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RSS2001 Vol. 13, No. 03
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2001,
13.
Abstract:
A series of optimization designs of electron diode in 12MeV linear induction accelerator are studied by using numerical simulation code MAGIC and experiment method in order to improve the electron beam quality.MAGIC code solves the Maxwell equations in the presence of charged particle,Electron field distribution on cathode surface which influences electron emission can be given,the optimum diode is obtained by comparing to the results of experiment in 12MeV, then the paper gives SEM analysis and experiment comparison of velvet emission. Finally, emitted current Ie= 8.52kA ,beam current I8= 3.0kA, targeted current I0= 2.30kA with optimum diode are obtained.
A series of optimization designs of electron diode in 12MeV linear induction accelerator are studied by using numerical simulation code MAGIC and experiment method in order to improve the electron beam quality.MAGIC code solves the Maxwell equations in the presence of charged particle,Electron field distribution on cathode surface which influences electron emission can be given,the optimum diode is obtained by comparing to the results of experiment in 12MeV, then the paper gives SEM analysis and experiment comparison of velvet emission. Finally, emitted current Ie= 8.52kA ,beam current I8= 3.0kA, targeted current I0= 2.30kA with optimum diode are obtained.
2001,
13.
Abstract:
The beam current characteristics of a two-component space-charge diode under the effect of electron injection with initial energy are studied. The diode is divided into two regions, by solving Poisson equations in the two regions, to yield analytical expressions for space-charge-limited electron/ion beam current densities of non-relativistic one-dimensional slab two-component fluxe diode as a function of the initial energy of electrons emitted from the cathode, and compared with these results of zero initial energy of electrons, the results show that the two-component space-charge-limited current densities decrease as the initial energy of electrons increase.
The beam current characteristics of a two-component space-charge diode under the effect of electron injection with initial energy are studied. The diode is divided into two regions, by solving Poisson equations in the two regions, to yield analytical expressions for space-charge-limited electron/ion beam current densities of non-relativistic one-dimensional slab two-component fluxe diode as a function of the initial energy of electrons emitted from the cathode, and compared with these results of zero initial energy of electrons, the results show that the two-component space-charge-limited current densities decrease as the initial energy of electrons increase.
2001,
13.
Abstract:
The paper introduced a type of small explosive magnetic flux compression generator(MFCG), which can provide pulse current up to 50-75kA,voltage 40-60kV at high inductance load(5-6μH). With the combined use of transformer and electric exploding opening switch (EEOS),it can drive high impedance (100W ) to generate more than 800 kV pulse voltage.
The paper introduced a type of small explosive magnetic flux compression generator(MFCG), which can provide pulse current up to 50-75kA,voltage 40-60kV at high inductance load(5-6μH). With the combined use of transformer and electric exploding opening switch (EEOS),it can drive high impedance (100W ) to generate more than 800 kV pulse voltage.
2001,
13.
Abstract:
The structure of the diode with velvet cathode and the design of the velvet cathode are described; the methods of diode parameter measurement and the results of diode experiment are presented. In the experiment, large area uniform electron beam is generated by three types of velvet cathode, and the uniformity of e-beam is diagnosed. The results of diode experiment show that with the similar diode parameter, the uniformity of e-beam generated by three types of velvet cathode is similar. In the last, the results of experiment are discussed.
The structure of the diode with velvet cathode and the design of the velvet cathode are described; the methods of diode parameter measurement and the results of diode experiment are presented. In the experiment, large area uniform electron beam is generated by three types of velvet cathode, and the uniformity of e-beam is diagnosed. The results of diode experiment show that with the similar diode parameter, the uniformity of e-beam generated by three types of velvet cathode is similar. In the last, the results of experiment are discussed.
2001,
13.
Abstract:
In order to improve RF cavity amplitude stability of Separated Sector Cyclotron (SSC) of Heavy Ion Research Facility in Lanzhou (HIRFL) for increasing accelerator beam current intensity, a set of new RF amplitude stabilization device is developed. Compared with the former RF amplitude stabilization device, the new one is featured by its double stabilizing control loops and single chip micro-computer control mode. The stability of SSC RF voltage amplitude with the new device is ± 6 10- 4 and the testing results are satisfactory.
In order to improve RF cavity amplitude stability of Separated Sector Cyclotron (SSC) of Heavy Ion Research Facility in Lanzhou (HIRFL) for increasing accelerator beam current intensity, a set of new RF amplitude stabilization device is developed. Compared with the former RF amplitude stabilization device, the new one is featured by its double stabilizing control loops and single chip micro-computer control mode. The stability of SSC RF voltage amplitude with the new device is ± 6 10- 4 and the testing results are satisfactory.
2001,
13.
Abstract:
Experiments on planar vircator were carried out on FLASH Ⅱ accelerator to find its frequency characteristics of the vircator. The results of the experiments were given in this paper. Multi frequencies were observed on planar vircator and they varied with the time in one pulse duration. The frequencies mainly cover C-band and X-band with the main frequency in C-band. The main frequency was produced by the oscillation of the virtual cathode and approximately equaled to the relativistic plasma frequency on it. According to experimental results, the main frequency of planar vircator was independent of the cathode area and anode material, and slightly depended upon the gap voltage, and was in inverse ratio with diode gap.
Experiments on planar vircator were carried out on FLASH Ⅱ accelerator to find its frequency characteristics of the vircator. The results of the experiments were given in this paper. Multi frequencies were observed on planar vircator and they varied with the time in one pulse duration. The frequencies mainly cover C-band and X-band with the main frequency in C-band. The main frequency was produced by the oscillation of the virtual cathode and approximately equaled to the relativistic plasma frequency on it. According to experimental results, the main frequency of planar vircator was independent of the cathode area and anode material, and slightly depended upon the gap voltage, and was in inverse ratio with diode gap.
2001,
13.
Abstract:
The paper introduces the characteristics of the electron gun used in the 9MeV traveling wave electron linear accelerator for fixed customs container inspection system. Wigh the scandate cathode, the electron gun meets the accelerator characteristics with the whole system not needing high-temperature roasting to degas. The electron gun can work normally at a vacuum of about 10- 5Pa and can be reinstalled after exposure to air. In the accelerator, the electron gun emits a beam which strikes the target to produce an X-ray beam with a dosage rate of over 30Gy/(min× m) and a beam focus spot of less than f 2mm. The EGUN code is used to simulate the structure and properties of the electron gun. The reference size debugging parameters for replacing the electron gun are given for assembly requirem
The paper introduces the characteristics of the electron gun used in the 9MeV traveling wave electron linear accelerator for fixed customs container inspection system. Wigh the scandate cathode, the electron gun meets the accelerator characteristics with the whole system not needing high-temperature roasting to degas. The electron gun can work normally at a vacuum of about 10- 5Pa and can be reinstalled after exposure to air. In the accelerator, the electron gun emits a beam which strikes the target to produce an X-ray beam with a dosage rate of over 30Gy/(min× m) and a beam focus spot of less than f 2mm. The EGUN code is used to simulate the structure and properties of the electron gun. The reference size debugging parameters for replacing the electron gun are given for assembly requirem
2001,
13.
Abstract:
According to the theory of diffraction, the distribution of laser intensity reflected from infrared system is analyzed. The diffraction pattern of spot center intensity in different transmission distance is studied and the relationship between spot intensity and radius is established. The reflection region can be divided into the transmission area, Fresnel diffraction area and Fraunhofer diffraction area. In Fresnel diffraction area, the intensity of spot center change light to dark. The intensity of spot center change violent vibration from 0~1km, and reach peak value between 1~3km, then reduce gradually with the reflection distance increasing. In Fraunhofer diffraction area, the spot center is light spot, around encircle light and dark ring.
According to the theory of diffraction, the distribution of laser intensity reflected from infrared system is analyzed. The diffraction pattern of spot center intensity in different transmission distance is studied and the relationship between spot intensity and radius is established. The reflection region can be divided into the transmission area, Fresnel diffraction area and Fraunhofer diffraction area. In Fresnel diffraction area, the intensity of spot center change light to dark. The intensity of spot center change violent vibration from 0~1km, and reach peak value between 1~3km, then reduce gradually with the reflection distance increasing. In Fraunhofer diffraction area, the spot center is light spot, around encircle light and dark ring.
2001,
13.
Abstract:
Experimental research of the slab cavity cleanliness of high power laser amplifiers is presented in this paper. The results indicate that materials within the slab cavity are readily pyrolyzed due to flashlamp high irradiance, and thus produce large quantity of airborne particles at the scale of micrometers. Experiments are carried out at two conditions, one of which is measuring the particles without nitrogen flushing, and the other is measuring the particles with several minutes of high flow nitrogen flushing slab cavity immediately after flashlamp pumping. Experimental results show that Class100,000~500,000 aerosols (diameter ³ 0.5m m) are usually produced immediately following the flashlamp firing. Flushing of the slab cavity with a high flow of filtered nitrogen can significantly
Experimental research of the slab cavity cleanliness of high power laser amplifiers is presented in this paper. The results indicate that materials within the slab cavity are readily pyrolyzed due to flashlamp high irradiance, and thus produce large quantity of airborne particles at the scale of micrometers. Experiments are carried out at two conditions, one of which is measuring the particles without nitrogen flushing, and the other is measuring the particles with several minutes of high flow nitrogen flushing slab cavity immediately after flashlamp pumping. Experimental results show that Class100,000~500,000 aerosols (diameter ³ 0.5m m) are usually produced immediately following the flashlamp firing. Flushing of the slab cavity with a high flow of filtered nitrogen can significantly
2001,
13.
Abstract:
Fast pulsed kicker magnets will be used to inject the full energy 3.5GeV beam into the Storage Ring in Shanghai Synchrotron Radiation Facility (SSRF). The kicker magnets in the Storage Ring are window frame type with a Ni-Zn ferrite core in air. The injection scheme is introduced in this thesis. The technical design of kicker hardware including magnets and pulse generators is presented and discussed. The basic requirement of a Ni-Zn ferrite core is given. The result of computer simulation for the pulse generators with PSpice program is shown. The OPERA-2D software is employed to compute the field flatness in the horizontal and median plane of the magnetic gap. As one of critical parts of the design in the kicker magnets of Storage Ring, the formulae of synchrotron radiation inside a cerami
Fast pulsed kicker magnets will be used to inject the full energy 3.5GeV beam into the Storage Ring in Shanghai Synchrotron Radiation Facility (SSRF). The kicker magnets in the Storage Ring are window frame type with a Ni-Zn ferrite core in air. The injection scheme is introduced in this thesis. The technical design of kicker hardware including magnets and pulse generators is presented and discussed. The basic requirement of a Ni-Zn ferrite core is given. The result of computer simulation for the pulse generators with PSpice program is shown. The OPERA-2D software is employed to compute the field flatness in the horizontal and median plane of the magnetic gap. As one of critical parts of the design in the kicker magnets of Storage Ring, the formulae of synchrotron radiation inside a cerami
2001,
13.
Abstract:
On the assumption of wavefront prolongation, a new optical phase retrieval algorithm by conventional lateral shear interferometer with wavelet transform is introduced. With this method, the device is remained, but the fast reconstruction of smooth wavefront also rough wavefront is realized. By computer simulation, its reconstruction precision is better than the polynomial fitting. In the measurement of inhomogeneous media, its result is reasonable.
On the assumption of wavefront prolongation, a new optical phase retrieval algorithm by conventional lateral shear interferometer with wavelet transform is introduced. With this method, the device is remained, but the fast reconstruction of smooth wavefront also rough wavefront is realized. By computer simulation, its reconstruction precision is better than the polynomial fitting. In the measurement of inhomogeneous media, its result is reasonable.
2001,
13.
Abstract:
On the base of physical simulation codes whose different output power and stimulating conditions coincided to the experiments, the codes for large and small bore copper vapor laser(CVL) were improved and could be used to a series of physical parameters with their figures. If a certain output power of CVL were needed, the lasing volume would be decided. After that if the diameter was given the input power density, the stimulating electric field, the frequency determined by the metastable copper and the wall temperature that decides the Copper vapor pressure were decided.
On the base of physical simulation codes whose different output power and stimulating conditions coincided to the experiments, the codes for large and small bore copper vapor laser(CVL) were improved and could be used to a series of physical parameters with their figures. If a certain output power of CVL were needed, the lasing volume would be decided. After that if the diameter was given the input power density, the stimulating electric field, the frequency determined by the metastable copper and the wall temperature that decides the Copper vapor pressure were decided.
2001,
13.
Abstract:
A kind of simple method is presented on the measurement of average velocity of flyer driven by mini size laser using quartz gauges. In the experiments, 5.5m m thickness and 0.5~0.8mm diameter of aluminum flyer have been driven successfully by mini size YAG laser in the energy range of 100~300mJ, the highest velocity of flyer have been up to 6.6km/s, and the relationship of flyer velocity and energy density have been obtained. The process of experiments and design of quartz sensor are introduced in detail in the article, and the analysis has made on the accuracy of experiment system and experimental data. It is proved that the method is simple and reliable, and can fit well the accuracy need of experiment.
A kind of simple method is presented on the measurement of average velocity of flyer driven by mini size laser using quartz gauges. In the experiments, 5.5m m thickness and 0.5~0.8mm diameter of aluminum flyer have been driven successfully by mini size YAG laser in the energy range of 100~300mJ, the highest velocity of flyer have been up to 6.6km/s, and the relationship of flyer velocity and energy density have been obtained. The process of experiments and design of quartz sensor are introduced in detail in the article, and the analysis has made on the accuracy of experiment system and experimental data. It is proved that the method is simple and reliable, and can fit well the accuracy need of experiment.
2001,
13.
Abstract:
Square pipe-array jet-type singlet oxygen generator (SPJSOG), which is invented by the authors, is a new efficient chemical energy provider for a chemical oxygen iodine laser (COIL). This paper describes a series of laser output experiments performed on a COIL equipped with an SPJSOG. The experimental investigation emphasized on the parameters and performance of the SPJSOG, and the corresponding chemical efficiency of COIL. Benefits of the SPJSOG were shown in the processes of manufacturing, assembly and integrated tests. With regular jets and high utilization of BHP (basic hydrogen peroxide) solution, the SPJSOG resulted in a COIL with chemical efficiency of 26%, which had a Cl2 flowrate of 0.25mol/s, a stable resonator, and no cold-trap.
Square pipe-array jet-type singlet oxygen generator (SPJSOG), which is invented by the authors, is a new efficient chemical energy provider for a chemical oxygen iodine laser (COIL). This paper describes a series of laser output experiments performed on a COIL equipped with an SPJSOG. The experimental investigation emphasized on the parameters and performance of the SPJSOG, and the corresponding chemical efficiency of COIL. Benefits of the SPJSOG were shown in the processes of manufacturing, assembly and integrated tests. With regular jets and high utilization of BHP (basic hydrogen peroxide) solution, the SPJSOG resulted in a COIL with chemical efficiency of 26%, which had a Cl2 flowrate of 0.25mol/s, a stable resonator, and no cold-trap.
2001,
13.
Abstract:
The residual phase error after correction for turbulence-induced phase aberrations by a partially compensating adaptive optics system (with temporal lag and limited space resolution) is computed by using the phase expansion on the Zernike polynomials in this paper. The computation can be used to derive the maximum order of aberration to be corrected to get the most from the compensation. The partially compensating adaptive optics system with Rayleigh beacon or sodium beacon as reference is computed also in this paper. The results show, the system with sodium beacon requires higher space frequency than the system with Rayleigh beacon. And the off-axis anisoplanatism effect due to the angular separation between the object and the beacon or the system temporal lag is more serious for the syst
The residual phase error after correction for turbulence-induced phase aberrations by a partially compensating adaptive optics system (with temporal lag and limited space resolution) is computed by using the phase expansion on the Zernike polynomials in this paper. The computation can be used to derive the maximum order of aberration to be corrected to get the most from the compensation. The partially compensating adaptive optics system with Rayleigh beacon or sodium beacon as reference is computed also in this paper. The results show, the system with sodium beacon requires higher space frequency than the system with Rayleigh beacon. And the off-axis anisoplanatism effect due to the angular separation between the object and the beacon or the system temporal lag is more serious for the syst
2001,
13.
Abstract:
The reflector array is used as pseudo phase conjugator in the common path/common mode adaptive optics system. The ability and the fidelity of the reflector array to provide pseudo phase conjugate of the incoming wave was analyzed. The phases of pseudo phase conjugate waves are simulated and the fidelities of different reflector arrays and different aberrations are calculated, while the aberration of the incoming wave is given in Zernike model. It is shown that the fidelity is determined not only by the cells’ number and arrangement of the retroreflector array, but also by the aberration itself. Different kinds of aberrations will have different fidelities. Factors such as diffraction, dihedral error, surface precision, which can influence the fidelity of the retroreflector array, are disc
The reflector array is used as pseudo phase conjugator in the common path/common mode adaptive optics system. The ability and the fidelity of the reflector array to provide pseudo phase conjugate of the incoming wave was analyzed. The phases of pseudo phase conjugate waves are simulated and the fidelities of different reflector arrays and different aberrations are calculated, while the aberration of the incoming wave is given in Zernike model. It is shown that the fidelity is determined not only by the cells’ number and arrangement of the retroreflector array, but also by the aberration itself. Different kinds of aberrations will have different fidelities. Factors such as diffraction, dihedral error, surface precision, which can influence the fidelity of the retroreflector array, are disc
2001,
13.
Abstract:
The elliptical flattened Gaussian beam (EFGB) is defined by using tensor method. The propagation formula and corresponding tensor ABCD law of EFGB passing through nonsymmetrical paraxial optical system is derived through vector integration. By using this formula, the propagation characteristics of EFGB through free-space are calculated and discussed. The results show that the propagation property is very different from those of circular flattened Gaussian beam or elliptical Gaussian beam, and is dependent on the order N. In the near field, the intensity distribution remains flat. With the increase of propagation distance, the flattened part degenerates. In the far field, EFGB tends to be elliptical Gaussian beam. Furthermore, beam spots of coupled EFGB rotate with propagation distance z.
The elliptical flattened Gaussian beam (EFGB) is defined by using tensor method. The propagation formula and corresponding tensor ABCD law of EFGB passing through nonsymmetrical paraxial optical system is derived through vector integration. By using this formula, the propagation characteristics of EFGB through free-space are calculated and discussed. The results show that the propagation property is very different from those of circular flattened Gaussian beam or elliptical Gaussian beam, and is dependent on the order N. In the near field, the intensity distribution remains flat. With the increase of propagation distance, the flattened part degenerates. In the far field, EFGB tends to be elliptical Gaussian beam. Furthermore, beam spots of coupled EFGB rotate with propagation distance z.
2001,
13.
Abstract:
The driving laser is very important in the CW-mode photoinjector. According to the requirement of the CW-mode photoinjector, the output of a CW mode-locked laser can be used as the laser seeds, amplified continuously , and frequency-converted to generate the driving laser. The seeding laser is the diode-pumped self mode-locked laser (GE-100), which can be synchronized to the driving signal through timing stablizer(CLX-100). The repetition rate of laser pulse can be changed from 81.25MHz to 10.16MHz by Pockels’cell, and every laser pulse is cotinuously amplified for 8 times. After forth harmonic, the laser pulse energy can reach 0.3m J at repetition rate of 10.16MHz, and the laser pulse-duration is 5ps.
The driving laser is very important in the CW-mode photoinjector. According to the requirement of the CW-mode photoinjector, the output of a CW mode-locked laser can be used as the laser seeds, amplified continuously , and frequency-converted to generate the driving laser. The seeding laser is the diode-pumped self mode-locked laser (GE-100), which can be synchronized to the driving signal through timing stablizer(CLX-100). The repetition rate of laser pulse can be changed from 81.25MHz to 10.16MHz by Pockels’cell, and every laser pulse is cotinuously amplified for 8 times. After forth harmonic, the laser pulse energy can reach 0.3m J at repetition rate of 10.16MHz, and the laser pulse-duration is 5ps.
2001,
13.
Abstract:
Different laser intensity distributions such as the beam with uniform profile, Gaussian, Super-Gaussian and flattened Gaussian beams are analyzed and compared. Under the same power and radius, the expressions of intensity distributions and beam fill factor varing with beam orders for these beams have been derived. In the heat conduction equation, laser beam with different special profiles as a surface heat source is included. Numerical calculations are performed to give the different thermal effects on a thin 30CrMnSiA metal slab induced by these beams.
Different laser intensity distributions such as the beam with uniform profile, Gaussian, Super-Gaussian and flattened Gaussian beams are analyzed and compared. Under the same power and radius, the expressions of intensity distributions and beam fill factor varing with beam orders for these beams have been derived. In the heat conduction equation, laser beam with different special profiles as a surface heat source is included. Numerical calculations are performed to give the different thermal effects on a thin 30CrMnSiA metal slab induced by these beams.
2001,
13.
Abstract:
The plasma characteristics of the bulk target irradiated by pulse laser is studied in detail, and the theoretical model of pulsed-laser-driven ablation is set up accordingly. In addition, the velocity distribution of the plasma is discussed. Moreover, the plasma density and temperature near the ablating surface as the function of time are discussed respectively by using hydrodynamic theory and the heat conduction equation. At the same time, our theoretical results are compared with our experiments and other authors’ conclusions.
The plasma characteristics of the bulk target irradiated by pulse laser is studied in detail, and the theoretical model of pulsed-laser-driven ablation is set up accordingly. In addition, the velocity distribution of the plasma is discussed. Moreover, the plasma density and temperature near the ablating surface as the function of time are discussed respectively by using hydrodynamic theory and the heat conduction equation. At the same time, our theoretical results are compared with our experiments and other authors’ conclusions.
2001,
13.
Abstract:
The wavefront power spectral density (PSD) is being adopted for specifying the large optical components employed in high power density solid-state laser for inertial confinement fusion (ICF). The phase wavefront detected by the interferometer is digitally processed to create the one dimension wavefront PSD. There’re anamorphic effects for measuring the wavefront’s components with high spatial frequencies. It’s necessary to calibrate the system transfer function of the interferometer. Based on the principle of phase comparing, we have designed and fabricated a 100-mm-diameter standard phase object that contained a step phase. The system transfer functions of the transmitted measuring mode and the reflective measuring mode for the WYKO 24-inch interferometer have been respectively obtaine
The wavefront power spectral density (PSD) is being adopted for specifying the large optical components employed in high power density solid-state laser for inertial confinement fusion (ICF). The phase wavefront detected by the interferometer is digitally processed to create the one dimension wavefront PSD. There’re anamorphic effects for measuring the wavefront’s components with high spatial frequencies. It’s necessary to calibrate the system transfer function of the interferometer. Based on the principle of phase comparing, we have designed and fabricated a 100-mm-diameter standard phase object that contained a step phase. The system transfer functions of the transmitted measuring mode and the reflective measuring mode for the WYKO 24-inch interferometer have been respectively obtaine
2001,
13.
Abstract:
Diode laser arrays side-pumped Nd:YAG slab double-pass laser power amplifier is studied in the paper .Experimental results and numerical simulations of laser performance are presented. MOPA system has been built up using gaussian beam as source. Over 51.9mJ energy per pulse at 100Hz repetition rate is achieved. Beam quality M2 is less than 2.The fluctuation of the laser output energy is less than 2%.The result shows that the experimental data have been consistent with the numerical calculation results.
Diode laser arrays side-pumped Nd:YAG slab double-pass laser power amplifier is studied in the paper .Experimental results and numerical simulations of laser performance are presented. MOPA system has been built up using gaussian beam as source. Over 51.9mJ energy per pulse at 100Hz repetition rate is achieved. Beam quality M2 is less than 2.The fluctuation of the laser output energy is less than 2%.The result shows that the experimental data have been consistent with the numerical calculation results.
2001,
13.
Abstract:
The operation voltage of high voltage DC power supply of plasma filled high power microwave source-PASOTRON is from –70kV up to –150kV, the total current is about 300A, while the modulator(current 60A, pulse width 60~120m s) is operating suspended on the HV-DC. In practice, if the strike arc occurs, there is a strong potential to destroy the microwave tube, high voltage DC power supply, modulator or/and modular circuit of the system. The protection system of the power supply, therefore, plays an important role in the operation of system. The special designed HV crowbar and a simple self-triggering circuit is applied, and a satisfied protection result is achieved. The experiments show that, 98% of the energy of the filtering capacitor would be bypassed by the crowbar after 150ns of the st
The operation voltage of high voltage DC power supply of plasma filled high power microwave source-PASOTRON is from –70kV up to –150kV, the total current is about 300A, while the modulator(current 60A, pulse width 60~120m s) is operating suspended on the HV-DC. In practice, if the strike arc occurs, there is a strong potential to destroy the microwave tube, high voltage DC power supply, modulator or/and modular circuit of the system. The protection system of the power supply, therefore, plays an important role in the operation of system. The special designed HV crowbar and a simple self-triggering circuit is applied, and a satisfied protection result is achieved. The experiments show that, 98% of the energy of the filtering capacitor would be bypassed by the crowbar after 150ns of the st
2001,
13.
Abstract:
For high power microwave application, the offset parabolic antennas have advantages of lower side lobes, lower standing wave ratio, high efficiency and avoiding breakdown comparing with the center feed parent. Without any rotary RF joint in the high power microwave transmit system, the scan can be achieved by spinning the reflector around the axe of the feed and swinging the reflector and feed around the focus in the (x, z) plane by using a vacuum flexible elliptical waveguide. By geometric approach, the scan functions are presented. The scan properties are characterized with the maximum elevation angle range at a definite distance. The renations between the scan characteristics and the antenna geometric and spin-swing parameters are given for the antenna design. The spin-swing single offs
For high power microwave application, the offset parabolic antennas have advantages of lower side lobes, lower standing wave ratio, high efficiency and avoiding breakdown comparing with the center feed parent. Without any rotary RF joint in the high power microwave transmit system, the scan can be achieved by spinning the reflector around the axe of the feed and swinging the reflector and feed around the focus in the (x, z) plane by using a vacuum flexible elliptical waveguide. By geometric approach, the scan functions are presented. The scan properties are characterized with the maximum elevation angle range at a definite distance. The renations between the scan characteristics and the antenna geometric and spin-swing parameters are given for the antenna design. The spin-swing single offs
2001,
13.
Abstract:
A relativistic electron beam is injected into a plasma whose density is lower than the beam’s density. The head of the electron beam pushes out the plasma electrons, leaving an ion channel. The ion focusing force is similar to the magnetic field in binding electrons. The dispersion equation of corrugated waveguide filled with plasma is derived. It is analyzed ty numerical computation that the performance of traveling wave tube (RTWT) amplifier is affected by geometry parameters of slow-wave structure, such as periods, depth of ripple and average radius of waveguide. The results are helpful for designing RTWT.
A relativistic electron beam is injected into a plasma whose density is lower than the beam’s density. The head of the electron beam pushes out the plasma electrons, leaving an ion channel. The ion focusing force is similar to the magnetic field in binding electrons. The dispersion equation of corrugated waveguide filled with plasma is derived. It is analyzed ty numerical computation that the performance of traveling wave tube (RTWT) amplifier is affected by geometry parameters of slow-wave structure, such as periods, depth of ripple and average radius of waveguide. The results are helpful for designing RTWT.
2001,
13.
Abstract:
Experimental Studies of relativistic BWO with a resonant reflector are presented. The resonant reflector is a circular wave-guide with longitudinal irregularity. The device emits TM01 microwave at 8.874GHz. The power of BWO is about 170MW at applied magnetic field Bz=0.7T, and 370MW at Bz=1.7T, both with microwave pulse duration of 10 ns. Experimental results show that BWO with resonant reflector works well at low applied magnetic field, and primary experimental studies will be the foundation of further research work.
Experimental Studies of relativistic BWO with a resonant reflector are presented. The resonant reflector is a circular wave-guide with longitudinal irregularity. The device emits TM01 microwave at 8.874GHz. The power of BWO is about 170MW at applied magnetic field Bz=0.7T, and 370MW at Bz=1.7T, both with microwave pulse duration of 10 ns. Experimental results show that BWO with resonant reflector works well at low applied magnetic field, and primary experimental studies will be the foundation of further research work.
2001,
13.
Abstract:
The mechanism of HPM pulse-duration damage effect on semiconductor component results from heat accumulation and diffusion process in the defect area. The experiential formulae of HPM pulse-duration damage effect in the range of whole pulse-duration, long pulse-duration as well as short pulse-duration are obtained, which agree with experiments and numerical simulation effect data very well.
The mechanism of HPM pulse-duration damage effect on semiconductor component results from heat accumulation and diffusion process in the defect area. The experiential formulae of HPM pulse-duration damage effect in the range of whole pulse-duration, long pulse-duration as well as short pulse-duration are obtained, which agree with experiments and numerical simulation effect data very well.
2001,
13.
Abstract:
In the process of implosion indirectly driven by laser, the high temperature and low density plasma produced by X-ray ablation is in the state of non-local thermodynamic equilibrium. And the propagation of X-ray needs to be treated by transportation method. X-ray energy flow reflected by plasma depends on the density, temperature of radiation and electrons, and their space profiles if the plasma produced by ablation is fully ionized. In addition, the plasma parameters in the region of rarefaction wave is determined by means of a simplified model. The approach to compute X-ray albedo is presented and the analytical formula of the albedo are given in this paper.
In the process of implosion indirectly driven by laser, the high temperature and low density plasma produced by X-ray ablation is in the state of non-local thermodynamic equilibrium. And the propagation of X-ray needs to be treated by transportation method. X-ray energy flow reflected by plasma depends on the density, temperature of radiation and electrons, and their space profiles if the plasma produced by ablation is fully ionized. In addition, the plasma parameters in the region of rarefaction wave is determined by means of a simplified model. The approach to compute X-ray albedo is presented and the analytical formula of the albedo are given in this paper.
2001,
13.
Abstract:
The DWBE method has been used to calculate the cross sections and of electron impact ionization of Alq+(q=1-12). We have related the scaled cross sections to the Bethe coefficients at high energy regime. The latter can be obtained by integral of cross section of photoionization. These cross sections are then fit to obtain corresponding rate coefficients. According to our calculations, the scaled cross sections vary slowly as the charge state change. Our results are in good agreement with those of experiment and other theoretical calculations.
The DWBE method has been used to calculate the cross sections and of electron impact ionization of Alq+(q=1-12). We have related the scaled cross sections to the Bethe coefficients at high energy regime. The latter can be obtained by integral of cross section of photoionization. These cross sections are then fit to obtain corresponding rate coefficients. According to our calculations, the scaled cross sections vary slowly as the charge state change. Our results are in good agreement with those of experiment and other theoretical calculations.
2001,
13.
Abstract:
We simulated radiation ablating Aluminum foil by using 1D muti-groups code(RDMG). With intense laser beams heating a gold hohlraum, the X-ray with intensity of 0.71 1014W× cm- 2 and pulse width 1.0ns emits from the hohlraum ablating 1.5m m and 3m m thick aluminum foil. The simulation investigates the radiation energy transport in hot dense mdium-Z matter (aluminum) and clearly shows the process of radiation heat wave passing through the aluminum foil. It has shown the sudden onset of X-ray flux from rear side of aluminum foil observed by experiments. The burn-through times predicted by the simulation fit well with the experimental results.
We simulated radiation ablating Aluminum foil by using 1D muti-groups code(RDMG). With intense laser beams heating a gold hohlraum, the X-ray with intensity of 0.71 1014W× cm- 2 and pulse width 1.0ns emits from the hohlraum ablating 1.5m m and 3m m thick aluminum foil. The simulation investigates the radiation energy transport in hot dense mdium-Z matter (aluminum) and clearly shows the process of radiation heat wave passing through the aluminum foil. It has shown the sudden onset of X-ray flux from rear side of aluminum foil observed by experiments. The burn-through times predicted by the simulation fit well with the experimental results.
