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RSS2014 Vol. 26, No. 04
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2014,
26: 043001.
doi: 10.11884/HPLPB201426.043001
Abstract:
A two-dimensional plasma-filled metallic photonic crystal cavity structure is studied. Particle in cell technique (PIC) is used to establish the physical model. The field distribution properties, the mode frequency and the amplitude of the electronic field are illustrated under plasma-filled situation. Results show that the electric field intensity of each mode in cavity decreases with the increase of plasma density, the mode frequency increases with the increase of the normalized frequency, and different source positions stimulate different modes.
A two-dimensional plasma-filled metallic photonic crystal cavity structure is studied. Particle in cell technique (PIC) is used to establish the physical model. The field distribution properties, the mode frequency and the amplitude of the electronic field are illustrated under plasma-filled situation. Results show that the electric field intensity of each mode in cavity decreases with the increase of plasma density, the mode frequency increases with the increase of the normalized frequency, and different source positions stimulate different modes.
2014,
26: 043002.
doi: 10.11884/HPLPB201426.043002
Abstract:
The working principle and dispersion characteristics of nonlinear transmission line (NLTL) are discussed, and a simulation method is proposed for analyzing across coupled and magnetic saturation NLTL. This method is based on time-step iteration of finite difference equations of each circuit nodes, and the J-A model is employed to describe the magnetizing behavior of NiZn ferrite beads in this method. We simulated an NLTL operation mode, and a center frequency of wideband pulse of 165 MHz was obtained in the experiment, preliminarily verifying the feasibility of producing wideband pulse with NLTL.
The working principle and dispersion characteristics of nonlinear transmission line (NLTL) are discussed, and a simulation method is proposed for analyzing across coupled and magnetic saturation NLTL. This method is based on time-step iteration of finite difference equations of each circuit nodes, and the J-A model is employed to describe the magnetizing behavior of NiZn ferrite beads in this method. We simulated an NLTL operation mode, and a center frequency of wideband pulse of 165 MHz was obtained in the experiment, preliminarily verifying the feasibility of producing wideband pulse with NLTL.
2014,
26: 043003.
doi: 10.11884/HPLPB201426.043003
Abstract:
The peak power of a frequency-modulated microwave pulse could be improved greatly by the compression of the helically corrugated waveguide. Firstly, the dispersion relations of the helical corrugated waveguide are calculated and analyzed using the code programmed with Matlab. The dispersion characteristics on the variation of the amplitude and period of the corrugation are obtained. Then the power compression ratios are calculated under some typical conditions. Calculation results show that: the power compression ratio is very sensitive to the format of the frequency modulation. Under the same format of frequency modulation, the power compression ratio increases with the increasing of the time width and frequency width of the input pulse. For an input pulse of 40 ns and a frequency width 0.7 GHz(from 8.8 GHz to 9.5 GHz), the format of the frequency modulation is matched to the dispersion characteristics of the helically corrugated waveguide, the power compression ratio reaches 15, and the compression efficiency is about 40%.
The peak power of a frequency-modulated microwave pulse could be improved greatly by the compression of the helically corrugated waveguide. Firstly, the dispersion relations of the helical corrugated waveguide are calculated and analyzed using the code programmed with Matlab. The dispersion characteristics on the variation of the amplitude and period of the corrugation are obtained. Then the power compression ratios are calculated under some typical conditions. Calculation results show that: the power compression ratio is very sensitive to the format of the frequency modulation. Under the same format of frequency modulation, the power compression ratio increases with the increasing of the time width and frequency width of the input pulse. For an input pulse of 40 ns and a frequency width 0.7 GHz(from 8.8 GHz to 9.5 GHz), the format of the frequency modulation is matched to the dispersion characteristics of the helically corrugated waveguide, the power compression ratio reaches 15, and the compression efficiency is about 40%.
2014,
26: 043004.
doi: 10.11884/HPLPB201426.043004
Abstract:
A paralleled 2-dimension optimization code syncretized Genetic Algorithm and PIC code is developed to improve the level of design of high power microwave (HPM) sources. Both C-MILO and L-MILO are optimized using this optimization code. By optimization design, the efficiency of C-MILO rises to 15.4% from 10.8% and that of L-MILO rises from 12.6% to 17.7% while the input power keeps the same. It is received that both the output power and the efficiency of the two MILOS are improved considerably as their input power are changeless. All optimized models have reasonable geometry parameters and exact simulating spectra.
A paralleled 2-dimension optimization code syncretized Genetic Algorithm and PIC code is developed to improve the level of design of high power microwave (HPM) sources. Both C-MILO and L-MILO are optimized using this optimization code. By optimization design, the efficiency of C-MILO rises to 15.4% from 10.8% and that of L-MILO rises from 12.6% to 17.7% while the input power keeps the same. It is received that both the output power and the efficiency of the two MILOS are improved considerably as their input power are changeless. All optimized models have reasonable geometry parameters and exact simulating spectra.
2014,
26: 043005.
doi: 10.11884/HPLPB201426.043005
Abstract:
A set of equations for the non-linear propagation of high power microwave pulses in the atmosphere as well as the evolution of self-generated air plasma are deduced. A 1D code named Atmospheric Plasma Non-linear Evaluation in code (APNEIC) has been programmed in a local time domain reference frame moving with group velocity of the electromagnetic wave. The evolution of character parameters of the self-generated plasma such as the electron number density, the electron temperature, and the vibration temperature are studied. The simulation results show that during the breakdown startup stage the electron temperature is enhanced very rapidly to saturation values because of the rather low local seed free electrons, while the increase of electron numbers is relatively slow, but the electron temperature decreases soon from its saturation value with the avalanched increase of electrons.
A set of equations for the non-linear propagation of high power microwave pulses in the atmosphere as well as the evolution of self-generated air plasma are deduced. A 1D code named Atmospheric Plasma Non-linear Evaluation in code (APNEIC) has been programmed in a local time domain reference frame moving with group velocity of the electromagnetic wave. The evolution of character parameters of the self-generated plasma such as the electron number density, the electron temperature, and the vibration temperature are studied. The simulation results show that during the breakdown startup stage the electron temperature is enhanced very rapidly to saturation values because of the rather low local seed free electrons, while the increase of electron numbers is relatively slow, but the electron temperature decreases soon from its saturation value with the avalanched increase of electrons.
2014,
26: 043006.
doi: 10.11884/HPLPB201426.043006
Abstract:
By electron beam impacting experiment of metal target and copper foil pasted on the inside surface of collector, with high magnetic field and annular graphite cathode (38-39 mm), the space density distribution of electron beam in the foilless diode and its forming reasons are preliminarily studied. It is shown that the electron beam is at 37.2-40.2 mm in radial direction, and there are a high density region (38.8-39.4 mm) and a density maximum (39.2 mm) which tend to the outboard of the cathode in the electron beam. The radial density distribution of electron beam explosively emitted from the annular cathode of the foilless diode can be approximated by nonsymmetrical distribution.
By electron beam impacting experiment of metal target and copper foil pasted on the inside surface of collector, with high magnetic field and annular graphite cathode (38-39 mm), the space density distribution of electron beam in the foilless diode and its forming reasons are preliminarily studied. It is shown that the electron beam is at 37.2-40.2 mm in radial direction, and there are a high density region (38.8-39.4 mm) and a density maximum (39.2 mm) which tend to the outboard of the cathode in the electron beam. The radial density distribution of electron beam explosively emitted from the annular cathode of the foilless diode can be approximated by nonsymmetrical distribution.
2014,
26: 043101.
doi: 10.11884/HPLPB201426.043101
Abstract:
The equivalent-conductivity method is applied to the simulation work of electromagnetic transmission attenuation for 345 GHz FWG-TWT(folded waveguide traveling-wave tube). The paper studies the cold model of slow-wave structure and does research on the big factors which influence transmission attenuation, such as the beam tunnels diameter, processing roughness. A big beam tunnel or a large roughness will result in serious electromagnetic attenuation. The paper also studies the hot model of slow-wave structure, and analyzes the effects of electromagnetic attenuation on gain, bandwidth, best length of slow wave structure. Results show that electromagnetic attenuation causes gain reduction and bandwidth decreases.
The equivalent-conductivity method is applied to the simulation work of electromagnetic transmission attenuation for 345 GHz FWG-TWT(folded waveguide traveling-wave tube). The paper studies the cold model of slow-wave structure and does research on the big factors which influence transmission attenuation, such as the beam tunnels diameter, processing roughness. A big beam tunnel or a large roughness will result in serious electromagnetic attenuation. The paper also studies the hot model of slow-wave structure, and analyzes the effects of electromagnetic attenuation on gain, bandwidth, best length of slow wave structure. Results show that electromagnetic attenuation causes gain reduction and bandwidth decreases.
2014,
26: 043201.
doi: 10.11884/HPLPB201426.043201
Abstract:
Strong electromagnetic interference in the high power linear induction accelerator (LIA) is disadvantageous to electron-beam-parameters measurement and diagnosis system. In this paper, electromagnetic interference effect on time-resolved electron-beam-parameter measurement system is analyzed, and the method for controlling the electromagnetic interference is discussed. With fiber embedded technology, narrow impulse signals are dependably transmitted, signal delay jitter is less than 2 ns. The experiment showed that the measuring system is characterized with the features of high reliability and achieves the application requirements.
Strong electromagnetic interference in the high power linear induction accelerator (LIA) is disadvantageous to electron-beam-parameters measurement and diagnosis system. In this paper, electromagnetic interference effect on time-resolved electron-beam-parameter measurement system is analyzed, and the method for controlling the electromagnetic interference is discussed. With fiber embedded technology, narrow impulse signals are dependably transmitted, signal delay jitter is less than 2 ns. The experiment showed that the measuring system is characterized with the features of high reliability and achieves the application requirements.
2014,
26: 044001.
doi: 10.11884/HPLPB201426.044001
Abstract:
A novel off-line diagnosis method for ion beams of the sealed tube neutron generator is introduced, which is based on secondary ion mass spectrometry (SIMS). The method has high resolution and can provide intensity distribution of ion beam profile and ion composition. The feasibility of the method was analyzed and discussed by numerical simulation, and verified by experiment. The preliminary experimental results indicate the hydrogen distribution and titanium distribution. This method can be used to diagnose the ion beam profile for the sealed tube neutron generator, and can provide confirmation and complement for other diagnostic methods.
A novel off-line diagnosis method for ion beams of the sealed tube neutron generator is introduced, which is based on secondary ion mass spectrometry (SIMS). The method has high resolution and can provide intensity distribution of ion beam profile and ion composition. The feasibility of the method was analyzed and discussed by numerical simulation, and verified by experiment. The preliminary experimental results indicate the hydrogen distribution and titanium distribution. This method can be used to diagnose the ion beam profile for the sealed tube neutron generator, and can provide confirmation and complement for other diagnostic methods.
2014,
26: 044002.
doi: 10.11884/HPLPB201426.044002
Abstract:
The flash X-ray radiography of the French Test Object (FTO) was studied and a 3-grade collimating system was designed to reduce the generation of scattered background. Except for the traditional 2-grade collimating system, we adopted a third collimator to further control the scattered background. Monte-Carlo simulations suggest that the 3-grade collimating system can effectively control the influence of scattering. The direct-exposure scattered-exposure ratio along each border between different materials can be greatly improved in the accepting plane.
The flash X-ray radiography of the French Test Object (FTO) was studied and a 3-grade collimating system was designed to reduce the generation of scattered background. Except for the traditional 2-grade collimating system, we adopted a third collimator to further control the scattered background. Monte-Carlo simulations suggest that the 3-grade collimating system can effectively control the influence of scattering. The direct-exposure scattered-exposure ratio along each border between different materials can be greatly improved in the accepting plane.
2014,
26: 044003.
doi: 10.11884/HPLPB201426.044003
Abstract:
In Z-pinch diagnostics, the soft X-ray scintillator powermeter is an important instrument which is applied in measuring the yield of soft X-ray radiating from Z-pinch plasma on Yang machine and also on the PTS. The spectral responsivity is a key parameter of the powermeter. We calibrated the spectral responsivity of the scintillator and photomultiplier tube system from 50 eV to 1800 eV on Beijing Synchrotron Radiation Facility (BSRF) for obtaining the spectral responsivity of the powermeter. There required another sensitivity comparison between the photomultiplier tube and the photoelectric tube for completing the spectral responsivity calibration for the powermeter. We designed a relative sensitivity calibration system for this job. In this paper, we present the configuration and working procedure of the relative sensitivity calibration system. The calibration method and calibration results are reported as well.
In Z-pinch diagnostics, the soft X-ray scintillator powermeter is an important instrument which is applied in measuring the yield of soft X-ray radiating from Z-pinch plasma on Yang machine and also on the PTS. The spectral responsivity is a key parameter of the powermeter. We calibrated the spectral responsivity of the scintillator and photomultiplier tube system from 50 eV to 1800 eV on Beijing Synchrotron Radiation Facility (BSRF) for obtaining the spectral responsivity of the powermeter. There required another sensitivity comparison between the photomultiplier tube and the photoelectric tube for completing the spectral responsivity calibration for the powermeter. We designed a relative sensitivity calibration system for this job. In this paper, we present the configuration and working procedure of the relative sensitivity calibration system. The calibration method and calibration results are reported as well.
2014,
26: 045001.
doi: 10.11884/HPLPB201426.045001
Abstract:
In order to explore the effect of the pulse power discharge and surface processing on polytetrafluoroethene(PTFE) film, we used the means of pulse transformer to set up a repetitive rating high voltage pulse power with the semiconductor solid switch IGBT, and finally achieved the target, a variable voltage amplitude of 15-20 kV, a pulse width of 10-15 s, a pulse rise time of about 1-3 s, and a variable repetitive rating 10-15 kHz. Meanwhile, we had a measurement for the water contact angle of the PTFE film before and after processing, and found that the water contact angle decreased from 112 to about 85.
In order to explore the effect of the pulse power discharge and surface processing on polytetrafluoroethene(PTFE) film, we used the means of pulse transformer to set up a repetitive rating high voltage pulse power with the semiconductor solid switch IGBT, and finally achieved the target, a variable voltage amplitude of 15-20 kV, a pulse width of 10-15 s, a pulse rise time of about 1-3 s, and a variable repetitive rating 10-15 kHz. Meanwhile, we had a measurement for the water contact angle of the PTFE film before and after processing, and found that the water contact angle decreased from 112 to about 85.
2014,
26: 045002.
doi: 10.11884/HPLPB201426.045002
Abstract:
The gas switch is one of the key components in pulsed power system and the impendence of spark channel greatly affects the efficiency of power delivery and the rising time of voltage applied to the load, but accurate measurement of spark resistance under oscillatory damped current pulse is difficult. In this paper, a spectrographic method is put forward. Through measuring the emission spectrum of spark channel with time and spatial resolution, the spark radius and conductivity are estimated and the spark resistance is calculated. The results show that electron temperature of nitrogen spark is about 2-3 eV while the conductivity of spark channel increases rapidly at first and then gradually decreases with a maximum of 16 000 S. As the spark channel develops, spark resistance drops rapidly from insulation and reaches a saturation value, and the time-dependent property of spark resistance fits well with the calculated results. In the pressure ranged from 3 to 100 kPa, the spark radius decreases and the spark resistance increases with the increase of pressure.
The gas switch is one of the key components in pulsed power system and the impendence of spark channel greatly affects the efficiency of power delivery and the rising time of voltage applied to the load, but accurate measurement of spark resistance under oscillatory damped current pulse is difficult. In this paper, a spectrographic method is put forward. Through measuring the emission spectrum of spark channel with time and spatial resolution, the spark radius and conductivity are estimated and the spark resistance is calculated. The results show that electron temperature of nitrogen spark is about 2-3 eV while the conductivity of spark channel increases rapidly at first and then gradually decreases with a maximum of 16 000 S. As the spark channel develops, spark resistance drops rapidly from insulation and reaches a saturation value, and the time-dependent property of spark resistance fits well with the calculated results. In the pressure ranged from 3 to 100 kPa, the spark radius decreases and the spark resistance increases with the increase of pressure.
2014,
26: 045003.
doi: 10.11884/HPLPB201426.045003
Abstract:
In order to study the characteristics of a plasma jet array, the discharge was driven by a microsecond pulse generator with 1-s rise time and 2-s duration. With a needle-ring configuration, the discharge properties of the helium plasma jet array at different ground electrode positions and repetition pulse frequencies were studied by means of voltage and current measurement and light-emission pictures. The experimental results show that the discharge was initiated at the edges of the plasma jet array at first. With the increase of the applied voltage, the plasma jet occurred in the middle tube, and the plasma jet array was finally formed. When the gap between the ground electrode and the tube nozzle increased, the amplitude of discharge current increased at first, and then decreased (the maximum value was at the gap of 20 mm). With the increase of repetition pulse frequency, the discharge mode changed from filamentary discharge to homogeneous discharge, the discharge current decreased at first, and then remained unchanged.
In order to study the characteristics of a plasma jet array, the discharge was driven by a microsecond pulse generator with 1-s rise time and 2-s duration. With a needle-ring configuration, the discharge properties of the helium plasma jet array at different ground electrode positions and repetition pulse frequencies were studied by means of voltage and current measurement and light-emission pictures. The experimental results show that the discharge was initiated at the edges of the plasma jet array at first. With the increase of the applied voltage, the plasma jet occurred in the middle tube, and the plasma jet array was finally formed. When the gap between the ground electrode and the tube nozzle increased, the amplitude of discharge current increased at first, and then decreased (the maximum value was at the gap of 20 mm). With the increase of repetition pulse frequency, the discharge mode changed from filamentary discharge to homogeneous discharge, the discharge current decreased at first, and then remained unchanged.
2014,
26: 045004.
doi: 10.11884/HPLPB201426.045004
Abstract:
A solid state high power long pulse generator was designed based on the technology of the magnetic switch, low impedance pulse forming line, and inductive voltage adder, which fully profited from the insulation rules, implemented modularization, and could improve the average power, stability, credibility and life of the whole system potentially. The circuit model and the key sub-systems were developed to examine the whole system. Experimental researches were carried out on the whole system. The preliminary results achieved on a dummy load show that the output pulsed power is about 2.1 GW and the pulse width about 170 ns, which verifies the design concept.
A solid state high power long pulse generator was designed based on the technology of the magnetic switch, low impedance pulse forming line, and inductive voltage adder, which fully profited from the insulation rules, implemented modularization, and could improve the average power, stability, credibility and life of the whole system potentially. The circuit model and the key sub-systems were developed to examine the whole system. Experimental researches were carried out on the whole system. The preliminary results achieved on a dummy load show that the output pulsed power is about 2.1 GW and the pulse width about 170 ns, which verifies the design concept.
2014,
26: 045005.
doi: 10.11884/HPLPB201426.045005
Abstract:
The super-fast pulse semiconductor device introduced in this article, is a kind of punch-through device with voltage up to 5000 V and current rise rate above 20 kA/s. Through matching with parameters, the pulse peak current can reach several hundreds of kA. The multiple-round-cell integrated structure and the diffusion technology which combines buffer layer and anode transparent layer, make the device has advantages compared with traditional thyristors in voltage drop and turn-on characteristics. This super-fast pulse semiconductor device which has been optimized on design and process technology, can meet the production condition.
The super-fast pulse semiconductor device introduced in this article, is a kind of punch-through device with voltage up to 5000 V and current rise rate above 20 kA/s. Through matching with parameters, the pulse peak current can reach several hundreds of kA. The multiple-round-cell integrated structure and the diffusion technology which combines buffer layer and anode transparent layer, make the device has advantages compared with traditional thyristors in voltage drop and turn-on characteristics. This super-fast pulse semiconductor device which has been optimized on design and process technology, can meet the production condition.
2014,
26: 045006.
doi: 10.11884/HPLPB201426.045006
Abstract:
This paper describes the preliminary experiments of measuring the in-bore velocity in 30 mm 25 mm caliber augmented railgun with W-band Doppler radar. The results indicate that the radar signals are strongly affected by pulsed magnetic field and armature-rail electrical contact. At low charging voltage, no arc generated between contact surfaces and the whole in-bore velocity was obtained; while at higher charging voltage, due to the generation of electrical arcs, the radar signal was attenuated too much and the velocity results was poor.
This paper describes the preliminary experiments of measuring the in-bore velocity in 30 mm 25 mm caliber augmented railgun with W-band Doppler radar. The results indicate that the radar signals are strongly affected by pulsed magnetic field and armature-rail electrical contact. At low charging voltage, no arc generated between contact surfaces and the whole in-bore velocity was obtained; while at higher charging voltage, due to the generation of electrical arcs, the radar signal was attenuated too much and the velocity results was poor.
2014,
26: 045007.
doi: 10.11884/HPLPB201426.045007
Abstract:
Based on the physical model of the electromagnetic railgun, a quantitative expression of sliding contact resistance of electromagnetic railgun is derived. The expression is related to the rail current, muzzle voltage, in-bore velocity of the armature and the rail configuration. The calculated sliding contact resistances between armature and rail depend on rail current. The resistance is different at different region of the rail current. At flat region, the contact resistance is about 0.2 m and at the rising and falling regions, the contact resistance reaches 3 m.
Based on the physical model of the electromagnetic railgun, a quantitative expression of sliding contact resistance of electromagnetic railgun is derived. The expression is related to the rail current, muzzle voltage, in-bore velocity of the armature and the rail configuration. The calculated sliding contact resistances between armature and rail depend on rail current. The resistance is different at different region of the rail current. At flat region, the contact resistance is about 0.2 m and at the rising and falling regions, the contact resistance reaches 3 m.
2014,
26: 045008.
doi: 10.11884/HPLPB201426.045008
Abstract:
An on-line measurement system based on Kerr effect is established to investigate the surface electric field of insulators stressed by nanosecond high-voltage (HV) pulse in vacuum. A 180 kV Marx generator with the high-voltage cable as the pulse forming line are utilized to output a square nanosecond HV pulse stressing on insulator specimen in Kerr cell, once a gas switch is conducted by a laser pulse emitted from a YAG laser. And a synchronous controlling apparatus is developed to make sure that the measurement on surface electric field is performed during the HV pulse being stressing on the insulator. Accordingly, a preliminary experimental observation on surface electric field is performed.
An on-line measurement system based on Kerr effect is established to investigate the surface electric field of insulators stressed by nanosecond high-voltage (HV) pulse in vacuum. A 180 kV Marx generator with the high-voltage cable as the pulse forming line are utilized to output a square nanosecond HV pulse stressing on insulator specimen in Kerr cell, once a gas switch is conducted by a laser pulse emitted from a YAG laser. And a synchronous controlling apparatus is developed to make sure that the measurement on surface electric field is performed during the HV pulse being stressing on the insulator. Accordingly, a preliminary experimental observation on surface electric field is performed.
2014,
26: 045009.
doi: 10.11884/HPLPB201426.045009
Abstract:
For the special need of wide variety of current waveforms during the magnetically driven isentropic compression experiment, this paper describes experiments that can shape the output current rise time on a refurbished 1.0 MV linear transformer driver(LTD) cavity. Forty-eight switches were divided into four groups, and each group of switches were triggered by one high voltage cable. Three sets of trigger cables with different length were conducted. The experimental results show that 0~100% rise time of output current can increase to 436.0 ns compared with 301.2 ns when all the switches are triggered simultaneously. However, the peak current will decrease from 294.0 kA to 210.2 kA with initial charge voltage of 32 kV. The closing time of forty switches were achieved by using fiber diagnostics system which could measure the switch optic signal during the discharge state. Based on the closing time of forty switches acquired in the experiment, the circuit model of 1 MA-LTD cavity was constructed in PSpice. The influence of the brick that has been triggered early in LTD cavity to other bricks was analyzed. This preliminary experiment results show that the LTD cavity can shape the output pulse with the aid of different trigger sequence.
For the special need of wide variety of current waveforms during the magnetically driven isentropic compression experiment, this paper describes experiments that can shape the output current rise time on a refurbished 1.0 MV linear transformer driver(LTD) cavity. Forty-eight switches were divided into four groups, and each group of switches were triggered by one high voltage cable. Three sets of trigger cables with different length were conducted. The experimental results show that 0~100% rise time of output current can increase to 436.0 ns compared with 301.2 ns when all the switches are triggered simultaneously. However, the peak current will decrease from 294.0 kA to 210.2 kA with initial charge voltage of 32 kV. The closing time of forty switches were achieved by using fiber diagnostics system which could measure the switch optic signal during the discharge state. Based on the closing time of forty switches acquired in the experiment, the circuit model of 1 MA-LTD cavity was constructed in PSpice. The influence of the brick that has been triggered early in LTD cavity to other bricks was analyzed. This preliminary experiment results show that the LTD cavity can shape the output pulse with the aid of different trigger sequence.
2014,
26: 045010.
doi: 10.11884/HPLPB201426.045010
Abstract:
The relationships between voltage and current, self-limited flow and loss front propagation speed of long MITL were studied based on particle-in-cell simulation. Different MITL models which were established under the steady-state assumptions were compared. Mendel model is more accurate than parapotential model and collisional model when depicting the relationship between long MITL voltage and current. Rescaled model is more accurate than Mendel model and parapotential model when computing the anode current at self-limited flow of long MITL. The loss front propagation speed is variable along power flow direction in long MITL, the speed is related with rise rate of input voltage.
The relationships between voltage and current, self-limited flow and loss front propagation speed of long MITL were studied based on particle-in-cell simulation. Different MITL models which were established under the steady-state assumptions were compared. Mendel model is more accurate than parapotential model and collisional model when depicting the relationship between long MITL voltage and current. Rescaled model is more accurate than Mendel model and parapotential model when computing the anode current at self-limited flow of long MITL. The loss front propagation speed is variable along power flow direction in long MITL, the speed is related with rise rate of input voltage.
2014,
26: 045011.
doi: 10.11884/HPLPB201426.045011
Abstract:
A repetitive frequency and nanosecond-pulsed generator based on the semiconductor opening switch (SOS) technology is developed, in which the pulse compression unit is realized by several radio frequency (RF) MOSFETs and a saturable linear transformer driver (LTD). The RF MOSFETs are employed to obtain the forward pumping current pulses with the duration of decades of nanoseconds; the saturable LTD is to raise the pulse voltage, compress the pulse width and pump SOS reversely. The SOS assembly cuts off the reverse current in a few nanoseconds that leads to narrow output pulse formation on an external load. The experimental results show that the output pulses of the SOS generator are amplitude 11 kV and width 2 ns on a 50 resistive load. Due to the repetitive ability of RF MOSFETs, the generator can operate at repetitive frequency of larger than 20 kHz.
A repetitive frequency and nanosecond-pulsed generator based on the semiconductor opening switch (SOS) technology is developed, in which the pulse compression unit is realized by several radio frequency (RF) MOSFETs and a saturable linear transformer driver (LTD). The RF MOSFETs are employed to obtain the forward pumping current pulses with the duration of decades of nanoseconds; the saturable LTD is to raise the pulse voltage, compress the pulse width and pump SOS reversely. The SOS assembly cuts off the reverse current in a few nanoseconds that leads to narrow output pulse formation on an external load. The experimental results show that the output pulses of the SOS generator are amplitude 11 kV and width 2 ns on a 50 resistive load. Due to the repetitive ability of RF MOSFETs, the generator can operate at repetitive frequency of larger than 20 kHz.
2014,
26: 045012.
doi: 10.11884/HPLPB201426.045012
Abstract:
A kind of compact stacked Blumlein nano-second pulse forming lines was studied in this paper, and the effect of circuits distribution parameter on output voltage of 2-staged stacked Blumlein pulse forming lines (PFLs) was analyzed and simulated by PSpice. The results show that the switchs on-resistance reduces the amplitude of output voltage, and the influence of the switchs inductance is greater than the influence of the loads inductance. The electromagnetic coupling effect of 2-stage Blumlein PFLs with different stacked structures was simulated by using XFDTD based on the principle of finite difference time domain method. The experiments of multi-stage stacked Blumlein PFLs were performed. The results show that, stacked Blumlein PFLs, based on ceramic solid-state transmission lines and GaAs photoconductive switches, achieve the superposition of output voltage, which could generate a nano-second high-voltage pulse.
A kind of compact stacked Blumlein nano-second pulse forming lines was studied in this paper, and the effect of circuits distribution parameter on output voltage of 2-staged stacked Blumlein pulse forming lines (PFLs) was analyzed and simulated by PSpice. The results show that the switchs on-resistance reduces the amplitude of output voltage, and the influence of the switchs inductance is greater than the influence of the loads inductance. The electromagnetic coupling effect of 2-stage Blumlein PFLs with different stacked structures was simulated by using XFDTD based on the principle of finite difference time domain method. The experiments of multi-stage stacked Blumlein PFLs were performed. The results show that, stacked Blumlein PFLs, based on ceramic solid-state transmission lines and GaAs photoconductive switches, achieve the superposition of output voltage, which could generate a nano-second high-voltage pulse.
2014,
26: 045013.
doi: 10.11884/HPLPB201426.045013
Abstract:
A novel plasma-jet triggered gas switch (PJTGS) triggered by plasma jet is proposed to improve the working behaviour of gas switches, such as the jitter and pre-fire probability under low working ratio. The PJTGS has the configuration of a triple-electrode electric field distortion switch, but a micro-incentive chamber is embedded in the trigger electrode to form plasma jet. The influences of trigger voltage and pressure on characteristics of the PJTGS are studied. The differences of trigger performance of the PJTGS at the field distortion and plasma-jet triggering are investigated. In addition, the effects of trigger voltage are also documented. The results show that the height of plasma jet is influenced by gas pressure and trigger voltage. The jitter of the overvoltage gap can be reduced by the plasma-jet triggering. Increasing trigger voltage not only reduces switch jitter, but also broadens the range of working coefficient. When the working ratio is 27.4% and trigger voltage is 80 kV, the PJTGS can still be triggered with the delay time of 97 ns and jitter of 3.5 ns.
A novel plasma-jet triggered gas switch (PJTGS) triggered by plasma jet is proposed to improve the working behaviour of gas switches, such as the jitter and pre-fire probability under low working ratio. The PJTGS has the configuration of a triple-electrode electric field distortion switch, but a micro-incentive chamber is embedded in the trigger electrode to form plasma jet. The influences of trigger voltage and pressure on characteristics of the PJTGS are studied. The differences of trigger performance of the PJTGS at the field distortion and plasma-jet triggering are investigated. In addition, the effects of trigger voltage are also documented. The results show that the height of plasma jet is influenced by gas pressure and trigger voltage. The jitter of the overvoltage gap can be reduced by the plasma-jet triggering. Increasing trigger voltage not only reduces switch jitter, but also broadens the range of working coefficient. When the working ratio is 27.4% and trigger voltage is 80 kV, the PJTGS can still be triggered with the delay time of 97 ns and jitter of 3.5 ns.
2014,
26: 045014.
doi: 10.11884/HPLPB201426.045014
Abstract:
The evolution of single-wire and dual-wire electrical explosion of 8 m- and 10 m- W was investigated by X-ray backlighting using the X-pinch as a soft X-ray source. The experiments were carried out on the pulsed power generator PPG-1 (400 kA/500 kV/100 ns) which was designed and constructed by Department of Electrical Engineering of Tsinghua University. The X-pinch as the X-ray source and the tungsten wire as the object are installed between the anode and the cathode and in the place of a current-return rod, respectively. The X-ray films of high resolution and high sensitivity were used to record the results. The current sensor and Rogowski coil of our own design were used to monitor the current. In order to observe the evolution of mass density distribution of the electrical explosion of single-wire of tungsten, the step wedge was designed. By a large number of imaging experiments, the physical images of wire core expansion, the formation and outward diffusion of the coronal plasma and the mass density distribution based on the original film were obtained. The conductance of 8 m-W was also calculated using voltage and current data.
The evolution of single-wire and dual-wire electrical explosion of 8 m- and 10 m- W was investigated by X-ray backlighting using the X-pinch as a soft X-ray source. The experiments were carried out on the pulsed power generator PPG-1 (400 kA/500 kV/100 ns) which was designed and constructed by Department of Electrical Engineering of Tsinghua University. The X-pinch as the X-ray source and the tungsten wire as the object are installed between the anode and the cathode and in the place of a current-return rod, respectively. The X-ray films of high resolution and high sensitivity were used to record the results. The current sensor and Rogowski coil of our own design were used to monitor the current. In order to observe the evolution of mass density distribution of the electrical explosion of single-wire of tungsten, the step wedge was designed. By a large number of imaging experiments, the physical images of wire core expansion, the formation and outward diffusion of the coronal plasma and the mass density distribution based on the original film were obtained. The conductance of 8 m-W was also calculated using voltage and current data.
2014,
26: 045015.
doi: 10.11884/HPLPB201426.045015
Abstract:
This paper concentrates on the inner pressure in the cylindrical metallized polypropylene film capacitor (MPPFC) winding. Firstly, the influences of inner pressure on self-healing and lifetime are investigated. Lifetime can be extended by inner pressure strengthening. Secondly, an inner pressure calculation formula is presented. Finally, the experimental results show that lifetime can be extended by 30% with rational heat treatment and by 38% when the number of wrapped films increases from 20 to 100.
This paper concentrates on the inner pressure in the cylindrical metallized polypropylene film capacitor (MPPFC) winding. Firstly, the influences of inner pressure on self-healing and lifetime are investigated. Lifetime can be extended by inner pressure strengthening. Secondly, an inner pressure calculation formula is presented. Finally, the experimental results show that lifetime can be extended by 30% with rational heat treatment and by 38% when the number of wrapped films increases from 20 to 100.
2014,
26: 045016.
doi: 10.11884/HPLPB201426.045016
Abstract:
The operational factors (voltage, temperature) that influence the lifetime of metallized polypropylene film capacitor(MPPFCs) are analyzed. The relationship between MPPFC elements and MPPFC prototypes in terms of lifetime is presented by a reliability analysis of the Weibull distribution. A lifetime prediction model based on the accelerating lifetime test of the element is established. Finally, lifetime tests of MPPFC prototypes and elements are performed to validate the prediction model. The results suggest that the predicted lifetime of MPPFC elements and prototypes could match well with the experimental data.
The operational factors (voltage, temperature) that influence the lifetime of metallized polypropylene film capacitor(MPPFCs) are analyzed. The relationship between MPPFC elements and MPPFC prototypes in terms of lifetime is presented by a reliability analysis of the Weibull distribution. A lifetime prediction model based on the accelerating lifetime test of the element is established. Finally, lifetime tests of MPPFC prototypes and elements are performed to validate the prediction model. The results suggest that the predicted lifetime of MPPFC elements and prototypes could match well with the experimental data.
2014,
26: 045017.
doi: 10.11884/HPLPB201426.045017
Abstract:
Metallized polypropylene film capacitors (MPPFCs) are key components in pulsed power systems. This paper mainly concentrates on the effect of the reverse voltage on the lifetime performance. Firstly the effect of discharge current on the lifetime performance of capacitors is introduced. Secondly experiment is designed to investigate the lifetime under different voltage reversal coefficients (). The results indicate that the lifetime is extremely sensitive to in the range of 9.4% to 65%, and the lifetime of MPPFCs decreases with in index. Based on the experimental results, an empirically derived life-scaling equation is given by statistical analysis, which can predict the lifetime of MPPFCs under different .
Metallized polypropylene film capacitors (MPPFCs) are key components in pulsed power systems. This paper mainly concentrates on the effect of the reverse voltage on the lifetime performance. Firstly the effect of discharge current on the lifetime performance of capacitors is introduced. Secondly experiment is designed to investigate the lifetime under different voltage reversal coefficients (). The results indicate that the lifetime is extremely sensitive to in the range of 9.4% to 65%, and the lifetime of MPPFCs decreases with in index. Based on the experimental results, an empirically derived life-scaling equation is given by statistical analysis, which can predict the lifetime of MPPFCs under different .
2014,
26: 045018.
doi: 10.11884/HPLPB201426.045018
Abstract:
The transmission character of Blumlein lines constructed by glass-ceramic plate transmission lines with different electrode width is studied. In order to achieve high-voltage fast-pulse output, positive mismatch load and high field strength photoconductive semiconductor switches were used. In the experiments, high voltage pulses with flat top and 9-ns pulse width were obtained, and the pulse amplitude was more than 20 kV. Low bias voltage causes high PCSS resistance so that output efficiency becomes low.
The transmission character of Blumlein lines constructed by glass-ceramic plate transmission lines with different electrode width is studied. In order to achieve high-voltage fast-pulse output, positive mismatch load and high field strength photoconductive semiconductor switches were used. In the experiments, high voltage pulses with flat top and 9-ns pulse width were obtained, and the pulse amplitude was more than 20 kV. Low bias voltage causes high PCSS resistance so that output efficiency becomes low.
2014,
26: 045019.
doi: 10.11884/HPLPB201426.045019
Abstract:
The three-dimensional electromagnetic fields simulation of nonuniform transmission lines that were under consideration for the next generation of Z-pinch drivers was performed by a code called CST microwave studio. A coaxial exponential line model was established in which the inside radius of the outer conductor is 100 mm, the characteristic impedance is 0.203 at the input port and 2.16 at the output port and the input voltage is half-sine pulse wave as TEM mode with an angular frequency of 14106 rad/s. A little energy of non-TEM mode is found during the transmission process. The more severely the radius of the line changes, the more energy of non-TEM mode is found. If the length of the transmission line is long enough, the difference of voltage transmission efficiency between electromagnetic fields and circuit simulation will be less than 1%. In this situation, results of electromagnetic fields simulation can be replaced by circuit situation.
The three-dimensional electromagnetic fields simulation of nonuniform transmission lines that were under consideration for the next generation of Z-pinch drivers was performed by a code called CST microwave studio. A coaxial exponential line model was established in which the inside radius of the outer conductor is 100 mm, the characteristic impedance is 0.203 at the input port and 2.16 at the output port and the input voltage is half-sine pulse wave as TEM mode with an angular frequency of 14106 rad/s. A little energy of non-TEM mode is found during the transmission process. The more severely the radius of the line changes, the more energy of non-TEM mode is found. If the length of the transmission line is long enough, the difference of voltage transmission efficiency between electromagnetic fields and circuit simulation will be less than 1%. In this situation, results of electromagnetic fields simulation can be replaced by circuit situation.
2014,
26: 045020.
doi: 10.11884/HPLPB201426.045020
Abstract:
Compared to the traditional method for surface treatment, non-thermal plasmas have advantages such as low pollution, simple process and low cost. In the paper, non-thermal plasmas are generated by dielectric barrier discharge (DBD) excited by China-made nanosecond-pulse generator with a rise time of ~70 ns and a full width at half maximum of ~100 ns. Such plasmas are used to modify the hydrophobic of the surface of polyethylene terephthalate (PET) in atmospheric carbon tetrafluoride (CF4). The static water contact angle of the PET surface is measured before and after treatment. The effects of CF4 flow, applied voltage, treatment time and CF4 ratio on modification performance are presented. The results show that the hydrophobic of the PET surface can be achieved using DBD plasmas. The static water contact angle of the PET surface can be up to 100 from 66.
Compared to the traditional method for surface treatment, non-thermal plasmas have advantages such as low pollution, simple process and low cost. In the paper, non-thermal plasmas are generated by dielectric barrier discharge (DBD) excited by China-made nanosecond-pulse generator with a rise time of ~70 ns and a full width at half maximum of ~100 ns. Such plasmas are used to modify the hydrophobic of the surface of polyethylene terephthalate (PET) in atmospheric carbon tetrafluoride (CF4). The static water contact angle of the PET surface is measured before and after treatment. The effects of CF4 flow, applied voltage, treatment time and CF4 ratio on modification performance are presented. The results show that the hydrophobic of the PET surface can be achieved using DBD plasmas. The static water contact angle of the PET surface can be up to 100 from 66.
2014,
26: 045021.
doi: 10.11884/HPLPB201426.045021
Abstract:
This article discusses the overall system design, manufacturing and testing process of the main switch and the pre-ionization switch in the high energy module. A two-electrode gas switch is selected in the main discharge circuit as the main switch, because it has a long working life under the current which has high value and low rise time, and a pulse transformer-based main switch trigger generator is thus constructed, the pressure control device is an auxiliary equipment of the system. While in the pre-ionization circuit, a three-electrode gas switch is selected as the discharge switch, and the principles of a trigger generator are given, the generator could both output high voltage and large current. Finally, the tests of electrical characteristics show that the two-electrode switch can sustain a peak current over 700 kA with a total volume of more than 200 kC transferred, in addition the switch life can be extended through the replacement of electrodes. Under the absolute pressure of 130 kPa and the charging voltage of 23 kV, the average breakdown delay of the three-electrode gas switch is 7.5 s, the delay jitter is 0.656 s, and the life test results of the pre-ionization switch show that the switch has 4000 times working life without replacing the graphite electrodes, and the total transferred charge exceeds 10 kC.
This article discusses the overall system design, manufacturing and testing process of the main switch and the pre-ionization switch in the high energy module. A two-electrode gas switch is selected in the main discharge circuit as the main switch, because it has a long working life under the current which has high value and low rise time, and a pulse transformer-based main switch trigger generator is thus constructed, the pressure control device is an auxiliary equipment of the system. While in the pre-ionization circuit, a three-electrode gas switch is selected as the discharge switch, and the principles of a trigger generator are given, the generator could both output high voltage and large current. Finally, the tests of electrical characteristics show that the two-electrode switch can sustain a peak current over 700 kA with a total volume of more than 200 kC transferred, in addition the switch life can be extended through the replacement of electrodes. Under the absolute pressure of 130 kPa and the charging voltage of 23 kV, the average breakdown delay of the three-electrode gas switch is 7.5 s, the delay jitter is 0.656 s, and the life test results of the pre-ionization switch show that the switch has 4000 times working life without replacing the graphite electrodes, and the total transferred charge exceeds 10 kC.
2014,
26: 045022.
doi: 10.11884/HPLPB201426.045022
Abstract:
The article analyzed the pulse voltage adding character of stacked Blumlein line generator. The parasitical shorted impedance is found to be the main factor affecting the adding efficiency. The parasitical inductance attenuates the flat top, and the attenuation extent depends on the stage number and the ratio between the shorted inductance and the transmission line inductance. The parasitical shorted capacitance slows the rise time, and the relative value depends on the stage number and the ratio between the shorted capacitance and the transmission line capacitance. The jitter of multiple switches leads to the slowing of the rise time and the fall time. Increasing the parasitical shorted impedance and decreasing the switch jitter are the best approaches to improve the adding efficiency and the output waveform.
The article analyzed the pulse voltage adding character of stacked Blumlein line generator. The parasitical shorted impedance is found to be the main factor affecting the adding efficiency. The parasitical inductance attenuates the flat top, and the attenuation extent depends on the stage number and the ratio between the shorted inductance and the transmission line inductance. The parasitical shorted capacitance slows the rise time, and the relative value depends on the stage number and the ratio between the shorted capacitance and the transmission line capacitance. The jitter of multiple switches leads to the slowing of the rise time and the fall time. Increasing the parasitical shorted impedance and decreasing the switch jitter are the best approaches to improve the adding efficiency and the output waveform.
2014,
26: 045023.
doi: 10.11884/HPLPB201426.045023
Abstract:
This paper focuses on the lifetime characteristics of pulse capacitors applied in millisecond pulse discharge through the establishment of the repetition-frequency lifetime test platform. The pulsed power charger adopts the mode of constant current charging and the output power is 30 kW with the voltage range between 0 kV and 12 kV. The switch of the pulse discharge circuit is a thyristor whose repetition frequency is up to 100 Hz. The discharge waveform can be adjusted by load resistance and load inductance. The effect of the charging time, hold time, intervals and repetition frequency on the lifetime characteristic of pulse capacitors can be sufficiently studied. Meanwhile, failure mechanisms of pulse capacitors in specific working conditions can be investigated.
This paper focuses on the lifetime characteristics of pulse capacitors applied in millisecond pulse discharge through the establishment of the repetition-frequency lifetime test platform. The pulsed power charger adopts the mode of constant current charging and the output power is 30 kW with the voltage range between 0 kV and 12 kV. The switch of the pulse discharge circuit is a thyristor whose repetition frequency is up to 100 Hz. The discharge waveform can be adjusted by load resistance and load inductance. The effect of the charging time, hold time, intervals and repetition frequency on the lifetime characteristic of pulse capacitors can be sufficiently studied. Meanwhile, failure mechanisms of pulse capacitors in specific working conditions can be investigated.
2014,
26: 045024.
doi: 10.11884/HPLPB201426.045024
Abstract:
New types of saturable pulse transformers (SPTs) with multiple batches of windings in parallel and coaxial cylindrical conductors are presented. The new SPT can be employed as the transformer and magnetic switch simultaneously for pulse capacitor or high-voltage pulse modulator of several hundred kV range. The SPT which has important features such as auto-resetting of core, high step-up ratio and low saturation inductance, achieves a compact integration of common transformer and magnetic switch. In the SPT, the physical suppression effect caused by reversed magnetic coupling mechanism among primary and secondary windings can reduce the saturation inductance of the SPT windings to a level lower than their structure inductances, which helps to achieve a magnetic switch with low saturation inductance. The proposed SPTs were applied in a high power pulse modulator based on a helical Blumlein pulse forming line (HBPFL). When the SPT played as a pulse transformer, the HBPFL could be charged to 200 kV. When the SPT played as a main magnetic switch of the HBPFL, it helped to form a quasi-square voltage pulse with amplitude of 180 kV, pulse duration of 130 ns, rise time of 60 ns. Furthermore, important new technologies and applications of SPT in 100 kV-range compact Marx generator and ns-range synchronization of multiple high-voltage pulses are proposed and demonstrated.
New types of saturable pulse transformers (SPTs) with multiple batches of windings in parallel and coaxial cylindrical conductors are presented. The new SPT can be employed as the transformer and magnetic switch simultaneously for pulse capacitor or high-voltage pulse modulator of several hundred kV range. The SPT which has important features such as auto-resetting of core, high step-up ratio and low saturation inductance, achieves a compact integration of common transformer and magnetic switch. In the SPT, the physical suppression effect caused by reversed magnetic coupling mechanism among primary and secondary windings can reduce the saturation inductance of the SPT windings to a level lower than their structure inductances, which helps to achieve a magnetic switch with low saturation inductance. The proposed SPTs were applied in a high power pulse modulator based on a helical Blumlein pulse forming line (HBPFL). When the SPT played as a pulse transformer, the HBPFL could be charged to 200 kV. When the SPT played as a main magnetic switch of the HBPFL, it helped to form a quasi-square voltage pulse with amplitude of 180 kV, pulse duration of 130 ns, rise time of 60 ns. Furthermore, important new technologies and applications of SPT in 100 kV-range compact Marx generator and ns-range synchronization of multiple high-voltage pulses are proposed and demonstrated.
2014,
26: 045025.
doi: 10.11884/HPLPB201426.045025
Abstract:
Stacked Blumlein pulse forming networks (PFNs) with photoconductive semiconductor switches can be used to drive flash X-ray diodes. In order to increase allowable running voltage of the device, factors affecting overvoltage on ceramic capacitors for PFNs during discharge are investigated. A voltage wave model of the stacked Blumlein PFNs is established, which incorporates parameters such as switch turn-on delay time, conductive resistance, and arbitrary resistor load, and the results are in accordance with that of PSpice circuit program. Moreover, factors influencing overvoltage coefficient are discussed, which shows that switch synchronization is key to overvoltage, the decreasing of diode impedance enhances the overvoltage coefficient, and too early collapse of diode impedance boosts the overvoltage up to－3 times the charge voltage.
Stacked Blumlein pulse forming networks (PFNs) with photoconductive semiconductor switches can be used to drive flash X-ray diodes. In order to increase allowable running voltage of the device, factors affecting overvoltage on ceramic capacitors for PFNs during discharge are investigated. A voltage wave model of the stacked Blumlein PFNs is established, which incorporates parameters such as switch turn-on delay time, conductive resistance, and arbitrary resistor load, and the results are in accordance with that of PSpice circuit program. Moreover, factors influencing overvoltage coefficient are discussed, which shows that switch synchronization is key to overvoltage, the decreasing of diode impedance enhances the overvoltage coefficient, and too early collapse of diode impedance boosts the overvoltage up to－3 times the charge voltage.
2014,
26: 045026.
doi: 10.11884/HPLPB201426.045026
Abstract:
A trigger device is designed for the hydrogen thyratron VE4141 according to the trigger method of hydrogen thyratrons used in the repetitive pulse-power system, which can output trigger pulses of repetition rate up to 10 kHz. In addition, it can receive optical and electric trigger signals. The pre-trigger pulse and main-trigger pulse are produced by fast-edge MOSFET switch. The former output amplitude is 500-1000 V; the latter amplitude is 1000-2000 V. Pulse delay time is about 500 ns and can be adjustable between the two trigger pulses. The trigger device can be easily applied to other high-power switches and pulse-power systems by adjusting some electronic components.
A trigger device is designed for the hydrogen thyratron VE4141 according to the trigger method of hydrogen thyratrons used in the repetitive pulse-power system, which can output trigger pulses of repetition rate up to 10 kHz. In addition, it can receive optical and electric trigger signals. The pre-trigger pulse and main-trigger pulse are produced by fast-edge MOSFET switch. The former output amplitude is 500-1000 V; the latter amplitude is 1000-2000 V. Pulse delay time is about 500 ns and can be adjustable between the two trigger pulses. The trigger device can be easily applied to other high-power switches and pulse-power systems by adjusting some electronic components.
2014,
26: 045027.
doi: 10.11884/HPLPB201426.045027
Abstract:
The discharge between two metalballs was used to simulate the transient process of the short-circuit load. The formula of inductor for overhead line and the circuit transient analysis were used to estimate the stray inductance. The calculation results accorded with simulation analysis results. Using the Monte Carlo analysis of various elements on the RCD (resistor, capacitor, and diode) snubber circuits and the gate drive circuits, the key elements influencing the transient voltage balancing of series connected IGBTs were found. They were Zener diodes of the gate drive circuits and capacitors for voltage balancing. The key elements of uniformity characteristics should be chosen to improve the reliability of the pulse power designed by the same topology.
The discharge between two metalballs was used to simulate the transient process of the short-circuit load. The formula of inductor for overhead line and the circuit transient analysis were used to estimate the stray inductance. The calculation results accorded with simulation analysis results. Using the Monte Carlo analysis of various elements on the RCD (resistor, capacitor, and diode) snubber circuits and the gate drive circuits, the key elements influencing the transient voltage balancing of series connected IGBTs were found. They were Zener diodes of the gate drive circuits and capacitors for voltage balancing. The key elements of uniformity characteristics should be chosen to improve the reliability of the pulse power designed by the same topology.
2014,
26: 045028.
doi: 10.11884/HPLPB201426.045028
Abstract:
For a high-current electron beam diode, in order to make reliable vacuum sealing, a ceramic vacuum interface was developed, following the compact and transportable demand: a novel radial insulation structure was designed and the hydrodynamic loading of the ceramic component was considered. For the insulation design, according to the theories of vacuum flashover and the rules for radial insulators, the electrostatic field along the ceramic surface was simulated by ANSYS package. By optimizing the outline of the anode and reshaping the shielding rings, the electric fields were well distributed and the field around the cathode triple junction was effectively controlled. Furthermore, the mechanic properties of the ceramic component were analyzed. Calculations show that the static and dynamic load for the ceramic interface is 4.8 MPa and 60 MPa, respectively. Finally, a vacuum diode with the ceramic interface was tested on a 200 ns high-voltage pulser, and the results show that the interface can work stably with the hold-off field of 44 kV/cm.
For a high-current electron beam diode, in order to make reliable vacuum sealing, a ceramic vacuum interface was developed, following the compact and transportable demand: a novel radial insulation structure was designed and the hydrodynamic loading of the ceramic component was considered. For the insulation design, according to the theories of vacuum flashover and the rules for radial insulators, the electrostatic field along the ceramic surface was simulated by ANSYS package. By optimizing the outline of the anode and reshaping the shielding rings, the electric fields were well distributed and the field around the cathode triple junction was effectively controlled. Furthermore, the mechanic properties of the ceramic component were analyzed. Calculations show that the static and dynamic load for the ceramic interface is 4.8 MPa and 60 MPa, respectively. Finally, a vacuum diode with the ceramic interface was tested on a 200 ns high-voltage pulser, and the results show that the interface can work stably with the hold-off field of 44 kV/cm.
2014,
26: 045029.
doi: 10.11884/HPLPB201426.045029
Abstract:
With an excitation of one-stage magnetic pulse compressor generator of 100 ns rise time and 150 ns duration, discharge mode of nanosecond-pulse discharges in an inhomogeneous electrical field in repetitive pulsed modes. Characteristics of nanosecond-pulse discharges are experimentally investigated by measuring their electrical parameters, images and taking their discharge photos. Results show that there were three typical discharge modes, i.e. corona, diffuse and spark discharges. The discharge modes were significantly influenced by the applied voltage, as the applied voltage increased the discharges experienced corona-to-diffuse-to-spark transition. With a fixed applied voltage, two discharge modes might simultaneously exist. Furthermore, experimental results on the effect of the pulse repetition frequency (PRF) show that, the excitation voltages of the diffuse discharges were slightly influenced by the PRF, but the excitation voltages of spark discharges decreased with the increase of the PRF. Thus, small PRF was beneficial for obtaining diffuse discharges in atmospheric-pressure air in a broad range of the applied voltage.
With an excitation of one-stage magnetic pulse compressor generator of 100 ns rise time and 150 ns duration, discharge mode of nanosecond-pulse discharges in an inhomogeneous electrical field in repetitive pulsed modes. Characteristics of nanosecond-pulse discharges are experimentally investigated by measuring their electrical parameters, images and taking their discharge photos. Results show that there were three typical discharge modes, i.e. corona, diffuse and spark discharges. The discharge modes were significantly influenced by the applied voltage, as the applied voltage increased the discharges experienced corona-to-diffuse-to-spark transition. With a fixed applied voltage, two discharge modes might simultaneously exist. Furthermore, experimental results on the effect of the pulse repetition frequency (PRF) show that, the excitation voltages of the diffuse discharges were slightly influenced by the PRF, but the excitation voltages of spark discharges decreased with the increase of the PRF. Thus, small PRF was beneficial for obtaining diffuse discharges in atmospheric-pressure air in a broad range of the applied voltage.
2014,
26: 045030.
doi: 10.11884/HPLPB201426.045030
Abstract:
A series of experiments were performed on Yang accelerator and PTS facility. We measured velocity histories of electrode panel with/without single crystal ［100］LiF windows by Doppler pins system(DPS, laser wavelength 1550 nm). As the driven panel is not disturbed until the first step of free-surface velocity profile, it is feasible to utilize half of free-surface velocity to estimate sample-window interface velocity. Analyzing apparent velocity profiles of the electrode panel with windows and free-surface, we obtained velocity correction and change of refractive index under magnetically driven quasi-isentropic compression to 50 GPa. Supposing half of free-surface velocity as true velocity, and through linear fit, we obtained the velocity correction factor. Additionally, the relationship between refractive index and density was calculated in the range of experimental conditions by a new procedure. The experiment data measured by photon Doppler velocimetry under 1550 nm laser wavelength are in close agreement with results from D.E. Fratanduono, Y. Ma, B.J. Jensen. The measured uncertainty in this work is as good as several shock experiments.
A series of experiments were performed on Yang accelerator and PTS facility. We measured velocity histories of electrode panel with/without single crystal ［100］LiF windows by Doppler pins system(DPS, laser wavelength 1550 nm). As the driven panel is not disturbed until the first step of free-surface velocity profile, it is feasible to utilize half of free-surface velocity to estimate sample-window interface velocity. Analyzing apparent velocity profiles of the electrode panel with windows and free-surface, we obtained velocity correction and change of refractive index under magnetically driven quasi-isentropic compression to 50 GPa. Supposing half of free-surface velocity as true velocity, and through linear fit, we obtained the velocity correction factor. Additionally, the relationship between refractive index and density was calculated in the range of experimental conditions by a new procedure. The experiment data measured by photon Doppler velocimetry under 1550 nm laser wavelength are in close agreement with results from D.E. Fratanduono, Y. Ma, B.J. Jensen. The measured uncertainty in this work is as good as several shock experiments.
2014,
26: 045031.
doi: 10.11884/HPLPB201426.045031
Abstract:
In this paper, an experimental investigation on pseudospark discharge behaviors was conducted under nanosecond pulse using a flexible discharge chamber. The influences of gas pressure, anode-cathode gap distance and hole diameter on the breakdown voltages were studied. The study results showed that the breakdown voltage decreased with the increasing of the pressure, gap distances and the hole diameter. In the end, an empirical formula was obtained. The attenuation coefficients were 0.76, 0.39 and 0.39, respectively.
In this paper, an experimental investigation on pseudospark discharge behaviors was conducted under nanosecond pulse using a flexible discharge chamber. The influences of gas pressure, anode-cathode gap distance and hole diameter on the breakdown voltages were studied. The study results showed that the breakdown voltage decreased with the increasing of the pressure, gap distances and the hole diameter. In the end, an empirical formula was obtained. The attenuation coefficients were 0.76, 0.39 and 0.39, respectively.
2014,
26: 045032.
doi: 10.11884/HPLPB201426.045032
Abstract:
A multi-stage stacked Blumlein line commutated by individual gas switches is designed. Comparative analysis of gas switch effect on the output waveform for the multi-stage Blumlein line is carried out. The switch jitter and electrical characteristics strongly influence the performance of the line and the stresses on the dielectric. The effects of switch jitter, inductance, the resistive decay during closure, and the closed-state resistance on the output pulse are explored for stacked Blumlein lines using SPICE simulations. Furthermore, the impact of switch operation on a four-stage stacked Blumlein line is studied experimentally.
A multi-stage stacked Blumlein line commutated by individual gas switches is designed. Comparative analysis of gas switch effect on the output waveform for the multi-stage Blumlein line is carried out. The switch jitter and electrical characteristics strongly influence the performance of the line and the stresses on the dielectric. The effects of switch jitter, inductance, the resistive decay during closure, and the closed-state resistance on the output pulse are explored for stacked Blumlein lines using SPICE simulations. Furthermore, the impact of switch operation on a four-stage stacked Blumlein line is studied experimentally.
2014,
26: 045033.
doi: 10.11884/HPLPB201426.045033
Abstract:
A portable 150 kV flash X-ray system based on fast rise time mini-Marx generator principle was designed in coaxial structure. The experimental results of a 10-stage 150 kV Mini-Marx generator and flash X-ray tube were described. With a flash X-ray tube integrated directly into the Mini-Marx generator as a load, the formed flash X-ray system generated a dose of 7.710-6 C/kg at 25 cm away for flash X-radiography. It penetrated aluminium 60 mm in thickness with source size 1-3 mm.
A portable 150 kV flash X-ray system based on fast rise time mini-Marx generator principle was designed in coaxial structure. The experimental results of a 10-stage 150 kV Mini-Marx generator and flash X-ray tube were described. With a flash X-ray tube integrated directly into the Mini-Marx generator as a load, the formed flash X-ray system generated a dose of 7.710-6 C/kg at 25 cm away for flash X-radiography. It penetrated aluminium 60 mm in thickness with source size 1-3 mm.
2014,
26: 045034.
doi: 10.11884/HPLPB201426.045034
Abstract:
A small tri-electrode gas switch and a small two-electrode gas switch are designed. Experiments for self-breakdown voltages of two-electrode gas switches and operating voltages of tri-electrode gas switches have been carried out in different conditions. The inductances of these switches have also been tested. The experimental results show the relation between self-breakdown voltages and gas pressures (0~0.30 MPa, relative) is nearly linear. The self-breakdown voltage of two-electrode gas switches with 11.9 mm gap and full of 0.25 MPa SF6 is up to 190 kV. The self-breakdown voltage by linear extrapolation can be up to 210 kV while the gap is 11.9 mm and inner SF6 pressure is 0.30 MPa. Operating voltages for tri-electrode gas switches with 11 mm total gap can be ranged from 90 kV to 200 kV by adjusting inner SF6 pressure from 0 to 0.30 MPa. Short circuit experiments reveal that the inductance of the two-electrode switch is about 20 nH and the one of the tri-electrode switch is about 22 nH. Thus the results tested for inductances are close to the values calculated.
A small tri-electrode gas switch and a small two-electrode gas switch are designed. Experiments for self-breakdown voltages of two-electrode gas switches and operating voltages of tri-electrode gas switches have been carried out in different conditions. The inductances of these switches have also been tested. The experimental results show the relation between self-breakdown voltages and gas pressures (0~0.30 MPa, relative) is nearly linear. The self-breakdown voltage of two-electrode gas switches with 11.9 mm gap and full of 0.25 MPa SF6 is up to 190 kV. The self-breakdown voltage by linear extrapolation can be up to 210 kV while the gap is 11.9 mm and inner SF6 pressure is 0.30 MPa. Operating voltages for tri-electrode gas switches with 11 mm total gap can be ranged from 90 kV to 200 kV by adjusting inner SF6 pressure from 0 to 0.30 MPa. Short circuit experiments reveal that the inductance of the two-electrode switch is about 20 nH and the one of the tri-electrode switch is about 22 nH. Thus the results tested for inductances are close to the values calculated.
2014,
26: 045035.
doi: 10.11884/HPLPB201426.045035
Abstract:
In order to study the spatio-temporal evolution of dielectric barrier discharge (DBD) excited by sub-microsecond pulse in atmospheric air, a high speed camera of intensified charge-coupled device (ICCD) which has a short exposure time of ns magnitude was used to photograph the process of the discharge, both the conditions of single and continuous (500 Hz) discharges were carefully studied in this work. On the condition of parallel board discharge excited by sub-microsecond pulse, it was found that discharge was not uniform at the early stage of the discharge. The discharge reached a uniform state while the current reached the peak point. Discharge during the falling time of the discharge was more uniform than that during the rising time of the discharge, the intensity of the discharge emission light and the discharge current coincided with each other. The existence of second discharge depended on the applied parameters such as repetitive frequency and voltage amplitude. Second discharge of the DBD was observed obviously in the single discharge mode and it was more uniform than the first discharge, but in the continuous discharge mode, generally the second discharge was too weak to be measured.
In order to study the spatio-temporal evolution of dielectric barrier discharge (DBD) excited by sub-microsecond pulse in atmospheric air, a high speed camera of intensified charge-coupled device (ICCD) which has a short exposure time of ns magnitude was used to photograph the process of the discharge, both the conditions of single and continuous (500 Hz) discharges were carefully studied in this work. On the condition of parallel board discharge excited by sub-microsecond pulse, it was found that discharge was not uniform at the early stage of the discharge. The discharge reached a uniform state while the current reached the peak point. Discharge during the falling time of the discharge was more uniform than that during the rising time of the discharge, the intensity of the discharge emission light and the discharge current coincided with each other. The existence of second discharge depended on the applied parameters such as repetitive frequency and voltage amplitude. Second discharge of the DBD was observed obviously in the single discharge mode and it was more uniform than the first discharge, but in the continuous discharge mode, generally the second discharge was too weak to be measured.
2014,
26: 045036.
doi: 10.11884/HPLPB201426.045036
Abstract:
Electric exploding opening switch(EEOS) is widely used in the inductive energy storage system, which has the features of simple structure, low cost, and strong ability of cutoff. Firstly the process of electric exploding wire was introduced. Its essence is a rapidly increased resistance, using its high impedance to achieve cutoff. Then a PSpice model, which simulated the resistor of the electric exploding opening switch, was created. A set of electric exploding opening switch experiments were designed. After that, the PSpice model simulation results were compared with the experimental results. The exploding moment and the voltage of the model were relatively close to the experimental results. The result shows that the model is reasonable. Finally, the deviation and limitation of this method were analyzed.
Electric exploding opening switch(EEOS) is widely used in the inductive energy storage system, which has the features of simple structure, low cost, and strong ability of cutoff. Firstly the process of electric exploding wire was introduced. Its essence is a rapidly increased resistance, using its high impedance to achieve cutoff. Then a PSpice model, which simulated the resistor of the electric exploding opening switch, was created. A set of electric exploding opening switch experiments were designed. After that, the PSpice model simulation results were compared with the experimental results. The exploding moment and the voltage of the model were relatively close to the experimental results. The result shows that the model is reasonable. Finally, the deviation and limitation of this method were analyzed.
2014,
26: 045037.
doi: 10.11884/HPLPB201426.045037
Abstract:
The single use of semiconductor switches in some special conditions was studied, especially in the cascade tests. The results show that the switch whose rated current is 30 mA can achieve a stable single discharge with a current of 10 kA. The discharge process was also analyzed. The switch experiences a complicated physical process from conduction to final damage. The circuit topology and the switch installation position have an effect on the output performance.
The single use of semiconductor switches in some special conditions was studied, especially in the cascade tests. The results show that the switch whose rated current is 30 mA can achieve a stable single discharge with a current of 10 kA. The discharge process was also analyzed. The switch experiences a complicated physical process from conduction to final damage. The circuit topology and the switch installation position have an effect on the output performance.
2014,
26: 045038.
doi: 10.11884/HPLPB201426.045038
Abstract:
Electromagnetic pulse emission produced by single mode plasma oscillations from Z pinches is theoretically studied. The angular distribution of electromagnetic pulse is similar with that of Cerenkov radiation when the phase velocity is superluminal, and the larger the phase velocity is, the more obvious the directional radiation; electromagnetic pulse with shorter wavelength has narrower distribution. The radiation power strongly depends plasma oscillation frequency of electrons and radius of plasma column.
Electromagnetic pulse emission produced by single mode plasma oscillations from Z pinches is theoretically studied. The angular distribution of electromagnetic pulse is similar with that of Cerenkov radiation when the phase velocity is superluminal, and the larger the phase velocity is, the more obvious the directional radiation; electromagnetic pulse with shorter wavelength has narrower distribution. The radiation power strongly depends plasma oscillation frequency of electrons and radius of plasma column.
2014,
26: 045039.
doi: 10.11884/HPLPB201426.045039
Abstract:
The breakdown delay processes of gas switches under combined voltages of DC and pulse voltages in the faster linear transformer driver (FLTD) are analyzed. A formula is presented to estimate the delay time. The three-electrode gas switches used in the present FLTD were preliminarily tested under combined voltages to investigate the breakdown characteristics by experiment. The experimental results indicate that, as applying the combined voltage of 70 kV DC voltage and 300 kV/30 ns fast pulse voltage, the delay time of switches under the combined voltages is smaller than that of normal trigger method. When gas switches are insulated by SF6, the delay time decreases by 17%-30%. While the delay time decreases by 50% with N2 as the dielectric. At the working coefficient of 55%, the jitter is less than 5 ns. Moreover, the estimated delay time is in close agreement with the experimental result.
The breakdown delay processes of gas switches under combined voltages of DC and pulse voltages in the faster linear transformer driver (FLTD) are analyzed. A formula is presented to estimate the delay time. The three-electrode gas switches used in the present FLTD were preliminarily tested under combined voltages to investigate the breakdown characteristics by experiment. The experimental results indicate that, as applying the combined voltage of 70 kV DC voltage and 300 kV/30 ns fast pulse voltage, the delay time of switches under the combined voltages is smaller than that of normal trigger method. When gas switches are insulated by SF6, the delay time decreases by 17%-30%. While the delay time decreases by 50% with N2 as the dielectric. At the working coefficient of 55%, the jitter is less than 5 ns. Moreover, the estimated delay time is in close agreement with the experimental result.
2014,
26: 045040.
doi: 10.11884/HPLPB201426.045040
Abstract:
Gouging will occur in the rails when the armature is moving at a high velocity in electromagnetic launch. The optimization of armature is designed in order to achieve high muzzle velocity without transition in the small caliber electromagnetic launching while researching the gouging with low energy. Optimization of the preload, size, plastic property, and contact area of the armature is presented in this paper. Some tests about these parameters have already been done. The model of the armature is thus determined, and high muzzle velocity is obtained with good electrical contact condition in launching.
Gouging will occur in the rails when the armature is moving at a high velocity in electromagnetic launch. The optimization of armature is designed in order to achieve high muzzle velocity without transition in the small caliber electromagnetic launching while researching the gouging with low energy. Optimization of the preload, size, plastic property, and contact area of the armature is presented in this paper. Some tests about these parameters have already been done. The model of the armature is thus determined, and high muzzle velocity is obtained with good electrical contact condition in launching.
2014,
26: 045041.
doi: 10.11884/HPLPB201426.045041
Abstract:
High frequency high turn ratio pulse transformer coupled solid state hard tube modulator was developed, the output voltage was 70 kV, and the output current was 12 A. The output pulse had two modes for 10 s and 200 s, when the output pulse was 10 s, the work frequency could adjust from 0 to 8 kHz; when the output pulse was 200 s, the working frequency could be adjusted from 0 to 400 Hz. The modulator was very compact, the overall size was 947 mm1127 mm1350 mm. The paper gave a brief overview of its components and working principle, focusing on the driver for IGBT solid switch, protection of the circuit and the power loss. Experiments were carried out to test the modulator , the pulse leading edge was 2.2 s, pulse trailing edge was 1.65 s, overshoot was smaller than 7%, the flat top was less than 1%, and the system was reliable and stable.
High frequency high turn ratio pulse transformer coupled solid state hard tube modulator was developed, the output voltage was 70 kV, and the output current was 12 A. The output pulse had two modes for 10 s and 200 s, when the output pulse was 10 s, the work frequency could adjust from 0 to 8 kHz; when the output pulse was 200 s, the working frequency could be adjusted from 0 to 400 Hz. The modulator was very compact, the overall size was 947 mm1127 mm1350 mm. The paper gave a brief overview of its components and working principle, focusing on the driver for IGBT solid switch, protection of the circuit and the power loss. Experiments were carried out to test the modulator , the pulse leading edge was 2.2 s, pulse trailing edge was 1.65 s, overshoot was smaller than 7%, the flat top was less than 1%, and the system was reliable and stable.
2014,
26: 045042.
doi: 10.11884/HPLPB201426.045042
Abstract:
Self-breakdown experiments were carried out with stainless steel (1Cr18Ni9Ti) electrode under different short current conditions. Electrode erosion and its effect on self breakdown were investigated by measuring various electrode mass loss, electrode surface roughness and breakdown voltage. The results are as follow: when current peak and periods increase, electrode mass loss rate and capacitance charge are linear, also the surface roughness and current peak are linear; when current peak and periods increase, the required breakdown numbers when self breakdown voltage comes to the peak and steady region decrease, also the self breakdown voltage and relative standard deviation in steady phase decrease; the distribution of self break down voltage probability follows Gauss distribution in all five current conditions.
Self-breakdown experiments were carried out with stainless steel (1Cr18Ni9Ti) electrode under different short current conditions. Electrode erosion and its effect on self breakdown were investigated by measuring various electrode mass loss, electrode surface roughness and breakdown voltage. The results are as follow: when current peak and periods increase, electrode mass loss rate and capacitance charge are linear, also the surface roughness and current peak are linear; when current peak and periods increase, the required breakdown numbers when self breakdown voltage comes to the peak and steady region decrease, also the self breakdown voltage and relative standard deviation in steady phase decrease; the distribution of self break down voltage probability follows Gauss distribution in all five current conditions.
2014,
26: 045043.
doi: 10.11884/HPLPB201426.045043
Abstract:
High power photoconductive semiconductor switches (PCSSs) were fabricated on V-doped semi-insulating 6H-SiC single crystal. The 6H-SiC PCSS were measured by applying a bias voltage from 1 kV to 14 kV. The triggered laser was a 355 nm pulse laser with an energy density of 150 J/mm2. The peak photocurrent shows an increasing trend with improving the applied voltage. The peak photocurrent running through the PCSS and the calculated on-state resistance are 185 A and about 22 respectively when the applied voltage reaches 14 kV, and the corresponding peak power is 2.59 MW.
High power photoconductive semiconductor switches (PCSSs) were fabricated on V-doped semi-insulating 6H-SiC single crystal. The 6H-SiC PCSS were measured by applying a bias voltage from 1 kV to 14 kV. The triggered laser was a 355 nm pulse laser with an energy density of 150 J/mm2. The peak photocurrent shows an increasing trend with improving the applied voltage. The peak photocurrent running through the PCSS and the calculated on-state resistance are 185 A and about 22 respectively when the applied voltage reaches 14 kV, and the corresponding peak power is 2.59 MW.
2014,
26: 045044.
doi: 10.11884/HPLPB201426.045044
Abstract:
To meet the requirement of some actual application experiments, a kind of high voltage microsecond pulse generator is developed. The output voltage amplitude is up to 30 kV with a minimum rise time of 300 ns and a pulse duration of 0.5 s. Some tests show that the output characteristics of the generator are determined by the load, and the input voltage and trigger pulse width can change the output pulse. Experiments by a point-to-point gas discharge are used to show the characteristics, the discharge modes can be changed by adjusting the pulse frequency and gap spacing. Different discharge modes can be distinguished by studying the variation of the pulse output with the load. Finally, the generator is successfully used for the excitation of atmospheric-pressure dielectric barrier discharge.
To meet the requirement of some actual application experiments, a kind of high voltage microsecond pulse generator is developed. The output voltage amplitude is up to 30 kV with a minimum rise time of 300 ns and a pulse duration of 0.5 s. Some tests show that the output characteristics of the generator are determined by the load, and the input voltage and trigger pulse width can change the output pulse. Experiments by a point-to-point gas discharge are used to show the characteristics, the discharge modes can be changed by adjusting the pulse frequency and gap spacing. Different discharge modes can be distinguished by studying the variation of the pulse output with the load. Finally, the generator is successfully used for the excitation of atmospheric-pressure dielectric barrier discharge.
2014,
26: 045045.
doi: 10.11884/HPLPB201426.045045
Abstract:
Current distribution between X-pinches and current-return rods was studied, considering the effect of mutual influence between different branches. In the experiment of current distribution between an X-pinch and a copper current-return rod, the current in the X-pinch is roughly the same as that in the current-return rod, which reflects that current division depends not only on the characteristic of the wires/rods, but also on the features of the other parts of the loops. In the experiment of current distribution between two X-pinches, the current flowing through the two X-pinches does not depend on the diameter or material of the X-pinch, confirming that current division has something to do with the parts of the parallel circuits other than X-pinches. The amplitude of current flowing in the X-pinch farther from the polyformaldehyde isolation rod is always slightly higher than the other, indicating the influence of the mutual inductance between the branch circuits.
Current distribution between X-pinches and current-return rods was studied, considering the effect of mutual influence between different branches. In the experiment of current distribution between an X-pinch and a copper current-return rod, the current in the X-pinch is roughly the same as that in the current-return rod, which reflects that current division depends not only on the characteristic of the wires/rods, but also on the features of the other parts of the loops. In the experiment of current distribution between two X-pinches, the current flowing through the two X-pinches does not depend on the diameter or material of the X-pinch, confirming that current division has something to do with the parts of the parallel circuits other than X-pinches. The amplitude of current flowing in the X-pinch farther from the polyformaldehyde isolation rod is always slightly higher than the other, indicating the influence of the mutual inductance between the branch circuits.
2014,
26: 045046.
doi: 10.11884/HPLPB201426.045046
Abstract:
This paper presents a flexible electrical insulating composite film-DMD. Through an analysis of the film structure, a series equivalent circuit model is designed. By using this model, dielectric constant and strength are solved in not oil impregnated and oil impregnated DMD film and formulae are given. The formulae show that the dielectric constants increase obviously after impregnation and the dielectric strength of impregnated DMD film is higher than that of the not oil impregnated DMD film. The electric field strength on polyester material increases and that on impregnated material decreases with the increase of the oil dielectric constant. Due to the high dielectric strength of polyester material, the dielectric strength of the transmission line is increased.
This paper presents a flexible electrical insulating composite film-DMD. Through an analysis of the film structure, a series equivalent circuit model is designed. By using this model, dielectric constant and strength are solved in not oil impregnated and oil impregnated DMD film and formulae are given. The formulae show that the dielectric constants increase obviously after impregnation and the dielectric strength of impregnated DMD film is higher than that of the not oil impregnated DMD film. The electric field strength on polyester material increases and that on impregnated material decreases with the increase of the oil dielectric constant. Due to the high dielectric strength of polyester material, the dielectric strength of the transmission line is increased.
2014,
26: 045047.
doi: 10.11884/HPLPB201426.045047
Abstract:
The B-dot probe is one of the most common measurements of velocity for armatures in the bore of a railgun. In this paper, we analyzed the principle of B-dot probe induced voltage, and found that the rate of change of armature current is the inaccuracy factor in locating moving armature by B-dot probe. Armature currents with different dI/dt were set in the Matlab simulation of locating moving armature by B-dot probe. The results show that the error in locating moving armature by B-dot probe is positively correlated to the absolute value of dI/dt, and is negatively correlated to the product of armature current and armature velocity if dI/dts are equal. According to the results, we performed a further simulation of inaccuracy in B-dot-probe measurement of armature velocity, and its results could be divided into three types. Real current data were utilized to replace the ideal current in the simulation, the results of which well matched the ideal one. In short, the error in measuring armature velocity by B-dot probe is small if dI/dts are similar, and the error is large if dI/dts are different.
The B-dot probe is one of the most common measurements of velocity for armatures in the bore of a railgun. In this paper, we analyzed the principle of B-dot probe induced voltage, and found that the rate of change of armature current is the inaccuracy factor in locating moving armature by B-dot probe. Armature currents with different dI/dt were set in the Matlab simulation of locating moving armature by B-dot probe. The results show that the error in locating moving armature by B-dot probe is positively correlated to the absolute value of dI/dt, and is negatively correlated to the product of armature current and armature velocity if dI/dts are equal. According to the results, we performed a further simulation of inaccuracy in B-dot-probe measurement of armature velocity, and its results could be divided into three types. Real current data were utilized to replace the ideal current in the simulation, the results of which well matched the ideal one. In short, the error in measuring armature velocity by B-dot probe is small if dI/dts are similar, and the error is large if dI/dts are different.
2014,
26: 045048.
doi: 10.11884/HPLPB201426.045048
Abstract:
The solid state modulator based on high ratio pulse transformer which utilizes nouniformity secondary to output 70 kV for 200 s is discussed. The stray capacitances of the annular pulse transformer are systematically analyzed. The relationship between static stray capacitances and equivalent stray capacitances when secondary is uniformity distribution is also presented. Furthermore, the analytic expression of the equivalent stray capacitances when secondary is nouniformity distribution is discussed. The experimental result shows that the equivalent stray capacitance reduces 30% when secondary is nouniformity distribution. The high voltage pulse with 2.5 s rise time and 4.3% overshoot can be achieved when the ratio of pulse transformers with nouniformity distributed secondary is 1∶100.
The solid state modulator based on high ratio pulse transformer which utilizes nouniformity secondary to output 70 kV for 200 s is discussed. The stray capacitances of the annular pulse transformer are systematically analyzed. The relationship between static stray capacitances and equivalent stray capacitances when secondary is uniformity distribution is also presented. Furthermore, the analytic expression of the equivalent stray capacitances when secondary is nouniformity distribution is discussed. The experimental result shows that the equivalent stray capacitance reduces 30% when secondary is nouniformity distribution. The high voltage pulse with 2.5 s rise time and 4.3% overshoot can be achieved when the ratio of pulse transformers with nouniformity distributed secondary is 1∶100.
2014,
26: 045049.
doi: 10.11884/HPLPB201426.045049
Abstract:
The characteristics of grooved insulator flashover under pulsed voltage are discussed in this paper. The groove widths are determined by the secondary electron emission trajectory. The experiments results show that the flashover voltages increased while the insulator samples with 0.05 mm, 0.1 mm, or 0.7 mm wide grooves were used and the biggest voltage multiple was 1.4. The samples with 1 mm wide grooves had the same flashover voltage level as the flat ones. It is concluded that proper grooves design could increase the insulator flashover level by preventing the development of the secondary electron emission avalanche. Mechanism of inhibition was analyzed with calculation of electric field strength on the surface of insulator. Wider grooves, would trap the electrons and narrower ones would inhibit the motion of the initial electrons. Comparing the samples surface micrograms, a conclusion was given that the surface micro-flaw would drop the insulator flashover level.
The characteristics of grooved insulator flashover under pulsed voltage are discussed in this paper. The groove widths are determined by the secondary electron emission trajectory. The experiments results show that the flashover voltages increased while the insulator samples with 0.05 mm, 0.1 mm, or 0.7 mm wide grooves were used and the biggest voltage multiple was 1.4. The samples with 1 mm wide grooves had the same flashover voltage level as the flat ones. It is concluded that proper grooves design could increase the insulator flashover level by preventing the development of the secondary electron emission avalanche. Mechanism of inhibition was analyzed with calculation of electric field strength on the surface of insulator. Wider grooves, would trap the electrons and narrower ones would inhibit the motion of the initial electrons. Comparing the samples surface micrograms, a conclusion was given that the surface micro-flaw would drop the insulator flashover level.
2014,
26: 045050.
doi: 10.11884/HPLPB201426.045050
Abstract:
The local ohmic heating dominated dynamic ablation of Z-pinch wire-array is investigated numerically in 2D geometry using FOI-PERFECT code. Mass ablation rate, precursor current and ablation time are analyzed quantitatively to investigate the effects of initial wire plasma diameter and wire number on the ablation of wire-array. Numerical results demonstrate that the increase of wire number and/or initial wire plasma diameter leads to the increase of mass ablation rate and the decrease of precursor current and ablation time. This conclusion agrees with the simulation works of other authors.
The local ohmic heating dominated dynamic ablation of Z-pinch wire-array is investigated numerically in 2D geometry using FOI-PERFECT code. Mass ablation rate, precursor current and ablation time are analyzed quantitatively to investigate the effects of initial wire plasma diameter and wire number on the ablation of wire-array. Numerical results demonstrate that the increase of wire number and/or initial wire plasma diameter leads to the increase of mass ablation rate and the decrease of precursor current and ablation time. This conclusion agrees with the simulation works of other authors.
2014,
26: 045101.
doi: 10.11884/HPLPB201426.045101
Abstract:
The triple-pulse linear induced accelerator (LIA) based on high voltage rectifier diodes needs an external reset system, for the diodes cut off the prepulse of the PFL charging which is used to reset the cavity cores of the single-pulse LIA. This paper describes the physics and circuit designs of the external reset unit, and introduces the layout of the whole reset system which includes other more units for charging, triggering and control. As a result, the system can reset the whole 92 cavities of the triple-pulse LIA steadily, quickly and fully.
The triple-pulse linear induced accelerator (LIA) based on high voltage rectifier diodes needs an external reset system, for the diodes cut off the prepulse of the PFL charging which is used to reset the cavity cores of the single-pulse LIA. This paper describes the physics and circuit designs of the external reset unit, and introduces the layout of the whole reset system which includes other more units for charging, triggering and control. As a result, the system can reset the whole 92 cavities of the triple-pulse LIA steadily, quickly and fully.
2014,
26: 045102.
doi: 10.11884/HPLPB201426.045102
Abstract:
The characteristics of photoconductive semiconductor switches (PCSSs), based on laser diodes, are introduced in this paper, including the scheme and some finals in the experiments. This kind of switch may be used in the dielectric wall accelerator (DWA). The pulsed laser triggering the PCSS has the wavelength, full width at half maximum (FWHM), rise-time, and peak power of 905 nm, 20 ns, 3.1 ns and 90 W, respectively. The switch we used in the experiment is an opposed-contact GaAs photoconductive semiconductor switch. The electrode gap is 5 mm, and when the bias pulsed voltage is between 15 kV and 22 kV, the switch works in the nonlinear mode. The measured least closing resistance is 4.1 , root mean square (RMS) jitter is less than 1 ns, and the average life-time of PCSSs is approximately 200 shots under 18 kV bias pulsed voltage.
The characteristics of photoconductive semiconductor switches (PCSSs), based on laser diodes, are introduced in this paper, including the scheme and some finals in the experiments. This kind of switch may be used in the dielectric wall accelerator (DWA). The pulsed laser triggering the PCSS has the wavelength, full width at half maximum (FWHM), rise-time, and peak power of 905 nm, 20 ns, 3.1 ns and 90 W, respectively. The switch we used in the experiment is an opposed-contact GaAs photoconductive semiconductor switch. The electrode gap is 5 mm, and when the bias pulsed voltage is between 15 kV and 22 kV, the switch works in the nonlinear mode. The measured least closing resistance is 4.1 , root mean square (RMS) jitter is less than 1 ns, and the average life-time of PCSSs is approximately 200 shots under 18 kV bias pulsed voltage.
2014,
26: 045103.
doi: 10.11884/HPLPB201426.045103
Abstract:
Beam monitors sensitive to the beams azimuthal B-dot field (sometimes referred as B-dots) are widely used to measure the displacement of beam centroid, as the beam generates a dipole term of the azimuthal magnetic field. Basing on the principle of the proportionality between the deflection angle and the difference of axial B field between the axially symmetrical positions, the axial B-dot probe has a potential use for beam deflection angle measurement. A calibration stand was built to test and improve the beam angle monitor, which was fabricated as a PCB structure. Meanwhile, simulations using the CST MWS codes were performed, demonstrating a good agreement with test results and giving some advices to suppress the disturbance of position deviation of the beam. Both the simulations and the experiments show that the axial B-dot monitor can be successfully used to measure the beam tilt directly.
Beam monitors sensitive to the beams azimuthal B-dot field (sometimes referred as B-dots) are widely used to measure the displacement of beam centroid, as the beam generates a dipole term of the azimuthal magnetic field. Basing on the principle of the proportionality between the deflection angle and the difference of axial B field between the axially symmetrical positions, the axial B-dot probe has a potential use for beam deflection angle measurement. A calibration stand was built to test and improve the beam angle monitor, which was fabricated as a PCB structure. Meanwhile, simulations using the CST MWS codes were performed, demonstrating a good agreement with test results and giving some advices to suppress the disturbance of position deviation of the beam. Both the simulations and the experiments show that the axial B-dot monitor can be successfully used to measure the beam tilt directly.
