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RSS2001 Vol. 13, No. 04
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2001,
13.
Abstract:
High-resolution X-ray photographing needs to focus intense relativistic electronic beams of several thousand amperes on the bremsstrahlung converter target, thereon forming small and stable spots. In the ideal focusing case, electron beams can be focused to a point. However, due to the influence of such factors as the space charge effect, the beam emittance, the spherical aberration of a lens, and the chromatic aberration, the minimal spot size of electronic beams will be limited. Furthermore, the corkscrew oscillation of the beam centroid will not only increase the spot size but also lead to the distortion of the spot shape.This paper analyzes the precondition transporting stably intense beams in an alternating solenoid field and presents the method confining corkscrew oscillations by usi
High-resolution X-ray photographing needs to focus intense relativistic electronic beams of several thousand amperes on the bremsstrahlung converter target, thereon forming small and stable spots. In the ideal focusing case, electron beams can be focused to a point. However, due to the influence of such factors as the space charge effect, the beam emittance, the spherical aberration of a lens, and the chromatic aberration, the minimal spot size of electronic beams will be limited. Furthermore, the corkscrew oscillation of the beam centroid will not only increase the spot size but also lead to the distortion of the spot shape.This paper analyzes the precondition transporting stably intense beams in an alternating solenoid field and presents the method confining corkscrew oscillations by usi
2001,
13.
Abstract:
The simulation and experimental results of electron gun with a ferroelectric material cathode by author in Cornell university are presented in this paper. The results show that the current densities is of order 110A/cm2, experimental. The current generated with the ferroelectric material cathode exceeds space charge limited current, It is considered this is caused by the electric field enhancement near the cathode surface, due to the introduction of trigger pulse, FE effect, and grid structure etc. Enhanced electric field will accelerate electrons to some energy in the district near cathode surface. According to this, The electron gun with ferroelectric material cathode can be simulated and designed by injecting electrons from cathode with an effective initial energy.
The simulation and experimental results of electron gun with a ferroelectric material cathode by author in Cornell university are presented in this paper. The results show that the current densities is of order 110A/cm2, experimental. The current generated with the ferroelectric material cathode exceeds space charge limited current, It is considered this is caused by the electric field enhancement near the cathode surface, due to the introduction of trigger pulse, FE effect, and grid structure etc. Enhanced electric field will accelerate electrons to some energy in the district near cathode surface. According to this, The electron gun with ferroelectric material cathode can be simulated and designed by injecting electrons from cathode with an effective initial energy.
2001,
13.
Abstract:
ELV-8 accelerator use flat lanthanum hexaboride as the cathode .The acceleration tube consists of alternating gradient section and equi-gradient section. Focusing of electron is completed by electrical fields of alternating gradient, which makes electron beam a laminar beam. The flat electrode of the electron gun makes the electrical fields before the gun uniform, so the electron optical characteristic of the accelerating tube is not sensitive to the initial condition and the replacement of electron gun is convenient.
ELV-8 accelerator use flat lanthanum hexaboride as the cathode .The acceleration tube consists of alternating gradient section and equi-gradient section. Focusing of electron is completed by electrical fields of alternating gradient, which makes electron beam a laminar beam. The flat electrode of the electron gun makes the electrical fields before the gun uniform, so the electron optical characteristic of the accelerating tube is not sensitive to the initial condition and the replacement of electron gun is convenient.
2001,
13.
Abstract:
A superconducting cavity coupler with coaxial symmetric structure is introduced. The coupling parameter of the coupler is analyzed by the SUPERFISH program. The curve of the coupler inner conductor position versus coupling parameter is obtained. The analyze result of coupling parameter is according with the experiment of a model cavity. As a result, the coupling parameter of CAEP superconducting photocathode injector experiment is given: coupling parameter is 1637, the position of coupler inner conductor is 15.45cm and the average accelerating field is 20MV/m.
A superconducting cavity coupler with coaxial symmetric structure is introduced. The coupling parameter of the coupler is analyzed by the SUPERFISH program. The curve of the coupler inner conductor position versus coupling parameter is obtained. The analyze result of coupling parameter is according with the experiment of a model cavity. As a result, the coupling parameter of CAEP superconducting photocathode injector experiment is given: coupling parameter is 1637, the position of coupler inner conductor is 15.45cm and the average accelerating field is 20MV/m.
2001,
13.
Abstract:
A rf-driven ion source has been developed for the ion beam bioengineering. As used in an electrostatic accelerator, the ion source was specially designed considering with the structure, weight and the power supplies. The size of the extracting electrode was calculated in detail. The extracting beam characteristics of the ion source depending on extracting voltage, focusing voltage and gas pressure were obtained by experiments. The variation of the beam radius along the axis was measured. Factors producing the beam instability were generally discussed, and effective techniques were used to reduce the beam instability. Experimental results showed that the extracting characteristics matched the theoretical expectation well. the maximum beam current was obtained when the extracting voltage was
A rf-driven ion source has been developed for the ion beam bioengineering. As used in an electrostatic accelerator, the ion source was specially designed considering with the structure, weight and the power supplies. The size of the extracting electrode was calculated in detail. The extracting beam characteristics of the ion source depending on extracting voltage, focusing voltage and gas pressure were obtained by experiments. The variation of the beam radius along the axis was measured. Factors producing the beam instability were generally discussed, and effective techniques were used to reduce the beam instability. Experimental results showed that the extracting characteristics matched the theoretical expectation well. the maximum beam current was obtained when the extracting voltage was
2001,
13.
Abstract:
Based on the light absorption mechanism, the characters of the pulsed laser in the pulsed laser simulation of single event upset are analyzed. The Monte Carlo calculation of the used pulsed laser simulation of single event upset is put forward. In the simplified case of only considering the photon electrical effect, the relationship between the energy threshold of the incident pulsed laser and the critical charge of a silicon chip (or the linear energy transfer) is obtained, a function for calculating the upset cross-section of the silicon chip is also obtained. The calculated results show that the energy threshold is several picojoules corresponding to the linear energy transfer 0.05pC/m m. For the critical charge 0.05 0.20pC, the calculated energy threshold is several 10-11J, the upset c
Based on the light absorption mechanism, the characters of the pulsed laser in the pulsed laser simulation of single event upset are analyzed. The Monte Carlo calculation of the used pulsed laser simulation of single event upset is put forward. In the simplified case of only considering the photon electrical effect, the relationship between the energy threshold of the incident pulsed laser and the critical charge of a silicon chip (or the linear energy transfer) is obtained, a function for calculating the upset cross-section of the silicon chip is also obtained. The calculated results show that the energy threshold is several picojoules corresponding to the linear energy transfer 0.05pC/m m. For the critical charge 0.05 0.20pC, the calculated energy threshold is several 10-11J, the upset c
2001,
13.
Abstract:
This paper describes the observed results of short-time pellet ablation based on CCD application during the multi-pellet fuelling experiment in the HL-1M tokamak, introduces a characteristic trigger mode, that is, Ha radiation signal emitting from pellet itself to trigger CCD camera. The experiment proves that a lot of photos can be taken through this arrangement and CCD camera is successfully applied to pellet ablation process investigation. Through photos processing and analysis, the structure on different plasma positions, dimension and space Ha emission profile of ablation cloud are obtained, therefore the CCD diagnosis means not only makes pellet fuelling understand deeply，but also may promote the transient &high-speed process research in the field of military and engineering.
This paper describes the observed results of short-time pellet ablation based on CCD application during the multi-pellet fuelling experiment in the HL-1M tokamak, introduces a characteristic trigger mode, that is, Ha radiation signal emitting from pellet itself to trigger CCD camera. The experiment proves that a lot of photos can be taken through this arrangement and CCD camera is successfully applied to pellet ablation process investigation. Through photos processing and analysis, the structure on different plasma positions, dimension and space Ha emission profile of ablation cloud are obtained, therefore the CCD diagnosis means not only makes pellet fuelling understand deeply，but also may promote the transient &high-speed process research in the field of military and engineering.
2001,
13.
Abstract:
The Shack-Hartmann wavefront sensor is the most popular type in adaptive optics system operated with faint objects, because of its outstanding advantages in high light efficiency, simple structure. In this paper, the signal statistics of image-intensified CCD(ICCD) wavefront sensor is analysized, and a mathematical model of its measurement error is given. One kind of ICCD(C2166 type image intensifier from Hamamatsu Photonics) wavefront sensor is tested. The results show that the different pixel sampling values of ICCD are not independent statistically and the measurement signals don’t obey the characteristics of Poisson distribution. No only the photon noises and readout noises, but also the gain fluctuation noises exist in the ICCD wavefront sensor. The measurement error is dependent on
The Shack-Hartmann wavefront sensor is the most popular type in adaptive optics system operated with faint objects, because of its outstanding advantages in high light efficiency, simple structure. In this paper, the signal statistics of image-intensified CCD(ICCD) wavefront sensor is analysized, and a mathematical model of its measurement error is given. One kind of ICCD(C2166 type image intensifier from Hamamatsu Photonics) wavefront sensor is tested. The results show that the different pixel sampling values of ICCD are not independent statistically and the measurement signals don’t obey the characteristics of Poisson distribution. No only the photon noises and readout noises, but also the gain fluctuation noises exist in the ICCD wavefront sensor. The measurement error is dependent on
2001,
13.
Abstract:
An optical klystron is built in the 800 MeV electron storage ring at University of Science and Technology of China for harmonic super-radiation generation. In single bunch operation mode the repetition rate of the spontaneous radiation pulses is about 4.533MHz, and the repetition rate of the seed laser pulses is about 3Hz, while the radiation pulse width is 300ps. For measuring harmonic radiation a high on/off ratio ICCD is used as an optical switch to reject spontaneous radiation pulses of high repetition rate.
An optical klystron is built in the 800 MeV electron storage ring at University of Science and Technology of China for harmonic super-radiation generation. In single bunch operation mode the repetition rate of the spontaneous radiation pulses is about 4.533MHz, and the repetition rate of the seed laser pulses is about 3Hz, while the radiation pulse width is 300ps. For measuring harmonic radiation a high on/off ratio ICCD is used as an optical switch to reject spontaneous radiation pulses of high repetition rate.
2001,
13.
Abstract:
The dependence of ZnO/K2SiO3 thermal control coating optical characteristics upon electron exposure was studied. The test specimens were exposed to 10, 30, 50 and 70keV electrons. The spectral reflectance of each test specimen was measured in situ before and after exposures. The solar absorptance was calculated by assuming a Johnson solar spectral irradiance distribution. The effects of electron energy on spectral reflectance and solar absorptance have been analyzed. The results are discussed relative to the change in spectral reflectance in the near infrared wavelength region. It is found that under the effect of electron exposure, the ZnO/K2SiO3 suffers a big amount of degradation. The magnitude of degradation is electron energy dependent, it goes up as the electron energy increases.
The dependence of ZnO/K2SiO3 thermal control coating optical characteristics upon electron exposure was studied. The test specimens were exposed to 10, 30, 50 and 70keV electrons. The spectral reflectance of each test specimen was measured in situ before and after exposures. The solar absorptance was calculated by assuming a Johnson solar spectral irradiance distribution. The effects of electron energy on spectral reflectance and solar absorptance have been analyzed. The results are discussed relative to the change in spectral reflectance in the near infrared wavelength region. It is found that under the effect of electron exposure, the ZnO/K2SiO3 suffers a big amount of degradation. The magnitude of degradation is electron energy dependent, it goes up as the electron energy increases.
2001,
13.
Abstract:
The electron residual energy in different plasma of low Z gas target driven by ultra-short linear polarized laser with different parameters, is analytically calculated and simulated by cloud-in-cell (CIC) method. Considering that plasma produced by linear polarized light in strong field has low temperature and high ionization degree, instead of normal equation of calculating inverse bremsstrahlung rate, zero-temperature approximation is adopted. In CIC simulation, longitudinal electric field effect in interaction of strong field with gas target is also included. The results of theoretical calculation of the interaction between linear polarized laser and gas targets of He, Ne as well as the corresponding conclusions are presented.
The electron residual energy in different plasma of low Z gas target driven by ultra-short linear polarized laser with different parameters, is analytically calculated and simulated by cloud-in-cell (CIC) method. Considering that plasma produced by linear polarized light in strong field has low temperature and high ionization degree, instead of normal equation of calculating inverse bremsstrahlung rate, zero-temperature approximation is adopted. In CIC simulation, longitudinal electric field effect in interaction of strong field with gas target is also included. The results of theoretical calculation of the interaction between linear polarized laser and gas targets of He, Ne as well as the corresponding conclusions are presented.
2001,
13.
Abstract:
Based on the theory of probability and statistics, the energy instability which caused by the random error from optical parameters of multi-beam high power solid laser was calculated in this paper. The simulation prototype has been founded on the dozens of four-pass amplifiers. The energy spread was evaluated for the amplifiers which output 1ns and 13ns flat-in-time laser pulses. As a result, the energy spread of outputing pulses for 1ns pulses was bigger than that for 13ns pulses at the same conditions. Because for 13ns pulses, the amplifiers have been forced to work at deep gain saturation state; but for 1ns pulses, the amplifiers have been worked at linear amplification state. Using this characteristic of amplifiers, the energy spread of multi-beam lasers could be reduced by increasing
Based on the theory of probability and statistics, the energy instability which caused by the random error from optical parameters of multi-beam high power solid laser was calculated in this paper. The simulation prototype has been founded on the dozens of four-pass amplifiers. The energy spread was evaluated for the amplifiers which output 1ns and 13ns flat-in-time laser pulses. As a result, the energy spread of outputing pulses for 1ns pulses was bigger than that for 13ns pulses at the same conditions. Because for 13ns pulses, the amplifiers have been forced to work at deep gain saturation state; but for 1ns pulses, the amplifiers have been worked at linear amplification state. Using this characteristic of amplifiers, the energy spread of multi-beam lasers could be reduced by increasing
2001,
13.
Abstract:
Based on the theory of chirped-pulse parametric amplification, the application of optical parametric amplification in chirped-pulse amplification is simulated. Gain and temporal characteristic of optical parametric chirped-pulse amplification is studied, especially in the small signal-condition and the large signal-condition. The infection of the group-velocity mismatch and the phase-velocity mismatch in the process of the amplification are discussed respectively. The request of synchronization between pump-pulse and signal-pulse is taked into account. The stability of the system is evaluated.
Based on the theory of chirped-pulse parametric amplification, the application of optical parametric amplification in chirped-pulse amplification is simulated. Gain and temporal characteristic of optical parametric chirped-pulse amplification is studied, especially in the small signal-condition and the large signal-condition. The infection of the group-velocity mismatch and the phase-velocity mismatch in the process of the amplification are discussed respectively. The request of synchronization between pump-pulse and signal-pulse is taked into account. The stability of the system is evaluated.
2001,
13.
Abstract:
The power deposition in nuclear Reactor Pumped Laser (RPL) cavity is studied in the present work. Basing on the calculated results with TRIM-code, EDL (Energy Deposition and Loss) code is used to calculate the energy deposition and energy loss in the 3He-Ar-Xe gas laser cavity. EDL is developed with Monte Carlo method. The relationship between power deposition density and the laser cavity parameters was studied, and the power deposition density function was derived in the paper. The results agree well with the results of reference.
The power deposition in nuclear Reactor Pumped Laser (RPL) cavity is studied in the present work. Basing on the calculated results with TRIM-code, EDL (Energy Deposition and Loss) code is used to calculate the energy deposition and energy loss in the 3He-Ar-Xe gas laser cavity. EDL is developed with Monte Carlo method. The relationship between power deposition density and the laser cavity parameters was studied, and the power deposition density function was derived in the paper. The results agree well with the results of reference.
2001,
13.
Abstract:
The propagation of Gaussian beams through a paraxial ABCD optical system with hard-edge aperture is studied. In the treatment the rectangular function is expanded into a sum of complex Gaussian functions, thus the approximate analytical propagation expression can be derived. As an application example, numerical calculations are performed for Gaussian beams propagating in free space with hard-edge aperture. The advantage of greatly reducing the computing time and computation errors are discussed. Further extension to plan waves and flattened Gaussian beams is made to confirm the wide applicability of this method.
The propagation of Gaussian beams through a paraxial ABCD optical system with hard-edge aperture is studied. In the treatment the rectangular function is expanded into a sum of complex Gaussian functions, thus the approximate analytical propagation expression can be derived. As an application example, numerical calculations are performed for Gaussian beams propagating in free space with hard-edge aperture. The advantage of greatly reducing the computing time and computation errors are discussed. Further extension to plan waves and flattened Gaussian beams is made to confirm the wide applicability of this method.
2001,
13.
Abstract:
The high-bright X-ray can be generated by the back-Compton scattering through the laser with electron beam, and the wavelength is tunable by changing the electron energy. Because of the low scattering chance of the scattering photon with the electron, it is difficult to acquire the high-bright radiation. The high power density laser and the high-bright electron beam is required to obtain the high-bright radiation. In the experiment, the electron beam of CAEP RF photoinjector together with 30MeV linac and the high power density laser in Nd:YAG laser cavity will be used, the radiation wavelength is 0.07 0.14nm, the radiation ability expected to be about 2.5 1011 photons per second, and the radiation wavelength can be tuned by changing the electron energy.
The high-bright X-ray can be generated by the back-Compton scattering through the laser with electron beam, and the wavelength is tunable by changing the electron energy. Because of the low scattering chance of the scattering photon with the electron, it is difficult to acquire the high-bright radiation. The high power density laser and the high-bright electron beam is required to obtain the high-bright radiation. In the experiment, the electron beam of CAEP RF photoinjector together with 30MeV linac and the high power density laser in Nd:YAG laser cavity will be used, the radiation wavelength is 0.07 0.14nm, the radiation ability expected to be about 2.5 1011 photons per second, and the radiation wavelength can be tuned by changing the electron energy.
2001,
13.
Abstract:
With the analysis of impurities at different locations and spectral transmittance of conventionally and rapid grown KDP crystals, several factors which influence the transmittance of crystals at ultraviolet band are discussed. Also multi-short damage thresholds of crystals induced by pico-second laser pulses at wavelength 1 064nm and 532nm are reported. Crystal adsorption and the damage threshold correspondent suggest that impurities as well as the lattice defect convert irradiance to heat distinctly and thus reduce the damage threshold of crystals.
With the analysis of impurities at different locations and spectral transmittance of conventionally and rapid grown KDP crystals, several factors which influence the transmittance of crystals at ultraviolet band are discussed. Also multi-short damage thresholds of crystals induced by pico-second laser pulses at wavelength 1 064nm and 532nm are reported. Crystal adsorption and the damage threshold correspondent suggest that impurities as well as the lattice defect convert irradiance to heat distinctly and thus reduce the damage threshold of crystals.
2001,
13.
Abstract:
The threshold of laser induced breakdown in high temperature atomic oxygen gas is obtained by solving quantum Boltzmann equation for electrons numerically. This threshold is much more smaller than that in low temperature molecular gas. The reason is that in the high temperature gas, the distribution of energy level and the degree of freedom is much more different from that in molecular gas. The vibrational excitation of molecule in molecular gas dose not exist in atomic gas, which reduces the energy loss of electrons and increases ionization rate.
The threshold of laser induced breakdown in high temperature atomic oxygen gas is obtained by solving quantum Boltzmann equation for electrons numerically. This threshold is much more smaller than that in low temperature molecular gas. The reason is that in the high temperature gas, the distribution of energy level and the degree of freedom is much more different from that in molecular gas. The vibrational excitation of molecule in molecular gas dose not exist in atomic gas, which reduces the energy loss of electrons and increases ionization rate.
2001,
13.
Abstract:
A Giga-Hertz Transverse Electromagnetic Cell (GTEM Cell) was used to study the interference of continuous electromagnetic waves on a chaotic synchronous secure communication system, which was based on the typical Chua's chaotic circuits. During the experiments, it was found that within the frequency range from 100MHz-150MHz there were some thresholds of the electromagnetic radiant (EMR) power density to a certain chaotic secure communication system. If the EMR power density is great than the threshold in this frequency range, the chaotic encrypt function of the secure communication system will be ineffective. Moreover, the chaotic synchronous secure communication system cannot recover from the ineffective state to chaotic synchronous state by itself even after the EMR is removed. This is a
A Giga-Hertz Transverse Electromagnetic Cell (GTEM Cell) was used to study the interference of continuous electromagnetic waves on a chaotic synchronous secure communication system, which was based on the typical Chua's chaotic circuits. During the experiments, it was found that within the frequency range from 100MHz-150MHz there were some thresholds of the electromagnetic radiant (EMR) power density to a certain chaotic secure communication system. If the EMR power density is great than the threshold in this frequency range, the chaotic encrypt function of the secure communication system will be ineffective. Moreover, the chaotic synchronous secure communication system cannot recover from the ineffective state to chaotic synchronous state by itself even after the EMR is removed. This is a
2001,
13.
Abstract:
Designing an octave bandwidth helical traveling wave tube for phase and gain matched operation in the EHF region presents many obstacles, the dimensional controls which must be imposed in the design and fabrication of parallel-operating are difficult. Recent advance in the state of computer modeling offer the possibility to evaluate the effect that slow-wave structure parameter and operating parameter variations, such as manufacturing tolerances, this will enable manufacturers to determine the cost effectiveness of controlling the dimensions of the component parts of the TWT. The computer code MAFIA is used to determine the effect on dispersion and on-axis interaction impedance of several helical slow-wave circuit parameter variations. In this paper, computer code Phase-Coincidence TWT CAD
Designing an octave bandwidth helical traveling wave tube for phase and gain matched operation in the EHF region presents many obstacles, the dimensional controls which must be imposed in the design and fabrication of parallel-operating are difficult. Recent advance in the state of computer modeling offer the possibility to evaluate the effect that slow-wave structure parameter and operating parameter variations, such as manufacturing tolerances, this will enable manufacturers to determine the cost effectiveness of controlling the dimensions of the component parts of the TWT. The computer code MAFIA is used to determine the effect on dispersion and on-axis interaction impedance of several helical slow-wave circuit parameter variations. In this paper, computer code Phase-Coincidence TWT CAD
2001,
13.
Abstract:
Some structural and electric parameter characteristics of the MBK were explained in the article. Approximate formula on the output cavity coupling coefficient of the MBK was driven, using method of the normal mode analysis for a pillbox output cavity. Bandwidth characteristics of the MBK were analyzed preliminary in this paper. It concluded that the increase of product of MBK’s output efficiency and its bandwidth completely depends on the increase of beam’s perveances. It also concluded that the output cavity coupling coefficient and the characteristic impedance of the cavity decrease as the beam number grows, but they decrease more slowly than the increase of perveances as the beam number grows.
Some structural and electric parameter characteristics of the MBK were explained in the article. Approximate formula on the output cavity coupling coefficient of the MBK was driven, using method of the normal mode analysis for a pillbox output cavity. Bandwidth characteristics of the MBK were analyzed preliminary in this paper. It concluded that the increase of product of MBK’s output efficiency and its bandwidth completely depends on the increase of beam’s perveances. It also concluded that the output cavity coupling coefficient and the characteristic impedance of the cavity decrease as the beam number grows, but they decrease more slowly than the increase of perveances as the beam number grows.
2001,
13.
Abstract:
To realize the saturation output of Beijing Free Electron Laser, the phase stability of RF power in accelerator is required to be less than ± 1° . In this paper, the relations between RF phase variation and the Pulse Form Net (PFN) in modulator of klystron are carefully studied through experiments. In order to meet the requirement of RF phase stability, all 48 sets of the PFN in HV modulator are repeatedly adjusted to obtain optimum result. The results show that the distributed parameters of the PFN take an important part in the stability of RF phase. In the pulse width of 6 s, RF phase ripple from the output of klystron is reduced to ± 1.5° from ± 2.6° before the adjustment; In the pulse width of 4 s, practically used in BFEL, RF phase ripple is only± 1° .
To realize the saturation output of Beijing Free Electron Laser, the phase stability of RF power in accelerator is required to be less than ± 1° . In this paper, the relations between RF phase variation and the Pulse Form Net (PFN) in modulator of klystron are carefully studied through experiments. In order to meet the requirement of RF phase stability, all 48 sets of the PFN in HV modulator are repeatedly adjusted to obtain optimum result. The results show that the distributed parameters of the PFN take an important part in the stability of RF phase. In the pulse width of 6 s, RF phase ripple from the output of klystron is reduced to ± 1.5° from ± 2.6° before the adjustment; In the pulse width of 4 s, practically used in BFEL, RF phase ripple is only± 1° .
2001,
13.
Abstract:
This paper numerically studies the radiation processes of the ultrawide band electromagnetic pulse emitted from the TEM antenna fed through the coaxial transmission line. The front end of the TEM horn antenna is a parallel-plate transmission line. The finite-difference time-domain method is adopted to simulate the processes of transmission in the parallel-plate transmission line and TEM horn. For the TEM horn, this paper presents the input impedance and voltage standing wave ratio as a function of frequencies. The radiated field distribution and energy pattern are also provided.
This paper numerically studies the radiation processes of the ultrawide band electromagnetic pulse emitted from the TEM antenna fed through the coaxial transmission line. The front end of the TEM horn antenna is a parallel-plate transmission line. The finite-difference time-domain method is adopted to simulate the processes of transmission in the parallel-plate transmission line and TEM horn. For the TEM horn, this paper presents the input impedance and voltage standing wave ratio as a function of frequencies. The radiated field distribution and energy pattern are also provided.
2001,
13.
Abstract:
This paper brings forth a new relativistic backward-wave oscillator with axial extracting. Numerical simulation is conducted using KARAT code. This simulation produces a microwave pulse power of 2.0GW at 9.28GHz for 730 kV, 6kA injecting beam. Power transform efficiency of 45% is obtained. The interaction between beam and slow wave structure is tracked and analyzed. SUPERFISH code is used to calculate axial electric field distribution, and the results shows that the relativistic backward-wave oscillator with axial extracting has the advantage of increasing efficiency.
This paper brings forth a new relativistic backward-wave oscillator with axial extracting. Numerical simulation is conducted using KARAT code. This simulation produces a microwave pulse power of 2.0GW at 9.28GHz for 730 kV, 6kA injecting beam. Power transform efficiency of 45% is obtained. The interaction between beam and slow wave structure is tracked and analyzed. SUPERFISH code is used to calculate axial electric field distribution, and the results shows that the relativistic backward-wave oscillator with axial extracting has the advantage of increasing efficiency.
2001,
13.
Abstract:
The paper presents the results of the experiment research on HPM pulse compression at S band by the method of switched energy storage. The input pulse is of the power ranged from 1.0 2.7MW and 1.4m s width. The width of output pulse is about 13 14ns, the power gain is about 40 and the output power is 106MW. A spontaneous gas breakdown switch is used. It is shown that the rise time of output pulse is depended on the gas pressure and gas ingredient and the power gain is of no relation with the rise time of output pulse.
The paper presents the results of the experiment research on HPM pulse compression at S band by the method of switched energy storage. The input pulse is of the power ranged from 1.0 2.7MW and 1.4m s width. The width of output pulse is about 13 14ns, the power gain is about 40 and the output power is 106MW. A spontaneous gas breakdown switch is used. It is shown that the rise time of output pulse is depended on the gas pressure and gas ingredient and the power gain is of no relation with the rise time of output pulse.
2001,
13.
Abstract:
A 2-1/2D cylindrical full electromagnetic particle-in-cell code ABLE2D is used to simulate conducting and opening procession of a low-density plasma erosion opening switch. The building of computing model and complex boundaries has been introduced in detail. In simulation results, current channel forms at the generator side of the plasma at first and migrates to the load side of the plasma with current increase. The electrons in the current channel move across plasma from cathode to anode by E xB drift, the magnetic field is advected with the electron flow as a frozen in field tied to the electrons. The ion density is almost unchanged in the conduction procession of PEOS, but become lower quickly in the opening procession. When PEOS is entirely opening, ion density near cathode is close to
A 2-1/2D cylindrical full electromagnetic particle-in-cell code ABLE2D is used to simulate conducting and opening procession of a low-density plasma erosion opening switch. The building of computing model and complex boundaries has been introduced in detail. In simulation results, current channel forms at the generator side of the plasma at first and migrates to the load side of the plasma with current increase. The electrons in the current channel move across plasma from cathode to anode by E xB drift, the magnetic field is advected with the electron flow as a frozen in field tied to the electrons. The ion density is almost unchanged in the conduction procession of PEOS, but become lower quickly in the opening procession. When PEOS is entirely opening, ion density near cathode is close to
2001,
13.
Abstract:
In this paper, the hybrid optimization algorithm, combing Hill-climbing and Simulated Annealing, is adopted to design the diffractive optical element (DOE) to realize beam smoothing. The performance of the DOE is improved by choosing suitable weight factor in the optimization, the non-uniformity is optimized to be less than 1% and the light efficiency greater than 95%. A large aperture DOE with diameter 180mm is fabricated by ion-etching with a hollowed-out mask. The intensity distribution of the focused spot is measured and a rather good intensity envelope has been obtained, without the center zeroth-order pulse but with a rather large high-frequency top modulation. Furthermore, to realize a true beam smoothing, improve the top uniformity and increase the tolerance of phase distortion, th
In this paper, the hybrid optimization algorithm, combing Hill-climbing and Simulated Annealing, is adopted to design the diffractive optical element (DOE) to realize beam smoothing. The performance of the DOE is improved by choosing suitable weight factor in the optimization, the non-uniformity is optimized to be less than 1% and the light efficiency greater than 95%. A large aperture DOE with diameter 180mm is fabricated by ion-etching with a hollowed-out mask. The intensity distribution of the focused spot is measured and a rather good intensity envelope has been obtained, without the center zeroth-order pulse but with a rather large high-frequency top modulation. Furthermore, to realize a true beam smoothing, improve the top uniformity and increase the tolerance of phase distortion, th
2001,
13.
Abstract:
In this paper, a model for the interaction of intense pulsed ion beams (IPIB) with metallic targets is briefly described. Then the thermal-mechanical effects on the aluminum target irradiated by the IPIBs with ion energy of 300 keV and 1.0 MeV, current density of 10, 50, 100 A/cm2 are simulated numerically. The calculation results, i.e., the stress, temperature, temperature gradient distributions, heating and cooling rates and elastic waves and shocks are presented and discussed.
In this paper, a model for the interaction of intense pulsed ion beams (IPIB) with metallic targets is briefly described. Then the thermal-mechanical effects on the aluminum target irradiated by the IPIBs with ion energy of 300 keV and 1.0 MeV, current density of 10, 50, 100 A/cm2 are simulated numerically. The calculation results, i.e., the stress, temperature, temperature gradient distributions, heating and cooling rates and elastic waves and shocks are presented and discussed.
2001,
13.
Abstract:
The technique of sampling-image streaking frame for plasma diagnostics in ICF is presented. Theoretical analysis of this technique, including its exposures time, framing rate and spatial resolution is given. A specially designed streak image tube, together with an active-passive mode-locked YAG laser is used to make a preliminary proof-of-principle experiment. And by means of digital image processing the experiment result gives 16 frames with an exposure time of better than 6.3ps and spatial resolution of 3.5 lp/mm in the photocathode.
The technique of sampling-image streaking frame for plasma diagnostics in ICF is presented. Theoretical analysis of this technique, including its exposures time, framing rate and spatial resolution is given. A specially designed streak image tube, together with an active-passive mode-locked YAG laser is used to make a preliminary proof-of-principle experiment. And by means of digital image processing the experiment result gives 16 frames with an exposure time of better than 6.3ps and spatial resolution of 3.5 lp/mm in the photocathode.
