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RSS2016 Vol. 28, No. 05
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2016,
28: 050101.
doi: 10.11884/HPLPB201628.050101
Abstract:
A high average power linearly polarized chirped pulse amplification (CPA) system is reported, which comprises of a fully fiberized fiber amplifier chain and a transmission grating pulse compressor. Before compression, the output average power of 425 W is achieved with corresponding optical to optical efficiency of 81%, polarization extinction ratio of 13 dB and near-transform-limited beam quality. After compression, femtosecond pulses with average power of 300 W, duration of 315 fs and peak power of 12 MW are achieved. This is the highest average power ever reported in linearly polarized fiber CPA system.
A high average power linearly polarized chirped pulse amplification (CPA) system is reported, which comprises of a fully fiberized fiber amplifier chain and a transmission grating pulse compressor. Before compression, the output average power of 425 W is achieved with corresponding optical to optical efficiency of 81%, polarization extinction ratio of 13 dB and near-transform-limited beam quality. After compression, femtosecond pulses with average power of 300 W, duration of 315 fs and peak power of 12 MW are achieved. This is the highest average power ever reported in linearly polarized fiber CPA system.
2016,
28: 050102.
doi: 10.11884/HPLPB201628.050102
Abstract:
The design of a linear-transformer-driver (LTD) accelerator for wire-array Z-pinch experiments was presented. The accelerator comprises 6 modules in parallel, and each of the module has 8 series 0.8 MA LTD cavities in a voltage adder configuration. A prototype cavity was built, employing a novel single-pulse-trigger method, as well as charging and trigger inductors. A full circuit modeling for the accelerator was conducted. Simulation result shows that a current pulse rising to 5.2 MA in 91 ns (10%-90%) can be delivered to the wire-array load, which is 1.2 cm in initial radius and 1mg in mass. The max kinetic energy of the load is 78kJ, which is 11.7% of the electric energy stored in the capacitors. This accelerator is supposed to enable a radiation energy efficiency of 20%-30%, providing a high efficient facility for research on fast Z-pinch and technologies for rep-rately operated accelerators.
The design of a linear-transformer-driver (LTD) accelerator for wire-array Z-pinch experiments was presented. The accelerator comprises 6 modules in parallel, and each of the module has 8 series 0.8 MA LTD cavities in a voltage adder configuration. A prototype cavity was built, employing a novel single-pulse-trigger method, as well as charging and trigger inductors. A full circuit modeling for the accelerator was conducted. Simulation result shows that a current pulse rising to 5.2 MA in 91 ns (10%-90%) can be delivered to the wire-array load, which is 1.2 cm in initial radius and 1mg in mass. The max kinetic energy of the load is 78kJ, which is 11.7% of the electric energy stored in the capacitors. This accelerator is supposed to enable a radiation energy efficiency of 20%-30%, providing a high efficient facility for research on fast Z-pinch and technologies for rep-rately operated accelerators.
2016,
28: 050201.
doi: 10.11884/HPLPB201628.050201
Abstract:
The rod-pinch diode has been widely applied to flash radiography due to its merits of high brightness and spatial resolution. Many efforts have been committed to improve its dose while keeping the spot size small. Some factors affecting the rod pinch diode dose are reviewed, including the dose spatial distribution, the process on coupling energy to diode, the efficiency of electrons pinched to rod tip, the diode configuration, and so on. Experimental results are reported that the radiation dose of diode with LaB6 cathode increases by 12% at least compared to that of diode with graphite cathode. Some means to improve dose are analyzed.
The rod-pinch diode has been widely applied to flash radiography due to its merits of high brightness and spatial resolution. Many efforts have been committed to improve its dose while keeping the spot size small. Some factors affecting the rod pinch diode dose are reviewed, including the dose spatial distribution, the process on coupling energy to diode, the efficiency of electrons pinched to rod tip, the diode configuration, and so on. Experimental results are reported that the radiation dose of diode with LaB6 cathode increases by 12% at least compared to that of diode with graphite cathode. Some means to improve dose are analyzed.
2016,
28: 051001.
doi: 10.11884/HPLPB201628.051001
Abstract:
To resolve the problem that the background pixels in an object model induce localization errors in target tracking, a new target model establishing method based on HRBW is put forward. The fuzzy membership degree based on target/background histogram log-likelihood ratio was introduced in the kernel histogram for reducing the localization errors in target tracking produced by background pixels. The method transforms only the target model but not the target candidate model and decreases the probability of target model features that are prominent in the background. The results in experiments prove that the proposed algorithm not only accelerated the convergence, but also enhanced anti-interference ability.
To resolve the problem that the background pixels in an object model induce localization errors in target tracking, a new target model establishing method based on HRBW is put forward. The fuzzy membership degree based on target/background histogram log-likelihood ratio was introduced in the kernel histogram for reducing the localization errors in target tracking produced by background pixels. The method transforms only the target model but not the target candidate model and decreases the probability of target model features that are prominent in the background. The results in experiments prove that the proposed algorithm not only accelerated the convergence, but also enhanced anti-interference ability.
2016,
28: 051002.
doi: 10.11884/HPLPB201628.051002
Abstract:
According to the different kinds of morphology features, 3D grid models of mitigated pits were built, and effects of different kinds of mitigated pits models on transport of laser beam (351 nm) was studied by using scalar diffraction theory and Fast Fourier Transform (FFT) methods. The results indicate that the off-axis downstream intensification of different kinds of mitigated pits, including conic, parabolic and Gaussian, pits, mainly relies on the depth of the mitigated pit. For the off-axis intensification, the maximum intensity increases with deepening depth, and the location of the maximum intensity approaches the output surface of optics with increasing pit depth, and is far away from the output surface of optics with the increasing diameter of mitigated pits. In addition, when the depth and diameter of different kinds of mitigation pits are equal, the parabolic mitigated pits can be the best choice for mitigated morphology. The results of this research indicate that the downstream intensification, which is induced by the mitigated damage pits, can be suppressed by controlling the morphology features of mitigated pits.
According to the different kinds of morphology features, 3D grid models of mitigated pits were built, and effects of different kinds of mitigated pits models on transport of laser beam (351 nm) was studied by using scalar diffraction theory and Fast Fourier Transform (FFT) methods. The results indicate that the off-axis downstream intensification of different kinds of mitigated pits, including conic, parabolic and Gaussian, pits, mainly relies on the depth of the mitigated pit. For the off-axis intensification, the maximum intensity increases with deepening depth, and the location of the maximum intensity approaches the output surface of optics with increasing pit depth, and is far away from the output surface of optics with the increasing diameter of mitigated pits. In addition, when the depth and diameter of different kinds of mitigation pits are equal, the parabolic mitigated pits can be the best choice for mitigated morphology. The results of this research indicate that the downstream intensification, which is induced by the mitigated damage pits, can be suppressed by controlling the morphology features of mitigated pits.
2016,
28: 052001.
doi: 10.11884/HPLPB201628.052001
Abstract:
Laser fusion ignition requires strict control over laser facility, target quality and diagnosis precision in experiments. With the experiments approaching ignition regime, the requirement of precision is increased. In the precision experiments, the target design should determine not only the parameters such as laser energy, target dimensions and gas density, et al, but also the uncertainty indexes of these important parameters. Hence it is important for target design to obtain the uncertainty indexes of parameters. This paper investigates the method to effectively obtain the uncertainty indexes in target design. The method is presented by theoretical analysis based on linear approximation, and takes into account the difference of the control abilities of different parameters. This paper also shows an example of the application of this method to a gas-filled target design. It is indicated that the parameters uncertainty indexes can be effectively specified in target design by this method with greatly reduced workload.
Laser fusion ignition requires strict control over laser facility, target quality and diagnosis precision in experiments. With the experiments approaching ignition regime, the requirement of precision is increased. In the precision experiments, the target design should determine not only the parameters such as laser energy, target dimensions and gas density, et al, but also the uncertainty indexes of these important parameters. Hence it is important for target design to obtain the uncertainty indexes of parameters. This paper investigates the method to effectively obtain the uncertainty indexes in target design. The method is presented by theoretical analysis based on linear approximation, and takes into account the difference of the control abilities of different parameters. This paper also shows an example of the application of this method to a gas-filled target design. It is indicated that the parameters uncertainty indexes can be effectively specified in target design by this method with greatly reduced workload.
2016,
28: 052002.
doi: 10.11884/HPLPB201628.052002
Abstract:
The absorption characteristics of the plane electromagnetic wave in magnetized plasma is studied by using the equivalent input impedance method. The result shows that the absorption characteristics can be primarily affected by the electron numerical density, the collision frequency, and the magnetic intensity. Different modes of electromagnetic wave are discussed and the variation of absorption property with changing parameter is given. A finite element simulation result is obtained by taking equivalent permittivity of plasma stabs in. This work explains operation parameter chosen principle and is useful for engineering application.
The absorption characteristics of the plane electromagnetic wave in magnetized plasma is studied by using the equivalent input impedance method. The result shows that the absorption characteristics can be primarily affected by the electron numerical density, the collision frequency, and the magnetic intensity. Different modes of electromagnetic wave are discussed and the variation of absorption property with changing parameter is given. A finite element simulation result is obtained by taking equivalent permittivity of plasma stabs in. This work explains operation parameter chosen principle and is useful for engineering application.
2016,
28: 053001.
doi: 10.11884/HPLPB201628.053001
Abstract:
In order to overcome the pulse shortening problem caused by the microwave leakage inside the device, the anode of the oversized backward wave oscillator was specially designed. In the PIC simulation, oversized backward wave oscillators with different anode structure were studied under the beam voltage of 800 kV and the current of 7 kA. By adding the microwave absorbing materials in the anode, the influence of the leaked microwave on the microwave output could be significantly reduced, and the pulse duration increased. The experimental result shows that the pulse duration at the frequency of 8.58 GHz increased obviously from 70 ns to 110 ns when the efficiency was 30%.
In order to overcome the pulse shortening problem caused by the microwave leakage inside the device, the anode of the oversized backward wave oscillator was specially designed. In the PIC simulation, oversized backward wave oscillators with different anode structure were studied under the beam voltage of 800 kV and the current of 7 kA. By adding the microwave absorbing materials in the anode, the influence of the leaked microwave on the microwave output could be significantly reduced, and the pulse duration increased. The experimental result shows that the pulse duration at the frequency of 8.58 GHz increased obviously from 70 ns to 110 ns when the efficiency was 30%.
2016,
28: 053002.
doi: 10.11884/HPLPB201628.053002
Abstract:
The measurement layout of the high power microwave in radiation field, which includes measuring the distance, the integral angle range, and the equality of E-plane and H-plane, is researched with numerical methods. The influence of measurement layout on the experimental results in radiation field is studied by the X-band magnetron and 20 dB horn as well as 680 mm horn with an input power of 407 kW. And the measurement layout is validated by the X-band 9.3 GHz and 9.7 GHz relativistic back wave oscillator. Experimental results show that accurate results can be got by the integral angle control if the equality of E-plane and H-plane is well, even though the measurement distance does not satisfy the far-field condition.
The measurement layout of the high power microwave in radiation field, which includes measuring the distance, the integral angle range, and the equality of E-plane and H-plane, is researched with numerical methods. The influence of measurement layout on the experimental results in radiation field is studied by the X-band magnetron and 20 dB horn as well as 680 mm horn with an input power of 407 kW. And the measurement layout is validated by the X-band 9.3 GHz and 9.7 GHz relativistic back wave oscillator. Experimental results show that accurate results can be got by the integral angle control if the equality of E-plane and H-plane is well, even though the measurement distance does not satisfy the far-field condition.
2016,
28: 053003.
doi: 10.11884/HPLPB201628.053003
Abstract:
In the paper, the heat dissipation of high power microwave tubes collector is calculated by using Euler two-phase model and the boiling model. Based on the electron beam sink rule, the distribution of heat source in collector material and cooling water is obtained. Then, the collector temperature is calculated by using the CFD software under electron beam duration of 45 ns, a repetitive frequency of 50 Hz and an average power of 27 kW. The effect of flow velocity of the cooling water on heat dissipation is analyzed. The results indicate that the max temperature of the collector is beyond the material melting point when the cooling water flow velocity is 1.5 m/s, and the collector will be damaged after some time. At the top of the heat dissipation, the convection heat transfer is about 71.7% of the total heat transfer. The quenching heat transfer is 28.1%, and the phase transition heat transfer is 0.2%. When the cooling water flow velocity is less than 5 m/s or more than 10 m/s, the maximum temperature of the collector will decrease quickly as the flow velocity increases; when the cooling water flow velocity is 5-10 m/s, the temperature will decrease slowly as the flow velocity increases. For the electron beam condition in the paper, it is requested that the cooling water flow velocity is 5 m/s at least for collector safety.
In the paper, the heat dissipation of high power microwave tubes collector is calculated by using Euler two-phase model and the boiling model. Based on the electron beam sink rule, the distribution of heat source in collector material and cooling water is obtained. Then, the collector temperature is calculated by using the CFD software under electron beam duration of 45 ns, a repetitive frequency of 50 Hz and an average power of 27 kW. The effect of flow velocity of the cooling water on heat dissipation is analyzed. The results indicate that the max temperature of the collector is beyond the material melting point when the cooling water flow velocity is 1.5 m/s, and the collector will be damaged after some time. At the top of the heat dissipation, the convection heat transfer is about 71.7% of the total heat transfer. The quenching heat transfer is 28.1%, and the phase transition heat transfer is 0.2%. When the cooling water flow velocity is less than 5 m/s or more than 10 m/s, the maximum temperature of the collector will decrease quickly as the flow velocity increases; when the cooling water flow velocity is 5-10 m/s, the temperature will decrease slowly as the flow velocity increases. For the electron beam condition in the paper, it is requested that the cooling water flow velocity is 5 m/s at least for collector safety.
2016,
28: 053004.
doi: 10.11884/HPLPB201628.053004
Abstract:
A novel tuning method based on aggressive space mapping (ASM) and genetic algorithm (GA) is presented in this paper. The method is applied to microwave filters with different phase shift effects at I/O ports. The tuning direction and magnitude are predicted by ASM. The phase shift effect can be calculated by GA, then the coarse model parameters are extracted by the Cauchy method. The fine model is constructed by the commercial FEM simulation software HFSS, and the coarse model is the equivalent circuit. A sixth order cross-coupled filter tuning example is used to verify the new method and the validity of the method is proved. The filter meets specifications less than four iterations.
A novel tuning method based on aggressive space mapping (ASM) and genetic algorithm (GA) is presented in this paper. The method is applied to microwave filters with different phase shift effects at I/O ports. The tuning direction and magnitude are predicted by ASM. The phase shift effect can be calculated by GA, then the coarse model parameters are extracted by the Cauchy method. The fine model is constructed by the commercial FEM simulation software HFSS, and the coarse model is the equivalent circuit. A sixth order cross-coupled filter tuning example is used to verify the new method and the validity of the method is proved. The filter meets specifications less than four iterations.
2016,
28: 053005.
doi: 10.11884/HPLPB201628.053005
Abstract:
A novel carbon/carbon composite cathode with carbon fibers perpendicular to the surface is developed and used in the relativistic klystron amplifier(RKA). The experimental results show that the field enhanced on the whisker is the main ignition of the explosive emission. RKA can steadily run at the frequency of 25 Hz with an output microwave power more than 1 GW, a pulse duration beyond 100 ns and a current density of 3.82 kA/cm2. The parameters of the carbon/carbon composite cathode such as start-up speed, current delay time and impedance characteristic still need to be studied in the future.
A novel carbon/carbon composite cathode with carbon fibers perpendicular to the surface is developed and used in the relativistic klystron amplifier(RKA). The experimental results show that the field enhanced on the whisker is the main ignition of the explosive emission. RKA can steadily run at the frequency of 25 Hz with an output microwave power more than 1 GW, a pulse duration beyond 100 ns and a current density of 3.82 kA/cm2. The parameters of the carbon/carbon composite cathode such as start-up speed, current delay time and impedance characteristic still need to be studied in the future.
2016,
28: 053006.
doi: 10.11884/HPLPB201628.053006
Abstract:
To generate wideband high power microwave with relatively high central frequency, a quarter wave switched oscillator filled with transformer oil as insulating medium is investigated in this paper. Firstly, the structure of this oscillator is introduced. Secondly its characteristic impedance is calculated. Thirdly, the voltage capability is estimated by the simulation results of static electric field distribution and experimental data of the breakdown electric field of the transformer oil. And then the transient performance of the oscillator is simulated by utilizing CST software. The influence of the breakdown position and down-time of the voltage between the switch gap on the peak voltage and central frequency is also investigated. Finally, the experimental result of the oscillator connected to a short helical antenna with a directivity of 3 is introduced. It is shown that the breakdown voltage of the oscillator reaches -322 kV when the rise time of the charging voltage is about 15 ns. The center frequency of the radiated electric field is about 360 MHz with a 3 dB bandwidth of about 22%, while the radiation factor is about 170 kV.
To generate wideband high power microwave with relatively high central frequency, a quarter wave switched oscillator filled with transformer oil as insulating medium is investigated in this paper. Firstly, the structure of this oscillator is introduced. Secondly its characteristic impedance is calculated. Thirdly, the voltage capability is estimated by the simulation results of static electric field distribution and experimental data of the breakdown electric field of the transformer oil. And then the transient performance of the oscillator is simulated by utilizing CST software. The influence of the breakdown position and down-time of the voltage between the switch gap on the peak voltage and central frequency is also investigated. Finally, the experimental result of the oscillator connected to a short helical antenna with a directivity of 3 is introduced. It is shown that the breakdown voltage of the oscillator reaches -322 kV when the rise time of the charging voltage is about 15 ns. The center frequency of the radiated electric field is about 360 MHz with a 3 dB bandwidth of about 22%, while the radiation factor is about 170 kV.
2016,
28: 053007.
doi: 10.11884/HPLPB201628.053007
Abstract:
A high power RF pulse formation system was developed based on ferrite magnetic nonlinear transmission lines with cross-linking elements. The system consisted of a pulse forming line, nonlinear transmission lines and a matched high power load or combined dipole antenna. The pulse forming line was based on a 100 kV high power source and a high power microwave coaxial cable. The pulse width of the output waveform of the pulse forming line was 60 ns and the output voltage of pulse was 35 kV. The output high power pulse was fed into nonlinear transmission. The nonlinear transmission lines connected to the matched load produced a RF pulse of 31 kV peak to peak voltage amplitude and with a 308 MHz centre frequency and 13% 3-dB bandwidth. A 380 MHz centre frequency and 12% 3-dB bandwidth were obtained when the nonlinear transmission lines were connected to a combined dipole antenna.
A high power RF pulse formation system was developed based on ferrite magnetic nonlinear transmission lines with cross-linking elements. The system consisted of a pulse forming line, nonlinear transmission lines and a matched high power load or combined dipole antenna. The pulse forming line was based on a 100 kV high power source and a high power microwave coaxial cable. The pulse width of the output waveform of the pulse forming line was 60 ns and the output voltage of pulse was 35 kV. The output high power pulse was fed into nonlinear transmission. The nonlinear transmission lines connected to the matched load produced a RF pulse of 31 kV peak to peak voltage amplitude and with a 308 MHz centre frequency and 13% 3-dB bandwidth. A 380 MHz centre frequency and 12% 3-dB bandwidth were obtained when the nonlinear transmission lines were connected to a combined dipole antenna.
2016,
28: 053201.
doi: 10.11884/HPLPB201628.053201
Abstract:
Based on principle of power synthesis of sparse array, mathematical model of spatial power combining is established. Relation between cross angle of beams and synthesis efficiency on aimed point from two antenna nodes is derived. Furthermore, the setting principle of sampling interval is analyzed for simulation experiment. Energy distributions of the useful points under different cross angles were simulated. Simulation shows that if distance between the antenna nodes and aimed point are equal, and frequency, polarization and antenna type are the same, synthesis efficiency relies on the cross angles of beams, shape and density on the useful points accumulation area also rely on the cross angles of beams.
Based on principle of power synthesis of sparse array, mathematical model of spatial power combining is established. Relation between cross angle of beams and synthesis efficiency on aimed point from two antenna nodes is derived. Furthermore, the setting principle of sampling interval is analyzed for simulation experiment. Energy distributions of the useful points under different cross angles were simulated. Simulation shows that if distance between the antenna nodes and aimed point are equal, and frequency, polarization and antenna type are the same, synthesis efficiency relies on the cross angles of beams, shape and density on the useful points accumulation area also rely on the cross angles of beams.
2016,
28: 053202.
doi: 10.11884/HPLPB201628.053202
Abstract:
This paper addresses the existence detection of blanket jamming based on fractal features in fractional Fourier transform (FRFT) domain. Firstly, the existences of fractal features of three typical jamming signals are analyzed, and box dimension and information dimension are employed to describe fractal features quantitatively. Then the differences of fractal characteristics between blanket jamming and white Gaussian noise (WGN) in FRFT domain are described, and a detector to detect the jamming is proposed. At last, simulations are done to verify that the algorithm is effective preferable.
This paper addresses the existence detection of blanket jamming based on fractal features in fractional Fourier transform (FRFT) domain. Firstly, the existences of fractal features of three typical jamming signals are analyzed, and box dimension and information dimension are employed to describe fractal features quantitatively. Then the differences of fractal characteristics between blanket jamming and white Gaussian noise (WGN) in FRFT domain are described, and a detector to detect the jamming is proposed. At last, simulations are done to verify that the algorithm is effective preferable.
2016,
28: 054001.
doi: 10.11884/HPLPB201628.054001
Abstract:
The beam optic characteristics of the neutral beam ion source affects the neutral beam injection power. With theoretical calculation and experimental scanning, study on the variation of half width of extraction beam with perveance is carried out. Theoretically, the 1/e half-width of extraction beam at the calorimetric target is obtained with IGUN program simulating trajectory of element beam to the 3 electrodes extraction accelerator on HL-2A device and beam geometry optic program calculating the superposition of every element beam. Experimentally, when the discharge gas is deuterium, the extraction voltage is scanned separately for arc current at 200 A, 300 A and 400 A, and the 1/e half-width of extraction beam is obtained with temperature rise curves measured by thermal couples on the calorimetric target. Theoretical and experimental results show that with the perveance increasing, the beam half width decreases first and then increases gradually. The optimum perveance value keeps almost the same for different beam current by theoretical result, while for arc current at 200, 300 and 400 A, the optimum perveances are 1.6, 1.7 and 1.85 P separately by experimental result.
The beam optic characteristics of the neutral beam ion source affects the neutral beam injection power. With theoretical calculation and experimental scanning, study on the variation of half width of extraction beam with perveance is carried out. Theoretically, the 1/e half-width of extraction beam at the calorimetric target is obtained with IGUN program simulating trajectory of element beam to the 3 electrodes extraction accelerator on HL-2A device and beam geometry optic program calculating the superposition of every element beam. Experimentally, when the discharge gas is deuterium, the extraction voltage is scanned separately for arc current at 200 A, 300 A and 400 A, and the 1/e half-width of extraction beam is obtained with temperature rise curves measured by thermal couples on the calorimetric target. Theoretical and experimental results show that with the perveance increasing, the beam half width decreases first and then increases gradually. The optimum perveance value keeps almost the same for different beam current by theoretical result, while for arc current at 200, 300 and 400 A, the optimum perveances are 1.6, 1.7 and 1.85 P separately by experimental result.
2016,
28: 054002.
doi: 10.11884/HPLPB201628.054002
Abstract:
In order to detect the chemical weapon contained in the unmarked ammunition, a fast neutron chemical weapon detection system based on associated particle technology (APT) was developed. The detection system included an associated particle DT neutron source, an particle detector, a detector and shielding as well as an electronics signal acquiring and processing system. Four types of chemical weapons including sarin, VX reagent, mustard gas and adamsite reagent were measured by the detection system. The characteristic gamma spectra induced by 14 MeV neutron were obtained. According to the analysis of the spectra, the characteristic gamma peaks of phosphorus (P), fluorine (F), sulfur (S) and chlorine (Cl) were clearly measured except arsenic (As). These results showed the APT could reach the goal of nondestructive detecting chemical weapon.
In order to detect the chemical weapon contained in the unmarked ammunition, a fast neutron chemical weapon detection system based on associated particle technology (APT) was developed. The detection system included an associated particle DT neutron source, an particle detector, a detector and shielding as well as an electronics signal acquiring and processing system. Four types of chemical weapons including sarin, VX reagent, mustard gas and adamsite reagent were measured by the detection system. The characteristic gamma spectra induced by 14 MeV neutron were obtained. According to the analysis of the spectra, the characteristic gamma peaks of phosphorus (P), fluorine (F), sulfur (S) and chlorine (Cl) were clearly measured except arsenic (As). These results showed the APT could reach the goal of nondestructive detecting chemical weapon.
2016,
28: 054003.
doi: 10.11884/HPLPB201628.054003
Abstract:
To improve the reconstruction quality of flash X-ray radiography containing noises, an image reconstruction algorithm based on ML-EM (maximum likelihood-expectation maximum) for radiography is studied. According to the characters of low signal to noise ratio and smoothness in pieces, proper filter restraining the noises during the processing of reconstruction is adopted, the result reconstructed by this algorithm is less influenced by noises and preserves the boundary character of the object. Simulation indicates that ML-EM reconstruction algorithm based on noises constraint can give satisfactory results.
To improve the reconstruction quality of flash X-ray radiography containing noises, an image reconstruction algorithm based on ML-EM (maximum likelihood-expectation maximum) for radiography is studied. According to the characters of low signal to noise ratio and smoothness in pieces, proper filter restraining the noises during the processing of reconstruction is adopted, the result reconstructed by this algorithm is less influenced by noises and preserves the boundary character of the object. Simulation indicates that ML-EM reconstruction algorithm based on noises constraint can give satisfactory results.
2016,
28: 054101.
doi: 10.11884/HPLPB201628.054101
Abstract:
Preparation course and wire properties of ultra-fine W wire with modulation diameter were studied by using the preparation device, laser-diffraction device for on-line diameter measurement, and the SEM and mechanical property test. It was showed that alternate of electrolyzation voltage and zero voltage could be a feasible way for preparing continuous W wire with modulation diameter shape. The modulation shape of W wire was obvious in the system of (100-500) gL-1NaOH electrolyte with 1.4 V and 1.6 V voltage. Corresponding modulation shape could be achieved in NaOH electrolyte of concentration less than 500 gL-1, when electrolyzation voltage was high. The relationship of direct ratio between loss weight of tungsten wire and the product of current intensity and electrolyzation time in the preparing process of ultra-fine tungsten wire by electrochemical corrosion technology was deduced and examined. The value of direct ratio could be 5.3510-5gC-1 in some certain condition. The thick segment diameter was 12.2 m, the thin segment diameter 9.8 m, and the ratio of diameter reduction was about 20% with experiment parameters of electrolyte density of 200 gL-1, a voltage of 2.0 V and an electrolysis time of 3 s. Fracture force of such modulation W wire was 0.2883 N.
Preparation course and wire properties of ultra-fine W wire with modulation diameter were studied by using the preparation device, laser-diffraction device for on-line diameter measurement, and the SEM and mechanical property test. It was showed that alternate of electrolyzation voltage and zero voltage could be a feasible way for preparing continuous W wire with modulation diameter shape. The modulation shape of W wire was obvious in the system of (100-500) gL-1NaOH electrolyte with 1.4 V and 1.6 V voltage. Corresponding modulation shape could be achieved in NaOH electrolyte of concentration less than 500 gL-1, when electrolyzation voltage was high. The relationship of direct ratio between loss weight of tungsten wire and the product of current intensity and electrolyzation time in the preparing process of ultra-fine tungsten wire by electrochemical corrosion technology was deduced and examined. The value of direct ratio could be 5.3510-5gC-1 in some certain condition. The thick segment diameter was 12.2 m, the thin segment diameter 9.8 m, and the ratio of diameter reduction was about 20% with experiment parameters of electrolyte density of 200 gL-1, a voltage of 2.0 V and an electrolysis time of 3 s. Fracture force of such modulation W wire was 0.2883 N.
2016,
28: 055001.
doi: 10.11884/HPLPB201628.055001
Abstract:
In this paper, a microsecond pulse driven helium plasma jet was well characterized by different electrode configurations and discharge parameters. The influence of dielectric material diameter (3 mm, 5 mm and 8 mm), different electrode configuration and frequencies on the discharge properties and optical emissions were studied. The results showed that the length of plasma jet plume reduced when dielectric material diameter was increased. The breakdown voltage and discharge current were the smallest with a diameter of 8 mm, while the intensities of N2, N+2, O and OH species reached their peaks. The discharge current, consume power and energy were the highest when the diameter was 5 mm. Whats more, larger discharge current, consume power and emission intensity were observed with sharp tip needle electrode configuration. Higher pulse repetition frequency led to lower breakdown voltage and longer length.
In this paper, a microsecond pulse driven helium plasma jet was well characterized by different electrode configurations and discharge parameters. The influence of dielectric material diameter (3 mm, 5 mm and 8 mm), different electrode configuration and frequencies on the discharge properties and optical emissions were studied. The results showed that the length of plasma jet plume reduced when dielectric material diameter was increased. The breakdown voltage and discharge current were the smallest with a diameter of 8 mm, while the intensities of N2, N+2, O and OH species reached their peaks. The discharge current, consume power and energy were the highest when the diameter was 5 mm. Whats more, larger discharge current, consume power and emission intensity were observed with sharp tip needle electrode configuration. Higher pulse repetition frequency led to lower breakdown voltage and longer length.
2016,
28: 055002.
doi: 10.11884/HPLPB201628.055002
Abstract:
Based on fast switching power MOSFET, by using a high repetitive frequency integrated drive chip and a high efficiency magnetic coupling structure, the compact high power repetitive frequency generator is designed. This generator is constructed by four stages LTD and tested for a single shot and repetitive operation at 2 MHz. Near-rectangle waveforms are obtained on the resistance of 200 , with an output voltage of 2.27 kV, a rise time of 6.8 ns, a pulse width of 91 ns, and a fall time of 20 ns. The overall system voltage efficiency is up to 95%. The generator can be used for research of repetitive frequency pulse effect because of its compactness, stableness and modularity.
Based on fast switching power MOSFET, by using a high repetitive frequency integrated drive chip and a high efficiency magnetic coupling structure, the compact high power repetitive frequency generator is designed. This generator is constructed by four stages LTD and tested for a single shot and repetitive operation at 2 MHz. Near-rectangle waveforms are obtained on the resistance of 200 , with an output voltage of 2.27 kV, a rise time of 6.8 ns, a pulse width of 91 ns, and a fall time of 20 ns. The overall system voltage efficiency is up to 95%. The generator can be used for research of repetitive frequency pulse effect because of its compactness, stableness and modularity.
2016,
28: 055003.
doi: 10.11884/HPLPB201628.055003
Abstract:
A series of current pulse shaping experiments have been carried out on the Primary Test Stand(PTS). More than 5 MA peak current were successfully achieved on the load with a rise time of 600 ns. The typical rise time of PTS machine is 90 ns with about 10 MA peak current under short pulse mode, which means all 24 modules discharged simultaneously. By distributing the laser trigger target time of 12 laser beams logically and adjusting the status of the pulse output switch, longer rise time pulse can be obtained on the PTS facility. According to the required pulse shaping, whole circuit simulation will be used to calculate the trigger time of each laser triggered gas switch and the status of the pulse output switches. The experimental results indicate that the rise time of the current is determined by the time difference between the first and last triggered gas switches, normally it should be less than the transition time of the two neighboring modules. In order to trigger the laser triggered gas switch, sufficient laser power is needed to be sent into the gap of the gas switch, the gas switch press and voltage difference on the two electrodes also affects the triggering of the gas switch. The voltage difference is determined by the switchs transition time. The study and experiments of the pulse shaping on PTS show the adaptable ability of the PTS for offering different waveform of mega ampere current pulse for different research purpose.
A series of current pulse shaping experiments have been carried out on the Primary Test Stand(PTS). More than 5 MA peak current were successfully achieved on the load with a rise time of 600 ns. The typical rise time of PTS machine is 90 ns with about 10 MA peak current under short pulse mode, which means all 24 modules discharged simultaneously. By distributing the laser trigger target time of 12 laser beams logically and adjusting the status of the pulse output switch, longer rise time pulse can be obtained on the PTS facility. According to the required pulse shaping, whole circuit simulation will be used to calculate the trigger time of each laser triggered gas switch and the status of the pulse output switches. The experimental results indicate that the rise time of the current is determined by the time difference between the first and last triggered gas switches, normally it should be less than the transition time of the two neighboring modules. In order to trigger the laser triggered gas switch, sufficient laser power is needed to be sent into the gap of the gas switch, the gas switch press and voltage difference on the two electrodes also affects the triggering of the gas switch. The voltage difference is determined by the switchs transition time. The study and experiments of the pulse shaping on PTS show the adaptable ability of the PTS for offering different waveform of mega ampere current pulse for different research purpose.
2016,
28: 055004.
doi: 10.11884/HPLPB201628.055004
Abstract:
It is important to study initial discharge for researching operating process in gas spark gap. The whole initial discharge process in gas spark gap was simulated in this paper by PIC-DSMC code. The evolutions of electron density distribution and ion density distribution were obtained, the electric field distribution in the gap was analyzed, and the process from electron emission to plasma channel was presented. Finally, the gas spark gap discharge experiment was performed with high speed camera. This is basis for further researching on physics mechanism of the gas spark gap.
It is important to study initial discharge for researching operating process in gas spark gap. The whole initial discharge process in gas spark gap was simulated in this paper by PIC-DSMC code. The evolutions of electron density distribution and ion density distribution were obtained, the electric field distribution in the gap was analyzed, and the process from electron emission to plasma channel was presented. Finally, the gas spark gap discharge experiment was performed with high speed camera. This is basis for further researching on physics mechanism of the gas spark gap.
2016,
28: 055005.
doi: 10.11884/HPLPB201628.055005
Abstract:
An all solid-state high-voltage rectangular pulse generator is proposed. This generator consists of a Marx generator, a pulse forming line (PFL) and a magnetic switch (MS). As a power supply, the Marx generator discharges to the PFL through an inductor. The inductor should cooperate with MS since it influences the discharging process directly and determines the volt-second product of the MS and the pre-pulse over the load. The MS saturates at exactly the moment the discharging process ends. PFL discharges to the matched resistor load through the saturated MS and a high voltage rectangular pulse is obtained over the load. The designs of the Marx generator and the MS are introduced in this paper. Experiments under a single shot and repetitive frequency of 5 kHz are carried out. PSpice simulations with a simplified model of MS are carried out to verify the experimental results. The experimental result matches well with the simulation results. A rectangular pulse with 12.5 kV voltage amplitude, 250 A current amplitude, 46-ns rise-time, 220 ns pulse-width is obtained over the 50 resistor load.
An all solid-state high-voltage rectangular pulse generator is proposed. This generator consists of a Marx generator, a pulse forming line (PFL) and a magnetic switch (MS). As a power supply, the Marx generator discharges to the PFL through an inductor. The inductor should cooperate with MS since it influences the discharging process directly and determines the volt-second product of the MS and the pre-pulse over the load. The MS saturates at exactly the moment the discharging process ends. PFL discharges to the matched resistor load through the saturated MS and a high voltage rectangular pulse is obtained over the load. The designs of the Marx generator and the MS are introduced in this paper. Experiments under a single shot and repetitive frequency of 5 kHz are carried out. PSpice simulations with a simplified model of MS are carried out to verify the experimental results. The experimental result matches well with the simulation results. A rectangular pulse with 12.5 kV voltage amplitude, 250 A current amplitude, 46-ns rise-time, 220 ns pulse-width is obtained over the 50 resistor load.
2016,
28: 055006.
doi: 10.11884/HPLPB201628.055006
Abstract:
Though the electrical insulation properties of epoxy resin are very excellent, the surface of epoxy insulator is charged easily and the charge is hard to decay. When the charge density accumulates to a level, it would lead to a part discharge or a surface flashover. In order to improve the surface flashover voltage of epoxy resin, ATH inorganic fillers with 1m particle size are used to change the surface properties of the epoxy resin. Samples with different mass fraction ATH fillers are prepared, which are 0% (pure epoxy), 20%, 40%, 60%, 80% and 100%. The pulsed electro-acoustic method is employed to study charge decay properties of epoxy composites. Several kinds of composites are experimented after the application of 10 kV/mm or 30 kV/mm polarization electrical field respectively. The results show that the charge decay constant of epoxy composites is related to the inorganic fillers mass fraction of the epoxy resin and the charge quantities of the samples.
Though the electrical insulation properties of epoxy resin are very excellent, the surface of epoxy insulator is charged easily and the charge is hard to decay. When the charge density accumulates to a level, it would lead to a part discharge or a surface flashover. In order to improve the surface flashover voltage of epoxy resin, ATH inorganic fillers with 1m particle size are used to change the surface properties of the epoxy resin. Samples with different mass fraction ATH fillers are prepared, which are 0% (pure epoxy), 20%, 40%, 60%, 80% and 100%. The pulsed electro-acoustic method is employed to study charge decay properties of epoxy composites. Several kinds of composites are experimented after the application of 10 kV/mm or 30 kV/mm polarization electrical field respectively. The results show that the charge decay constant of epoxy composites is related to the inorganic fillers mass fraction of the epoxy resin and the charge quantities of the samples.
2016,
28: 055007.
doi: 10.11884/HPLPB201628.055007
Abstract:
The on-line calibration of capacitive voltage dividers used in low impedance pulse forming lines is discussed, and a parallel inductance is proposed to compensate the capacitive load of the forming line. Due to the low impedance of the forming line, the calibrated waveform will lack flattop if a short pulse square wave generator is used, and the calibrated waveform will have poor signal noise ratio if low voltage sine wave generator is used. By using a parallel-connected inductance, a parallel resonance circuit is formed. Low distortion and high voltage can be obtained from the amplifier. The method can be used in on-line calibration of microsecond capacitive voltage dividers in forming line voltage measurement.
The on-line calibration of capacitive voltage dividers used in low impedance pulse forming lines is discussed, and a parallel inductance is proposed to compensate the capacitive load of the forming line. Due to the low impedance of the forming line, the calibrated waveform will lack flattop if a short pulse square wave generator is used, and the calibrated waveform will have poor signal noise ratio if low voltage sine wave generator is used. By using a parallel-connected inductance, a parallel resonance circuit is formed. Low distortion and high voltage can be obtained from the amplifier. The method can be used in on-line calibration of microsecond capacitive voltage dividers in forming line voltage measurement.
2016,
28: 055008.
doi: 10.11884/HPLPB201628.055008
Abstract:
In order to overcome disadvantages of pulse generator for electrostatic precipitators (ESP), such as pulse stretching, residual voltage accumulation of capacitors and oscillating voltage of ESP, an appropriate solution with an auxiliary switch inversely connected to the charging diode in parallel is put forward. This article analyzes the principle of the pulse generator for ESP at length, and provides the theory of the selection of critical parameters. The simulation analysis and low-voltage experimental results confirm the validity of the solution. The improvement of pulse generator for ESP is conductive to further improve the collection efficiency and energy utilization.
In order to overcome disadvantages of pulse generator for electrostatic precipitators (ESP), such as pulse stretching, residual voltage accumulation of capacitors and oscillating voltage of ESP, an appropriate solution with an auxiliary switch inversely connected to the charging diode in parallel is put forward. This article analyzes the principle of the pulse generator for ESP at length, and provides the theory of the selection of critical parameters. The simulation analysis and low-voltage experimental results confirm the validity of the solution. The improvement of pulse generator for ESP is conductive to further improve the collection efficiency and energy utilization.
2016,
28: 055009.
doi: 10.11884/HPLPB201628.055009
Abstract:
An experiment platform of laser illumination together with pulsed voltage excitation was built. The vacuum surface flashover performance of an angled-insulator was studied. The results show that the performance of +45 insulator is better than that of －45 insulator when UV laser (266 nm) or visible laser (532 nm) illuminates at either the cathode triple point or the sample center. The effect of the UV laser illumination on the cathode triple point is prominent, and it is important to shield this area against UV light in the design of vacuum insulators.
An experiment platform of laser illumination together with pulsed voltage excitation was built. The vacuum surface flashover performance of an angled-insulator was studied. The results show that the performance of +45 insulator is better than that of －45 insulator when UV laser (266 nm) or visible laser (532 nm) illuminates at either the cathode triple point or the sample center. The effect of the UV laser illumination on the cathode triple point is prominent, and it is important to shield this area against UV light in the design of vacuum insulators.
2016,
28: 055010.
doi: 10.11884/HPLPB201628.055010
Abstract:
Based on PTS accelerator, combined with theoretical calculation and circuit simulation, magnetic driven loading experiments design method and sample loading path control techniques were developed and improved. With the excellent output characteristics of the platform PTS, quasi-isentropic compression of oxygen-free high-conductivity copper(OFHC) was realized. In these experiments, with the existing wave profile measuring technique, we measured the interface velocity history of two different thickness OFHC samples/LiF window material successfully. Combined with the Lagrange analysis and inverse integral method, we have successfully acquired the quasi-isentropic compression reference line of copper up to 100 GPa, which agrees well with that in SESAME dataset.
Based on PTS accelerator, combined with theoretical calculation and circuit simulation, magnetic driven loading experiments design method and sample loading path control techniques were developed and improved. With the excellent output characteristics of the platform PTS, quasi-isentropic compression of oxygen-free high-conductivity copper(OFHC) was realized. In these experiments, with the existing wave profile measuring technique, we measured the interface velocity history of two different thickness OFHC samples/LiF window material successfully. Combined with the Lagrange analysis and inverse integral method, we have successfully acquired the quasi-isentropic compression reference line of copper up to 100 GPa, which agrees well with that in SESAME dataset.
2016,
28: 055101.
doi: 10.11884/HPLPB201628.055101
Abstract:
In order to meet the requirement of crack region segmentation, based on the characteristics of oil sedimentary core industrial CT image, the level set segmentation algorithm is improved. Firstly, a median filter is used for denoising, and a C-V model is adopted to get the coarse image segmentation result. The background area and the core area are separated, and the contour of the core is obtained. Secondly, the gray level of the background region is adjusted, so that it is equal to the average gray level of the core area. Finally, the Region-Scalable Fitting (RSF) model is adopted to precisely segment the crack region. For the core image of Gauss noise pollution, the method of non-local mean with the neighborhood window is used, and then the improved level set algorithm is used. The experimental results show that the improved level set algorithm for image segmentation is effective for oil rock core CT image.
In order to meet the requirement of crack region segmentation, based on the characteristics of oil sedimentary core industrial CT image, the level set segmentation algorithm is improved. Firstly, a median filter is used for denoising, and a C-V model is adopted to get the coarse image segmentation result. The background area and the core area are separated, and the contour of the core is obtained. Secondly, the gray level of the background region is adjusted, so that it is equal to the average gray level of the core area. Finally, the Region-Scalable Fitting (RSF) model is adopted to precisely segment the crack region. For the core image of Gauss noise pollution, the method of non-local mean with the neighborhood window is used, and then the improved level set algorithm is used. The experimental results show that the improved level set algorithm for image segmentation is effective for oil rock core CT image.
2016,
28: 055102.
doi: 10.11884/HPLPB201628.055102
Abstract:
This paper demonstrates a fiber link based timing distribution with femtosecond precision. The output femtosecond laser pulse train from a passively mode-locked fiber laser serves as master clock, which is distributed over a 2 km single mode fiber link. A balanced optical cross-correlator (BOC) is used to monitor the accumulated timing error, which is actively compensated by a local fiber stretcher and a step motor. The standard deviation of the residual timing error is less than 1.1 fs over 2 h observation, and the time stability is better than 10-18.
This paper demonstrates a fiber link based timing distribution with femtosecond precision. The output femtosecond laser pulse train from a passively mode-locked fiber laser serves as master clock, which is distributed over a 2 km single mode fiber link. A balanced optical cross-correlator (BOC) is used to monitor the accumulated timing error, which is actively compensated by a local fiber stretcher and a step motor. The standard deviation of the residual timing error is less than 1.1 fs over 2 h observation, and the time stability is better than 10-18.
2016,
28: 055103.
doi: 10.11884/HPLPB201628.055103
Abstract:
Plasma characteristics are key parameters of ion source. The characteristics of plasma in high current laser ion source are diagnosed by optic emission spectroscopy and an ICCD camera. The plasma is produced by a quadruplicated frequency Nd: YAG laser irradiating Cu target. The laser energy density is about 108 W/cm2, and the duration time is 15 ns. The plasma expansion progress is captured by the ICCD camera, which shows the expansion velocity is about 1 cm/s. Meantime the plasma emission spectra are measured by a spectrograph, which are mostly Cu Ⅰ spectra from Cu atoms and some weakly Cu Ⅱ spectra from Cu+ ions. Electron temperatures are got by Boltzmann plot and they are about 1 eV. Electron densities are got by Stark broadening and they are about 1016 cm-3.
Plasma characteristics are key parameters of ion source. The characteristics of plasma in high current laser ion source are diagnosed by optic emission spectroscopy and an ICCD camera. The plasma is produced by a quadruplicated frequency Nd: YAG laser irradiating Cu target. The laser energy density is about 108 W/cm2, and the duration time is 15 ns. The plasma expansion progress is captured by the ICCD camera, which shows the expansion velocity is about 1 cm/s. Meantime the plasma emission spectra are measured by a spectrograph, which are mostly Cu Ⅰ spectra from Cu atoms and some weakly Cu Ⅱ spectra from Cu+ ions. Electron temperatures are got by Boltzmann plot and they are about 1 eV. Electron densities are got by Stark broadening and they are about 1016 cm-3.
2016,
28: 055104.
doi: 10.11884/HPLPB201628.055104
Abstract:
An on-line electron beam energy measurement technique was designed for the beam characteristics of linear induction accelerator. In this technique the slice average energy of the electron beam was measured by beam position monitors and magnetic analyzer, which can avoid the errors in beam bunch sampling as well as the influence of measurement process on the beam and can achieve the on-line measurement. This method was applied in the measurement of electron energy for a high current linear induction accelerator and the slice average energy time curve was obtained, with the energy measurement uncertainty of 0.177 MeV and the energy spread measurement uncertainty of 0.39%.
An on-line electron beam energy measurement technique was designed for the beam characteristics of linear induction accelerator. In this technique the slice average energy of the electron beam was measured by beam position monitors and magnetic analyzer, which can avoid the errors in beam bunch sampling as well as the influence of measurement process on the beam and can achieve the on-line measurement. This method was applied in the measurement of electron energy for a high current linear induction accelerator and the slice average energy time curve was obtained, with the energy measurement uncertainty of 0.177 MeV and the energy spread measurement uncertainty of 0.39%.
2016,
28: 056001.
doi: 10.11884/HPLPB201628.056001
Abstract:
A numerical simulation method is built based on the point reactor kinetic equations to study the impact of scattering neutrons on a super-prompt critical system, and its correctness is validated by pulse experiment on CFBR-Ⅱ reactor. The analysis and calculation show that kinetic effects of the scattered neutrons in the super-prompt critical state include that the reactivity increases, the pulse wave is broadened, and the fission yield is enlarged by scattering neutrons. The numerical simulation method can be used to forecast the kinetic effect of scattered neutrons produced by objects out of the pulse reactor, and it is valuable to upgrade the nuclear safety of a pulse reactor.
A numerical simulation method is built based on the point reactor kinetic equations to study the impact of scattering neutrons on a super-prompt critical system, and its correctness is validated by pulse experiment on CFBR-Ⅱ reactor. The analysis and calculation show that kinetic effects of the scattered neutrons in the super-prompt critical state include that the reactivity increases, the pulse wave is broadened, and the fission yield is enlarged by scattering neutrons. The numerical simulation method can be used to forecast the kinetic effect of scattered neutrons produced by objects out of the pulse reactor, and it is valuable to upgrade the nuclear safety of a pulse reactor.
2016,
28: 056002.
doi: 10.11884/HPLPB201628.056002
Abstract:
Assuming that the Ti-H plasma generated by vacuum arc ion source using Ti-H solid solution was a non-equilibrium two-temperature plasma. The dissociation of hydrogen and the ionization of atomic particles were described by Culdberg-Waage dissociation equation and Saha ionization equation, respectively. Combining plasma atomic emission spectra and plasmas charge quasi-neutral condition, the electron temperature, heavy particle temperature and particle number density were calculated. Then the thermodynamic parameters including mass density, enthalpy and specific heat were described. Under different electron densities, the changes of each parameter with the ratio of the electron temperature to heavy particle temperature named were studied. The calculated results showed: under the same electron number density, with the growth of , in addition of the hydrogen molecules number density, the electron temperature and the number densities of all single-atomic particles were all almost not changed. When the electron density was high, single-atomic particles were dominant in the plasma and the thermodynamic parameters were controlled by them. On the other hand, with low electron density, with the growth of , hydrogen molecules in the plasma became dominant gradually, and the variation of the thermodynamic parameters exhibited the same trend.
Assuming that the Ti-H plasma generated by vacuum arc ion source using Ti-H solid solution was a non-equilibrium two-temperature plasma. The dissociation of hydrogen and the ionization of atomic particles were described by Culdberg-Waage dissociation equation and Saha ionization equation, respectively. Combining plasma atomic emission spectra and plasmas charge quasi-neutral condition, the electron temperature, heavy particle temperature and particle number density were calculated. Then the thermodynamic parameters including mass density, enthalpy and specific heat were described. Under different electron densities, the changes of each parameter with the ratio of the electron temperature to heavy particle temperature named were studied. The calculated results showed: under the same electron number density, with the growth of , in addition of the hydrogen molecules number density, the electron temperature and the number densities of all single-atomic particles were all almost not changed. When the electron density was high, single-atomic particles were dominant in the plasma and the thermodynamic parameters were controlled by them. On the other hand, with low electron density, with the growth of , hydrogen molecules in the plasma became dominant gradually, and the variation of the thermodynamic parameters exhibited the same trend.
2016,
28: 059001.
doi: 10.11884/HPLPB201628.059001
Abstract:
The electron irradiation ground simulation test was conducted on the mechanical property of polyimide film, thermo gravimetric and X-ray Photoelectron Spectroscopy was used to analyze the evolution mechanism of polyimide film in different electron fluencies. It was found that the mechanical properties such as tensile force, tensile strength and rupture elongation of polyimide film increased firstly and then exponentially decreased. The corresponding initial decomposition temperature of the electron-radiated polyimide film lowered from 595 ℃ to 583 ℃ for weight-loss ratio of 10%. From XPS analysis, it can be found that there were ruptures and crosslinks of chemical bonds in the polyimide film. In early stage of electron irradiation, the rupture of CN bond and the following crosslink increased the mechanical properties of polyimide film; however, along with the increase of electron irradiation, the ruptures of C=O and N（CO）bonds, formation of CN bond, as well as release of N were the main factors for the decrease of mechanical properties of polyimide films.
The electron irradiation ground simulation test was conducted on the mechanical property of polyimide film, thermo gravimetric and X-ray Photoelectron Spectroscopy was used to analyze the evolution mechanism of polyimide film in different electron fluencies. It was found that the mechanical properties such as tensile force, tensile strength and rupture elongation of polyimide film increased firstly and then exponentially decreased. The corresponding initial decomposition temperature of the electron-radiated polyimide film lowered from 595 ℃ to 583 ℃ for weight-loss ratio of 10%. From XPS analysis, it can be found that there were ruptures and crosslinks of chemical bonds in the polyimide film. In early stage of electron irradiation, the rupture of CN bond and the following crosslink increased the mechanical properties of polyimide film; however, along with the increase of electron irradiation, the ruptures of C=O and N（CO）bonds, formation of CN bond, as well as release of N were the main factors for the decrease of mechanical properties of polyimide films.
