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RSS2006 Vol. 18, No. 02
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2006,
18.
Abstract:
numberical simulation method of Mikhailovskii's physics model about dispersion laws of relativistic plasma of Fermi distribution is presented and the method is proved peasible. The result of the method inosculates with the result of Mikhailovskii's theory in the ultrarelativisty. We get the dispersion laws which Mikhailovskii can't get in his theory. The dispersion laws in different temperature are also obtained by using the numerical simulation method.
numberical simulation method of Mikhailovskii's physics model about dispersion laws of relativistic plasma of Fermi distribution is presented and the method is proved peasible. The result of the method inosculates with the result of Mikhailovskii's theory in the ultrarelativisty. We get the dispersion laws which Mikhailovskii can't get in his theory. The dispersion laws in different temperature are also obtained by using the numerical simulation method.
2006,
18.
Abstract:
In this paper we reported a ring-shaped LaB6 cathode with a large emission area of 115 mm2. The direct emission current density of the LaB6 was more than 40 A/cm2 when the temperature of LaB6 was 1 873 K. The heating power for the LaB6 cathode was only 173 W when the temperature of LaB6 cathode was as high as 1 873 K, in which an electron beam source was employed as the heater. The heating power decreased 66%, compared to that when the conversional graphite acted as the heater. It presented excellent emitting performance even after the cathode was exposed to the air many times.
In this paper we reported a ring-shaped LaB6 cathode with a large emission area of 115 mm2. The direct emission current density of the LaB6 was more than 40 A/cm2 when the temperature of LaB6 was 1 873 K. The heating power for the LaB6 cathode was only 173 W when the temperature of LaB6 cathode was as high as 1 873 K, in which an electron beam source was employed as the heater. The heating power decreased 66%, compared to that when the conversional graphite acted as the heater. It presented excellent emitting performance even after the cathode was exposed to the air many times.
2006,
18.
Abstract:
United with RKR potential function and the newest EDMF, the program Level developed by Prof. Le Roy of Canada to calculate bi-molecule spectroscopic constants was used to compute the Einstein spontaneous emission coefficients(A coefficients) for fundamental band transitions with vibrational energy level of V<6. The database of HCl's A coefficients was retrieved, and it seemed that Level is a rather simple but robust tool for quantum electronics researchers.
United with RKR potential function and the newest EDMF, the program Level developed by Prof. Le Roy of Canada to calculate bi-molecule spectroscopic constants was used to compute the Einstein spontaneous emission coefficients(A coefficients) for fundamental band transitions with vibrational energy level of V<6. The database of HCl's A coefficients was retrieved, and it seemed that Level is a rather simple but robust tool for quantum electronics researchers.
2006,
18.
Abstract:
The spectrum of incident electrons and emitted photons on the anode surface of the diode were calculated and analyzed by Monte Carlo Code MCNP/4C and Matlab, according to relations between the structure, operation parameters of the diodes and emitted electrons and photons spectrum. The parameters for single pulse obtained by several shots were compared, and the distributions of the electron and photon spectrum generated by each shot were calculated. It was investigated that variations of the electrical parameters in the operation of the intense diode influence the stability of the pulsed X-ray spectrum. The result shows that the stability is good with small variations of the electrical parameters of diode.
The spectrum of incident electrons and emitted photons on the anode surface of the diode were calculated and analyzed by Monte Carlo Code MCNP/4C and Matlab, according to relations between the structure, operation parameters of the diodes and emitted electrons and photons spectrum. The parameters for single pulse obtained by several shots were compared, and the distributions of the electron and photon spectrum generated by each shot were calculated. It was investigated that variations of the electrical parameters in the operation of the intense diode influence the stability of the pulsed X-ray spectrum. The result shows that the stability is good with small variations of the electrical parameters of diode.
2006,
18.
Abstract:
This paper depicts in brief the basic information of ACTEL's antifuse-based FPGA(field programmable gate array)and the working theory of FPGA delay circuits. The method of measurement of FPGA delay circuits on Qiangguang Ⅰgenerator is discussed. And some of the results are presented. The analysis shows that γ transient radiation will destroy a signal period state, so, to some extent, there is a possibility of disabled FPGA function. However, as a whole, the performance of FPGA is better than many other CMOS large scale integrated circuit at high γ dose rate.
This paper depicts in brief the basic information of ACTEL's antifuse-based FPGA(field programmable gate array)and the working theory of FPGA delay circuits. The method of measurement of FPGA delay circuits on Qiangguang Ⅰgenerator is discussed. And some of the results are presented. The analysis shows that γ transient radiation will destroy a signal period state, so, to some extent, there is a possibility of disabled FPGA function. However, as a whole, the performance of FPGA is better than many other CMOS large scale integrated circuit at high γ dose rate.
2006,
18.
Abstract:
In this paper, the simulation of interaction between scintillation fibers and 14 MeV neutrons after penetrating through objects is presented. The neutron radiation is converted to green light (496 nm) in scintillation fibers, and the number of photons in each fiber is calculated. In simulated experiments, factors influencing quality of images are analyzed. The variation of the number of scattered neutrons into the scintillator with the distance between objects and the scintillator is calculated, and the results indicate that, for a distance of several centimeters, the influence of scattered neutrons to the image can be ignored. The simulation also indicates that for a certain number range of incident neutrons, the threshold thickness of objects which can be discriminated is approximately l
In this paper, the simulation of interaction between scintillation fibers and 14 MeV neutrons after penetrating through objects is presented. The neutron radiation is converted to green light (496 nm) in scintillation fibers, and the number of photons in each fiber is calculated. In simulated experiments, factors influencing quality of images are analyzed. The variation of the number of scattered neutrons into the scintillator with the distance between objects and the scintillator is calculated, and the results indicate that, for a distance of several centimeters, the influence of scattered neutrons to the image can be ignored. The simulation also indicates that for a certain number range of incident neutrons, the threshold thickness of objects which can be discriminated is approximately l
2006,
18.
Abstract:
Phase locking of a diode laser array in an external Talbot cavity was studied. Far field distributions of in-phase mode and out-of-phase mode were calculated using Fresnel diffraction formula of one-dimension on the basis of near field amplitude distribution. According to the distributions of the in-phase mode and out-of-phase mode in fraction Talbot cavity, a tilted external cavity mirror of 1/2 Talbot cavity was adopted, which made the in-phase mode be selected and the loss of the mode be lowered. In order to let the feedback light be injected into the elements effectively in this experiment, a “sandwich” construction of composite diamond is utilized to package the diode laser array which has obviously eliminated the “smile” effect. Phase locking of in-phase mode is obtained in the e
Phase locking of a diode laser array in an external Talbot cavity was studied. Far field distributions of in-phase mode and out-of-phase mode were calculated using Fresnel diffraction formula of one-dimension on the basis of near field amplitude distribution. According to the distributions of the in-phase mode and out-of-phase mode in fraction Talbot cavity, a tilted external cavity mirror of 1/2 Talbot cavity was adopted, which made the in-phase mode be selected and the loss of the mode be lowered. In order to let the feedback light be injected into the elements effectively in this experiment, a “sandwich” construction of composite diamond is utilized to package the diode laser array which has obviously eliminated the “smile” effect. Phase locking of in-phase mode is obtained in the e
2006,
18.
Abstract:
The surface reflectivity change process of the 45# steel irradiated by repetitive pulse laser in atmosphere is studied by the measurement of the reflectivity and the metallographical and surface energy spectrum analysis of the recovered samples. The physiochemical mechanism of the processes of the 45# steel interacting with the laser in the atmosphere can be obtained by comparing the theory result with the experiment result.It can explain the change of the surface reflectance taking into account the temperature rise of the surface and the formation of the surface oxidant simultaneously.
The surface reflectivity change process of the 45# steel irradiated by repetitive pulse laser in atmosphere is studied by the measurement of the reflectivity and the metallographical and surface energy spectrum analysis of the recovered samples. The physiochemical mechanism of the processes of the 45# steel interacting with the laser in the atmosphere can be obtained by comparing the theory result with the experiment result.It can explain the change of the surface reflectance taking into account the temperature rise of the surface and the formation of the surface oxidant simultaneously.
2006,
18.
Abstract:
This paper selects the Blumlein circuit as the main discharge circuit and sets up the discretization equivalent model for the Blumlein circuit. The simulation and the optimum design of the circuit are carried out by using this model. A group of circuit component parameters are selected as the basis of mounting and adjusting the discharge circuit. The transmission line capacitor and stored capacitor are designed to reduce the parasitic parameters of the circuit and enhance the performance of the circuit. Experiment results indicate that the output voltage rising edge of the discharge power supply reaches the goal(5.08 ns) of the design, and that the discharge power supply works stably and plays an important role in S2 laser device.
This paper selects the Blumlein circuit as the main discharge circuit and sets up the discretization equivalent model for the Blumlein circuit. The simulation and the optimum design of the circuit are carried out by using this model. A group of circuit component parameters are selected as the basis of mounting and adjusting the discharge circuit. The transmission line capacitor and stored capacitor are designed to reduce the parasitic parameters of the circuit and enhance the performance of the circuit. Experiment results indicate that the output voltage rising edge of the discharge power supply reaches the goal(5.08 ns) of the design, and that the discharge power supply works stably and plays an important role in S2 laser device.
2006,
18.
Abstract:
The principle to measure the impulse coupling coefficients of laser propulsion with a pendulum system was provided. The impulse coupling coefficients of a parabol laser propulsion thruster were measured with a pendulum system using air, He, N2 or Ar as propellant respectively. The experimental results indicated that the coupling coefficient of the laser propulsion was the highest when the propellant was Ar and it was the lowest when the propellant was He. The relative error of the impulse coupling coefficient was 5.4%~6.4%.
The principle to measure the impulse coupling coefficients of laser propulsion with a pendulum system was provided. The impulse coupling coefficients of a parabol laser propulsion thruster were measured with a pendulum system using air, He, N2 or Ar as propellant respectively. The experimental results indicated that the coupling coefficient of the laser propulsion was the highest when the propellant was Ar and it was the lowest when the propellant was He. The relative error of the impulse coupling coefficient was 5.4%~6.4%.
2006,
18.
Abstract:
The theories of cuneiform prism and series neutral glass slices used as laser attenuator are analyzed in this paper. An aberration-free laser quantitative attenuator made of cuneiform prism is adopted and a series of neutral attenuated slices are used for adjusting laser-beam enegy at the same time. The M2-factor of the Hermite-Gaussian beams generated by an LD-pumped mode master is measured and it has been verified that the cuneiform prism used as reflection laser attenuator of 4.3% 0<θi<55° has no distinct influence on the beam quality and the neutral glass slices have accurate adjusted the operation for laser beam energy. More powerful attenuator can be obtained by using the combination of multi-cuneiform prism. The precision control of the laser beam power was realized with neutral g
The theories of cuneiform prism and series neutral glass slices used as laser attenuator are analyzed in this paper. An aberration-free laser quantitative attenuator made of cuneiform prism is adopted and a series of neutral attenuated slices are used for adjusting laser-beam enegy at the same time. The M2-factor of the Hermite-Gaussian beams generated by an LD-pumped mode master is measured and it has been verified that the cuneiform prism used as reflection laser attenuator of 4.3% 0<θi<55° has no distinct influence on the beam quality and the neutral glass slices have accurate adjusted the operation for laser beam energy. More powerful attenuator can be obtained by using the combination of multi-cuneiform prism. The precision control of the laser beam power was realized with neutral g
2006,
18.
Abstract:
The nozzle is one of the most important parts of a laser thruster. It can be designed with the focusing system together. It can also be designed independently without considering the focusing system. For the latter case, an ignition mode was set up with an auxiliary focusing system. By changing the parameters of the nozzle, the relationship between the impulse coupling coefficient and two dimensionless parameters, the ratio of the head diameter to the exit diameter of the nozzle and the ratio of the nozzle length to the exit diameter of the nozzle, was obtained. The reasons why the parameters of nozzle structure affect the impulse coupling coefficient were explained. The results show that the propulsion performance of the rotary trapezium nozzle is better than that of the column nozzle or
The nozzle is one of the most important parts of a laser thruster. It can be designed with the focusing system together. It can also be designed independently without considering the focusing system. For the latter case, an ignition mode was set up with an auxiliary focusing system. By changing the parameters of the nozzle, the relationship between the impulse coupling coefficient and two dimensionless parameters, the ratio of the head diameter to the exit diameter of the nozzle and the ratio of the nozzle length to the exit diameter of the nozzle, was obtained. The reasons why the parameters of nozzle structure affect the impulse coupling coefficient were explained. The results show that the propulsion performance of the rotary trapezium nozzle is better than that of the column nozzle or
2006,
18.
Abstract:
The abnormal responsive mechanism of photoconductive semiconductor detectors irradiated by off-band laser, hot electron photoconductivity, was proposed. The response of a photoconductive semiconductor detector under off-band laser irradiation is different from that under in-band laser irradiation. Heat effect in detectors was considered simultaneously under high power laser irradiation. The outputs of the detector were calculated accordingly. The calculated results show that the production of hot electrons causes the conductivity to decrease when a photoconductive HgCdTe detector is irradiated by off-band laser and that the resistance and the output of the detector are increased consequently.
The abnormal responsive mechanism of photoconductive semiconductor detectors irradiated by off-band laser, hot electron photoconductivity, was proposed. The response of a photoconductive semiconductor detector under off-band laser irradiation is different from that under in-band laser irradiation. Heat effect in detectors was considered simultaneously under high power laser irradiation. The outputs of the detector were calculated accordingly. The calculated results show that the production of hot electrons causes the conductivity to decrease when a photoconductive HgCdTe detector is irradiated by off-band laser and that the resistance and the output of the detector are increased consequently.
2006,
18.
Abstract:
Based on the traditional Shark-Hartmann wave-front measurement, a wave-front measuring method suitable for large scale telescope system was proposed. A set of pentagonal prism beam turning devices were introduced to transfer quasi-reference beam to scan every sub-aperture, and an improved S-H sensor was used to measure the wave-front of every sub-aperture. The wave-front measuring errors, which were induced by the manufacturing and kinetic errors of pentagonal prism, were theoretically analyzed and proved to be correct by a wave-front compensation method. The errors of self-wavefront of large scale telescope was reproduced availably. The method can be applied to measuring the wave-front of large scale telescope.
Based on the traditional Shark-Hartmann wave-front measurement, a wave-front measuring method suitable for large scale telescope system was proposed. A set of pentagonal prism beam turning devices were introduced to transfer quasi-reference beam to scan every sub-aperture, and an improved S-H sensor was used to measure the wave-front of every sub-aperture. The wave-front measuring errors, which were induced by the manufacturing and kinetic errors of pentagonal prism, were theoretically analyzed and proved to be correct by a wave-front compensation method. The errors of self-wavefront of large scale telescope was reproduced availably. The method can be applied to measuring the wave-front of large scale telescope.
2006,
18.
Abstract:
An effective gain of 23.8 cm-1 has been got at 1.2×1013 W·cm-2. In this paper, using series codes, quasi-stable Ni-like Ag collisional excitation scheme driven by laser with grazing incidence is studied. Compared with normal incidence, at a drive intensity of 4.3×1013 W·cm-2, the laser energy is mainly deposited on the gain region. The electronic temperature on gain region can be dramatically increased and the gain coefficients can also be dramatically increased. Its effective gain reaches 40 cm-1, which is 3.4 times of that of normal incidence. If 50 J laser energy is used to drive a single target, deeply saturated gain with a gain length product of 40 can be got.
An effective gain of 23.8 cm-1 has been got at 1.2×1013 W·cm-2. In this paper, using series codes, quasi-stable Ni-like Ag collisional excitation scheme driven by laser with grazing incidence is studied. Compared with normal incidence, at a drive intensity of 4.3×1013 W·cm-2, the laser energy is mainly deposited on the gain region. The electronic temperature on gain region can be dramatically increased and the gain coefficients can also be dramatically increased. Its effective gain reaches 40 cm-1, which is 3.4 times of that of normal incidence. If 50 J laser energy is used to drive a single target, deeply saturated gain with a gain length product of 40 can be got.
2006,
18.
Abstract:
Using di-ethoxy-silicane as precursor, a colloidal prepolymer was developed from sol-gel process. With silica colloid as modifier, the modified moisture-resistant films were prepared on neodymium-doped phosphate glass by spin coating. When the mole ratio of di-ethoxy-silicane to silica was 1∶1, the films after cure had improved abrasion-resistance. RMS was 1.245 nm, while laser-damage threshold value more than 15 J/cm2 at the condition of 1 053 nm, 1 ns. After staying in a closed circumstance at 80 ℃ and 95%RH, the films had approximately constant transmission and contact angle. It indicates that the films have a stable hydrophobic structure, good moisture-resistance, improved abrasion-resistant feature and longer service life.
Using di-ethoxy-silicane as precursor, a colloidal prepolymer was developed from sol-gel process. With silica colloid as modifier, the modified moisture-resistant films were prepared on neodymium-doped phosphate glass by spin coating. When the mole ratio of di-ethoxy-silicane to silica was 1∶1, the films after cure had improved abrasion-resistance. RMS was 1.245 nm, while laser-damage threshold value more than 15 J/cm2 at the condition of 1 053 nm, 1 ns. After staying in a closed circumstance at 80 ℃ and 95%RH, the films had approximately constant transmission and contact angle. It indicates that the films have a stable hydrophobic structure, good moisture-resistance, improved abrasion-resistant feature and longer service life.
2006,
18.
Abstract:
The flat crystal spectrometer is one of the fundamental tools to diagnose X-ray. Quasi-quantitative and quantitative analyses of X-ray spectra require calibrations of the flat crystal’s characteristic parameters, such as integral reflective coefficient and FWHM of the flat crystal’s rocking curve. Using BSRF 3B3 beam as the X-ray source, this article gives an indirect method to calibrate the flat PET crystal. Good results are obtained in the range of 2.1~6.0 keV and interrelated analysis is provided.
The flat crystal spectrometer is one of the fundamental tools to diagnose X-ray. Quasi-quantitative and quantitative analyses of X-ray spectra require calibrations of the flat crystal’s characteristic parameters, such as integral reflective coefficient and FWHM of the flat crystal’s rocking curve. Using BSRF 3B3 beam as the X-ray source, this article gives an indirect method to calibrate the flat PET crystal. Good results are obtained in the range of 2.1~6.0 keV and interrelated analysis is provided.
2006,
18.
Abstract:
To resolve the problem of phase separation in PMMA/SiO2 hybrids system, different polymethyl methacrylate(PMMA)/SiO2 hybrids were prepared by synchronous sol-gel process. There is a covalent bond between PMMA and SiO2. The samples were characterized by transmission electron microscopy (TEM), X-ray diffraction (XRD ), Fourier transformed infrared spectrum (FTIR) and thermal gravity(TG). The results show that when the silica content is between 20%~60%, there is no phase separation in the PMMA/SiO2 hybrid system.and the transparency of PMMA/SiO2 hybrid material is good when the silica content is between 20%~40%.
To resolve the problem of phase separation in PMMA/SiO2 hybrids system, different polymethyl methacrylate(PMMA)/SiO2 hybrids were prepared by synchronous sol-gel process. There is a covalent bond between PMMA and SiO2. The samples were characterized by transmission electron microscopy (TEM), X-ray diffraction (XRD ), Fourier transformed infrared spectrum (FTIR) and thermal gravity(TG). The results show that when the silica content is between 20%~60%, there is no phase separation in the PMMA/SiO2 hybrid system.and the transparency of PMMA/SiO2 hybrid material is good when the silica content is between 20%~40%.
2006,
18.
Abstract:
The CCD’s optics-electron characteristic is an important parameter when it is applied to measuring the energy distribution of laser’s far-field and near-field. A new method of calibrating the CCD’s optics-electron characteristic is introduced in this paper. The method uses the zeroth order energy-distribution caused by the pinhole diffraction as the CCD’s fiducial input energy. According to the CCD’s output data sampling the pinhole diffraction, the optics-electron characteristic curve is calculated through the least-square algorithm. The data process procedure, the validation experimental result and the analysis of its residual error are presented.
The CCD’s optics-electron characteristic is an important parameter when it is applied to measuring the energy distribution of laser’s far-field and near-field. A new method of calibrating the CCD’s optics-electron characteristic is introduced in this paper. The method uses the zeroth order energy-distribution caused by the pinhole diffraction as the CCD’s fiducial input energy. According to the CCD’s output data sampling the pinhole diffraction, the optics-electron characteristic curve is calculated through the least-square algorithm. The data process procedure, the validation experimental result and the analysis of its residual error are presented.
2006,
18.
Abstract:
Coupling efficiencies of TE11 and TM01 modes oscillating with radial injected electron beam in coaxial vircator present nearly the same value for coaxial geometry. 3D PIC simulation result shows that non-poloidal uniform mode dominates the output power. The effect of TE11 mode oscillating with injected electron beam on the performance of coaxial vircator can not be ignored. By introducing an unsymmetrical geometry and a TE11 mode reflector, the coupling efficiency between electron beam and TM01 mode is restrained. Consequently, the modes competition in the beam-EM wave interaction cavity is quenched, which leads to the increase of the energy conversion efficiency. The TE11 mode enhanced coaxial vircator with a non-coaxial geometry gives the power efficiency of 7% and 1.0 GW output pow
Coupling efficiencies of TE11 and TM01 modes oscillating with radial injected electron beam in coaxial vircator present nearly the same value for coaxial geometry. 3D PIC simulation result shows that non-poloidal uniform mode dominates the output power. The effect of TE11 mode oscillating with injected electron beam on the performance of coaxial vircator can not be ignored. By introducing an unsymmetrical geometry and a TE11 mode reflector, the coupling efficiency between electron beam and TM01 mode is restrained. Consequently, the modes competition in the beam-EM wave interaction cavity is quenched, which leads to the increase of the energy conversion efficiency. The TE11 mode enhanced coaxial vircator with a non-coaxial geometry gives the power efficiency of 7% and 1.0 GW output pow
2006,
18.
Abstract:
A virtual cathode oscillator (VCO) with an axially extracted TE10 mode of rectangular waveguide is investigated by PIC simulation which emits microwaves axially through an antenna without mode converter or transition waveguide, making the system more simple and compact. A microwave power of 500 MW is obtained with an electron beam of 400 keV and 8.9 kA, which can be obtained experimentally from the TomaChan accelerator. The beam-to-microwave efficiency is 14%. The frequency and mode of the generated microwave are very pure. These results can provide a possible method for building a compact high-power microwave device.
A virtual cathode oscillator (VCO) with an axially extracted TE10 mode of rectangular waveguide is investigated by PIC simulation which emits microwaves axially through an antenna without mode converter or transition waveguide, making the system more simple and compact. A microwave power of 500 MW is obtained with an electron beam of 400 keV and 8.9 kA, which can be obtained experimentally from the TomaChan accelerator. The beam-to-microwave efficiency is 14%. The frequency and mode of the generated microwave are very pure. These results can provide a possible method for building a compact high-power microwave device.
2006,
18.
Abstract:
The preliminary design of a new high-power low-pressure plasma-cathode e-gun is presented. Based on the hollow cathode effect and low-pressure glow discharge empirical formulas, the hollow cathode, the accelerating gap, and the working gas pressure region are given. The general experimental device of the low-pressure plasma cathode electron-gun generating high current density e-beam source is shown. Experiments has been done in continuous filled-in gases and gases-puff condition, and the discharging current of 150~200 A, the width of 60 μs and the collector current of 30~80 A, the width of 60 μs are obtaind. The results show that the new plasma cathode e-gun can take the place of material cathode e-gun, especially in plasma filled microwave tubes.
The preliminary design of a new high-power low-pressure plasma-cathode e-gun is presented. Based on the hollow cathode effect and low-pressure glow discharge empirical formulas, the hollow cathode, the accelerating gap, and the working gas pressure region are given. The general experimental device of the low-pressure plasma cathode electron-gun generating high current density e-beam source is shown. Experiments has been done in continuous filled-in gases and gases-puff condition, and the discharging current of 150~200 A, the width of 60 μs and the collector current of 30~80 A, the width of 60 μs are obtaind. The results show that the new plasma cathode e-gun can take the place of material cathode e-gun, especially in plasma filled microwave tubes.
2006,
18.
Abstract:
In this paper, a linear theory is presented of a relativistic high power microwave generator with coaxial slow wave structure. The space-charge-limiting current of a coaxial cylindrical waveguide is derived, which is larger than that of a hollow cylindrical waveguide. Thus, the electron beam in the former has more kinetic energy than that in the latter when the cathode potential and the current are the same and the coaxial device might obtain higher beam-wave conversion efficiency. Also derived is the dispersion relation for a coaxial cylindrical waveguide with sinusoidally varying wall radii. For the case of dispersion relation without considering the beam space charge effect, the theoretical results agree very well with the simulation results with Superfish. According to the numerical so
In this paper, a linear theory is presented of a relativistic high power microwave generator with coaxial slow wave structure. The space-charge-limiting current of a coaxial cylindrical waveguide is derived, which is larger than that of a hollow cylindrical waveguide. Thus, the electron beam in the former has more kinetic energy than that in the latter when the cathode potential and the current are the same and the coaxial device might obtain higher beam-wave conversion efficiency. Also derived is the dispersion relation for a coaxial cylindrical waveguide with sinusoidally varying wall radii. For the case of dispersion relation without considering the beam space charge effect, the theoretical results agree very well with the simulation results with Superfish. According to the numerical so
2006,
18.
Abstract:
A new method, the field analysis method is used to calculate the gap-impedance in a klystron output circuit based on the analysis of the electromagnetic field components and microwave circuit theory. The impedance superposition method is presented for an output cavity where several resonant modes overlap. The bunched electron beams will interact with all the existing modes and the sum of the gap-impedance in each mode constitutes the overall gap-impedance in the output cavity. This principle can also be used to calculate the imaginary part for a given real part of the gap-impedance. An example illustrates that the maximum resulting error between the field analysis method and the equivalent gap impedance method is less than 1.5%, and the maximum error between the mode overlapping method and
A new method, the field analysis method is used to calculate the gap-impedance in a klystron output circuit based on the analysis of the electromagnetic field components and microwave circuit theory. The impedance superposition method is presented for an output cavity where several resonant modes overlap. The bunched electron beams will interact with all the existing modes and the sum of the gap-impedance in each mode constitutes the overall gap-impedance in the output cavity. This principle can also be used to calculate the imaginary part for a given real part of the gap-impedance. An example illustrates that the maximum resulting error between the field analysis method and the equivalent gap impedance method is less than 1.5%, and the maximum error between the mode overlapping method and
2006,
18.
Abstract:
In this paper, experimental findings on the coaxial virtual cathode oscillator at Institute of Applied Electronics of CAEP are reported. The experiments show that the output microwave power and spectrum of a coaxial vircator with the reflector are evidently superior to those of a coaxial vircator without the reflector. With 350 kV diode voltage and 23 kA diode current, 500 MW output microwave at 3.3 GHz is obtained, and the conversion efficiency is about 6.2%. The cavity resonance effect on the coaxial virtual cathode oscillator is investigated.
In this paper, experimental findings on the coaxial virtual cathode oscillator at Institute of Applied Electronics of CAEP are reported. The experiments show that the output microwave power and spectrum of a coaxial vircator with the reflector are evidently superior to those of a coaxial vircator without the reflector. With 350 kV diode voltage and 23 kA diode current, 500 MW output microwave at 3.3 GHz is obtained, and the conversion efficiency is about 6.2%. The cavity resonance effect on the coaxial virtual cathode oscillator is investigated.
2006,
18.
Abstract:
An L-band 100 kW multi-beam klystron electron optics system was simulated using MAFIA, to which a MACRO program had been added. The effect of three-dimensional magnetic field on electron trajectories was analyzed. Among the center beam, inner beam and outer beam, with the increase of the distances between the main axis and the axes of the beams, the transverse magnetic field becomes stronger gradually, the wave amplitude of the electron beam becomes larger, and the laminar characteristics become worse. Eighteen beams were also simulated and the results showed that the beams scattered uniformly at the entrance of the collector.
An L-band 100 kW multi-beam klystron electron optics system was simulated using MAFIA, to which a MACRO program had been added. The effect of three-dimensional magnetic field on electron trajectories was analyzed. Among the center beam, inner beam and outer beam, with the increase of the distances between the main axis and the axes of the beams, the transverse magnetic field becomes stronger gradually, the wave amplitude of the electron beam becomes larger, and the laminar characteristics become worse. Eighteen beams were also simulated and the results showed that the beams scattered uniformly at the entrance of the collector.
2006,
18.
Abstract:
In this paper, a measurement system of UWS electromagnetic pulse radiating field is developed, which consisted of TEM horn, coaxial transmitting line, wide band oscillograph and data processing software for the compensation of signal attenuation and aberration. The TEM horn is fed vertically through coaxial line, its upper plate is an isosceles-triangle metal plate and lower plate is a rectangular metal plate. LabView is adopted to compile the data processing software. Pulses with base width from 300 ps to 4 ns can be measured accurately by using the system. The radiating field produced by a reflector antenna is measured，the experimental results show that the system has the characteristics of both the high waveform fidelity and the wide band. It can be applied in research of pulse radiati
In this paper, a measurement system of UWS electromagnetic pulse radiating field is developed, which consisted of TEM horn, coaxial transmitting line, wide band oscillograph and data processing software for the compensation of signal attenuation and aberration. The TEM horn is fed vertically through coaxial line, its upper plate is an isosceles-triangle metal plate and lower plate is a rectangular metal plate. LabView is adopted to compile the data processing software. Pulses with base width from 300 ps to 4 ns can be measured accurately by using the system. The radiating field produced by a reflector antenna is measured，the experimental results show that the system has the characteristics of both the high waveform fidelity and the wide band. It can be applied in research of pulse radiati
2006,
18.
Abstract:
The helical array antenna fed from radial waveguide is a kind of new antenna to realize the directional radiation of high power microwave. In this paper, the optimized simulation result of a helical array antenna fed from double-layered radial waveguide is presented and some experiment researches are developed for an antenna fabricated according to simulated structure. During experiment researches, an impedance converter is designed to connect the standard port with the antenna input port, and the method of comparing with standard linear polarized antenna is used to measure array antenna circular polarized gain. The experiment result shows that, in the range of 3.8 GHz to 4.2 GHz, the antenna gain is over 19.7 dB, the antenna aperture efficiency is over 42%, the antenna axial ratio is belo
The helical array antenna fed from radial waveguide is a kind of new antenna to realize the directional radiation of high power microwave. In this paper, the optimized simulation result of a helical array antenna fed from double-layered radial waveguide is presented and some experiment researches are developed for an antenna fabricated according to simulated structure. During experiment researches, an impedance converter is designed to connect the standard port with the antenna input port, and the method of comparing with standard linear polarized antenna is used to measure array antenna circular polarized gain. The experiment result shows that, in the range of 3.8 GHz to 4.2 GHz, the antenna gain is over 19.7 dB, the antenna aperture efficiency is over 42%, the antenna axial ratio is belo
2006,
18.
Abstract:
Studies were carried out to optimize the operation of a high-voltage and high-repetition-rate trigatron switch, including optimization of the insulation structure, the diameter of the trigger hole and the position of the trigger electrode. Some experiments were performed with the designed switch, and the experimental results were discussed. The experimental results prove that the switch can operate steadily at voltage up to 1.1 MV, peak current up to about 13.8 kA, and repetition rate up to 100 Hz. The switch has been successfully used in a repetitive high-current e-beam accelerator CHP01.
Studies were carried out to optimize the operation of a high-voltage and high-repetition-rate trigatron switch, including optimization of the insulation structure, the diameter of the trigger hole and the position of the trigger electrode. Some experiments were performed with the designed switch, and the experimental results were discussed. The experimental results prove that the switch can operate steadily at voltage up to 1.1 MV, peak current up to about 13.8 kA, and repetition rate up to 100 Hz. The switch has been successfully used in a repetitive high-current e-beam accelerator CHP01.
2006,
18.
Abstract:
In BEPC, the oscillation information of the beam position of a single bunch in every turn can be tracked by the bunch-by-bunch system, through which the relationships between the transverse damping time and the beam current, chromaticity, octupole current and beam energy were obtained. The radiation damping time acquired in the experiment was 52 ms. The data analysis result of the bunch-by-bunch tracking experiment indicates that the higher the beam current is and the higher the chromaticity is, the higher the damping ratio is, and that the change of the octupole current has little influence on the damping ratio when the beam current is 4.7 mA. The damping ratio decreases with the rising of the beam energy when the beam current is 5 mA.
In BEPC, the oscillation information of the beam position of a single bunch in every turn can be tracked by the bunch-by-bunch system, through which the relationships between the transverse damping time and the beam current, chromaticity, octupole current and beam energy were obtained. The radiation damping time acquired in the experiment was 52 ms. The data analysis result of the bunch-by-bunch tracking experiment indicates that the higher the beam current is and the higher the chromaticity is, the higher the damping ratio is, and that the change of the octupole current has little influence on the damping ratio when the beam current is 4.7 mA. The damping ratio decreases with the rising of the beam energy when the beam current is 5 mA.
2006,
18.
Abstract:
A 120 MW pulsed electron gun has been developed for 50 MW China-made klystron. It has a Pierce type dispenser cathode and it scans with a diameter of 85 mm. This paper describes the temperature field distribution in the gun and the gun deformation caused by this distribution by using ANSYS. According to the real complex structure and the energy conversion inside the electron gun, we took the thermal conduction as the main energy conversion form and got the temperature field. The coincidence between the temperature field and the structural deformation is also described in this paper. The beam optics simulated by EGUN with and without considering deformation is discussed, and the valuable results have been obtained. The high power test results and simulation results are analyzed and compared
A 120 MW pulsed electron gun has been developed for 50 MW China-made klystron. It has a Pierce type dispenser cathode and it scans with a diameter of 85 mm. This paper describes the temperature field distribution in the gun and the gun deformation caused by this distribution by using ANSYS. According to the real complex structure and the energy conversion inside the electron gun, we took the thermal conduction as the main energy conversion form and got the temperature field. The coincidence between the temperature field and the structural deformation is also described in this paper. The beam optics simulated by EGUN with and without considering deformation is discussed, and the valuable results have been obtained. The high power test results and simulation results are analyzed and compared
2006,
18.
Abstract:
According to the time-frequency localization properties of wavelet transform, the application methods in pulse signal′s de-noising and singularity detection show good performance in signal processing of high current LIA. A method to extract characteristic parameters from energy on the coefficients of wavelet packet transform of Dragon-Ⅰ’s waveforms is presented. Parameters, which are extracted from the relevant frequency bands and are used as vector, represent jointly temporal position and frequency variation of waveform. Such characteristic vector can be applied to further signal processing and fault diagnosis of high current LIA.
According to the time-frequency localization properties of wavelet transform, the application methods in pulse signal′s de-noising and singularity detection show good performance in signal processing of high current LIA. A method to extract characteristic parameters from energy on the coefficients of wavelet packet transform of Dragon-Ⅰ’s waveforms is presented. Parameters, which are extracted from the relevant frequency bands and are used as vector, represent jointly temporal position and frequency variation of waveform. Such characteristic vector can be applied to further signal processing and fault diagnosis of high current LIA.
2006,
18.
Abstract:
This paper presents a newly implemented wideband(100 MHz) bunch oscillation measurement system, which is in nature different from the narrow-band (<5 MHz) facilities employed before. Basic formalism and implementation details of the system are introduced to illustrate the function of observing coupled bunch instabilities in time and frequency domain. The designed function includes detecting of transverse oscillation, synchrotron phase oscillation, as well as bunch filling pattern. Some diagnostics results of machine instabilities and application of this system are also discussed, which well depict bunch filling mechanism, instability coupling between transverse and longitudinal directions, inherent machine damping time, as well as dominant oscillation modes.
This paper presents a newly implemented wideband(100 MHz) bunch oscillation measurement system, which is in nature different from the narrow-band (<5 MHz) facilities employed before. Basic formalism and implementation details of the system are introduced to illustrate the function of observing coupled bunch instabilities in time and frequency domain. The designed function includes detecting of transverse oscillation, synchrotron phase oscillation, as well as bunch filling pattern. Some diagnostics results of machine instabilities and application of this system are also discussed, which well depict bunch filling mechanism, instability coupling between transverse and longitudinal directions, inherent machine damping time, as well as dominant oscillation modes.
2006,
18.
Abstract:
In order to cure and suppress beam instabilities caused by the high order modes (HOM) in the RF cavity and the resistive wall impedance of the vacuum chamber, a bunch by bunch measuring and transverse feedback system of broad band with two BPM is under development now. It can detect and analyze the coupled-bunch(CB) instabilities in time and frequency domain, bunch filling pattern in injection and injection ratio, and suppress CB instability for advanced machine performance. The design concepts and detailed development of the system are presented in this paper. The high frequency of HLS is 204 MHz, which requires the bandwidth of the feedback system wider than 100 MHz. The primary ideas to choose the broad-band components and the system parameters are also expounded.
In order to cure and suppress beam instabilities caused by the high order modes (HOM) in the RF cavity and the resistive wall impedance of the vacuum chamber, a bunch by bunch measuring and transverse feedback system of broad band with two BPM is under development now. It can detect and analyze the coupled-bunch(CB) instabilities in time and frequency domain, bunch filling pattern in injection and injection ratio, and suppress CB instability for advanced machine performance. The design concepts and detailed development of the system are presented in this paper. The high frequency of HLS is 204 MHz, which requires the bandwidth of the feedback system wider than 100 MHz. The primary ideas to choose the broad-band components and the system parameters are also expounded.
2006,
18.
Abstract:
The high power waveguide valve is a major part of microwave system for BEPCⅡ-Linac. As an ultra-high vacuum RF component with functions of microwave high power transmission and vacuum sealing, it has a complicated structure and is difficult to fabricate. In summer of 2004, 16 sets of high power waveguide valves were developed successfully and installed on BEPCⅡ-Linac. Now the wave-guide valve work well at pulse peak power of 30~50 MW. This paper describes the design, mechanism, RF test and high power operating status of the wave-guide valve.
The high power waveguide valve is a major part of microwave system for BEPCⅡ-Linac. As an ultra-high vacuum RF component with functions of microwave high power transmission and vacuum sealing, it has a complicated structure and is difficult to fabricate. In summer of 2004, 16 sets of high power waveguide valves were developed successfully and installed on BEPCⅡ-Linac. Now the wave-guide valve work well at pulse peak power of 30~50 MW. This paper describes the design, mechanism, RF test and high power operating status of the wave-guide valve.
2006,
18.
Abstract:
The on-line measurement system based on OTR can be used to measure the parameters of the intense electron beam, such as beam energy, divergence and emittance, and it has characteristics of ultra-fast response and high special resolution. With the embedded remote controll system, the time-resolved OTR measurement has been implemented successfully. The computer controll system receives the photoelectric video frequency signal, transmits real time image, and gets the dynamic image. This work removes the difficulties of strong disturbance in the beam measurement of intense LIA.
The on-line measurement system based on OTR can be used to measure the parameters of the intense electron beam, such as beam energy, divergence and emittance, and it has characteristics of ultra-fast response and high special resolution. With the embedded remote controll system, the time-resolved OTR measurement has been implemented successfully. The computer controll system receives the photoelectric video frequency signal, transmits real time image, and gets the dynamic image. This work removes the difficulties of strong disturbance in the beam measurement of intense LIA.
2006,
18.
Abstract:
X-band pulse compression equipment is simulated by the finite element method. The influence on resonance frequency and quality factor of some parameters, such as the length of the cavity, the width of the input iris and the location of the output coupling port, is analyzed. The study shows that the resonance frequency of the equipment can be restricted within the range of prescriptive frequency by means of adjusting the length of cavity. As the aperture width of input iris is narrowed down, SWR decreases, before reaching critical coupling, then increases, and resonance frequency also slightly rises. Quality factor is closely corrective with output leakage, which periodically varies with the distance between short circuit and H-T embranch ment midline. The optimal simulation results for the
X-band pulse compression equipment is simulated by the finite element method. The influence on resonance frequency and quality factor of some parameters, such as the length of the cavity, the width of the input iris and the location of the output coupling port, is analyzed. The study shows that the resonance frequency of the equipment can be restricted within the range of prescriptive frequency by means of adjusting the length of cavity. As the aperture width of input iris is narrowed down, SWR decreases, before reaching critical coupling, then increases, and resonance frequency also slightly rises. Quality factor is closely corrective with output leakage, which periodically varies with the distance between short circuit and H-T embranch ment midline. The optimal simulation results for the
2006,
18.
Abstract:
The optimization design of the electrode was of great influence on the switch in pulsed power. The charge simulation method was used to simulate the electric field, the rotating ellipse method to optimize the electrode’s figure, the Particle Swarm Optimization method to select the best geometrical parameters, and the ANSYS electromagnetic analysis to emulate the electric field of the optimized result. The results indicate that the rotating ellipse method combined with the Parameters Scan method can be applied to the auto-optimization of the ring-shaped switch electrodes, and the electric field of the optimized figure and parameters can meet the requirements of electrical field.
The optimization design of the electrode was of great influence on the switch in pulsed power. The charge simulation method was used to simulate the electric field, the rotating ellipse method to optimize the electrode’s figure, the Particle Swarm Optimization method to select the best geometrical parameters, and the ANSYS electromagnetic analysis to emulate the electric field of the optimized result. The results indicate that the rotating ellipse method combined with the Parameters Scan method can be applied to the auto-optimization of the ring-shaped switch electrodes, and the electric field of the optimized figure and parameters can meet the requirements of electrical field.
2006,
18.
Abstract:
A method of time domain calibration and data processing on pulsed current probe which is based on Rogowski coil is introduced. The result of time domain calibration using pulsed signal is compared with the frequency domain calibration result. A dynamic model of measurement system is established through system identification method according to low frequency distortion of the current probe. This method is also used to correct the distorted output signal of the probe. The validity of established model is verified by experimental data and the measurement system can be corrected into an ideal proportional system by designed compensating digital filter.
A method of time domain calibration and data processing on pulsed current probe which is based on Rogowski coil is introduced. The result of time domain calibration using pulsed signal is compared with the frequency domain calibration result. A dynamic model of measurement system is established through system identification method according to low frequency distortion of the current probe. This method is also used to correct the distorted output signal of the probe. The validity of established model is verified by experimental data and the measurement system can be corrected into an ideal proportional system by designed compensating digital filter.
2006,
18.
Abstract:
The current loss in magnetically insulated transmission line(MITL) on pulsed power installation “S-300” is studied by measuring bremsstrahlung between the electrodes, current and voltage in the load. Three kinds of load were used in experiments and the results show that the characteristics of current loss in MITL notablely depend on the types of load. When the load is wire arrays, the current loss occurs at the moment of wire arrays stagnation and the maximum amplitude is no more than 5% of total current in the load.
The current loss in magnetically insulated transmission line(MITL) on pulsed power installation “S-300” is studied by measuring bremsstrahlung between the electrodes, current and voltage in the load. Three kinds of load were used in experiments and the results show that the characteristics of current loss in MITL notablely depend on the types of load. When the load is wire arrays, the current loss occurs at the moment of wire arrays stagnation and the maximum amplitude is no more than 5% of total current in the load.
2006,
18.
Abstract:
In a lot of single-shot applications and experiments at remote locations where magnetic flux compression generator(MFCG) provides the most practicable power, it is impracticable or inconvenient to use a capacitor bank to be the initial energy source. Godovnina, V.V. et al have used a homogenous permanent magnet as the initial energy source to drive MFCG, but the energy density stored in a single permanent magnet is very low. The possibility of using periodic permanent magnetic ring structure to be the initial energy source of an MFCG was analyzed theoretically and numerically. It was concluded that about 1 kJ initial energy can be provided to an MFCG by the periodic-ring permanent magnetic ring which weights less than 30 kg and the outside radius less than 30 cm. In this paper, an axially
In a lot of single-shot applications and experiments at remote locations where magnetic flux compression generator(MFCG) provides the most practicable power, it is impracticable or inconvenient to use a capacitor bank to be the initial energy source. Godovnina, V.V. et al have used a homogenous permanent magnet as the initial energy source to drive MFCG, but the energy density stored in a single permanent magnet is very low. The possibility of using periodic permanent magnetic ring structure to be the initial energy source of an MFCG was analyzed theoretically and numerically. It was concluded that about 1 kJ initial energy can be provided to an MFCG by the periodic-ring permanent magnetic ring which weights less than 30 kg and the outside radius less than 30 cm. In this paper, an axially
2006,
18.
Abstract:
A planar spark gap switch with three electrodes which is suitable for connecting parallel-plate transmission lines is developed. The shape of positive and negative electrodes of the switch is semicircle, and the triggering electrode is a thin strip. When the planar spark gap switch substitutes for the stereo spark gap with hemispherical electrodes used in the exploding foil initiator, the parameters in the circuit are optimized obviously. The performance of the planar spark gap switch with different gap space was measured. The experimental results show that the inductance of the planar spark gap is less than 15 nH, and that the jitter time of the switch with different gap space is no more than 10 ns for different applied voltages ranges. When the planar spark gap switch is used in the puls
A planar spark gap switch with three electrodes which is suitable for connecting parallel-plate transmission lines is developed. The shape of positive and negative electrodes of the switch is semicircle, and the triggering electrode is a thin strip. When the planar spark gap switch substitutes for the stereo spark gap with hemispherical electrodes used in the exploding foil initiator, the parameters in the circuit are optimized obviously. The performance of the planar spark gap switch with different gap space was measured. The experimental results show that the inductance of the planar spark gap is less than 15 nH, and that the jitter time of the switch with different gap space is no more than 10 ns for different applied voltages ranges. When the planar spark gap switch is used in the puls
