Email alert
RSS2016 Vol. 28, No. 07
Recommend Articles
Display Method:
2016,
28: 070201.
doi: 10.11884/HPLPB201628.070201
Abstract:
Along with the development of high energy or high power lasers, especially laser weapon and lasers for controlled nuclear fusion, the laser induced damage threshold of the optical films gradually becomes the bottleneck against the development of the lasers, which is of considerable interest from the world. Laser induced damage mechanism of optical films, test flat and method for laser induced damage threshold were expatiated. The development of researches on the technologies and methods for laser damage resistance of optical films at home and abroad, which included ion beam pretreatment, ion beam or anneal treatment, pretest coating with the materials of high refractive index and so on, were analyzed. The pulsed laser deposition with magnetic filter technology was emphasized in the expectation, and the atom layer deposition was advised to accelerate to develop, which supplied the theoretic base to improve the laser damage resistance of optical films to settle for current requirements.
Along with the development of high energy or high power lasers, especially laser weapon and lasers for controlled nuclear fusion, the laser induced damage threshold of the optical films gradually becomes the bottleneck against the development of the lasers, which is of considerable interest from the world. Laser induced damage mechanism of optical films, test flat and method for laser induced damage threshold were expatiated. The development of researches on the technologies and methods for laser damage resistance of optical films at home and abroad, which included ion beam pretreatment, ion beam or anneal treatment, pretest coating with the materials of high refractive index and so on, were analyzed. The pulsed laser deposition with magnetic filter technology was emphasized in the expectation, and the atom layer deposition was advised to accelerate to develop, which supplied the theoretic base to improve the laser damage resistance of optical films to settle for current requirements.
2016,
28: 071001.
doi: 10.11884/HPLPB201628.071001
Abstract:
An optical beam energy distribution measuring method for nanosecond pulse laser is discussed. A kind of auto tracking integral mode is adopted for the method. By using forecast circuit, the pulse photocurrent is accumulated and held. The integral photocurrent is sampled by a low speed A/D converter. Thus, a high sampling rate can be got. The method is used successfully for a laser array target for testing high power energy beam distribution, and fit for testing the pulse laser with frequency from 5 Hz to 1 kHz, pulse width from 10 ns to 200 ns.
An optical beam energy distribution measuring method for nanosecond pulse laser is discussed. A kind of auto tracking integral mode is adopted for the method. By using forecast circuit, the pulse photocurrent is accumulated and held. The integral photocurrent is sampled by a low speed A/D converter. Thus, a high sampling rate can be got. The method is used successfully for a laser array target for testing high power energy beam distribution, and fit for testing the pulse laser with frequency from 5 Hz to 1 kHz, pulse width from 10 ns to 200 ns.
2016,
28: 071002.
doi: 10.11884/HPLPB201628.071002
Abstract:
Surface heat and water vapour fluxes have an important and extensive influence on global climate change and atmospheric circulation, while Monin-Obukhov(M-O) similarity function plays an important role in calculating surface layer heat and water vapour fluxes and it is an essential factor in estimation model of atmospheric optical turbulence. Therefore, it is necessary and urgent to propose a reasonable, scientific and effective similarity function. The meteorological datasets at the 35 m tower in the western suburbs of Hefei was analysed and a new set of M-O similarity functions are fitted by use of non-linear least squares method, which shows good consistency with the previous similarity functions. At the same time, the functions were applied to estimate atmospheric optical turbulence, the estimated values have a good agreement with the measured values. The analysis results show that under stable and very unstable conditions, the functions are similar, however, this similarity breaks down weakly unstable conditions.
Surface heat and water vapour fluxes have an important and extensive influence on global climate change and atmospheric circulation, while Monin-Obukhov(M-O) similarity function plays an important role in calculating surface layer heat and water vapour fluxes and it is an essential factor in estimation model of atmospheric optical turbulence. Therefore, it is necessary and urgent to propose a reasonable, scientific and effective similarity function. The meteorological datasets at the 35 m tower in the western suburbs of Hefei was analysed and a new set of M-O similarity functions are fitted by use of non-linear least squares method, which shows good consistency with the previous similarity functions. At the same time, the functions were applied to estimate atmospheric optical turbulence, the estimated values have a good agreement with the measured values. The analysis results show that under stable and very unstable conditions, the functions are similar, however, this similarity breaks down weakly unstable conditions.
2016,
28: 071003.
doi: 10.11884/HPLPB201628.071003
Abstract:
The hazardous exhaust gases, such as chlorine and iodine which are emitted from chemical oxygen-iodine laser (COIL), are harmful to air quality and personnel health in workplace. In this paper, based on the Gauss point source diffusion mode, exhaust gas diffusion model of COIL is established in the light wind or windless conditions. During the 15 minutes operating period of COIL, chlorine and iodine are accumulated in the air. The spatial distribution of concentration at the height of 1.5 m is calculated at the distance of 500 m away from the laser. Five sampling points were selected according to the spatial distribution of the pollutants concentration. In the measurement, Chlorine and iodine were collected simultaneously by using sodium sulfite solution as absorber. The concentrations of Cl- and I- in the absorption solution were measured by ion chromatography. The results show that the maximum concentration of chlorine was 0.200 mg/m3 in situ and the iodine concentration was under the detection limit of 0.030 mg/m3. Both of them are much less than the allowed concentration limit of harmful materials (1 mg/m3) specified in national occupational health standard.
The hazardous exhaust gases, such as chlorine and iodine which are emitted from chemical oxygen-iodine laser (COIL), are harmful to air quality and personnel health in workplace. In this paper, based on the Gauss point source diffusion mode, exhaust gas diffusion model of COIL is established in the light wind or windless conditions. During the 15 minutes operating period of COIL, chlorine and iodine are accumulated in the air. The spatial distribution of concentration at the height of 1.5 m is calculated at the distance of 500 m away from the laser. Five sampling points were selected according to the spatial distribution of the pollutants concentration. In the measurement, Chlorine and iodine were collected simultaneously by using sodium sulfite solution as absorber. The concentrations of Cl- and I- in the absorption solution were measured by ion chromatography. The results show that the maximum concentration of chlorine was 0.200 mg/m3 in situ and the iodine concentration was under the detection limit of 0.030 mg/m3. Both of them are much less than the allowed concentration limit of harmful materials (1 mg/m3) specified in national occupational health standard.
2016,
28: 071004.
doi: 10.11884/HPLPB201628.071004
Abstract:
Jet singlet oxygen generator is the most stable energy generating device for the chemical oxygen iodine laser. The three dimensional simulation of the jet chemical oxygen iodine laser is presented, which shows the structure of flow field in the reactor and the distribution of the components. It is pointed out that arrangement of liquid jets influences the operation of jet singlet oxygen generator under the same specific surface area. Moreover, the jet singlet oxygen generator with two gas entrances has a lower flow channel resistance compared to that with single gas entrance under the condition of the same flow. These results are meaningful for further optimization of jet singlet oxygen generator.
Jet singlet oxygen generator is the most stable energy generating device for the chemical oxygen iodine laser. The three dimensional simulation of the jet chemical oxygen iodine laser is presented, which shows the structure of flow field in the reactor and the distribution of the components. It is pointed out that arrangement of liquid jets influences the operation of jet singlet oxygen generator under the same specific surface area. Moreover, the jet singlet oxygen generator with two gas entrances has a lower flow channel resistance compared to that with single gas entrance under the condition of the same flow. These results are meaningful for further optimization of jet singlet oxygen generator.
2016,
28: 071005.
doi: 10.11884/HPLPB201628.071005
Abstract:
The influence of laser shaping on illumination uniformity and size with or without turbulence is analyzed, and beam intercept ratio on illumination uniformity is also analyzed using a self-developed laser-simulation-software called Easylaser. The results show that illumination uniformity is improved and illumination size can be adjusted by laser shaping even on the condition of turbulence. Then the effects of changing beam quality and laser shaping on illumination uniformity in turbulence are compared. The illumination uniformity with laser shaping is better than that with changing beam quality in weak turbulence.
The influence of laser shaping on illumination uniformity and size with or without turbulence is analyzed, and beam intercept ratio on illumination uniformity is also analyzed using a self-developed laser-simulation-software called Easylaser. The results show that illumination uniformity is improved and illumination size can be adjusted by laser shaping even on the condition of turbulence. Then the effects of changing beam quality and laser shaping on illumination uniformity in turbulence are compared. The illumination uniformity with laser shaping is better than that with changing beam quality in weak turbulence.
2016,
28: 071006.
doi: 10.11884/HPLPB201628.071006
Abstract:
In order to improve the efficiency of fluid jet polishing (FJP), the rectangle-nozzle structure was proposed to improve the removal efficiency in parallel. According to principles of fluid dynamics, the flow field characteristic of rectangle-nozzle structure was analyzed theoretically and the flow field distribution was calculated. Based on jet removal theory, the theoretical material removal models of rectangle-nozzle model were established, and removal distributions were calculated and compared. The relationship between rectangle-nozzle structure parameters and removal was analyzed in detail. Based on above results, the rectangle-nozzle was optimized. The results show that when the rectangle-nozzle length-width ratio be controlled to 10 or so can obtain better removal effect.
In order to improve the efficiency of fluid jet polishing (FJP), the rectangle-nozzle structure was proposed to improve the removal efficiency in parallel. According to principles of fluid dynamics, the flow field characteristic of rectangle-nozzle structure was analyzed theoretically and the flow field distribution was calculated. Based on jet removal theory, the theoretical material removal models of rectangle-nozzle model were established, and removal distributions were calculated and compared. The relationship between rectangle-nozzle structure parameters and removal was analyzed in detail. Based on above results, the rectangle-nozzle was optimized. The results show that when the rectangle-nozzle length-width ratio be controlled to 10 or so can obtain better removal effect.
2016,
28: 072001.
doi: 10.11884/HPLPB201628.072001
Abstract:
Characteristics of the Kelvin-Helmholtz (KH) instability of the interfaces formed by two semi-infinitely distributed fluids and one interlayer were studied. It was found that the coupling effects between the interfaces should be considered if the interlayer thickness was less than 0.5 times of the disturbation wavelength. And the degenerate modes could be produced in the situation with proper parameters.
Characteristics of the Kelvin-Helmholtz (KH) instability of the interfaces formed by two semi-infinitely distributed fluids and one interlayer were studied. It was found that the coupling effects between the interfaces should be considered if the interlayer thickness was less than 0.5 times of the disturbation wavelength. And the degenerate modes could be produced in the situation with proper parameters.
2016,
28: 072002.
doi: 10.11884/HPLPB201628.072002
Abstract:
The cold drawing of ultrafine Ni80Cr20 alloy wire often presents a regular three-dimensional helical crimp state. The effects of the drawing angle, working ratio, drawing speed and sizing section length on the curvature of NiCr alloy wire were studied. The NiCr ultrafine wire single-die cold drawing process was developed. The results show that with the increase of the drawing angle, the ultrafine wire curvature gradually increases; when drawing angle is 17, the curvature of the wire does not change significantly with increasing the working ratio, and it is about 0.56 mm-1. However，when the drawing angle is 0, its curvature gradually increases with the working ratio; when the drawing speed is less than 10 mmin-1, the curvature gradually increases, however, when the drawing speed is between 10 mmin-1 and 30 mmin-1, the increasing trend becomes slower; but it has a downward trend when the drawing speed is more than 30 mmin-1; meanwhile, with the sizing section length increases, the curvature value decreases. Analysis suggests that the reason why ultrafine wire crimp is that NiCr ultrafine wire surface additional shear deformation produced by cold drawing and flow rate inconformity of shear layer，meanwhile, the greater curvature, the greater residual stress. To reduce the inhomogeneous deformation of the ultrafine wire, the cold drawing process should use 0 to draw, the drawing speed should be 10 m min-1, the sizing zone length of diamond die should is 60% of diameter of die sizing area.
The cold drawing of ultrafine Ni80Cr20 alloy wire often presents a regular three-dimensional helical crimp state. The effects of the drawing angle, working ratio, drawing speed and sizing section length on the curvature of NiCr alloy wire were studied. The NiCr ultrafine wire single-die cold drawing process was developed. The results show that with the increase of the drawing angle, the ultrafine wire curvature gradually increases; when drawing angle is 17, the curvature of the wire does not change significantly with increasing the working ratio, and it is about 0.56 mm-1. However，when the drawing angle is 0, its curvature gradually increases with the working ratio; when the drawing speed is less than 10 mmin-1, the curvature gradually increases, however, when the drawing speed is between 10 mmin-1 and 30 mmin-1, the increasing trend becomes slower; but it has a downward trend when the drawing speed is more than 30 mmin-1; meanwhile, with the sizing section length increases, the curvature value decreases. Analysis suggests that the reason why ultrafine wire crimp is that NiCr ultrafine wire surface additional shear deformation produced by cold drawing and flow rate inconformity of shear layer，meanwhile, the greater curvature, the greater residual stress. To reduce the inhomogeneous deformation of the ultrafine wire, the cold drawing process should use 0 to draw, the drawing speed should be 10 m min-1, the sizing zone length of diamond die should is 60% of diameter of die sizing area.
2016,
28: 072003.
doi: 10.11884/HPLPB201628.072003
Abstract:
Interferograms of laser-induced epoxy fiber reinforced polymer plasmas are obtained through a Mach-Zehnder interferometry system. An improved digital double-exposure Fourier method is applied to extract initial wrapped phases from interferograms, and then an improved phase unwrapping algorithm based on a mask and a branch-cut method is proposed to solve the problem of phase unwrapping. After the inverse Abel transformation of the unwrapped phase, spatial distributions of the electron density of laser-induced epoxy fiber reinforced polymer plasma at various delays are acquired. Results show that the measured electron density of the plasma is mainly distributed on the order of 1018 cm-3. The experiment also indicates that the total amount of laser plasma electrons changes slightly within the recorded time and the change of the electron density is approximately inversely proportional to the change of the plasma volume.
Interferograms of laser-induced epoxy fiber reinforced polymer plasmas are obtained through a Mach-Zehnder interferometry system. An improved digital double-exposure Fourier method is applied to extract initial wrapped phases from interferograms, and then an improved phase unwrapping algorithm based on a mask and a branch-cut method is proposed to solve the problem of phase unwrapping. After the inverse Abel transformation of the unwrapped phase, spatial distributions of the electron density of laser-induced epoxy fiber reinforced polymer plasma at various delays are acquired. Results show that the measured electron density of the plasma is mainly distributed on the order of 1018 cm-3. The experiment also indicates that the total amount of laser plasma electrons changes slightly within the recorded time and the change of the electron density is approximately inversely proportional to the change of the plasma volume.
2016,
28: 072004.
doi: 10.11884/HPLPB201628.072004
Abstract:
A physical model of heating and ignition of magnetized plasma is presented, which is analyzed by 1D 3T MHD Lagrange code in the metal liner driven by pulsed-power. The analysis includes the procedure of metal liner implosion driven by pulse, the impact of different driving source within magnetized target warming on, the effects of embedded magnetic field and the pre-heating temperature for magnetized plasma warming during Z-pinch process, the initial parameters for ignition and energy output. The physical mechanism is introduced in which the magnetic field increases the energy deposition and reduces energy loss through heat conduction electron and ionization. The simulation indicates that a strong magnetic field (over 1000 T) is produced during the implosion procedure and obvious heating-up (about 4 keV) can be acquired by selecting 5 T embedded magnetic field and 250 eV preheat temperature for the target. We get the order of one thousand T magnetic field and the energy output about a hundred kJ/mm level when the initial parameters, including embedded magnetic field, pre-heating temperature, fuel density, liner scale, pulse amplitude and loading time, are under certain conditions.
A physical model of heating and ignition of magnetized plasma is presented, which is analyzed by 1D 3T MHD Lagrange code in the metal liner driven by pulsed-power. The analysis includes the procedure of metal liner implosion driven by pulse, the impact of different driving source within magnetized target warming on, the effects of embedded magnetic field and the pre-heating temperature for magnetized plasma warming during Z-pinch process, the initial parameters for ignition and energy output. The physical mechanism is introduced in which the magnetic field increases the energy deposition and reduces energy loss through heat conduction electron and ionization. The simulation indicates that a strong magnetic field (over 1000 T) is produced during the implosion procedure and obvious heating-up (about 4 keV) can be acquired by selecting 5 T embedded magnetic field and 250 eV preheat temperature for the target. We get the order of one thousand T magnetic field and the energy output about a hundred kJ/mm level when the initial parameters, including embedded magnetic field, pre-heating temperature, fuel density, liner scale, pulse amplitude and loading time, are under certain conditions.
2016,
28: 073001.
doi: 10.11884/HPLPB201628.073001
Abstract:
Based on the actual structure of an IGBT module, the finite element equivalent thermal analysis model and the double thermal resistance model of the IGBT switch power supply are established. The total loss of the module is calculated by using the voltage-current curve and temperature measurement experiment results under the circumstance of actual work of the switching power supply. The transient thermal resistance which is the main parameter of the thermal characteristics is simulated. By comparing with the measured thermal resistance curve provided by the manufacturers data sheet, the consistence of both curves indicates that the finite element equivalent thermal analysis model is reasonable. The thermal distribution and chip junction temperature of the IGBT module are achieved under actual working state by experimental comparison and analysis, based on the steady state thermal simulation of the finite element analysis model and double thermal resistance model. The advantages and disadvantages of double thermal resistance model are analyzed, and an improvement program is proposed.
Based on the actual structure of an IGBT module, the finite element equivalent thermal analysis model and the double thermal resistance model of the IGBT switch power supply are established. The total loss of the module is calculated by using the voltage-current curve and temperature measurement experiment results under the circumstance of actual work of the switching power supply. The transient thermal resistance which is the main parameter of the thermal characteristics is simulated. By comparing with the measured thermal resistance curve provided by the manufacturers data sheet, the consistence of both curves indicates that the finite element equivalent thermal analysis model is reasonable. The thermal distribution and chip junction temperature of the IGBT module are achieved under actual working state by experimental comparison and analysis, based on the steady state thermal simulation of the finite element analysis model and double thermal resistance model. The advantages and disadvantages of double thermal resistance model are analyzed, and an improvement program is proposed.
2016,
28: 073002.
doi: 10.11884/HPLPB201628.073002
Abstract:
For high efficient EM simulating requirements around FLAPS-typed HPM transmitters based on spatial power combination techniques, integral equation methods (IE) accompanied with multi-scale geometrical and EM modeling techniques named MLFMA-MLACE are applied in this paper. The algorithms mainly concern multi-scale geometrical modeling for the designed project, MLFMA acceleration in macroscopical layer and adaptive MLACE acceleration in microcosmic layer. Through some primary applications in W-band FLAPS models, the precision of the combined methods is validated. Its applicativity, approximate level in detail, effects and computational cost are sufficiently analyzed. The results show that as to aspects of memory requirements and computational time, the combined technique has extremely evident advantage. Some discussions about future improvement are also given in this paper.
For high efficient EM simulating requirements around FLAPS-typed HPM transmitters based on spatial power combination techniques, integral equation methods (IE) accompanied with multi-scale geometrical and EM modeling techniques named MLFMA-MLACE are applied in this paper. The algorithms mainly concern multi-scale geometrical modeling for the designed project, MLFMA acceleration in macroscopical layer and adaptive MLACE acceleration in microcosmic layer. Through some primary applications in W-band FLAPS models, the precision of the combined methods is validated. Its applicativity, approximate level in detail, effects and computational cost are sufficiently analyzed. The results show that as to aspects of memory requirements and computational time, the combined technique has extremely evident advantage. Some discussions about future improvement are also given in this paper.
2016,
28: 073003.
doi: 10.11884/HPLPB201628.073003
Abstract:
Microwave vacuum devices are used in a wide variety of areas, such as radar, space technology, electron accelerators, free electron lasers. The cathodes, i.e. the electron sources, are the cores of high-power microwave sources. Their performances directly determine the output power, lifetime and other properties of the microwave sources. It is necessary to know the actual temperature of a thermionic cathode. The temperatures of an impregnated cathode, a coated cathode and a cathode side (molybdenum tube) have been tested by infrared thermometer, optical pyrometer and thermocouple thermometer (platinum and rhodium-platinum).The results show that the temperature of an impregnated cathode tested by infrared thermometer and optical pyrometer is similar to that by thermocouple thermometer, so the temperatures of impregnated cathode tested by infrared thermometer and optical pyrometer are very close to the actual temperature by thermocouple thermometer. The temperatures of coated cathode tested by infrared thermometer and optical pyrometer are lower than the actual temperature of the cathode tested by thermocouple thermometer about 50 ℃.The temperatures of the cathode side (molybdenum tube) tested by infrared thermometer and optical pyrometer are lower than the actual temperature of the cathode by thermocouple thermometer about 60 ℃. Since the physical and chemical changes arise on the cathode surface, the temperatures of the cathode surface tested by infrared thermometer and optical pyrometer increase about 30 ℃ heated at about 1150 ℃ within 100 min. These results will be affected by the molybdenum processing technology on the surface of the material, coating material, thickness of the film, the film density and other factors. Infrared thermometer and optical pyrometer are strongly dependent on the thermal radiation coefficient of the test surface, and it is very difficult to accurately obtain the thermal radiation coefficient of some materials.
Microwave vacuum devices are used in a wide variety of areas, such as radar, space technology, electron accelerators, free electron lasers. The cathodes, i.e. the electron sources, are the cores of high-power microwave sources. Their performances directly determine the output power, lifetime and other properties of the microwave sources. It is necessary to know the actual temperature of a thermionic cathode. The temperatures of an impregnated cathode, a coated cathode and a cathode side (molybdenum tube) have been tested by infrared thermometer, optical pyrometer and thermocouple thermometer (platinum and rhodium-platinum).The results show that the temperature of an impregnated cathode tested by infrared thermometer and optical pyrometer is similar to that by thermocouple thermometer, so the temperatures of impregnated cathode tested by infrared thermometer and optical pyrometer are very close to the actual temperature by thermocouple thermometer. The temperatures of coated cathode tested by infrared thermometer and optical pyrometer are lower than the actual temperature of the cathode tested by thermocouple thermometer about 50 ℃.The temperatures of the cathode side (molybdenum tube) tested by infrared thermometer and optical pyrometer are lower than the actual temperature of the cathode by thermocouple thermometer about 60 ℃. Since the physical and chemical changes arise on the cathode surface, the temperatures of the cathode surface tested by infrared thermometer and optical pyrometer increase about 30 ℃ heated at about 1150 ℃ within 100 min. These results will be affected by the molybdenum processing technology on the surface of the material, coating material, thickness of the film, the film density and other factors. Infrared thermometer and optical pyrometer are strongly dependent on the thermal radiation coefficient of the test surface, and it is very difficult to accurately obtain the thermal radiation coefficient of some materials.
2016,
28: 073004.
doi: 10.11884/HPLPB201628.073004
Abstract:
In order to improve the power capacity of the high power microwave (HPM) radiation antenna, a radiation antenna window with grading ring is designed. With grading ring in antenna window can avoid dielectric window breakdown effectively. Changing the electric field distribution of the dielectric window leads to the electron trajectory change. CST simulation shows that when the grading ring is perpendicular to electric field, it does not affect the radiation of the antenna. According to the output microwave characteristics (TM01 mode) of HPM device (BWO Backward-wave Oscillator), the BWO experiment shows that the width of the output microwave changes from 45 ns to 100 ns with a beam voltage of 3 MV, a beam current of 10 kA, and an efficiency of 30%.
In order to improve the power capacity of the high power microwave (HPM) radiation antenna, a radiation antenna window with grading ring is designed. With grading ring in antenna window can avoid dielectric window breakdown effectively. Changing the electric field distribution of the dielectric window leads to the electron trajectory change. CST simulation shows that when the grading ring is perpendicular to electric field, it does not affect the radiation of the antenna. According to the output microwave characteristics (TM01 mode) of HPM device (BWO Backward-wave Oscillator), the BWO experiment shows that the width of the output microwave changes from 45 ns to 100 ns with a beam voltage of 3 MV, a beam current of 10 kA, and an efficiency of 30%.
2016,
28: 073005.
doi: 10.11884/HPLPB201628.073005
Abstract:
The principle and design method of Denisov-type quasi-optical mode converter is investigated in detail. The operation process of the Denisov-type launcher is analyzed by applying the geometrical optics, and the Gaussian-like field distribution achieved on the waveguide wall is also derived. The method for designing a rippled-wall launcher is proposed on the basis of coupled mode theory. A simulation code for Denisov-type quasi-optical mode converter GQOMC-D is developed based on coupled mode theory, vector diffraction integration and physical optics, which is compared to the design parameters and experimental results reported in literature for its validity. According to this code, a Denisov-type quasi-optical mode converter used in 110 GHz TE22,6 mode gyrotron oscillators is designed. Simulation results indicate that a Gaussian-like beam is obtained at the output window with a scalar content of 98.4% and a conversion efficiency of 94.7%.
The principle and design method of Denisov-type quasi-optical mode converter is investigated in detail. The operation process of the Denisov-type launcher is analyzed by applying the geometrical optics, and the Gaussian-like field distribution achieved on the waveguide wall is also derived. The method for designing a rippled-wall launcher is proposed on the basis of coupled mode theory. A simulation code for Denisov-type quasi-optical mode converter GQOMC-D is developed based on coupled mode theory, vector diffraction integration and physical optics, which is compared to the design parameters and experimental results reported in literature for its validity. According to this code, a Denisov-type quasi-optical mode converter used in 110 GHz TE22,6 mode gyrotron oscillators is designed. Simulation results indicate that a Gaussian-like beam is obtained at the output window with a scalar content of 98.4% and a conversion efficiency of 94.7%.
2016,
28: 073101.
doi: 10.11884/HPLPB201628.073101
Abstract:
There are few papers about terahertz wave propagating in magnetized plasma. Adding constant magnetic field around space crafts and choosing terahertz wave as communication signal are two effective ways to solve the famous blackout problem. It is necessary to study the properties of terahertz wave propagation in magnetized plasma sheath. This paper has established the one-dimensional model to describe electromagnetic wave passing through the magnetized plasma sheath. A numerical analysis method is adopted to calculate the reflection coefficient, transmission coefficient and attenuation coefficient of the terahertz wave propagating in magnetized plasma sheath. The variations of the terahertz wave propagation properties with the terahertz wave frequency, plasma density, plasma collision frequency, the thickness of the plasma and magnetic field intensity are acquired. The simulation shows that the magnetic field effectively reduces the attenuation when the terahertz wave propagates in plasma sheath. Except the peak value of the attenuation, the value is less than 5 dB. This phenomenon shows that the communication blackout problem is solved effectively. The result can be used as reference for designing hypersonic vehicles with magnetic window antenna using terahertz wave as communication signal.
There are few papers about terahertz wave propagating in magnetized plasma. Adding constant magnetic field around space crafts and choosing terahertz wave as communication signal are two effective ways to solve the famous blackout problem. It is necessary to study the properties of terahertz wave propagation in magnetized plasma sheath. This paper has established the one-dimensional model to describe electromagnetic wave passing through the magnetized plasma sheath. A numerical analysis method is adopted to calculate the reflection coefficient, transmission coefficient and attenuation coefficient of the terahertz wave propagating in magnetized plasma sheath. The variations of the terahertz wave propagation properties with the terahertz wave frequency, plasma density, plasma collision frequency, the thickness of the plasma and magnetic field intensity are acquired. The simulation shows that the magnetic field effectively reduces the attenuation when the terahertz wave propagates in plasma sheath. Except the peak value of the attenuation, the value is less than 5 dB. This phenomenon shows that the communication blackout problem is solved effectively. The result can be used as reference for designing hypersonic vehicles with magnetic window antenna using terahertz wave as communication signal.
2016,
28: 073201.
doi: 10.11884/HPLPB201628.073201
Abstract:
The first step to the design of aircrafts is to determinate the initial lightning attachment points. In this paper, a fast numerical simulation method based on the stream-leader discharge theory is presented to simulate the initial lighting attachment point on the helicopter. Firstly, the size of the electrode, the distance between the helicopter and the boundary and other parameters are determined according to the test methods of the lightning attachment points in the SAE-ARP 5416A standard. Then, upward leader inception based on Beccera-Cooray criterion is used to analyze the tip of the main rotor and tail rotor , the head, and the horizontal tail of the UH-60 helicopter. Finally, finding the minimum electric field sustains the positive leader inception by continuously changing the potential of the electrode, which can provide basis to the analysis of the initial lightning attachment points. The simulation results show that the main rotor is most likely to be the lightning initial attachment point and the head is hard to be the lightning initial attachment point.
The first step to the design of aircrafts is to determinate the initial lightning attachment points. In this paper, a fast numerical simulation method based on the stream-leader discharge theory is presented to simulate the initial lighting attachment point on the helicopter. Firstly, the size of the electrode, the distance between the helicopter and the boundary and other parameters are determined according to the test methods of the lightning attachment points in the SAE-ARP 5416A standard. Then, upward leader inception based on Beccera-Cooray criterion is used to analyze the tip of the main rotor and tail rotor , the head, and the horizontal tail of the UH-60 helicopter. Finally, finding the minimum electric field sustains the positive leader inception by continuously changing the potential of the electrode, which can provide basis to the analysis of the initial lightning attachment points. The simulation results show that the main rotor is most likely to be the lightning initial attachment point and the head is hard to be the lightning initial attachment point.
2016,
28: 073202.
doi: 10.11884/HPLPB201628.073202
Abstract:
The vortex electromagnetic wave has a new degree of freedom named orbital angular momentum (OAM), which arises from the vortex phase term. Recently it has received intensive attention in the application to the wireless communication field. In radio waves, the array antenna is an effective method to generate vortex electromagnetic waves carrying orbital angular momentum. We proposed a new design of patch array antenna carrying orbital angular momentum at 6 GHz. In this design, eight proximity-fed circular patches arranged on a circle with equidistant space. By controlling the phase delay, we got OAM modes of quantum number 0, 1, 2, 3, 4, and obtained the vortex electromagnetic wave carrying orbital angular momentum. In addition, the appropriate array radius and feed transport line were two keys to generate good properties of vortex waves carrying orbital angular momentum.
The vortex electromagnetic wave has a new degree of freedom named orbital angular momentum (OAM), which arises from the vortex phase term. Recently it has received intensive attention in the application to the wireless communication field. In radio waves, the array antenna is an effective method to generate vortex electromagnetic waves carrying orbital angular momentum. We proposed a new design of patch array antenna carrying orbital angular momentum at 6 GHz. In this design, eight proximity-fed circular patches arranged on a circle with equidistant space. By controlling the phase delay, we got OAM modes of quantum number 0, 1, 2, 3, 4, and obtained the vortex electromagnetic wave carrying orbital angular momentum. In addition, the appropriate array radius and feed transport line were two keys to generate good properties of vortex waves carrying orbital angular momentum.
2016,
28: 075001.
doi: 10.11884/HPLPB201628.075001
Abstract:
The cascaded pulse power supply with the magnetic isolation is used to solve the problem of floating power supply of each cascaded unit. Its structure is compact and the trigger mode is simple and reliable. Using the trigger mode of magnetic coupling isolation can increase the tail branch in each concatenation unit simply and conveniently, reduce greatly the falling edge of output high voltage pulse, and improve the adaptability of cascade type pulse power. In this paper, a kind of 10 kV cascaded pulse power supply is developed. The rated working voltage of each cascaded unit is 1 kV for a total of 10 units. The voltage regulation range is 0-10 kV, the operating frequency is 1-10 kHz, the pulse current is 0-20 A, and the pulse width is 5-30 s.
The cascaded pulse power supply with the magnetic isolation is used to solve the problem of floating power supply of each cascaded unit. Its structure is compact and the trigger mode is simple and reliable. Using the trigger mode of magnetic coupling isolation can increase the tail branch in each concatenation unit simply and conveniently, reduce greatly the falling edge of output high voltage pulse, and improve the adaptability of cascade type pulse power. In this paper, a kind of 10 kV cascaded pulse power supply is developed. The rated working voltage of each cascaded unit is 1 kV for a total of 10 units. The voltage regulation range is 0-10 kV, the operating frequency is 1-10 kHz, the pulse current is 0-20 A, and the pulse width is 5-30 s.
2016,
28: 075002.
doi: 10.11884/HPLPB201628.075002
Abstract:
The high electromagnetic force produced by the pulse current is the main reason for the damage of pulse power cable, which also limits the current capacity of pulse power cable. We simulate the stress of the coaxial cable conductor layer, and discuss the cable conductor structures influence on the current capacity of pulse power cable. We example one kind of used coaxial cable, analyze the force of the outer conductor layer and the structure change tendency about the cable, and discuss the test result. Based on all of thoes, we research another structure type coaxial cable, and we believe that it has better capacity to oppose electromagnetic force. The experimental results show that the peak current of the new cable can achieve 208 kA, and the current capacity can achieve 6.9 kA/mm2, which can verify the superiority of the cable. Finally we provide a way to solve the problem of using too many cables in pulse power system.
The high electromagnetic force produced by the pulse current is the main reason for the damage of pulse power cable, which also limits the current capacity of pulse power cable. We simulate the stress of the coaxial cable conductor layer, and discuss the cable conductor structures influence on the current capacity of pulse power cable. We example one kind of used coaxial cable, analyze the force of the outer conductor layer and the structure change tendency about the cable, and discuss the test result. Based on all of thoes, we research another structure type coaxial cable, and we believe that it has better capacity to oppose electromagnetic force. The experimental results show that the peak current of the new cable can achieve 208 kA, and the current capacity can achieve 6.9 kA/mm2, which can verify the superiority of the cable. Finally we provide a way to solve the problem of using too many cables in pulse power system.
2016,
28: 075003.
doi: 10.11884/HPLPB201628.075003
Abstract:
The input power of the conventional constant current charging power supply increases with the increase of output voltage, and the input power drops to 0 immediately at the end of the charging, indicating that the conventional CCPS not only needs 2 times power of mean value from grid, but also causes the fluctuation of the grid voltage. Especially when the repetition of high power system is close to the grid frequency, it may cause the oscillation of the power grid, reduce its reliability and have influence on other equipment connected to the same grid. A topology with buffer energy storage is proposed, which keeps the input power of CCPS stable during the charging process. The stable value equals to the average power of whole charging process. The characteristics of series resonant circuit in discontinuous mode are fully used, there is no need of auxiliary converter, only with control of bidirectional switches. The buffer capacitor can be charged in the early stage gradually, and release the energy to the resonant circuit gradually in the later stage. At the starting and ending of charging, the energy in buffer capacitor keeps the same. The proposed topology is added to the DC-link based CCPS. The analysis and deduced process of control parameter are given. The experiment is carried out on a CCPS with 8 A output current and 5 kV output voltage. The experiment results show that at the same charging speed, the DC bus current is stable and is about 1/2 of the maximum value in conventional CCPS.
The input power of the conventional constant current charging power supply increases with the increase of output voltage, and the input power drops to 0 immediately at the end of the charging, indicating that the conventional CCPS not only needs 2 times power of mean value from grid, but also causes the fluctuation of the grid voltage. Especially when the repetition of high power system is close to the grid frequency, it may cause the oscillation of the power grid, reduce its reliability and have influence on other equipment connected to the same grid. A topology with buffer energy storage is proposed, which keeps the input power of CCPS stable during the charging process. The stable value equals to the average power of whole charging process. The characteristics of series resonant circuit in discontinuous mode are fully used, there is no need of auxiliary converter, only with control of bidirectional switches. The buffer capacitor can be charged in the early stage gradually, and release the energy to the resonant circuit gradually in the later stage. At the starting and ending of charging, the energy in buffer capacitor keeps the same. The proposed topology is added to the DC-link based CCPS. The analysis and deduced process of control parameter are given. The experiment is carried out on a CCPS with 8 A output current and 5 kV output voltage. The experiment results show that at the same charging speed, the DC bus current is stable and is about 1/2 of the maximum value in conventional CCPS.
2016,
28: 075004.
doi: 10.11884/HPLPB201628.075004
Abstract:
Based on the characteristics of the Si photoconductive semiconductor switch (PCSS) and the magnetic switch (MS), a new combined switch is developed. The combined switch integrates a traditional Si PCSS and a normal magnetic switch. Compared with normal magnetic switch, the combined switch can withstand a charge time of several tens microsecond and give an output voltage with several tens nanosecond rise time. The combined switch also can reduce the power of the laser for triggering the traditional single Si PCSS and then laser diode can be used. The traditional single Si PCSS and the combined switch were triggered by laser diode for comparison.
Based on the characteristics of the Si photoconductive semiconductor switch (PCSS) and the magnetic switch (MS), a new combined switch is developed. The combined switch integrates a traditional Si PCSS and a normal magnetic switch. Compared with normal magnetic switch, the combined switch can withstand a charge time of several tens microsecond and give an output voltage with several tens nanosecond rise time. The combined switch also can reduce the power of the laser for triggering the traditional single Si PCSS and then laser diode can be used. The traditional single Si PCSS and the combined switch were triggered by laser diode for comparison.
2016,
28: 075005.
doi: 10.11884/HPLPB201628.075005
Abstract:
When the gas switch discharges in the FLTD, the self-breakdown characteristic turns worse compared to individually discharging. To solve the problem, the electric field distribution of the switch which is influenced by the cable and the FLTD module is simulated and computed. The main reasons for the decline of the switch self-breakdown characteristic are analyzed. The experiments of both corona needle for voltage-balance and resistance for equalization are individually developed. The results are obtained for different length of the corona needle and variable values of resistance. The self-breakdown voltage of the switch is separately improved by 3.2% and 4.3% for the two types of equalization. The self-breakdown voltage is improved by 8.9% and the pre-fire probability is reduced by 60%, when all of the gas switches are equipped with equalization in the FLTD stage. The stability of the FLTD output current is obviously improved. The amplitude of the output current is improved by 8.1% and the standard deviation is reduced by 30.8%.
When the gas switch discharges in the FLTD, the self-breakdown characteristic turns worse compared to individually discharging. To solve the problem, the electric field distribution of the switch which is influenced by the cable and the FLTD module is simulated and computed. The main reasons for the decline of the switch self-breakdown characteristic are analyzed. The experiments of both corona needle for voltage-balance and resistance for equalization are individually developed. The results are obtained for different length of the corona needle and variable values of resistance. The self-breakdown voltage of the switch is separately improved by 3.2% and 4.3% for the two types of equalization. The self-breakdown voltage is improved by 8.9% and the pre-fire probability is reduced by 60%, when all of the gas switches are equipped with equalization in the FLTD stage. The stability of the FLTD output current is obviously improved. The amplitude of the output current is improved by 8.1% and the standard deviation is reduced by 30.8%.
2016,
28: 075006.
doi: 10.11884/HPLPB201628.075006
Abstract:
Surface flashover properties of polymer insulator are very closely related to its surface structure and morphology. To enhance the surface flashover voltage of polymer insulator, nano-SiO2/cross-linked polystyrene (CLPS) composites with modified surface structure of nano-sized cavities were developed by means of both free radical crosslinking copolymerization and surface erosion for the first time. The structures of SiO2/CLPS composites were characterized with Fourier transform infrared spectroscopy(FT-IR) and transmission electron microscopy(TEM). The results showed that nano-SiO2 particles with an average size of 20-50 nm were well dispersed in the cross-linked polystyrene matrix with excellent compatibility between the organic and inorganic components. The cavities with the same size as SiO2 particles could be formed in the surface of the polymer, and SiO2 particles in the inner layer would remain intact. The uniform cavities could be responsible for the improvement of surface flashover property of polymer insulator. The surface flashover voltages of the modified surface insulators were increased by 15%-20% by comparison with that of CLPS. It gives a novel way to develop high dielectric polymer insulator.
Surface flashover properties of polymer insulator are very closely related to its surface structure and morphology. To enhance the surface flashover voltage of polymer insulator, nano-SiO2/cross-linked polystyrene (CLPS) composites with modified surface structure of nano-sized cavities were developed by means of both free radical crosslinking copolymerization and surface erosion for the first time. The structures of SiO2/CLPS composites were characterized with Fourier transform infrared spectroscopy(FT-IR) and transmission electron microscopy(TEM). The results showed that nano-SiO2 particles with an average size of 20-50 nm were well dispersed in the cross-linked polystyrene matrix with excellent compatibility between the organic and inorganic components. The cavities with the same size as SiO2 particles could be formed in the surface of the polymer, and SiO2 particles in the inner layer would remain intact. The uniform cavities could be responsible for the improvement of surface flashover property of polymer insulator. The surface flashover voltages of the modified surface insulators were increased by 15%-20% by comparison with that of CLPS. It gives a novel way to develop high dielectric polymer insulator.
2016,
28: 075007.
doi: 10.11884/HPLPB201628.075007
Abstract:
A resistive bolometer which is used to diagnose soft X-ray fluence is described. The bolometer is calibrated with Ohm heating. In the calibration scheme, heat loss into the substrate is considered with a simple one-dimensional heat conduction model. We utilize the bolometer to diagnose soft X-ray fluence of tungsten wire array Z-pinch experiments on PTS. Comparison of the bolometer measurements with a flat spectral response XRD (FSR-XRD) shows that the soft X-ray power and energy measurements from bolometers are reasonably consistent with that obtained by FSR-XRD.
A resistive bolometer which is used to diagnose soft X-ray fluence is described. The bolometer is calibrated with Ohm heating. In the calibration scheme, heat loss into the substrate is considered with a simple one-dimensional heat conduction model. We utilize the bolometer to diagnose soft X-ray fluence of tungsten wire array Z-pinch experiments on PTS. Comparison of the bolometer measurements with a flat spectral response XRD (FSR-XRD) shows that the soft X-ray power and energy measurements from bolometers are reasonably consistent with that obtained by FSR-XRD.
2016,
28: 075008.
doi: 10.11884/HPLPB201628.075008
Abstract:
A repetitive rate flash X-ray generator was developed recently to meet the demands in scientific research and industrial area. A repetitive pulsed power supply was fabricated with GaAs photo conductive semiconductor switches and stacked Blumlein pulse forming networks to drive industrial X-ray diode, and a novel X-ray diode was proposed with spoked metal ceramic flashover cathode. The results show that 2 pulse burst X rays were generated under 1 kHz frame rate with novel cathode, and the two power pulses of diode and X-ray signals were identical.
A repetitive rate flash X-ray generator was developed recently to meet the demands in scientific research and industrial area. A repetitive pulsed power supply was fabricated with GaAs photo conductive semiconductor switches and stacked Blumlein pulse forming networks to drive industrial X-ray diode, and a novel X-ray diode was proposed with spoked metal ceramic flashover cathode. The results show that 2 pulse burst X rays were generated under 1 kHz frame rate with novel cathode, and the two power pulses of diode and X-ray signals were identical.
2016,
28: 075009.
doi: 10.11884/HPLPB201628.075009
Abstract:
A multi-gap gas switch with corona discharge for voltage balance is developed. The self-breakdown characteristics of the switch at different gas pressures, the voltage-current characteristics of corona discharge, the needle erosion and the switch life time are studied respectively. The experiment results show that after conditioning the switch self-breakdown voltage relative standard deviation is less than 3.5%, the voltage balance has good effect. The voltage-current characteristics line of multi-gap corona discharge is similar to a parabola form. When the switch is pumped 400 kPa dry air and the work voltage is 100 kV, the switch lifetime can reach more 50 000 times, the jitter of the switch breakdown delay time is about 4.3 ns, the per fire probability of the switch can be lower than 110-4.
A multi-gap gas switch with corona discharge for voltage balance is developed. The self-breakdown characteristics of the switch at different gas pressures, the voltage-current characteristics of corona discharge, the needle erosion and the switch life time are studied respectively. The experiment results show that after conditioning the switch self-breakdown voltage relative standard deviation is less than 3.5%, the voltage balance has good effect. The voltage-current characteristics line of multi-gap corona discharge is similar to a parabola form. When the switch is pumped 400 kPa dry air and the work voltage is 100 kV, the switch lifetime can reach more 50 000 times, the jitter of the switch breakdown delay time is about 4.3 ns, the per fire probability of the switch can be lower than 110-4.
2016,
28: 075101.
doi: 10.11884/HPLPB201628.075101
Abstract:
A remote trigger-control system based on LabVIEW and PIC microcontroller is developed to control the repetitively pulsed intense-electron-beam accelerator charged by capacitive energy storage. This system employs an ordinary data-acquisition card and a microcontroller to realize complex circuit control and sequence control, with functions of signal collecting, data sheet calling, thyristor switch triggering and so on, to achieve the main purpose of controlling the charging of primary capacitance of transformer resonantly and stably. When the intense-electron-beam accelerator works repetitively with the control system, the voltage of the primary capacitance of transformer is tested to be consistent and stable, which shows that the control system can work stably and reliably with strong anti-interference ability.
A remote trigger-control system based on LabVIEW and PIC microcontroller is developed to control the repetitively pulsed intense-electron-beam accelerator charged by capacitive energy storage. This system employs an ordinary data-acquisition card and a microcontroller to realize complex circuit control and sequence control, with functions of signal collecting, data sheet calling, thyristor switch triggering and so on, to achieve the main purpose of controlling the charging of primary capacitance of transformer resonantly and stably. When the intense-electron-beam accelerator works repetitively with the control system, the voltage of the primary capacitance of transformer is tested to be consistent and stable, which shows that the control system can work stably and reliably with strong anti-interference ability.
2016,
28: 075102.
doi: 10.11884/HPLPB201628.075102
Abstract:
According to the principle of Cherenkov radiation (CR), the direction of CR light is strictly defined by the direction along which the charged particle moves. This angular orientation between particle and CR light can be utilized to measure and calculate beam divergence and its distribution. With multi Coulomb scatter and ionization with target material taken into account, this paper analyzed the Cherenkov effect and its application, created the simulating model with Mont-Carlo method, developed the computing code, and simulated the process of Cherenkov effects and inverse. The simulated result shows that the electron beam divergence and its distribution can be measured based on CR with an appropriate target. Simulation work put forward the appropriate conditions for the following measuring experiments and made a good reference for future work.
According to the principle of Cherenkov radiation (CR), the direction of CR light is strictly defined by the direction along which the charged particle moves. This angular orientation between particle and CR light can be utilized to measure and calculate beam divergence and its distribution. With multi Coulomb scatter and ionization with target material taken into account, this paper analyzed the Cherenkov effect and its application, created the simulating model with Mont-Carlo method, developed the computing code, and simulated the process of Cherenkov effects and inverse. The simulated result shows that the electron beam divergence and its distribution can be measured based on CR with an appropriate target. Simulation work put forward the appropriate conditions for the following measuring experiments and made a good reference for future work.
2016,
28: 075103.
doi: 10.11884/HPLPB201628.075103
Abstract:
Three kicker assemblies including eight pulsed magnets will be used in the rapid circle synchrotron of China Spallation Neutron Source. Magnetic field simulation and structural design of the kicker magnet is presented. The results of OPERA-3D simulation show that the central field integral of magnets meet the physical requirements by choosing a suitable magnet coil structure. The field uniformity in 60% magnet width is 0.7%. The relation between the distance of two magnets and the mutual inductance are simulated. Compared to the prototype, the magnet structure is modified and improved in design to increase the mechanical stability. A simple and practical design of multi-bolt sliding support structures which is used to push six magnets into the vacuum chamber is introduced.
Three kicker assemblies including eight pulsed magnets will be used in the rapid circle synchrotron of China Spallation Neutron Source. Magnetic field simulation and structural design of the kicker magnet is presented. The results of OPERA-3D simulation show that the central field integral of magnets meet the physical requirements by choosing a suitable magnet coil structure. The field uniformity in 60% magnet width is 0.7%. The relation between the distance of two magnets and the mutual inductance are simulated. Compared to the prototype, the magnet structure is modified and improved in design to increase the mechanical stability. A simple and practical design of multi-bolt sliding support structures which is used to push six magnets into the vacuum chamber is introduced.
2016,
28: 075104.
doi: 10.11884/HPLPB201628.075104
Abstract:
Superconducting parallel-bar deflectors are deflecting/crabbing cavities with attractive properties, such as compact structure and high efficiency. Aiming at the application in the XFEL proposed by Institute of High Energy Physics, a 325 MHz superconducting deflector with trapezoid parallel-bars is investigated and optimized. This paper presents the details on the design method and results of this deflector as follows: the simulation codes of CST MWS, CST PS, COMSOL, ANSYS are employed, the electromagnetic and mechanical parameters of the deflector are competitive, and the machining process is improved.
Superconducting parallel-bar deflectors are deflecting/crabbing cavities with attractive properties, such as compact structure and high efficiency. Aiming at the application in the XFEL proposed by Institute of High Energy Physics, a 325 MHz superconducting deflector with trapezoid parallel-bars is investigated and optimized. This paper presents the details on the design method and results of this deflector as follows: the simulation codes of CST MWS, CST PS, COMSOL, ANSYS are employed, the electromagnetic and mechanical parameters of the deflector are competitive, and the machining process is improved.
2016,
28: 076001.
doi: 10.11884/HPLPB201628.076001
Abstract:
This paper utilizes MCNP method together with the MCAM software (Monte-Carlo Automatic Modeling) to simulate the shielding performance of the laser fusion experimental facilitys target chamber, in the meanwhile, provides theoretical foundation for the establishment of the shielding system, radiation protection of personnel as well as the selection of the target chamber from radiation protection perspective. The simulation results show that the instantaneous gamma dose in the non-channel area is reduced by 50% when CLAM steel (China Low Activity Martensitic Steel) was applied as the chamber material comparing to the aluminum alloy. In addition, the neutron and gamma dose are decreased one level by using the heavy concrete with a thickness of 40 cm (aluminum alloy as the chamber target). It is worth mentioning that the neutron and gamma dose in the channel area is 10% larger than the bared target, so extra protection should be considered outside the hole.
This paper utilizes MCNP method together with the MCAM software (Monte-Carlo Automatic Modeling) to simulate the shielding performance of the laser fusion experimental facilitys target chamber, in the meanwhile, provides theoretical foundation for the establishment of the shielding system, radiation protection of personnel as well as the selection of the target chamber from radiation protection perspective. The simulation results show that the instantaneous gamma dose in the non-channel area is reduced by 50% when CLAM steel (China Low Activity Martensitic Steel) was applied as the chamber material comparing to the aluminum alloy. In addition, the neutron and gamma dose are decreased one level by using the heavy concrete with a thickness of 40 cm (aluminum alloy as the chamber target). It is worth mentioning that the neutron and gamma dose in the channel area is 10% larger than the bared target, so extra protection should be considered outside the hole.
2016,
28: 079001.
doi: 10.11884/HPLPB201628.079001
Abstract:
Based on the electro-hydraulic effect, rock fracture experiments were conducted on the artificial rock samples and the real sandstone samples. A pulsed power supply with a stored energy of 40 kJ/20 kV was developed. Experimental results show that large multi-fractures could be generated, the maximum length of the fracture in the vertical direction was 0.32 m. The shape of the fracture is related to the stored energy, the discharge voltage, the discharge times and the rock mechanical parameters. The 3-D morphology analyzer was used to observe the surface configuration of the fracture. The fractures have no obvious tortuosity in the near borehole area, and all the fractures generated by the pulsed discharge have certain average roughness in the range of 0.430-1.075 mm, which are capable of forming conductivity ability.
Based on the electro-hydraulic effect, rock fracture experiments were conducted on the artificial rock samples and the real sandstone samples. A pulsed power supply with a stored energy of 40 kJ/20 kV was developed. Experimental results show that large multi-fractures could be generated, the maximum length of the fracture in the vertical direction was 0.32 m. The shape of the fracture is related to the stored energy, the discharge voltage, the discharge times and the rock mechanical parameters. The 3-D morphology analyzer was used to observe the surface configuration of the fracture. The fractures have no obvious tortuosity in the near borehole area, and all the fractures generated by the pulsed discharge have certain average roughness in the range of 0.430-1.075 mm, which are capable of forming conductivity ability.
2016,
28: 079002.
doi: 10.11884/HPLPB201628.079002
Abstract:
The size of three dimensional (3D) profile data is too large for the 3D digital museum to properly transmit and display in real time. To solve the problem, this paper proposes a 3D profile data compression method based on composite dithering technique. Firstly, 3D profile data are stored into 24 bit image by utilizing the virtual structured-light projection system. Then, different dithering methods are applied to the different channels of the image, and the results are saved into the three most significant bits of the 8 bit grayscale image or three 1 bit logical images, to achieve a further compression of 3D profile data. The experimental results show that the proposed method achieves a compression ratio up to 75.9∶1 compared with the provided 3D model format, and is very suitable for real-time transmission, reconstruction and display of 3D profile data.
The size of three dimensional (3D) profile data is too large for the 3D digital museum to properly transmit and display in real time. To solve the problem, this paper proposes a 3D profile data compression method based on composite dithering technique. Firstly, 3D profile data are stored into 24 bit image by utilizing the virtual structured-light projection system. Then, different dithering methods are applied to the different channels of the image, and the results are saved into the three most significant bits of the 8 bit grayscale image or three 1 bit logical images, to achieve a further compression of 3D profile data. The experimental results show that the proposed method achieves a compression ratio up to 75.9∶1 compared with the provided 3D model format, and is very suitable for real-time transmission, reconstruction and display of 3D profile data.
2016,
28: 079901.
doi: 10.11884/HPLPB201628.079901
Abstract:
We fabricated (N+1) GT-wave fiber suitable for bidirectional pump method. 5.07 kW laser output with optical-to-optical efficiency of 74.5% was generated in bidirectional pump GT-wave fiber amplifier.
We fabricated (N+1) GT-wave fiber suitable for bidirectional pump method. 5.07 kW laser output with optical-to-optical efficiency of 74.5% was generated in bidirectional pump GT-wave fiber amplifier.
