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RSS2010 Vol. 22, No. 06
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2010,
22.
Abstract:
The centered-difference, time-biased and FDTD algorithms in particle-in-cell (PIC) simulation are studied and the stability conditions of these algorithms are given. The high-frequency noise filtering characters of time-biased and high quality algorithms are analysed and their application scopes are discussed. The calculated results of the three algorithms are compared for the computation of a relativistic backward wave oscillator, further verifying their filtering characters.
The centered-difference, time-biased and FDTD algorithms in particle-in-cell (PIC) simulation are studied and the stability conditions of these algorithms are given. The high-frequency noise filtering characters of time-biased and high quality algorithms are analysed and their application scopes are discussed. The calculated results of the three algorithms are compared for the computation of a relativistic backward wave oscillator, further verifying their filtering characters.
2010,
22.
Abstract:
Guiding magnetic fields are necessary for some high-power microwave (HPM) sources, and the usual way to generate them is to apply capacitor discharge to solenoids. In the paper, a power source using the pulse width modulation(PMW) technique is designed, which can drive solenoids to generate a quasi-steady strong magnetic field with certain duration. A 15 F super-capacitor bank with the maximum charge voltage of 800 V, the maximum energy storage of 4.8 MJ and an internal resistance of less than 0.25 Ω is used as the energy storage part of the source. In experiments, when charged to 645 V, the source can generate a quasi-steady current of 900 A with a duration of 1.9 s on a solenoid with 60 mH inductance and 0.40 Ω resistance, and the corresponding axial magnetic field is 2.2 T at the maxi
Guiding magnetic fields are necessary for some high-power microwave (HPM) sources, and the usual way to generate them is to apply capacitor discharge to solenoids. In the paper, a power source using the pulse width modulation(PMW) technique is designed, which can drive solenoids to generate a quasi-steady strong magnetic field with certain duration. A 15 F super-capacitor bank with the maximum charge voltage of 800 V, the maximum energy storage of 4.8 MJ and an internal resistance of less than 0.25 Ω is used as the energy storage part of the source. In experiments, when charged to 645 V, the source can generate a quasi-steady current of 900 A with a duration of 1.9 s on a solenoid with 60 mH inductance and 0.40 Ω resistance, and the corresponding axial magnetic field is 2.2 T at the maxi
2010,
22.
Abstract:
An over-moded coaxial relativistic backward-wave oscillator was presented. Its interaction zone is composed of rippled slow wave structures with two different periods. In the help of the software MAGIC, three stable frequency microwave output was obtained in X-band. The results of the simulation are as follows: when the beam voltage is 570 kV, the beam current is 11.4 kA, the guided magnetic field is 0.72 T, and the output frequencies of the microwave are respectively 9.575, 10.025 and 10.475 GHz. The power level is 1.0 GW and the efficiency is 15.4%. By adjusting voltage, four frequency microwave was obtained.
An over-moded coaxial relativistic backward-wave oscillator was presented. Its interaction zone is composed of rippled slow wave structures with two different periods. In the help of the software MAGIC, three stable frequency microwave output was obtained in X-band. The results of the simulation are as follows: when the beam voltage is 570 kV, the beam current is 11.4 kA, the guided magnetic field is 0.72 T, and the output frequencies of the microwave are respectively 9.575, 10.025 and 10.475 GHz. The power level is 1.0 GW and the efficiency is 15.4%. By adjusting voltage, four frequency microwave was obtained.
2010,
22.
Abstract:
Analysis of bend waveguides shows that a small curvature-radius bend waveguide and a mitered-joint waveguide that have equal bend angles and equivalent axial lengths have similar transmission characteristics. Therefore, a new kind of TM01-TE11 11 mode converter, which is composed of several mitered-joint straight waveguides, are proposed and studied. Design method of such converters is studied, and several sample are presented, all of which have high conversion efficiencies of greater than 99% at center frequency.
Analysis of bend waveguides shows that a small curvature-radius bend waveguide and a mitered-joint waveguide that have equal bend angles and equivalent axial lengths have similar transmission characteristics. Therefore, a new kind of TM01-TE11 11 mode converter, which is composed of several mitered-joint straight waveguides, are proposed and studied. Design method of such converters is studied, and several sample are presented, all of which have high conversion efficiencies of greater than 99% at center frequency.
2010,
22.
Abstract:
The near field properties of circular aperture antennas with Gaussian amplitude distribution are analyzed by the aperture field integration method in this paper. The axial near field and gain expressions of the unfocused and focused circular aperture antennas are deduced. The near-axis field distribution of circular aperture antennas is obtained by numeric integration method. The analysis shows that for the circular aperture antennas with Gaussian amplitude distribution, axial near field varies in an oscillatory manner and the near-field gain is related to both aperture distribution and the distance from the antenna. The near-field gain in the focus can achieve the gain in far field and the field intensity near the focus can be enhanced greatly through aperture focusing.
The near field properties of circular aperture antennas with Gaussian amplitude distribution are analyzed by the aperture field integration method in this paper. The axial near field and gain expressions of the unfocused and focused circular aperture antennas are deduced. The near-axis field distribution of circular aperture antennas is obtained by numeric integration method. The analysis shows that for the circular aperture antennas with Gaussian amplitude distribution, axial near field varies in an oscillatory manner and the near-field gain is related to both aperture distribution and the distance from the antenna. The near-field gain in the focus can achieve the gain in far field and the field intensity near the focus can be enhanced greatly through aperture focusing.
2010,
22.
Abstract:
In the study of anti-HPM reinforcement of analog integrated-circuits, the damage mechanism of a single BJT in the tested ICs is researched first. The research is composed of effect experiments and failure analysis, in order to get the damage mechanism of BJTs. In the experiments, microwave energy is injected into the BJT from the base, the emitter and the collector respectively, till the transistors are damaged. The damage threshold, degradation and failure of tested transistors are observed. Failure analysis of damaged transistors compare the damaged position and the failure mode of damaged transistors, showing that transistors have the maximum vulnerability to microwave injected from the base, and the minimum vulnerability to microwave from the collector.
In the study of anti-HPM reinforcement of analog integrated-circuits, the damage mechanism of a single BJT in the tested ICs is researched first. The research is composed of effect experiments and failure analysis, in order to get the damage mechanism of BJTs. In the experiments, microwave energy is injected into the BJT from the base, the emitter and the collector respectively, till the transistors are damaged. The damage threshold, degradation and failure of tested transistors are observed. Failure analysis of damaged transistors compare the damaged position and the failure mode of damaged transistors, showing that transistors have the maximum vulnerability to microwave injected from the base, and the minimum vulnerability to microwave from the collector.
2010,
22.
Abstract:
The planar zone plate,light weight, low loss and low cost with simple design, has been extensively studied and used at microwave and millimeterwave frequencies. However, the attenuation in conventional lowloss materials increases at higher frequencies, and dimensional tolerances become smaller, making the fabrication of the terahertz zone plate more difficult. This investigation addressed the design of a zone plate with continuous phase for terahertz frequencies. The relation between the feature size and some important parameters of the zone plate was analyzed, including focal length, F-number, incident frequency and material refractive index, and some factors that affect the plate’s efficiency were discussed. The simulation of intensity distribution on the focal plane and optic axis
The planar zone plate,light weight, low loss and low cost with simple design, has been extensively studied and used at microwave and millimeterwave frequencies. However, the attenuation in conventional lowloss materials increases at higher frequencies, and dimensional tolerances become smaller, making the fabrication of the terahertz zone plate more difficult. This investigation addressed the design of a zone plate with continuous phase for terahertz frequencies. The relation between the feature size and some important parameters of the zone plate was analyzed, including focal length, F-number, incident frequency and material refractive index, and some factors that affect the plate’s efficiency were discussed. The simulation of intensity distribution on the focal plane and optic axis
2010,
22.
Abstract:
In this paper, space-charge field distribution of elliptical sheet beam is derived. Then its Diocotron instability is observed using 3D PIC program. After that, transmission characteristics of the elliptical sheet beam transporting in periodical cusped magnet and offset-periodical cusped magnet are analyzed and simulated. Through comparison, it is concluded that offset-periodical cusped magnet is more suitable for restraining the Diocotron instability.
In this paper, space-charge field distribution of elliptical sheet beam is derived. Then its Diocotron instability is observed using 3D PIC program. After that, transmission characteristics of the elliptical sheet beam transporting in periodical cusped magnet and offset-periodical cusped magnet are analyzed and simulated. Through comparison, it is concluded that offset-periodical cusped magnet is more suitable for restraining the Diocotron instability.
2010,
22.
Abstract:
The ultra fast neutron detector is the key device in ICF fusion reactionrate measure system. The performance of the ultra fast neutron scintillator BC-422 was simulated using Geant4 code system. The detection efficiency, temporal resolution and signal intensity of BC-422 with different thickness were calculated. The temporal resolution and signal intensity of BC-422 cladded with two kinds of reflection surfaces were compared. The results show that the properly designed BC-422 scintillator can perform well above 108 neutron yield, and its temporal resolution is better than 20 ps for DT fusion neutron, and 30 ps for DD fusion neutron. The BC-422 scintillator is applicable to the fusion reaction-rate measure system for a large-scale laser facility and its prototype requiring tens of ps-scal
The ultra fast neutron detector is the key device in ICF fusion reactionrate measure system. The performance of the ultra fast neutron scintillator BC-422 was simulated using Geant4 code system. The detection efficiency, temporal resolution and signal intensity of BC-422 with different thickness were calculated. The temporal resolution and signal intensity of BC-422 cladded with two kinds of reflection surfaces were compared. The results show that the properly designed BC-422 scintillator can perform well above 108 neutron yield, and its temporal resolution is better than 20 ps for DT fusion neutron, and 30 ps for DD fusion neutron. The BC-422 scintillator is applicable to the fusion reaction-rate measure system for a large-scale laser facility and its prototype requiring tens of ps-scal
2010,
22.
Abstract:
In the first run of the large laser prototype facility, two sensitive plastic scintillation detectors were used to measure the primary neutron yield and the secondary neutron yield in the implosion experiments. When the primary neutron yield exceeded 108, the secondary neutron yield could be gained. Under the low fuel areal density, the ratio of the secondary neutron yield to the primary neutron yield was used to calculate the fuel areal density. This is the first time that the values of fuel areal density was obtained through this way in China， and the fuel areal density is lower than 4 mg/cm2.
In the first run of the large laser prototype facility, two sensitive plastic scintillation detectors were used to measure the primary neutron yield and the secondary neutron yield in the implosion experiments. When the primary neutron yield exceeded 108, the secondary neutron yield could be gained. Under the low fuel areal density, the ratio of the secondary neutron yield to the primary neutron yield was used to calculate the fuel areal density. This is the first time that the values of fuel areal density was obtained through this way in China， and the fuel areal density is lower than 4 mg/cm2.
2010,
22.
Abstract:
Nickel/titanium multilayers with different period of 10, 30, 50 and 75 were fabricated by DC magnetron sputtering. Grazing incidence X-ray measured reflectivity was used to characterize the interfacial roughness of the multilayers. To study the evolution law of surface roughness of Ni/Ti multilayers with different period numbers, atomic force microscope(AFM) was used to characterize the surfaces of the multilayers. The results show that surface roughness of Ni/Ti multilayers increases with the number of periods of the multilayers. As the number of periods increases from 10 to 75, the roughness increases from 0.8 nm to 1.69 nm. Fitting results show that surface roughness mainly varies with the number of periods as a cubic function.
Nickel/titanium multilayers with different period of 10, 30, 50 and 75 were fabricated by DC magnetron sputtering. Grazing incidence X-ray measured reflectivity was used to characterize the interfacial roughness of the multilayers. To study the evolution law of surface roughness of Ni/Ti multilayers with different period numbers, atomic force microscope(AFM) was used to characterize the surfaces of the multilayers. The results show that surface roughness of Ni/Ti multilayers increases with the number of periods of the multilayers. As the number of periods increases from 10 to 75, the roughness increases from 0.8 nm to 1.69 nm. Fitting results show that surface roughness mainly varies with the number of periods as a cubic function.
2010,
22.
Abstract:
The current-voltage characteristic of hydrogen plasmas induced by helicon waves was measured in situ by a Langmuir probe under low pressure. According to Druyvesteyn method, raw data were fitted by an exponential transformation to a tangent hyperbolic function. Electron density, effective electron temperature and electron energy probability function(EEPF) were calculated from the fitted curves. The variation law of electron density, effective electron temperature and EEPF was analyzed in relation to different experimental parameters. The results demonstrate that RF power, gas pressure and controlled magnetic field have significant effects on state parameters of plasma. Electron density jumps with the increase of RF power because of the transition of mode, and it increases linearly with con
The current-voltage characteristic of hydrogen plasmas induced by helicon waves was measured in situ by a Langmuir probe under low pressure. According to Druyvesteyn method, raw data were fitted by an exponential transformation to a tangent hyperbolic function. Electron density, effective electron temperature and electron energy probability function(EEPF) were calculated from the fitted curves. The variation law of electron density, effective electron temperature and EEPF was analyzed in relation to different experimental parameters. The results demonstrate that RF power, gas pressure and controlled magnetic field have significant effects on state parameters of plasma. Electron density jumps with the increase of RF power because of the transition of mode, and it increases linearly with con
2010,
22.
Abstract:
The vacuum-gap discharge damage of micro-channel plate(MCP) imagers based on two screen-electrode structures, with Al-screen and indium-tin-oxide(ITO) screen respectively, is investigated after first arcing. The results show that the erosion pattern of Al-screen MCP imager appears as crater, and the electric insulating strength is less than 3 kV/mm under 10 μs-wide screen voltage, independent of MCP. The erosion of ITO-screen mostly appears as phosphor transporting to MCP, which drives field emission to steady state, and the electric insulating strength can reach 9 kV/mm at 10 μs-wide voltage. Thus, the discharge of MCP imagers depends mostly on screen-electrode structure, and ITO-screen MCP imagers can obtain higher electric insulating strength.
The vacuum-gap discharge damage of micro-channel plate(MCP) imagers based on two screen-electrode structures, with Al-screen and indium-tin-oxide(ITO) screen respectively, is investigated after first arcing. The results show that the erosion pattern of Al-screen MCP imager appears as crater, and the electric insulating strength is less than 3 kV/mm under 10 μs-wide screen voltage, independent of MCP. The erosion of ITO-screen mostly appears as phosphor transporting to MCP, which drives field emission to steady state, and the electric insulating strength can reach 9 kV/mm at 10 μs-wide voltage. Thus, the discharge of MCP imagers depends mostly on screen-electrode structure, and ITO-screen MCP imagers can obtain higher electric insulating strength.
2010,
22.
Abstract:
Amorphous hydrogenated carbon films were prepared by pulsed laser deposition(PLD) and the effect of the hydrogen pressure upon the performance of the films was studied. The AFM and Wyko images of the film show that the surfaces of the films are smooth and compact and that as the hydrogen pressure increases, the roughness becomes higher. The Raman spectra of the films were analyzed and it shows that the G peak and D peak approach to higher wave numbers as the hydrogen pressure increases. Fourier transform infrared spectroscopy indicates that there exist sp3—CH2 and sp2—CHclusters in the film. With floating method of PLD, self-supporting CH films with different thickness (100~300 nm) were synthesized.
Amorphous hydrogenated carbon films were prepared by pulsed laser deposition(PLD) and the effect of the hydrogen pressure upon the performance of the films was studied. The AFM and Wyko images of the film show that the surfaces of the films are smooth and compact and that as the hydrogen pressure increases, the roughness becomes higher. The Raman spectra of the films were analyzed and it shows that the G peak and D peak approach to higher wave numbers as the hydrogen pressure increases. Fourier transform infrared spectroscopy indicates that there exist sp3—CH2 and sp2—CHclusters in the film. With floating method of PLD, self-supporting CH films with different thickness (100~300 nm) were synthesized.
2010,
22.
Abstract:
Based on the polyimino ketone(PIKs), low density microporous foams were successfully prepared with the dioxane solvent by the general freezing-dry technology. In order to analyze the relationship between polymer concentration and foam density, a series of PIKs solution with different concentrations were confected. The results show that the polymer concentration has a good linear relationship with the actual density of PIKs foams and there is a fixed difference between the actual density and theoretic density, which will effectually control the density of foams. The pore structures of foams were also analyzed. The results show that with the increase of densities, the average pore size and BET surface area decrease. The general properties of PIKs foams are characterized by means of DSC, TG,
Based on the polyimino ketone(PIKs), low density microporous foams were successfully prepared with the dioxane solvent by the general freezing-dry technology. In order to analyze the relationship between polymer concentration and foam density, a series of PIKs solution with different concentrations were confected. The results show that the polymer concentration has a good linear relationship with the actual density of PIKs foams and there is a fixed difference between the actual density and theoretic density, which will effectually control the density of foams. The pore structures of foams were also analyzed. The results show that with the increase of densities, the average pore size and BET surface area decrease. The general properties of PIKs foams are characterized by means of DSC, TG,
2010,
22.
Abstract:
SiO2 colloidal crystals were fabricated by vertical deposition and spin coating methods, and their appearance morphology, microstructure and photonic band-gap properties were compared. The used colloidal SiO2 spheres were synthesized by improved Stober method with different diameters and small relative standard deviation. With white light illumination, characteristic six-beam diffraction appears on the SiO2 colloidal crystal fabricated by spin coating, while stripes appear on the surface of the SiO2 colloidal crystal fabricated by vertical deposition. SEM images reveal that, with different dilutions in the same spin coating process conditions, the quality of SiO2 colloidal crystal dispersed in a mixture of glycol and ethanol is best. Transmission
SiO2 colloidal crystals were fabricated by vertical deposition and spin coating methods, and their appearance morphology, microstructure and photonic band-gap properties were compared. The used colloidal SiO2 spheres were synthesized by improved Stober method with different diameters and small relative standard deviation. With white light illumination, characteristic six-beam diffraction appears on the SiO2 colloidal crystal fabricated by spin coating, while stripes appear on the surface of the SiO2 colloidal crystal fabricated by vertical deposition. SEM images reveal that, with different dilutions in the same spin coating process conditions, the quality of SiO2 colloidal crystal dispersed in a mixture of glycol and ethanol is best. Transmission
2010,
22.
Abstract:
Spectral responses of aluminum- and gold-cathode X-ray diodes, commonly used in Z-pinch experiments of Qiangguang-I generator, have been calibrated on the 4B7B beamline of Beijing Synchrotron Radiation Facility, with a spectral range of 2.1 to 5.9 keV. Results of different kinds of cathodes, as well as other published data, are compared to check the effect of cathode material, preparation process and usage conditions on the degradation and dispersivity of the sensitivity. Evaporated gold cathodes stored in dry air for several years still have quite uniform spectral responses, while also with a large fall that their responses are only 20% to 25% of those reported data for fresh gold cathodes. Used gold cathodes even show a further fall in sensitivities. The aluminum cathodes exhibit muc
Spectral responses of aluminum- and gold-cathode X-ray diodes, commonly used in Z-pinch experiments of Qiangguang-I generator, have been calibrated on the 4B7B beamline of Beijing Synchrotron Radiation Facility, with a spectral range of 2.1 to 5.9 keV. Results of different kinds of cathodes, as well as other published data, are compared to check the effect of cathode material, preparation process and usage conditions on the degradation and dispersivity of the sensitivity. Evaporated gold cathodes stored in dry air for several years still have quite uniform spectral responses, while also with a large fall that their responses are only 20% to 25% of those reported data for fresh gold cathodes. Used gold cathodes even show a further fall in sensitivities. The aluminum cathodes exhibit muc
2010,
22.
Abstract:
The diagnostic instrument manipulator(DIM) is designed for the instruments pointing and positioning in inertial confinement fusion (ICF) experiment. The DIM is a hybrid manipulator and provides precision 2-rotation and 1-translation capability for positioning of diagnostic packages. The inverse kinematics and close-form direct kinematics of the DIM are presented. Moreover, the error mapping function, which represents the end positioning error resulted from limbs length error and joint clearances, is formulated by using matrix method with the differential of kinematics function. Monte-Carlo method is involved in influencing factors analysis on the capability of DIM positioning. The clearances of sphere -pin-joint has a greater negative impact on DIM terminal error than other source errors b
The diagnostic instrument manipulator(DIM) is designed for the instruments pointing and positioning in inertial confinement fusion (ICF) experiment. The DIM is a hybrid manipulator and provides precision 2-rotation and 1-translation capability for positioning of diagnostic packages. The inverse kinematics and close-form direct kinematics of the DIM are presented. Moreover, the error mapping function, which represents the end positioning error resulted from limbs length error and joint clearances, is formulated by using matrix method with the differential of kinematics function. Monte-Carlo method is involved in influencing factors analysis on the capability of DIM positioning. The clearances of sphere -pin-joint has a greater negative impact on DIM terminal error than other source errors b
2010,
22.
Abstract:
The attenuation coefficient of electric thruster plasma jet for communication signals was calculated with time-domain finite-difference method. And the attenuation effect on C-band electromagnetic wave propagating through microwave plasma thruster jet was tested at ground using space-wave method. Theoretical calculation and experimental results show that the attenuation coefficient increases almost linearly with the plasma jet frequency, but decreases while the frequency of communication signals increasing. And it has an increasing first then decreasing tendency with the plasma collision frequency increasing. The attenuation coefficient of the C-band communication signal varies from 1.5 dB to 6.0 dB, with the plasma jet density from 0.9×1016 to 1.8×1016. The attenua
The attenuation coefficient of electric thruster plasma jet for communication signals was calculated with time-domain finite-difference method. And the attenuation effect on C-band electromagnetic wave propagating through microwave plasma thruster jet was tested at ground using space-wave method. Theoretical calculation and experimental results show that the attenuation coefficient increases almost linearly with the plasma jet frequency, but decreases while the frequency of communication signals increasing. And it has an increasing first then decreasing tendency with the plasma collision frequency increasing. The attenuation coefficient of the C-band communication signal varies from 1.5 dB to 6.0 dB, with the plasma jet density from 0.9×1016 to 1.8×1016. The attenua
2010,
22.
Abstract:
In order to optimize the design scheme of the wavefront control system in a high power solid-state laser facility, wavefront test and correction experiment are conducted on a verification facility. The results show that, although the equivalent number of Nd: glasses increases, the output static and dynamic wavefronts without defocus component is not largely raised for the application of U-turn beam reverser in the main amplifier. However, the defocus component visibly increases. And the laser is blocked at the pinhole of the spatial filter. The output near field of the main amplifier has sharp modulation and energy loss. In the experiment, the defocus component before each pinhole is adjusted in advance by moving the focal lens in the optical path. And the static wavefront without defocus
In order to optimize the design scheme of the wavefront control system in a high power solid-state laser facility, wavefront test and correction experiment are conducted on a verification facility. The results show that, although the equivalent number of Nd: glasses increases, the output static and dynamic wavefronts without defocus component is not largely raised for the application of U-turn beam reverser in the main amplifier. However, the defocus component visibly increases. And the laser is blocked at the pinhole of the spatial filter. The output near field of the main amplifier has sharp modulation and energy loss. In the experiment, the defocus component before each pinhole is adjusted in advance by moving the focal lens in the optical path. And the static wavefront without defocus
2010,
22.
Abstract:
A novel microstrip switch was developed based on micro-discharge plasma. The plasma switch is a dynamic device of microwave component to control the propagation of electromagnetic wave on the microstripline structure, which has a similar structure as RF MEMS switch but replacing its connecting anchor by using time-varying plasma. A basic structure of plasma switch contains a microstrip line with a small gap which is able to block electromagnetic wave and a discharge configuration which can generate a sheet-like plasma. When the discharge is turned on, the electromagnetic wave will transmit through the gap with the help of the conductive plasma, resulting in the ON state. When the discharge is extinguished, the electromagnetic wave energy will be reflected by the stripline gap, realizing th
A novel microstrip switch was developed based on micro-discharge plasma. The plasma switch is a dynamic device of microwave component to control the propagation of electromagnetic wave on the microstripline structure, which has a similar structure as RF MEMS switch but replacing its connecting anchor by using time-varying plasma. A basic structure of plasma switch contains a microstrip line with a small gap which is able to block electromagnetic wave and a discharge configuration which can generate a sheet-like plasma. When the discharge is turned on, the electromagnetic wave will transmit through the gap with the help of the conductive plasma, resulting in the ON state. When the discharge is extinguished, the electromagnetic wave energy will be reflected by the stripline gap, realizing th
2010,
22.
Abstract:
Employing Jones theory, thermal self-induced depolarization in high power conventional Faraday isolators is investigated with single mode and multimode lasers. The results show that depolarization in high power isolators is composed of depolarization induced by linear birefringence and depolarization induced by circular birefringence, and both are proportional to square of laser power; with a constant laser power, depolarization induced by linear birefringence is beam radius independent, but depolarization induced by circular birefringence increases with decrease of beam radius. Both depolarizations are reduced by multimode incidence. Depolarization induced by linear birefringence with multimode incidence is only 0.6 times that with single mode. Reduction of depolarization induced by circu
Employing Jones theory, thermal self-induced depolarization in high power conventional Faraday isolators is investigated with single mode and multimode lasers. The results show that depolarization in high power isolators is composed of depolarization induced by linear birefringence and depolarization induced by circular birefringence, and both are proportional to square of laser power; with a constant laser power, depolarization induced by linear birefringence is beam radius independent, but depolarization induced by circular birefringence increases with decrease of beam radius. Both depolarizations are reduced by multimode incidence. Depolarization induced by linear birefringence with multimode incidence is only 0.6 times that with single mode. Reduction of depolarization induced by circu
2010,
22.
Abstract:
The thermo-chemical ablation of the carbon-carbon complex material of hypersonic vehicles in the condition of aero-heating and laser ablation respectively and coupled aero-heating with laser ablation were calculated via the engineering calculation method. The numerical results indicate that: the ablation rate was minor with laser ablation only; the ablation rate rose with the laser energy increase; in the condition of aero-heating, laser ablation damage factor of carbon-carbon material for hypersonic vehicles will increase greatly; the aero-heating cumulating effect was not distinct to the coupling ablation of aero-heating and laser ablation.
The thermo-chemical ablation of the carbon-carbon complex material of hypersonic vehicles in the condition of aero-heating and laser ablation respectively and coupled aero-heating with laser ablation were calculated via the engineering calculation method. The numerical results indicate that: the ablation rate was minor with laser ablation only; the ablation rate rose with the laser energy increase; in the condition of aero-heating, laser ablation damage factor of carbon-carbon material for hypersonic vehicles will increase greatly; the aero-heating cumulating effect was not distinct to the coupling ablation of aero-heating and laser ablation.
2010,
22.
Abstract:
The principle of high power MOSFET generating high-current narrow-width pulses to drive laser diode is theoretically analyzed, and the formula of MOSFET gate drive current and the estimation formula of MOSFET drive rise time are obtained. The key factors which influence the laser diode(LD) power supply current width, amplitude and oscillation are summarized through simulation. Theory and simulation show that components stray inductance, circuit routing inductance and load inductance influence the drive current greatly. Experiment results show that the MOSFET switch-on time is about 2 ns at the drain-source voltage of 200 V. The LD drive power supply’s pulse current possesses a rise-time less than 10 ns, with the pulse width, amplitude and frequency ranging in 15～100 ns， 0～50 A and 0～5
The principle of high power MOSFET generating high-current narrow-width pulses to drive laser diode is theoretically analyzed, and the formula of MOSFET gate drive current and the estimation formula of MOSFET drive rise time are obtained. The key factors which influence the laser diode(LD) power supply current width, amplitude and oscillation are summarized through simulation. Theory and simulation show that components stray inductance, circuit routing inductance and load inductance influence the drive current greatly. Experiment results show that the MOSFET switch-on time is about 2 ns at the drain-source voltage of 200 V. The LD drive power supply’s pulse current possesses a rise-time less than 10 ns, with the pulse width, amplitude and frequency ranging in 15～100 ns， 0～50 A and 0～5
2010,
22.
Abstract:
The stochastic parallel gradient descent(SPGD) algorithm can optimize the system performance indexes directly to correct wavefront aberration. A 61-element adaptive optics system model based on SPGD algorithm was simulated. For different initial static aberrations, the algorithm’s correction capabilities were analyzed. The selections of algorithm gain coefficient and perturbation amplitude were compared in the conditions of adopting different performance indexes, and so was the correction effects. Simulation results demonstrate that the algorithm’s convergence rate depends on gain coefficient and perturbation amplitude to a great extent. For relatively severe aberrations with perturbation amplitude ranging from 0.50 to 0.85, the correction effects of using mean radius as the system perfo
The stochastic parallel gradient descent(SPGD) algorithm can optimize the system performance indexes directly to correct wavefront aberration. A 61-element adaptive optics system model based on SPGD algorithm was simulated. For different initial static aberrations, the algorithm’s correction capabilities were analyzed. The selections of algorithm gain coefficient and perturbation amplitude were compared in the conditions of adopting different performance indexes, and so was the correction effects. Simulation results demonstrate that the algorithm’s convergence rate depends on gain coefficient and perturbation amplitude to a great extent. For relatively severe aberrations with perturbation amplitude ranging from 0.50 to 0.85, the correction effects of using mean radius as the system perfo
2010,
22.
Abstract:
The influence of deflector position on characters of the streak tube is discussed. A large amount of electron trajectories are figured out by statistical simulation method, and the modulation transfer function(MTF) used to evaluate temporal and spatial resolution is calculated. The conclusions are as follows: the streak tube has obtained the optimal temporal resolution when the deflection plate is set to the aperture of anode, and the optimal spatial resolution is obtained when deflection plate is set to the point with minimum electron beam diameter. In addition, any perpendicular deviation of deflection plate from the axis of streak tube can worsen both temporal and spatial resolution worse, thus axis of the deflection plate should strictly overlap with the center axis of the streak tube.
The influence of deflector position on characters of the streak tube is discussed. A large amount of electron trajectories are figured out by statistical simulation method, and the modulation transfer function(MTF) used to evaluate temporal and spatial resolution is calculated. The conclusions are as follows: the streak tube has obtained the optimal temporal resolution when the deflection plate is set to the aperture of anode, and the optimal spatial resolution is obtained when deflection plate is set to the point with minimum electron beam diameter. In addition, any perpendicular deviation of deflection plate from the axis of streak tube can worsen both temporal and spatial resolution worse, thus axis of the deflection plate should strictly overlap with the center axis of the streak tube.
2010,
22.
Abstract:
The paper describes the design and construction of an intracavity intensity enhanced hot-band CW CO2 laser with the line selected by concave grating. In this laser, using a gas mixture of 13% CO2, 15% N2 and 72% He (volume fraction) at a total pressure of 1 074.9 Pa and a discharge current of 25 mA, more than 100 laser lines are observed from R(56) to P(60) in the regular band 0001-［1000, 0200］Ⅰ,Ⅱ, besides, another 18 lines in 11 μm wavelength region with 9 lines in the 0111-0310 band and 9 lines in the 0111-1110 band, are also observed under the condition of no hot CO2 absorption cell in the cavity. In the experiment, it is found that the laser output power decreases when more helium gas is added to the laser gas mixture. The one-way intrac
The paper describes the design and construction of an intracavity intensity enhanced hot-band CW CO2 laser with the line selected by concave grating. In this laser, using a gas mixture of 13% CO2, 15% N2 and 72% He (volume fraction) at a total pressure of 1 074.9 Pa and a discharge current of 25 mA, more than 100 laser lines are observed from R(56) to P(60) in the regular band 0001-［1000, 0200］Ⅰ,Ⅱ, besides, another 18 lines in 11 μm wavelength region with 9 lines in the 0111-0310 band and 9 lines in the 0111-1110 band, are also observed under the condition of no hot CO2 absorption cell in the cavity. In the experiment, it is found that the laser output power decreases when more helium gas is added to the laser gas mixture. The one-way intrac
2010,
22.
Abstract:
The analytical expression for the propagation of a radial Lorentz array beam with an initial phase distribution is derived and used to study the propagation properties of the coherently combined beam in free space. For the case of the radial Lorentz array beam with a certain different initial phase distribution, the intensity profile of the resulting beam becomes a dark-hollow one, whereas for the case of the array beam with an equal initial phase distribution, the center of the intensity profile is a bright spot. The beam width and power in the bucket of the resulting beam depend on the waist width of the Lorentz beamlet, and on the initial phase distribution and radius of the radial array. The results are illustrated by numerical examples. When the radius of the radial array is larger an
The analytical expression for the propagation of a radial Lorentz array beam with an initial phase distribution is derived and used to study the propagation properties of the coherently combined beam in free space. For the case of the radial Lorentz array beam with a certain different initial phase distribution, the intensity profile of the resulting beam becomes a dark-hollow one, whereas for the case of the array beam with an equal initial phase distribution, the center of the intensity profile is a bright spot. The beam width and power in the bucket of the resulting beam depend on the waist width of the Lorentz beamlet, and on the initial phase distribution and radius of the radial array. The results are illustrated by numerical examples. When the radius of the radial array is larger an
2010,
22.
Abstract:
The description of a Laguerre-Gaussian beam is directly derived from the Maxwell’s equations. According to the vector spectrum representation of the Maxwell’s equations and the vectorial structure of an electromagnetic beam, the analytical TE and TM terms of a Laguerre-Gaussian beam in the near field are presented by means of some mathematical techniques. The light intensity distributions of a Laguerre-Gaussian beam, the TE term and the TM term are depicted in the near field, respectively. The vectorial structures of Laguerre-Gaussian beams are compared. The Laguerre-Gaussian beams, whose dependences on angle are respectively cosine and sine, have thoroughly alike whole beam spots with the only difference of spatial orientation of the sub lobes. However, their vectorial structure is dist
The description of a Laguerre-Gaussian beam is directly derived from the Maxwell’s equations. According to the vector spectrum representation of the Maxwell’s equations and the vectorial structure of an electromagnetic beam, the analytical TE and TM terms of a Laguerre-Gaussian beam in the near field are presented by means of some mathematical techniques. The light intensity distributions of a Laguerre-Gaussian beam, the TE term and the TM term are depicted in the near field, respectively. The vectorial structures of Laguerre-Gaussian beams are compared. The Laguerre-Gaussian beams, whose dependences on angle are respectively cosine and sine, have thoroughly alike whole beam spots with the only difference of spatial orientation of the sub lobes. However, their vectorial structure is dist
2010,
22.
Abstract:
The oscillation condition for the simultaneous dual-wavelength operation and intracavity sum-frequency mixing in a diode-end-pumped Nd:YVO4 solid-state laser is analyzed. A CW laser at 491 nm is reported with an LD-pumped Nd:YVO4 crystal and a type I critical phase matching LBO as the laser crystal and the intracavity sum-frequency mixing crystal, respectively. By the simple linear resonator, TEM00 mode laser at 491 nm of 2.5 mW was obtained with 5.0 W injection pump power. The optical-to-optical conversion efficiency was 0.05%.
The oscillation condition for the simultaneous dual-wavelength operation and intracavity sum-frequency mixing in a diode-end-pumped Nd:YVO4 solid-state laser is analyzed. A CW laser at 491 nm is reported with an LD-pumped Nd:YVO4 crystal and a type I critical phase matching LBO as the laser crystal and the intracavity sum-frequency mixing crystal, respectively. By the simple linear resonator, TEM00 mode laser at 491 nm of 2.5 mW was obtained with 5.0 W injection pump power. The optical-to-optical conversion efficiency was 0.05%.
2010,
22.
Abstract:
Aiming at the all-optical regeneration based on self-phase modulation effect(SPM) in fiber, the effect of the chromatic dispersion on the transfer function and Q factor improvement of the regenerator was analyzed, as well as the interaction between chromatic dispersion and SPM. The method to improve the plateau of transfer function via changing the segments of fiber in the regenerator was proposed. The numerical results show that chromatic dispersion will suppress the spectra broadening caused by SPM and reduce the Q factor improvement in the all-optical regenerator. For fibers with different parameters such as dispersion, nonlinear coefficient, length and so on, the performance of the regenerator will keep basically unchanged if the ratio of the product of dispersion and fiber length to t
Aiming at the all-optical regeneration based on self-phase modulation effect(SPM) in fiber, the effect of the chromatic dispersion on the transfer function and Q factor improvement of the regenerator was analyzed, as well as the interaction between chromatic dispersion and SPM. The method to improve the plateau of transfer function via changing the segments of fiber in the regenerator was proposed. The numerical results show that chromatic dispersion will suppress the spectra broadening caused by SPM and reduce the Q factor improvement in the all-optical regenerator. For fibers with different parameters such as dispersion, nonlinear coefficient, length and so on, the performance of the regenerator will keep basically unchanged if the ratio of the product of dispersion and fiber length to t
2010,
22.
Abstract:
The effects of high temperature flowfields around hypersonic air vehicles on laser lethality have been analysed in the case of the American Airborne Laser(ABL) system, including the effects of gas breakdown, plasma shielding and ablation smoke absorption. It is shown that, the electron number density in flowfields is generally less than 1017 cm-3 which can not result in plasma shielding. The plasma shielding of high pressure flowfields (above around 10 MPa) may be obvious only within the transmission distance of 0.5 km and only for broad pulse duration which may rarely happen in battlefield. The ablation products can not result in extinction to laser emission when the ablation mass flux nondimensioned by free stream flux is less than around 10-2 and the fli
The effects of high temperature flowfields around hypersonic air vehicles on laser lethality have been analysed in the case of the American Airborne Laser(ABL) system, including the effects of gas breakdown, plasma shielding and ablation smoke absorption. It is shown that, the electron number density in flowfields is generally less than 1017 cm-3 which can not result in plasma shielding. The plasma shielding of high pressure flowfields (above around 10 MPa) may be obvious only within the transmission distance of 0.5 km and only for broad pulse duration which may rarely happen in battlefield. The ablation products can not result in extinction to laser emission when the ablation mass flux nondimensioned by free stream flux is less than around 10-2 and the fli
2010,
22.
Abstract:
The periodic cusped magnetic fields generated by a kind of air-core electromagnets made of thin metal sheets have been investigated analytically and numerically. The amplitude of the PCM fields can be increased through increasing the PCM period, decreasing the magnet gap, or increasing the linear current density in the metal sheets. In addition, the increase of the PCM period will lead to better uniformity of peak-to-peak magnetic fields on the axis z.
The periodic cusped magnetic fields generated by a kind of air-core electromagnets made of thin metal sheets have been investigated analytically and numerically. The amplitude of the PCM fields can be increased through increasing the PCM period, decreasing the magnet gap, or increasing the linear current density in the metal sheets. In addition, the increase of the PCM period will lead to better uniformity of peak-to-peak magnetic fields on the axis z.
2010,
22.
Abstract:
The structure of a 1 MV low-impedance accelerator and the design principles of its main switch were introduced. Optimized design and simulation of the oil switch, which was selected as the main switch, were carried out. The simulation showed when the switch was working at 1 MV, the discharge inductance was about 100 nH, the distributed capacitance was 150 pF, and the charging inductance was 360 nH. No unacceptable influence was caused by those distributed parameters. Simulation also showed that the electric field inside the main switch was safe, that is, no flashover would happen at the oil-nylon interface. The low-impedance accelerator was assembled with the optimized oil switch and produced 700 kV, 70 kA electron beams with 150 ns pulse width (FWHM). Preliminary tests show that the switc
The structure of a 1 MV low-impedance accelerator and the design principles of its main switch were introduced. Optimized design and simulation of the oil switch, which was selected as the main switch, were carried out. The simulation showed when the switch was working at 1 MV, the discharge inductance was about 100 nH, the distributed capacitance was 150 pF, and the charging inductance was 360 nH. No unacceptable influence was caused by those distributed parameters. Simulation also showed that the electric field inside the main switch was safe, that is, no flashover would happen at the oil-nylon interface. The low-impedance accelerator was assembled with the optimized oil switch and produced 700 kV, 70 kA electron beams with 150 ns pulse width (FWHM). Preliminary tests show that the switc
2010,
22.
Abstract:
The principle of an integrative denvice of Tesla transformer with Blumlein pulse forming line(PFL) has been introduced in the paper. The parameters of the Telsa transformer and the Blumlein PFL were designed, while the electrical field distribution of the device was analyzed. The results show that the structure of the PFL satisfies the insulation condition of transformer oil, ensuring the device’s safe operation. Finally, the full circuit analysis of the device is simulated by Pspice. It is shown that the charge voltage of the Blumlein PFL is up to 1.37 MV. In this condition, the output voltage of 50 Ω load is 1.4 MV with 40 ns pulse width, which meets the design requirement.
The principle of an integrative denvice of Tesla transformer with Blumlein pulse forming line(PFL) has been introduced in the paper. The parameters of the Telsa transformer and the Blumlein PFL were designed, while the electrical field distribution of the device was analyzed. The results show that the structure of the PFL satisfies the insulation condition of transformer oil, ensuring the device’s safe operation. Finally, the full circuit analysis of the device is simulated by Pspice. It is shown that the charge voltage of the Blumlein PFL is up to 1.37 MV. In this condition, the output voltage of 50 Ω load is 1.4 MV with 40 ns pulse width, which meets the design requirement.
2010,
22.
Abstract:
In order to investigate the nanosecond current interruption mechanism of semiconductor opening switch (SOS) with a doping profile of p+-p-n-n+ structure, a 1D circuit-fluid coupled model was developed by deriving a current-voltage relation expression from the fluid mechanics equations and the total current density equation. The model simultaneously solves the external circuit equations and the internal fluid mechanics equations of SOS. Numerical results show the evolution of carrier density distribution and electric field in the SOS during the nanosecond pulse opening process. At the beginning of the process, the carrier density in the n-n+ boundary first dropped obviously with a high electric field yield and similar phenomena occurred in the p+-
In order to investigate the nanosecond current interruption mechanism of semiconductor opening switch (SOS) with a doping profile of p+-p-n-n+ structure, a 1D circuit-fluid coupled model was developed by deriving a current-voltage relation expression from the fluid mechanics equations and the total current density equation. The model simultaneously solves the external circuit equations and the internal fluid mechanics equations of SOS. Numerical results show the evolution of carrier density distribution and electric field in the SOS during the nanosecond pulse opening process. At the beginning of the process, the carrier density in the n-n+ boundary first dropped obviously with a high electric field yield and similar phenomena occurred in the p+-
2010,
22.
Abstract:
The high power microwave(HPM) sources of peak power at GW class have the characteristics of large volume and heavy weight. In the application of HPM directional radiation, the microwave sources are generally static, and with the beam waveguide to adjust the beam pointing, the transmission efficiency is usually 40% to 50%. The radar rotary joint used in the conventional mechanical scanning radar cannot meet the requirements of HPM antenna because of its small power capacity. The relations of conversion between different modes and radii of curvature in bending waveguide were investigated using the coupled wave theory. A waveguide bent 90° and a simple TM01 mode rotary joint were developed and tested. The results indicate that their transmission efficiencies were greater than 93% and the pow
The high power microwave(HPM) sources of peak power at GW class have the characteristics of large volume and heavy weight. In the application of HPM directional radiation, the microwave sources are generally static, and with the beam waveguide to adjust the beam pointing, the transmission efficiency is usually 40% to 50%. The radar rotary joint used in the conventional mechanical scanning radar cannot meet the requirements of HPM antenna because of its small power capacity. The relations of conversion between different modes and radii of curvature in bending waveguide were investigated using the coupled wave theory. A waveguide bent 90° and a simple TM01 mode rotary joint were developed and tested. The results indicate that their transmission efficiencies were greater than 93% and the pow
2010,
22.
Abstract:
This paper describes the design and test results of an liner transformer driver(LTD) stage prototype and its multi-gap switch. This stage consists of 20 storage capacitors(100 kV/20 nF) that are arranged in 10 identical bricks locating evenly around the axis of the stage. Each brick contains two capacitors, a multi-gap switch, and the output connector that transfer the energy to the resistive load. The outer diameter of the stage is about 1.5 m, at a thickness of 20 cm. The load current was measured by B-dot probe. The magnetic core was premagnetized before each shot. At the charge voltage of ±90 kV, the stage can deliver 102.2 kA fast pulse with a FWHM of 133 ns into a 1.1 Ω resistive load. The experimental results show that the LTD stage has the capability of fast pulse output.
This paper describes the design and test results of an liner transformer driver(LTD) stage prototype and its multi-gap switch. This stage consists of 20 storage capacitors(100 kV/20 nF) that are arranged in 10 identical bricks locating evenly around the axis of the stage. Each brick contains two capacitors, a multi-gap switch, and the output connector that transfer the energy to the resistive load. The outer diameter of the stage is about 1.5 m, at a thickness of 20 cm. The load current was measured by B-dot probe. The magnetic core was premagnetized before each shot. At the charge voltage of ±90 kV, the stage can deliver 102.2 kA fast pulse with a FWHM of 133 ns into a 1.1 Ω resistive load. The experimental results show that the LTD stage has the capability of fast pulse output.
2010,
22.
Abstract:
A soft X-ray detector has been made with high quality chemical vapor deposited(CVD) diamond and the electrical structure of micro-strip. Through the measurement of response time on a laser with the pulse width of 10 ps, the full width at half maximum of the data got in the oscilloscope was 115 ps. The rise time of the CVD diamond detector was calculated to be 49 ps. In the experiment on the laser prototype facility, the signal got by the CVD diamond detector was compared with that got by a soft X-ray spectrosmeter. Both signals coincided well. The detector is proved to be a kind of reliable soft X-ray detector with fast response and high signal-to-noise ratio.
A soft X-ray detector has been made with high quality chemical vapor deposited(CVD) diamond and the electrical structure of micro-strip. Through the measurement of response time on a laser with the pulse width of 10 ps, the full width at half maximum of the data got in the oscilloscope was 115 ps. The rise time of the CVD diamond detector was calculated to be 49 ps. In the experiment on the laser prototype facility, the signal got by the CVD diamond detector was compared with that got by a soft X-ray spectrosmeter. Both signals coincided well. The detector is proved to be a kind of reliable soft X-ray detector with fast response and high signal-to-noise ratio.
2010,
22.
Abstract:
Taking the advantage of the BV theorem, a scattering model is established for the polarized light scattering from a spheroid particle on or near a wafer. The scattering process is analysed and the scattering coefficients are derived through expanding vector spherical harmonic functions. The variation of differential scattering cross section（DSCS） of a spheroid particle with scattering angle is calculated, which is compared with the results of discreter sources method and extended Mie method. The results are coincident, proving the validity of the method. The variations of DSCS are discussed with incident angle, scattering angle, spheroid particle size, axial ratio, the distance of the particle from the wafer, dielectric constant, and particle azimuth angle. The result shows that with th
Taking the advantage of the BV theorem, a scattering model is established for the polarized light scattering from a spheroid particle on or near a wafer. The scattering process is analysed and the scattering coefficients are derived through expanding vector spherical harmonic functions. The variation of differential scattering cross section（DSCS） of a spheroid particle with scattering angle is calculated, which is compared with the results of discreter sources method and extended Mie method. The results are coincident, proving the validity of the method. The variations of DSCS are discussed with incident angle, scattering angle, spheroid particle size, axial ratio, the distance of the particle from the wafer, dielectric constant, and particle azimuth angle. The result shows that with th
2010,
22.
Abstract:
A wideband spectrum of electromagnetic radiation from the special explosive which differs from high explosive has been measured. Four broadband antennas were employed to observe pulse electromagnetic radiation from a spherical explosive. The frequency spectra from these experiments were analyzed using time/frequency Fourier methods. The results show that the EM pulse from the explosive with mass of 150 g lasted 50 ns with a sharp rise. The radiation mechanisms for the phenomenon are theoretically discussed, in order to make it clear how the energy radiates. It is suggested plasma radiation might be the source of the electromagnetic radiation detected by the antennas.
A wideband spectrum of electromagnetic radiation from the special explosive which differs from high explosive has been measured. Four broadband antennas were employed to observe pulse electromagnetic radiation from a spherical explosive. The frequency spectra from these experiments were analyzed using time/frequency Fourier methods. The results show that the EM pulse from the explosive with mass of 150 g lasted 50 ns with a sharp rise. The radiation mechanisms for the phenomenon are theoretically discussed, in order to make it clear how the energy radiates. It is suggested plasma radiation might be the source of the electromagnetic radiation detected by the antennas.
2010,
22.
Abstract:
Acid etching combined with UV laser conditioning is developed to enhance the laser induced damage threshold (LIDT) of fused silica. Firstly, the fused silica is etched for 1~100 min with a buffered 1% HF solution. After acid etching, its transmittance, surface roughness and LIDT are measured. The results reveal that the fused silica has the highest LIDT and transmittance after etching for 10 min. Then UV laser (355 nm) conditioning is adopted to process the 10-min-etched fused silica. When the laser fluence is below 60% of fused silica’s zero probability damage threshold, the LIDT increases gradually with the increase of laser conditioning fluence. However, the LIDT rapidly decreases to be lower than the threshold of the 10-min-etched fused silica when the conditioning fluence is up to 80
Acid etching combined with UV laser conditioning is developed to enhance the laser induced damage threshold (LIDT) of fused silica. Firstly, the fused silica is etched for 1~100 min with a buffered 1% HF solution. After acid etching, its transmittance, surface roughness and LIDT are measured. The results reveal that the fused silica has the highest LIDT and transmittance after etching for 10 min. Then UV laser (355 nm) conditioning is adopted to process the 10-min-etched fused silica. When the laser fluence is below 60% of fused silica’s zero probability damage threshold, the LIDT increases gradually with the increase of laser conditioning fluence. However, the LIDT rapidly decreases to be lower than the threshold of the 10-min-etched fused silica when the conditioning fluence is up to 80
2010,
22.
Abstract:
In dynamic light scattering(DLS) measurement, auto correlation method is used for signal denoising, whose denoising effect is affected by data amount. Based on different characteristics of noises and signals, wavelet packet transform is used in the signal , which can improve signal to noise ratio and particle inversion results. The DLS signal of 100 nm particles is denoised by the two methods and the auto correlation functions of the denoised signals are respectively inverted. The inversion error can be improved by 0.88%~6.41% after denoising by wavelet packet. Denoising results of different data amounts by the two methods show that, wavelet packet transform is more effective for short data, and when the data amount is greater than 1×106, the effects of the two denoising method
In dynamic light scattering(DLS) measurement, auto correlation method is used for signal denoising, whose denoising effect is affected by data amount. Based on different characteristics of noises and signals, wavelet packet transform is used in the signal , which can improve signal to noise ratio and particle inversion results. The DLS signal of 100 nm particles is denoised by the two methods and the auto correlation functions of the denoised signals are respectively inverted. The inversion error can be improved by 0.88%~6.41% after denoising by wavelet packet. Denoising results of different data amounts by the two methods show that, wavelet packet transform is more effective for short data, and when the data amount is greater than 1×106, the effects of the two denoising method
2010,
22.
Abstract:
According to the B-H curve and structure dimensions of the Snubber, induction voltage and eddy current of any core lamination with the thickness of saturated regions are derived by referring to Fink’s method, when accelerator breakdown occurs at the Experimental Advanced Superconducting Tokamak(EAST). Using Ampere’s law, in each core tape, the eddy current and the thickness of saturated regions are deduced. And then, the equivalent resistance of the Snubber is obtained. The transient eddy current due to stray capacitance is analyzed, and the exponential time constant and the arc current are obtained. Then the maximum width of the lamination and the minimum thickness of the core tape are 28 mm and 114 μm, respectively. The obtained experimental time constant is approximately the same as
According to the B-H curve and structure dimensions of the Snubber, induction voltage and eddy current of any core lamination with the thickness of saturated regions are derived by referring to Fink’s method, when accelerator breakdown occurs at the Experimental Advanced Superconducting Tokamak(EAST). Using Ampere’s law, in each core tape, the eddy current and the thickness of saturated regions are deduced. And then, the equivalent resistance of the Snubber is obtained. The transient eddy current due to stray capacitance is analyzed, and the exponential time constant and the arc current are obtained. Then the maximum width of the lamination and the minimum thickness of the core tape are 28 mm and 114 μm, respectively. The obtained experimental time constant is approximately the same as
2010,
22.
Abstract:
Electrical aging of insulation materials affects the reliability and security of pulsed power equipments. Based on the present pulsed source, the electrical tree initiation characteristic of epoxy resin is studied under different frequencies (1, 25, 50, 100, 300 and 500 Hz). The parameters of the pulsed source are as follows: peak voltage about 34 kV, rise time about 40 ns and half pulse width about 70 ns. The relationship between epoxy resin aging and voltage frequency is studied. Experiments demonstrate that tree initiation voltage decreases as frequency increases. The initiation voltage under positive pulse is higher than that under negative pulse. Insulation characteristic of E44 is better than that of PMMA. Factors influencing electrical tree initiation characteristic of E44 are discu
Electrical aging of insulation materials affects the reliability and security of pulsed power equipments. Based on the present pulsed source, the electrical tree initiation characteristic of epoxy resin is studied under different frequencies (1, 25, 50, 100, 300 and 500 Hz). The parameters of the pulsed source are as follows: peak voltage about 34 kV, rise time about 40 ns and half pulse width about 70 ns. The relationship between epoxy resin aging and voltage frequency is studied. Experiments demonstrate that tree initiation voltage decreases as frequency increases. The initiation voltage under positive pulse is higher than that under negative pulse. Insulation characteristic of E44 is better than that of PMMA. Factors influencing electrical tree initiation characteristic of E44 are discu
2010,
22.
Abstract:
The electron irradiation ground simulation test was conducted on the ITO/F46/Ag thermal control coating. The variation of surface resistivity of the ITO/F46/Ag coating with electron fluence was discussed, and the scanning electron microscope was used to analyze the irradiation effects of electron on the coating’s morphology. It was found that there were severe damages appearing in the ITO/F46/Ag coating, e.g. crack, debris and melt erosion. The damage mechanism of the ITO/F46/Ag thermal control coating under electron irradiation was analyzed, and a surface damage model was proposed.
The electron irradiation ground simulation test was conducted on the ITO/F46/Ag thermal control coating. The variation of surface resistivity of the ITO/F46/Ag coating with electron fluence was discussed, and the scanning electron microscope was used to analyze the irradiation effects of electron on the coating’s morphology. It was found that there were severe damages appearing in the ITO/F46/Ag coating, e.g. crack, debris and melt erosion. The damage mechanism of the ITO/F46/Ag thermal control coating under electron irradiation was analyzed, and a surface damage model was proposed.
2010,
22.
Abstract:
This paper reports quantitative and qualitative analysis of metals in the liquid by laser-induced breakdown spectroscopy. The two measurement modes, liquid jets (diameter of 0.5 mm) and static liquids, have been used in experiments. The calibration curves of Cd, Pb, Fe and Al elements with different concentrations in the liquid were acquired, and the linear correlation coefficients of the calibration curves are basically higher than 0.99. The detection limits of metals are 0.206 5(Cd), 0.147 6(Fe), 0.061 9(Al) and 0.200 9(Pb) g/L at the liquid jets mode and 0.050 1(Cd), 0.023 9(Fe), 0.014 8(Al) and 0.006 9(Pb) g/L at the static liquids mode. The experiment results provide the basis for the detection of metallic elements in the industrial waste water．
This paper reports quantitative and qualitative analysis of metals in the liquid by laser-induced breakdown spectroscopy. The two measurement modes, liquid jets (diameter of 0.5 mm) and static liquids, have been used in experiments. The calibration curves of Cd, Pb, Fe and Al elements with different concentrations in the liquid were acquired, and the linear correlation coefficients of the calibration curves are basically higher than 0.99. The detection limits of metals are 0.206 5(Cd), 0.147 6(Fe), 0.061 9(Al) and 0.200 9(Pb) g/L at the liquid jets mode and 0.050 1(Cd), 0.023 9(Fe), 0.014 8(Al) and 0.006 9(Pb) g/L at the static liquids mode. The experiment results provide the basis for the detection of metallic elements in the industrial waste water．
2010,
22.
Abstract:
The structural and elastic properties of ZrH2 are investigated using the full-potential linearized augmented plane wave plus local orbital method within the generalized gradient in the frame of the density functional theory. The ground state properties such as lattice constant, bulk modulus and elastic constants are in good agreement with numerous experimental and theoretical data. Through the quasi-harmonic Debye model, in which the phononic effects are considered, the thermodynamic properties have been obtained successfully, such as thermal expansion coefficient, Debye temperature and heat capacity in the whole pressure range from 0 to 50 GPa and temperature range from 0 to 1 300 K. The results show that heat capacity increases with temperature, tending to the Dulong-Petit limit. Debye t
The structural and elastic properties of ZrH2 are investigated using the full-potential linearized augmented plane wave plus local orbital method within the generalized gradient in the frame of the density functional theory. The ground state properties such as lattice constant, bulk modulus and elastic constants are in good agreement with numerous experimental and theoretical data. Through the quasi-harmonic Debye model, in which the phononic effects are considered, the thermodynamic properties have been obtained successfully, such as thermal expansion coefficient, Debye temperature and heat capacity in the whole pressure range from 0 to 50 GPa and temperature range from 0 to 1 300 K. The results show that heat capacity increases with temperature, tending to the Dulong-Petit limit. Debye t
2010,
22.
Abstract:
A model of gas spark switch with rough cathode is presented. Utilizing the rough layer thickness and electric enhancement factor to characterize the cathode roughness, the breakdown situation of gas spark switch is studied by probability theory. Influences of gas pressure on the stability, E/p (electric field strength to gas pressure) curve and insulation recovery velocity are analyzed. The study shows when the cathode is rough enough for the mean free path of electron, the switch obtain the highest stability, but when the dimension of coarse structure is close to the mean free path of electron, the switch obtain the best recovery property.
A model of gas spark switch with rough cathode is presented. Utilizing the rough layer thickness and electric enhancement factor to characterize the cathode roughness, the breakdown situation of gas spark switch is studied by probability theory. Influences of gas pressure on the stability, E/p (electric field strength to gas pressure) curve and insulation recovery velocity are analyzed. The study shows when the cathode is rough enough for the mean free path of electron, the switch obtain the highest stability, but when the dimension of coarse structure is close to the mean free path of electron, the switch obtain the best recovery property.
2010,
22.
Abstract:
The distributions of the energy deposition of gamma-rays with various energies in LSO crystal were calculated by MCNP code and compared with the results of the experiment. The effects of different interactions between the ray and the material were analyzed. The laws of the energy deposition of gamma ray in axial and radial directions were obtained. In axial direction, the calculated distributions are approximately exponential for different incidental energies, and the deposited energy decreases a lot in the sub marginal region. In radial direction, the energy deposition in the region near the incident axis is mainly ascribed to cascade electrons, and it decreases as radius increases. In the region far from the incident axis, the deposited energy is mainly produced by the secondary gamma ra
The distributions of the energy deposition of gamma-rays with various energies in LSO crystal were calculated by MCNP code and compared with the results of the experiment. The effects of different interactions between the ray and the material were analyzed. The laws of the energy deposition of gamma ray in axial and radial directions were obtained. In axial direction, the calculated distributions are approximately exponential for different incidental energies, and the deposited energy decreases a lot in the sub marginal region. In radial direction, the energy deposition in the region near the incident axis is mainly ascribed to cascade electrons, and it decreases as radius increases. In the region far from the incident axis, the deposited energy is mainly produced by the secondary gamma ra
2010,
22.
Abstract:
The time-dependent-wave-packet plus the split-operator-Fourier method has been applied to studying the influence on the high harmonic generation of the different isotopes. The recollision probabilities of the isotopes H2, D2, and T2 have been got by solving the time-dependent Schr-dinger equation depicting the correlation between the electron and its parent ions in the intense laser field. Although the electron will return several times to recollide with its parent ion during the laser pulses the largest probability to each isotope molecule occurs in the first optical period. Compared the recollision probabilities during the last two optical periods, T2 isotope has the largest probability. In addition, the ionization rates of the isotopes have be
The time-dependent-wave-packet plus the split-operator-Fourier method has been applied to studying the influence on the high harmonic generation of the different isotopes. The recollision probabilities of the isotopes H2, D2, and T2 have been got by solving the time-dependent Schr-dinger equation depicting the correlation between the electron and its parent ions in the intense laser field. Although the electron will return several times to recollide with its parent ion during the laser pulses the largest probability to each isotope molecule occurs in the first optical period. Compared the recollision probabilities during the last two optical periods, T2 isotope has the largest probability. In addition, the ionization rates of the isotopes have be
2010,
22.
Abstract:
Experiments on the interaction of deuterium clusters with intense laser pulses have been performed on SILEX-Ⅰ. Faraday cups were used to characterize the deuterium ions emitted from laser irradiated gas plumes. The size and its distribution of the deuterium clusters were calculated using energy spectra of the ions, developing a new calibrating method of cluster size. Due to the influence of laser prepulse, the resulting cluster size is smaller than that by Rayleigh scattering. The results are important for analyzing clusters’ interaction with intense lasers, and they may provide guidelines to choose proper fire time.
Experiments on the interaction of deuterium clusters with intense laser pulses have been performed on SILEX-Ⅰ. Faraday cups were used to characterize the deuterium ions emitted from laser irradiated gas plumes. The size and its distribution of the deuterium clusters were calculated using energy spectra of the ions, developing a new calibrating method of cluster size. Due to the influence of laser prepulse, the resulting cluster size is smaller than that by Rayleigh scattering. The results are important for analyzing clusters’ interaction with intense lasers, and they may provide guidelines to choose proper fire time.
2010,
22.
Abstract:
The magnetic field generated by the solenoid mounted inside the accelerating cell is calculated. There are three steps to finish this work. Firstly, a formula of the ideal magnetic field of the solenoid is deduced according to the Biot-Savart law. Secondly, the effect of the field homogenizer ring on the magnetic field is taken into account. Then, a group of formulas are deduced which relate the deflecting angle to the magnetic field components. At last, the electron transport in accelerating cell is simulated with the derived field components, and the comparison between the measurement and the simulation validate the calculation.
The magnetic field generated by the solenoid mounted inside the accelerating cell is calculated. There are three steps to finish this work. Firstly, a formula of the ideal magnetic field of the solenoid is deduced according to the Biot-Savart law. Secondly, the effect of the field homogenizer ring on the magnetic field is taken into account. Then, a group of formulas are deduced which relate the deflecting angle to the magnetic field components. At last, the electron transport in accelerating cell is simulated with the derived field components, and the comparison between the measurement and the simulation validate the calculation.
2010,
22.
Abstract:
The super fragment separator (Super-FRS) of the FAIR-project (facility for antiproton and ion research) is a large international cooperation project. The quench transient thermal stress is simulated using FEM software ADINA. The simulation uses the C program for a secondary development of ADINA to control the load and call the solver. The thermal stress and the acoustic are analyzed. The results show that the maximal thermal stress is 26 MPa, and the frequency of the acoustic wave is about 35 Hz．
The super fragment separator (Super-FRS) of the FAIR-project (facility for antiproton and ion research) is a large international cooperation project. The quench transient thermal stress is simulated using FEM software ADINA. The simulation uses the C program for a secondary development of ADINA to control the load and call the solver. The thermal stress and the acoustic are analyzed. The results show that the maximal thermal stress is 26 MPa, and the frequency of the acoustic wave is about 35 Hz．
2010,
22.
Abstract:
Experiments have been done to study the magnetic characteristics of the magnetic cores under MHz repetition-rate multi-pulse excitation in the multi-pulse inductive accelerator. With a low-voltage (～1 kV) multi-pulse power system based on the MOSFET solid state switch, the permeabilities of a ferrite core and a amorphous core have been obtain, as well as their magnetization curves under multi-pulse excitation. Significant differences in the experimental results show that the amorphous core is more fit in multi-pulse exciting condition. And in the later experiments on induction cells with ferrite and amorphous cores under high voltage (more than 200 kV) triple-pulse excitation, consistent results have been derived.
Experiments have been done to study the magnetic characteristics of the magnetic cores under MHz repetition-rate multi-pulse excitation in the multi-pulse inductive accelerator. With a low-voltage (～1 kV) multi-pulse power system based on the MOSFET solid state switch, the permeabilities of a ferrite core and a amorphous core have been obtain, as well as their magnetization curves under multi-pulse excitation. Significant differences in the experimental results show that the amorphous core is more fit in multi-pulse exciting condition. And in the later experiments on induction cells with ferrite and amorphous cores under high voltage (more than 200 kV) triple-pulse excitation, consistent results have been derived.
