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RSS1999 Vol. 11, No. 02
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1999,
11.
Abstract:
The principle of the coded imaging and its decoding in inertial confinement fusion is described simply in this paper. We take ring aperture microscope for example and use backproject (BP) algorithm to decode the coded image. The decoding program has been performed for numerical simulation. Simulationts of two models are made, and the results show that the accurance of BP algorithm is high and effect of reconstruction is good. Thus,it indicates that BP algorithm is applicable to decoding for coded image in ICF experiments.
The principle of the coded imaging and its decoding in inertial confinement fusion is described simply in this paper. We take ring aperture microscope for example and use backproject (BP) algorithm to decode the coded image. The decoding program has been performed for numerical simulation. Simulationts of two models are made, and the results show that the accurance of BP algorithm is high and effect of reconstruction is good. Thus,it indicates that BP algorithm is applicable to decoding for coded image in ICF experiments.
1999,
11.
Abstract:
Nano porous material SiO2 aerogels can not only be used as a low temperature Nuclear Target in ICF but also be used as an adsorbent of HTO vapor. BET，SEM，Pore Size Distribution and TEM techniques were used to characterize the morphology and pore structure of the low-density silica aerogels. Gas adsorption of the lowdensity silica aerogels was measured for the samples with various densities（18.6～200 kg·m-3）. Measurements were done at various pressure drops with water and benzene. The results of the adsorption isotherms were analyzed with BET multilayer adsorption theory．
Nano porous material SiO2 aerogels can not only be used as a low temperature Nuclear Target in ICF but also be used as an adsorbent of HTO vapor. BET，SEM，Pore Size Distribution and TEM techniques were used to characterize the morphology and pore structure of the low-density silica aerogels. Gas adsorption of the lowdensity silica aerogels was measured for the samples with various densities（18.6～200 kg·m-3）. Measurements were done at various pressure drops with water and benzene. The results of the adsorption isotherms were analyzed with BET multilayer adsorption theory．
1999,
11.
Abstract:
In this paper， we report the preparation and performances of the solgel antireflective and protective coatings on KDP crystals. The AR coatings with refractive index of 1.23 are of high transmission, the maximum of which is large than 99%, and the laser d amage threshold is about 10J／cm2 for laser beam at 1.06μm and with pulse width of 1ns. The composition coatings methyl silicone and porous silica reduced the threshold down to 5～8Ｊ/cm2.
In this paper， we report the preparation and performances of the solgel antireflective and protective coatings on KDP crystals. The AR coatings with refractive index of 1.23 are of high transmission, the maximum of which is large than 99%, and the laser d amage threshold is about 10J／cm2 for laser beam at 1.06μm and with pulse width of 1ns. The composition coatings methyl silicone and porous silica reduced the threshold down to 5～8Ｊ/cm2.
1999,
11.
Abstract:
The distribution of CⅥ line(at 207.1nm) and the time behavior has been measured with Optical Spectroscope Multichannel Analyzer and single channel near ultraviolet system in HT-6M Tokamak. The result of the analysis of line shape and the time behavior show that CⅥ line(at 207.1nm) stemmed from the emission of charge exchange recombination processes．
The distribution of CⅥ line(at 207.1nm) and the time behavior has been measured with Optical Spectroscope Multichannel Analyzer and single channel near ultraviolet system in HT-6M Tokamak. The result of the analysis of line shape and the time behavior show that CⅥ line(at 207.1nm) stemmed from the emission of charge exchange recombination processes．
1999,
11.
Abstract:
The optimum design of a newly typed impedance transformer in ICRH radiofrequency system on Tokamak is presented . The network synthesis utilizes an optimum function of approaching the property of the device and the mixed lumped and distributed circuit. The newly typed impedance transformer has the character of wide band, short length and the ability to transform large power, and fits the use of future fusion reactor.
The optimum design of a newly typed impedance transformer in ICRH radiofrequency system on Tokamak is presented . The network synthesis utilizes an optimum function of approaching the property of the device and the mixed lumped and distributed circuit. The newly typed impedance transformer has the character of wide band, short length and the ability to transform large power, and fits the use of future fusion reactor.
1999,
11.
Abstract:
The radiation fields and the design of coaxial biconical antenna are obtained with the field of equivalent Huggens source on the spherical surface aperture. The experiment of high power coaxial biconical antenna which has been operated in ultrawide band pulse of high voltage ±100kV, high repetition rate 100Hz, pulse duration 3.6ns, and the radiation peak power more than 100MW are also presented. The antenna band wide is from 15MHz to 1GHz，input impedance 50Ω; The FWHM of an tenna patterns for peak power in E plane and H plane is 50° and 360°, respectively, radiation efficiency more than 65%.
The radiation fields and the design of coaxial biconical antenna are obtained with the field of equivalent Huggens source on the spherical surface aperture. The experiment of high power coaxial biconical antenna which has been operated in ultrawide band pulse of high voltage ±100kV, high repetition rate 100Hz, pulse duration 3.6ns, and the radiation peak power more than 100MW are also presented. The antenna band wide is from 15MHz to 1GHz，input impedance 50Ω; The FWHM of an tenna patterns for peak power in E plane and H plane is 50° and 360°, respectively, radiation efficiency more than 65%.
1999,
11.
Abstract:
The behavior of a twostage slot ted gyroTWT is selfconsistently simulated in this paper by a single wave nonlinear code .The effects of the length and position of the sever and the lengths of the first and the second sections on beamwave interaction are analysed and discussed in details. The influence of the velocity spread of the electron beam on the efficiency, gain, and bandwidth of the beamwave interaction is also simulated and discussed in details in this paper.The electron beam employed encircles around the axis of the wave guide.
The behavior of a twostage slot ted gyroTWT is selfconsistently simulated in this paper by a single wave nonlinear code .The effects of the length and position of the sever and the lengths of the first and the second sections on beamwave interaction are analysed and discussed in details. The influence of the velocity spread of the electron beam on the efficiency, gain, and bandwidth of the beamwave interaction is also simulated and discussed in details in this paper.The electron beam employed encircles around the axis of the wave guide.
1999,
11.
Abstract:
The purpose of this paper is to use the Finite DifferenceTime Domain (FDTD) method to determine numerically the influence of plasma exhaust plume to boost flyer on electromag netic pulse effects. Computational datas indicate that the distribution of the induced skin current is seriously changed by the exhaust plume. The skin current density of the flyer with exhaust plume is quite larger than that of the flyer without exhaust plume. The waveform of the induced current is a decreased ringing wave and the ringing period equals twice to the time of induced current flowing along flyer and exhaust plume.
The purpose of this paper is to use the Finite DifferenceTime Domain (FDTD) method to determine numerically the influence of plasma exhaust plume to boost flyer on electromag netic pulse effects. Computational datas indicate that the distribution of the induced skin current is seriously changed by the exhaust plume. The skin current density of the flyer with exhaust plume is quite larger than that of the flyer without exhaust plume. The waveform of the induced current is a decreased ringing wave and the ringing period equals twice to the time of induced current flowing along flyer and exhaust plume.
1999,
11.
Abstract:
A frequency analysis system for single short microwave pulse which is developed by means of a ring of waveguide dispersive line is described in this paper.The system is characterized by frequency resolution 6 times higher than that of normal dispersive line with the same length.At the same time,the ring of dispersive line is capable of measuring the time-dependence realation for microwave frequency components and avoides uncertain rising from the duration of microwave pulse,making the uncertain is less than 2％.The system has been used successfully in the experimental study of Vircator．
A frequency analysis system for single short microwave pulse which is developed by means of a ring of waveguide dispersive line is described in this paper.The system is characterized by frequency resolution 6 times higher than that of normal dispersive line with the same length.At the same time,the ring of dispersive line is capable of measuring the time-dependence realation for microwave frequency components and avoides uncertain rising from the duration of microwave pulse,making the uncertain is less than 2％.The system has been used successfully in the experimental study of Vircator．
1999,
11.
Abstract:
A microwave electrin gun cavity structure with coupling cavity of antiarrowshaped crosssection is described in this paper. This structure has the advantages of decrease electrons backbombardment power to the cathode, good radial E field symmetry, small radial size, simplicity in fabrication, loose dimension altolerance．
A microwave electrin gun cavity structure with coupling cavity of antiarrowshaped crosssection is described in this paper. This structure has the advantages of decrease electrons backbombardment power to the cathode, good radial E field symmetry, small radial size, simplicity in fabrication, loose dimension altolerance．
1999,
11.
Abstract:
In this paper, the basic principle of how to obtain high power laser output using Stimulated Brillion Scatterin g (SBS) pulse compression is discussed, and a corresponding numerical simulatio n is also given. A principle experiment on pulse compression has been done at t he φ 40mm output stage of “Xingguang Ⅱ” laser facility, 60% SBS e nergy conversion efficiency are obtained with 4 times compression ratio (3.2ns/0 .8ns). The pulse duration is compressed nearly to the compression limit, with a good stability.
In this paper, the basic principle of how to obtain high power laser output using Stimulated Brillion Scatterin g (SBS) pulse compression is discussed, and a corresponding numerical simulatio n is also given. A principle experiment on pulse compression has been done at t he φ 40mm output stage of “Xingguang Ⅱ” laser facility, 60% SBS e nergy conversion efficiency are obtained with 4 times compression ratio (3.2ns/0 .8ns). The pulse duration is compressed nearly to the compression limit, with a good stability.
1999,
11.
Abstract:
A introduction is given to the e xperimental setting and the data acquisition system of 10kW solid propellant combustion driven CO2 gasdynamic laser system. Structure and operation process are described briefly, some descriptions about measuring methods of parameters，hardware configuration, and performance of data acquisition system as well as rules and methods of software development are mainly presented. The typical experimental results are also given.
A introduction is given to the e xperimental setting and the data acquisition system of 10kW solid propellant combustion driven CO2 gasdynamic laser system. Structure and operation process are described briefly, some descriptions about measuring methods of parameters，hardware configuration, and performance of data acquisition system as well as rules and methods of software development are mainly presented. The typical experimental results are also given.
1999,
11.
Abstract:
This paper mainly introduced the research work about the effect of the substrate preparation, coating materials, substrate condition and the impurities in the vacuum chamber during the deposition of optical coatings on Laser Induced Damage Threshold of films.
This paper mainly introduced the research work about the effect of the substrate preparation, coating materials, substrate condition and the impurities in the vacuum chamber during the deposition of optical coatings on Laser Induced Damage Threshold of films.
1999,
11.
Abstract:
The variation equation describing distance dependence of the beam waist of a fundamental Gaussian beam with high intensity propagating in logarithmically saturable nonlinear media has been deduced. The equation is formally consistent with that of a particle moving in potential well, so we can use the behavior of a particle moving in potential well to describe the breath mode of Gaussian beams. Having adopted the quadratic approximation of potential, we can solve the equation and get the approximately analytical solutions of Gaussiantyped breath mode. We analyze the incident condition dependence of its breath period and breath depth, and the conditions of Gaussian spatial solitons forming．
The variation equation describing distance dependence of the beam waist of a fundamental Gaussian beam with high intensity propagating in logarithmically saturable nonlinear media has been deduced. The equation is formally consistent with that of a particle moving in potential well, so we can use the behavior of a particle moving in potential well to describe the breath mode of Gaussian beams. Having adopted the quadratic approximation of potential, we can solve the equation and get the approximately analytical solutions of Gaussiantyped breath mode. We analyze the incident condition dependence of its breath period and breath depth, and the conditions of Gaussian spatial solitons forming．
1999,
11.
Abstract:
The transverse model spectral method is widely applied to numerical simulations of FEL oscillators . It is shown that the efficiency of the method is determined by several physical factors, and in the cases of holecoupled oscillators the efficiency is influenced mainly by the holecoupling effect and the varying transverse model structure of intracavity optical field.
The transverse model spectral method is widely applied to numerical simulations of FEL oscillators . It is shown that the efficiency of the method is determined by several physical factors, and in the cases of holecoupled oscillators the efficiency is influenced mainly by the holecoupling effect and the varying transverse model structure of intracavity optical field.
1999,
11.
Abstract:
A computational simulation for 2D smallsignal gain of COIL was performed based on a simple kinetics model wit hout considering mixing. Some results were obtained at different conditions. As comparing with the experimental results, both of the values and the trend of the smallsignal gain are very close at standard condition.
A computational simulation for 2D smallsignal gain of COIL was performed based on a simple kinetics model wit hout considering mixing. Some results were obtained at different conditions. As comparing with the experimental results, both of the values and the trend of the smallsignal gain are very close at standard condition.
1999,
11.
Abstract:
A theoretical model of chirpedpulseamplification is presented, and based on which we give the numerical analys is on the evolution of stretched pulse in the amplifier. Amplitude and phase modulation including: gainnarrowing, selfphasemodulation, gainsaturation and higherorderdispersions experienced by the pulse in the CPA system are resp onsible for the distortions on the temporal shape, power spectra and recompressed autocorrelation trace of the amplified pulse. In addition, for the first time the contribution of stretching chirps from the stretcher on the distortions of the pulse is studied in detail.
A theoretical model of chirpedpulseamplification is presented, and based on which we give the numerical analys is on the evolution of stretched pulse in the amplifier. Amplitude and phase modulation including: gainnarrowing, selfphasemodulation, gainsaturation and higherorderdispersions experienced by the pulse in the CPA system are resp onsible for the distortions on the temporal shape, power spectra and recompressed autocorrelation trace of the amplified pulse. In addition, for the first time the contribution of stretching chirps from the stretcher on the distortions of the pulse is studied in detail.
1999,
11.
Abstract:
The splitoperator method solving the wavefunction evolution of atomic systems in ultrashort laser fields is introduced. It gives more accurate simulation results in comparison with the standard difference expression. Much information can be extracted from the timeresolved wavefunction. The ionization probability and highorder harmonic spectrum of a simple atomic model is calculated．
The splitoperator method solving the wavefunction evolution of atomic systems in ultrashort laser fields is introduced. It gives more accurate simulation results in comparison with the standard difference expression. Much information can be extracted from the timeresolved wavefunction. The ionization probability and highorder harmonic spectrum of a simple atomic model is calculated．
1999,
11.
Abstract:
The intermittency characteristics of laser irradiance scintillation in a turbulent atmosphere were checked qualitatively via the wavelet transformation, and a quantitative description method based on the singularity measure analysis was adopted to study the intermittency in a systematic manner. From the diurnal variation of the intermittency index we found that the intermittercy of laser irradiance is rather stable under different scintillation index.
The intermittency characteristics of laser irradiance scintillation in a turbulent atmosphere were checked qualitatively via the wavelet transformation, and a quantitative description method based on the singularity measure analysis was adopted to study the intermittency in a systematic manner. From the diurnal variation of the intermittency index we found that the intermittercy of laser irradiance is rather stable under different scintillation index.
1999,
11.
Abstract:
A new style of flexible focus variable mirror which is forced by piezoelectric ceramic is designed in this paper. Finite elements method is used to calculate the mirrors deflection and the deviation of surface shape is quoted to evaluate the mirrors imaging quality. When the maximum deflection is 9μ m, the radius of mirrors curvature is varying from 610mm to 590mm and the PV val ue of deviation is 1μm, the relative deviation of surface shape is 0.3%．
A new style of flexible focus variable mirror which is forced by piezoelectric ceramic is designed in this paper. Finite elements method is used to calculate the mirrors deflection and the deviation of surface shape is quoted to evaluate the mirrors imaging quality. When the maximum deflection is 9μ m, the radius of mirrors curvature is varying from 610mm to 590mm and the PV val ue of deviation is 1μm, the relative deviation of surface shape is 0.3%．
1999,
11.
Abstract:
The regular crack is observed on the surface of InSb crystal when irradiated with a laser pulse of certain duration and certain energy density. In this paper, the mechanism of crack producing an dits regularity are analyzed from the lattice structure of InSb crystal.
The regular crack is observed on the surface of InSb crystal when irradiated with a laser pulse of certain duration and certain energy density. In this paper, the mechanism of crack producing an dits regularity are analyzed from the lattice structure of InSb crystal.
1999,
11.
Abstract:
According to the required puls e shape by ICF experiments, the injected pulse shape of main amplifier was obtained by the method of optimum control. The caculated result is in accord with the experimental results ,and the pulse shape design of SG Ⅲ laser is presented .
According to the required puls e shape by ICF experiments, the injected pulse shape of main amplifier was obtained by the method of optimum control. The caculated result is in accord with the experimental results ,and the pulse shape design of SG Ⅲ laser is presented .
1999,
11.
Abstract:
A twodimensional model was used to simulate the chemical dynamic process, gas dynamic process and lasi ng process of a combustiondriven CW HF overtone chemical laser. The calculated results included reaction product in combustor, HF molecule concentration on each vibration energy level while lasing, average pressure and temperature in the cavity, zero power gain coefficient, laser spectrum, output power, and chemical efficency. Compared with HF fundamental lasers, the results were analyzed．
A twodimensional model was used to simulate the chemical dynamic process, gas dynamic process and lasi ng process of a combustiondriven CW HF overtone chemical laser. The calculated results included reaction product in combustor, HF molecule concentration on each vibration energy level while lasing, average pressure and temperature in the cavity, zero power gain coefficient, laser spectrum, output power, and chemical efficency. Compared with HF fundamental lasers, the results were analyzed．
1999,
11.
Abstract:
The measurement system of Xray spot size for the 12MeV LIA is described in this paper. The Xray spot size and modulation transfer function, which judges the space resolution of 12MeV LIA Xray image, for the 12MeV LIA can be obtained using this system. According to the characteristic of approximate axial symmetry of Xray source and the distribution of image black density, the spa ce distribution of spot intensity is also imitated．
The measurement system of Xray spot size for the 12MeV LIA is described in this paper. The Xray spot size and modulation transfer function, which judges the space resolution of 12MeV LIA Xray image, for the 12MeV LIA can be obtained using this system. According to the characteristic of approximate axial symmetry of Xray source and the distribution of image black density, the spa ce distribution of spot intensity is also imitated．
1999,
11.
Abstract:
The theoretical results are presented for the stagnation zone effect of the slewing laser beam, for the examine，the numerical calculation using 4D code of the laser atmosphere propagation are proceeded. The theory analysis and the results computed by 4D code show that in many cases the influences of the stagnation zone effect are not important because in those cases the beam spreading radius induced by thermal distortion in the stagnation zone is smaller than that induced by the diffraction effect.
The theoretical results are presented for the stagnation zone effect of the slewing laser beam, for the examine，the numerical calculation using 4D code of the laser atmosphere propagation are proceeded. The theory analysis and the results computed by 4D code show that in many cases the influences of the stagnation zone effect are not important because in those cases the beam spreading radius induced by thermal distortion in the stagnation zone is smaller than that induced by the diffraction effect.
1999,
11.
Abstract:
A finite element model is used to analyze the temperature distribution of metal/explosive dilayer materials irradiated by laser. The temperature rise of explosive surface center varying with laser intensity, spot size, and irradiation time is given. The preliminary results about laser ignition on explosive with a metal envelope are got. The subsonic airflow convective heat transfer influence on the target temperature field is also analyzed.
A finite element model is used to analyze the temperature distribution of metal/explosive dilayer materials irradiated by laser. The temperature rise of explosive surface center varying with laser intensity, spot size, and irradiation time is given. The preliminary results about laser ignition on explosive with a metal envelope are got. The subsonic airflow convective heat transfer influence on the target temperature field is also analyzed.
