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RSS2011 Vol. 23, No. 08
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2011,
23.
Abstract:
Proximate series solutions of the output pulse waveforms and transmission efficiencies of transmission line with exponential impedance profile have been developed based on distributed-parameter model for typical incident pulses suitable for next generation of Z-pinch plasma drivers. The transmission efficiencies are studied computationally with these solutions for petawatt-class Z-pinch driver’s exponential transmission line taking account of the line’s length and ratio of output impedance to the input as well as the pulse’s shape and parameter. The voltage transmission efficiency increases with the increase of the ratio of output impedance to the input, line length and pulse frequencies; the power transmission efficiency increases with the increase of pulse frequencies and with the dec
Proximate series solutions of the output pulse waveforms and transmission efficiencies of transmission line with exponential impedance profile have been developed based on distributed-parameter model for typical incident pulses suitable for next generation of Z-pinch plasma drivers. The transmission efficiencies are studied computationally with these solutions for petawatt-class Z-pinch driver’s exponential transmission line taking account of the line’s length and ratio of output impedance to the input as well as the pulse’s shape and parameter. The voltage transmission efficiency increases with the increase of the ratio of output impedance to the input, line length and pulse frequencies; the power transmission efficiency increases with the increase of pulse frequencies and with the dec
2011,
23.
Abstract:
The paper investigates the optimization design of power efficiency of exponential impedance transformer with analytic method and numerical method. In numerical calculation, a sine wave voltage with hypothesis of rising edge equivalence is regarded as the forward-going voltage at input of transformer, and its dominant angular frequency is determined by typical rise-time of actual voltage waveforms. At the same time, dissipative loss in water dielectric is neglected. The numerical results of three typical modes of impedance transformation, viz. linear mode, saturation mode and steep mode, are compared. Pivotal factors which affect the power efficiency of exponential impedance transformer are discussed, and a certain extent quantitative range of intermediate variables and accordance coefficie
The paper investigates the optimization design of power efficiency of exponential impedance transformer with analytic method and numerical method. In numerical calculation, a sine wave voltage with hypothesis of rising edge equivalence is regarded as the forward-going voltage at input of transformer, and its dominant angular frequency is determined by typical rise-time of actual voltage waveforms. At the same time, dissipative loss in water dielectric is neglected. The numerical results of three typical modes of impedance transformation, viz. linear mode, saturation mode and steep mode, are compared. Pivotal factors which affect the power efficiency of exponential impedance transformer are discussed, and a certain extent quantitative range of intermediate variables and accordance coefficie
2011,
23.
Abstract:
Detailed demand and optimization design of glow discharge cavity of pseudospark switch are presented. Based on the optimum structure, particle simulation and experimental investigation are given. The particle simulation shows that the designed discharge cavity is a glow discharge cavity and the set up time of glow discharge is approximately 18.5 ns. When glow discharge happens, the cathode voltage drop dominates the primary anode voltage drop. In the cathode voltage drop region, the ion density is larger than the electron density and the net charge density is a constant. The experiment indicates that, the glow discharge cavity works on the left region of Paschen curve; as the gas pressure increases, the discharge voltage drops. When the discharge current is more than 0.14 mA and less than
Detailed demand and optimization design of glow discharge cavity of pseudospark switch are presented. Based on the optimum structure, particle simulation and experimental investigation are given. The particle simulation shows that the designed discharge cavity is a glow discharge cavity and the set up time of glow discharge is approximately 18.5 ns. When glow discharge happens, the cathode voltage drop dominates the primary anode voltage drop. In the cathode voltage drop region, the ion density is larger than the electron density and the net charge density is a constant. The experiment indicates that, the glow discharge cavity works on the left region of Paschen curve; as the gas pressure increases, the discharge voltage drops. When the discharge current is more than 0.14 mA and less than
2011,
23.
Abstract:
In the beginning of magnetic insulated period, loss electron in coaxial vacuum magnetically insulated transmission line(MITL) strikes anode and the bremsstrahlung photons are generated in the mean time. Based on the self-limited flow model, velocity in direction of energy transport, energy spectrum and angular distribution of loss electron are simulated by PIC code, energy spectrum of bremsstrahlung photons as well calculated though Monte Carlo method. Computational results show that the velocity of loss electron is less than 2.998×108 m/s, the angular excursion of electron is not much in a board extent of energy spectrum. These results show an indirect diagnosis of vacuum insulted transmission line working status based on loss electron bremsstrahlung.
In the beginning of magnetic insulated period, loss electron in coaxial vacuum magnetically insulated transmission line(MITL) strikes anode and the bremsstrahlung photons are generated in the mean time. Based on the self-limited flow model, velocity in direction of energy transport, energy spectrum and angular distribution of loss electron are simulated by PIC code, energy spectrum of bremsstrahlung photons as well calculated though Monte Carlo method. Computational results show that the velocity of loss electron is less than 2.998×108 m/s, the angular excursion of electron is not much in a board extent of energy spectrum. These results show an indirect diagnosis of vacuum insulted transmission line working status based on loss electron bremsstrahlung.
2011,
23.
Abstract:
Employing transmission theory of transverse electromagnetic wave, the pulse forming process of spiral pulse forming line(PFL) with outer shield and inner conductor was analyzed. The calculation formulas of characteristic parameters, such as wave impedance, slow-wave coefficient, and flat-topped fluctuate ratio of output pulse, were obtained. This kind spiral PFL is of the same wave impedance and slow-wave coefficient with spiral delayed line. The flat-topped fluctuate ratio of output pulse can be reduced with increasing slow-wave coefficient or load impedance.
Employing transmission theory of transverse electromagnetic wave, the pulse forming process of spiral pulse forming line(PFL) with outer shield and inner conductor was analyzed. The calculation formulas of characteristic parameters, such as wave impedance, slow-wave coefficient, and flat-topped fluctuate ratio of output pulse, were obtained. This kind spiral PFL is of the same wave impedance and slow-wave coefficient with spiral delayed line. The flat-topped fluctuate ratio of output pulse can be reduced with increasing slow-wave coefficient or load impedance.
2011,
23.
Abstract:
According to Maxwell’s equations and heat-conduction differential equation, a mathematical model is developed to describe the distribution of electromagnetic field, inductive eddy current and thermal field for multi-stage induction coilgun. Based on the finite element method(FEM) analysis of electromagnetic and thermal fields, a three-dimensional FEM model is built. When ignoring the inter-stage effect, armature temperature rise calculated in multi-stage is equivalent to multiple armature temperature rise calculated in single-stage. the practical induction heating quenching process is simulated by using ANSYS software. The relationship between the physical parameters of the coilgun and the resulting temperature is considered during the computation. The simulated results indicate that: 1.
According to Maxwell’s equations and heat-conduction differential equation, a mathematical model is developed to describe the distribution of electromagnetic field, inductive eddy current and thermal field for multi-stage induction coilgun. Based on the finite element method(FEM) analysis of electromagnetic and thermal fields, a three-dimensional FEM model is built. When ignoring the inter-stage effect, armature temperature rise calculated in multi-stage is equivalent to multiple armature temperature rise calculated in single-stage. the practical induction heating quenching process is simulated by using ANSYS software. The relationship between the physical parameters of the coilgun and the resulting temperature is considered during the computation. The simulated results indicate that: 1.
2011,
23.
Abstract:
A repetitive linear transformer driver(LTD) based on IGBTs has been tested. The device has four 3 300 V/1 200 A IGBT switches and corresponding drivers, buffer circuits, capacitors, and magnetic core. It can output 4.3 kA current on 0.57 Ω load and achieve a 200 Hz repetition frequency at burst mode. The test result shows that the LTD based on IGBTs can work in repetition mode and the LTD circuit can enhance the operation voltage of IGBTs. Core saturation and reset problems are also analyzed, and an effective method to solve core saturation without reset is proposed.
A repetitive linear transformer driver(LTD) based on IGBTs has been tested. The device has four 3 300 V/1 200 A IGBT switches and corresponding drivers, buffer circuits, capacitors, and magnetic core. It can output 4.3 kA current on 0.57 Ω load and achieve a 200 Hz repetition frequency at burst mode. The test result shows that the LTD based on IGBTs can work in repetition mode and the LTD circuit can enhance the operation voltage of IGBTs. Core saturation and reset problems are also analyzed, and an effective method to solve core saturation without reset is proposed.
2011,
23.
Abstract:
When pulse power device discharge, the voltage to ground rises. It leads to a common mode current from probe’s ground to oscilloscope’s. The output waveform can be affected, and the oscilloscope can be destroyed sometimes. A common mode inductance(CM inductance) made by coaxial cable which enwinds a ferromagnetic core was designed between the probe and oscilloscope. The voltage to ground was calculated based on the equivalent circuit with inductance and resistance of grounded connector. The CM inductance reduced the common mode current and isolated the ground of probe to oscilloscope. The output voltage was measured using a square waveform source with the rise time of 4.8 ns, the rise time of CM inductance output is 7.2 ns. A circuit for testing the isolating impact was designed: The out
When pulse power device discharge, the voltage to ground rises. It leads to a common mode current from probe’s ground to oscilloscope’s. The output waveform can be affected, and the oscilloscope can be destroyed sometimes. A common mode inductance(CM inductance) made by coaxial cable which enwinds a ferromagnetic core was designed between the probe and oscilloscope. The voltage to ground was calculated based on the equivalent circuit with inductance and resistance of grounded connector. The CM inductance reduced the common mode current and isolated the ground of probe to oscilloscope. The output voltage was measured using a square waveform source with the rise time of 4.8 ns, the rise time of CM inductance output is 7.2 ns. A circuit for testing the isolating impact was designed: The out
2011,
23.
Abstract:
One-dimensional theoretical models are obtained for magnetic fields of plasma induced by hypervelocity projectile impacting target, according to existing theories of magnetic fields about laser plasma along with the maxwell’s equation and Faraday’s law of electromagnetic induction. Meanwhile, Based on the partial differential equations of magnetic fields for semi-sphere plasma cloud generated by hypervelocity normal impact, the partial differential equations of magnetic fields are established for plasma cloud in the form of part of ellipsoid induced by hypervelocity oblique impact in cylindrical coordinate system. Magnetic induction intensity measurement is carried out with magnetic coils through hypervelocity impact experiment. Experimental results and model prediction show that the mod
One-dimensional theoretical models are obtained for magnetic fields of plasma induced by hypervelocity projectile impacting target, according to existing theories of magnetic fields about laser plasma along with the maxwell’s equation and Faraday’s law of electromagnetic induction. Meanwhile, Based on the partial differential equations of magnetic fields for semi-sphere plasma cloud generated by hypervelocity normal impact, the partial differential equations of magnetic fields are established for plasma cloud in the form of part of ellipsoid induced by hypervelocity oblique impact in cylindrical coordinate system. Magnetic induction intensity measurement is carried out with magnetic coils through hypervelocity impact experiment. Experimental results and model prediction show that the mod
2011,
23.
Abstract:
A study is presented on the potential profile between planar plane capacitors by constructing electronic spread launch model and analytically solving Poisson equation. The results show that electron beam introduces periodic and non-periodic perturbation to vacuum potential without electron beam. Non-periodic perturbation prevails because the overall effect of periodic perturbation is zero. When the launch angle varies from 0° to 90°, four perturbation peaks take on and beside them electron beam has no impact on vacuum potential, which provide a theoretical explanation for MICHELLE’s nine-particle launch model and a guide for mesh refinement choice when a code is developed.
A study is presented on the potential profile between planar plane capacitors by constructing electronic spread launch model and analytically solving Poisson equation. The results show that electron beam introduces periodic and non-periodic perturbation to vacuum potential without electron beam. Non-periodic perturbation prevails because the overall effect of periodic perturbation is zero. When the launch angle varies from 0° to 90°, four perturbation peaks take on and beside them electron beam has no impact on vacuum potential, which provide a theoretical explanation for MICHELLE’s nine-particle launch model and a guide for mesh refinement choice when a code is developed.
2011,
23.
Abstract:
BB84 phase encoding quantum key distribution systems can distribute shared secret keys between remote communication parties via optic fiber channel with provable security. However, performance of these systems usually suffers from the phase shift in realistic running environment. The existing active phase compensation schemes for these systems have to break the key distribution process to measure phase drift parameters, leading to decrease the final key generation rate of system. A new uninterrupted scheme is proposed to address this problem. The proposed scheme allows the system to run phase compensation process and key distribution process simultaneously by collecting and analyzing the quantum bits with incompatible basis during the quantum key distribution process, which is supposed to
BB84 phase encoding quantum key distribution systems can distribute shared secret keys between remote communication parties via optic fiber channel with provable security. However, performance of these systems usually suffers from the phase shift in realistic running environment. The existing active phase compensation schemes for these systems have to break the key distribution process to measure phase drift parameters, leading to decrease the final key generation rate of system. A new uninterrupted scheme is proposed to address this problem. The proposed scheme allows the system to run phase compensation process and key distribution process simultaneously by collecting and analyzing the quantum bits with incompatible basis during the quantum key distribution process, which is supposed to
2011,
23.
Abstract:
Fusion reaction rate is an important parameter for measuring compression during the implosion in inertial confinement fusion experiment. We have developed a system for fusion reaction history measurement with high temporal resolution. The system is composed of plastic scintillator and nose cone, optical system and streak camera. We have applied this system on the SG-Ⅲ prototype for fusion reaction rate measuring. For the first time, fusion reaction rate history have been measured for deuterium-tritium filled targets with netrons yields about 1010. We have anatomized possible influence factor during fusion reaction rate measuring. It indicates that the instrument measures fusion reaction bang time at temporal resolutions as low as 30 ps.
Fusion reaction rate is an important parameter for measuring compression during the implosion in inertial confinement fusion experiment. We have developed a system for fusion reaction history measurement with high temporal resolution. The system is composed of plastic scintillator and nose cone, optical system and streak camera. We have applied this system on the SG-Ⅲ prototype for fusion reaction rate measuring. For the first time, fusion reaction rate history have been measured for deuterium-tritium filled targets with netrons yields about 1010. We have anatomized possible influence factor during fusion reaction rate measuring. It indicates that the instrument measures fusion reaction bang time at temporal resolutions as low as 30 ps.
2011,
23.
Abstract:
This paper presents an improved constrained conjugate gradient reconstruction algorithm for flash radiographic image with low signal-to-noise ratio. A new preconditioned method is consummated which can more accurately reconstruct image’s axis of symmetry. The new convergence criterion and the substitution of relaxation step for optimal step in the one-dimension search are adopted to ensure the reconstruction accuracy and shorten the reconstruction time simultaneously. The numerical experiment results show that the improved algorithm has better general performance in iteration time and reconstruction quality compared with the original constrained conjugate gradient algorithm.
This paper presents an improved constrained conjugate gradient reconstruction algorithm for flash radiographic image with low signal-to-noise ratio. A new preconditioned method is consummated which can more accurately reconstruct image’s axis of symmetry. The new convergence criterion and the substitution of relaxation step for optimal step in the one-dimension search are adopted to ensure the reconstruction accuracy and shorten the reconstruction time simultaneously. The numerical experiment results show that the improved algorithm has better general performance in iteration time and reconstruction quality compared with the original constrained conjugate gradient algorithm.
2011,
23.
Abstract:
Analytic method is employed to simulate courses of electronic transportation, collision and secondary emission in a MCP single channel. With the use of commercially available software Lorentz-2D, we obtain such curves as initial energy distribution of secondary electrons, electron energy distribution just before colliding with the channel wall, and electron transit time distribution. These simulation results can serve as references when developing a new framing camera or trying to improve its performance. MCP sensitivity is measured, compared with simulation results, it is found that first collision will actually affect the gain of MCP. Qualitative analysis shows that parameters like bias voltage make significant impacts on the depth of first collision. According to what is observed in sim
Analytic method is employed to simulate courses of electronic transportation, collision and secondary emission in a MCP single channel. With the use of commercially available software Lorentz-2D, we obtain such curves as initial energy distribution of secondary electrons, electron energy distribution just before colliding with the channel wall, and electron transit time distribution. These simulation results can serve as references when developing a new framing camera or trying to improve its performance. MCP sensitivity is measured, compared with simulation results, it is found that first collision will actually affect the gain of MCP. Qualitative analysis shows that parameters like bias voltage make significant impacts on the depth of first collision. According to what is observed in sim
2011,
23.
Abstract:
Single event effects (SEEs) test results on a static random access memory (SRAM)-based FPGA with 100 k system gates using californium-252 (252Cf) and the HI-13 tandem-accelerator are presented. The results including the static single event upset (SEU) cross-sections and the linear energy transfer (LET) threshold of single event latchup (SEL) were quantitatively compared and analyzed. The results showed that the SEU cross-sections using 252Cf were an order of magnitude less than the ones using the accelerator. SEL was not observed when the FPGA was exposed to the 252Cf, while SEL LET threshold could be measured when using the heavy-ion accelerator. Therefore, 252Cf is not an ideal radioactive source to test SEL of CMOS circuits fabricated with advanced technologies for experimental simulati
Single event effects (SEEs) test results on a static random access memory (SRAM)-based FPGA with 100 k system gates using californium-252 (252Cf) and the HI-13 tandem-accelerator are presented. The results including the static single event upset (SEU) cross-sections and the linear energy transfer (LET) threshold of single event latchup (SEL) were quantitatively compared and analyzed. The results showed that the SEU cross-sections using 252Cf were an order of magnitude less than the ones using the accelerator. SEL was not observed when the FPGA was exposed to the 252Cf, while SEL LET threshold could be measured when using the heavy-ion accelerator. Therefore, 252Cf is not an ideal radioactive source to test SEL of CMOS circuits fabricated with advanced technologies for experimental simulati
2011,
23.
Abstract:
Correct and effective identification of nuclear material is a key part for nuclear weapon’s verification. Based on the nuclear information system constructed with 252Cf spontaneous neutron source, the simulated autocorrelation functions are utilized for identification of different fissile mass with Elman neural network. The experimental results show the trained Elman neural network is able to distinguish the characteristics of autocorrelation function, identify different fissile mass, and the average identification rate reaches 85% and keep average synthesis error smaller than 0.04 with high robustness.
Correct and effective identification of nuclear material is a key part for nuclear weapon’s verification. Based on the nuclear information system constructed with 252Cf spontaneous neutron source, the simulated autocorrelation functions are utilized for identification of different fissile mass with Elman neural network. The experimental results show the trained Elman neural network is able to distinguish the characteristics of autocorrelation function, identify different fissile mass, and the average identification rate reaches 85% and keep average synthesis error smaller than 0.04 with high robustness.
2011,
23.
Abstract:
A method to analyze electric field distribution of the accelerator based on CST and PSpice software is introduced, and the dynamic three-dimensional electric field distribution and voltage of the device are obtained. The models for numerical simulation of the spiral pulse generator are set up, and detailed results are presented. The changing rules of voltage obtained by CST are similar to that by PSpice software. The numerical simulation results indicate that higher electric fields appear at the seams and the joint surface of the spiral bands, and the interior of the dielectric strut.
A method to analyze electric field distribution of the accelerator based on CST and PSpice software is introduced, and the dynamic three-dimensional electric field distribution and voltage of the device are obtained. The models for numerical simulation of the spiral pulse generator are set up, and detailed results are presented. The changing rules of voltage obtained by CST are similar to that by PSpice software. The numerical simulation results indicate that higher electric fields appear at the seams and the joint surface of the spiral bands, and the interior of the dielectric strut.
2011,
23.
Abstract:
To realize digital phase control of subharmonic buncher, a low level radio frequency control system using down converter, IQ modulator and demodulator techniques, and commercial PXI system, was developed on the platform of LabVIEW. A single-neuron adaptive PID(proportional-integral-derivative) control algorithm with ability of self learning was adopted, satisfying the requirements of phase stability. By comparison with the traditional PID algorithm in field testing, the new algorithm has good stability, fast response and strong anti-interference ability.
To realize digital phase control of subharmonic buncher, a low level radio frequency control system using down converter, IQ modulator and demodulator techniques, and commercial PXI system, was developed on the platform of LabVIEW. A single-neuron adaptive PID(proportional-integral-derivative) control algorithm with ability of self learning was adopted, satisfying the requirements of phase stability. By comparison with the traditional PID algorithm in field testing, the new algorithm has good stability, fast response and strong anti-interference ability.
2011,
23.
Abstract:
Chopper is an important equipment in beam distribution system based on time of heavy ion research facility in Lanzhou(HIRFL). This paper introduces its mode analysis system’s architecture and hardware composition, analyzes corresponding software requirements, and designs the mode analysis program using multithreading technology. Firstly the program reads mode pulse data of chopper from data acquisition card by NI-DAQmx function, then uses the data for further analysis, and finally sends corresponding work mode control instruction to chopper controller through TCP/IP protocol. The designed program meets system requirements, realizing the function of chopper mode automatic conversion, and has passed the field test.
Chopper is an important equipment in beam distribution system based on time of heavy ion research facility in Lanzhou(HIRFL). This paper introduces its mode analysis system’s architecture and hardware composition, analyzes corresponding software requirements, and designs the mode analysis program using multithreading technology. Firstly the program reads mode pulse data of chopper from data acquisition card by NI-DAQmx function, then uses the data for further analysis, and finally sends corresponding work mode control instruction to chopper controller through TCP/IP protocol. The designed program meets system requirements, realizing the function of chopper mode automatic conversion, and has passed the field test.
2011,
23.
Abstract:
Spectrum of excited electron beam position was analyzed to determine tune value and quality factor in Shanghai Synchrotron Radiation Facility(SSRF). Vertical impedance and transverse damping rate of SSRF storage ring were educed. In light of these results, sources of beam instability are discussed and characteristics of the motion of excited single bunch are presented. Frequency response function of RLC circuit was used to fit peaks in the spectrum of beam position signal. Based on the fitting results, quality factor, which represents damping state of the motion, dispersion of frequency, and degree of instability, was acquired. Experiment results show that, the correlation of fitted data and original data can be up to 98%, and the profile of fitted figure is quite similar to original one,
Spectrum of excited electron beam position was analyzed to determine tune value and quality factor in Shanghai Synchrotron Radiation Facility(SSRF). Vertical impedance and transverse damping rate of SSRF storage ring were educed. In light of these results, sources of beam instability are discussed and characteristics of the motion of excited single bunch are presented. Frequency response function of RLC circuit was used to fit peaks in the spectrum of beam position signal. Based on the fitting results, quality factor, which represents damping state of the motion, dispersion of frequency, and degree of instability, was acquired. Experiment results show that, the correlation of fitted data and original data can be up to 98%, and the profile of fitted figure is quite similar to original one,
2011,
23.
Abstract:
High power microwave vacuum electron devices can work at high frequency, high peak and average power. They have been widely used in military and civil microwave electron systems, such as radar, communication, countermeasure, TV broadcast, particle accelerators, plasma heating devices of fusion, microwave sensing and microwave heating. In scientific research, high power microwave vacuum electron devices are used mainly on high energy particle accelerator and fusion research. The devices include high peak power klystron, CW and long pulse high power klystron, multi-beam klystron, and high power gyrotron. In national economy, high power microwave vacuum electron devices are used mainly on weather and navigation radar, medical and radiation accelerator, TV broadcast and communication system. T
High power microwave vacuum electron devices can work at high frequency, high peak and average power. They have been widely used in military and civil microwave electron systems, such as radar, communication, countermeasure, TV broadcast, particle accelerators, plasma heating devices of fusion, microwave sensing and microwave heating. In scientific research, high power microwave vacuum electron devices are used mainly on high energy particle accelerator and fusion research. The devices include high peak power klystron, CW and long pulse high power klystron, multi-beam klystron, and high power gyrotron. In national economy, high power microwave vacuum electron devices are used mainly on weather and navigation radar, medical and radiation accelerator, TV broadcast and communication system. T
2011,
23.
Abstract:
Three-dimensional flow governing functions and the paraxial wave function are solved within whole laser cavity for the study of supersonic chemical oxygen-iodine lasers. A suitable computational method is developed to improve compatibility, effectiveness of data communication, and convergence performance for the coupling of computational fluid dynamics and computational optics. The coupled simulation can provide detailed information about the three-dimensional mixing flow in the cavity, the diffraction of resonant optical field, the influence of laser extraction upon flow fields, and the intensity and phase distribution of laser output.
Three-dimensional flow governing functions and the paraxial wave function are solved within whole laser cavity for the study of supersonic chemical oxygen-iodine lasers. A suitable computational method is developed to improve compatibility, effectiveness of data communication, and convergence performance for the coupling of computational fluid dynamics and computational optics. The coupled simulation can provide detailed information about the three-dimensional mixing flow in the cavity, the diffraction of resonant optical field, the influence of laser extraction upon flow fields, and the intensity and phase distribution of laser output.
2011,
23.
Abstract:
The reflectance of 30CrMnSiA carbon steel under laser irradiation in 20 Pa air, 1 000 Pa air, 1 000 Pa oxygen gas and 105 Pa air was obtained by integrating sphere absolute measurement method, and corresponding temperature history curves were got. The results show that the initial reflectance of material in air increases with the pressure varying from 20 Pa to 105 Pa. The change of reflectance is slower and the inflexion temperature of reflectance change is higher in oxygen-deficient environment than those in oxygen-enriched environment. Additionally, in oxygen-enriched environment, the rapid oxidation reaction of material after heating is in favor of laser energy absorption. For given temperature of material, the reflectance of material is different in different irradiation environments.
The reflectance of 30CrMnSiA carbon steel under laser irradiation in 20 Pa air, 1 000 Pa air, 1 000 Pa oxygen gas and 105 Pa air was obtained by integrating sphere absolute measurement method, and corresponding temperature history curves were got. The results show that the initial reflectance of material in air increases with the pressure varying from 20 Pa to 105 Pa. The change of reflectance is slower and the inflexion temperature of reflectance change is higher in oxygen-deficient environment than those in oxygen-enriched environment. Additionally, in oxygen-enriched environment, the rapid oxidation reaction of material after heating is in favor of laser energy absorption. For given temperature of material, the reflectance of material is different in different irradiation environments.
2011,
23.
Abstract:
Amplified spontaneous emission(ASE) and parasitic oscillation in laser resonators exhibit distinct physical properties. An analytic method is employed to find eigenmodes of disk medium. These modes processes some non-trivial dispersion relations, which allow few stable longitudinal modes only. It decreases amplifying rate of parasitic oscillation in mode competition with main laser. A numerical model is further proposed to perform (3+1) dimensional simulations. Ray tracing method, together with finite-difference in time domain and Fox-Li type iteration, are used to solve a set of coupled equations. Transverse mode competition between ASE/parasitic oscillations and main laser increases threshold to establish laser oscillation and decreases output power as well. Time evolution of laser outpu
Amplified spontaneous emission(ASE) and parasitic oscillation in laser resonators exhibit distinct physical properties. An analytic method is employed to find eigenmodes of disk medium. These modes processes some non-trivial dispersion relations, which allow few stable longitudinal modes only. It decreases amplifying rate of parasitic oscillation in mode competition with main laser. A numerical model is further proposed to perform (3+1) dimensional simulations. Ray tracing method, together with finite-difference in time domain and Fox-Li type iteration, are used to solve a set of coupled equations. Transverse mode competition between ASE/parasitic oscillations and main laser increases threshold to establish laser oscillation and decreases output power as well. Time evolution of laser outpu
2011,
23.
Abstract:
Aiming at the shortcomings of laser point to point communication, the assumption of building the communication networks by laser diffusion from sea surface is come up with according to the need of real sea battle. The energy distribution characteristics of scattered field is studied using forward-backward method(FBM) combined with Green spectral acceleration algorithm (SAA). The accurate 2D laser scattering coefficients from sea surface are obtained and the results are verified by experiments. The results showed that the energy scattered from sea surface are concentrated in the forward zone, less in the backward zone, and attenuated fast in the edges of the scattered field. The feasibility of building communication network by laser diffusion from sea surface among vessels is illustrated. A
Aiming at the shortcomings of laser point to point communication, the assumption of building the communication networks by laser diffusion from sea surface is come up with according to the need of real sea battle. The energy distribution characteristics of scattered field is studied using forward-backward method(FBM) combined with Green spectral acceleration algorithm (SAA). The accurate 2D laser scattering coefficients from sea surface are obtained and the results are verified by experiments. The results showed that the energy scattered from sea surface are concentrated in the forward zone, less in the backward zone, and attenuated fast in the edges of the scattered field. The feasibility of building communication network by laser diffusion from sea surface among vessels is illustrated. A
2011,
23.
Abstract:
In order to analyze the effect of scattering loss on optical transmittance of transparent laser ceramics, the paper uses zeroth-order lognormal distributions(ZOLDs) to describe the scattering loss at different pore sizes and porosities, and introduces the definition of secondary phase volume ratio to calculate the number of scattering particles. The effects of scattering loss due to pores, grain boundary secondary phases and grain boundary surface roughness on optical transmittance of transparent laser ceramics are discussed based on the theories of Mie scattering, Rayleigh scattering and total integrated scatter(TIS). The results show that the transmittance is influenced significantly by porosity, while pore size distributions determine the trend of the envelope of optical transmittance;
In order to analyze the effect of scattering loss on optical transmittance of transparent laser ceramics, the paper uses zeroth-order lognormal distributions(ZOLDs) to describe the scattering loss at different pore sizes and porosities, and introduces the definition of secondary phase volume ratio to calculate the number of scattering particles. The effects of scattering loss due to pores, grain boundary secondary phases and grain boundary surface roughness on optical transmittance of transparent laser ceramics are discussed based on the theories of Mie scattering, Rayleigh scattering and total integrated scatter(TIS). The results show that the transmittance is influenced significantly by porosity, while pore size distributions determine the trend of the envelope of optical transmittance;
2011,
23.
Abstract:
The calibration of radiochromic films (HD-810) irradiated by protons with different energies has been carried out on the tandem electrostatic accelerator. The optical densities of the irradiated films were obtained using spectrophotometer and commercial flatbed scanner, and the curves of the net optical densities versus dose were acquired. The results of calibration corroborate that, in a certain range of absorbed dose, the net optical densities vary linearly with absorbed doses of the sensitive layer and are independent on the energy of protons. The wavelength of light used to measure the optical density has great effect on the linear range, and the linear range of green light (532 nm) is obviously larger than that of red light (670 nm).
The calibration of radiochromic films (HD-810) irradiated by protons with different energies has been carried out on the tandem electrostatic accelerator. The optical densities of the irradiated films were obtained using spectrophotometer and commercial flatbed scanner, and the curves of the net optical densities versus dose were acquired. The results of calibration corroborate that, in a certain range of absorbed dose, the net optical densities vary linearly with absorbed doses of the sensitive layer and are independent on the energy of protons. The wavelength of light used to measure the optical density has great effect on the linear range, and the linear range of green light (532 nm) is obviously larger than that of red light (670 nm).
2011,
23.
Abstract:
Diffractive properties of the continuous phase type zone plate with Gaussian beam incidence were analyzed based on Rayleigh-Sommerfeld diffraction theory. The simulations of intensity distribution on the focal plane and the optic axis were completed using Matlab. Diffraction fields of the zone plate with continuous phase were analyzed. The effects of the parameters of the incident beam on the diffraction field were discussed. The results indicate that the continuous phase type zone plate can focus Gaussian beam with high diffraction efficiency. Diffraction law of the continuous phase type zone plate is similar to that of thin lens. If the waist location is optimized, the diffraction efficiency will be larger than 85%. Compared with the plane wave incidence, when the Gaussian beam is incide
Diffractive properties of the continuous phase type zone plate with Gaussian beam incidence were analyzed based on Rayleigh-Sommerfeld diffraction theory. The simulations of intensity distribution on the focal plane and the optic axis were completed using Matlab. Diffraction fields of the zone plate with continuous phase were analyzed. The effects of the parameters of the incident beam on the diffraction field were discussed. The results indicate that the continuous phase type zone plate can focus Gaussian beam with high diffraction efficiency. Diffraction law of the continuous phase type zone plate is similar to that of thin lens. If the waist location is optimized, the diffraction efficiency will be larger than 85%. Compared with the plane wave incidence, when the Gaussian beam is incide
2011,
23.
Abstract:
Based on characteristics of image-relaying structure in high power excimer MOPA laser system, simulation and analysis software of targeting beam’s barycenter stability was designed by using LABVIEW and MATLAB. Simulation was made to measured results of every optical component in laboratory environment. Simulation and validation of budget values for optical components was and optimization of error budget of system was accomplished via post-allocation for several times. It is shown that targeting beam’s barycenter stability in the condition of current laboratory environment can’t satisfy needs and index of high demand optical components can be allotted to 1.7 μrad when index of low demand optical components have some stability margin. These results can provide a guide to construction of
Based on characteristics of image-relaying structure in high power excimer MOPA laser system, simulation and analysis software of targeting beam’s barycenter stability was designed by using LABVIEW and MATLAB. Simulation was made to measured results of every optical component in laboratory environment. Simulation and validation of budget values for optical components was and optimization of error budget of system was accomplished via post-allocation for several times. It is shown that targeting beam’s barycenter stability in the condition of current laboratory environment can’t satisfy needs and index of high demand optical components can be allotted to 1.7 μrad when index of low demand optical components have some stability margin. These results can provide a guide to construction of
2011,
23.
Abstract:
In experimental facility of cylindrical gain generator assembly for HF chemical laser, primary diluent He is injected into combustor from two different regions. Some of He is injected by D2 jet orifices after being premixed with D2. The other of He is injected by backward He jet orifices at back end of primary nozzle blade. The effect of changing mass flow rate of onward He or backward He on laser’s characteristics is studied by a couple of lasing experiments. The experimental results show that, as compared with changing mass flow rate of onward He, changing mass flow rate of backward He can acquire much higher output power and better ignition stability. When primary diluent ratio is required to be increased, changing mass flow rate of backward He should be given priority.
In experimental facility of cylindrical gain generator assembly for HF chemical laser, primary diluent He is injected into combustor from two different regions. Some of He is injected by D2 jet orifices after being premixed with D2. The other of He is injected by backward He jet orifices at back end of primary nozzle blade. The effect of changing mass flow rate of onward He or backward He on laser’s characteristics is studied by a couple of lasing experiments. The experimental results show that, as compared with changing mass flow rate of onward He, changing mass flow rate of backward He can acquire much higher output power and better ignition stability. When primary diluent ratio is required to be increased, changing mass flow rate of backward He should be given priority.
2011,
23.
Abstract:
The laser propagation process can be influenced by atmospheric turbulence. The turbulence could bring on the degradation of the laser beam correlation, induce beam wandering and spreading. However, the experimental data obtained from the outer field research about laser propagation in turbulence is always influenced inevitably by many factors. A turbulence simulating device in inner field for studying the process of laser propagation in atmospheric turbulence could avoid the disturbance of these factors for studying. A physical turbulence simulation system using random phase plates based on Kolmogorov spectrum was designed to complete a spot wander experiment of laser propagation. The formula of instantaneous wander variance and beam expansion variance are given, which could be used to det
The laser propagation process can be influenced by atmospheric turbulence. The turbulence could bring on the degradation of the laser beam correlation, induce beam wandering and spreading. However, the experimental data obtained from the outer field research about laser propagation in turbulence is always influenced inevitably by many factors. A turbulence simulating device in inner field for studying the process of laser propagation in atmospheric turbulence could avoid the disturbance of these factors for studying. A physical turbulence simulation system using random phase plates based on Kolmogorov spectrum was designed to complete a spot wander experiment of laser propagation. The formula of instantaneous wander variance and beam expansion variance are given, which could be used to det
2011,
23.
Abstract:
Scattered radiation, which seriously decreases the precision of image reconstruction in high energy flash X-ray radiography, can be largely diminished by anti-scatter grid. The design aim of MeV anti-scatter grid is firstly presented, and the radiographic system layout and the imaging system are given using theoretic analysis. Then parameters of anti-scatter grid, such as the total thickness, aperture and space between holes, and the thickness of W thin foil with small holes, are detailed using Monte Carlo simulation and analysis. Effects of the machining error and imperfect alignments of radiographic components on the performance of MeV anti-scatter grid are also discussed, and design parameters of the prototype of anti-scatter grid are presented. With the designed anti-scatter grid, the
Scattered radiation, which seriously decreases the precision of image reconstruction in high energy flash X-ray radiography, can be largely diminished by anti-scatter grid. The design aim of MeV anti-scatter grid is firstly presented, and the radiographic system layout and the imaging system are given using theoretic analysis. Then parameters of anti-scatter grid, such as the total thickness, aperture and space between holes, and the thickness of W thin foil with small holes, are detailed using Monte Carlo simulation and analysis. Effects of the machining error and imperfect alignments of radiographic components on the performance of MeV anti-scatter grid are also discussed, and design parameters of the prototype of anti-scatter grid are presented. With the designed anti-scatter grid, the
2011,
23.
Abstract:
With approximation of little amplitude aberration modes, we present theoretical analysis and explore validate conditions of MBWFS. We also compare and analysis three ways of extracting information from intensity distribution in measurement plane and three definitions of sensor output signals, respectively. Performance difference of sensor to detect single and multiple modes is numerically studied in terms of Zernike aberration modes. The results show that, sensor sensitivity indicates aberration modes component and amplitude included in test wavefront, which are identical or relevant with those in bias-screen plate, but sensitivity to each Zernike aberration mode is different, and furthermore, irrelevant aberration modes can affect both output signals and sensitivity.
With approximation of little amplitude aberration modes, we present theoretical analysis and explore validate conditions of MBWFS. We also compare and analysis three ways of extracting information from intensity distribution in measurement plane and three definitions of sensor output signals, respectively. Performance difference of sensor to detect single and multiple modes is numerically studied in terms of Zernike aberration modes. The results show that, sensor sensitivity indicates aberration modes component and amplitude included in test wavefront, which are identical or relevant with those in bias-screen plate, but sensitivity to each Zernike aberration mode is different, and furthermore, irrelevant aberration modes can affect both output signals and sensitivity.
2011,
23.
Abstract:
Water cooling micro-channel heat sink for high power laser diode was designed. And designs were simulated with computational fluid dynamics(CFD) and numerical heat transfer(NHT) methods. Influences of the size, number of cooling channels and flow rate of cooling water to temperature level and flow resistance characters of the heat sink were discussed. The performance with a diamond heat spreader was numerical calculated. The results indicate that diamond heat spreader can play an important role on decreasing temperature of the heat sink.
Water cooling micro-channel heat sink for high power laser diode was designed. And designs were simulated with computational fluid dynamics(CFD) and numerical heat transfer(NHT) methods. Influences of the size, number of cooling channels and flow rate of cooling water to temperature level and flow resistance characters of the heat sink were discussed. The performance with a diamond heat spreader was numerical calculated. The results indicate that diamond heat spreader can play an important role on decreasing temperature of the heat sink.
2011,
23.
Abstract:
An all-fiber-configuration master oscillator power amplification(MOPA)-structured high power laser has been constructed all with China-made components. A maximum output of 52.5 W centered at 1 080 nm is achieved at the launched pump power of 75 W. The optical to optical conversion efficiency is 70%. The experimental results have demonstrated the potential to achieve higher output power with more powerful pump source.
An all-fiber-configuration master oscillator power amplification(MOPA)-structured high power laser has been constructed all with China-made components. A maximum output of 52.5 W centered at 1 080 nm is achieved at the launched pump power of 75 W. The optical to optical conversion efficiency is 70%. The experimental results have demonstrated the potential to achieve higher output power with more powerful pump source.
2011,
23.
Abstract:
An all-solid-state laser diode(LD)-side-pumped Nd:YAG ultraviolet(UV) laser at 266 nm is reported, which is based on fourth harmonic generation and adopts zigzag cavity structure. The type-Ⅰ critical phase matched LBO and BBO crystals are used as the second harmonic and fourth harmonic generation crystals, respectively, and 2.1 W UV laser of 266 nm with single pulse energy of 420 μJ is obtained at the pulse repetition rate of 5 kHz with the conversion efficiency of 13.13% from green to ultraviolet light. With V-shaped cavity configuration, only 305 mW 266 nm UV laser is obtained under the same condition.
An all-solid-state laser diode(LD)-side-pumped Nd:YAG ultraviolet(UV) laser at 266 nm is reported, which is based on fourth harmonic generation and adopts zigzag cavity structure. The type-Ⅰ critical phase matched LBO and BBO crystals are used as the second harmonic and fourth harmonic generation crystals, respectively, and 2.1 W UV laser of 266 nm with single pulse energy of 420 μJ is obtained at the pulse repetition rate of 5 kHz with the conversion efficiency of 13.13% from green to ultraviolet light. With V-shaped cavity configuration, only 305 mW 266 nm UV laser is obtained under the same condition.
2011,
23.
Abstract:
Based on diffraction theory, this paper deduces the equation of coherent beam intensity in far-field of with multi-core double-clad fiber. The effects of different fiber core arrays, especially single ring array, multilayer rings array, rectangular array and hexagon array, on the final quality of beam combination are investigated. The effects of different parameters including core diameter, core space, the distance between output plane and diffraction plane and wavelength are also studied. Numerical results demonstrate that, for given core number, single ring array is the best scheme among the above four core array in order to realize high quality beam combination, and the next one is rectangular array. Increasing core number can increase cross section utilization ratio，thus producing hig
Based on diffraction theory, this paper deduces the equation of coherent beam intensity in far-field of with multi-core double-clad fiber. The effects of different fiber core arrays, especially single ring array, multilayer rings array, rectangular array and hexagon array, on the final quality of beam combination are investigated. The effects of different parameters including core diameter, core space, the distance between output plane and diffraction plane and wavelength are also studied. Numerical results demonstrate that, for given core number, single ring array is the best scheme among the above four core array in order to realize high quality beam combination, and the next one is rectangular array. Increasing core number can increase cross section utilization ratio，thus producing hig
2011,
23.
Abstract:
Generation of bottle beam by modulating the spatial coherent coefficient of partially coherent beams is investigated. Based on the theorem of van Cittert-Zernike and scalar diffractive theory, partially coherent beam with particular coherent coefficient is constructed. And focused properties of this kind of partially coherent beam is studied. Based on theoretical results, an optical system to achieve the special partially coherent beams, and focus partially coherent beams with a thin lens is designed. The results indicate that particular partially coherent beams can be converted into bottle beam after focusing by thin lens. Moreover, the influence of parameters of optical system and focus length of thin lens on construction of the bottle beam is studied. The greater of lens focal length an
Generation of bottle beam by modulating the spatial coherent coefficient of partially coherent beams is investigated. Based on the theorem of van Cittert-Zernike and scalar diffractive theory, partially coherent beam with particular coherent coefficient is constructed. And focused properties of this kind of partially coherent beam is studied. Based on theoretical results, an optical system to achieve the special partially coherent beams, and focus partially coherent beams with a thin lens is designed. The results indicate that particular partially coherent beams can be converted into bottle beam after focusing by thin lens. Moreover, the influence of parameters of optical system and focus length of thin lens on construction of the bottle beam is studied. The greater of lens focal length an
2011,
23.
Abstract:
A narrow-linewidth high power Yb-doped fiber laser in all-fiber format is set up. The seed laser has an output power of more than 40 mW with linewidth narrower than 100 MHz. The fiber laser employs three-stage master oscillator power amplifier(MOPA) configuration. It outputs 334 W narrow-linewidth laser when pumped with a total power of 405 W in the main amplifier. The optical-to-optical conversion efficiency is 82.4%. Presently, the output power is limited by the pump power. It can be predicted that the laser power can be further scaled with increased available pump power.
A narrow-linewidth high power Yb-doped fiber laser in all-fiber format is set up. The seed laser has an output power of more than 40 mW with linewidth narrower than 100 MHz. The fiber laser employs three-stage master oscillator power amplifier(MOPA) configuration. It outputs 334 W narrow-linewidth laser when pumped with a total power of 405 W in the main amplifier. The optical-to-optical conversion efficiency is 82.4%. Presently, the output power is limited by the pump power. It can be predicted that the laser power can be further scaled with increased available pump power.
2011,
23.
Abstract:
Erbium hydride films were prepared via two steps. In the process, the erbium films fabricated via rolling reacted with hydrogen under high temperature and the hydrogenation process should last more than 24 hours for quality consideration. The hydrogen pressure and the reaction temperature play key roles in the fabrication process, and fine erbium hydride films can be obtained under proper control of the two factors when the hydrogenation process and the release of the stress generated in hydrogenation are both slow. The derived fine erbium hydride films with thickness of 5 to 15 μm have been used as the targets in experiments to produce high energy proton beams bringing good experimental results.
Erbium hydride films were prepared via two steps. In the process, the erbium films fabricated via rolling reacted with hydrogen under high temperature and the hydrogenation process should last more than 24 hours for quality consideration. The hydrogen pressure and the reaction temperature play key roles in the fabrication process, and fine erbium hydride films can be obtained under proper control of the two factors when the hydrogenation process and the release of the stress generated in hydrogenation are both slow. The derived fine erbium hydride films with thickness of 5 to 15 μm have been used as the targets in experiments to produce high energy proton beams bringing good experimental results.
2011,
23.
Abstract:
Using high energy X-ray defocus phase contrast imaging on polystyrene(PS) microspheres, the contrast of the edge of tiny bubbles (about a few micrometers in diameter) in the sphere’s wall are effectively enhanced, where the density gradient is relatively larger, and thus the bubbles will be highlighted on the image of microsphere which has overall smooth gray scale. The contrast causing and related factors are analyzed and discussed. The experiments conducted use micro-focal spot X-ray tube and CCD as the light source and detector, the derived image resolution is better than 2 μm, and the rapid defect detection of PS shells is achieved at the X-ray energy of 20 to 30 keV, providing a fast and effectiving means for monitoring of microspheres preparation process.
Using high energy X-ray defocus phase contrast imaging on polystyrene(PS) microspheres, the contrast of the edge of tiny bubbles (about a few micrometers in diameter) in the sphere’s wall are effectively enhanced, where the density gradient is relatively larger, and thus the bubbles will be highlighted on the image of microsphere which has overall smooth gray scale. The contrast causing and related factors are analyzed and discussed. The experiments conducted use micro-focal spot X-ray tube and CCD as the light source and detector, the derived image resolution is better than 2 μm, and the rapid defect detection of PS shells is achieved at the X-ray energy of 20 to 30 keV, providing a fast and effectiving means for monitoring of microspheres preparation process.
2011,
23.
Abstract:
Implosions with nested tungsten wire array were performed at the Angara-5-1 facility in Russian Research Centre. The experimental results of nested tungsten wire array are compared with those of single array. Radiation parameters of nested array are discussed based on four different dynamic models. When the implosions of outer and inner wire arrays are synchronized, the relatively uniform distribution of inner layer plasma will improve the uniformity of outer layer plasma. As compared with single array, nested array has an increase of 32% in X-ray radiation power.
Implosions with nested tungsten wire array were performed at the Angara-5-1 facility in Russian Research Centre. The experimental results of nested tungsten wire array are compared with those of single array. Radiation parameters of nested array are discussed based on four different dynamic models. When the implosions of outer and inner wire arrays are synchronized, the relatively uniform distribution of inner layer plasma will improve the uniformity of outer layer plasma. As compared with single array, nested array has an increase of 32% in X-ray radiation power.
2011,
23.
Abstract:
Based on volume sum rule for computing equation of state(EOS) of mixture materials, a physical model is proposed to determine mixture temperature. According to equilibrium conditions of component temperatures and pressures, EOS of mixture is calculated using iterations of pressure and density. To verify and validate proposed temperature model, EOS for mixture with H2 and W is calculated and analyzed, and it is shown that proposed temperature model is reasonable. Then EOSs for the following cases, (i) various concentration of H2 and W mixture, (ii) variable single component with fixed concentration, (iii) different temperature and density range, are presented. These results are useful in research of inertial confined fusion and high velocity collision.
Based on volume sum rule for computing equation of state(EOS) of mixture materials, a physical model is proposed to determine mixture temperature. According to equilibrium conditions of component temperatures and pressures, EOS of mixture is calculated using iterations of pressure and density. To verify and validate proposed temperature model, EOS for mixture with H2 and W is calculated and analyzed, and it is shown that proposed temperature model is reasonable. Then EOSs for the following cases, (i) various concentration of H2 and W mixture, (ii) variable single component with fixed concentration, (iii) different temperature and density range, are presented. These results are useful in research of inertial confined fusion and high velocity collision.
2011,
23.
Abstract:
In order to improve the resistance of multilayer dielectric pulse compressor gratings (PCGs) with top layer of HfO2 to laser damage, the residues including carbon fluorinated compounds and metal compounds containing fluorine, which are left on the surface of PCG during ion reactive etching of HfO2 with working gas of CHF3, have been cleaned by Piranha solution (the mixture of 98% H2SO4 and 30% H2O2). The parameters of Piranha solution cleaning, such as cleaning temperature, composition, cleaning time, and times of cleaning, were studied systematically. Scanning electron microscope (SEM) was presented to observe the grooves of PCG and X-ray photoelectron spectroscopy( XPS) was employed to evaluate different elements on the surface of PCG before and after cleaning. The removal mechanism of r
In order to improve the resistance of multilayer dielectric pulse compressor gratings (PCGs) with top layer of HfO2 to laser damage, the residues including carbon fluorinated compounds and metal compounds containing fluorine, which are left on the surface of PCG during ion reactive etching of HfO2 with working gas of CHF3, have been cleaned by Piranha solution (the mixture of 98% H2SO4 and 30% H2O2). The parameters of Piranha solution cleaning, such as cleaning temperature, composition, cleaning time, and times of cleaning, were studied systematically. Scanning electron microscope (SEM) was presented to observe the grooves of PCG and X-ray photoelectron spectroscopy( XPS) was employed to evaluate different elements on the surface of PCG before and after cleaning. The removal mechanism of r
2011,
23.
Abstract:
Based on the experimental result of inducing shock wave in a small-scale short-duration supersonic wind tunnel, this paper illustrated the theory of inducing shock wave that was not only lied on Joule heating effect but also decided by the discharge area thickness of boundary layer. Moreover, the experimental investigation on inducing plasma shock wave in the hypersonic wind tunnel in order to confirm such theory drew the conclusion that under the condition that the boundary layer is very thin the plasma aerodynamic actuation could induce oblique shock wave. This paper discussed the theory of inducing shock wave in these two different conditions and also confirmed the key effect of boundary layer in plasma and shock wave interaction.
Based on the experimental result of inducing shock wave in a small-scale short-duration supersonic wind tunnel, this paper illustrated the theory of inducing shock wave that was not only lied on Joule heating effect but also decided by the discharge area thickness of boundary layer. Moreover, the experimental investigation on inducing plasma shock wave in the hypersonic wind tunnel in order to confirm such theory drew the conclusion that under the condition that the boundary layer is very thin the plasma aerodynamic actuation could induce oblique shock wave. This paper discussed the theory of inducing shock wave in these two different conditions and also confirmed the key effect of boundary layer in plasma and shock wave interaction.
2011,
23.
Abstract:
The target positioning precision of multi-beam laser facility is crucial to future inertial confinement fusion experiments, so the calculation methods have been developed for estimating the target positioning precision. The measurement method of target positioning precision based on the X-ray pinhole camera was presented. The coordinates of target center position determined by microscope and read by X-ray pinhole camera after the shoot on CH target of multi-hole, the conversion relationship of coordinates between target plane and X-ray pinhole camera was established. The template of focal area was acquired after the shoot of focal area target. The match method of template was adopted, and the position coordinates of focal area center were obtained by X-ray pinhole camera. The position of f
The target positioning precision of multi-beam laser facility is crucial to future inertial confinement fusion experiments, so the calculation methods have been developed for estimating the target positioning precision. The measurement method of target positioning precision based on the X-ray pinhole camera was presented. The coordinates of target center position determined by microscope and read by X-ray pinhole camera after the shoot on CH target of multi-hole, the conversion relationship of coordinates between target plane and X-ray pinhole camera was established. The template of focal area was acquired after the shoot of focal area target. The match method of template was adopted, and the position coordinates of focal area center were obtained by X-ray pinhole camera. The position of f
2011,
23.
Abstract:
The lifetime of a laser optics is limited by laser-induced damage and subsequent growth of laser initiated damage area. Morphology and growth of laser-induced damage on polished K9 glass surface and inside of the material have been measured after single-shot laser irradiation at 1 064 nm wavelength and approximately 10 ns pulse duration. Differential interference contrast(DIC) optical microscopy, SEM are used for imaging the damage sites. All of the observed damage is concentrated on the optics surface, and the output surface damage is more visible and serious than input surface. For input surface, plasma produced by laser pulse shields the material and reduces material destruction, symmetrical craterlet and microcrack is produced by ablation effect and laser-supported detonation wave(LSD
The lifetime of a laser optics is limited by laser-induced damage and subsequent growth of laser initiated damage area. Morphology and growth of laser-induced damage on polished K9 glass surface and inside of the material have been measured after single-shot laser irradiation at 1 064 nm wavelength and approximately 10 ns pulse duration. Differential interference contrast(DIC) optical microscopy, SEM are used for imaging the damage sites. All of the observed damage is concentrated on the optics surface, and the output surface damage is more visible and serious than input surface. For input surface, plasma produced by laser pulse shields the material and reduces material destruction, symmetrical craterlet and microcrack is produced by ablation effect and laser-supported detonation wave(LSD
2011,
23.
Abstract:
Intensities of emission spectra of laser-induced alloy-aluminum plasma, with use of neodymium YAG laser (laser pulse energy is 6~10 J), were experimentally studied in air atmosphere. Emission spectra of laser-induced aluminum plasma of 6~10 J energy were obtained. Relationship between spectral line intensity and laser energy were analyzed. Experimental results show that signal intensity of spectral line increases with increasing of laser energy. In addition, half width of spectral line was obtained by Lorentz linear fitting of plasma spectra, in order to calculate electron density. Electron density and signal intensities will decrease gradually with increasing of shock time.
Intensities of emission spectra of laser-induced alloy-aluminum plasma, with use of neodymium YAG laser (laser pulse energy is 6~10 J), were experimentally studied in air atmosphere. Emission spectra of laser-induced aluminum plasma of 6~10 J energy were obtained. Relationship between spectral line intensity and laser energy were analyzed. Experimental results show that signal intensity of spectral line increases with increasing of laser energy. In addition, half width of spectral line was obtained by Lorentz linear fitting of plasma spectra, in order to calculate electron density. Electron density and signal intensities will decrease gradually with increasing of shock time.
2011,
23.
Abstract:
Effects of plasma density and current ramp up rate on runaway electrons is investigated in current ramp-up phase. It is found that higher density and lower current ramp-up rate can reduce generation of runaway electrons in current ramp-up phase, even in current flat-top phase. Low plasma density will result in hard runaway electrons emission. Lower hybrid wave (LHW) can drive plasma current in order to reduce loop voltage and save volt-second product of Tokamak in current ramp-up phase. Runaway electrons can also be restrained because of reduced loop voltage.
Effects of plasma density and current ramp up rate on runaway electrons is investigated in current ramp-up phase. It is found that higher density and lower current ramp-up rate can reduce generation of runaway electrons in current ramp-up phase, even in current flat-top phase. Low plasma density will result in hard runaway electrons emission. Lower hybrid wave (LHW) can drive plasma current in order to reduce loop voltage and save volt-second product of Tokamak in current ramp-up phase. Runaway electrons can also be restrained because of reduced loop voltage.
2011,
23.
Abstract:
The design, measurement technique and experimental results of rotating TE6 2 mode generator are presented. The source includes millimeter wave optical system and open coaxial wave guide system. The millimeter wave optical system consists of pyramid antenna, hyperbolical reflector, parabolic reflector and quasi parabolic reflector. The open coaxial wave guide system contains open coaxial wave guide cavity, cylinder wave guide and output antenna. It is tested by network analyser and millimeter wave near field pattern auto-test system, and the purity of rotating TE6 2 mode at 96.4 GHz is about 97%.
The design, measurement technique and experimental results of rotating TE6 2 mode generator are presented. The source includes millimeter wave optical system and open coaxial wave guide system. The millimeter wave optical system consists of pyramid antenna, hyperbolical reflector, parabolic reflector and quasi parabolic reflector. The open coaxial wave guide system contains open coaxial wave guide cavity, cylinder wave guide and output antenna. It is tested by network analyser and millimeter wave near field pattern auto-test system, and the purity of rotating TE6 2 mode at 96.4 GHz is about 97%.
2011,
23.
Abstract:
With 3D full electromagnetic particle-in-cell code, an X-band coaxial double-gap output cavity of klystron amplifier has been designed and simulated. It is found that the microwave extraction power and efficiency is increased by employing the coaxial double-gap output cavity. The relation between output power and modulation depth of current, and the relation between output power and the distance from electron beam outer radius to drifting wall are obtained. Furthermore, the relation between output power and DC transitional angle is presented. A 1.2 GW averaged power over the oscillator period is generated by simulation with 600 kV electron beam voltage, 5 kA current, 100% modulation depth of current and 1 T leading magnetic field density. The peak frequency is 9.37 GHz and the efficiency i
With 3D full electromagnetic particle-in-cell code, an X-band coaxial double-gap output cavity of klystron amplifier has been designed and simulated. It is found that the microwave extraction power and efficiency is increased by employing the coaxial double-gap output cavity. The relation between output power and modulation depth of current, and the relation between output power and the distance from electron beam outer radius to drifting wall are obtained. Furthermore, the relation between output power and DC transitional angle is presented. A 1.2 GW averaged power over the oscillator period is generated by simulation with 600 kV electron beam voltage, 5 kA current, 100% modulation depth of current and 1 T leading magnetic field density. The peak frequency is 9.37 GHz and the efficiency i
2011,
23.
Abstract:
The chaotic properties of the electromagnetic wave propagation in electrical, large complex cavities are analyzed by semi-classical approximation approach. The random plane wave hypothesis of three dimensional eigen-function is also induced. Based on this hypothesis and the random polarization of wave, the statistical approach to the solution of eigen-electromagnetic field spatial distribution problem establishes the statistical model. Importantly, those are independent of the details of cavity. Moreover, we numerically investigate statistical properties of three-dimensional Sinai microwave cavities, and numerical results are agreed well with those obtained from the statistical model.
The chaotic properties of the electromagnetic wave propagation in electrical, large complex cavities are analyzed by semi-classical approximation approach. The random plane wave hypothesis of three dimensional eigen-function is also induced. Based on this hypothesis and the random polarization of wave, the statistical approach to the solution of eigen-electromagnetic field spatial distribution problem establishes the statistical model. Importantly, those are independent of the details of cavity. Moreover, we numerically investigate statistical properties of three-dimensional Sinai microwave cavities, and numerical results are agreed well with those obtained from the statistical model.
2011,
23.
Abstract:
Three dimensional particle simulation of input cavity for S-band long-pulse high-current RKA is presented. First three-dimensional model of open cavity for input cavity is established and resonant frequency and loaded-Q of open cavity is calculated. Raising the beam voltage and beam current from 600 kV, 5.4 kA to 837 kV, 12.48 kA, three-dimensional Particle-in-cell(PIC) code can run stably for 100 ns. The modulated current of simulation is consistent with experiment result. With the structure unchanged, raising the beam voltage and beam current from 837 kV, 12.48 kA to 900 kV, 16 kA, the code can only run stably for 50 ns because of the mode competition. In order to conquer the mode competition, changing the coupling-hole to symmetric double coupling-hole, the code can run stably for 100ns
Three dimensional particle simulation of input cavity for S-band long-pulse high-current RKA is presented. First three-dimensional model of open cavity for input cavity is established and resonant frequency and loaded-Q of open cavity is calculated. Raising the beam voltage and beam current from 600 kV, 5.4 kA to 837 kV, 12.48 kA, three-dimensional Particle-in-cell(PIC) code can run stably for 100 ns. The modulated current of simulation is consistent with experiment result. With the structure unchanged, raising the beam voltage and beam current from 837 kV, 12.48 kA to 900 kV, 16 kA, the code can only run stably for 50 ns because of the mode competition. In order to conquer the mode competition, changing the coupling-hole to symmetric double coupling-hole, the code can run stably for 100ns
2011,
23.
Abstract:
Finite element computation of 2-D magnetic field of solenoid with current has been implemented. It adopted first or second order interpolation based finite element method to solve the 2-D magnetic field of the solenoid. The single solenoid model and the periodic structure model were analyzed and simulated. The results were compared with the results of Ansoft Maxwell 2D. It is shown that, compared with the first order interpolation based finite element method, the second order interpolation one has a faster convergence rate and a better accuracy on the axis of symmetry.
Finite element computation of 2-D magnetic field of solenoid with current has been implemented. It adopted first or second order interpolation based finite element method to solve the 2-D magnetic field of the solenoid. The single solenoid model and the periodic structure model were analyzed and simulated. The results were compared with the results of Ansoft Maxwell 2D. It is shown that, compared with the first order interpolation based finite element method, the second order interpolation one has a faster convergence rate and a better accuracy on the axis of symmetry.
2011,
23.
Abstract:
For the 2.5-dimensional simulation of the whole system from HPM(high power microwave) source to antennas’ radiation, a scheme of finite-difference time-domain(FDTD) near-to-far-field transformation in 2.5-dimensional simulation is proposed based on the simulation of near fields. The closed three-dimensional column surface is got through rotating the output-boundary in the 2.5-dimensional simulation domain about the symmetry axis. The equivalent electric and magnetic currents can be obtained from FDTD near fields on the closed surface with equivalence principle. The far-fields radiated by these currents are then calculated using the radiation field expressions. The examples about far fields of conical-horns excited by circular waveguide TM01 mode or TE01 mode are given. And the results agr
For the 2.5-dimensional simulation of the whole system from HPM(high power microwave) source to antennas’ radiation, a scheme of finite-difference time-domain(FDTD) near-to-far-field transformation in 2.5-dimensional simulation is proposed based on the simulation of near fields. The closed three-dimensional column surface is got through rotating the output-boundary in the 2.5-dimensional simulation domain about the symmetry axis. The equivalent electric and magnetic currents can be obtained from FDTD near fields on the closed surface with equivalence principle. The far-fields radiated by these currents are then calculated using the radiation field expressions. The examples about far fields of conical-horns excited by circular waveguide TM01 mode or TE01 mode are given. And the results agr
2011,
23.
Abstract:
One novel overmode bend circular waveguide is designed and studied. The novel approach is as follows: the circular waveguide TM01 mode is converted to half-circular waveguide TE11 mode by inserting fins into the overmode bend circular waveguide along the plane of bend. After transmission by the bend, the half-circular waveguide TE11 mode is re-converted to the circular waveguide TM01 mode. An overmode bend circular waveguide of bend 45° for 2.856 GHz based on this principle is designed and optimized, as well as studied. The experiment results show that：at the center frequency of 2.856 GHz, the loss is about 0.247 dB and VSWR is 1.217. In the range of 2.75 GHz to 2.95 GHz, the loss and VSWR are below 0.53 dB and 1.34 respectively. Curvature radius of the overmode bend circular waveguide i
One novel overmode bend circular waveguide is designed and studied. The novel approach is as follows: the circular waveguide TM01 mode is converted to half-circular waveguide TE11 mode by inserting fins into the overmode bend circular waveguide along the plane of bend. After transmission by the bend, the half-circular waveguide TE11 mode is re-converted to the circular waveguide TM01 mode. An overmode bend circular waveguide of bend 45° for 2.856 GHz based on this principle is designed and optimized, as well as studied. The experiment results show that：at the center frequency of 2.856 GHz, the loss is about 0.247 dB and VSWR is 1.217. In the range of 2.75 GHz to 2.95 GHz, the loss and VSWR are below 0.53 dB and 1.34 respectively. Curvature radius of the overmode bend circular waveguide i
2011,
23.
Abstract:
The special structure and working principle of all-solid-state fast ionization device(FID) are studied. The compression characteristics in pulse voltage amplitude and pulse width of FID are given through experiment study at different exterior bias voltages. The experimental result of transforming the input pulse of voltage 1.7 kV, width 4 μs, repetition frequency 2 kHz into the output pulse of voltage 1 985 V, width 90 ns, repetition frequency 2 kHz is obtained from FID compression under 50 Ω load.
The special structure and working principle of all-solid-state fast ionization device(FID) are studied. The compression characteristics in pulse voltage amplitude and pulse width of FID are given through experiment study at different exterior bias voltages. The experimental result of transforming the input pulse of voltage 1.7 kV, width 4 μs, repetition frequency 2 kHz into the output pulse of voltage 1 985 V, width 90 ns, repetition frequency 2 kHz is obtained from FID compression under 50 Ω load.
2011,
23.
Abstract:
An X-band high power microwave(HPM) antenna based on leaky waveguide was designed and investigated. Its radiation characteristics were determined by transverse resonance approach and numerical full wave simulation optimization. The simulation results indicate that, the antenna gain is 26.2 dBi, the aperture efficiency is above 70%, the power handling capacity is above 200 MW at 9.6 GHz, the reflection coefficient is less than -20 dB, and in far-field waveform deformation would not occur at the angle of maximum radiation in response to short pulses of tens of nanoseconds, which validate the feasibility of the antenna in HPM application.
An X-band high power microwave(HPM) antenna based on leaky waveguide was designed and investigated. Its radiation characteristics were determined by transverse resonance approach and numerical full wave simulation optimization. The simulation results indicate that, the antenna gain is 26.2 dBi, the aperture efficiency is above 70%, the power handling capacity is above 200 MW at 9.6 GHz, the reflection coefficient is less than -20 dB, and in far-field waveform deformation would not occur at the angle of maximum radiation in response to short pulses of tens of nanoseconds, which validate the feasibility of the antenna in HPM application.
2011,
23.
Abstract:
In order to improve the field uniformity in the work space of a reverberation chamber， the mechanism of the position of emission antenna affecting the field uniformity was analyzed, and the simulation model was constructed and analyzed with FEKO software based on the method of moments combining genetic algorithm(GA) with MOM was put forward to analyze and optimize the reverberation chamber, and the effect of the position of emission antenna on the field uniformity in the work space was investigated. The optimal results show that the field uniformity of working volume is improved by optimization. The experiments verify that the method could be used to optimize the design of a reverberation chamber．
In order to improve the field uniformity in the work space of a reverberation chamber， the mechanism of the position of emission antenna affecting the field uniformity was analyzed, and the simulation model was constructed and analyzed with FEKO software based on the method of moments combining genetic algorithm(GA) with MOM was put forward to analyze and optimize the reverberation chamber, and the effect of the position of emission antenna on the field uniformity in the work space was investigated. The optimal results show that the field uniformity of working volume is improved by optimization. The experiments verify that the method could be used to optimize the design of a reverberation chamber．
