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RSS2013 Vol. 25, No. 11
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2013,
25: 2777-2779.
doi: 10.3788/HPLPB20132511.2777
Abstract:
The paper presents the results of non-thermal transient plasma and thermal transient plasma ignition for delay reduction of quiescent ethene-air mixture in a cylinder combustion chamber. The non-thermal transient plasma and thermal transient plasma were produced by nanosecond high voltage pulse discharge. The results from the experiments indicated that electrical energy consumption of non-thermal transient plasma was lower than that of thermal transient plasma. Non-thermal transient plasma ignition has demonstrated reductions in ignition delay compared to thermal transient plasma ignition.
The paper presents the results of non-thermal transient plasma and thermal transient plasma ignition for delay reduction of quiescent ethene-air mixture in a cylinder combustion chamber. The non-thermal transient plasma and thermal transient plasma were produced by nanosecond high voltage pulse discharge. The results from the experiments indicated that electrical energy consumption of non-thermal transient plasma was lower than that of thermal transient plasma. Non-thermal transient plasma ignition has demonstrated reductions in ignition delay compared to thermal transient plasma ignition.
2013,
25: 2780-2784.
doi: 10.3788/HPLPB20132511.2780
Abstract:
The beam parameters measurement is the most important work for the study of linear induction accelerator(LIA). The beam parameters are important to evaluate the character of the beam. The demands of beam parameters measurement are improving while the development of accelerator is improving. The measurement difficulty feature higher time-resolved ability, higher spatial resolution, larger dynamic range and higher intuitionistic view data. The measurement technology of beam spot, beam emittance, beam energy have been developed for the past several years. Some high performance equipments such as high speed framing camera are developed recently. Under this condition, the relative integrated optical measurement and diagnostic system for the beam parameters is developed based on several principles. The system features time-resolved ability of up to 2 ns, high sensitivity and large dynamic range. The processing program is compiled for the data process and the local real-time process is reached. The measurement and diagnostic system has provided full and accurate data for the debug work and has been put into applications.
The beam parameters measurement is the most important work for the study of linear induction accelerator(LIA). The beam parameters are important to evaluate the character of the beam. The demands of beam parameters measurement are improving while the development of accelerator is improving. The measurement difficulty feature higher time-resolved ability, higher spatial resolution, larger dynamic range and higher intuitionistic view data. The measurement technology of beam spot, beam emittance, beam energy have been developed for the past several years. Some high performance equipments such as high speed framing camera are developed recently. Under this condition, the relative integrated optical measurement and diagnostic system for the beam parameters is developed based on several principles. The system features time-resolved ability of up to 2 ns, high sensitivity and large dynamic range. The processing program is compiled for the data process and the local real-time process is reached. The measurement and diagnostic system has provided full and accurate data for the debug work and has been put into applications.
2013,
25: 2785-2787.
doi: 10.3788/HPLPB20132511.2785
Abstract:
We reported the experiments of 1137 nm Yb-doped fiber laser, which was pumped by 976 nm laser diode and 1040 nm fiber laser respectively. Both of the output powers of the experiments were over hundred-milliwatt. The laser was a linear cavity. The reflectivities of the high reflectivity fiber Bragg grating and low reflectivity output coupler were 99.6% and 39.7% respectively. The gain media was an 8-meters-long Yb-doped fiber with a core diameter of 5 m. When the power of the 976 nm laser diode was 912 mW, the output power of 1137 nm laser reached to 182 mW corresponding to the slope efficiency of 28.5%. When pumped by 1.59 W 1040 nm fiber laser, a 278 mW 1137 nm laser power was obtained with a slope efficiency of 25%. We also compared the differences of these two pumping methods.
We reported the experiments of 1137 nm Yb-doped fiber laser, which was pumped by 976 nm laser diode and 1040 nm fiber laser respectively. Both of the output powers of the experiments were over hundred-milliwatt. The laser was a linear cavity. The reflectivities of the high reflectivity fiber Bragg grating and low reflectivity output coupler were 99.6% and 39.7% respectively. The gain media was an 8-meters-long Yb-doped fiber with a core diameter of 5 m. When the power of the 976 nm laser diode was 912 mW, the output power of 1137 nm laser reached to 182 mW corresponding to the slope efficiency of 28.5%. When pumped by 1.59 W 1040 nm fiber laser, a 278 mW 1137 nm laser power was obtained with a slope efficiency of 25%. We also compared the differences of these two pumping methods.
2013,
25: 2788-2792.
doi: 10.3788/HPLPB20132511.2788
Abstract:
Based on Mach-Zehnder interferometer placed in electro-optic crystal, and using the principles of double beam interference of the Mach-Zehnder interferometer and the linear electro-optic effect of the crystal, a new method of scanning filtering for improving the signal to noise ratio (SNR) of chirped pulse was proposed. The spectral characteristics of the scanning filter were analyzed quantitatively. The effects of the delay time of the prepulse on the output SNR were analyzed. Moreover, the effects of the control parameters of the electro-optic crystal voltage on the SNR were discussed in detail. The results show that the variation of controlling voltage and the delay time of the prepulse have significant impact on the filtering effect and that the SNR of the chirp pulse can be improved nearly two magnitudes by using the scanning filtering method and the transmittance of signal can be as high as 95% or more.
Based on Mach-Zehnder interferometer placed in electro-optic crystal, and using the principles of double beam interference of the Mach-Zehnder interferometer and the linear electro-optic effect of the crystal, a new method of scanning filtering for improving the signal to noise ratio (SNR) of chirped pulse was proposed. The spectral characteristics of the scanning filter were analyzed quantitatively. The effects of the delay time of the prepulse on the output SNR were analyzed. Moreover, the effects of the control parameters of the electro-optic crystal voltage on the SNR were discussed in detail. The results show that the variation of controlling voltage and the delay time of the prepulse have significant impact on the filtering effect and that the SNR of the chirp pulse can be improved nearly two magnitudes by using the scanning filtering method and the transmittance of signal can be as high as 95% or more.
2013,
25: 2793-2798.
doi: 10.3788/HPLPB20132511.2793
Abstract:
The self-focusing transmission , filamentation, breakdown of intense laser pulses in water, and sound pressure waves generated during breakdown become a hot topic of intense laser pulse application research. Ionization generated bubbles compress the surrounding water bodies, which produces sound pressure waves underwater. Based on the previous theory, a dynamic model is developed, in which the gas content, viscosity coefficient and the surface tension coefficient are considered. The collapse process of double bubbles is also modeled, which could be applied to calculate the bubble radius and generated sound pressure waves. These theories are amended by introducing varying factors of water characters at different temperatures. Calculation results show that the bubbles shrink more violently and generate higher sound pressure waves when water temperature is higher. For double bubbles, higher sound pressure waves will be generated when the two bubbles are closer. The minimum collapse radiuses are varying linearly along with the distances between bubbles, and the generated maximum sound pressures are monotonically increasing.
The self-focusing transmission , filamentation, breakdown of intense laser pulses in water, and sound pressure waves generated during breakdown become a hot topic of intense laser pulse application research. Ionization generated bubbles compress the surrounding water bodies, which produces sound pressure waves underwater. Based on the previous theory, a dynamic model is developed, in which the gas content, viscosity coefficient and the surface tension coefficient are considered. The collapse process of double bubbles is also modeled, which could be applied to calculate the bubble radius and generated sound pressure waves. These theories are amended by introducing varying factors of water characters at different temperatures. Calculation results show that the bubbles shrink more violently and generate higher sound pressure waves when water temperature is higher. For double bubbles, higher sound pressure waves will be generated when the two bubbles are closer. The minimum collapse radiuses are varying linearly along with the distances between bubbles, and the generated maximum sound pressures are monotonically increasing.
2013,
25: 2799-2802.
doi: 10.3788/HPLPB20132511.2799
Abstract:
We designed a phase transition cooling system with thermal energy storage solutions, and designed a spray phase transition cooler and microchannel phase transition coolers that meet the need of heat dispersion for high power diode laser. By use of NH3 as cryogen, the cooler with porous heat exchanging surface achieved a heat flux density up to 511 W/cm2 while the surface temperature was 37 ℃. A back cooling phase transition microchannel cooler and a thin piece shaped phase transition microchannel cooler had been designed by using throttle evaporation principle. The dispersed heat flux density of 550 W/cm2 and 270 W/cm2 was proved by the back cooling phase transition cooler with NH3 and R124 as cryogen, respectively. The diode laser modules with power of QCW 3 kW and CW 100 W were packaged based on phase transition cooler with R124 as cryogen.
We designed a phase transition cooling system with thermal energy storage solutions, and designed a spray phase transition cooler and microchannel phase transition coolers that meet the need of heat dispersion for high power diode laser. By use of NH3 as cryogen, the cooler with porous heat exchanging surface achieved a heat flux density up to 511 W/cm2 while the surface temperature was 37 ℃. A back cooling phase transition microchannel cooler and a thin piece shaped phase transition microchannel cooler had been designed by using throttle evaporation principle. The dispersed heat flux density of 550 W/cm2 and 270 W/cm2 was proved by the back cooling phase transition cooler with NH3 and R124 as cryogen, respectively. The diode laser modules with power of QCW 3 kW and CW 100 W were packaged based on phase transition cooler with R124 as cryogen.
2013,
25: 2803-2806.
doi: 10.3788/HPLPB20132511.2803
Abstract:
Based on the Fox-Li iterative method, a planar ring cavity is modeled with optical simulation software GLAD, to study the effect of mirror tilt on the oscillation mode. The mode intensity distribution, the peak intensity position and the loss of the cavity are presented in the condition of different mirror tilts in two directions. Results show that mirror tilts result in the resonator mode distortion. With the cavity mirror tilt increasing, the loss of the cavity increases and the peak intensity moves to the edge of the mirror. Mirror tilts in the direction perpendicular to the cavity surface have more effect on the oscillation mode than in the direction parallel to the cavity surface.
Based on the Fox-Li iterative method, a planar ring cavity is modeled with optical simulation software GLAD, to study the effect of mirror tilt on the oscillation mode. The mode intensity distribution, the peak intensity position and the loss of the cavity are presented in the condition of different mirror tilts in two directions. Results show that mirror tilts result in the resonator mode distortion. With the cavity mirror tilt increasing, the loss of the cavity increases and the peak intensity moves to the edge of the mirror. Mirror tilts in the direction perpendicular to the cavity surface have more effect on the oscillation mode than in the direction parallel to the cavity surface.
2013,
25: 2807-2810.
doi: 10.3788/HPLPB20132511.2807
Abstract:
100 MHz high repetition rate lasers are experimentally realized with narrow bandwidth and tunable wavelength. A single-frequency CW seed source is modulated by an electro-optical (EO) modulator to achieve pulsed lasers. The pulsed laser is amplified by a fiber amplifier and then by a two-stage solid-state laser amplifier. The maximum output power is 31.9 W in fundamental mode. The M2 factor is less than 1.5. The pulse width is 1 ns with a repetition rate of 100 MHz. The line-width of the output laser is less than 0.8 GHz. The experimental results verify the validity of method to achieve high repetition rate lasers. The combined amplifier with both fiber amplifier and solid-state laser amplifier is approved to be effective to achieve power amplification.
100 MHz high repetition rate lasers are experimentally realized with narrow bandwidth and tunable wavelength. A single-frequency CW seed source is modulated by an electro-optical (EO) modulator to achieve pulsed lasers. The pulsed laser is amplified by a fiber amplifier and then by a two-stage solid-state laser amplifier. The maximum output power is 31.9 W in fundamental mode. The M2 factor is less than 1.5. The pulse width is 1 ns with a repetition rate of 100 MHz. The line-width of the output laser is less than 0.8 GHz. The experimental results verify the validity of method to achieve high repetition rate lasers. The combined amplifier with both fiber amplifier and solid-state laser amplifier is approved to be effective to achieve power amplification.
2013,
25: 2811-2815.
doi: 10.3788/HPLPB20132511.2811
Abstract:
For the problem of small infrared target detection with complex background interference and noises, an improved dim small infrared target detection algorithm based on nonsubsampled Contourlet transform (NSCT) is put forward. Firstly, the infrared image with dim small target is preprocessed. Then, the NSCT is implemented, by combining the improved nonlinear map function and energy cross fusion to suppress the background clutters. Finally, threshold segmentation using the Otsu algorithm is used to isolate the dim small infrared target.compared with the similar small target detection algorithm, the method can effectively detect the small infrared target.
For the problem of small infrared target detection with complex background interference and noises, an improved dim small infrared target detection algorithm based on nonsubsampled Contourlet transform (NSCT) is put forward. Firstly, the infrared image with dim small target is preprocessed. Then, the NSCT is implemented, by combining the improved nonlinear map function and energy cross fusion to suppress the background clutters. Finally, threshold segmentation using the Otsu algorithm is used to isolate the dim small infrared target.compared with the similar small target detection algorithm, the method can effectively detect the small infrared target.
2013,
25: 2816-2820.
doi: 10.3788/HPLPB20132511.2816
Abstract:
In order to realize the spot homogenization and beam shaping of high-power laser diode stack, a homogenization system is proposed based on double cylindrical lenses in the slow axis direction. The double cylindrical lenses are used to collimate beams of high fill factor laser diodes in the slow axis direction, for decreasing the numerical aperture of microlenses in the imaging multi-aperture integrator and reducing the homogenization system volume. Through three limiting conditions, the parameter ranges of the double cylindrical lenses are determined. By analyzing the effect of aberration on slow axis collimation, the double cylindrical lenses are optimized to achieve the remaining divergence angle of 1.74. With the imaging multi-aperture beam integrator, the homogenization system for laser diode stack beams is designed and verified through experimental test. The experimental results show that the size of central spot on the target plane is about 6 mm6 mm and the spot inhomogeneity reaches to 8.11%.
In order to realize the spot homogenization and beam shaping of high-power laser diode stack, a homogenization system is proposed based on double cylindrical lenses in the slow axis direction. The double cylindrical lenses are used to collimate beams of high fill factor laser diodes in the slow axis direction, for decreasing the numerical aperture of microlenses in the imaging multi-aperture integrator and reducing the homogenization system volume. Through three limiting conditions, the parameter ranges of the double cylindrical lenses are determined. By analyzing the effect of aberration on slow axis collimation, the double cylindrical lenses are optimized to achieve the remaining divergence angle of 1.74. With the imaging multi-aperture beam integrator, the homogenization system for laser diode stack beams is designed and verified through experimental test. The experimental results show that the size of central spot on the target plane is about 6 mm6 mm and the spot inhomogeneity reaches to 8.11%.
2013,
25: 2821-2825.
doi: 10.3788/HPLPB20132511.2821
Abstract:
Laser induced polarization spectroscopy (LIPS) and laser induced fluorescence (LIF) measurement techniques have been employed simultaneously to diagnose CH4/AIR flame. Fluorescence spectra and polarization spectra of OH were measured at different height in the center of CH4/AIR flame at the same time, and the distributions of temperature and OH number density were obtained. The collection efficiency of fluorescence affected by the surface of the burner was analysed, the experimental data obtained by two techniques were compared, and OH number density distribution law along the height direction was acquired. The experimental results indicate the feasibility of combining these two techniques for combustion diagnostics, and the experimental data acquired by the two techniques agree well with each other, with a discrepancy within 5% for OH density and a discrepancy within 8% for temperature.
Laser induced polarization spectroscopy (LIPS) and laser induced fluorescence (LIF) measurement techniques have been employed simultaneously to diagnose CH4/AIR flame. Fluorescence spectra and polarization spectra of OH were measured at different height in the center of CH4/AIR flame at the same time, and the distributions of temperature and OH number density were obtained. The collection efficiency of fluorescence affected by the surface of the burner was analysed, the experimental data obtained by two techniques were compared, and OH number density distribution law along the height direction was acquired. The experimental results indicate the feasibility of combining these two techniques for combustion diagnostics, and the experimental data acquired by the two techniques agree well with each other, with a discrepancy within 5% for OH density and a discrepancy within 8% for temperature.
2013,
25: 2826-2830.
doi: 10.3788/HPLPB20132511.2826
Abstract:
An in situ multi-beam optical stress sensor system was used to monitor and analyze the force per unit width and stress evolution during and after the deposition of magnetron-sputtered Si and SiNx films. A rapid stress relaxation, as well as a recovery, was observed in both films. Stress in Si films was reversible, while partial reversible in SiNx films. Physical adsorption and desorption are the main factors responsible for the stress relaxation and recovery. The non-reversible stress component results from chemical adsorption. And a model based on adsorption is proposed to explain the stress relaxation.
An in situ multi-beam optical stress sensor system was used to monitor and analyze the force per unit width and stress evolution during and after the deposition of magnetron-sputtered Si and SiNx films. A rapid stress relaxation, as well as a recovery, was observed in both films. Stress in Si films was reversible, while partial reversible in SiNx films. Physical adsorption and desorption are the main factors responsible for the stress relaxation and recovery. The non-reversible stress component results from chemical adsorption. And a model based on adsorption is proposed to explain the stress relaxation.
2013,
25: 2831-2835.
doi: 10.3788/HPLPB20132511.2831
Abstract:
A high efficiency, composite and air cooling LD end-pumped Nd:YVO4, acousto-optic Q-switched, and LBO(critical phase matching) intracavity doubled all-solid-state green laser is reported. By analyzing the absorption characteristics, with different polarized light pump, the uniformity of the crystal absorption could be significantly improved when the gain medium was pumped with partially polarized light. The fundamental wave distortion could be improved and the conversion efficiency could be enhanced. When the incident pump power was 33 W, the repetition rate of the AO-Q switch is 20 kHz, a 1064 nm fundamental frequency laser with an output power of 15 W and a pulse width of 23.96 ns was obtained. The output power of 532 nm green laser was 11.2 W. The optical to optical conversion efficiency from diode to green and from IR to green laser were about 34% and 74.6%. The output power instability was 0.512 2% at the output power of 10 W, The M2 beam quality factor was 1.2 in the horizontal direction and 1.1 in the vertical direction .
A high efficiency, composite and air cooling LD end-pumped Nd:YVO4, acousto-optic Q-switched, and LBO(critical phase matching) intracavity doubled all-solid-state green laser is reported. By analyzing the absorption characteristics, with different polarized light pump, the uniformity of the crystal absorption could be significantly improved when the gain medium was pumped with partially polarized light. The fundamental wave distortion could be improved and the conversion efficiency could be enhanced. When the incident pump power was 33 W, the repetition rate of the AO-Q switch is 20 kHz, a 1064 nm fundamental frequency laser with an output power of 15 W and a pulse width of 23.96 ns was obtained. The output power of 532 nm green laser was 11.2 W. The optical to optical conversion efficiency from diode to green and from IR to green laser were about 34% and 74.6%. The output power instability was 0.512 2% at the output power of 10 W, The M2 beam quality factor was 1.2 in the horizontal direction and 1.1 in the vertical direction .
2013,
25: 2836-2840.
doi: 10.3788/HPLPB20132511.2836
Abstract:
A model was developed for the description of inclusion-induced damage in fused silica by nanosecond-pulse laser at 355 nm. We calculated the temperature of impurity particles with their sizes increasing, and obtained the correlation between the critical fluence and particle radius through Mie theory and heat equation. Moreover, the size at which fused silica damage could be induced easily was discussed for each particle. We got the curves of laser damage probability for samples from the results of damage tests at last. Both the calculation and the experiment show that, by absorbing the energy of laser, with the particle radius increasing, the temperature in particle edge increases first and then decreases. Hence, only a certain range of particles can initiate damage of fused silica. The particles whose radius corresponds to critical fluence most likely cause breakdown of fused silica. The probability of damage on the fused silica sample etched decreases as its impurity density at surface decreases, thus improving the damage threshold of the fused silica.
A model was developed for the description of inclusion-induced damage in fused silica by nanosecond-pulse laser at 355 nm. We calculated the temperature of impurity particles with their sizes increasing, and obtained the correlation between the critical fluence and particle radius through Mie theory and heat equation. Moreover, the size at which fused silica damage could be induced easily was discussed for each particle. We got the curves of laser damage probability for samples from the results of damage tests at last. Both the calculation and the experiment show that, by absorbing the energy of laser, with the particle radius increasing, the temperature in particle edge increases first and then decreases. Hence, only a certain range of particles can initiate damage of fused silica. The particles whose radius corresponds to critical fluence most likely cause breakdown of fused silica. The probability of damage on the fused silica sample etched decreases as its impurity density at surface decreases, thus improving the damage threshold of the fused silica.
2013,
25: 2841-2845.
doi: 10.3788/HPLPB20132511.2841
Abstract:
Systematic error is a part of error sources in atmospheric CO2 high precision retrieval, such as the effect of precision deficiency of temperature profile, pressure profile, H2O and atmospheric layers. This error is hard to overcome only using CO2 band, however, it is nearly independent of wavelength of radiation and can be corrected by other bands. Simulations indicate that O2 band can correct CO2 retrieval error largely. GOSAT data observing the Great Xingan Mountains were used to retrieve atmospheric CO2 and the error of CO2 retrieval indeed decreased by O2 correction obviously.
Systematic error is a part of error sources in atmospheric CO2 high precision retrieval, such as the effect of precision deficiency of temperature profile, pressure profile, H2O and atmospheric layers. This error is hard to overcome only using CO2 band, however, it is nearly independent of wavelength of radiation and can be corrected by other bands. Simulations indicate that O2 band can correct CO2 retrieval error largely. GOSAT data observing the Great Xingan Mountains were used to retrieve atmospheric CO2 and the error of CO2 retrieval indeed decreased by O2 correction obviously.
2013,
25: 2846-2850.
doi: 10.3788/HPLPB20132511.2846
Abstract:
Based on the principle of polarization modulation and optical interference, a microwave photonic filter with positive coefficients and negative coefficients is proposed and an experimental model is set up to verify the feasibility of the project design. With polarization modulation and the polarization property of light, it is achieved that the carrier and the first order sidebands are in two orthogonal polarization directions. Then, the phase shift is introduced to the carrier and the first order sidebands by adjusting the bias voltage of the polarization modulator. With the optical interference effect between the two orthogonal polarization lights in the fast and slow axes of the polarization maintaining fiber when they are in the same polarization state, a microwave photonic filter is achieved with negative coefficients or positive coefficients when the phase difference is 0 or 90. Finally, the frequency response of the filter with a frequency range between 0 GHz and 15 GHz is measured and verified.
Based on the principle of polarization modulation and optical interference, a microwave photonic filter with positive coefficients and negative coefficients is proposed and an experimental model is set up to verify the feasibility of the project design. With polarization modulation and the polarization property of light, it is achieved that the carrier and the first order sidebands are in two orthogonal polarization directions. Then, the phase shift is introduced to the carrier and the first order sidebands by adjusting the bias voltage of the polarization modulator. With the optical interference effect between the two orthogonal polarization lights in the fast and slow axes of the polarization maintaining fiber when they are in the same polarization state, a microwave photonic filter is achieved with negative coefficients or positive coefficients when the phase difference is 0 or 90. Finally, the frequency response of the filter with a frequency range between 0 GHz and 15 GHz is measured and verified.
2013,
25: 2851-2855.
doi: 10.3788/HPLPB20132511.2851
Abstract:
This article expatiated the theory of the thermal-structural-optical (TSO) integrated analysis and interface polynomial. The integrated analysis method was applied to the laser optical system. First of all, the thermal analysis and structure analysis of the optical system were analyzed by FEA software. Then the analyzed data were picked up and made Zernike surface fitting by software. Finally, the influence of the thermal deformation on the beam quality was analyzed by optical software. The results show that the integrated analysis can analyze the influence of optical mirror thermal deformation, and can guide optical system design in the laser optical system.
This article expatiated the theory of the thermal-structural-optical (TSO) integrated analysis and interface polynomial. The integrated analysis method was applied to the laser optical system. First of all, the thermal analysis and structure analysis of the optical system were analyzed by FEA software. Then the analyzed data were picked up and made Zernike surface fitting by software. Finally, the influence of the thermal deformation on the beam quality was analyzed by optical software. The results show that the integrated analysis can analyze the influence of optical mirror thermal deformation, and can guide optical system design in the laser optical system.
2013,
25: 2856-2860.
doi: 10.3788/HPLPB20132511.2856
Abstract:
By using synchronous powder feeding system, Fe-based cladding layers reinforced with in-situ TiVC2 particles were synthesized on 42CrMo roller by laser cladding the mixture powders of ferrotitanium, ferrovanadium and graphite. The cladding layers have good forming and metallurgical bonding with the substrate, without porosity and cracks. The microstructure and properties of the cladding layers were investigated by means of X-ray diffractometry (XRD), electron probe micro-analyzer (EPMA), microhardness tester and electrochemical workstation. The results show that the carbides in cladding layers are TiVC2 with a size of 0.5~ 2 m and these polygonal carbides distribute evenly in cladding layers. These carbides have two different nucleation mechanisms: the heterogeneous nucleation on alumina and the carbide spontaneous nucleation. With the increasing of Ti-VC in alloy powders, the hardness of cladding layers does not increase linearly, and the corrosion resistance of cladding layers decreases gradually.
By using synchronous powder feeding system, Fe-based cladding layers reinforced with in-situ TiVC2 particles were synthesized on 42CrMo roller by laser cladding the mixture powders of ferrotitanium, ferrovanadium and graphite. The cladding layers have good forming and metallurgical bonding with the substrate, without porosity and cracks. The microstructure and properties of the cladding layers were investigated by means of X-ray diffractometry (XRD), electron probe micro-analyzer (EPMA), microhardness tester and electrochemical workstation. The results show that the carbides in cladding layers are TiVC2 with a size of 0.5~ 2 m and these polygonal carbides distribute evenly in cladding layers. These carbides have two different nucleation mechanisms: the heterogeneous nucleation on alumina and the carbide spontaneous nucleation. With the increasing of Ti-VC in alloy powders, the hardness of cladding layers does not increase linearly, and the corrosion resistance of cladding layers decreases gradually.
2013,
25: 2861-2864.
doi: 10.3788/HPLPB20132511.2861
Abstract:
With femtosecond laser pulse shaping technique, the coherent control of non-resonant two-photon transition in a molecular system (perylene dissolved in chloroform solution) is studied theoretically and experimentally. The femtosecond pulse is shaped with simple phase patterns (cosinusoidal and phase step-function shapes) and it is found that the two-photon transition probability in molecular systems can be reduced but cannot be eliminated. Coherent control of non-resonant two-photon transition in a molecular system is correlated with both the laser field and the molecular absorption bandwidth. In contrast with atomic system, control efficiency of two-photon transition in molecular systems is reduced.
With femtosecond laser pulse shaping technique, the coherent control of non-resonant two-photon transition in a molecular system (perylene dissolved in chloroform solution) is studied theoretically and experimentally. The femtosecond pulse is shaped with simple phase patterns (cosinusoidal and phase step-function shapes) and it is found that the two-photon transition probability in molecular systems can be reduced but cannot be eliminated. Coherent control of non-resonant two-photon transition in a molecular system is correlated with both the laser field and the molecular absorption bandwidth. In contrast with atomic system, control efficiency of two-photon transition in molecular systems is reduced.
2013,
25: 2865-2868.
doi: 10.3788/HPLPB20132511.2865
Abstract:
A self-developed miniaturized stress loading system equipped with residual stress neutron diffractometer can actualize in situ measurement of polycrystalline material. It makes possible further acquirement about phase, texture and stress evolution within material and the building of a material macro constitutive model based on micromechanism. This system utilizes servo motor to provide motive power, and chooses 7050 aluminum alloy material to fabricate mechanical structure, whose tensile strength can reach up to 10 kN and the move speed can be adjusted between 1 m/s and 1 mm/s. The S-type sensor used in the system will be deformed when it receives force and exports voltage signals, which will be dealt with by PLC program, and then the relationship between sample stress and strain can be obtained. The results obtained by 10 kN in-situ stretcher were in close agreement with the stress-strain profiles obtained by Instron 5967 stretcher on the same type steel samples.
A self-developed miniaturized stress loading system equipped with residual stress neutron diffractometer can actualize in situ measurement of polycrystalline material. It makes possible further acquirement about phase, texture and stress evolution within material and the building of a material macro constitutive model based on micromechanism. This system utilizes servo motor to provide motive power, and chooses 7050 aluminum alloy material to fabricate mechanical structure, whose tensile strength can reach up to 10 kN and the move speed can be adjusted between 1 m/s and 1 mm/s. The S-type sensor used in the system will be deformed when it receives force and exports voltage signals, which will be dealt with by PLC program, and then the relationship between sample stress and strain can be obtained. The results obtained by 10 kN in-situ stretcher were in close agreement with the stress-strain profiles obtained by Instron 5967 stretcher on the same type steel samples.
2013,
25: 2869-2872.
doi: 10.3788/HPLPB20132511.2869
Abstract:
A novel liquid-level sensor based on a chirped-fiber Bragg grating (CFBG) is proposed，It is mainly constituted of a rectangular cantilever beam sensing mechanism and a fiber optic spectrometer. The expression of relationship between the liquid-level and the bandwidth of the reflection spectra of CFBG is derived. The liquid-level can be obtained by measuring the bandwidth of the reflection spectral of CFBG. The experimental results show that the reflection spectrum bandwidth of a CFBG is insensitive to temperature changes within the measuring range, and a good linear relationship of the bandwidth of the reflection spectrum with the measured liquid-level is obtained.
A novel liquid-level sensor based on a chirped-fiber Bragg grating (CFBG) is proposed，It is mainly constituted of a rectangular cantilever beam sensing mechanism and a fiber optic spectrometer. The expression of relationship between the liquid-level and the bandwidth of the reflection spectra of CFBG is derived. The liquid-level can be obtained by measuring the bandwidth of the reflection spectral of CFBG. The experimental results show that the reflection spectrum bandwidth of a CFBG is insensitive to temperature changes within the measuring range, and a good linear relationship of the bandwidth of the reflection spectrum with the measured liquid-level is obtained.
2013,
25: 2873-2876.
doi: 10.3788/HPLPB20132511.2873
Abstract:
To improve the forming performance of low density polymer foams and to meet the requirement of ICF physical experiments, the forming control of low density polymer foams was studied using thermally induced phase-inversion technique combined with in situ moulding or machining. The results indicate that the fine structure and homogeneity of the foam were preserved by quenching the liquid gel to liquid nitrogen under appropriate nitrogen pressure, and after the solvents being released, the resulted PMP foams had higher strength, more uniform microstrucure and finer pore size. By using in situ moulding or machining, precision forming control of low density PMP foams could be achieved.
To improve the forming performance of low density polymer foams and to meet the requirement of ICF physical experiments, the forming control of low density polymer foams was studied using thermally induced phase-inversion technique combined with in situ moulding or machining. The results indicate that the fine structure and homogeneity of the foam were preserved by quenching the liquid gel to liquid nitrogen under appropriate nitrogen pressure, and after the solvents being released, the resulted PMP foams had higher strength, more uniform microstrucure and finer pore size. By using in situ moulding or machining, precision forming control of low density PMP foams could be achieved.
2013,
25: 2877-2881.
doi: 10.3788/HPLPB20132511.2877
Abstract:
An arbitrary Rogowski coil expression was deduced in this paper. Using high permeability magnetic core and adding turns of the coil, the Rogowski coil was designed, which could measure the low current with slow-rising edge. And the electron-beam signal was obtained by the Rogowski coil. Using the deduced expression of arbitrary Rogowski coil, the current waveforms with low frequency and high frequency were gained. The results show that beam oscillation exists in this electron-beam plasma system, and the oscillation amplitude reaches 12%.
An arbitrary Rogowski coil expression was deduced in this paper. Using high permeability magnetic core and adding turns of the coil, the Rogowski coil was designed, which could measure the low current with slow-rising edge. And the electron-beam signal was obtained by the Rogowski coil. Using the deduced expression of arbitrary Rogowski coil, the current waveforms with low frequency and high frequency were gained. The results show that beam oscillation exists in this electron-beam plasma system, and the oscillation amplitude reaches 12%.
2013,
25: 2882-2886.
doi: 10.3788/HPLPB20132511.2882
Abstract:
The dynamic process of nanosecond laser induced damage of fused silicas input-surface, output-surface and bulk in air was investigated by ultrafast time-resolved shadowgraphs. The comparison and analysis of the damage mechanisms of the input-surface, output-surface and bulk were performed. On the input-surface, the generation and development process of plasma and shock wave were observed in air and materials, three stress waves were observed in materials under the subnanosecond laser, and the bulk damage was observed near the input-surface. On the output-surface, the images of material ablation, explosive phase change and shock waves were obtained. In the bulk, the results show that both the self-focusing and the absorption of point defect are answerable for the damage. However, the damage beginning due to the absorption of point defect maybe has temporal difference.
The dynamic process of nanosecond laser induced damage of fused silicas input-surface, output-surface and bulk in air was investigated by ultrafast time-resolved shadowgraphs. The comparison and analysis of the damage mechanisms of the input-surface, output-surface and bulk were performed. On the input-surface, the generation and development process of plasma and shock wave were observed in air and materials, three stress waves were observed in materials under the subnanosecond laser, and the bulk damage was observed near the input-surface. On the output-surface, the images of material ablation, explosive phase change and shock waves were obtained. In the bulk, the results show that both the self-focusing and the absorption of point defect are answerable for the damage. However, the damage beginning due to the absorption of point defect maybe has temporal difference.
2013,
25: 2887-2890.
doi: 10.3788/HPLPB20132511.2887
Abstract:
It is important to reduce the capsule preheating from gold M-band emission in inertial confinement fusion experiments. A flat-response X-ray detector consisted of particular compound filters and an X-ray diode was adopted to measure the evolution of gold M-band X-ray from different directions from laser entrance hole. The spectral response of detector is not exactly flat on gold M band, which will introduce uncertainty into the calculation. Thus, a calibration result was given that flatness degree of the spectral response was better than 10%. Less M-band energy was observed with the detectors with larger observation angles with respect to the hohlraum axis. Higher energy conversion efficiency of laser to M-band x-ray was observed in R-T hohlraum experiments than that in large hohlraum.
It is important to reduce the capsule preheating from gold M-band emission in inertial confinement fusion experiments. A flat-response X-ray detector consisted of particular compound filters and an X-ray diode was adopted to measure the evolution of gold M-band X-ray from different directions from laser entrance hole. The spectral response of detector is not exactly flat on gold M band, which will introduce uncertainty into the calculation. Thus, a calibration result was given that flatness degree of the spectral response was better than 10%. Less M-band energy was observed with the detectors with larger observation angles with respect to the hohlraum axis. Higher energy conversion efficiency of laser to M-band x-ray was observed in R-T hohlraum experiments than that in large hohlraum.
2013,
25: 2891-2894.
doi: 10.3788/HPLPB20132511.2891
Abstract:
The pulse shapes of loading pressure and driven laser were deduced based on compression isentrope of condensed matter, and the ramp compression simulations of aluminum were performed by hydrodynamic code MULTI. The process of the ramp compression is described with the following parameters: temperature, pressure, density, particle velocity and entropy production. Results show that the entropy production of the ramp compression process is small. This work can provide important supports for laser-driven ramp compression experiments in near future.
The pulse shapes of loading pressure and driven laser were deduced based on compression isentrope of condensed matter, and the ramp compression simulations of aluminum were performed by hydrodynamic code MULTI. The process of the ramp compression is described with the following parameters: temperature, pressure, density, particle velocity and entropy production. Results show that the entropy production of the ramp compression process is small. This work can provide important supports for laser-driven ramp compression experiments in near future.
2013,
25: 2895-2899.
doi: 10.3788/HPLPB20132511.2895
Abstract:
According to the target chamber structure and shooting mode of SG-Ⅲ laser facility, a static X-ray imaging system (SXI) has been successfully developed based on the principle of pin-hole imaging. This system uses the imitated target for off-line targeting, and can be adjusted on-line, with the regulation accuracy of 81 m and 40 m. The pinhole component and filter component can be changed automatically, which realizes fast online aiming and running in vacuum environment. The displacement and stress were calculated using the software ANSYS to ensure the reliability of this system. Laser targeting evaluation of the system equipped with X-ray CCD has been conducted on SG-Ⅲ laser facility. The result shows that the system reaches the requirement of the SG-Ⅲ laser facility.
According to the target chamber structure and shooting mode of SG-Ⅲ laser facility, a static X-ray imaging system (SXI) has been successfully developed based on the principle of pin-hole imaging. This system uses the imitated target for off-line targeting, and can be adjusted on-line, with the regulation accuracy of 81 m and 40 m. The pinhole component and filter component can be changed automatically, which realizes fast online aiming and running in vacuum environment. The displacement and stress were calculated using the software ANSYS to ensure the reliability of this system. Laser targeting evaluation of the system equipped with X-ray CCD has been conducted on SG-Ⅲ laser facility. The result shows that the system reaches the requirement of the SG-Ⅲ laser facility.
2013,
25: 2900-2904.
doi: 10.3788/HPLPB20132511.2900
Abstract:
Systems of two-beam interference lithography and laser rapid scanning lithography were constructed. Gratings with different period and depth were fabricated over large areas by laser interference lithography. Utilizing the two-dimensional scan function of laser rapid scanner, exposure and distance between stuffers were optimized by controlling laser power and scanning speed. Two methods for two-scale texture fabrication were presented. The first one was that photoresist which had been scanned in x and y directions by scanning lithography was exposed in interference lithography system. The second one was that photoresist was exposed twice with different incidence angle in interference lithography system. The results show that the two methods were fast, cheap and controllable for two-scale texture fabrication.
Systems of two-beam interference lithography and laser rapid scanning lithography were constructed. Gratings with different period and depth were fabricated over large areas by laser interference lithography. Utilizing the two-dimensional scan function of laser rapid scanner, exposure and distance between stuffers were optimized by controlling laser power and scanning speed. Two methods for two-scale texture fabrication were presented. The first one was that photoresist which had been scanned in x and y directions by scanning lithography was exposed in interference lithography system. The second one was that photoresist was exposed twice with different incidence angle in interference lithography system. The results show that the two methods were fast, cheap and controllable for two-scale texture fabrication.
2013,
25: 2905-2908.
doi: 10.3788/HPLPB20132511.2905
Abstract:
Low-density tungsten-doped poly(4-methyl-1-petene) (PMP) polymer foams were prepared with thermal induced phase inversion method using PMP as the foam skeleton material, tungsten in micron dimension as doping materials, and upper ultra-high molecular weight polyethylene(UHWPE) as solution viscosity control agent. The results indicated that 10-m tungsten particle doped foams were synthesized uniformly when the mass content of UHWPE was 25%. The density of foam was 20 mg/cm3, while the mass content of doped tungsten reached up to 60%.
Low-density tungsten-doped poly(4-methyl-1-petene) (PMP) polymer foams were prepared with thermal induced phase inversion method using PMP as the foam skeleton material, tungsten in micron dimension as doping materials, and upper ultra-high molecular weight polyethylene(UHWPE) as solution viscosity control agent. The results indicated that 10-m tungsten particle doped foams were synthesized uniformly when the mass content of UHWPE was 25%. The density of foam was 20 mg/cm3, while the mass content of doped tungsten reached up to 60%.
2013,
25: 2909-2913.
doi: 10.3788/HPLPB20132511.2909
Abstract:
The treatment of H2S gas by the atmospheric pressure microwave plasma jet (MPJ) technology was studied. The influences of the temperature, the microwave power, the carrier(Ar) flow and total gas flow rate on H2S decomposition were investigated. The results show that, the temperature must be controlled in a certain range in order to process hydrogen sulfide; as the microwave power and the carrier gas flow increases, the decomposition rate of H2S is first increases, then decreases; with the increase of the total gas flow rate, the decomposition rate of H2S falls. The maximum decomposition rate of H2S reach to 91.32%, when the mass ratio of H2S to Ar is 10∶90, the total flow is 1000 mL/min, and the microwave is 1000 W. The production of the treatment was characterized by Raman spectroscopy and XRD (X-ray diffraction ), and the results show the solid state material is high purity sulfur.
The treatment of H2S gas by the atmospheric pressure microwave plasma jet (MPJ) technology was studied. The influences of the temperature, the microwave power, the carrier(Ar) flow and total gas flow rate on H2S decomposition were investigated. The results show that, the temperature must be controlled in a certain range in order to process hydrogen sulfide; as the microwave power and the carrier gas flow increases, the decomposition rate of H2S is first increases, then decreases; with the increase of the total gas flow rate, the decomposition rate of H2S falls. The maximum decomposition rate of H2S reach to 91.32%, when the mass ratio of H2S to Ar is 10∶90, the total flow is 1000 mL/min, and the microwave is 1000 W. The production of the treatment was characterized by Raman spectroscopy and XRD (X-ray diffraction ), and the results show the solid state material is high purity sulfur.
2013,
25: 2914-2918.
doi: 10.3788/HPLPB20132511.2914
Abstract:
With the mathematical statistics method, the impact of random phase error with arbitrary probability distribution on power combining efficiency of antenna array was analyzed. The analytic relationship between random phase error and expectation of combining efficiency of N-element antenna array was provided, which makes it easy to evaluate the impact of random phase error on array combining efficiency with fast-Fourier-transform (FFT) technology. As examples, the impact of random phase error with three typical distributions, uniform, Gaussian, and triangular distributions was discussed with the proposed analytical method.
With the mathematical statistics method, the impact of random phase error with arbitrary probability distribution on power combining efficiency of antenna array was analyzed. The analytic relationship between random phase error and expectation of combining efficiency of N-element antenna array was provided, which makes it easy to evaluate the impact of random phase error on array combining efficiency with fast-Fourier-transform (FFT) technology. As examples, the impact of random phase error with three typical distributions, uniform, Gaussian, and triangular distributions was discussed with the proposed analytical method.
2013,
25: 2919-2921.
doi: 10.3788/HPLPB20132511.2919
Abstract:
A novel design on miniaturized low-pass filters from artificial transmission line structures is proposed. Reactance components, i. e. capacitors and inductors, are directly constructed from microstrip structures based on electromagnetic simulation and parameter extraction. The constructed reactance components are integrated to build low-pass filters. The results of two 5th-order Butterworth and 0.5 dB ripple Chebyshev low-pass filters, which are realized by the proposed method, are presented. The proposed low-pass filter is compact and its size is only 23% of a conventional filter. The simulation agrees well to the measurements, which shows the validation of the proposed design method. The miniaturized low-pass filters have good applications in microwave systems.
A novel design on miniaturized low-pass filters from artificial transmission line structures is proposed. Reactance components, i. e. capacitors and inductors, are directly constructed from microstrip structures based on electromagnetic simulation and parameter extraction. The constructed reactance components are integrated to build low-pass filters. The results of two 5th-order Butterworth and 0.5 dB ripple Chebyshev low-pass filters, which are realized by the proposed method, are presented. The proposed low-pass filter is compact and its size is only 23% of a conventional filter. The simulation agrees well to the measurements, which shows the validation of the proposed design method. The miniaturized low-pass filters have good applications in microwave systems.
2013,
25: 2922-2926.
doi: 10.3788/HPLPB20132511.2922
Abstract:
The suppression of the frequency spectrum noise is the key in the magnetron research. The performance of 14-vanes 5.8 GHz strapped magnetron is modeled, including cathode, vane, straps, pole pieces and output antenna. The cavity frequency is 5.86 GHz in the cold cavity simulation. Seven electron spokes confirm the mode works in the oscillation cavity region by the hot simulation. A non-uniform magnetic field distribution is calculated as a conic section curve by the pole structure in the model. When beam voltage is 4.5 kV, the anode current is 1.55 A and the axial value of the non-uniform magnetic field is 0.289 T, the output frequency 5.891 GHz and output power 4.9 kW in the hot test simulation are obtained. The efficiency of the electron interaction is 70.3%. The remarkable improvement in the frequency spectrum and the electron efficiency are achieved by suppressing the RF harmonic content.
The suppression of the frequency spectrum noise is the key in the magnetron research. The performance of 14-vanes 5.8 GHz strapped magnetron is modeled, including cathode, vane, straps, pole pieces and output antenna. The cavity frequency is 5.86 GHz in the cold cavity simulation. Seven electron spokes confirm the mode works in the oscillation cavity region by the hot simulation. A non-uniform magnetic field distribution is calculated as a conic section curve by the pole structure in the model. When beam voltage is 4.5 kV, the anode current is 1.55 A and the axial value of the non-uniform magnetic field is 0.289 T, the output frequency 5.891 GHz and output power 4.9 kW in the hot test simulation are obtained. The efficiency of the electron interaction is 70.3%. The remarkable improvement in the frequency spectrum and the electron efficiency are achieved by suppressing the RF harmonic content.
2013,
25: 2927-2930.
doi: 10.3788/HPLPB20132511.2927
Abstract:
To reduce the Gyro-TWT cathode heating power, the paper adopts a new cathode structure with opening slot and adding heat shield on its support cylinder. The finite element analysis software ANSYS is used to optimize the number and the depth of slot and analyze the impact of heat shield on the cathode temperature. The relationship between the temperature of cathode emitter and the depth of slot is given. With the same temperature of cathode emitter, the heating power of the optimized structure is compared with that of the original structure. The results show that the heating power of the optimized structure decreases about 40%, greatly reducing the cathode heating power, which provide a certain reference value for the development of high performance cathode of gyrotron traveling wave tube.
To reduce the Gyro-TWT cathode heating power, the paper adopts a new cathode structure with opening slot and adding heat shield on its support cylinder. The finite element analysis software ANSYS is used to optimize the number and the depth of slot and analyze the impact of heat shield on the cathode temperature. The relationship between the temperature of cathode emitter and the depth of slot is given. With the same temperature of cathode emitter, the heating power of the optimized structure is compared with that of the original structure. The results show that the heating power of the optimized structure decreases about 40%, greatly reducing the cathode heating power, which provide a certain reference value for the development of high performance cathode of gyrotron traveling wave tube.
2013,
25: 2931-2938.
doi: 10.3788/HPLPB20132511.2931
Abstract:
One- and two- dimensional discontinuous Galerkin finite-element (DGFE) operators for solving Maxwells equations are investigated in this paper. These operators are based on unconventional spaces of approximation functions. Unlike in the existing DGFE method where the field components E and H are expanded with the same family of basis functions, in our scheme, it is attempted to compose various discontinuous Galerkin operators by approximating each of the two components in different function spaces and employing center numerical fluxes. With the combination of various basis function spaces for E and H, we build a series of operators. Through the calculation of the resonant modes of one- and two- dimensional PEC cavities on regular and irregular meshes, the convergence and spuriousness-supporting properties of these operators are examined, and based on which a selection of the optimal spaces of basis functions is made. Resonant modes calculated in time-domain and frequency-domain agree well with each other. It is shown not only that the proposed scheme is both non-dissipative and spurious-free, but also that no additional auxiliary variables are required, thus providing a new way to develop high quality algorithm for the Maxwells equations and the corresponding electromagnetic field simulating software.
One- and two- dimensional discontinuous Galerkin finite-element (DGFE) operators for solving Maxwells equations are investigated in this paper. These operators are based on unconventional spaces of approximation functions. Unlike in the existing DGFE method where the field components E and H are expanded with the same family of basis functions, in our scheme, it is attempted to compose various discontinuous Galerkin operators by approximating each of the two components in different function spaces and employing center numerical fluxes. With the combination of various basis function spaces for E and H, we build a series of operators. Through the calculation of the resonant modes of one- and two- dimensional PEC cavities on regular and irregular meshes, the convergence and spuriousness-supporting properties of these operators are examined, and based on which a selection of the optimal spaces of basis functions is made. Resonant modes calculated in time-domain and frequency-domain agree well with each other. It is shown not only that the proposed scheme is both non-dissipative and spurious-free, but also that no additional auxiliary variables are required, thus providing a new way to develop high quality algorithm for the Maxwells equations and the corresponding electromagnetic field simulating software.
2013,
25: 2939-2942.
doi: 10.3788/HPLPB20132511.2939
Abstract:
A model of multimode startup in the coaxial-cavity gyrotron operating at higher-order mode with mode competition taken into account is presented in this paper, the detailed numerical calculation method is also given. By the use of the code based on this model, the nonlinear multimode simulations on a coaxial-cavity gyrotron with the high-order mode TE42, 22 at a frequency of 0.22 THz are performed. The results show that with proper cavity parameters and considering the ohmic losses on the wall, the competing modes can be effectively suppressed, this resonator can operate stably at a single mode with the output power of 0.87 MW and corresponding efficiency of 22.8%, and the maximum density of ohmic losses on the wall is below the constraint.
A model of multimode startup in the coaxial-cavity gyrotron operating at higher-order mode with mode competition taken into account is presented in this paper, the detailed numerical calculation method is also given. By the use of the code based on this model, the nonlinear multimode simulations on a coaxial-cavity gyrotron with the high-order mode TE42, 22 at a frequency of 0.22 THz are performed. The results show that with proper cavity parameters and considering the ohmic losses on the wall, the competing modes can be effectively suppressed, this resonator can operate stably at a single mode with the output power of 0.87 MW and corresponding efficiency of 22.8%, and the maximum density of ohmic losses on the wall is below the constraint.
2013,
25: 2943-2948.
doi: 10.3788/HPLPB20132511.2943
Abstract:
An improved low-impedance transit-time oscillator loaded with washer-like structure is proposed and investigated by using the 2.5D fully electromagnetic particle-in-cell code. The extractor operates at -like mode, which is advantageous to keep a high efficiency of the beam-wave interaction. Due to the adoption of the tapered output waveguide, the microwave can be extracted more effectively. Loading inductive metal rods can not only support the washers, but also ground the DC induced charge in the washers. The optimized simulation results show that a 7.76 GHz, 2.74 GW microwave can be obtained with a efficiency of 40% under the condition of the diode voltage 530 kV，the current 12.9 kA and the guiding magnetic field 0.7 T.
An improved low-impedance transit-time oscillator loaded with washer-like structure is proposed and investigated by using the 2.5D fully electromagnetic particle-in-cell code. The extractor operates at -like mode, which is advantageous to keep a high efficiency of the beam-wave interaction. Due to the adoption of the tapered output waveguide, the microwave can be extracted more effectively. Loading inductive metal rods can not only support the washers, but also ground the DC induced charge in the washers. The optimized simulation results show that a 7.76 GHz, 2.74 GW microwave can be obtained with a efficiency of 40% under the condition of the diode voltage 530 kV，the current 12.9 kA and the guiding magnetic field 0.7 T.
2013,
25: 2949-2953.
doi: 10.3788/HPLPB20132511.2949
Abstract:
Multi-unit radial-line sub-array can be used to reduce cascade of array feed network, thus contributing to reducing the loss of the whole feed network, and triangle-grid arrangement can reduce the number of antenna units so as to reduce the cost effectively. Therefore, the design idea of multi-unit triangle-grid radial-line sub-array is proposed. Based on the required coupling amount of feed network, a new coupling probe is designed, and moreover a 66-element triangle-grid radial-line feed network at the center frequency of 2.856 GHz is designed. Simulation results show that, this feed network basically achieves an equal amplitude of 66 units coupling coefficient, and in the frequency band from 2.78 GHz to 2.92 GHz, the reflection coefficient is lower than 0.1. In addition, simulation on the radiation characteristics of the feed network which is loaded with the antenna units is carried out, which further verifies the feasibility of the design.
Multi-unit radial-line sub-array can be used to reduce cascade of array feed network, thus contributing to reducing the loss of the whole feed network, and triangle-grid arrangement can reduce the number of antenna units so as to reduce the cost effectively. Therefore, the design idea of multi-unit triangle-grid radial-line sub-array is proposed. Based on the required coupling amount of feed network, a new coupling probe is designed, and moreover a 66-element triangle-grid radial-line feed network at the center frequency of 2.856 GHz is designed. Simulation results show that, this feed network basically achieves an equal amplitude of 66 units coupling coefficient, and in the frequency band from 2.78 GHz to 2.92 GHz, the reflection coefficient is lower than 0.1. In addition, simulation on the radiation characteristics of the feed network which is loaded with the antenna units is carried out, which further verifies the feasibility of the design.
2013,
25: 2954-2958.
doi: 10.3788/HPLPB20132511.2954
Abstract:
Several micro-machinings were used to manufacture 0.22 THz folded waveguide slow wave structure. In with these micro-machinings, micro-milling was most suitable for manufacturing 0.22 THz folded waveguide slow wave structure now. And the loss of WR4 waveguide manufactured by micro-milling was tested. The relative conductivity of 3.2107 S/m was obtained when electromagnetic wave of 0.22 THz propagated in oxygen-free copper waveguide. Finally, a 0.22 THz folded waveguide TWT was developed and experimented with output power greater than 100 mW and 3 dB bandwidth of 3.5 GHz.
Several micro-machinings were used to manufacture 0.22 THz folded waveguide slow wave structure. In with these micro-machinings, micro-milling was most suitable for manufacturing 0.22 THz folded waveguide slow wave structure now. And the loss of WR4 waveguide manufactured by micro-milling was tested. The relative conductivity of 3.2107 S/m was obtained when electromagnetic wave of 0.22 THz propagated in oxygen-free copper waveguide. Finally, a 0.22 THz folded waveguide TWT was developed and experimented with output power greater than 100 mW and 3 dB bandwidth of 3.5 GHz.
2013,
25: 2959-2964.
doi: 10.3788/HPLPB20132511.2959
Abstract:
Based on the hot electron effect of n-Si irradiated by high electric field, a 0.14 THz high-power terahertz pulse detector using overmoded structure is proposed and fabricated. The detector consists of a fundamental mode wavguide WR6, a tapered waveguide, an overmoded waveguide WR10, a detecting chip made of n-Si, and a bias constant current source. First, the working process of the detector is analyzed, showing that the detector can be operated in the TE10 mode well, and the expression of its relative sensitivity is given. Then, the structural parameters and manufacture techniques of detecting chip are reasonably designed, and the fabrication of detecting chips and detector prototypes is accomplished. Ultimately, the validation experiments of the detector prototype are carried out in the radiation field of the 0.14 THz relativistic surface wave oscillator, which are analyzed and compared with the measured results of diode detector. The experimental results show that, the overmoded detector prototype has a response time of picoseconds-level, the relative sensitivity of about 0.12 kW-1, and the maximum enduring power of tens of watts. Therefore, the sensor could be used to directly detect 0.14 THz high-power pulses.
Based on the hot electron effect of n-Si irradiated by high electric field, a 0.14 THz high-power terahertz pulse detector using overmoded structure is proposed and fabricated. The detector consists of a fundamental mode wavguide WR6, a tapered waveguide, an overmoded waveguide WR10, a detecting chip made of n-Si, and a bias constant current source. First, the working process of the detector is analyzed, showing that the detector can be operated in the TE10 mode well, and the expression of its relative sensitivity is given. Then, the structural parameters and manufacture techniques of detecting chip are reasonably designed, and the fabrication of detecting chips and detector prototypes is accomplished. Ultimately, the validation experiments of the detector prototype are carried out in the radiation field of the 0.14 THz relativistic surface wave oscillator, which are analyzed and compared with the measured results of diode detector. The experimental results show that, the overmoded detector prototype has a response time of picoseconds-level, the relative sensitivity of about 0.12 kW-1, and the maximum enduring power of tens of watts. Therefore, the sensor could be used to directly detect 0.14 THz high-power pulses.
2013,
25: 2965-2970.
doi: 10.3788/HPLPB20132511.2965
Abstract:
An experiment was conducted on the shock tube to explore the transmission characteristics of millimeter wave and terahertz wave in high density plasmas, in order to meet the communication requirement of hypersonic vehicles during blackout. The transmission attenuation curves of millimeter wave and terahertz wave in different electron density and collision frequency were obtained. The experiment was also simulated by auxiliary differential equation finite-difference time-domain (ADE-FDTD) methods. The experimental and numerical results show that the transmission attenuation of terahertz wave in the plasma is smaller than that of millimeter wave under the same conditions. The transmission attenuation of terahertz wave in the plasma is enhanced with the increase of electron density. The terahertz wave is a promising alternative to the electromagnetic wave propagation in high density plasmas.
An experiment was conducted on the shock tube to explore the transmission characteristics of millimeter wave and terahertz wave in high density plasmas, in order to meet the communication requirement of hypersonic vehicles during blackout. The transmission attenuation curves of millimeter wave and terahertz wave in different electron density and collision frequency were obtained. The experiment was also simulated by auxiliary differential equation finite-difference time-domain (ADE-FDTD) methods. The experimental and numerical results show that the transmission attenuation of terahertz wave in the plasma is smaller than that of millimeter wave under the same conditions. The transmission attenuation of terahertz wave in the plasma is enhanced with the increase of electron density. The terahertz wave is a promising alternative to the electromagnetic wave propagation in high density plasmas.
2013,
25: 2971-2975.
doi: 10.3788/HPLPB20132511.2971
Abstract:
A stripline beam position monitor(BPM) was designed for HLS Ⅱupgraded and used to measure beam parameter in the HLS storage ring. Position signal was offline calibrated using the difference/sum and log-ratio methods. Sensitivities, mapping figures and experienced fitting polynomials were acquired. The results showed that the sensitivities and linear range using logratio method were bigger than those using difference/sum method. The sum signal was offline calibrated and the result showed that the variety of normalized sum signal relative to the sum signal at the stripline BPM center was no more than 6 % in the range of (-5 mm, -5 mm) to (5 mm, 5 mm). The stripline BPM will be also used to measure the transverse quadrupole oscillation in the HLS storage ring, so calibrating transverse quadrupole component is needed. The Gaussian weighted method of a two-dimensional grid structure was used to simulate the Gaussian bunch and the difference/sum method was applied to calculate transverse quadrupole component. The measurement result was compared with the simulation result. The result showed that the sensitivity of the transverse quadrupole component varying with (x2-y2) by offline method was the same as simulation result and sensitivity was 0.001 1 mm-2. Experienced fitting polynomial was calculated to be used for the future online measurement.
A stripline beam position monitor(BPM) was designed for HLS Ⅱupgraded and used to measure beam parameter in the HLS storage ring. Position signal was offline calibrated using the difference/sum and log-ratio methods. Sensitivities, mapping figures and experienced fitting polynomials were acquired. The results showed that the sensitivities and linear range using logratio method were bigger than those using difference/sum method. The sum signal was offline calibrated and the result showed that the variety of normalized sum signal relative to the sum signal at the stripline BPM center was no more than 6 % in the range of (-5 mm, -5 mm) to (5 mm, 5 mm). The stripline BPM will be also used to measure the transverse quadrupole oscillation in the HLS storage ring, so calibrating transverse quadrupole component is needed. The Gaussian weighted method of a two-dimensional grid structure was used to simulate the Gaussian bunch and the difference/sum method was applied to calculate transverse quadrupole component. The measurement result was compared with the simulation result. The result showed that the sensitivity of the transverse quadrupole component varying with (x2-y2) by offline method was the same as simulation result and sensitivity was 0.001 1 mm-2. Experienced fitting polynomial was calculated to be used for the future online measurement.
2013,
25: 2976-2980.
doi: 10.3788/HPLPB20132511.2976
Abstract:
To set emittance, velocity spread and beam tilt correctly, a multi-function emission module is developed in LIAPIC3D code. This module development is based on beam emission module, which could set beam energy, beam length correctly. During experiment, researchers could get value and angle of emittance. When setting emittance, researchers must input these two parameters. To set velocity spread, a Gauss random function is created. This function could create Gauss distribution random values, and which are related to particle energy. Beam tilt direction is determined by two angle parameters. After development of multi-function emission module, a proof principle simulation is designed. Emittance in different direction, velocity spread in z direction, and beam tilt are tested in simulation. The simulation results are coincident with input values, verifying the development of the multi-function module.
To set emittance, velocity spread and beam tilt correctly, a multi-function emission module is developed in LIAPIC3D code. This module development is based on beam emission module, which could set beam energy, beam length correctly. During experiment, researchers could get value and angle of emittance. When setting emittance, researchers must input these two parameters. To set velocity spread, a Gauss random function is created. This function could create Gauss distribution random values, and which are related to particle energy. Beam tilt direction is determined by two angle parameters. After development of multi-function emission module, a proof principle simulation is designed. Emittance in different direction, velocity spread in z direction, and beam tilt are tested in simulation. The simulation results are coincident with input values, verifying the development of the multi-function module.
2013,
25: 2981-2985.
doi: 10.3788/HPLPB20132511.2981
Abstract:
An 11 MeV cyclotron used for production of positron emission radionuclide aiming at positron emission tomography (PET) imaging produces a huge quantity of instant neutron and gamma ray radiation. For shielding this kind of accelerator, a self-shielding bunker-like structure is employed, which can be designed with Monte Carlo method. The discrete dual-differential section data are calculated first to obtain the input data for Monte Carlo code, with which the protection characteristics with a single layer and composite structure of various materials are simulated next. The results show that with a single layer, the heavy concrete which has 73.8% iron content brings greatest protection characteristic among all of the materials included in this paper and attenuates the total dose rate about 100 kilo times at the position of 1 m far away from the radiation source with 0 emission angle with thickness of 90 cm. With materials of iron and boracic acid liquor, a particular composite structure can bring the same characteristic with the same thickness and reduce the total density about 20% at least.
An 11 MeV cyclotron used for production of positron emission radionuclide aiming at positron emission tomography (PET) imaging produces a huge quantity of instant neutron and gamma ray radiation. For shielding this kind of accelerator, a self-shielding bunker-like structure is employed, which can be designed with Monte Carlo method. The discrete dual-differential section data are calculated first to obtain the input data for Monte Carlo code, with which the protection characteristics with a single layer and composite structure of various materials are simulated next. The results show that with a single layer, the heavy concrete which has 73.8% iron content brings greatest protection characteristic among all of the materials included in this paper and attenuates the total dose rate about 100 kilo times at the position of 1 m far away from the radiation source with 0 emission angle with thickness of 90 cm. With materials of iron and boracic acid liquor, a particular composite structure can bring the same characteristic with the same thickness and reduce the total density about 20% at least.
2013,
25: 2986-2990.
doi: 10.3788/HPLPB20132511.2986
Abstract:
The design and test of the low-level RF (LLRF) control system for the dual-harmonic acceleration at the rapid cycling synchrotron (RCS) of China Spallation Neutron Source (CSNS) at phase Ⅰ is introduced. In order to implement the mode switch from the second harmonic to the fundamental during the acceleration cycle for one of the eight RF cavities, the LLRF system for the cavity has been designed differently from the others. Several technical measures such as the opening of the control loops during the mode switch and the reclosing of two tuning circuits of the RF amplifier at different moments, have been taken. The experimental results on the testing platform based on an RF prototype show good dynamic performance of the LLRF system and prove the feasibility of dual-harmonic operation.
The design and test of the low-level RF (LLRF) control system for the dual-harmonic acceleration at the rapid cycling synchrotron (RCS) of China Spallation Neutron Source (CSNS) at phase Ⅰ is introduced. In order to implement the mode switch from the second harmonic to the fundamental during the acceleration cycle for one of the eight RF cavities, the LLRF system for the cavity has been designed differently from the others. Several technical measures such as the opening of the control loops during the mode switch and the reclosing of two tuning circuits of the RF amplifier at different moments, have been taken. The experimental results on the testing platform based on an RF prototype show good dynamic performance of the LLRF system and prove the feasibility of dual-harmonic operation.
2013,
25: 2991-2994.
doi: 10.3788/HPLPB20132511.2991
Abstract:
A compact cyclotron as the injector of a synchrotron which forms the heavy ion medical machine is being designed and constructed at Institute of Modern Physics, China. The required high intensity and high beam quality of the extraction beam make it difficult to design the extraction system. The magnetic field used in the design is calculated from TOSCA model. The single particle orbit is calculated to determine component types and basic parameters of the extraction system. The multi-particle tracking is done to determine the final component parameters and beam parameters. In order to improve the efficiency and beam quality of the extraction system, a C-type magnet is placed at the location, where the magnetic field gradient is very large. A pair of coil is used to eliminate the effect of the C-type magnet on the main magnetic field. Detailed calculations show the extraction beam intensity and beam quality can meet the requirement of the synchrotron.
A compact cyclotron as the injector of a synchrotron which forms the heavy ion medical machine is being designed and constructed at Institute of Modern Physics, China. The required high intensity and high beam quality of the extraction beam make it difficult to design the extraction system. The magnetic field used in the design is calculated from TOSCA model. The single particle orbit is calculated to determine component types and basic parameters of the extraction system. The multi-particle tracking is done to determine the final component parameters and beam parameters. In order to improve the efficiency and beam quality of the extraction system, a C-type magnet is placed at the location, where the magnetic field gradient is very large. A pair of coil is used to eliminate the effect of the C-type magnet on the main magnetic field. Detailed calculations show the extraction beam intensity and beam quality can meet the requirement of the synchrotron.
2013,
25: 2995-2998.
doi: 10.3788/HPLPB20132511.2995
Abstract:
Measurement of high-energy X-ray energy spectrum is difficult in high-energy flash X-ray radiograph. According to previous studies, controlling the influence of diffusion to a certain extent is very important to improve the precision of energy spectrum measurement. In this paper, circular array method (CAM) is introduced to measuring X-ray energy spectrum. An experiment setup is designed. Simulation from Monte-Carlo suggests that it is possible to control the influence of diffusion within 4%.
Measurement of high-energy X-ray energy spectrum is difficult in high-energy flash X-ray radiograph. According to previous studies, controlling the influence of diffusion to a certain extent is very important to improve the precision of energy spectrum measurement. In this paper, circular array method (CAM) is introduced to measuring X-ray energy spectrum. An experiment setup is designed. Simulation from Monte-Carlo suggests that it is possible to control the influence of diffusion within 4%.
2013,
25: 2999-3001.
doi: 10.3788/HPLPB20132511.2999
Abstract:
The shortest pulse width of ECR proton source is about sub-millisecond. A chopper or a kicker is important to produce 100 ns pulsed proton beams for high gradient accelerating structure. Physical design of an electrostatic kicker was described in this paper. The configuration of the kicker was matched with an ECR proton source which was being investigated. Electrostatic field was calculated with ANSYS. The capacitance of the kicker was extracted with CMATRIX command macro. Relations between beams rising time and kicker pulses rising time were discussed. The desire for pulsed power supply was also analyzed.
The shortest pulse width of ECR proton source is about sub-millisecond. A chopper or a kicker is important to produce 100 ns pulsed proton beams for high gradient accelerating structure. Physical design of an electrostatic kicker was described in this paper. The configuration of the kicker was matched with an ECR proton source which was being investigated. Electrostatic field was calculated with ANSYS. The capacitance of the kicker was extracted with CMATRIX command macro. Relations between beams rising time and kicker pulses rising time were discussed. The desire for pulsed power supply was also analyzed.
2013,
25: 3004-3008.
doi: 10.3788/HPLPB20132511.3004
Abstract:
High gradient insulator(HGI) structures assembled from alternating layers of metal and dielectric can result in improved performance of flashover compared to conventional insulators as they can restrain the process of vacuum flashover. Samples which are constituted of different materials and processed by different preparations have huge difference in surface breakdown field strength. Performance of flashover of the samples with different materials and different sizes were tested, and the influence factors of sample surface flashover field strength was analyzed with the surface micrographs.
High gradient insulator(HGI) structures assembled from alternating layers of metal and dielectric can result in improved performance of flashover compared to conventional insulators as they can restrain the process of vacuum flashover. Samples which are constituted of different materials and processed by different preparations have huge difference in surface breakdown field strength. Performance of flashover of the samples with different materials and different sizes were tested, and the influence factors of sample surface flashover field strength was analyzed with the surface micrographs.
2013,
25: 3009-3012.
doi: 10.3788/HPLPB20132511.3009
Abstract:
The beam online data processing system is an important part of control and diagnoses system on the multi-pulse and high current LIA. The hardware includes many measurement instruments and computers which construct the industrial ethernet network. Many software models are accomplished on LabVIEW which include the measurement network configuration, data collection, computing intensity and position of beam, calibration parameter input display and storage, etc. The method of the resistance ring is applied for beam measurement to the multi-pulse LIA, and the waves of beam intensity and position are achieved according to the oscillograph voltage wave and calibration parameters, and statistical beam parameters are computed based on waves. Two ways for data storage are applied cooperatively. The system runs steadily and reliably on multi-pulse and high current LIA by this time and which gives valid and reliable information for experiment.
The beam online data processing system is an important part of control and diagnoses system on the multi-pulse and high current LIA. The hardware includes many measurement instruments and computers which construct the industrial ethernet network. Many software models are accomplished on LabVIEW which include the measurement network configuration, data collection, computing intensity and position of beam, calibration parameter input display and storage, etc. The method of the resistance ring is applied for beam measurement to the multi-pulse LIA, and the waves of beam intensity and position are achieved according to the oscillograph voltage wave and calibration parameters, and statistical beam parameters are computed based on waves. Two ways for data storage are applied cooperatively. The system runs steadily and reliably on multi-pulse and high current LIA by this time and which gives valid and reliable information for experiment.
2013,
25: 3013-3016.
doi: 10.3788/HPLPB20132511.3013
Abstract:
HIRFL-CSR (Heavy Ion Research Facility in Lanzhou-Cooler Storage Ring) control system has been working normally for nuclear physics experiment and tumor therapy experiment in recent years. HIRFL-CSR control system is a large distributed control system designed for completing HIRFL-CSR. HIRFL-CSR control system has three tiers: business tier, front-end control tier and device control tier. Business tier mainly includes control management program, central database and synchronous timing system; front-end control tier mainly includes front-end server and front-end controller; device control tier mainly includes MCU multifunction controller and controlled device. The central database stores all accelerator control data and provides data to support accelerator changes beam energy. HIRFL-CSR control system can basically meet nuclear physics experiment and tumor therapy experiment requirements, which is based on long-running situation.
HIRFL-CSR (Heavy Ion Research Facility in Lanzhou-Cooler Storage Ring) control system has been working normally for nuclear physics experiment and tumor therapy experiment in recent years. HIRFL-CSR control system is a large distributed control system designed for completing HIRFL-CSR. HIRFL-CSR control system has three tiers: business tier, front-end control tier and device control tier. Business tier mainly includes control management program, central database and synchronous timing system; front-end control tier mainly includes front-end server and front-end controller; device control tier mainly includes MCU multifunction controller and controlled device. The central database stores all accelerator control data and provides data to support accelerator changes beam energy. HIRFL-CSR control system can basically meet nuclear physics experiment and tumor therapy experiment requirements, which is based on long-running situation.
2013,
25: 3017-3020.
doi: 10.3788/HPLPB20132511.3017
Abstract:
Imaging simulation by means of the Monte Carlo method is performed for the spectrum reconstruction of the X-ray which is produced by high-energy intense-current electron beam striking a high-Z target. Generally, the high-energy X-ray spectrum can be resolved from the primary transmission curve when the X-ray passes through the attenuator. A truncated cone model with collimating apertures is designed, by which an entire attenuation transmission curve is obtained in a single imaging simulation. The scattering photons are effectively obstructed from disturbing the transmission curve and finally the spectrum reconstruction. A non-uniform grid for tallying is adopted for the imaging plane in order to concentrate most of the probing tallies at the exit of each collimating aperture, which guarantees a fine imaging for the concerned region while reduces the total computing time.
Imaging simulation by means of the Monte Carlo method is performed for the spectrum reconstruction of the X-ray which is produced by high-energy intense-current electron beam striking a high-Z target. Generally, the high-energy X-ray spectrum can be resolved from the primary transmission curve when the X-ray passes through the attenuator. A truncated cone model with collimating apertures is designed, by which an entire attenuation transmission curve is obtained in a single imaging simulation. The scattering photons are effectively obstructed from disturbing the transmission curve and finally the spectrum reconstruction. A non-uniform grid for tallying is adopted for the imaging plane in order to concentrate most of the probing tallies at the exit of each collimating aperture, which guarantees a fine imaging for the concerned region while reduces the total computing time.
2013,
25: 3021-3024.
doi: 10.3788/HPLPB20132511.3021
Abstract:
To meet the requirement of small sample studies on the neutron diffraction complex, a one-dimensional ellipse focusing mirror system was designed and its parameters were optimized. The effects of elliptical focusing mirror parameters on the neutron flux at sample were evaluated by both employing elliptical analytical calculation and neutron tracing simulation package McStas. And the optimal parameters of the mirror for the maximum neutron flux were investigated and obtained. The results show that in the source (left ellipse focus) to the sample (right ellipse focus) distance of 2.7 m, the super mirror factor of 3 and the mirror length of 25 cm case, the optimum right-position of the ellipse mirror is at distance 560 mm from sample and the half long axis is 1 350.016 mm. In optimized condition, the neutron flux at the sample can be improved 7 times.
To meet the requirement of small sample studies on the neutron diffraction complex, a one-dimensional ellipse focusing mirror system was designed and its parameters were optimized. The effects of elliptical focusing mirror parameters on the neutron flux at sample were evaluated by both employing elliptical analytical calculation and neutron tracing simulation package McStas. And the optimal parameters of the mirror for the maximum neutron flux were investigated and obtained. The results show that in the source (left ellipse focus) to the sample (right ellipse focus) distance of 2.7 m, the super mirror factor of 3 and the mirror length of 25 cm case, the optimum right-position of the ellipse mirror is at distance 560 mm from sample and the half long axis is 1 350.016 mm. In optimized condition, the neutron flux at the sample can be improved 7 times.
2013,
25: 3025-3028.
doi: 10.3788/HPLPB20132511.3025
Abstract:
In order to study damage of plasma energy generated by hypervelocity impact on spacecraft electronic components, It is necessary to obtain temporal and spatial distribution characteristics of particle energy induced by hypervelocity impact. The relationship between the particle energy density and the particle velocity was derived based on charge particle motive velocity and diffusive characteristic. We obtained temporal and the spatial distribution rules of particle energy in thin plasma cloud generated by hypervelocity impact 2024-T4 Aluminum targets based on analysis of original data from impacting 2024-T4 Aluminum target experiment and Matlab computer codes.
In order to study damage of plasma energy generated by hypervelocity impact on spacecraft electronic components, It is necessary to obtain temporal and spatial distribution characteristics of particle energy induced by hypervelocity impact. The relationship between the particle energy density and the particle velocity was derived based on charge particle motive velocity and diffusive characteristic. We obtained temporal and the spatial distribution rules of particle energy in thin plasma cloud generated by hypervelocity impact 2024-T4 Aluminum targets based on analysis of original data from impacting 2024-T4 Aluminum target experiment and Matlab computer codes.
2013,
25: 3029-3034.
doi: 10.3788/HPLPB20132511.3029
Abstract:
The duration and the interval of the pulsed source neutrons are two key timing parameters of PFTNA (pulsed fast/thermal neutron analysis) method. However, there are still no relative literatures about the evaluation and the setting of these two parameters, both at home and abroad. An function S was established to quantitavely evaluate the parameters, and then a theoretical model was proposed to obtain the optimal timing parameters. The calculation process was simplified by regarding the target object and surrounding mediums as a linear time invariant system. It was mathematically proved that the optimal duration and the interval had the equal value. The scenario of PELAN applied to landmine detection was chosen to expound the detailed calculation procedures based on the above-mentioned theoretical model. Furthermore, adaptability of the model to the surrounding medium and that to the detection layout were also fully tested. It was illustrated that, optimal timing parameters of the PFTNA method can be easily obtained through the theoretical model, meanwhile the model showed a strong adaptability to both the surrounding medium and the detection layout. Effective reference timing parameters could be provided when PFTNA method was applied to the fields like material analysis, contraband detection and landmine identification.
The duration and the interval of the pulsed source neutrons are two key timing parameters of PFTNA (pulsed fast/thermal neutron analysis) method. However, there are still no relative literatures about the evaluation and the setting of these two parameters, both at home and abroad. An function S was established to quantitavely evaluate the parameters, and then a theoretical model was proposed to obtain the optimal timing parameters. The calculation process was simplified by regarding the target object and surrounding mediums as a linear time invariant system. It was mathematically proved that the optimal duration and the interval had the equal value. The scenario of PELAN applied to landmine detection was chosen to expound the detailed calculation procedures based on the above-mentioned theoretical model. Furthermore, adaptability of the model to the surrounding medium and that to the detection layout were also fully tested. It was illustrated that, optimal timing parameters of the PFTNA method can be easily obtained through the theoretical model, meanwhile the model showed a strong adaptability to both the surrounding medium and the detection layout. Effective reference timing parameters could be provided when PFTNA method was applied to the fields like material analysis, contraband detection and landmine identification.
2013,
25: 3035-3039.
doi: 10.3788/HPLPB20132511.3035
Abstract:
The material databases for the Vaughans secondary electron model which is popularly utilized in the plasma simulation are abundant. Most of them are highly accurate and reliable, due to the validations of experiments. In order to integrate these precious databases into our electromagnetic-particle simulation platform and improve the computational precision of our simulation platform, the classic Vaughans model for the secondary electron emission is firstly researched. Based on the derivation of the numerical method to generate the actual number of secondary electrons, the way to calculate the energy of each secondary electron and the method to obtain the emissive angle are successfully proposed. Due to our work, it is more convenient to numerically implement the Vaughans theorem in practical applications. Furthermore, the accuracy and the robustness of our proposed methods are validated by the computational results in this paper.
The material databases for the Vaughans secondary electron model which is popularly utilized in the plasma simulation are abundant. Most of them are highly accurate and reliable, due to the validations of experiments. In order to integrate these precious databases into our electromagnetic-particle simulation platform and improve the computational precision of our simulation platform, the classic Vaughans model for the secondary electron emission is firstly researched. Based on the derivation of the numerical method to generate the actual number of secondary electrons, the way to calculate the energy of each secondary electron and the method to obtain the emissive angle are successfully proposed. Due to our work, it is more convenient to numerically implement the Vaughans theorem in practical applications. Furthermore, the accuracy and the robustness of our proposed methods are validated by the computational results in this paper.
2013,
25: 3040-3044.
doi: 10.3788/HPLPB20132511.3040
Abstract:
In order to obtain arbitrary planes of industrial CT volume data, a new fast section display algorithm based on 3D texture mapping was proposed. Firstly, industrial CT serial images were loaded in sequence and stored as volume data. Secondly, these data were defined as 3D texture after transforming by the transfer function. Then according to the plane parameters given by the user, the cutting polygon on the section plane was calculated, which made a preparation for the calculation of corresponding 3D texture coordinates. Finally, a section plane was obtained by mapping conducted. The main feature of this method is that it completes sampling and interpolation with texture mapping supported by the graphics processor. The experimental results show the presented algorithm could capture the slice data in arbitrary direction，and also satisfy the speed requirements of the Human-Computer Interaction.
In order to obtain arbitrary planes of industrial CT volume data, a new fast section display algorithm based on 3D texture mapping was proposed. Firstly, industrial CT serial images were loaded in sequence and stored as volume data. Secondly, these data were defined as 3D texture after transforming by the transfer function. Then according to the plane parameters given by the user, the cutting polygon on the section plane was calculated, which made a preparation for the calculation of corresponding 3D texture coordinates. Finally, a section plane was obtained by mapping conducted. The main feature of this method is that it completes sampling and interpolation with texture mapping supported by the graphics processor. The experimental results show the presented algorithm could capture the slice data in arbitrary direction，and also satisfy the speed requirements of the Human-Computer Interaction.
2013,
25: 3045-3049.
doi: 10.3788/HPLPB20132511.3045
Abstract:
To eliminate the influence of the random background spectra on the prompt spectra in the associated particle technique，the random background spectra induced by non-tagged neutrons and the prompt spectra induced by tagged neutrons were studied in experiment. Measurements of the random background spectra in different condition were analyzed. The methods of acquiring random spectra were proposed for the bulk and small sample of different substances. For small sample，the background spectra can be obtained without the sample by selecting the same time window as in measuring the prompt spectra with the sample. In the case of the tagged neutron range less than the volume of the sample, the background spectra can be obtained with the sample by selecting the time window during the random time.
To eliminate the influence of the random background spectra on the prompt spectra in the associated particle technique，the random background spectra induced by non-tagged neutrons and the prompt spectra induced by tagged neutrons were studied in experiment. Measurements of the random background spectra in different condition were analyzed. The methods of acquiring random spectra were proposed for the bulk and small sample of different substances. For small sample，the background spectra can be obtained without the sample by selecting the same time window as in measuring the prompt spectra with the sample. In the case of the tagged neutron range less than the volume of the sample, the background spectra can be obtained with the sample by selecting the time window during the random time.
2013,
25: 3050-3054.
doi: 10.3788/HPLPB20132511.3050
Abstract:
The accuracy in reverberation chamber (RC) measurements depends on the chamber settings being able to generate a large number of independent measurement samples. In this paper, an approximate theoretical model of the number of independent samples is derived by theoretically analyzing how the RC configuration and the frequency influence the number of independent samples, and the model is improved and verified by comparing a large amount of experimental data and calculation. The results show that the number of independent samples positively correlates with chamber volume, quality factor, and stirrer size, and negatively correlates with the electrical size of stirrers in a certain range. The model can be used to calculate the number of independent samples in RCs of different configurations, with good accuracy and generality.
The accuracy in reverberation chamber (RC) measurements depends on the chamber settings being able to generate a large number of independent measurement samples. In this paper, an approximate theoretical model of the number of independent samples is derived by theoretically analyzing how the RC configuration and the frequency influence the number of independent samples, and the model is improved and verified by comparing a large amount of experimental data and calculation. The results show that the number of independent samples positively correlates with chamber volume, quality factor, and stirrer size, and negatively correlates with the electrical size of stirrers in a certain range. The model can be used to calculate the number of independent samples in RCs of different configurations, with good accuracy and generality.
2013,
25: 3055-3059.
doi: 10.3788/HPLPB20132511.3055
Abstract:
The coaxial self-magnetic field generated by pulsed current of low impedance generator could affect the vacuum insulator surface flashover characteristics because of the magnetic-flashover-inhibition (MFI) effect. In coaxial electrode structure, the ratio of electric field E and magnetic field B is independent of variety of radius, but only depends on circuit parameters. Four coaxial structures are designed with different ratios of E/cB, viz. , 0.041, 0.05, 0.056, and 0.062. Two type experiments, with and without magnetic field, are carried out. The experimental results show that, the surface flashover voltage with appropriate magnetic field orientation to MFI is increased obviously, compared to that without magnetic field. The smaller the ratio of E/cB is, the higher the flashover voltage is. When the ratio of E/cB is 0.041, the flashover voltage can increase to about 1.3 times that in non-magnetic field condition. But flashover voltage will decrease when the orientation of magnetic field is reversed.
The coaxial self-magnetic field generated by pulsed current of low impedance generator could affect the vacuum insulator surface flashover characteristics because of the magnetic-flashover-inhibition (MFI) effect. In coaxial electrode structure, the ratio of electric field E and magnetic field B is independent of variety of radius, but only depends on circuit parameters. Four coaxial structures are designed with different ratios of E/cB, viz. , 0.041, 0.05, 0.056, and 0.062. Two type experiments, with and without magnetic field, are carried out. The experimental results show that, the surface flashover voltage with appropriate magnetic field orientation to MFI is increased obviously, compared to that without magnetic field. The smaller the ratio of E/cB is, the higher the flashover voltage is. When the ratio of E/cB is 0.041, the flashover voltage can increase to about 1.3 times that in non-magnetic field condition. But flashover voltage will decrease when the orientation of magnetic field is reversed.
2013,
25: 3060-3064.
doi: 10.3788/HPLPB20132511.3060
Abstract:
The KrF excimer laser was studied here. The large area uniform glow discharge was realized by using compact Chang electrode combined ultraviolet spark pre-ionization, and to provide high-voltage discharge with high rising edge, the laser described here used LC inversion and one-stage magnetic switch in excitation circuit. The influence of the laser pulse energy by the work gas content was studied, and in volume ratio of F2/He∶Kr∶Ne = 1.97∶3.18∶94.85 gas mixture at the total gas pressure of 330 kPa, the cross section of the output beam was 30 mm14 mm at 27 kV charging voltage. A maximum output energy of 738 mJ was obtained. And the maximal overall efficiency was up to 2.0% with the charging voltage up to 23 kV.
The KrF excimer laser was studied here. The large area uniform glow discharge was realized by using compact Chang electrode combined ultraviolet spark pre-ionization, and to provide high-voltage discharge with high rising edge, the laser described here used LC inversion and one-stage magnetic switch in excitation circuit. The influence of the laser pulse energy by the work gas content was studied, and in volume ratio of F2/He∶Kr∶Ne = 1.97∶3.18∶94.85 gas mixture at the total gas pressure of 330 kPa, the cross section of the output beam was 30 mm14 mm at 27 kV charging voltage. A maximum output energy of 738 mJ was obtained. And the maximal overall efficiency was up to 2.0% with the charging voltage up to 23 kV.
2013,
25: 3065-3068.
doi: 10.3788/HPLPB20132511.3065
Abstract:
A compact flash radiography accelerator based on fast linear transformer driver(FLTD) and rod-pinch diode(RPD) becomes the research hotspot. A PIC model of the 40-stage FLTD driven RPD was built. The output characteristics of positive and negative polarity of magnetically insulated transmission line(MITL) inner electrode were compared and analyzed, and the properties of electron beam pinch for RPD at the diode voltage of 4 MV was simulated. Simulation results show that the effective electron current proportion in positive polarity MITL was lower than that in negative polarity MITL under the same condition. Under the diode voltage of 4 MV, the electron beam of RPD was pinched well and the electron beam distribution is concentrated in axial direction, and about 38% electrons hit 1.5 mm area around the needle point of the rod.
A compact flash radiography accelerator based on fast linear transformer driver(FLTD) and rod-pinch diode(RPD) becomes the research hotspot. A PIC model of the 40-stage FLTD driven RPD was built. The output characteristics of positive and negative polarity of magnetically insulated transmission line(MITL) inner electrode were compared and analyzed, and the properties of electron beam pinch for RPD at the diode voltage of 4 MV was simulated. Simulation results show that the effective electron current proportion in positive polarity MITL was lower than that in negative polarity MITL under the same condition. Under the diode voltage of 4 MV, the electron beam of RPD was pinched well and the electron beam distribution is concentrated in axial direction, and about 38% electrons hit 1.5 mm area around the needle point of the rod.
2013,
25: 3069-3072.
doi: 10.3788/HPLPB20132511.3069
Abstract:
Experimental results of instability developments of 8 mm tungsten wire array Z-pinches on the 1.5 MA level, 100 ns rise-time Qiangguang-Ⅰfacility are presented. The dominated instability wavelength for imploding 8 mm wire arrays in early ablation regime is (0.20.03) mm, and it grows up to longer wavelength in later implosion and stagnation regime. An m=1 kink, when observed, is always on all frames obtained after peak power. Thus there may be some relation between the occurrence of m=1 and the termination of the rapid rise of the power pulse.
Experimental results of instability developments of 8 mm tungsten wire array Z-pinches on the 1.5 MA level, 100 ns rise-time Qiangguang-Ⅰfacility are presented. The dominated instability wavelength for imploding 8 mm wire arrays in early ablation regime is (0.20.03) mm, and it grows up to longer wavelength in later implosion and stagnation regime. An m=1 kink, when observed, is always on all frames obtained after peak power. Thus there may be some relation between the occurrence of m=1 and the termination of the rapid rise of the power pulse.
2013,
25: 3073-3076.
doi: 10.3788/HPLPB20132511.3073
Abstract:
The support and control system of double-gap series diodes suspension electrode was developed. It consists of support pins, driver circuit and synchronization control part. The support pins are retracted using three small solenoids, and the suspension electrode is accurately located by the three support pins. The withdrawing support pins are driven by a capacitor discharge, and with the driving, the pins can move 30 mm and the suspension electrode can move 125 m in 5 ms. The voltage signal of magnetic coil is used as the synchronization control signal. It triggers the time delay unit DG535, which may export a pulse delayed by 5 ms and trigger the forestage trigger source of Flash-Ⅱ. The Flash-Ⅱ starts at the same time when the support pins withdraw from the diode space. The experimental results indicate that the double-gap series diode is reliable with the suspension electrodes support and control system.
The support and control system of double-gap series diodes suspension electrode was developed. It consists of support pins, driver circuit and synchronization control part. The support pins are retracted using three small solenoids, and the suspension electrode is accurately located by the three support pins. The withdrawing support pins are driven by a capacitor discharge, and with the driving, the pins can move 30 mm and the suspension electrode can move 125 m in 5 ms. The voltage signal of magnetic coil is used as the synchronization control signal. It triggers the time delay unit DG535, which may export a pulse delayed by 5 ms and trigger the forestage trigger source of Flash-Ⅱ. The Flash-Ⅱ starts at the same time when the support pins withdraw from the diode space. The experimental results indicate that the double-gap series diode is reliable with the suspension electrodes support and control system.
