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RSS2016 Vol. 28, No. 04
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2016,
28: 041002.
doi: 10.11884/HPLPB201628.121002
Abstract:
A numerical simulation is performed to calculate temperature and stress distributions in K9 glass sample irradiated by KrF excimer laser using finite element method, and the relationship between laser parameters and damage effect is also studied. The simulation results indicate that the damage of K9 glass irradiated by KrF excimer laser is thermal stress damage when the incident laser energy is low. The stress damage in laser spot area is dominated by compressive stress, and the damage near the edge of the spot or inside the K9 glass is dominated by tensile stress. The thermal stress as shock wave oscillates obviously inside the K9 glass sample. It is shown that repetition frequency and the number of pulses affect damage considerably, and the accumulation of multi-shot laser induced damage in K9 glass is obvious.
A numerical simulation is performed to calculate temperature and stress distributions in K9 glass sample irradiated by KrF excimer laser using finite element method, and the relationship between laser parameters and damage effect is also studied. The simulation results indicate that the damage of K9 glass irradiated by KrF excimer laser is thermal stress damage when the incident laser energy is low. The stress damage in laser spot area is dominated by compressive stress, and the damage near the edge of the spot or inside the K9 glass is dominated by tensile stress. The thermal stress as shock wave oscillates obviously inside the K9 glass sample. It is shown that repetition frequency and the number of pulses affect damage considerably, and the accumulation of multi-shot laser induced damage in K9 glass is obvious.
2016,
28: 041001.
doi: 10.11884/HPLPB201628.121001
Abstract:
Demodulation algorithm is the key technique of interferometry. Simulation and experiment study of the phase generation carrier(PGC) algorithm is done based on the fiber photo-thermal instrument. Firstly, the study found the mechanism of phase generated carrier algorithms for measuring phase change information; secondly, it verified the PGC algorithms through applying different voltage on piezoelectricity to simulate the actual aerosol absorption coefficient circumstance, and finally it compared corresponding results of different nitrogen dioxide concentration, simulating demodulation phase signal and interference pattern method. The results prove that the PGC algorithms can satisfy the requirements of the fiber photo-thermal aerosol absorption measurement instrument.
Demodulation algorithm is the key technique of interferometry. Simulation and experiment study of the phase generation carrier(PGC) algorithm is done based on the fiber photo-thermal instrument. Firstly, the study found the mechanism of phase generated carrier algorithms for measuring phase change information; secondly, it verified the PGC algorithms through applying different voltage on piezoelectricity to simulate the actual aerosol absorption coefficient circumstance, and finally it compared corresponding results of different nitrogen dioxide concentration, simulating demodulation phase signal and interference pattern method. The results prove that the PGC algorithms can satisfy the requirements of the fiber photo-thermal aerosol absorption measurement instrument.
2016,
28: 040102.
doi: 10.11884/HPLPB201628.120102
Abstract:
Four channels of 500 W power-level all fiberized, narrow-band, and polarization-maintained amplifiers are coaxially combined using active phasing coherent polarization beam combining (CPBC) system. When the phase control system is in closed loop, 2164 W output power is achieved with combing efficiency of 94.5%. In the experiment, the combining efficiency does not degrade obviously along with power scaling process. This is the highest output power based on CPBC system up to now.
Four channels of 500 W power-level all fiberized, narrow-band, and polarization-maintained amplifiers are coaxially combined using active phasing coherent polarization beam combining (CPBC) system. When the phase control system is in closed loop, 2164 W output power is achieved with combing efficiency of 94.5%. In the experiment, the combining efficiency does not degrade obviously along with power scaling process. This is the highest output power based on CPBC system up to now.
2016,
28: 040101.
doi: 10.11884/HPLPB201628.120101
Abstract:
The first X-ray backlighting of Z-pinched aluminium liner with sinusoidal perturbations experiment was carried out on PTS facility. A kilo-joule laser (1053 nm, 1 kJ, 1 ns) was used to drive the solid target to produce X-rays and the development of the instability of the Z-pinched aluminium liner outer edge, under a driver current of 7.5 MA, was successfully observed by using the monochromatic X-ray backlighting based on spherical-bent crystal and the direct point shadow radiography, respectively. This experiment confirmed the capability of X-ray backlighting on the PTS facility by union of the kilo-joule laser and it provided the foundation for the subsequent researching of the fine Z-pinch physics.
The first X-ray backlighting of Z-pinched aluminium liner with sinusoidal perturbations experiment was carried out on PTS facility. A kilo-joule laser (1053 nm, 1 kJ, 1 ns) was used to drive the solid target to produce X-rays and the development of the instability of the Z-pinched aluminium liner outer edge, under a driver current of 7.5 MA, was successfully observed by using the monochromatic X-ray backlighting based on spherical-bent crystal and the direct point shadow radiography, respectively. This experiment confirmed the capability of X-ray backlighting on the PTS facility by union of the kilo-joule laser and it provided the foundation for the subsequent researching of the fine Z-pinch physics.
2016,
28: 041003.
doi: 10.11884/HPLPB201628.121003
Abstract:
Micro-spall problem of shock-melted materials is an important scientific issue in shock physics. This paper examines the application of the advanced laser-driven X-ray backlighting technique in the study of this problem. High energy laser beams were launched by SGⅡ to drive the aluminum physical target and the copper backlighting target. The X-ray emitted from the backlighting target was directed to pass through a pinhole to take the radiograph of the microspall products. High-quality radiograph was finally obtained, whose spatial resolution was found to be greater than 40 m via the examination of standard grids. Moreover, the radiograph shows clearly the products can be divided into different regions, which directly reveals different mechanism of the fragmentation of the target. The success of our exploring experiments demonstrate the prospect of the application of the technique in the micro-spall study.
Micro-spall problem of shock-melted materials is an important scientific issue in shock physics. This paper examines the application of the advanced laser-driven X-ray backlighting technique in the study of this problem. High energy laser beams were launched by SGⅡ to drive the aluminum physical target and the copper backlighting target. The X-ray emitted from the backlighting target was directed to pass through a pinhole to take the radiograph of the microspall products. High-quality radiograph was finally obtained, whose spatial resolution was found to be greater than 40 m via the examination of standard grids. Moreover, the radiograph shows clearly the products can be divided into different regions, which directly reveals different mechanism of the fragmentation of the target. The success of our exploring experiments demonstrate the prospect of the application of the technique in the micro-spall study.
2016,
28: 041004.
doi: 10.11884/HPLPB201628.121004
Abstract:
Based on indentation experiments and continuous stiffness method, the relationship curves between indentation depth and hardness/elastic modulus were obtained for fused silica optics. The process of ductile to brittle transition was systematically analyzed, and the critical loads and critical depths were determined in static/quasi-static indentation or dynamic scratch process. The results of gradient load scratch experiments show that the crack induced by scratch process has a strong dependence on the normal load, and the material removal is ductile removal with a small load. With the increase of normal load, the median cracks perpendicular to the specimen surface and lateral cracks parallel to specimen surface are produced, while no obvious features are observed on specimen surface. Lateral cracks are extended and the bright regions are formed, eventually the radial cracks are induced, whose propagation directions are perpendicular or approximately perpendicular to indenter movement direction, so brittle material removal is achieved.
Based on indentation experiments and continuous stiffness method, the relationship curves between indentation depth and hardness/elastic modulus were obtained for fused silica optics. The process of ductile to brittle transition was systematically analyzed, and the critical loads and critical depths were determined in static/quasi-static indentation or dynamic scratch process. The results of gradient load scratch experiments show that the crack induced by scratch process has a strong dependence on the normal load, and the material removal is ductile removal with a small load. With the increase of normal load, the median cracks perpendicular to the specimen surface and lateral cracks parallel to specimen surface are produced, while no obvious features are observed on specimen surface. Lateral cracks are extended and the bright regions are formed, eventually the radial cracks are induced, whose propagation directions are perpendicular or approximately perpendicular to indenter movement direction, so brittle material removal is achieved.
2016,
28: 042001.
doi: 10.11884/HPLPB201628.122001
Abstract:
The integration simulation of two-hole spherical hohlraum under three-temperature model and radiation transfer model is accomplished by the 2-D LARED-Integration code. The electron temperature at corona region is comparable, while the radiation temperature inside hohlraum differs. The radiation temperature inside hohlraum intensively depends on the radiation opacity. When the opacities are close, the radiation temperatures by three-temperature model and radiation transfer model are in full accord with each other.
The integration simulation of two-hole spherical hohlraum under three-temperature model and radiation transfer model is accomplished by the 2-D LARED-Integration code. The electron temperature at corona region is comparable, while the radiation temperature inside hohlraum differs. The radiation temperature inside hohlraum intensively depends on the radiation opacity. When the opacities are close, the radiation temperatures by three-temperature model and radiation transfer model are in full accord with each other.
2016,
28: 042002.
doi: 10.11884/HPLPB201628.122002
Abstract:
Measurement of shock temperature under high temperature and high pressure is an essential part of equations of state(EOS) research. This paper introduces a temperature diagnosis system for laser-driven shock wave experiment on the basis of SG-Ⅱ high-power laser facility. The system comprised the streaked optical pyrometer (SOP) which is high time-resolved and the spectral resolved SOP (SSOP). The VISAR system was added to measure emissivity. The on-line calibration system of temperature measurement was established simultaneously using a NIST traceable standard lamp. High time-resolved signal images of the high temperature radiation spectrum were obtained through experiments driven by high power laser on aluminum using the diagnosis system. The shock temperature of aluminum was obtained according to gray body radiation theoretical model. The measured temperature was 2.95 eV, which was close to Hugoniot temperature in SESAME library at the same shock wave velocity. The experiment result indicates that the temperature measurement system used in the experiment can diagnose the shock temperature of metallic materials effectively. Key words:
Measurement of shock temperature under high temperature and high pressure is an essential part of equations of state(EOS) research. This paper introduces a temperature diagnosis system for laser-driven shock wave experiment on the basis of SG-Ⅱ high-power laser facility. The system comprised the streaked optical pyrometer (SOP) which is high time-resolved and the spectral resolved SOP (SSOP). The VISAR system was added to measure emissivity. The on-line calibration system of temperature measurement was established simultaneously using a NIST traceable standard lamp. High time-resolved signal images of the high temperature radiation spectrum were obtained through experiments driven by high power laser on aluminum using the diagnosis system. The shock temperature of aluminum was obtained according to gray body radiation theoretical model. The measured temperature was 2.95 eV, which was close to Hugoniot temperature in SESAME library at the same shock wave velocity. The experiment result indicates that the temperature measurement system used in the experiment can diagnose the shock temperature of metallic materials effectively. Key words:
2016,
28: 043001.
doi: 10.11884/HPLPB201628.123001
Abstract:
A kind of high-power coplanar-feed impulse radiating antenna (IRA) is described in this paper. It is constructed of four electrically large coplanar arms, and a 2.1 m diameter paraboloid reflector. To get higher gain, the point feed was fixed at the reflector focus. To figure out the high power feed problem, a kind of new high power balun was introduced, with conical input to 4 points output. The high-power coplanar-feed IRA was fabricated and the farfield was measured. The results show that: with 450 ps pulse width, 142 kV peak voltage short pulse input, the rE value could reach 800 kV.
A kind of high-power coplanar-feed impulse radiating antenna (IRA) is described in this paper. It is constructed of four electrically large coplanar arms, and a 2.1 m diameter paraboloid reflector. To get higher gain, the point feed was fixed at the reflector focus. To figure out the high power feed problem, a kind of new high power balun was introduced, with conical input to 4 points output. The high-power coplanar-feed IRA was fabricated and the farfield was measured. The results show that: with 450 ps pulse width, 142 kV peak voltage short pulse input, the rE value could reach 800 kV.
2016,
28: 043101.
doi: 10.11884/HPLPB201628.123101
Abstract:
The scattering characteristics in terahertz band of uniform partition and non-uniform unstable conducting target with different roughness surface is studied. This paper proposes to apply the modeling concept of randomly rough surface to the modeling of uniform partition and non-uniform unstable rough surface target in terahertz band, which is different from the modeling method of using formulae. Two physical quantities which are used to describe the RMS height and correlation length of rough surface are applied to adjust the roughness of target surface. Firstly, the rough surfaces of uniform partition and non-uniform unstable target are modeled by Gaussian random surface, then a combined method of physic optics and equivalent current is employed for simulation. The THz wave scattering characteristics of different rough surface target with different incident angles, different frequencies and different roughness are analyzed and discussed. Finally, the relevant conclusions are drawn.
The scattering characteristics in terahertz band of uniform partition and non-uniform unstable conducting target with different roughness surface is studied. This paper proposes to apply the modeling concept of randomly rough surface to the modeling of uniform partition and non-uniform unstable rough surface target in terahertz band, which is different from the modeling method of using formulae. Two physical quantities which are used to describe the RMS height and correlation length of rough surface are applied to adjust the roughness of target surface. Firstly, the rough surfaces of uniform partition and non-uniform unstable target are modeled by Gaussian random surface, then a combined method of physic optics and equivalent current is employed for simulation. The THz wave scattering characteristics of different rough surface target with different incident angles, different frequencies and different roughness are analyzed and discussed. Finally, the relevant conclusions are drawn.
2016,
28: 044001.
doi: 10.11884/HPLPB201628.124001
Abstract:
When the devices are irradiated with the system at the transient dose rate, many of them will work at the state that all of the input signal, power supply and the photocurrent are out of the designed state. This transient effects can not be found by irradiating the device only. So transient radiation effects with -ray on an electronics system, composed of DC/DC, CPU, FPGA, et al, were investigated. The gamma pulse width was 20 ns and the dose rate was in the range of 2.8105 to 1.7107 Gy (Si)/s in the experimental study. And the function of the system and many parameters of the main devices were tested. The result of experiments showed that some of the test devices were disrupted by low level of transient radiation, but the system work was not disturbed. While the dose rates increased, all of the devices were disrupted and the system function failed. The signal originating from the transient ionizing radiation transferring from the input to the output of the device was observed.
When the devices are irradiated with the system at the transient dose rate, many of them will work at the state that all of the input signal, power supply and the photocurrent are out of the designed state. This transient effects can not be found by irradiating the device only. So transient radiation effects with -ray on an electronics system, composed of DC/DC, CPU, FPGA, et al, were investigated. The gamma pulse width was 20 ns and the dose rate was in the range of 2.8105 to 1.7107 Gy (Si)/s in the experimental study. And the function of the system and many parameters of the main devices were tested. The result of experiments showed that some of the test devices were disrupted by low level of transient radiation, but the system work was not disturbed. While the dose rates increased, all of the devices were disrupted and the system function failed. The signal originating from the transient ionizing radiation transferring from the input to the output of the device was observed.
2016,
28: 044002.
doi: 10.11884/HPLPB201628.124002
Abstract:
As silicon bipolar devices and circuits have different radiation effects from other types of circuits, such as enhanced low dose rate sensitivity, this article analyzes the space radiation environment, Al shield effect, the total ionizing dose radiation damage mechanism and the principle, rule, and electrical parameters change by enhanced low dose rate radiation sensitivity of bipolar devices and circuits. The radiation experiment in lab with several typical bipolar devices and circuits indicates that the important parameters of the bipolar devices and circuits are greatly influenced by total ionizing dose radiation, especially by low dose rate radiation, with the enhancement factors of low dose rate radiation mostly more than 1.5.Different bipolar devices and circuits have different enhanced low dose rate sensitivity, which is mainly due to device types and manufacture process (such as oxidation layer thickness).
As silicon bipolar devices and circuits have different radiation effects from other types of circuits, such as enhanced low dose rate sensitivity, this article analyzes the space radiation environment, Al shield effect, the total ionizing dose radiation damage mechanism and the principle, rule, and electrical parameters change by enhanced low dose rate radiation sensitivity of bipolar devices and circuits. The radiation experiment in lab with several typical bipolar devices and circuits indicates that the important parameters of the bipolar devices and circuits are greatly influenced by total ionizing dose radiation, especially by low dose rate radiation, with the enhancement factors of low dose rate radiation mostly more than 1.5.Different bipolar devices and circuits have different enhanced low dose rate sensitivity, which is mainly due to device types and manufacture process (such as oxidation layer thickness).
2016,
28: 044003.
doi: 10.11884/HPLPB201628.124003
Abstract:
The generalized theory of double-stage electrostatic reflection system for time-domain compressing electron packet is presented. In analog to the multilayer dielectric optical chirp mirror for compressing optical pulse, the system is renamed as tunable electrostatic chirp mirror, of which the tunability of chirp properties is analyzed detailedly. The essential difference between the two chirp properties lies in the dispersive dependence of electrons time of flight on its initial energy: the electrons with higher initial axial energy have longer time of flight for positive chirp, while it is not the case for negative chirp. The time of flight dispersive dependence constitutes the mechanism of electron packet compression for each mode. And an example illustration is given.
The generalized theory of double-stage electrostatic reflection system for time-domain compressing electron packet is presented. In analog to the multilayer dielectric optical chirp mirror for compressing optical pulse, the system is renamed as tunable electrostatic chirp mirror, of which the tunability of chirp properties is analyzed detailedly. The essential difference between the two chirp properties lies in the dispersive dependence of electrons time of flight on its initial energy: the electrons with higher initial axial energy have longer time of flight for positive chirp, while it is not the case for negative chirp. The time of flight dispersive dependence constitutes the mechanism of electron packet compression for each mode. And an example illustration is given.
2016,
28: 045001.
doi: 10.11884/HPLPB201628.125001
Abstract:
A control system based on DSP is designed for the application of the power supply. By regulating the control system, the output voltage can be regulated from 0 to 30 kV, and the repetition frequency can be regulated from 1 to 100 Hz. In order to operate more easily, two control modes are designed, one is the remote computer control and the other is the local control by LCD and keyboard. The multiple protective circuits are designed to process the faults which are over voltage, over current, over time or over temperature. In order to extend the application of this power supply, an external trigger control interface is provided for the synchronization control of the power supply and other equipments of the laser. The electromagnetic compatibility design of the power supply is adopted in the control system. Coupled with a fiber optical control and feed back communication system, the anti-interference performance of the control system is much better.
A control system based on DSP is designed for the application of the power supply. By regulating the control system, the output voltage can be regulated from 0 to 30 kV, and the repetition frequency can be regulated from 1 to 100 Hz. In order to operate more easily, two control modes are designed, one is the remote computer control and the other is the local control by LCD and keyboard. The multiple protective circuits are designed to process the faults which are over voltage, over current, over time or over temperature. In order to extend the application of this power supply, an external trigger control interface is provided for the synchronization control of the power supply and other equipments of the laser. The electromagnetic compatibility design of the power supply is adopted in the control system. Coupled with a fiber optical control and feed back communication system, the anti-interference performance of the control system is much better.
2016,
28: 045002.
doi: 10.11884/HPLPB201628.125002
Abstract:
A new CaO-TiO2-Al2O3 based dielectric ceramic system is designed for pulse forming line application. The dielectric ceramic is prepared by traditional solid state method and its microstructure was controlled by optimizing the composition and preparation process. The dielectric ceramic exhibits an excellent dielectric properties. The frequency stability of the dielectric constant is good. The dielectric loss is less than 0.002 in a wide frequency range. The electric strength is up to 50 kV/mm (1 mm in thickness). The influence of thickness on the electric strength of CaO-TiO2-Al2O3 based dielectric ceramics is studied. With the thickness decreasing from 1 mm to 0.1 mm, the dielectric breakdown strength increases nonlinearly from 50 kV/mm to 92 kV/mm. So it can be seen that the dielectric breakdown of the CaO-TiO2-Al2O3 dielectric ceramics is similar to their mechanical damage. Based on the chemical compositions and the microstructures, the dielectric breakdown mechanism of CaO-TiO2-Al2O3 dielectric ceramics can be explained by the weak breakdown theory.
A new CaO-TiO2-Al2O3 based dielectric ceramic system is designed for pulse forming line application. The dielectric ceramic is prepared by traditional solid state method and its microstructure was controlled by optimizing the composition and preparation process. The dielectric ceramic exhibits an excellent dielectric properties. The frequency stability of the dielectric constant is good. The dielectric loss is less than 0.002 in a wide frequency range. The electric strength is up to 50 kV/mm (1 mm in thickness). The influence of thickness on the electric strength of CaO-TiO2-Al2O3 based dielectric ceramics is studied. With the thickness decreasing from 1 mm to 0.1 mm, the dielectric breakdown strength increases nonlinearly from 50 kV/mm to 92 kV/mm. So it can be seen that the dielectric breakdown of the CaO-TiO2-Al2O3 dielectric ceramics is similar to their mechanical damage. Based on the chemical compositions and the microstructures, the dielectric breakdown mechanism of CaO-TiO2-Al2O3 dielectric ceramics can be explained by the weak breakdown theory.
2016,
28: 045003.
doi: 10.11884/HPLPB201628.125003
Abstract:
The dielectric wall linear accelerator, based on technologies of solid-state pulse forming lines, photoconductive semiconductor switches and high gradient insulators, is a new concept linear accelerator being developed at Institute of Fluid Physics, CAEP. During accelerator test process, the measured energy gain of the accelerated proton beam is much lower than expected. After the exclusion of the pulsed power source factor, we find that the coupling effect induced connecting circuit is the main factor of causing low beam energy gain. Based on discharge circuit analysis of the dielectric wall linear accelerator acceleration unit, we confirm that the circuit coupling between acceleration units is inevitable. The circuit coupling of several different operation modes is studied by measuring the circuit current. According to the characteristics of the coupled circuit, we give two kind of decoupling methods based on the magnetic core isolation, and we measure the efficiency of the decoupling of the two methods.
The dielectric wall linear accelerator, based on technologies of solid-state pulse forming lines, photoconductive semiconductor switches and high gradient insulators, is a new concept linear accelerator being developed at Institute of Fluid Physics, CAEP. During accelerator test process, the measured energy gain of the accelerated proton beam is much lower than expected. After the exclusion of the pulsed power source factor, we find that the coupling effect induced connecting circuit is the main factor of causing low beam energy gain. Based on discharge circuit analysis of the dielectric wall linear accelerator acceleration unit, we confirm that the circuit coupling between acceleration units is inevitable. The circuit coupling of several different operation modes is studied by measuring the circuit current. According to the characteristics of the coupled circuit, we give two kind of decoupling methods based on the magnetic core isolation, and we measure the efficiency of the decoupling of the two methods.
2016,
28: 045004.
doi: 10.11884/HPLPB201628.125004
Abstract:
The performance of the 10-stage LTD generator is investigated in experiments with some stages uncharged or untriggered. The result shows that both the current and the voltage decrease by almost 10%, 20% and 30%, the pulse rise-time increases by 10, 22 and 32 ns and the pulse width increases by 13, 23 and 48 ns, for 1, 2 and 3 malfunctioning stages respectively. Compared with the LTD generator in good condition, the equivalent circuit simulation of the LTD generator working abnormally demonstrates that the variation trends of the current and the voltage in the load agree well with the experimental results. In addition, the induced voltage on the switch in the malfunction stage is simulated and analyzed.
The performance of the 10-stage LTD generator is investigated in experiments with some stages uncharged or untriggered. The result shows that both the current and the voltage decrease by almost 10%, 20% and 30%, the pulse rise-time increases by 10, 22 and 32 ns and the pulse width increases by 13, 23 and 48 ns, for 1, 2 and 3 malfunctioning stages respectively. Compared with the LTD generator in good condition, the equivalent circuit simulation of the LTD generator working abnormally demonstrates that the variation trends of the current and the voltage in the load agree well with the experimental results. In addition, the induced voltage on the switch in the malfunction stage is simulated and analyzed.
2016,
28: 045005.
doi: 10.11884/HPLPB201628.125005
Abstract:
This paper proposes a new structure of a low-jitter repetitive pulse power generator based on Tesla transformer and Blumlein pulse forming line(PFL). The parameters of the Tesla transformer and the Blumlein PFL are designed. To reduce the jitter, a low-jitter repetitive multi-stage corona-stabilized switch is developed, while the electrical field distribution of the switch is analyzed. New transformer oil named MIDEL 7131 is used by insulation medium of Blumlein PFL. The experimental results show that the output pulse on a match resistive load is about 130 kV and the width is 5.5 ns. The generator can operate at a repetitive frequency of 50 Hz over 3000 pulses and the jitter is less than 10 ns.
This paper proposes a new structure of a low-jitter repetitive pulse power generator based on Tesla transformer and Blumlein pulse forming line(PFL). The parameters of the Tesla transformer and the Blumlein PFL are designed. To reduce the jitter, a low-jitter repetitive multi-stage corona-stabilized switch is developed, while the electrical field distribution of the switch is analyzed. New transformer oil named MIDEL 7131 is used by insulation medium of Blumlein PFL. The experimental results show that the output pulse on a match resistive load is about 130 kV and the width is 5.5 ns. The generator can operate at a repetitive frequency of 50 Hz over 3000 pulses and the jitter is less than 10 ns.
2016,
28: 045006.
doi: 10.11884/HPLPB201628.125006
Abstract:
The statistical model is used as a typical method for vacuum insulator stack flashover probability calculation. We have calculated the stack flashover probability and the g factors by which a flashover will change the voltages on the each of the insulator rings with different conditions. The calculated results show that the real performance of insulator stack characteristics with the multi-stage and large circumferential transit time. The matrix a in the statistical model was predigested to reduce the g calculation time and make the probability calculation accurate. Finally, analysis based on fixed distance between insulation rings showed that there were some optimized ring numbers with maximum voltage amplitude and electrical field amplitude. This conclusion could be used for evaluation of insulation ring number in insulator stack design.
The statistical model is used as a typical method for vacuum insulator stack flashover probability calculation. We have calculated the stack flashover probability and the g factors by which a flashover will change the voltages on the each of the insulator rings with different conditions. The calculated results show that the real performance of insulator stack characteristics with the multi-stage and large circumferential transit time. The matrix a in the statistical model was predigested to reduce the g calculation time and make the probability calculation accurate. Finally, analysis based on fixed distance between insulation rings showed that there were some optimized ring numbers with maximum voltage amplitude and electrical field amplitude. This conclusion could be used for evaluation of insulation ring number in insulator stack design.
2016,
28: 045007.
doi: 10.11884/HPLPB201628.125007
Abstract:
The pattern of plate-plate electrodes with the gap of 2 mm and the discharge current peak of 22 kA is used to compare and research the erosion characteristics of the brass and W-Cu electrodes. The mass loss of the eroded electrode during the pulsed discharge process can be obtained by a high precision balance. Then, the erosion rates of the anode, cathode and total average erosion rates of the electrodes can be calculated, respectively. The micro morphology analysis about the surface of the eroded electrode and the comparison about the content of the metal ions will help to investigate the erosion mechanism of metal electrodes in water. The results show that anti-erosion performance of the W-Cu is obviously better than that of the brass under pulsed discharge in water. For the brass electrodes, large amounts of holes and craters in the central area and the wave structure in the edge area indicate that sputtering of the molten metal is the major erosion form while the unique protuberances and relatively smooth surface of the W-Cu electrode imply the action of the vapor-phase erosion. When regarding Joule heating effect as the powerful catalyst, the electrochemical reaction of the W-Cu behaves more fiercely than that of the brass. Therefore, its unreasonable to neglect the influences of the electrochemical corrosion on the eroded surface when the pulsed discharge occurs in water.
The pattern of plate-plate electrodes with the gap of 2 mm and the discharge current peak of 22 kA is used to compare and research the erosion characteristics of the brass and W-Cu electrodes. The mass loss of the eroded electrode during the pulsed discharge process can be obtained by a high precision balance. Then, the erosion rates of the anode, cathode and total average erosion rates of the electrodes can be calculated, respectively. The micro morphology analysis about the surface of the eroded electrode and the comparison about the content of the metal ions will help to investigate the erosion mechanism of metal electrodes in water. The results show that anti-erosion performance of the W-Cu is obviously better than that of the brass under pulsed discharge in water. For the brass electrodes, large amounts of holes and craters in the central area and the wave structure in the edge area indicate that sputtering of the molten metal is the major erosion form while the unique protuberances and relatively smooth surface of the W-Cu electrode imply the action of the vapor-phase erosion. When regarding Joule heating effect as the powerful catalyst, the electrochemical reaction of the W-Cu behaves more fiercely than that of the brass. Therefore, its unreasonable to neglect the influences of the electrochemical corrosion on the eroded surface when the pulsed discharge occurs in water.
2016,
28: 045008.
doi: 10.11884/HPLPB201628.125008
Abstract:
The compact and miniaturization properties are playing a considerably important role in the high power ns pulse forming network. The components and characteristics of a two-node anti-resonance pulse forming network which generates square pulses is introduced and the equivalent circuit of this network is obtained. A method for designing parameters of this type of circuit is put forward by using the Laplace transform and the Fourier series expansion, and the corresponding simulation is carried out. The simulation results show that the flattop of the output pulse is about 1/4 of the whole pulse duration, while the rise time is about 1/7 and the pulse width is 5/7. Preliminary experimental investigation is studied and the results indicate that the two-node anti-resonance pulse forming network can generate ns square pulses which is in accord with the simulation results.
The compact and miniaturization properties are playing a considerably important role in the high power ns pulse forming network. The components and characteristics of a two-node anti-resonance pulse forming network which generates square pulses is introduced and the equivalent circuit of this network is obtained. A method for designing parameters of this type of circuit is put forward by using the Laplace transform and the Fourier series expansion, and the corresponding simulation is carried out. The simulation results show that the flattop of the output pulse is about 1/4 of the whole pulse duration, while the rise time is about 1/7 and the pulse width is 5/7. Preliminary experimental investigation is studied and the results indicate that the two-node anti-resonance pulse forming network can generate ns square pulses which is in accord with the simulation results.
2016,
28: 045009.
doi: 10.11884/HPLPB201628.125009
Abstract:
In Z-pinch experiments on Primary Test Stand, a specially configured flat spectral response X-ray diode (FSR-XRD) was used to diagnose X-ray flux, which utilized a gold cathode XRD and a compounded gold filter to give rise to a nearly flat spectral response in photon energy range of 0.1-4 keV. To establish an absolute measurement of X-ray flux, each XRD and filter used was calibrated on beam lines 4B7B and 4B7A, Beijing synchrotron radiation facility. In typical experiments, uncertainty of X-ray power measurement inferred by FSR-XRD was 12%. In a single tungsten wire array Z-pinches experiment, diagnosed X-ray power exceeded 52 TW, energy was about 540 kJ. In dynamical hohlraum experiments, an FSR-XRD in the radial and an FSR-XRD in the axial were used to provide a time correlated measurement of X-ray pulse. In a typical dynamical hohlraum experiment, peak of axial X-ray power occurred before radial power by amount of about 1.2 ns.
In Z-pinch experiments on Primary Test Stand, a specially configured flat spectral response X-ray diode (FSR-XRD) was used to diagnose X-ray flux, which utilized a gold cathode XRD and a compounded gold filter to give rise to a nearly flat spectral response in photon energy range of 0.1-4 keV. To establish an absolute measurement of X-ray flux, each XRD and filter used was calibrated on beam lines 4B7B and 4B7A, Beijing synchrotron radiation facility. In typical experiments, uncertainty of X-ray power measurement inferred by FSR-XRD was 12%. In a single tungsten wire array Z-pinches experiment, diagnosed X-ray power exceeded 52 TW, energy was about 540 kJ. In dynamical hohlraum experiments, an FSR-XRD in the radial and an FSR-XRD in the axial were used to provide a time correlated measurement of X-ray pulse. In a typical dynamical hohlraum experiment, peak of axial X-ray power occurred before radial power by amount of about 1.2 ns.
2016,
28: 045010.
doi: 10.11884/HPLPB201628.125010
Abstract:
Double-exponent pulse current generator can be used in conducted coupling experiment of electronic system ports. The generator can produce a double-exponent pulse current of rise-time 10 ns, pulse width 100 ns and current amplitude 3 kA. In this article, a circuit model of generator is established. Influence of stray capacitor and inductance on pulse current is analyzed and a possible optimizing scheme is also mentioned. Results of simulation show that stray capacitor at load can cause overshoot on the current waveform. At the same time, stray capacitor and inductance at current measurement zone can also cause oscillating interferential wave on the falling edge of current waveform. There are two possible methods to restrain the overshoot and interference. One is that a filter should be fitted at the current measurement zone. The other is that a lossless coaxial cable with proper impedance should be used to transmit the current.
Double-exponent pulse current generator can be used in conducted coupling experiment of electronic system ports. The generator can produce a double-exponent pulse current of rise-time 10 ns, pulse width 100 ns and current amplitude 3 kA. In this article, a circuit model of generator is established. Influence of stray capacitor and inductance on pulse current is analyzed and a possible optimizing scheme is also mentioned. Results of simulation show that stray capacitor at load can cause overshoot on the current waveform. At the same time, stray capacitor and inductance at current measurement zone can also cause oscillating interferential wave on the falling edge of current waveform. There are two possible methods to restrain the overshoot and interference. One is that a filter should be fitted at the current measurement zone. The other is that a lossless coaxial cable with proper impedance should be used to transmit the current.
2016,
28: 045011.
doi: 10.11884/HPLPB201628.125011
Abstract:
Parasitic transmission lines located between the stages have severe impact on the output waveform of a PFN-Marx generator. In this paper, the discharging processes of the parasitic transmission line in two kinds of PFN-Marx generators are analyzed. Especially, a two-row structure PFN Marx was simulated by the full circuit simulation. The simulation results show that the dropping of the rising edge of the output waveform was caused by the diode load, the parasitic oscillation frequency was decided by the parasitic capacitance and the amplitude of the parasitic oscillation was amplified by the load inductance. The following experiments proved the results. A de-oscillation circuit was proposed and also proved by the circuit simulation. Further experiments confirmed the validity of this circuit.
Parasitic transmission lines located between the stages have severe impact on the output waveform of a PFN-Marx generator. In this paper, the discharging processes of the parasitic transmission line in two kinds of PFN-Marx generators are analyzed. Especially, a two-row structure PFN Marx was simulated by the full circuit simulation. The simulation results show that the dropping of the rising edge of the output waveform was caused by the diode load, the parasitic oscillation frequency was decided by the parasitic capacitance and the amplitude of the parasitic oscillation was amplified by the load inductance. The following experiments proved the results. A de-oscillation circuit was proposed and also proved by the circuit simulation. Further experiments confirmed the validity of this circuit.
2016,
28: 045012.
doi: 10.11884/HPLPB201628.125012
Abstract:
Four coaxial electrodes with identical shape but different surface characteristics are made by common surface treatments, including sanding, wool polishing, metal electroplating and nonmetal electroplating. The relationship between different surface characteristics and the insulation characteristics of the glycerol medium is studied by experiments. A thyristor controlled air-core pulse transformer with a maximum output voltage of 500 kV and the rising time of 26 s is built. The experimental results show that the four kinds of electrodes have significantly different microcosmic morphologies, resulting in different breakdown characteristics of the glycerol between the electrodes. Under the same charging voltage, the average breakdown strength of the glycerol is 210-260 kV/cm. Compared with the conventional sanded electrodes, the breakdown strength of electrodes disposed by wool polishing, metal electroplating and nonmetal electroplating can be increased by 14.51%, 11.60% and 19.67% respectively. Due to their much higher surface uniformity, the highest breakdown strength between nonmetal electroplating electrodes can reach up to 288 kV/cm, which is 33.09% larger than the average value of the control group.
Four coaxial electrodes with identical shape but different surface characteristics are made by common surface treatments, including sanding, wool polishing, metal electroplating and nonmetal electroplating. The relationship between different surface characteristics and the insulation characteristics of the glycerol medium is studied by experiments. A thyristor controlled air-core pulse transformer with a maximum output voltage of 500 kV and the rising time of 26 s is built. The experimental results show that the four kinds of electrodes have significantly different microcosmic morphologies, resulting in different breakdown characteristics of the glycerol between the electrodes. Under the same charging voltage, the average breakdown strength of the glycerol is 210-260 kV/cm. Compared with the conventional sanded electrodes, the breakdown strength of electrodes disposed by wool polishing, metal electroplating and nonmetal electroplating can be increased by 14.51%, 11.60% and 19.67% respectively. Due to their much higher surface uniformity, the highest breakdown strength between nonmetal electroplating electrodes can reach up to 288 kV/cm, which is 33.09% larger than the average value of the control group.
2016,
28: 045013.
doi: 10.11884/HPLPB201628.125013
Abstract:
In order to generate a high-energy plasma synthetic jet, a compact microsecond-pulse power supply is developed and tested. The maximum output voltage is 10 kV with a pulse repetition rate of 100 Hz and the generator can withstand a discharge current with an amplitude of 250 A. Moreover, the working principle of the generator is introduced and the effect of different capacitor on the primary current and output voltage is compared. Furthermore, the designed generator is successfully used for generating plasma synthetic jet. The effect of the gap distance on the plasma synthetic jet is analyzed. The ratio of dissipation energy at different discharge capacitors is compared. The results show that: The breakdown voltage for different discharge capacitors has a similar value at the same gap distance. The breakdown voltage increases with the gap distance. In addition, large discharge current can be generated when the discharge capacitor is used. The discharge current increases with the value of the discharge capacitor. The ratio of dissipation energy is higher in the case with discharge capacitor than that in the case without discharge capacitor. Under such conditions, it is easy to generate a high-energy plasma synthetic jet.
In order to generate a high-energy plasma synthetic jet, a compact microsecond-pulse power supply is developed and tested. The maximum output voltage is 10 kV with a pulse repetition rate of 100 Hz and the generator can withstand a discharge current with an amplitude of 250 A. Moreover, the working principle of the generator is introduced and the effect of different capacitor on the primary current and output voltage is compared. Furthermore, the designed generator is successfully used for generating plasma synthetic jet. The effect of the gap distance on the plasma synthetic jet is analyzed. The ratio of dissipation energy at different discharge capacitors is compared. The results show that: The breakdown voltage for different discharge capacitors has a similar value at the same gap distance. The breakdown voltage increases with the gap distance. In addition, large discharge current can be generated when the discharge capacitor is used. The discharge current increases with the value of the discharge capacitor. The ratio of dissipation energy is higher in the case with discharge capacitor than that in the case without discharge capacitor. Under such conditions, it is easy to generate a high-energy plasma synthetic jet.
2016,
28: 045014.
doi: 10.11884/HPLPB201628.125014
Abstract:
We propose a complete relaxation magnetohydrodynamic (MHD) model for the simulation of electromagnetically driven high energy density (HED) systems. The full relaxation MHD model is composed of relaxation electromagnetic wave, relaxation heat transport, P1/3 approximate radiation transport and certainly the indispensable hydrodynamics (HD). The electromagnetic part transitions from electromagnetic propagation in vacuum to magnetic diffusion in plasma in a natural way. The phase and group velocities are finite for this relaxation system. Therefore, the relaxation MHD can degenerate to resistive MHD and is convenient for explicit parallel computations. The FOI-PERFECT code is developed, based on the relaxation MHD. The key numerical techniques and various applications are given.
We propose a complete relaxation magnetohydrodynamic (MHD) model for the simulation of electromagnetically driven high energy density (HED) systems. The full relaxation MHD model is composed of relaxation electromagnetic wave, relaxation heat transport, P1/3 approximate radiation transport and certainly the indispensable hydrodynamics (HD). The electromagnetic part transitions from electromagnetic propagation in vacuum to magnetic diffusion in plasma in a natural way. The phase and group velocities are finite for this relaxation system. Therefore, the relaxation MHD can degenerate to resistive MHD and is convenient for explicit parallel computations. The FOI-PERFECT code is developed, based on the relaxation MHD. The key numerical techniques and various applications are given.
2016,
28: 045015.
doi: 10.11884/HPLPB201628.125015
Abstract:
An experimental system of a small monolithic radial transmission line is established. This line with hyperbolic characteristic impedance is composed of 2 aluminium-alloy plates with a distance of 1 cm. One output port is placed at the center, while 20 input ports are placed uniformly at the outer circumference. Therefore, the maximum number of input pulses of this line is 20. The line is entirely immersed into deionized water, which makes its one-way transmit time 15 ns. The matched load is composed of 20 154 in parallel. The output voltage obtained in experiment is very close to the result of 3-dimensional electromagnetic simulation. Moreover, by investigating the output voltage with different numbers of input pulses, it is found that the amplitude of the lines output voltage is nearly proportional to the number of input pulses when the number of input pulses is small.
An experimental system of a small monolithic radial transmission line is established. This line with hyperbolic characteristic impedance is composed of 2 aluminium-alloy plates with a distance of 1 cm. One output port is placed at the center, while 20 input ports are placed uniformly at the outer circumference. Therefore, the maximum number of input pulses of this line is 20. The line is entirely immersed into deionized water, which makes its one-way transmit time 15 ns. The matched load is composed of 20 154 in parallel. The output voltage obtained in experiment is very close to the result of 3-dimensional electromagnetic simulation. Moreover, by investigating the output voltage with different numbers of input pulses, it is found that the amplitude of the lines output voltage is nearly proportional to the number of input pulses when the number of input pulses is small.
2016,
28: 045016.
doi: 10.11884/HPLPB201628.125016
Abstract:
An 100 kV compact Marx generator is designed and constructed, and it is presently operational at Northwest Institute of Nuclear Technology. In this paper the principle of compact Marx generator is introduced. Single polarity charge, ceramic capacitance, switch and insulation integrative configuration and function blocking are adopted to make Marx generator compact. The front part of the generator includes trigger, charge and gas pressure control module, and it can work reliably with gas source and AC input only. The Marx generator has a wide working range, with an output voltage range from 15 kV to 100 kV.
An 100 kV compact Marx generator is designed and constructed, and it is presently operational at Northwest Institute of Nuclear Technology. In this paper the principle of compact Marx generator is introduced. Single polarity charge, ceramic capacitance, switch and insulation integrative configuration and function blocking are adopted to make Marx generator compact. The front part of the generator includes trigger, charge and gas pressure control module, and it can work reliably with gas source and AC input only. The Marx generator has a wide working range, with an output voltage range from 15 kV to 100 kV.
2016,
28: 045017.
doi: 10.11884/HPLPB201628.125017
Abstract:
The electromagnetic driven solid liner implosion is one of the high energy density physics (HEDP) experimental techniques. Because of the metal strength, there exists a threshold for driven pressure where plastic flow just begins. And the plastic work that will turn to the internal energy of the metal liner should decrease the kinetic energy of liner, which of course will affect the implosion of the solid liner. The critical current has been found via the elastic-plastic analysis of cylindrical symmetry issue. The zero-dimension (0D) simulation considering the effect of material strength has been developed, whose result is also compared with the simple model and experimental data separately. The result shows that the effect of material strength is negligible when the peak value of current is far larger than the critical current, while the effect is remarkable when the peak value is similar to the critical current.
The electromagnetic driven solid liner implosion is one of the high energy density physics (HEDP) experimental techniques. Because of the metal strength, there exists a threshold for driven pressure where plastic flow just begins. And the plastic work that will turn to the internal energy of the metal liner should decrease the kinetic energy of liner, which of course will affect the implosion of the solid liner. The critical current has been found via the elastic-plastic analysis of cylindrical symmetry issue. The zero-dimension (0D) simulation considering the effect of material strength has been developed, whose result is also compared with the simple model and experimental data separately. The result shows that the effect of material strength is negligible when the peak value of current is far larger than the critical current, while the effect is remarkable when the peak value is similar to the critical current.
2016,
28: 045101.
doi: 10.11884/HPLPB201628.125101
Abstract:
In the dielectric wall accelerator (DWA), the intensity and the distribution of the axial and radial electric fields generated by the electrode structure are obviously different. In order to enhance the axial accelerating field, improve the accelerating gradient and suppress the beam profile expansion caused by the radial electric field, metal grids are embedded in between each accelerating unit. Electromagnetic simulation software based on particle-in-cell method is used to numerically simulate structures with and without metal grids, and to analyze the distribution of electric field as well as the change of the beam profile under different structures. The experimental results agree well with the simulation outcome, which demonstrate that the DWA with the metal grid structure has stronger and more uniform axial accelerating field than the DWA without metal grids. Furthermore, for the metal grid structure, the radial electric field is suppressed efficiently and the radial divergence of the accelerated particle beam in free drift space is improved.
In the dielectric wall accelerator (DWA), the intensity and the distribution of the axial and radial electric fields generated by the electrode structure are obviously different. In order to enhance the axial accelerating field, improve the accelerating gradient and suppress the beam profile expansion caused by the radial electric field, metal grids are embedded in between each accelerating unit. Electromagnetic simulation software based on particle-in-cell method is used to numerically simulate structures with and without metal grids, and to analyze the distribution of electric field as well as the change of the beam profile under different structures. The experimental results agree well with the simulation outcome, which demonstrate that the DWA with the metal grid structure has stronger and more uniform axial accelerating field than the DWA without metal grids. Furthermore, for the metal grid structure, the radial electric field is suppressed efficiently and the radial divergence of the accelerated particle beam in free drift space is improved.
2016,
28: 045102.
doi: 10.11884/HPLPB201628.125102
Abstract:
An integrated monitoring system of power supply in the CSRm is designed to reconstruct the original monitoring system. The system is based on the LabVIEW software platform and uses the PXI -6133 multi-function data acquisition card of NI. The C/S mode is adopted to build the system. The programs in the front -end servers acquire data from the power supply and process the data. The processed data will be transmitted to the client with the DataSocket Transmit Protocol. The programs in the client can set the parameters of the power supplies and receive, display the data. According to the test results, the system is a stable and reliable system with a simple, flexible and manageable operation interface and it has fulfilled the requirements of controlling beam of CSRm.
An integrated monitoring system of power supply in the CSRm is designed to reconstruct the original monitoring system. The system is based on the LabVIEW software platform and uses the PXI -6133 multi-function data acquisition card of NI. The C/S mode is adopted to build the system. The programs in the front -end servers acquire data from the power supply and process the data. The processed data will be transmitted to the client with the DataSocket Transmit Protocol. The programs in the client can set the parameters of the power supplies and receive, display the data. According to the test results, the system is a stable and reliable system with a simple, flexible and manageable operation interface and it has fulfilled the requirements of controlling beam of CSRm.
2016,
28: 045103.
doi: 10.11884/HPLPB201628.125103
Abstract:
Peking University is designing a superconducting taper-type half-wave resonator (HWR) with frequency of 162.5 MHz and of 0.09 for high current proton beam (about 100 mA) and deuteron beam (about 50 mA) acceleration. For this kind of SRF cavity, mechanical analysis is important to predict the frequency shift caused by the cavity deformation. ANSYS codes are used to analyse the frequency shift caused by helium bath pressure and Lorentz force, and the tuning range. Simulation results show that this HWR cavity has pressure sensitivity as low as 31.1 Hz/kPa and Lorentz force detuning coefficient of －0.41 Hz/(MVm-1)2. The tuning range of the cavity is 177 kHz which is wide enough for compensating the possible frequency shift. The mechanical property of the cavity permits the cavitys stable operation.
Peking University is designing a superconducting taper-type half-wave resonator (HWR) with frequency of 162.5 MHz and of 0.09 for high current proton beam (about 100 mA) and deuteron beam (about 50 mA) acceleration. For this kind of SRF cavity, mechanical analysis is important to predict the frequency shift caused by the cavity deformation. ANSYS codes are used to analyse the frequency shift caused by helium bath pressure and Lorentz force, and the tuning range. Simulation results show that this HWR cavity has pressure sensitivity as low as 31.1 Hz/kPa and Lorentz force detuning coefficient of －0.41 Hz/(MVm-1)2. The tuning range of the cavity is 177 kHz which is wide enough for compensating the possible frequency shift. The mechanical property of the cavity permits the cavitys stable operation.
2016,
28: 045104.
doi: 10.11884/HPLPB201628.125104
Abstract:
The pulsed high-current beams in Linear Induction Accelerator required by radiography gain their energy from the induction electric field generated at the acceleration gap. Beam loading effect determines that particles at different longitudinal position within a bunch get unequal gain of energy: particles at the beam head and tail have their energy increase faster than those at the main part, which consequently results in an energy spread increase. Since the first observations, significant efforts have been made to measure and restrain this energy spread growth. In this paper, a new method is proposed to mitigate the energy spread growth through regulating the energy gain of particles within a bunch by cell-timing asynchronization. Initial results from experiments on the accelerator show that the beam energy spread can be effectively controlled with this method.
The pulsed high-current beams in Linear Induction Accelerator required by radiography gain their energy from the induction electric field generated at the acceleration gap. Beam loading effect determines that particles at different longitudinal position within a bunch get unequal gain of energy: particles at the beam head and tail have their energy increase faster than those at the main part, which consequently results in an energy spread increase. Since the first observations, significant efforts have been made to measure and restrain this energy spread growth. In this paper, a new method is proposed to mitigate the energy spread growth through regulating the energy gain of particles within a bunch by cell-timing asynchronization. Initial results from experiments on the accelerator show that the beam energy spread can be effectively controlled with this method.
2016,
28: 045105.
doi: 10.11884/HPLPB201628.125105
Abstract:
The three cavities dielectric wall proton accelerator is systemically simulated by the self-developed 3D particle simulation software. On this basis, the transit time of protons in three cavities shall be calculated and the timing optimization design between cavities shall be achieved. The impressed voltage peak value is 100 kV. The width at top is 1ns and it is 10 ns at half maximum. The thickness of insulation micro reactor is 2.0 cm. The proton initial energy is 40 keV. The tungsten mesh is added to accelerating electrode. The simulation results are the following: When the voltage lasts 6.5 ns, the H+ which goes into high insulation gradient material shall get a maximum 90.84% acceleration efficiency while passing the first cavity, and the corresponding transit time is 5.668 ns. When the voltage triggers in the second cavity 4.5 ns behinds the first cavity, the H+ shall get a maximum 94.77% acceleration efficiency while passing the third cavity, and the corresponding transit time is 3.545 ns. When the voltage triggers in the third cavity 3.0 ns behinds the second cavity, the H+ shall get a maximum 97.30% acceleration efficiency while passing the second cavity, and the corresponding transit time is 3.018 ns. The total time of the maximum energy H+ transiting the three cavities is 12.231 ns. The acceleration efficiency of total H+ is 94.31%. When the proton beam center enters the first cavity and falls behind the pulse voltage trigger in 6.5 ns, with the delay time between first and second cavities, the second and third cavities are 4.5 ns and 3.0 ns respectively. The H+ of proton beams whose lengths are 2.5 ns and 4.0 ns shall be accelerated above 90% and 80% respectively.
The three cavities dielectric wall proton accelerator is systemically simulated by the self-developed 3D particle simulation software. On this basis, the transit time of protons in three cavities shall be calculated and the timing optimization design between cavities shall be achieved. The impressed voltage peak value is 100 kV. The width at top is 1ns and it is 10 ns at half maximum. The thickness of insulation micro reactor is 2.0 cm. The proton initial energy is 40 keV. The tungsten mesh is added to accelerating electrode. The simulation results are the following: When the voltage lasts 6.5 ns, the H+ which goes into high insulation gradient material shall get a maximum 90.84% acceleration efficiency while passing the first cavity, and the corresponding transit time is 5.668 ns. When the voltage triggers in the second cavity 4.5 ns behinds the first cavity, the H+ shall get a maximum 94.77% acceleration efficiency while passing the third cavity, and the corresponding transit time is 3.545 ns. When the voltage triggers in the third cavity 3.0 ns behinds the second cavity, the H+ shall get a maximum 97.30% acceleration efficiency while passing the second cavity, and the corresponding transit time is 3.018 ns. The total time of the maximum energy H+ transiting the three cavities is 12.231 ns. The acceleration efficiency of total H+ is 94.31%. When the proton beam center enters the first cavity and falls behind the pulse voltage trigger in 6.5 ns, with the delay time between first and second cavities, the second and third cavities are 4.5 ns and 3.0 ns respectively. The H+ of proton beams whose lengths are 2.5 ns and 4.0 ns shall be accelerated above 90% and 80% respectively.
2016,
28: 045106.
doi: 10.11884/HPLPB201628.125106
Abstract:
The X-ray spot size is a critical parameter for flash radiography facility which degrades resolution in the flash radiography. It is difficult to measure the X-ray spot size in the condition of intense radiation and its penetrability. This paper describes a rollbar used to measure the X-ray focal spot size. The edge spread function(ESF), line spread function(LSF) and modulation transfer function(MTF) of the X-ray spot are obtained from the rollbar image data, and the X-ray spot size is determined by the MTF. In the experiment of Dragon-Ⅱ linear induction accelerator downstream and target, the X-ray spot size is measured and the results are analyzed.
The X-ray spot size is a critical parameter for flash radiography facility which degrades resolution in the flash radiography. It is difficult to measure the X-ray spot size in the condition of intense radiation and its penetrability. This paper describes a rollbar used to measure the X-ray focal spot size. The edge spread function(ESF), line spread function(LSF) and modulation transfer function(MTF) of the X-ray spot are obtained from the rollbar image data, and the X-ray spot size is determined by the MTF. In the experiment of Dragon-Ⅱ linear induction accelerator downstream and target, the X-ray spot size is measured and the results are analyzed.
2016,
28: 045107.
doi: 10.11884/HPLPB201628.125107
Abstract:
In this article the Penning-type negative hydrogen ion source of 11 MeV compact cyclotron is studied. This ion source works in arc-mode. By changing the magnetic field strength, the impact of the magnetic field on ion sources work situation is analyzed. These issues are analyzed in the article: the mechanical properties of sustained discharge in the ion source, the impedance change of the ion source when the magnetic field varies, abnormal glow observed at the extraction slit. In this experiment, when hydrogen flow is stabled at 6 mL/min, changing the magnetic strength will influence Penning discharge. The result indicates that at strong magnetic field condition, the plasma conductivity almost does not change; but when the magnetic strength gets weak (less than 0.15 T), the plasma resistivity will increase rapidly, and there is a fierce discharge/glow of plasma brightening rapidly in this condition. Some inspiration in the design of PIG source are got from this experiment, and we are trying to analyze the probable microcosmic physics mechanism of this phenomenon in the discussion.
In this article the Penning-type negative hydrogen ion source of 11 MeV compact cyclotron is studied. This ion source works in arc-mode. By changing the magnetic field strength, the impact of the magnetic field on ion sources work situation is analyzed. These issues are analyzed in the article: the mechanical properties of sustained discharge in the ion source, the impedance change of the ion source when the magnetic field varies, abnormal glow observed at the extraction slit. In this experiment, when hydrogen flow is stabled at 6 mL/min, changing the magnetic strength will influence Penning discharge. The result indicates that at strong magnetic field condition, the plasma conductivity almost does not change; but when the magnetic strength gets weak (less than 0.15 T), the plasma resistivity will increase rapidly, and there is a fierce discharge/glow of plasma brightening rapidly in this condition. Some inspiration in the design of PIG source are got from this experiment, and we are trying to analyze the probable microcosmic physics mechanism of this phenomenon in the discussion.
2016,
28: 049001.
doi: 10.11884/HPLPB201628.129001
Abstract:
Composite electro-thermal chemical explosion (CETCE) was used to generate strong shock waves (SWs). This paper introduces the mechanism and effects of SWs generated by CETCE on reservoir stimulation and gives the discharge parameters and discharge load structure used to ignite energetic materials (EMs). The SW fracturing effects experiments were carried out. The dynamic strain and desorption related parameters, including porosity, permeability, strengths of extension and compression were measured and compared with those before the shock experiments. The results show that, the SWs generated by CETCE can generate the dynamic strain of 1000-1500, and visual cracks appear on and in the samples. The average porosity of sample increases from 15.24% to 15.62%, average permeability increases from 1.749 0910-3m2 to 2.467 0810-3 m2, and strengths of extension, compression and shear decrease by about 30% overall.
Composite electro-thermal chemical explosion (CETCE) was used to generate strong shock waves (SWs). This paper introduces the mechanism and effects of SWs generated by CETCE on reservoir stimulation and gives the discharge parameters and discharge load structure used to ignite energetic materials (EMs). The SW fracturing effects experiments were carried out. The dynamic strain and desorption related parameters, including porosity, permeability, strengths of extension and compression were measured and compared with those before the shock experiments. The results show that, the SWs generated by CETCE can generate the dynamic strain of 1000-1500, and visual cracks appear on and in the samples. The average porosity of sample increases from 15.24% to 15.62%, average permeability increases from 1.749 0910-3m2 to 2.467 0810-3 m2, and strengths of extension, compression and shear decrease by about 30% overall.
