Email alert
RSS2010 Vol. 22, No. 03
Recommend Articles
Display Method:
2010,
22.
Abstract:
Pulse compression and voltage multiplication methods were studied by using solid-state switches for repetitive operation. Circuit schemes of pulse-forming line using inductive energy storage and pulse compression using saturable capacitor were explored experimentally. The experimental results have validated the principle of their operations and have revealed their technical features by the comparison with the traditional methods.
Pulse compression and voltage multiplication methods were studied by using solid-state switches for repetitive operation. Circuit schemes of pulse-forming line using inductive energy storage and pulse compression using saturable capacitor were explored experimentally. The experimental results have validated the principle of their operations and have revealed their technical features by the comparison with the traditional methods.
2010,
22.
Abstract:
In experiments it is found that the wire wound spiral transformer would undergo breakdown during the charging period, sometimes even when the primary circuit just conducts. To explore the reason for breakdown and to improve insulation, a simplified multi-conductor transmission line method is used to deduce the inter-turn voltage distribution, under the assumption that the displacement current can be neglected. The results show that the voltage distribution varies with time, and it is influenced by circuit extrinsic parameters such as circuit mismatch, primary capacitor voltage, etc. With slight circuit mismatch, the transformer is likely to break down at the initial stage of charging. These characters can be utilized to design a better insulated transformer, by making the voltage distribut
In experiments it is found that the wire wound spiral transformer would undergo breakdown during the charging period, sometimes even when the primary circuit just conducts. To explore the reason for breakdown and to improve insulation, a simplified multi-conductor transmission line method is used to deduce the inter-turn voltage distribution, under the assumption that the displacement current can be neglected. The results show that the voltage distribution varies with time, and it is influenced by circuit extrinsic parameters such as circuit mismatch, primary capacitor voltage, etc. With slight circuit mismatch, the transformer is likely to break down at the initial stage of charging. These characters can be utilized to design a better insulated transformer, by making the voltage distribut
2010,
22.
Abstract:
The optimization theory of a transmission line pulse transformer(TLT) has been introduced, and a 4-stage TLT was built and tested based on the theory. Magnetic cores used in this TLT met the optimization requirement of the TLT structure without coupling between stages. Coaxial cables with good flexibility were used, and the secondary line inductance of each stage was 1.83, 3.52 and 5.41 mH respectively, which was up to the preset goal. Through a Blumlein pulsed generator, a pulse with a voltage up to 10 kV, a duration of 150 ns and a rise-time about 20 ns was injected into the TLT. Then at the output terminal of the TLT, a pulse with an amplitude of 40 kV, a duration of 150 ns and a rise-time slightly larger than 20 ns was obtained. The result indicates that the pulse’s basic shape can be
The optimization theory of a transmission line pulse transformer(TLT) has been introduced, and a 4-stage TLT was built and tested based on the theory. Magnetic cores used in this TLT met the optimization requirement of the TLT structure without coupling between stages. Coaxial cables with good flexibility were used, and the secondary line inductance of each stage was 1.83, 3.52 and 5.41 mH respectively, which was up to the preset goal. Through a Blumlein pulsed generator, a pulse with a voltage up to 10 kV, a duration of 150 ns and a rise-time about 20 ns was injected into the TLT. Then at the output terminal of the TLT, a pulse with an amplitude of 40 kV, a duration of 150 ns and a rise-time slightly larger than 20 ns was obtained. The result indicates that the pulse’s basic shape can be
2010,
22.
Abstract:
A novel double-layer cylinder flashboard plasma gun system is put forward. The inner flashboard of the plasma gun is connected to high voltage, with 160 arcing points uniformly distributed on it. Each arcing point consists of a central electrode and a groove filled by TiH2 powder. The powder is bound to the groove with a sodium-silicate binder. TiH2 is chosen for negative hydrogen production, and one can fill the grooves with other materials for other purposes if needed. Each high voltage electrode is connected with the earth electrode through a 100 Ω resistor, and the plasma is produced in the gap between electrodes. Experimental results show that, when the capacitor is 3 kV/20 μF, the plasma gun is triggered by a current whose amplitude is 150 A and pulse width is 1.5 μs, and the dens
A novel double-layer cylinder flashboard plasma gun system is put forward. The inner flashboard of the plasma gun is connected to high voltage, with 160 arcing points uniformly distributed on it. Each arcing point consists of a central electrode and a groove filled by TiH2 powder. The powder is bound to the groove with a sodium-silicate binder. TiH2 is chosen for negative hydrogen production, and one can fill the grooves with other materials for other purposes if needed. Each high voltage electrode is connected with the earth electrode through a 100 Ω resistor, and the plasma is produced in the gap between electrodes. Experimental results show that, when the capacitor is 3 kV/20 μF, the plasma gun is triggered by a current whose amplitude is 150 A and pulse width is 1.5 μs, and the dens
2010,
22.
Abstract:
The design of a 1 MA linear transformer driver(LTD) stage is introduced, whose current risetime is 100 ns. The stage consists of 48 parallel bricks, each of which consists of two capacitors (40 nF/100 kV) and a multi-gap gas switch in series. The 48 switches are triggered by 8 high voltage pulses (100 kV/50 ns) with each pulse triggering 6 switches. According to the simulation results, when charged to 90 kV, the output current of this stage is 1.04 MA, and the current risetime is 84.5 ns (0~100%) and 52 ns (10%~90%). Simulation is based on experimental data. Work conditions of the switches are similar to those in 100 kA-LTD stage which has been tested successfully before. The 1 MA-LTD stage will be filled with transformer oil to ensure safty when charged to high voltage.
The design of a 1 MA linear transformer driver(LTD) stage is introduced, whose current risetime is 100 ns. The stage consists of 48 parallel bricks, each of which consists of two capacitors (40 nF/100 kV) and a multi-gap gas switch in series. The 48 switches are triggered by 8 high voltage pulses (100 kV/50 ns) with each pulse triggering 6 switches. According to the simulation results, when charged to 90 kV, the output current of this stage is 1.04 MA, and the current risetime is 84.5 ns (0~100%) and 52 ns (10%~90%). Simulation is based on experimental data. Work conditions of the switches are similar to those in 100 kA-LTD stage which has been tested successfully before. The 1 MA-LTD stage will be filled with transformer oil to ensure safty when charged to high voltage.
2010,
22.
Abstract:
The novel repetitive frequency impulse voltage generator utilizes both the feature “high repetitive rate and magnetic compression” of magnetic switch and the feature “charging in parallel and discharging in series” of Marx generator. It is possible to generate high voltage impulses with rapid rise time and high repetition rate by replacing the spark gaps in the traditional impulse voltage generator with magnetic switches. A magnetic switch based impulse voltage generator was built and the output impulses with a magnitude of 17 kV, a rise time of 80 ns and a repetition rate of 1 kHz were achieved on a 1 nF capacitive load.
The novel repetitive frequency impulse voltage generator utilizes both the feature “high repetitive rate and magnetic compression” of magnetic switch and the feature “charging in parallel and discharging in series” of Marx generator. It is possible to generate high voltage impulses with rapid rise time and high repetition rate by replacing the spark gaps in the traditional impulse voltage generator with magnetic switches. A magnetic switch based impulse voltage generator was built and the output impulses with a magnitude of 17 kV, a rise time of 80 ns and a repetition rate of 1 kHz were achieved on a 1 nF capacitive load.
2010,
22.
Abstract:
The paper presents Chopping-Peaking(C-P) switch type and Blumlein line type high power bipolar pulse formers, and studies their operating principles. In ideal condition, the output bipolar high voltage pulses with the peak-peak voltage between the peaks of unlike polarity is twice the voltage of the injecting pulse. Two corresponding high power bipolar pulse formers are designed and simulated calculations are carried out through adopting Pspice software. High voltage experiments about two types of high power bipolar pulse formers are operated on the same high power ultra-wideband supply and the results of the experiments are that the C-P switch type bipolar pulse former can export the bipolar pulse with peak voltages of -812.0 kV, 603.2 kV and 720 ps interval of two peaks, at the input pul
The paper presents Chopping-Peaking(C-P) switch type and Blumlein line type high power bipolar pulse formers, and studies their operating principles. In ideal condition, the output bipolar high voltage pulses with the peak-peak voltage between the peaks of unlike polarity is twice the voltage of the injecting pulse. Two corresponding high power bipolar pulse formers are designed and simulated calculations are carried out through adopting Pspice software. High voltage experiments about two types of high power bipolar pulse formers are operated on the same high power ultra-wideband supply and the results of the experiments are that the C-P switch type bipolar pulse former can export the bipolar pulse with peak voltages of -812.0 kV, 603.2 kV and 720 ps interval of two peaks, at the input pul
2010,
22.
Abstract:
A new method to generate high voltage multi-pulse is described. The Blumlein pulse forming line(PFL) and the pulse transmission line are connected to form a closed loop, in which the voltage pulse generated by the PFL will circulate with the loss neglectable. And if the resistance of the load is much higher than that of the transmission line, the MHz repetition multi-pulse cluster will act on the load. Theory analysis and experiments have been done to prove the feasibility of this method. In the experiments, the multi-pulse clusters were generated with a voltage more than 200 kV, a pulse number more than 4, and a pulse interval less than 400 ns, according with the forecast of the theory analysis.
A new method to generate high voltage multi-pulse is described. The Blumlein pulse forming line(PFL) and the pulse transmission line are connected to form a closed loop, in which the voltage pulse generated by the PFL will circulate with the loss neglectable. And if the resistance of the load is much higher than that of the transmission line, the MHz repetition multi-pulse cluster will act on the load. Theory analysis and experiments have been done to prove the feasibility of this method. In the experiments, the multi-pulse clusters were generated with a voltage more than 200 kV, a pulse number more than 4, and a pulse interval less than 400 ns, according with the forecast of the theory analysis.
2010,
22.
Abstract:
An experimental study on repetition nanosecond-pulse breakdown in polytetrafluoroethylene(PTFE) films is presented, the pulse rise-time and pulse-width are 15 ns and 30~40 ns respectively, and the pulse repetition frequency varies from 1 to 1 000 Hz. The parameters affecting breakdown characteristics such as voltage-current waveforms, repetitive pulse stress time and applied pulse number are measured and calculated. The experimental results show that the electric field of repetition nanosecond-pulse breakdown is on the order of MV/cm, and the repetitive pulse stress time decreases with the increasing of the applied electric field and the pulse repetition frequency. The dispersion of the experimental data results from the intrinsic film properties and oil-filling time. In addition, the ther
An experimental study on repetition nanosecond-pulse breakdown in polytetrafluoroethylene(PTFE) films is presented, the pulse rise-time and pulse-width are 15 ns and 30~40 ns respectively, and the pulse repetition frequency varies from 1 to 1 000 Hz. The parameters affecting breakdown characteristics such as voltage-current waveforms, repetitive pulse stress time and applied pulse number are measured and calculated. The experimental results show that the electric field of repetition nanosecond-pulse breakdown is on the order of MV/cm, and the repetitive pulse stress time decreases with the increasing of the applied electric field and the pulse repetition frequency. The dispersion of the experimental data results from the intrinsic film properties and oil-filling time. In addition, the ther
2010,
22.
Abstract:
Multichannel discharge in gas switches is an effective approach for the reduction of switch inductance, channel resistance and electrode erosion, and the increase of switch lifetime and stability. A coaxial field-distortion gas spark switch was designed and its multichannel discharge phenomena under nanosecond voltage pulses were investigated. The relation between the characteristics of multichannel discharge and the rising rate of pulse voltage was studied. Multichannel discharge characteristics of SF6/Ar mixtures under two mixture ratios were compared. Experimental results show that under a certain pressure the average number of channels increases as the rising rate of pulses increases, and the distribution of current tends to be uniform. The number of channels under a higher pressure is
Multichannel discharge in gas switches is an effective approach for the reduction of switch inductance, channel resistance and electrode erosion, and the increase of switch lifetime and stability. A coaxial field-distortion gas spark switch was designed and its multichannel discharge phenomena under nanosecond voltage pulses were investigated. The relation between the characteristics of multichannel discharge and the rising rate of pulse voltage was studied. Multichannel discharge characteristics of SF6/Ar mixtures under two mixture ratios were compared. Experimental results show that under a certain pressure the average number of channels increases as the rising rate of pulses increases, and the distribution of current tends to be uniform. The number of channels under a higher pressure is
2010,
22.
Abstract:
Output performance of multiferroic pulse forming lines(PFLs) were investigated. The multiferroic PFLs were fabricated by utilizing (Ni, Zn) ferrite-BaTiO3 ceramics composites. Square output waveforms with different widths were acquired under the conditions of different magnetic circuit schemes. With “closed” magnetic circuit scheme formed by high permeability materials, the FWHM of the output waveform is 201 ns. Relative permittivity coefficient approaching 2 000 and relative permeability coefficient more than 1.4 are calculated respectively. The impact of multiferroic PFL’s topology on output characteristics is analysed based on the concept of effective permeability. As the parallel plate multiferroic PFL is concerned, effective permeability is determined not only by the permeability o
Output performance of multiferroic pulse forming lines(PFLs) were investigated. The multiferroic PFLs were fabricated by utilizing (Ni, Zn) ferrite-BaTiO3 ceramics composites. Square output waveforms with different widths were acquired under the conditions of different magnetic circuit schemes. With “closed” magnetic circuit scheme formed by high permeability materials, the FWHM of the output waveform is 201 ns. Relative permittivity coefficient approaching 2 000 and relative permeability coefficient more than 1.4 are calculated respectively. The impact of multiferroic PFL’s topology on output characteristics is analysed based on the concept of effective permeability. As the parallel plate multiferroic PFL is concerned, effective permeability is determined not only by the permeability o
2010,
22.
Abstract:
A compact pulsed generator based on ceramic capacitor is designed. Its circuit is theoretically calculated and the effect of the main parameters on the output waveform is analyzed. A circuit model of the generator is established for validation with PSpice software, and the simulation results agree well with the calculated results. The generator can produce an adjustable high voltage pulse with the parameters of output voltage 100~200 kV, pulse width 30~40 ns and rise time less than 10 ns. The generator is a no-liquid pulsed generator with ceramic capacitors as the energy storage components and SF6 as insulated dielectric. It has characteristics of compact construction, small volume and light weight.
A compact pulsed generator based on ceramic capacitor is designed. Its circuit is theoretically calculated and the effect of the main parameters on the output waveform is analyzed. A circuit model of the generator is established for validation with PSpice software, and the simulation results agree well with the calculated results. The generator can produce an adjustable high voltage pulse with the parameters of output voltage 100~200 kV, pulse width 30~40 ns and rise time less than 10 ns. The generator is a no-liquid pulsed generator with ceramic capacitors as the energy storage components and SF6 as insulated dielectric. It has characteristics of compact construction, small volume and light weight.
2010,
22.
Abstract:
The characteristic parameters of a folded film dielectric parallel-plates Blumlein line were analyzed theoretically. The equivalent circuit model was simulated using Pspice software considering the effect of switch inductance and parasitic impedance on the output waveform. Simulating result shows that the increase in switch inductance slows the rise edge and distorts the fall edge of the pulses, introducing reflections as well. The parasitic impedance causes some power loss in the device so that the output pulse amplitude is lower than expected. The electromagnetic field distributions were simulated. The electric field distortion at the rim and bend part of the film electrode must be considered in the insulation design of the folded parallel-plates Blumlein line. Based on the theoretical a
The characteristic parameters of a folded film dielectric parallel-plates Blumlein line were analyzed theoretically. The equivalent circuit model was simulated using Pspice software considering the effect of switch inductance and parasitic impedance on the output waveform. Simulating result shows that the increase in switch inductance slows the rise edge and distorts the fall edge of the pulses, introducing reflections as well. The parasitic impedance causes some power loss in the device so that the output pulse amplitude is lower than expected. The electromagnetic field distributions were simulated. The electric field distortion at the rim and bend part of the film electrode must be considered in the insulation design of the folded parallel-plates Blumlein line. Based on the theoretical a
2010,
22.
Abstract:
A low impedance triplate transmission line, consisting of three parallel plate-electrodes, filled with de-ionized water, was designed for the Z-pinch Primary Test Stand (PTS) prototype. The determination of the triplate line’s parameters by its characteristic impedance cannot use the traditional bi-plate impedance formula, since the coupling-capacitance between the inner plate edge and water tank must be considered. The rated impedance of the triplate line was 4.00 Ω, and the designed impedance reached 4.08 Ω by the dimension of the triplate line without water tank. When considering capacitance coupling between triplate edge and water tank, the triplate line’s impedance was 3.77 Ω by precise FEM calculation. While, the actual operation impedance was 3.83 Ω according to measured volt
A low impedance triplate transmission line, consisting of three parallel plate-electrodes, filled with de-ionized water, was designed for the Z-pinch Primary Test Stand (PTS) prototype. The determination of the triplate line’s parameters by its characteristic impedance cannot use the traditional bi-plate impedance formula, since the coupling-capacitance between the inner plate edge and water tank must be considered. The rated impedance of the triplate line was 4.00 Ω, and the designed impedance reached 4.08 Ω by the dimension of the triplate line without water tank. When considering capacitance coupling between triplate edge and water tank, the triplate line’s impedance was 3.77 Ω by precise FEM calculation. While, the actual operation impedance was 3.83 Ω according to measured volt
2010,
22.
Abstract:
A high-power photoconductive semiconductor switch(PCSS) has been fabricated by semi-insulating silicon carbide crystal. The width of the output voltage pulse was about 40 ns and the rise-time was 9.6 ns, when a KrF excimer laser was adopted as the excitation source. Two different steps were observed in the rising edge. With the input voltage rising from 1 kV to 11 kV, the on-state resistance remained about 12 Ω. The peak current through the PCSS came to be 159 A with the 11 kV input voltage, while the peak power reached 1.4 MW. No carrier saturation has been observed in the experiment.
A high-power photoconductive semiconductor switch(PCSS) has been fabricated by semi-insulating silicon carbide crystal. The width of the output voltage pulse was about 40 ns and the rise-time was 9.6 ns, when a KrF excimer laser was adopted as the excitation source. Two different steps were observed in the rising edge. With the input voltage rising from 1 kV to 11 kV, the on-state resistance remained about 12 Ω. The peak current through the PCSS came to be 159 A with the 11 kV input voltage, while the peak power reached 1.4 MW. No carrier saturation has been observed in the experiment.
2010,
22.
Abstract:
This paper summarized the design method of a 1.2 MV pulse transformer, which adopted the helix-involute winding to enlarge the isolation distance between the winding and the magnetic core. The numerical simulation of ANSYS showed that the maximum electric field was less than 18 kV/mm in this transformer. The local-discharge phenomena of the winding to the insulator were solved through experimental research. The derived pulse transformer could meet the following design specifications:1.2 MV output voltage, 100 Hz repetition frequency and 1 min single runtime.
This paper summarized the design method of a 1.2 MV pulse transformer, which adopted the helix-involute winding to enlarge the isolation distance between the winding and the magnetic core. The numerical simulation of ANSYS showed that the maximum electric field was less than 18 kV/mm in this transformer. The local-discharge phenomena of the winding to the insulator were solved through experimental research. The derived pulse transformer could meet the following design specifications:1.2 MV output voltage, 100 Hz repetition frequency and 1 min single runtime.
2010,
22.
Abstract:
To generate 200~500 kV, 1~10 kA picosecond(ps) pulses with 100~500 ps duration, a theoretical model of ps pulse generator has been suggested. The extreme value method has been proposed for the choice of the operation state with the highest gain coefficients, and the derived ps pulse forming line(PFL) achieved normalized gain coefficients of output voltage, energy and power, respectively, of 90%, 70% and 85%. Finally, the impedance ratio of ns PFL to ps PFL was optimized to shorten the loading time of the 500 kV high voltage on the ps-PFL. At the ratio of impedances 1.63, the gains of the output voltage, energy and power reach 94%, 72% and 89% at the time of 4 ps-PFL pulse-widthes, and 99%, 53% and 97% at the 6 ps-PFL pulse widthes, respectively.
To generate 200~500 kV, 1~10 kA picosecond(ps) pulses with 100~500 ps duration, a theoretical model of ps pulse generator has been suggested. The extreme value method has been proposed for the choice of the operation state with the highest gain coefficients, and the derived ps pulse forming line(PFL) achieved normalized gain coefficients of output voltage, energy and power, respectively, of 90%, 70% and 85%. Finally, the impedance ratio of ns PFL to ps PFL was optimized to shorten the loading time of the 500 kV high voltage on the ps-PFL. At the ratio of impedances 1.63, the gains of the output voltage, energy and power reach 94%, 72% and 89% at the time of 4 ps-PFL pulse-widthes, and 99%, 53% and 97% at the 6 ps-PFL pulse widthes, respectively.
2010,
22.
Abstract:
A PSpice model of electromagnetic launch(EML) system was built up for the distributed energy store(DES) powered railgun. The pulsed power supply adopts the capacitor-based pulse forming network(PFN), which is widely-used in railgun systems. The railgun model takes consideration of many nonlinear factors caused by the movement of armature. During simulation, various parameters were applied to calculate the efficiency of the EML system, including capacitance and initial voltage of capacitor bank, inductance of pulse forming inductor, intervals of crowbar switches, parameters of pulse forming units and so on. Through comparison and analysis, several methods to raise the efficiency of the EML system were acquired. The simulation results show that, for given amature mass and accelerating distan
A PSpice model of electromagnetic launch(EML) system was built up for the distributed energy store(DES) powered railgun. The pulsed power supply adopts the capacitor-based pulse forming network(PFN), which is widely-used in railgun systems. The railgun model takes consideration of many nonlinear factors caused by the movement of armature. During simulation, various parameters were applied to calculate the efficiency of the EML system, including capacitance and initial voltage of capacitor bank, inductance of pulse forming inductor, intervals of crowbar switches, parameters of pulse forming units and so on. Through comparison and analysis, several methods to raise the efficiency of the EML system were acquired. The simulation results show that, for given amature mass and accelerating distan
2010,
22.
Abstract:
Surface treatment of polyethylene terephthalate(PET) films for improving the hydrophilicity using dielectric barrier discharge(DBD) excited by unipolar nanosecond pulses is presented. Homogeneous and filamentary discharges are obtained under certain experimental conditions and then used to modify the surface of PET films. The properties of PET films before and after treatment are characterized with water contact angle measurement, atomic force microscope and X-ray photoelectron spectroscope. The experimental results show that static water contact angles decrease evidently after DBD plasma treatment and the observed contact angle changes from 78° for the untreated samples to 25° after treatment. However, the decrease of contact angles is not continuous and it will reach a saturation state
Surface treatment of polyethylene terephthalate(PET) films for improving the hydrophilicity using dielectric barrier discharge(DBD) excited by unipolar nanosecond pulses is presented. Homogeneous and filamentary discharges are obtained under certain experimental conditions and then used to modify the surface of PET films. The properties of PET films before and after treatment are characterized with water contact angle measurement, atomic force microscope and X-ray photoelectron spectroscope. The experimental results show that static water contact angles decrease evidently after DBD plasma treatment and the observed contact angle changes from 78° for the untreated samples to 25° after treatment. However, the decrease of contact angles is not continuous and it will reach a saturation state
2010,
22.
Abstract:
A triggered and self-closing rod-plane corona stabilized spark switch is reported. Its rod electrode diameter, main gap and trigger gap are 2 mm,10 mm and 5 mm, respectively. The degree of field divergence is known to be larger than 7 by simulating electrostatic field of the switch. Experimental results show that, the corona onset voltage and breakdown voltage are 6.8 kV and 19.3 kV, respectively, based on which the corona stabilized factor is caculated to be 0.55. That is, the switch has good corona stabilized performance.
A triggered and self-closing rod-plane corona stabilized spark switch is reported. Its rod electrode diameter, main gap and trigger gap are 2 mm,10 mm and 5 mm, respectively. The degree of field divergence is known to be larger than 7 by simulating electrostatic field of the switch. Experimental results show that, the corona onset voltage and breakdown voltage are 6.8 kV and 19.3 kV, respectively, based on which the corona stabilized factor is caculated to be 0.55. That is, the switch has good corona stabilized performance.
2010,
22.
Abstract:
In the linear induction accelerator, the power supply of rectifier loop is constant current sources. This article studied two kinds of voltage controlled constant current sources(VCCS) with operational amplifiers based on floating load and grounded load. From theory, simulation and experiment, their differences in configuration, operation character and output were comparatively studied. The results point out that the two kinds of VCCS can both produce the output in anticipation, and the floating-load VCCS can provide a more steady current output, fulfilling the future engineering requirements.
In the linear induction accelerator, the power supply of rectifier loop is constant current sources. This article studied two kinds of voltage controlled constant current sources(VCCS) with operational amplifiers based on floating load and grounded load. From theory, simulation and experiment, their differences in configuration, operation character and output were comparatively studied. The results point out that the two kinds of VCCS can both produce the output in anticipation, and the floating-load VCCS can provide a more steady current output, fulfilling the future engineering requirements.
2010,
22.
Abstract:
As an important part of photoconductive semiconductor switch the laser triggering system was studied. A photoconductive semiconductor switch with a gap of 12 mm was fabricated from semi-insulating GaAs. Illuminated by laser pulses with different incident optical energies at a wavelength of 1 064 nm, photoconductivity tests of the photoconductive semiconductor switch were performed at different bias voltages. The laser spots with different profiles were used to trigger the photoconductive semiconductor switch, and the results of the photoconductivity tests were compared and discussed, which show that spot location has opposite influence on photocurrent for intrinsic and extrinsic photoconductivity.
As an important part of photoconductive semiconductor switch the laser triggering system was studied. A photoconductive semiconductor switch with a gap of 12 mm was fabricated from semi-insulating GaAs. Illuminated by laser pulses with different incident optical energies at a wavelength of 1 064 nm, photoconductivity tests of the photoconductive semiconductor switch were performed at different bias voltages. The laser spots with different profiles were used to trigger the photoconductive semiconductor switch, and the results of the photoconductivity tests were compared and discussed, which show that spot location has opposite influence on photocurrent for intrinsic and extrinsic photoconductivity.
2010,
22.
Abstract:
A new design method of pulsed power generatior based on semiconductor switches has been studied. The generator using metal-oxide-semiconductor field-effect transistors(MOSFETs) can work in high repetition rate, and can also reduce the circuit loss effectively due to the unique circuit structure. The crux of the experiment is how to synchronize all the drive signals of the semiconductor switches. The measure that regulating each drive signal was taken to compensate the influence caused by the difference of each device. Meanwhile special efforts were made on the issues of isolation， such as the optical isolation for the switching signals and the isolated DC-DC converters for power supply, which are important not only for operation synchronization but also for device protection. The Marx gen
A new design method of pulsed power generatior based on semiconductor switches has been studied. The generator using metal-oxide-semiconductor field-effect transistors(MOSFETs) can work in high repetition rate, and can also reduce the circuit loss effectively due to the unique circuit structure. The crux of the experiment is how to synchronize all the drive signals of the semiconductor switches. The measure that regulating each drive signal was taken to compensate the influence caused by the difference of each device. Meanwhile special efforts were made on the issues of isolation， such as the optical isolation for the switching signals and the isolated DC-DC converters for power supply, which are important not only for operation synchronization but also for device protection. The Marx gen
2010,
22.
Abstract:
The diode insulator applied in the Tesla-type pulsed power generator has been simulated. It is found that the field-enhancement regions are generally the breakdown regions. The reasons responsible for breakdown are explored from the aspects of electric-field distribution, angle distribution of electrical lines relative to insulator surfaces, and the imperfections in the insulator, etc. It is believed that the imperfections are the main factor responsible for breakdown, and the local field enhancement and improper structure design are factors partly leading to breakdown. The key structures on the coaxial line influencing the electric field distribution of insulator interfaces are optimized. Then the optimum ranges for the radii of the anode chamfer and the cathode shield are summarized.
The diode insulator applied in the Tesla-type pulsed power generator has been simulated. It is found that the field-enhancement regions are generally the breakdown regions. The reasons responsible for breakdown are explored from the aspects of electric-field distribution, angle distribution of electrical lines relative to insulator surfaces, and the imperfections in the insulator, etc. It is believed that the imperfections are the main factor responsible for breakdown, and the local field enhancement and improper structure design are factors partly leading to breakdown. The key structures on the coaxial line influencing the electric field distribution of insulator interfaces are optimized. Then the optimum ranges for the radii of the anode chamfer and the cathode shield are summarized.
2010,
22.
Abstract:
A high-power photoconductive semiconductor switch(PCSS) has been fabricated by semi-insulating silicon carbide crystal. The width of the output voltage pulse was about 40 ns and the rise-time was 9.6 ns, when a KrF excimer laser was adopted as the excitation source. Two different steps were observed in the rising edge. With the input voltage rising from 1 kV to 11 kV, the on-state resistance remained about 12 Ω. The peak current through the PCSS came to be 159 A with the 11 kV input voltage, while the peak power reached 1.4 MW. No carrier saturation has been observed in the experiment.
A high-power photoconductive semiconductor switch(PCSS) has been fabricated by semi-insulating silicon carbide crystal. The width of the output voltage pulse was about 40 ns and the rise-time was 9.6 ns, when a KrF excimer laser was adopted as the excitation source. Two different steps were observed in the rising edge. With the input voltage rising from 1 kV to 11 kV, the on-state resistance remained about 12 Ω. The peak current through the PCSS came to be 159 A with the 11 kV input voltage, while the peak power reached 1.4 MW. No carrier saturation has been observed in the experiment.
2010,
22.
Abstract:
A trigatron switch was designed for a gigawatt nanosecond pulse source of Tesla type. For achieving subnanosecond jitter, experimental research was conducted under different voltage polarity combination, trigger voltage, trigger gap, trigger pin diameter and trigger pulse width. The results show that voltage polarity combination, trigger voltage and trigger gap have significant influence on triggering characteristics. The influence of trigger pin diameter and trigger pulse width is relative small. The trigatron switch was optimized according to the experimental results and a jitter of 0.1 ns was achieved.
A trigatron switch was designed for a gigawatt nanosecond pulse source of Tesla type. For achieving subnanosecond jitter, experimental research was conducted under different voltage polarity combination, trigger voltage, trigger gap, trigger pin diameter and trigger pulse width. The results show that voltage polarity combination, trigger voltage and trigger gap have significant influence on triggering characteristics. The influence of trigger pin diameter and trigger pulse width is relative small. The trigatron switch was optimized according to the experimental results and a jitter of 0.1 ns was achieved.
2010,
22.
Abstract:
The behaviors of three kinds of self-breakdown water switches for Qiangguang-Ⅰaccelerator were studied. They have different configurations including sphere-plane structure, local field-enhanced sphere-plane structure and annulus-plane structure. By computer simulation,the electric field parameters were determined. The breakdown characteristics of the switches were tested in Qiangguang-Ⅰfacility. Experimental results of three different kinds of switches show that the annulus-plane structured ha= s the switch stablest breakdown performance. The time jitter of the annulus-plane switch for 15 shots is only 30 ns, comparing the 60 ns and 140 ns of the local field-enhanced sphere-plane structure and the sphere-plane structure respectively.In addition to the standard electrical diagnostics, opt
The behaviors of three kinds of self-breakdown water switches for Qiangguang-Ⅰaccelerator were studied. They have different configurations including sphere-plane structure, local field-enhanced sphere-plane structure and annulus-plane structure. By computer simulation,the electric field parameters were determined. The breakdown characteristics of the switches were tested in Qiangguang-Ⅰfacility. Experimental results of three different kinds of switches show that the annulus-plane structured ha= s the switch stablest breakdown performance. The time jitter of the annulus-plane switch for 15 shots is only 30 ns, comparing the 60 ns and 140 ns of the local field-enhanced sphere-plane structure and the sphere-plane structure respectively.In addition to the standard electrical diagnostics, opt
2010,
22.
Abstract:
This paper presents the results of an experimental comparison of carbon velvet cathodes and a common polymer velvet cathode. The comparative results show that the initiation of the carbon velvet cathodes is slightly slower, and it is possible that the output microwave power of the carbon velvet cathodes is higher than that of the common polymer velvet cathode under the same diode voltage. However, the output microwave power and pulse width of the carbon velvet cathodes reduce obviously when part of the fibers fall from the cathode. The tips of the polymer velvet fibers are expanded and bent because of the erosion in operation, which shortens the lifetime of the polymer velvet cathode. While, this does not happen to the tips of the carbon velvet fibers, which shows that the lifetime of the
This paper presents the results of an experimental comparison of carbon velvet cathodes and a common polymer velvet cathode. The comparative results show that the initiation of the carbon velvet cathodes is slightly slower, and it is possible that the output microwave power of the carbon velvet cathodes is higher than that of the common polymer velvet cathode under the same diode voltage. However, the output microwave power and pulse width of the carbon velvet cathodes reduce obviously when part of the fibers fall from the cathode. The tips of the polymer velvet fibers are expanded and bent because of the erosion in operation, which shortens the lifetime of the polymer velvet cathode. While, this does not happen to the tips of the carbon velvet fibers, which shows that the lifetime of the
2010,
22.
Abstract:
A wide flat-topped low transverse error field solenoid magnet design for linear induction accelerator is presented. The design features non-uniform winding to reduce field fluctuation due to the magnets’ gap, and homogenizer rings within the solenoid to greatly reduce the effects of winding errors. Numerical modeling of several designs for 12 MeV linear induction accelerator(LIA) in China Academy of Engineering Physics has demonstrated that by using these two techniques the magnetic field fluctuations in the accelerator gap can be reduced by 70% and the transverse error field can be reduced by 96.5%.
A wide flat-topped low transverse error field solenoid magnet design for linear induction accelerator is presented. The design features non-uniform winding to reduce field fluctuation due to the magnets’ gap, and homogenizer rings within the solenoid to greatly reduce the effects of winding errors. Numerical modeling of several designs for 12 MeV linear induction accelerator(LIA) in China Academy of Engineering Physics has demonstrated that by using these two techniques the magnetic field fluctuations in the accelerator gap can be reduced by 70% and the transverse error field can be reduced by 96.5%.
2010,
22.
Abstract:
Outgassing characteristics of a polymer velvet cathode under single shot and repetition rate (rep-rate) operation were experimentally investigated on a pulser, Torch-02, which has an about 300 kV, adout 6 ns and 1 to 300 Hz rep-rate output. For a 10 L vacuum diode-velvet cathode system with an emission area of 28 cm2, an A-K gap of 50 mm and an effective pumping speed of 62 L/s, the pulse desorption profiles with different emitting current densities were obtained. According to the pressure histories, the dependence of equilibrium pressure on pulse rep-rate was presented in the condition of about 5×10-3 Pa base pressure and about 6 J single pulse energy. The diode pressure for burst mode test increased almost linearly with pulse rep-rate from 10 to 100 Hz, and increas
Outgassing characteristics of a polymer velvet cathode under single shot and repetition rate (rep-rate) operation were experimentally investigated on a pulser, Torch-02, which has an about 300 kV, adout 6 ns and 1 to 300 Hz rep-rate output. For a 10 L vacuum diode-velvet cathode system with an emission area of 28 cm2, an A-K gap of 50 mm and an effective pumping speed of 62 L/s, the pulse desorption profiles with different emitting current densities were obtained. According to the pressure histories, the dependence of equilibrium pressure on pulse rep-rate was presented in the condition of about 5×10-3 Pa base pressure and about 6 J single pulse energy. The diode pressure for burst mode test increased almost linearly with pulse rep-rate from 10 to 100 Hz, and increas
2010,
22.
Abstract:
The mechanical axis alignment of Dragon-Ⅰ and -Ⅱ linear induction accelerators(LIAs) requires the error of linearity and level no more than 0.2 mm and the error of angle no more than 2". This paper analyzes the error limit of the major specifications that influence the LIAs’ alignment. The total station, level, theodolite and laser tracker are selected for measurement. An alignment control network including large hexagonal network and small quadrilateral network covering the whole LIA area has been built. Components for precise mechanical adjustment and alignment are designed, and the alignment process and technique of the LIA system are presented. This method has been verified in “Dragon-Ⅰ” LIA.
The mechanical axis alignment of Dragon-Ⅰ and -Ⅱ linear induction accelerators(LIAs) requires the error of linearity and level no more than 0.2 mm and the error of angle no more than 2". This paper analyzes the error limit of the major specifications that influence the LIAs’ alignment. The total station, level, theodolite and laser tracker are selected for measurement. An alignment control network including large hexagonal network and small quadrilateral network covering the whole LIA area has been built. Components for precise mechanical adjustment and alignment are designed, and the alignment process and technique of the LIA system are presented. This method has been verified in “Dragon-Ⅰ” LIA.
2010,
22.
Abstract:
A modified 2 MeV injector was used to study the photocathode for linear induction accelerators, which adopted a frequency-quadrupled Nd:YAG laser (266 nm) and a quartz window. Its trigger system was improved to realize output synchronization between the pulsed power system and the laser. A scandate cathode was investigated and the maximal cathode temperature was about 740 ℃ in the experiments. Photoemission and plasma emission caused by laser were observed. The maximal laser power density was about 1.3 MW/cm2, the maximal emission current density was about 16 A/cm2, and the quantum efficiency of photoemission was about 0.05‰.
A modified 2 MeV injector was used to study the photocathode for linear induction accelerators, which adopted a frequency-quadrupled Nd:YAG laser (266 nm) and a quartz window. Its trigger system was improved to realize output synchronization between the pulsed power system and the laser. A scandate cathode was investigated and the maximal cathode temperature was about 740 ℃ in the experiments. Photoemission and plasma emission caused by laser were observed. The maximal laser power density was about 1.3 MW/cm2, the maximal emission current density was about 16 A/cm2, and the quantum efficiency of photoemission was about 0.05‰.
2010,
22.
Abstract:
The wide-gap klystron and triaxial klystron are the recent developments of the conventional relativistic klystron amplifier, which can effectively improve the output power and efficiency especially at high frequency. The wide-gap triaxial klystron takes advantages of the two kinds of klystrons mentioned above. 2D particle-in-cell simulation on the electron beam transportation of the C-band wide-gap klystron is presented. In order to obtain stable beam transportation, both the radially asymmetrical cavity structure and cautious position choice of the grounding rod located before the input cavity are necessary. Under a diode voltage of 440 kV and an input power of 200 MW at 5.0 GHz, a maximum fundamental integral modulation current of 11.8 kA is obtained with the modulation depth of 88% and
The wide-gap klystron and triaxial klystron are the recent developments of the conventional relativistic klystron amplifier, which can effectively improve the output power and efficiency especially at high frequency. The wide-gap triaxial klystron takes advantages of the two kinds of klystrons mentioned above. 2D particle-in-cell simulation on the electron beam transportation of the C-band wide-gap klystron is presented. In order to obtain stable beam transportation, both the radially asymmetrical cavity structure and cautious position choice of the grounding rod located before the input cavity are necessary. Under a diode voltage of 440 kV and an input power of 200 MW at 5.0 GHz, a maximum fundamental integral modulation current of 11.8 kA is obtained with the modulation depth of 88% and
2010,
22.
Abstract:
A compact L-band relativistic backward wave oscillator(RBWO) is investigated with simulation and experimental method. In simulation, the L-band coaxial RBWO, driven by a 700 kV, 10 kA electron beam, comes to a nonlinear steady state in 20 ns. High-power microwave(HPM) is generated with an average power of 2.23 GW, a frequency of 1.60 GHz, and power conversion efficiency of 31.8%. In the primary experiment, the measured microwave frequency is 1.61 GHz, with a peak power level of above 1.05 GW, when the diode voltage is 703 kV and the current is 10.6 kA. The pulse duration (full-width at half-maximum) of the radiated microwave is 38 ns.
A compact L-band relativistic backward wave oscillator(RBWO) is investigated with simulation and experimental method. In simulation, the L-band coaxial RBWO, driven by a 700 kV, 10 kA electron beam, comes to a nonlinear steady state in 20 ns. High-power microwave(HPM) is generated with an average power of 2.23 GW, a frequency of 1.60 GHz, and power conversion efficiency of 31.8%. In the primary experiment, the measured microwave frequency is 1.61 GHz, with a peak power level of above 1.05 GW, when the diode voltage is 703 kV and the current is 10.6 kA. The pulse duration (full-width at half-maximum) of the radiated microwave is 38 ns.
2010,
22.
Abstract:
This paper conducted the simulation study in 3 dimensions. The cold-cavity analysis was performed for input, idler and output cavities by high frequency field software. The whole L-band RKA tube was modeled by three dimensional particle-in-cell method, and special attention was put onto the influence of the input and output coupling structures. The optimized parameters in the simulation are as follows: the electron energy is 500 keV, the current is 5 kA, the working frequency is 1.3 GHz, the mean output power is 600 MW and the efficiency is about 25%.
This paper conducted the simulation study in 3 dimensions. The cold-cavity analysis was performed for input, idler and output cavities by high frequency field software. The whole L-band RKA tube was modeled by three dimensional particle-in-cell method, and special attention was put onto the influence of the input and output coupling structures. The optimized parameters in the simulation are as follows: the electron energy is 500 keV, the current is 5 kA, the working frequency is 1.3 GHz, the mean output power is 600 MW and the efficiency is about 25%.
2010,
22.
Abstract:
A new coaxial slow-wave oscillator with low impedance was designed. Its diode is seperated from the beam-wave interaction section by the metal mesh in the anode. In order to increase its efficiency, the beam-wave interaction section adopts the double slow-wave structure. The oscillator was optimized by 2D fully electromagnetic particle-in-cell(PIC) code. The optimal model gains the averaged output power in a period of 23 GW and a power conversion efficiency of 23% in L band when the input power is 100 GW and the input current is 95.4 kA. The oscillator is compact and lightweight, requiring no external magnetic field. In addition, the temperature rising of the metal mesh in the anode was simply estimated.
A new coaxial slow-wave oscillator with low impedance was designed. Its diode is seperated from the beam-wave interaction section by the metal mesh in the anode. In order to increase its efficiency, the beam-wave interaction section adopts the double slow-wave structure. The oscillator was optimized by 2D fully electromagnetic particle-in-cell(PIC) code. The optimal model gains the averaged output power in a period of 23 GW and a power conversion efficiency of 23% in L band when the input power is 100 GW and the input current is 95.4 kA. The oscillator is compact and lightweight, requiring no external magnetic field. In addition, the temperature rising of the metal mesh in the anode was simply estimated.
2010,
22.
Abstract:
The statistical nature(probability density function) of the induced voltages at key points within the wave-chaotic scattering cavity was discussed. The applications of random coupling model(RCM) in the high power microwave(HPM) effects and electromagnetic compatibility were introduced. The practicability of RCM-based calculation has been validated by measuring the magnitudes of induced voltages at key points within the computer cavity. It shows that the calculated and experimental results are basically the same, offering a new method for electromagnetic compatibility and HPM effects research.
The statistical nature(probability density function) of the induced voltages at key points within the wave-chaotic scattering cavity was discussed. The applications of random coupling model(RCM) in the high power microwave(HPM) effects and electromagnetic compatibility were introduced. The practicability of RCM-based calculation has been validated by measuring the magnitudes of induced voltages at key points within the computer cavity. It shows that the calculated and experimental results are basically the same, offering a new method for electromagnetic compatibility and HPM effects research.
2010,
22.
Abstract:
Superradiance relativistic backward wave oscillator(SR-RBWO) with high power conversion efficiency is studied by simulation. Coaxial structure is used in the beam-wave interaction region. The outer conductor is a corrugated waveguide and the inner conductor is a smooth circular waveguide. Microwaves will be coupled to the circular waveguide and output from there. By increasing the period number and adjusting the corrugation depth near the collection end, the power conversion efficiency is improved furtherly. For an electron beam of 360 kV and 9.15 kA, with an applied magnetic field of 2.7 T, SR microwave pulse with 18 GW instantaneous power and 400 ps duration is obtained at a center frequency of 8.1 GHz by simulation, the power conversion efficiency reaches 275%.
Superradiance relativistic backward wave oscillator(SR-RBWO) with high power conversion efficiency is studied by simulation. Coaxial structure is used in the beam-wave interaction region. The outer conductor is a corrugated waveguide and the inner conductor is a smooth circular waveguide. Microwaves will be coupled to the circular waveguide and output from there. By increasing the period number and adjusting the corrugation depth near the collection end, the power conversion efficiency is improved furtherly. For an electron beam of 360 kV and 9.15 kA, with an applied magnetic field of 2.7 T, SR microwave pulse with 18 GW instantaneous power and 400 ps duration is obtained at a center frequency of 8.1 GHz by simulation, the power conversion efficiency reaches 275%.
2010,
22.
Abstract:
A C-band relativistic traveling-wave-structure amplifier is designed from dispersion relation of disk-loaded slow-wave structure. In order to avoid self-excitation of the amplifier, some methods are employed in the tube design as follows: coaxial extraction to suppress reflection, sever and absorber to reduce substantially positive feedback, tapering output to reduce retrograde electrons. On the basis of cold cavity characteristic research, quantitative analysis of beam-wave interaction is performed using 2D PIC simulation code. The highest output power, the gain and efficiency is about 890 MW, 35.6 dB and 32% respectively for a 5.64 GHz, 250 kW input.
A C-band relativistic traveling-wave-structure amplifier is designed from dispersion relation of disk-loaded slow-wave structure. In order to avoid self-excitation of the amplifier, some methods are employed in the tube design as follows: coaxial extraction to suppress reflection, sever and absorber to reduce substantially positive feedback, tapering output to reduce retrograde electrons. On the basis of cold cavity characteristic research, quantitative analysis of beam-wave interaction is performed using 2D PIC simulation code. The highest output power, the gain and efficiency is about 890 MW, 35.6 dB and 32% respectively for a 5.64 GHz, 250 kW input.
2010,
22.
Abstract:
An X-band multimode conical horn has been designed with three sections of varied flare angles. The results obtained by experiment measurements are in good agreement with the simulation results. E and H patterns of the conical horn are well equal in the 10 dB regime. The simulation results show that the 10 dB widths of E and H patterns are about 40°. The high power microwave(HPM) experiment results show that the 10 dB width of E pattern is 40°, and the 10 dB width of H pattern is 43°.The conical horn’s power capacity reaches 3 GW in the simulation. In HPM experiment, when the power reaches 1.3 GW,no breakdown phenomena appear.
An X-band multimode conical horn has been designed with three sections of varied flare angles. The results obtained by experiment measurements are in good agreement with the simulation results. E and H patterns of the conical horn are well equal in the 10 dB regime. The simulation results show that the 10 dB widths of E and H patterns are about 40°. The high power microwave(HPM) experiment results show that the 10 dB width of E pattern is 40°, and the 10 dB width of H pattern is 43°.The conical horn’s power capacity reaches 3 GW in the simulation. In HPM experiment, when the power reaches 1.3 GW,no breakdown phenomena appear.
2010,
22.
Abstract:
A compact L-band relativistic backward wave oscillator(RBWO) is investigated with simulation and experimental method. In simulation, the L-band coaxial RBWO, driven by a 700 kV, 10 kA electron beam, comes to a nonlinear steady state in 20 ns. High-power microwave(HPM) is generated with an average power of 2.23 GW, a frequency of 1.60 GHz, and power conversion efficiency of 31.8%. In the primary experiment, the measured microwave frequency is 1.61 GHz, with a peak power level of above 1.05 GW, when the diode voltage is 703 kV and the current is 10.6 kA. The pulse duration (full-width at half-maximum) of the radiated microwave is 38 ns.
A compact L-band relativistic backward wave oscillator(RBWO) is investigated with simulation and experimental method. In simulation, the L-band coaxial RBWO, driven by a 700 kV, 10 kA electron beam, comes to a nonlinear steady state in 20 ns. High-power microwave(HPM) is generated with an average power of 2.23 GW, a frequency of 1.60 GHz, and power conversion efficiency of 31.8%. In the primary experiment, the measured microwave frequency is 1.61 GHz, with a peak power level of above 1.05 GW, when the diode voltage is 703 kV and the current is 10.6 kA. The pulse duration (full-width at half-maximum) of the radiated microwave is 38 ns.
2010,
22.
Abstract:
A new layout of time resolved beam energy spectrum measurement is proposed for Dragon-Ⅰ by a new method named RBS(rotating beams in solenoids). The basic theory of RBS and the new layout are presented and the measuring error is also discussed. The derived time resolved beam energy spectrum is discrete and is determined by measuring the beam’s rotating angle and expanding width through a group of solenoids at the export of Dragon-Ⅰ.
A new layout of time resolved beam energy spectrum measurement is proposed for Dragon-Ⅰ by a new method named RBS(rotating beams in solenoids). The basic theory of RBS and the new layout are presented and the measuring error is also discussed. The derived time resolved beam energy spectrum is discrete and is determined by measuring the beam’s rotating angle and expanding width through a group of solenoids at the export of Dragon-Ⅰ.
2010,
22.
Abstract:
The Compton detector, with fast time response, linear range over many orders of magnitude and low sensitivity to X-ray fluxes, can be used to measure the dose of time resolved X-ray, whose sensitivity is decided by the materials and dimensions of its collector, dielectric and metal case. Since the detector dimension is energy dependent, there will be an optimal dimension for a detector to measure bremsstrahlung X-ray dose. Monte-Carlo method was used to design a Compton detector which will be used to measure the bremsstrahlung X-ray dose produced by the Dragon-Ⅰ accelerator. The bremsstrahlung spectrum of Dragon-Ⅰ was computed by MCNP program, as well as the Compton electron number as a function of plexiglass thickness, aluminum case thickness and plumbum collector thickness. According t
The Compton detector, with fast time response, linear range over many orders of magnitude and low sensitivity to X-ray fluxes, can be used to measure the dose of time resolved X-ray, whose sensitivity is decided by the materials and dimensions of its collector, dielectric and metal case. Since the detector dimension is energy dependent, there will be an optimal dimension for a detector to measure bremsstrahlung X-ray dose. Monte-Carlo method was used to design a Compton detector which will be used to measure the bremsstrahlung X-ray dose produced by the Dragon-Ⅰ accelerator. The bremsstrahlung spectrum of Dragon-Ⅰ was computed by MCNP program, as well as the Compton electron number as a function of plexiglass thickness, aluminum case thickness and plumbum collector thickness. According t
2010,
22.
Abstract:
B/S architecture is utilized in the database system of “Dragon-Ⅰ”. The dynamic web software is designed with the technology of ASP.NET, and the web software are divided into three main tiers: user interface tier, business logic tier and access tier. The data of accelerator status and the data generated in experiment processes are managed with SQL Server DBMS, and the database is accessed based on the technology of ADO.NET. The status of facility, control parameters and testing waves are queried by the experiment number and experiment time. The demand of storage, management, browse, query and offline analysis are implemented entirely in this database system based on B/S architecture.
B/S architecture is utilized in the database system of “Dragon-Ⅰ”. The dynamic web software is designed with the technology of ASP.NET, and the web software are divided into three main tiers: user interface tier, business logic tier and access tier. The data of accelerator status and the data generated in experiment processes are managed with SQL Server DBMS, and the database is accessed based on the technology of ADO.NET. The status of facility, control parameters and testing waves are queried by the experiment number and experiment time. The demand of storage, management, browse, query and offline analysis are implemented entirely in this database system based on B/S architecture.
2010,
22.
Abstract:
A time-resolved measurement system of spot size for X-ray sources was constructed by coupling a gated CCD camera with a fast scintillator crystal. The spot size of the high-energy pulsed X-ray source from the Dragon-Ⅰ linear induction accelerator was measured at 10 ns intervals, and a curve of spot size versus time was obtained. An LYSO crystal array with a pixel size of 0.78 mm was also designed and tested in X-ray field, and primary experimental results show the array can be used for time-resolved spot size diagnosis of the high energy X-ray source and significantly improve the spatial resolution of X-ray images.
A time-resolved measurement system of spot size for X-ray sources was constructed by coupling a gated CCD camera with a fast scintillator crystal. The spot size of the high-energy pulsed X-ray source from the Dragon-Ⅰ linear induction accelerator was measured at 10 ns intervals, and a curve of spot size versus time was obtained. An LYSO crystal array with a pixel size of 0.78 mm was also designed and tested in X-ray field, and primary experimental results show the array can be used for time-resolved spot size diagnosis of the high energy X-ray source and significantly improve the spatial resolution of X-ray images.
2010,
22.
Abstract:
One-dimensional little-area Si PIN detectors array for high energy X-ray measurement was developed. The sensitivity, linear output current and time response of the Si PIN were calculated theoretically and also simulated using MC software EGSnrc. According to the theoretical study, little-area Si PIN detectors array can be used to detect high intensity and high energy X-ray with better spatio-temporal resolution(3 mm-8 ns). Primary experiments were carried out based on the theoretical design on “Dragon-Ⅰ” linear induction electron accelerator using the Si-PIN photoelectric cell and the corresponding amplifier. Rreasonable response of Si-PIN photoelectric cell was gained for optimum design of practical one-dimensional little-area Si PIN detectors array.
One-dimensional little-area Si PIN detectors array for high energy X-ray measurement was developed. The sensitivity, linear output current and time response of the Si PIN were calculated theoretically and also simulated using MC software EGSnrc. According to the theoretical study, little-area Si PIN detectors array can be used to detect high intensity and high energy X-ray with better spatio-temporal resolution(3 mm-8 ns). Primary experiments were carried out based on the theoretical design on “Dragon-Ⅰ” linear induction electron accelerator using the Si-PIN photoelectric cell and the corresponding amplifier. Rreasonable response of Si-PIN photoelectric cell was gained for optimum design of practical one-dimensional little-area Si PIN detectors array.
2010,
22.
Abstract:
In high energy flash radiography, enhancing the direct-to-scattered ratio(DSR) in receiving plane is favorable to the derivation of effective information. Monte-Carlo method is used to simulate the radiography process of French test object(FTO). Energy spectrum distribution of direct and scattering fluxes is obtained within the receiving domain. The method to improve the DSR in the receiving domain by energy spectrum optimization is proposed according to the distribution property. It is found that energy spectrum can be optimized by inserting an attenuation screen. Owing to its low absorption coefficient, tantalum is adopted as the material to optimize the energy spectrum with concerning practical manufacture condition. The maximum thickness of the attenuation screen is derived according t
In high energy flash radiography, enhancing the direct-to-scattered ratio(DSR) in receiving plane is favorable to the derivation of effective information. Monte-Carlo method is used to simulate the radiography process of French test object(FTO). Energy spectrum distribution of direct and scattering fluxes is obtained within the receiving domain. The method to improve the DSR in the receiving domain by energy spectrum optimization is proposed according to the distribution property. It is found that energy spectrum can be optimized by inserting an attenuation screen. Owing to its low absorption coefficient, tantalum is adopted as the material to optimize the energy spectrum with concerning practical manufacture condition. The maximum thickness of the attenuation screen is derived according t
2010,
22.
Abstract:
To better understand the characteristics of the impulse force formed by pulse current of electromagnetic rail propulsion system, and to explore effective ways to improve the support structure of rails, a set of impulse force test system was designed, and the work-related test situation was numerically simulated. Several impulse force waveforms formed by different pulse current waveforms were achieved by using a C-shape monolithic armature as a source of impulse force in this test system, and two curves of waveform were comparatively analyzed. Numerical calculation of the armature existing in the environment of coupling fields including electric field and magnetic field and force field was carried out by ANSYS/Multiphysics, the coupling force field was emphatically analyzed to calculate the
To better understand the characteristics of the impulse force formed by pulse current of electromagnetic rail propulsion system, and to explore effective ways to improve the support structure of rails, a set of impulse force test system was designed, and the work-related test situation was numerically simulated. Several impulse force waveforms formed by different pulse current waveforms were achieved by using a C-shape monolithic armature as a source of impulse force in this test system, and two curves of waveform were comparatively analyzed. Numerical calculation of the armature existing in the environment of coupling fields including electric field and magnetic field and force field was carried out by ANSYS/Multiphysics, the coupling force field was emphatically analyzed to calculate the
2010,
22.
Abstract:
The algorithms and numerical schemes of some usual external magnetic field loading modules were introduced and studied in detail for the 3D fully electromagnetic and PIC simulation code NEPTUNE. The loading of simple magnetic field distribution function and discrete magnetic field data, the loadings of magnetic field distributions produced by current elements of direct and helix lines and solenoid, and the loadings of magnetic fields produced by wiggler and permanent magnet were all included and discussed thoroughly. All the calculated results validate the credibility of these external magnetic field loading modules. As a practical example, a coaxial diode with electron beam emission under different guide magnetic fields was test. Its emission characteristics validate these field loading m
The algorithms and numerical schemes of some usual external magnetic field loading modules were introduced and studied in detail for the 3D fully electromagnetic and PIC simulation code NEPTUNE. The loading of simple magnetic field distribution function and discrete magnetic field data, the loadings of magnetic field distributions produced by current elements of direct and helix lines and solenoid, and the loadings of magnetic fields produced by wiggler and permanent magnet were all included and discussed thoroughly. All the calculated results validate the credibility of these external magnetic field loading modules. As a practical example, a coaxial diode with electron beam emission under different guide magnetic fields was test. Its emission characteristics validate these field loading m
2010,
22.
Abstract:
The surface flashover characteristics of insulations are studied, which are used in the laser-triggered surface flashover switch in vacuum. The experimental platform of laser-triggered surface flashover under pulsed voltage was built in the laboratory. Based on the platform, the experiment of laser-triggered surface flashover was carried out using flat electrodes and three kinds of column insulations, whose materials are nylon, polycarbonate and Al2O3, respectively. The results show that the self-flashover voltage of polycarbonate is the highest, and flashover delay time and jitter time decrease with the increase of pulsed voltage and laser energy density. With laser trigger, the jitter time of the insulations is about 1 ns and the jitter time of polycarbonate is the lowest. The delay time
The surface flashover characteristics of insulations are studied, which are used in the laser-triggered surface flashover switch in vacuum. The experimental platform of laser-triggered surface flashover under pulsed voltage was built in the laboratory. Based on the platform, the experiment of laser-triggered surface flashover was carried out using flat electrodes and three kinds of column insulations, whose materials are nylon, polycarbonate and Al2O3, respectively. The results show that the self-flashover voltage of polycarbonate is the highest, and flashover delay time and jitter time decrease with the increase of pulsed voltage and laser energy density. With laser trigger, the jitter time of the insulations is about 1 ns and the jitter time of polycarbonate is the lowest. The delay time
2010,
22.
Abstract:
A dielectric-coated sphere-cylinder electrode was designed and used for the generation of volume discharge in water. The generation of hydrogen peroxide was determined by the colorimetric method. The effect of different conditions such as pulse amplitude, pulse width and water conductivity was taken into consideration. The experimental results demonstrate that as voltage amplitude increases, the generation rate of hydrogen peroxide increases. The discharge transits from streamer mode to arc mode when the applied voltage is high enough. Meanwhile, the generation rate increases sharply. With the same voltage amplitude, the generation of hydrogen peroxide decreases with the increasing water conductivity, while increases with the increasing pulse frequency. The concentration of hydrogen peroxi
A dielectric-coated sphere-cylinder electrode was designed and used for the generation of volume discharge in water. The generation of hydrogen peroxide was determined by the colorimetric method. The effect of different conditions such as pulse amplitude, pulse width and water conductivity was taken into consideration. The experimental results demonstrate that as voltage amplitude increases, the generation rate of hydrogen peroxide increases. The discharge transits from streamer mode to arc mode when the applied voltage is high enough. Meanwhile, the generation rate increases sharply. With the same voltage amplitude, the generation of hydrogen peroxide decreases with the increasing water conductivity, while increases with the increasing pulse frequency. The concentration of hydrogen peroxi
2010,
22.
Abstract:
The measurement of charge separation potentials of metal targets irradiated by 107 W/cm2, 30 ns X-ray pulses produced by Z pinch on “Yang” accelerator (1 MA, 80 ns) shows kilovolt target potentials existing for 40 ns. The pinch load was tungsten wire array (3 mm in radius) consisting of 16 wires with a radius of 5 μm. The measurement also gives the distribution of potentials on the targets. The polarity of the potential indicates that the electrons move along target surfaces, not along the normal direction. The experimental results show that thermoelectric effect is the main mechanism causing this charge separation. The conclusions reveal that, electrons’ individual behavior including photoelectric effect and Compton effect dominates when targets are irradiated by
The measurement of charge separation potentials of metal targets irradiated by 107 W/cm2, 30 ns X-ray pulses produced by Z pinch on “Yang” accelerator (1 MA, 80 ns) shows kilovolt target potentials existing for 40 ns. The pinch load was tungsten wire array (3 mm in radius) consisting of 16 wires with a radius of 5 μm. The measurement also gives the distribution of potentials on the targets. The polarity of the potential indicates that the electrons move along target surfaces, not along the normal direction. The experimental results show that thermoelectric effect is the main mechanism causing this charge separation. The conclusions reveal that, electrons’ individual behavior including photoelectric effect and Compton effect dominates when targets are irradiated by
2010,
22.
Abstract:
A transmission grating spectrometer has been fabricated for the study of X-ray radiations from Z-pinch plasma. The spectrometer contains a 3 333 lp/mm gold transmission grating and an X-ray CCD to record time-integral spectral images. Two slits are employed in the spectrometer. One is used for 1D space resolving and the other, working together with the grating’s entrance slit, can collimate the incident X-rays and thus improve the spectral resolution of the spectrometer. The spectrometer has been used in Z-pinch experiments performed on Yang accelerator. When using Al wire arrays as Z-pinch loads, the Al K-shell lines and lines from Li-like ions were observed. In addition, by comparing the spectral image with the image obtained from an X-ray pinhole camera, the K-shell radiations emitted
A transmission grating spectrometer has been fabricated for the study of X-ray radiations from Z-pinch plasma. The spectrometer contains a 3 333 lp/mm gold transmission grating and an X-ray CCD to record time-integral spectral images. Two slits are employed in the spectrometer. One is used for 1D space resolving and the other, working together with the grating’s entrance slit, can collimate the incident X-rays and thus improve the spectral resolution of the spectrometer. The spectrometer has been used in Z-pinch experiments performed on Yang accelerator. When using Al wire arrays as Z-pinch loads, the Al K-shell lines and lines from Li-like ions were observed. In addition, by comparing the spectral image with the image obtained from an X-ray pinhole camera, the K-shell radiations emitted
2010,
22.
Abstract:
A supersonic single-shell gas-puff load has been developed for Z-pinch experiments on “Yang” accelerator. Using a fast responding pressure probe to measure the supersonic gas flow, impact pressure at different position and plenum pressure were acquired, which were combined with gas dynamics formulas to determine gas pressures and densities. The radial density profile displays that positions of gas shell varies with axial position, and the gas densities on axis increases as the distance from nozzle increases. Integral radial densities indicates that the linear mass density peaks at nozzle exit and decreases as increasing the distance from nozzle. Using single-shell supersonic gas-puff load, Z-pinch implosion experiments were performed on “Yang” accelerator. Primary analysis of implosion
A supersonic single-shell gas-puff load has been developed for Z-pinch experiments on “Yang” accelerator. Using a fast responding pressure probe to measure the supersonic gas flow, impact pressure at different position and plenum pressure were acquired, which were combined with gas dynamics formulas to determine gas pressures and densities. The radial density profile displays that positions of gas shell varies with axial position, and the gas densities on axis increases as the distance from nozzle increases. Integral radial densities indicates that the linear mass density peaks at nozzle exit and decreases as increasing the distance from nozzle. Using single-shell supersonic gas-puff load, Z-pinch implosion experiments were performed on “Yang” accelerator. Primary analysis of implosion
2010,
22.
Abstract:
A device for nano-powder production by electrical explosion of wires was designed and built. Eight wires housed in the discharge chamber are exploded one by one before opening the chamber for the collection of the produced nano-powder. To increase the rate of energy deposition into a wire, the electrical behavior of the discharge circuit including the exploding wire was simulated. The results showed that both reducing the circuit inductance and reducing the capacitance of the energy-storage capacitor (keeping the storage energy constant) can increase the energy deposition rate. To better understand the physical processes of the nano-powder formation by the wire vapor, a Mach-Zehnder interferometer was used to record the time evolution of the wire vapor as well as the plasma. A thermal expa
A device for nano-powder production by electrical explosion of wires was designed and built. Eight wires housed in the discharge chamber are exploded one by one before opening the chamber for the collection of the produced nano-powder. To increase the rate of energy deposition into a wire, the electrical behavior of the discharge circuit including the exploding wire was simulated. The results showed that both reducing the circuit inductance and reducing the capacitance of the energy-storage capacitor (keeping the storage energy constant) can increase the energy deposition rate. To better understand the physical processes of the nano-powder formation by the wire vapor, a Mach-Zehnder interferometer was used to record the time evolution of the wire vapor as well as the plasma. A thermal expa
2010,
22.
Abstract:
A kind of self-integrating capacitive divider is introduced to measure the diode load voltage on the Qiangguang-Ⅰ accelerator. The structure of the divider is given first and the static electric field of the divider is simulated by ANSYS. The calculation result shows that no significant effect is induced on the electric field between the anode board and the cathode board, when the divider is located in a small hole on the anode board. By using the square pulse voltage generator and the standard resistance divider the frequency response and the attenuation ratio of the capacitive divider are calibrated. At last the divider-measured voltage of the short-circuit load on the Qiangguang-Ⅰ accelerator is given.
A kind of self-integrating capacitive divider is introduced to measure the diode load voltage on the Qiangguang-Ⅰ accelerator. The structure of the divider is given first and the static electric field of the divider is simulated by ANSYS. The calculation result shows that no significant effect is induced on the electric field between the anode board and the cathode board, when the divider is located in a small hole on the anode board. By using the square pulse voltage generator and the standard resistance divider the frequency response and the attenuation ratio of the capacitive divider are calibrated. At last the divider-measured voltage of the short-circuit load on the Qiangguang-Ⅰ accelerator is given.
