the percentage of argon is higher than 20%. However there is no ideal performance using N2-Ar mixtures.
In field-distortion gas spark switch, discharge channel between two electrodes can be conducted rapidly in argon gap, as abundant metastable atoms excite in argon. In this paper, a series of experiments to support the superiority of spark gap using argon gas mixtures were accomplished. The discharge characteristics of gas mixtures(SF6-Ar and N2-Ar) in spark gap were obtained under DC voltage. On this basis, we can get the optimized argon percentage of gas mixtures and figure out the breakdown characteristics of gas mixtures in spark gap. The spark gap using SF6-Ar can reach a lower jitter when the percentage of argon is higher than 20%. However there is no ideal performance using N2-Ar mixtures.
2016,
28: 125002.
doi: 10.11884/HPLPB201628.160158
Abstract:
Generating low-temperature plasma with high density requires fast pulses with high repetitive frequency, nanosecond rise time and nanosecond pulse width, which is very difficult for the widely used MOSFET and IGBT. Studies show that the bipolar junction transistors avalanche breakdown process has the characteristics of fast conduction, fast recovery and high stability, which is suitable for the self-breakdown switches in compact solid-state Marx generators. In this paper, it is found that the avalanche breakdown voltage can be adjusted by changing the resistance between BJTs gate and emitter. The experiments of avalanche breakdown and recovery show that BJT will turn off when the breakdown current attenuates below the maintain current, so the BJT avalanche breakdowns conduction time can be controlled by adjusting the parameters to change the attenuation of the discharging current in the circuit. Applying these conclusions to the actual circuit, fast pulses, with rise time of 5 ns, pulse width of 10 ns and amplitude of 2 kV and frequency of 100 kHz, are obtained.
Generating low-temperature plasma with high density requires fast pulses with high repetitive frequency, nanosecond rise time and nanosecond pulse width, which is very difficult for the widely used MOSFET and IGBT. Studies show that the bipolar junction transistors avalanche breakdown process has the characteristics of fast conduction, fast recovery and high stability, which is suitable for the self-breakdown switches in compact solid-state Marx generators. In this paper, it is found that the avalanche breakdown voltage can be adjusted by changing the resistance between BJTs gate and emitter. The experiments of avalanche breakdown and recovery show that BJT will turn off when the breakdown current attenuates below the maintain current, so the BJT avalanche breakdowns conduction time can be controlled by adjusting the parameters to change the attenuation of the discharging current in the circuit. Applying these conclusions to the actual circuit, fast pulses, with rise time of 5 ns, pulse width of 10 ns and amplitude of 2 kV and frequency of 100 kHz, are obtained.
2016,
28: 125003.
doi: 10.11884/HPLPB201628.160167
Abstract:
Varistors and transient voltage suppressor (TVS) diodes, as two typical surge protective devices, are often used to limit voltage in the high power microwave pulse. To investigate their nanosecond pulse response and provide a scientific basis for the selection of electromagnetic pulse interference protection devices, the experimental measurement were carried out by the way of hundreds of nanoseconds and two nanoseconds risetime pulses injecting directly. Moreover, the differences of overshoot response between the varistors and TVS diodes, under different conditions of risetime and voltage amplitudes, are developed by comparative analyses, and the physical mechanism is also expatiated. The results demonstrate that the response time of both devices depend on the risetime of the injected nanosecond pulse and it increases with the increase of pulse risetime, and TVS diode has the more faster response speed for the same risetime pulses. As the amplitude of injected pulse voltage increases, the thermal accumulation in P-N junction and the breakdown speed increases, which results in a shorter response time. Furthermore, the limited voltage amplitude of varistor is a more drastic oscillation than that of TVS diode. The voltage overshoot phenomenon, in addition, is appearing before the limited voltage stability for both surge protective devices when the fast pulses being injected. The amplitude of overshoot for two typical surge protective devices increases with the injected pulse amplitude increasing, although the limited voltage amplitude is usually determined by its own protective characteristics, the overshoot voltages for different models of one kind of device have nearly the identical amplitude under the same injected pulse. Furthermore, the overshoot voltage of varistor is usually lower than its limited voltage. For TVS diodes, however, the overshoot voltage is higher than its limited voltage and the ratio of the former to the latter increases with the decrease of the limited voltage amplitude, which means that the voltage overshoot phenomenon has a more serious impact on the performance of the low-voltage TVS diode.
Varistors and transient voltage suppressor (TVS) diodes, as two typical surge protective devices, are often used to limit voltage in the high power microwave pulse. To investigate their nanosecond pulse response and provide a scientific basis for the selection of electromagnetic pulse interference protection devices, the experimental measurement were carried out by the way of hundreds of nanoseconds and two nanoseconds risetime pulses injecting directly. Moreover, the differences of overshoot response between the varistors and TVS diodes, under different conditions of risetime and voltage amplitudes, are developed by comparative analyses, and the physical mechanism is also expatiated. The results demonstrate that the response time of both devices depend on the risetime of the injected nanosecond pulse and it increases with the increase of pulse risetime, and TVS diode has the more faster response speed for the same risetime pulses. As the amplitude of injected pulse voltage increases, the thermal accumulation in P-N junction and the breakdown speed increases, which results in a shorter response time. Furthermore, the limited voltage amplitude of varistor is a more drastic oscillation than that of TVS diode. The voltage overshoot phenomenon, in addition, is appearing before the limited voltage stability for both surge protective devices when the fast pulses being injected. The amplitude of overshoot for two typical surge protective devices increases with the injected pulse amplitude increasing, although the limited voltage amplitude is usually determined by its own protective characteristics, the overshoot voltages for different models of one kind of device have nearly the identical amplitude under the same injected pulse. Furthermore, the overshoot voltage of varistor is usually lower than its limited voltage. For TVS diodes, however, the overshoot voltage is higher than its limited voltage and the ratio of the former to the latter increases with the decrease of the limited voltage amplitude, which means that the voltage overshoot phenomenon has a more serious impact on the performance of the low-voltage TVS diode.
2016,
28: 125004.
doi: 10.11884/HPLPB201628.160138
Abstract:
To study conveniently the electromagretic coupling of Primary Test Stand (PTS) with Z pinch load, based on experimental electrical data analysis and full circuit simulations, a simple lumped circuit model (LCM-PTS) was established and the lumped parameters were discussed in detail. The equivalent voltage was obtained by constructing the open circuit voltage at the tri-plate output water transmission line, which could be fitted by a function of 3.3sin2(t/205). The space electrons current loss in the magnetically insulated transmission line was simplified by flow impedance model. Simulations were carried out by coupling the LCM-PTS model with a 0-dimensional dynamic model of Z pinch loads, and the load currents agreed well with the experimental results.
To study conveniently the electromagretic coupling of Primary Test Stand (PTS) with Z pinch load, based on experimental electrical data analysis and full circuit simulations, a simple lumped circuit model (LCM-PTS) was established and the lumped parameters were discussed in detail. The equivalent voltage was obtained by constructing the open circuit voltage at the tri-plate output water transmission line, which could be fitted by a function of 3.3sin2(t/205). The space electrons current loss in the magnetically insulated transmission line was simplified by flow impedance model. Simulations were carried out by coupling the LCM-PTS model with a 0-dimensional dynamic model of Z pinch loads, and the load currents agreed well with the experimental results.
2016,
28: 125005.
doi: 10.11884/HPLPB201628.160157
Abstract:
In order to realize flexible interface setting and high-precision timing control between multi-channel pulse lasers, a multi-channel timing control system was designed based on STM32 and FPGA. This paper mainly introduces the generation of multi-channel nanosecond timing signal based on FPGA and the design of touch panel interface based on ucGUI. The driver circuit was designed using high-speed optical isolation technology and high-speed switch circuit technology, which shortened the rise time of pulse outputs, improved delay precision, driver capability and anti-interference performance. The design ensures that each channel delay can be set with in the range from 5 ns to 10 ms , with minimum step of 5 ns, and precision of the system delay time is less than 1 ns.
In order to realize flexible interface setting and high-precision timing control between multi-channel pulse lasers, a multi-channel timing control system was designed based on STM32 and FPGA. This paper mainly introduces the generation of multi-channel nanosecond timing signal based on FPGA and the design of touch panel interface based on ucGUI. The driver circuit was designed using high-speed optical isolation technology and high-speed switch circuit technology, which shortened the rise time of pulse outputs, improved delay precision, driver capability and anti-interference performance. The design ensures that each channel delay can be set with in the range from 5 ns to 10 ms , with minimum step of 5 ns, and precision of the system delay time is less than 1 ns.
2016,
28: 125101.
doi: 10.11884/HPLPB201628.160096
Abstract:
The key to design magnetic alloy (MA) loaded cavity is to test and research the performance parameter of the MA core. Using the resonant circuits, we have tested the performance parameters of the domestic MA core, including the permeability, Q value and shunt impedance. Test results show that the Q value of the MA core is low while the change caused by frequency is not obvious. The magnetic permeability is high and decreases with frequency increase while the shunt impedance increases with frequency increase. Within the working temperature from 0 ℃ to 100 ℃, the performance parameter of the MA core changes very little. The analysis of the performance test data of the MA core provides important technical indexes for the design of microwave power source and LLRF system.
The key to design magnetic alloy (MA) loaded cavity is to test and research the performance parameter of the MA core. Using the resonant circuits, we have tested the performance parameters of the domestic MA core, including the permeability, Q value and shunt impedance. Test results show that the Q value of the MA core is low while the change caused by frequency is not obvious. The magnetic permeability is high and decreases with frequency increase while the shunt impedance increases with frequency increase. Within the working temperature from 0 ℃ to 100 ℃, the performance parameter of the MA core changes very little. The analysis of the performance test data of the MA core provides important technical indexes for the design of microwave power source and LLRF system.
2016,
28: 125102.
doi: 10.11884/HPLPB201628.160114
Abstract:
The 3.5-cell direct current-superconductive (DC-SRF) photoinjector requires a 1.3 GHz 20 kW continuous wave (CW) power amplifier. The RD of a solid state amplifier (SSA) consisting of 88 unit modules with individual power supplies, which is the first high power (10 kW) CW L-band SSA in China, has been carried out under the cooperation of Peking University and Beijing BBEF Science Technology Co. Ltd.(BBEF). The RF test results show that the main parameters of this SSA reach the designed values. The efficiency is 34% at full output power of 20 kW and the gain is higher than 85 dB. The phase shift and gain vary within 9.5 and 1.6 dB respectively when the output power changes from 1 to 20 kW. It has been put into operation for more than 2000 h. After a brief description of the design, this paper mainly introduces the commissioning process of the SSA and discusses the problem of full reflection.
The 3.5-cell direct current-superconductive (DC-SRF) photoinjector requires a 1.3 GHz 20 kW continuous wave (CW) power amplifier. The RD of a solid state amplifier (SSA) consisting of 88 unit modules with individual power supplies, which is the first high power (10 kW) CW L-band SSA in China, has been carried out under the cooperation of Peking University and Beijing BBEF Science Technology Co. Ltd.(BBEF). The RF test results show that the main parameters of this SSA reach the designed values. The efficiency is 34% at full output power of 20 kW and the gain is higher than 85 dB. The phase shift and gain vary within 9.5 and 1.6 dB respectively when the output power changes from 1 to 20 kW. It has been put into operation for more than 2000 h. After a brief description of the design, this paper mainly introduces the commissioning process of the SSA and discusses the problem of full reflection.
2016,
28: 125103.
doi: 10.11884/HPLPB201628.160122
Abstract:
The interferometer system for transverse beam size measurement was one of the important parts of storage ring diagnostics in Shanghai Synchrotron Radiation Facility (SSRF).The average of multiple lines and curve fitting method was adopted for raw image data processing now, but there were big random errors and system errors when the CCD is not aligned with the double slits. The article discusses the feasibility and the advantages about using primary component analyzing (PCA) method to process the raw image data from the interferometer system. Using MATLAB simulation and two experiments with random noise and rotated CCD, comparing the results errors between PCA raw image data processing and normal average of multiple lines method, it is concluded that the noise could be reduced and the small angle between CCD and double slits could be found out and corrected using PCA methods.
The interferometer system for transverse beam size measurement was one of the important parts of storage ring diagnostics in Shanghai Synchrotron Radiation Facility (SSRF).The average of multiple lines and curve fitting method was adopted for raw image data processing now, but there were big random errors and system errors when the CCD is not aligned with the double slits. The article discusses the feasibility and the advantages about using primary component analyzing (PCA) method to process the raw image data from the interferometer system. Using MATLAB simulation and two experiments with random noise and rotated CCD, comparing the results errors between PCA raw image data processing and normal average of multiple lines method, it is concluded that the noise could be reduced and the small angle between CCD and double slits could be found out and corrected using PCA methods.
2016,
28: 125104.
doi: 10.11884/HPLPB201628.160104
Abstract:
Barrier bucket (BB) is used to enhance the intensity of the beam current by accumulation repeatedly in synchrotron. It can overcome the influence of space-charge effect. For realizing the beam accumulation repeatedly, it needs generating a single-sine voltage pulse in the accelerating cavity. Based on the single-sine waveforms characteristics, conditions and methods for generating barrier voltages are discussed in this paper. The bandwidth requirement of the signal is obtained according to the spectrum analysis of the signal, at the same time the relationship between the output voltage and the input excitation current is determined by using the method of equivalent parallel circuit and the linear time invariant approximation. The bandwidth requirement of the barrier RF signal is at least two times of the single sine frequency. The input excitation current is based on a single sinusoidal signal adding a DC pulse bias(the bias value equals to the Q value of cavity). Based on the results of the analysis, the BB voltage test was carried out on both of the ferrite loaded cavity of the cooling storage experimental ring (CSRe) and the newly developed magnetic alloy cavity,and the test results are discussed.
Barrier bucket (BB) is used to enhance the intensity of the beam current by accumulation repeatedly in synchrotron. It can overcome the influence of space-charge effect. For realizing the beam accumulation repeatedly, it needs generating a single-sine voltage pulse in the accelerating cavity. Based on the single-sine waveforms characteristics, conditions and methods for generating barrier voltages are discussed in this paper. The bandwidth requirement of the signal is obtained according to the spectrum analysis of the signal, at the same time the relationship between the output voltage and the input excitation current is determined by using the method of equivalent parallel circuit and the linear time invariant approximation. The bandwidth requirement of the barrier RF signal is at least two times of the single sine frequency. The input excitation current is based on a single sinusoidal signal adding a DC pulse bias(the bias value equals to the Q value of cavity). Based on the results of the analysis, the BB voltage test was carried out on both of the ferrite loaded cavity of the cooling storage experimental ring (CSRe) and the newly developed magnetic alloy cavity,and the test results are discussed.
2016,
28: 125105.
doi: 10.11884/HPLPB201628.160120
Abstract:
Top-up operation mode of Shanghai Synchrotron Radiation Facility (SSRF) needs the linac to supply a stable, continuous and high quality beam. The principle of an 8-pole strip-line-type beam position monitor (BPM) and measurement of the beam energy spread at low energy transform line from the linac to the booster are described, and a proportion and integration (PI) control algorithm is used to complete the feedback control of beam energy spread, which uses RF (radio frequency) amplitude or phase as the adjusting parameter. A long term stability of the beam energy is realized, which ensures the high rate of the beam injection of the linac.
Top-up operation mode of Shanghai Synchrotron Radiation Facility (SSRF) needs the linac to supply a stable, continuous and high quality beam. The principle of an 8-pole strip-line-type beam position monitor (BPM) and measurement of the beam energy spread at low energy transform line from the linac to the booster are described, and a proportion and integration (PI) control algorithm is used to complete the feedback control of beam energy spread, which uses RF (radio frequency) amplitude or phase as the adjusting parameter. A long term stability of the beam energy is realized, which ensures the high rate of the beam injection of the linac.
2016,
28: 125106.
doi: 10.11884/HPLPB201628.160144
Abstract:
Vibrating wire theory provides a high accuracy alignment method, applying vibrating wire theory to magnets pre-alignment on a girder will greatly increase the alignment accuracy between the magnets. This paper introduces briefly the pre-alignment scheme of magnets on a girder. According to the scheme and the vibrating wire theory, it introduces a scheme of data acquisition and processing for a vibrating wire system. This paper also analyses and solves the key problems including sensor work point alignment, wire current measurement, data acquisition devices selection, magnetic induction intensity calculation and magnetic center calculation. Finally, it presents the experiments of feasibility and accuracy verification.
Vibrating wire theory provides a high accuracy alignment method, applying vibrating wire theory to magnets pre-alignment on a girder will greatly increase the alignment accuracy between the magnets. This paper introduces briefly the pre-alignment scheme of magnets on a girder. According to the scheme and the vibrating wire theory, it introduces a scheme of data acquisition and processing for a vibrating wire system. This paper also analyses and solves the key problems including sensor work point alignment, wire current measurement, data acquisition devices selection, magnetic induction intensity calculation and magnetic center calculation. Finally, it presents the experiments of feasibility and accuracy verification.
2016,
28: 125107.
doi: 10.11884/HPLPB201628.160361
Abstract:
This article mainly describes the interlock protection function design in the cyclotron control system of HIMM (Heavy Ion Medical Machine). Aiming at the interlock requirements of ion source, radio frequency, vacuum, power supply, cooling water and other subsystems, we designed an interlock system based on device+PLC+software structure. This design ensures the normal work of interlock function in case of power down, line connection failure or abnormal data transmission. The reaction time reached milliseconds for hardware interlock and sub-second for software interlock. The whole function was verified in the process of cyclotron testing and ensured the beam tuning of the whole accelerator.
This article mainly describes the interlock protection function design in the cyclotron control system of HIMM (Heavy Ion Medical Machine). Aiming at the interlock requirements of ion source, radio frequency, vacuum, power supply, cooling water and other subsystems, we designed an interlock system based on device+PLC+software structure. This design ensures the normal work of interlock function in case of power down, line connection failure or abnormal data transmission. The reaction time reached milliseconds for hardware interlock and sub-second for software interlock. The whole function was verified in the process of cyclotron testing and ensured the beam tuning of the whole accelerator.
2016,
28: 126001.
doi: 10.11884/HPLPB201628.160115
Abstract:
Neutron stimulated emission computed tomography (NSECT) is a new approach for biological spectroscopy and imaging. Since the gamma-ray photons emitted from stimulated element have energies from 100 keV to about 6 MeV, previous reports have proposed that the projection path can be defined by the neutron beam. In this paper, a good energy resolution method has been applied, whose performance is analysed through simulations. Using signals from a single BGO crystal, it is impossible to achieve good energy resolution for such high-energy photons. But when summing additional signals from adjacent crystals, the energy spectrum becomes much better. Using an energy window with energy resolution of 90 keV, an average intrinsic spatial resolution of 3.938 mm FWHM is obtained.
Neutron stimulated emission computed tomography (NSECT) is a new approach for biological spectroscopy and imaging. Since the gamma-ray photons emitted from stimulated element have energies from 100 keV to about 6 MeV, previous reports have proposed that the projection path can be defined by the neutron beam. In this paper, a good energy resolution method has been applied, whose performance is analysed through simulations. Using signals from a single BGO crystal, it is impossible to achieve good energy resolution for such high-energy photons. But when summing additional signals from adjacent crystals, the energy spectrum becomes much better. Using an energy window with energy resolution of 90 keV, an average intrinsic spatial resolution of 3.938 mm FWHM is obtained.
2016,
28: 126002.
doi: 10.11884/HPLPB201628.160126
Abstract:
For various applications and security considerations of radioactive nuclide, good performance of Compton camera is very important. In this article, the Monte Carlo method is used to simulate the double array type Compton camera, whose scattering detector material is Si and absorption detector material is CZT. By using the projection image reconstruction algorithm for image reconstruction, the maximum likelihood method is adopted to optimize reconstruction results, which effectively improves the resolution of the reconstructed image. When the source-detector distance is 100 mm, after 10 times of maximum likelihood method iterative calculation, the position resolution and angle resolution are 5.1 mm and 7.3 respectively. It is proved that maximum likelihood method can optimize Compton camera source image reconstruction effectively.
For various applications and security considerations of radioactive nuclide, good performance of Compton camera is very important. In this article, the Monte Carlo method is used to simulate the double array type Compton camera, whose scattering detector material is Si and absorption detector material is CZT. By using the projection image reconstruction algorithm for image reconstruction, the maximum likelihood method is adopted to optimize reconstruction results, which effectively improves the resolution of the reconstructed image. When the source-detector distance is 100 mm, after 10 times of maximum likelihood method iterative calculation, the position resolution and angle resolution are 5.1 mm and 7.3 respectively. It is proved that maximum likelihood method can optimize Compton camera source image reconstruction effectively.
2016,
28: 129901.
doi: 10.11884/HPLPB201628.160490
Abstract:
光纤激光是继气体激光、化学激光和固体激光之后的新一代激光技术，是近年来世界各国科学研究的热点领域。制约光纤激光功率提升的主要技术瓶颈是系统集成技术和光纤材料制备技术。目前，我国科研工作者成功掌握了千瓦级光纤激光系统集成技术并实现了产业化，但是所用的光纤激光材料与核心器件还严重依赖进口。相较于比较成熟的系统集成技术，我国光纤激光材料的科学研究和产业化进程相对滞后，尚无法提供成熟稳定的有源光纤产品。 2016年6月，中国工程物理研究院激光聚变研究中心的研究人员经过近三年科研攻关，成功研发了30/900规格（纤芯30 m/包层900 m）镱掺杂铝磷硅（Yb-APS）三元体系激光光纤并实现了6.03 kW最高功率输出，在5 kW功率水平下可长期稳定工作。光纤激光材料综合测试平台采用了传统的1+1型MOPA放大结构（即信号种子源与一级主放）：信号光种子源的功率为40 W，光束质量M2=1.1；第二级MOPA放大级使用的976 nm LD泵浦光总功率9.95 kW，经过CPS功率剥离器激光净化处理后，最终安全地实现了6.03 kW最大功率输出。如图1所示，最高输出功率时斜率效率为61.25%，源于1∶30的芯包比和20 m以上的光纤使用长度；激光输出光谱中心波长1080 nm，3 dB带宽为1.89 nm，受激拉曼抑制比＞15 dB；5 kW稳定工作时，光束质量M2=2.38，未发现光子暗化效应。中物院激光聚变研究中心所研制的镱掺杂铝磷硅三元体系有源光纤(30/900 Yb-APS fiber)成功实现了6.03 kW激光输出，是我国高功率光纤激光材料研究领域的重要进步，为制备低损耗、高掺杂、高吸收、高增益、无光子暗化效应的商业激光光纤产品奠定了坚实的技术基础。
