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RSS2005 Vol. 17, No. 01
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2005,
17.
Abstract:
The energies and transition probabilities of the atomic systems are calculated by Grasp-92 Utility. Based on the local thermal equilibrium theory and the data of 058 experiment of the inertial confinement fusion(ICF), with Ar+D2 filled target pellet, the temperature and density of plasmas in target pellet of ICF are calculated and they are 804.7 eV，8.39×1023 cm－3 respectively, the results agree well with that of other calculations.
The energies and transition probabilities of the atomic systems are calculated by Grasp-92 Utility. Based on the local thermal equilibrium theory and the data of 058 experiment of the inertial confinement fusion(ICF), with Ar+D2 filled target pellet, the temperature and density of plasmas in target pellet of ICF are calculated and they are 804.7 eV，8.39×1023 cm－3 respectively, the results agree well with that of other calculations.
2005,
17.
Abstract:
In order to improve the filled factor of beam and the conversion efficiency of amplifier, with reference to the technical integrated line of Shenguang-Ⅲ, a kind of new spatial four-pass amplifier structure is designed, which is made up of four pairs of spatial filters, in the Ti:sapphire CPA system. The spatial structure amplifier is put in a vacuum because there are real focus points in the amplifier. Before amplification, the input Gauss beam firstly goes through a diaphragm and then a static spatial filter with a pinhole, the beam is refitted into a 4th order super-gaussian beam. Then, the image of super-gaussian beam is relayed to the first spatial filter of amplifier. The Ti:sapphire crystal is put at the surface of image or object of the spatial filters for the sake of the good qual
In order to improve the filled factor of beam and the conversion efficiency of amplifier, with reference to the technical integrated line of Shenguang-Ⅲ, a kind of new spatial four-pass amplifier structure is designed, which is made up of four pairs of spatial filters, in the Ti:sapphire CPA system. The spatial structure amplifier is put in a vacuum because there are real focus points in the amplifier. Before amplification, the input Gauss beam firstly goes through a diaphragm and then a static spatial filter with a pinhole, the beam is refitted into a 4th order super-gaussian beam. Then, the image of super-gaussian beam is relayed to the first spatial filter of amplifier. The Ti:sapphire crystal is put at the surface of image or object of the spatial filters for the sake of the good qual
2005,
17.
Abstract:
The energy spectra of hot electrons have been measured using the magnetic spectrometers, fitted with the LiF thermoluminescent dosimeter (TLD) which were calibrated using Cs137 γ-ray sources, in the interaction of a 130 mJ, 60 fs, 800 nm, 1∶10-6, 7.0×1017 W·cm-2 P-polarized laser incidence on Cu foil target at an angle of 45° with respect to the target normal without any prepulse. The yield of hot electrons and the conversion efficiency of laser energy to energy of hot electrons are 1.19×1010/sr and 4.55%/sr at the normal of target and are 1.83×109/sr and 0.76%/sr at the specular direction of laser, which were deduced from the energy spectra of hot electrons. They were different at various direction because of the hot electrons produced in the interaction of laser-plasma constituted
The energy spectra of hot electrons have been measured using the magnetic spectrometers, fitted with the LiF thermoluminescent dosimeter (TLD) which were calibrated using Cs137 γ-ray sources, in the interaction of a 130 mJ, 60 fs, 800 nm, 1∶10-6, 7.0×1017 W·cm-2 P-polarized laser incidence on Cu foil target at an angle of 45° with respect to the target normal without any prepulse. The yield of hot electrons and the conversion efficiency of laser energy to energy of hot electrons are 1.19×1010/sr and 4.55%/sr at the normal of target and are 1.83×109/sr and 0.76%/sr at the specular direction of laser, which were deduced from the energy spectra of hot electrons. They were different at various direction because of the hot electrons produced in the interaction of laser-plasma constituted
2005,
17.
Abstract:
Weibel instability is studied by three dimensional particle in cell simulation code LARED-P. The generated magnetic field and currents by Weibel instability present filamentary structure. When the Weibel instability reaches the saturation stage, the current filaments begin to interact with each other. The relativistic electron beam deposits part of its energy into the plasmas through instabilities. For 10 MeV electrons, when the beam electron density concentrates 5% of the total electron density, 14% energy of beam can be deposited at last. The dispersion relation in this case also deduced, the growth rate is obtained in some simple cases.
Weibel instability is studied by three dimensional particle in cell simulation code LARED-P. The generated magnetic field and currents by Weibel instability present filamentary structure. When the Weibel instability reaches the saturation stage, the current filaments begin to interact with each other. The relativistic electron beam deposits part of its energy into the plasmas through instabilities. For 10 MeV electrons, when the beam electron density concentrates 5% of the total electron density, 14% energy of beam can be deposited at last. The dispersion relation in this case also deduced, the growth rate is obtained in some simple cases.
2005,
17.
Abstract:
The interaction between laser and plasma has been studied using a 2.5 dimensional particle simulation code. The results show that electrons are accelerated by J×B heating mechanism and a strong electrostatic field is caused by charge separation, which has a potential well structure. Electrons are oscillating in electrostatic field potential wells and can be accelerated many times. Some electrons with higher velocity escape from potential wells, so that charge separation becomes stronger and stronger, and then electrostatic fields break up and electrons get the energy of electrostatic field. During the process, electrons are oscillating locally and accelerated, their relativistic kinetic energy can reach over 10 MeV. This is a new kind of heating mechanism and is named local oscillating el
The interaction between laser and plasma has been studied using a 2.5 dimensional particle simulation code. The results show that electrons are accelerated by J×B heating mechanism and a strong electrostatic field is caused by charge separation, which has a potential well structure. Electrons are oscillating in electrostatic field potential wells and can be accelerated many times. Some electrons with higher velocity escape from potential wells, so that charge separation becomes stronger and stronger, and then electrostatic fields break up and electrons get the energy of electrostatic field. During the process, electrons are oscillating locally and accelerated, their relativistic kinetic energy can reach over 10 MeV. This is a new kind of heating mechanism and is named local oscillating el
2005,
17.
Abstract:
Using the model of transient stimulated rotational Raman scattering (SRRS) and considering many factors such as phase change of laser beams, the pulsedshape, the depletion of pump laser, the nonlinear amplification of the Stokes field, and the initial random Stokes scattered field, etc, the effect of the spatial phase perturbation on the SRRS of highpower ultraviolet laser beams in long air path has been studied. It is shown that the effects on the threshold of SRRS and the temporal pulse profile are weak. However, the effect on the beam quality is very evident. It is also shown that the energy distribution of the beam becomes more nonuniform and the beam intensity contrast increases sharply as the phase perturbation grows, reducing the beam quality. When the propagation distance is
Using the model of transient stimulated rotational Raman scattering (SRRS) and considering many factors such as phase change of laser beams, the pulsedshape, the depletion of pump laser, the nonlinear amplification of the Stokes field, and the initial random Stokes scattered field, etc, the effect of the spatial phase perturbation on the SRRS of highpower ultraviolet laser beams in long air path has been studied. It is shown that the effects on the threshold of SRRS and the temporal pulse profile are weak. However, the effect on the beam quality is very evident. It is also shown that the energy distribution of the beam becomes more nonuniform and the beam intensity contrast increases sharply as the phase perturbation grows, reducing the beam quality. When the propagation distance is
2005,
17.
Abstract:
Subsurface damage has been the main cause to lower the laser induced damage threshold of optics components in high power solid laser system, and one important of them is scratch. finite difference time domain (FDTD) method was used to simulate the electromagnetic distribution around column form or triangular scratch in fused silica. 2D electric field amplitude distributing is illustrated, and maximal values vs.sizes are calculated. The conclusion displays that the electric intensity is maximal when size is 2λ, which is easy to cause self-focusing, the effect can be neglected when scratch is subwavelength class or large enough. The depth is larger, the maximal value is larger when size is the same, but it becomes smaller when scratch is too deep．
Subsurface damage has been the main cause to lower the laser induced damage threshold of optics components in high power solid laser system, and one important of them is scratch. finite difference time domain (FDTD) method was used to simulate the electromagnetic distribution around column form or triangular scratch in fused silica. 2D electric field amplitude distributing is illustrated, and maximal values vs.sizes are calculated. The conclusion displays that the electric intensity is maximal when size is 2λ, which is easy to cause self-focusing, the effect can be neglected when scratch is subwavelength class or large enough. The depth is larger, the maximal value is larger when size is the same, but it becomes smaller when scratch is too deep．
2005,
17.
Abstract:
On the basis of the different emission bands between the fast and slow components in BaF2 crystal, the photonic band multilayer filter with 3.5 periods of Al2O3/MgF2/Al/MgF2… was designed and developed in order to suppress the slow component of the scintillation light in BaF2. It is shown that the filter can increase more than 80 times of the ratio of the intensities of the fast emission to the slow one, while the transmission, emission and decay time spectra of BaF2 crystal modified by the filter are not changed apparently after 60Co γray irradiation under the dose of 105 Gy. The results indicate that BaF2 crystal modified by the filter can not only avoid the interference of the slow component effectively, but also keep the good radiation resistance．
On the basis of the different emission bands between the fast and slow components in BaF2 crystal, the photonic band multilayer filter with 3.5 periods of Al2O3/MgF2/Al/MgF2… was designed and developed in order to suppress the slow component of the scintillation light in BaF2. It is shown that the filter can increase more than 80 times of the ratio of the intensities of the fast emission to the slow one, while the transmission, emission and decay time spectra of BaF2 crystal modified by the filter are not changed apparently after 60Co γray irradiation under the dose of 105 Gy. The results indicate that BaF2 crystal modified by the filter can not only avoid the interference of the slow component effectively, but also keep the good radiation resistance．
2005,
17.
Abstract:
The image transfer function is used to judge the precision of XUV radiography system and silicon grating foils are prepared to measure the image transfer function. Using photoetching and ion beam etching processes, the silicon grating foils with check and stripe pattern were prepared on thin silicon foil. The thickness of thin silicon foil was 3 to 4 μm and the pattern’s etching depth was about 1 μm. The size of check pattern was 25 μm×25 μm and the width of stripe pattern was 5 μm. The parameters of photoetching and ion beam etching processes were studied to control the precision of patterns. And silicon grating foils were used to measure the image transfer function by XUV radiography system on “Shenguang Ⅱ” high power laser facility in 2000.
The image transfer function is used to judge the precision of XUV radiography system and silicon grating foils are prepared to measure the image transfer function. Using photoetching and ion beam etching processes, the silicon grating foils with check and stripe pattern were prepared on thin silicon foil. The thickness of thin silicon foil was 3 to 4 μm and the pattern’s etching depth was about 1 μm. The size of check pattern was 25 μm×25 μm and the width of stripe pattern was 5 μm. The parameters of photoetching and ion beam etching processes were studied to control the precision of patterns. And silicon grating foils were used to measure the image transfer function by XUV radiography system on “Shenguang Ⅱ” high power laser facility in 2000.
2005,
17.
Abstract:
Considering gases retention in plastic microsphere in ICF experiment,the diffusion and permeation behavior of water vapor in hydrocarbon (CH) film,polyvinyl alcohol (PVA) film and polystyrene (PS) film at 40 ℃ 90% relative humidity was studied in this paper. On the basis of experimental data, the permeatibility coefficients of water vapor in three films were worked out,which are separately 1.906×10－13，5.950×10－15，3.432×10－14 mol·m/(m2·s·Pa)，.And the relative humidity of middle layer (PVA) of 53.06% in threelayer structure, which is analogous to multilayer plastic microsphere's, under 40 ℃ 90% relative humidity environmental condition was figured out using an approximate model of multilayer packaging structure. Moreover,the relationship between thickness of CH film and relat
Considering gases retention in plastic microsphere in ICF experiment,the diffusion and permeation behavior of water vapor in hydrocarbon (CH) film,polyvinyl alcohol (PVA) film and polystyrene (PS) film at 40 ℃ 90% relative humidity was studied in this paper. On the basis of experimental data, the permeatibility coefficients of water vapor in three films were worked out,which are separately 1.906×10－13，5.950×10－15，3.432×10－14 mol·m/(m2·s·Pa)，.And the relative humidity of middle layer (PVA) of 53.06% in threelayer structure, which is analogous to multilayer plastic microsphere's, under 40 ℃ 90% relative humidity environmental condition was figured out using an approximate model of multilayer packaging structure. Moreover,the relationship between thickness of CH film and relat
2005,
17.
Abstract:
Transient collisional excitation(TCE) has proved to be an efficient method to significantly save driving energy. In this paper, Ne-like Ge 19.6 nm X-ray laser driven by picosecond Nd:glass laser pulse at 1.053 μm are simulated. The local gain greater than 60 cm-1 is predicted and calculations of the propagation of X-ray laser, including refraction effects, are done to understand which regions have the right combination of high gain and low density gradients for an optimum contribution to the X-ray laser output.
Transient collisional excitation(TCE) has proved to be an efficient method to significantly save driving energy. In this paper, Ne-like Ge 19.6 nm X-ray laser driven by picosecond Nd:glass laser pulse at 1.053 μm are simulated. The local gain greater than 60 cm-1 is predicted and calculations of the propagation of X-ray laser, including refraction effects, are done to understand which regions have the right combination of high gain and low density gradients for an optimum contribution to the X-ray laser output.
2005,
17.
Abstract:
SBS process was simulated numerically based on a one-dimensional transient model. The influence of Brillouin media on SBS characteristics was studied. A variety of media, such as FC-72, FC-75, CCl4, CS2, Acetone, Benzene, and mixture liquid of CCl4/Ethanol, are investigated experimentally with a Nd∶YAG Q-switched laser, and comparison is made between the SBS characteristics, such as the SBS pulse-width, the energy reflectivity and the SBS pulse shape. It is shown that a large gain factor corresponds to a small absorption coefficient and a large SBS energy reflectivity; a large absorption coefficient corresponds to a short SBS pulse-width; and a short phonon lifetime corresponds to a short SBS rise time. The modulation of SBS pulse shape tends to occur with a short phonon lifetime.
SBS process was simulated numerically based on a one-dimensional transient model. The influence of Brillouin media on SBS characteristics was studied. A variety of media, such as FC-72, FC-75, CCl4, CS2, Acetone, Benzene, and mixture liquid of CCl4/Ethanol, are investigated experimentally with a Nd∶YAG Q-switched laser, and comparison is made between the SBS characteristics, such as the SBS pulse-width, the energy reflectivity and the SBS pulse shape. It is shown that a large gain factor corresponds to a small absorption coefficient and a large SBS energy reflectivity; a large absorption coefficient corresponds to a short SBS pulse-width; and a short phonon lifetime corresponds to a short SBS rise time. The modulation of SBS pulse shape tends to occur with a short phonon lifetime.
2005,
17.
Abstract:
The optimal design of the output cavity of a Ka-band second harmonic three-cavity gyroklystron amplifier is finished based on beam-wave interaction characteristics of the amplifier in this paper. The diffraction Q variation with the size of the diffraction output aperture for the RF power at the end of the output cavity is calculated. By PIC simulations, the output characteristics of the amplifier such as the frequency response etc are analyzed. At 35.0 GHz, a peak output power of more than 220 kW with an electronic efficiency of about 23%, and a gain of 23 dB, and a 3 dB bandwidth of 110 MHz (0.3%) is obtained with a 70 kV, 15 A electron beam at a magnetic field of 0.685 T and a beam velocity ratio of 1.45.
The optimal design of the output cavity of a Ka-band second harmonic three-cavity gyroklystron amplifier is finished based on beam-wave interaction characteristics of the amplifier in this paper. The diffraction Q variation with the size of the diffraction output aperture for the RF power at the end of the output cavity is calculated. By PIC simulations, the output characteristics of the amplifier such as the frequency response etc are analyzed. At 35.0 GHz, a peak output power of more than 220 kW with an electronic efficiency of about 23%, and a gain of 23 dB, and a 3 dB bandwidth of 110 MHz (0.3%) is obtained with a 70 kV, 15 A electron beam at a magnetic field of 0.685 T and a beam velocity ratio of 1.45.
2005,
17.
Abstract:
In the paper, the bandwidths of highelectromagnetic pulses generated by high altitude nuclear explode, lightning, ESD have been investigated. In terms of the energy spectrums of the highEMP and the viewpoint of measurement validity, authors have put forward two new concepts, energy effective bandwidth and dynamic range effective bandwidth, to represent the bandwidth of the highEMP. Both of the effective bandwidths of the highEMP specified in IEC61000－4－4, MIL－STD－464, IEC61312－1 and IEC61000－4－2, have been calculated. In addition, it has been known that the rising time of above highEMP has a little impact on two kind of the effective bandwidth, and it is neglectable within a certain range. At last, the measurement bandwidths of above highEMP are given in according with t
In the paper, the bandwidths of highelectromagnetic pulses generated by high altitude nuclear explode, lightning, ESD have been investigated. In terms of the energy spectrums of the highEMP and the viewpoint of measurement validity, authors have put forward two new concepts, energy effective bandwidth and dynamic range effective bandwidth, to represent the bandwidth of the highEMP. Both of the effective bandwidths of the highEMP specified in IEC61000－4－4, MIL－STD－464, IEC61312－1 and IEC61000－4－2, have been calculated. In addition, it has been known that the rising time of above highEMP has a little impact on two kind of the effective bandwidth, and it is neglectable within a certain range. At last, the measurement bandwidths of above highEMP are given in according with t
2005,
17.
Abstract:
Electron beam performance parameters of a double-anode magnetron injection gun(MIG) for 8 mm second harmonic gyroklystron amplifier is calculated. According to these parameters, double-anode MIG is designed and optimized by using EGUN simulation. The ratio of perpendicular to parallel velocity is 1.45 and velocity spread is 5.4%. Many factors such as electrode shape, magnetic distribution, beam current, control anode voltage, second anode voltage influenced electron gun performance are discussed. The results show that electron beam performance is sensitive to these factors．
Electron beam performance parameters of a double-anode magnetron injection gun(MIG) for 8 mm second harmonic gyroklystron amplifier is calculated. According to these parameters, double-anode MIG is designed and optimized by using EGUN simulation. The ratio of perpendicular to parallel velocity is 1.45 and velocity spread is 5.4%. Many factors such as electrode shape, magnetic distribution, beam current, control anode voltage, second anode voltage influenced electron gun performance are discussed. The results show that electron beam performance is sensitive to these factors．
2005,
17.
Abstract:
This paper studies the combined TM01-TE11 mode converter, which consists of two bent circular waveguides with a straight circular waveguide between them. Keeping the axes parallel of both the output and the input ports, its structure is analyzed and power conversion efficiency is calculated by theory and simulation. The results from both methods are in good agreement. Considering of higher-order modes coupling and the power attenuation of the straight circular copper waveguide, the output value of the overall power conversion efficiency is 93.8% at 3.75 GHz when the inner diameter is 9.0 cm and the axial distance between the two ports is up to 10.57 m.
This paper studies the combined TM01-TE11 mode converter, which consists of two bent circular waveguides with a straight circular waveguide between them. Keeping the axes parallel of both the output and the input ports, its structure is analyzed and power conversion efficiency is calculated by theory and simulation. The results from both methods are in good agreement. Considering of higher-order modes coupling and the power attenuation of the straight circular copper waveguide, the output value of the overall power conversion efficiency is 93.8% at 3.75 GHz when the inner diameter is 9.0 cm and the axial distance between the two ports is up to 10.57 m.
2005,
17.
Abstract:
A method of improving radiation from TM01 model conical horn is presented, drielectric lens consisted of a number of sectors locates on aperture plane of conical horn, appropriate thickness of each sector is choosed ,the conical horn can radiate circular polarized pattern,with a boresigh peak . Radition fields of the horn are gived by analytic formulae and analytic results agree well with that of numerical simulations ,the geak pattern gain of the horn with multi-Sector dielectric lens is about 19.6dB,bandwidth is approximately 15.8%(S11<0.2),aperture efficiecy is 31.8% at 5GHz．
A method of improving radiation from TM01 model conical horn is presented, drielectric lens consisted of a number of sectors locates on aperture plane of conical horn, appropriate thickness of each sector is choosed ,the conical horn can radiate circular polarized pattern,with a boresigh peak . Radition fields of the horn are gived by analytic formulae and analytic results agree well with that of numerical simulations ,the geak pattern gain of the horn with multi-Sector dielectric lens is about 19.6dB,bandwidth is approximately 15.8%(S11<0.2),aperture efficiecy is 31.8% at 5GHz．
2005,
17.
Abstract:
The background and character of five different electron optic softwares(TWTCAD, EGUN, CAMEO, Workstation, Orprogr) were introduced, and the simulation of eleven different construction guns were present by the five softwares. After compared the perveance, gunshot and beam waist radius computed by these softwares with the experiment result, it gives the conclusion that different electron optic software has different precision in computing various electron gun, and then provides the error range of each sofwares, which shows that in the perveance, EGUN and Orprogr has the higher precision, its absolute average error is 7.18% and 7.4%. In the gunshot, TWTCAD is the best, which is 5.69%. In the beam waist radius, the Orprogr’s absoulte average error is 47.43%, is the worst one, but the Workstat
The background and character of five different electron optic softwares(TWTCAD, EGUN, CAMEO, Workstation, Orprogr) were introduced, and the simulation of eleven different construction guns were present by the five softwares. After compared the perveance, gunshot and beam waist radius computed by these softwares with the experiment result, it gives the conclusion that different electron optic software has different precision in computing various electron gun, and then provides the error range of each sofwares, which shows that in the perveance, EGUN and Orprogr has the higher precision, its absolute average error is 7.18% and 7.4%. In the gunshot, TWTCAD is the best, which is 5.69%. In the beam waist radius, the Orprogr’s absoulte average error is 47.43%, is the worst one, but the Workstat
2005,
17.
Abstract:
The propagation of electromagnetic pulses in uniform magnetized plasma is studied using the finite-difference timedomain (FDTD) method by means of Z transforms. The Z transform formulation of FDTD method is derived. The reflection and transmission coefficients are computed for electromagnetic waves through the magnetized plasma layer by discrete Fourier transform. The comparison of numerical results with analytical values is presented．
The propagation of electromagnetic pulses in uniform magnetized plasma is studied using the finite-difference timedomain (FDTD) method by means of Z transforms. The Z transform formulation of FDTD method is derived. The reflection and transmission coefficients are computed for electromagnetic waves through the magnetized plasma layer by discrete Fourier transform. The comparison of numerical results with analytical values is presented．
2005,
17.
Abstract:
The effects of microwave irradiation on the certain integrate circuit radio fuse from aspects of service and normal working state are studied. The damaged and accidental explosion threshold values for microwave irradiation on the radio fuse under test are determined, which are 140~150 kW/cm2 and 100 kW/cm2 respectively. The effecting mechanism of microwave irradiation is analyzed, which shows that the high-frequency module and low-frequency module of radio fuse can be destroyed by antenna coupling for microwave irradiation. Experiments show that microwave irradiation can lead to false action of electronic modules and result in malfunction of explosion executing-device, that is the ultimate reason of accidental explosion for radio fuse under test.
The effects of microwave irradiation on the certain integrate circuit radio fuse from aspects of service and normal working state are studied. The damaged and accidental explosion threshold values for microwave irradiation on the radio fuse under test are determined, which are 140~150 kW/cm2 and 100 kW/cm2 respectively. The effecting mechanism of microwave irradiation is analyzed, which shows that the high-frequency module and low-frequency module of radio fuse can be destroyed by antenna coupling for microwave irradiation. Experiments show that microwave irradiation can lead to false action of electronic modules and result in malfunction of explosion executing-device, that is the ultimate reason of accidental explosion for radio fuse under test.
2005,
17.
Abstract:
This paper is mainly concerned about the theoretical and experimental research of a novel high-power microwave device of the X-band five-unit Transit-time Tube Oscillator (TTTO), which is based on the transit-time effect. Firstly, the structure model of this kind of oscillator is put forward, and the high-frequency characteristics of the resonator (or cavities) are investigated, which is TM01-3π/5 mode. Secondly, resorting to the one-dimension analysis, the interactions between the electrons and the field of different modes in the resonator are researched. It shows that this TTTO can generate high power microwave. Thirdly, this TTTO is simulated, optimized and designed by the particle simulation code. Finally, the experimental research is carried out. After a series of adjustment, employi
This paper is mainly concerned about the theoretical and experimental research of a novel high-power microwave device of the X-band five-unit Transit-time Tube Oscillator (TTTO), which is based on the transit-time effect. Firstly, the structure model of this kind of oscillator is put forward, and the high-frequency characteristics of the resonator (or cavities) are investigated, which is TM01-3π/5 mode. Secondly, resorting to the one-dimension analysis, the interactions between the electrons and the field of different modes in the resonator are researched. It shows that this TTTO can generate high power microwave. Thirdly, this TTTO is simulated, optimized and designed by the particle simulation code. Finally, the experimental research is carried out. After a series of adjustment, employi
2005,
17.
Abstract:
In the numerical simulation of thermal blooming effects, how to choose the grid spacing and other computing parameters correctly is introduced. Based on the sample principles of numerical calculation, the choice of computing parameters is analyzed. Combining the blooming distortion phase distribution for a Gaussian beam and a uniform irradiance circular beam, the relation between the grid spacing and Bradley-Hermann distortion number is deduce. The correct grid spacing could be chosen from the value of the thermal distortion number. In addiaion, we can correctly evaluate the effects of laser propagation in the neal atmosphere from the numerical results. The results show that the difference of the numerical results with same grid numbers and different grid spacing is relatively big. Moreove
In the numerical simulation of thermal blooming effects, how to choose the grid spacing and other computing parameters correctly is introduced. Based on the sample principles of numerical calculation, the choice of computing parameters is analyzed. Combining the blooming distortion phase distribution for a Gaussian beam and a uniform irradiance circular beam, the relation between the grid spacing and Bradley-Hermann distortion number is deduce. The correct grid spacing could be chosen from the value of the thermal distortion number. In addiaion, we can correctly evaluate the effects of laser propagation in the neal atmosphere from the numerical results. The results show that the difference of the numerical results with same grid numbers and different grid spacing is relatively big. Moreove
2005,
17.
Abstract:
The thermal distortions of mirror substrates with such materials as silicon, copper, tungsten and beryllium oxide are calculated and analyzed by use of finite element methods. The results show that when the power of input laser with the diameter of 17 cm gets up to 2 kW, and the reflectivity of the mirrors is 93%, the central maximum thermal distortions of the mirror substrates are separately 0.984 μm, 3.32 μm, 1.55 μm and 1.88 μm, respectively, under the radiation time of 10 seconds. By comparison, the thermal distortion of silicon substrate is the smallest, which would be a kind of more promising material for mirror substrates. And the thermal deformation of Cu substrate is the largest, while those of W and BeO are between Si and Cu. But the materials of W and BeO have high force int
The thermal distortions of mirror substrates with such materials as silicon, copper, tungsten and beryllium oxide are calculated and analyzed by use of finite element methods. The results show that when the power of input laser with the diameter of 17 cm gets up to 2 kW, and the reflectivity of the mirrors is 93%, the central maximum thermal distortions of the mirror substrates are separately 0.984 μm, 3.32 μm, 1.55 μm and 1.88 μm, respectively, under the radiation time of 10 seconds. By comparison, the thermal distortion of silicon substrate is the smallest, which would be a kind of more promising material for mirror substrates. And the thermal deformation of Cu substrate is the largest, while those of W and BeO are between Si and Cu. But the materials of W and BeO have high force int
2005,
17.
Abstract:
ZrO2 films were prepared by electron beam evaporation method at different oxygen partial pressures. Through the measurement of XRD, surface thermal lensing technique, optical spectra and laser irradiate resistance testing, the microstructure, refractive index, absorption and laser induced damage threshold were measured. The experiment results indicate that the films are multicrystal, and the tetragonal is dominant. With the oxygen partial pressure increasing, the crystalline, refractive index and weak absorption are all decreasing. The laser induced damage threshold (LIDT) increase with the oxygen partial pressure increase at first, and the LIDT reaches the maximum value 26.7 J/cm２ nearby oxygen partial pressure of 9×10－3 Pa, but the LIDT decreases when oxygen partial pressure continu
ZrO2 films were prepared by electron beam evaporation method at different oxygen partial pressures. Through the measurement of XRD, surface thermal lensing technique, optical spectra and laser irradiate resistance testing, the microstructure, refractive index, absorption and laser induced damage threshold were measured. The experiment results indicate that the films are multicrystal, and the tetragonal is dominant. With the oxygen partial pressure increasing, the crystalline, refractive index and weak absorption are all decreasing. The laser induced damage threshold (LIDT) increase with the oxygen partial pressure increase at first, and the LIDT reaches the maximum value 26.7 J/cm２ nearby oxygen partial pressure of 9×10－3 Pa, but the LIDT decreases when oxygen partial pressure continu
2005,
17.
Abstract:
As the fundamentals of the fabrication of monolithically integrated optical receiver, a photodiode has been fabricated using laser assisted microprocessing. Laser induced local zinc diffusion has been used to form the p-n junction of the photodiode. The diffusion process was implemented by using the focused laser spot to heat the diffusion window. A spin-on film doped by Zn was used as the diffusion source. Lithography, passivation, electrodes fabrication and packaging are conventional, as the wafers don't endure high temperature in these steps. The responsivity of the fabricated Planar InGaAs/InP PIN photodiodes arrived 0.21 A/W. It was found that some factors in the laser induced diffusion process caused the low performance of the photodiodes. Then improvements including the automatic co
As the fundamentals of the fabrication of monolithically integrated optical receiver, a photodiode has been fabricated using laser assisted microprocessing. Laser induced local zinc diffusion has been used to form the p-n junction of the photodiode. The diffusion process was implemented by using the focused laser spot to heat the diffusion window. A spin-on film doped by Zn was used as the diffusion source. Lithography, passivation, electrodes fabrication and packaging are conventional, as the wafers don't endure high temperature in these steps. The responsivity of the fabricated Planar InGaAs/InP PIN photodiodes arrived 0.21 A/W. It was found that some factors in the laser induced diffusion process caused the low performance of the photodiodes. Then improvements including the automatic co
2005,
17.
Abstract:
The principle and the linear model of two photo laser induced flluorescence(TP-LIF) were presented and discussed in this paper. The CO Q-branch (0,0) band of the B1∑+←←X1∑＋ transition was excited near 230 nm and the B1∑+→A1Π band fluorescence was detected at around 483nm. Through the analysis of the fluorescence spectrum and intensity, the effects of laser intensity, laser wavelength and the temperature on measurement were discussed. Finally the CO distribution was measured in a methane-air flame, which shows a good agreement with the results measured by other method. It was demonstrated that in the linear model of TP-LIF, the quenching effects and the other effects can be avoided. TP-LIF can be used to detect the minor species concentration conveniently.
The principle and the linear model of two photo laser induced flluorescence(TP-LIF) were presented and discussed in this paper. The CO Q-branch (0,0) band of the B1∑+←←X1∑＋ transition was excited near 230 nm and the B1∑+→A1Π band fluorescence was detected at around 483nm. Through the analysis of the fluorescence spectrum and intensity, the effects of laser intensity, laser wavelength and the temperature on measurement were discussed. Finally the CO distribution was measured in a methane-air flame, which shows a good agreement with the results measured by other method. It was demonstrated that in the linear model of TP-LIF, the quenching effects and the other effects can be avoided. TP-LIF can be used to detect the minor species concentration conveniently.
2005,
17.
Abstract:
The analytical expression of the temperature rise of the heat sink of a diode laser array has been obtained by solving the heat conduction equation. The influence of convection heat transfer coefficient on the temperature rise of the top and the bottom surfaces has been analyzed. The temperature difference between the top and the bottom changes little when the convection heat transfer coefficient reaches certain value. The temperature rise decreases as the convection heat transfer coefficient increases. All of the results obtained are in accordance with that by the finite element method and confirmed by the experiment.
The analytical expression of the temperature rise of the heat sink of a diode laser array has been obtained by solving the heat conduction equation. The influence of convection heat transfer coefficient on the temperature rise of the top and the bottom surfaces has been analyzed. The temperature difference between the top and the bottom changes little when the convection heat transfer coefficient reaches certain value. The temperature rise decreases as the convection heat transfer coefficient increases. All of the results obtained are in accordance with that by the finite element method and confirmed by the experiment.
2005,
17.
Abstract:
Range gating is a kind of effective method that can eliminate backscattered light and increase the SNR of the range gated laser imaging system. The theory of range gating is described and the key techniques for range gating are analyzed in this paper. On this basis, a few schemes are designed for range gated imaging system such as producing laser pulse by modulated electrical source or mechanical pulsewidth modulator and feasibility of the pulse modulating methods is approved by experiments. Of particular importance, the mechanical modulating method is useful when the light source of active imaging system is CW diode laser. The target image at range of 1 509 m and 675 m is acquired by range gated imaging system. The shortcomings and improvement of these schemes are also presented．
Range gating is a kind of effective method that can eliminate backscattered light and increase the SNR of the range gated laser imaging system. The theory of range gating is described and the key techniques for range gating are analyzed in this paper. On this basis, a few schemes are designed for range gated imaging system such as producing laser pulse by modulated electrical source or mechanical pulsewidth modulator and feasibility of the pulse modulating methods is approved by experiments. Of particular importance, the mechanical modulating method is useful when the light source of active imaging system is CW diode laser. The target image at range of 1 509 m and 675 m is acquired by range gated imaging system. The shortcomings and improvement of these schemes are also presented．
2005,
17.
Abstract:
In this paper, radiation effects of 1 MeV electron on short wavelength Hg1-xCdxTe photovoltaic detectors have been studied. Response spectrum, currentvoltage characterization and detectivity were measured before and after irradiation to analyze the radiation effects. It's been observed that after irradiation, the response spectra of detectors become narrower at shot wavelength while the peak and cutoff wavelength have no noticeable change. The dark current of devices increases with the irradiation dosage increasing and the detectivity thus decreases.
In this paper, radiation effects of 1 MeV electron on short wavelength Hg1-xCdxTe photovoltaic detectors have been studied. Response spectrum, currentvoltage characterization and detectivity were measured before and after irradiation to analyze the radiation effects. It's been observed that after irradiation, the response spectra of detectors become narrower at shot wavelength while the peak and cutoff wavelength have no noticeable change. The dark current of devices increases with the irradiation dosage increasing and the detectivity thus decreases.
2005,
17.
Abstract:
The heat-deformation P-V value of Si mirror(80 mm×12.5 mm) fixed in radialfixing way analyzed by ANSYS is 0.109 3 μm, with net irradiation heat 100 W in 5 s by a -40 mm and co-axial uniform laser. And 0.138 8 μm by axialfixing way and 0.121 μm in three points supporting respectively. The experimental result to the Si mirror(75 mm×12.5 mm), fixed in radial-fixing way is 0.32 μm with 100 W heat in 5 s by a 17 mm×20 mm and co-axial uniform laser, and 0.63 μm in axial-fixing way. The experimental mirror deflection is 0.63 μrad by radial-fixing way and 0.28 μrad by axial-fixing way. The deflection is the smallest by threecone supporting way．
The heat-deformation P-V value of Si mirror(80 mm×12.5 mm) fixed in radialfixing way analyzed by ANSYS is 0.109 3 μm, with net irradiation heat 100 W in 5 s by a -40 mm and co-axial uniform laser. And 0.138 8 μm by axialfixing way and 0.121 μm in three points supporting respectively. The experimental result to the Si mirror(75 mm×12.5 mm), fixed in radial-fixing way is 0.32 μm with 100 W heat in 5 s by a 17 mm×20 mm and co-axial uniform laser, and 0.63 μm in axial-fixing way. The experimental mirror deflection is 0.63 μrad by radial-fixing way and 0.28 μrad by axial-fixing way. The deflection is the smallest by threecone supporting way．
2005,
17.
Abstract:
Serial optical fiber transmission technology will be used to transfer data from the detector electronics systems to the trigger system in the Beijing Spectrometer Ⅲ. This technology has the advantages of cutting off the ground loops between the electronics systems and the trigger system, improving the system immunity to electro-magnetic interference and lengthening the transfer distance.Some important aspects of this technology are carefully studied, such as the bit error rate, error report,synchronization back，delay skew of channels and phase stability.Design for single line self-synchronizing back is given,which makes the system more robust.The skew of channels is half a period.So the synchronous parellel data can be gotten if the rising of sample clock is set at the middle of the stab
Serial optical fiber transmission technology will be used to transfer data from the detector electronics systems to the trigger system in the Beijing Spectrometer Ⅲ. This technology has the advantages of cutting off the ground loops between the electronics systems and the trigger system, improving the system immunity to electro-magnetic interference and lengthening the transfer distance.Some important aspects of this technology are carefully studied, such as the bit error rate, error report,synchronization back，delay skew of channels and phase stability.Design for single line self-synchronizing back is given,which makes the system more robust.The skew of channels is half a period.So the synchronous parellel data can be gotten if the rising of sample clock is set at the middle of the stab
2005,
17.
Abstract:
In this article, an Nd∶YAG laser is used as light source of the probe system. The main switch signal of the pulsed accelerator can be chosen with specific time delay to trigger the laser system after a 100 ns innate time delay of the laser outer-triggered controlling circuit is attained. In the experiment the triggering signal of Q-switch, the laser light signal, the triggering signal of main switch of the accelerator and load current are temporally associated with an oscilloscope. The delay time of the adjustment system is based on results of measurement of the time association. The synchronization of 9.6 ns between light pulse of probe system and accelerator load current is realized.
In this article, an Nd∶YAG laser is used as light source of the probe system. The main switch signal of the pulsed accelerator can be chosen with specific time delay to trigger the laser system after a 100 ns innate time delay of the laser outer-triggered controlling circuit is attained. In the experiment the triggering signal of Q-switch, the laser light signal, the triggering signal of main switch of the accelerator and load current are temporally associated with an oscilloscope. The delay time of the adjustment system is based on results of measurement of the time association. The synchronization of 9.6 ns between light pulse of probe system and accelerator load current is realized.
2005,
17.
Abstract:
The experiments of microsecond conduction time plasma opening switch (POS) which has been operated at 100 kA current level are reported in this paper. As a result, the rise time of load current is between 54 to 76 ns. The maximal POS voltage of 1.38 MV is obtained with the 200 nH inductive load, and a factor of voltage multiplication up to 4.9 is achieved. In addition, a 2D snowplow model of POS conduction phase has been developed. The sequence of snowplow fronts in POS conduction phase is obtained from the simulation. The primary results show that the model has well predictability.
The experiments of microsecond conduction time plasma opening switch (POS) which has been operated at 100 kA current level are reported in this paper. As a result, the rise time of load current is between 54 to 76 ns. The maximal POS voltage of 1.38 MV is obtained with the 200 nH inductive load, and a factor of voltage multiplication up to 4.9 is achieved. In addition, a 2D snowplow model of POS conduction phase has been developed. The sequence of snowplow fronts in POS conduction phase is obtained from the simulation. The primary results show that the model has well predictability.
2005,
17.
Abstract:
This paper describes power matching of the 200 kW generator and RF cavity of HIRFL Injector RF system， working principle of matching measure system as well as matching system improvement and perfecting.It further calculates the input impedance and coupling capacitor of the RF cavity. In order to enhance the reliability and stability in RF system, the problem of D voltageenhancement and RF power transmission,etc are researched in depth. The vector impedance meter is used to measure the cavity matching impedance and the vector voltage to dynamically measure the phasing errors of the power output, then that the D circuit is working at the matching stage can be ensured. With the D voltage of SFC raising from 50~65 kV (unstable) to 105 kV (stable), SFC's high efficiency is guaranteed．
This paper describes power matching of the 200 kW generator and RF cavity of HIRFL Injector RF system， working principle of matching measure system as well as matching system improvement and perfecting.It further calculates the input impedance and coupling capacitor of the RF cavity. In order to enhance the reliability and stability in RF system, the problem of D voltageenhancement and RF power transmission,etc are researched in depth. The vector impedance meter is used to measure the cavity matching impedance and the vector voltage to dynamically measure the phasing errors of the power output, then that the D circuit is working at the matching stage can be ensured. With the D voltage of SFC raising from 50~65 kV (unstable) to 105 kV (stable), SFC's high efficiency is guaranteed．
2005,
17.
Abstract:
The simulation of vacuum ultraviolet (VUV) and the working mechanism, technical parameters as well as characters of the gas-jet device for simulating vacuum ultraviolet were introduced. The outgas, mass loss ratio (fSAML), interlayer shear strength (δILSS), and variation in surface state of epoxy cast ingot (EP648) and carbon/epoxy composites (C/E648) under VUV were studied using the above device as well as other analysis means. Results show that VUV exposure resulted in obvious outgas effect, while mass loss ratio shows a trend of ascending followed by leveling off; the mass loss of EP648 is 3.4 times of that of C/E648 under dose of 17 280 esh; δILSS of C/E648 after exposure is decreased to 13.3% of that before the exposure; the epoxy is damaged greatly, while the surface of carbon fibe
The simulation of vacuum ultraviolet (VUV) and the working mechanism, technical parameters as well as characters of the gas-jet device for simulating vacuum ultraviolet were introduced. The outgas, mass loss ratio (fSAML), interlayer shear strength (δILSS), and variation in surface state of epoxy cast ingot (EP648) and carbon/epoxy composites (C/E648) under VUV were studied using the above device as well as other analysis means. Results show that VUV exposure resulted in obvious outgas effect, while mass loss ratio shows a trend of ascending followed by leveling off; the mass loss of EP648 is 3.4 times of that of C/E648 under dose of 17 280 esh; δILSS of C/E648 after exposure is decreased to 13.3% of that before the exposure; the epoxy is damaged greatly, while the surface of carbon fibe
2005,
17.
Abstract:
To correct the beam orbit in the storage ring, it is required to measure offset of every quadrupole's megnetic center relative to electrical center of its adjacent beam position monitor (BPM). By varying individual quadrupole maganet strength, the offsets could be calculated from the corresponding effects on the beam orbit.A program,which based on the hardware of BBA in HLS storage ring and EPICS, was developed with Lab View 6.1 on Windows system to control the measurement. The program manages quadrupole magnet strength, and performs a least squares fit of the result data points to a parabola, which indicates the offset, i.e. position of quadrupole magnetic center. These offsets were measured with an accuracy of better than 100 μm．
To correct the beam orbit in the storage ring, it is required to measure offset of every quadrupole's megnetic center relative to electrical center of its adjacent beam position monitor (BPM). By varying individual quadrupole maganet strength, the offsets could be calculated from the corresponding effects on the beam orbit.A program,which based on the hardware of BBA in HLS storage ring and EPICS, was developed with Lab View 6.1 on Windows system to control the measurement. The program manages quadrupole magnet strength, and performs a least squares fit of the result data points to a parabola, which indicates the offset, i.e. position of quadrupole magnetic center. These offsets were measured with an accuracy of better than 100 μm．
2005,
17.
Abstract:
Pure permanent-magnet undulator consists of many magnets. The unavoidable remanence divergence of these magnets causes the undulator magnetic field error, which will affect the functional mode of the storage ring and the quality of the spontaneous emission spectrum. Optimizing permanent-magnet undulator magnets ordering using simulated annealing algorithm before installing undulator magnets, the first field integral can be reduced to 10－6 T·m, the second integral to 10－6 T·m2 and the peak field error to less than 10－4. The optimized results are independent of the initial solution. This paper gives the optimizing process in detail and puts forward a method to quickly calculate the peak field error and field integral according to the magnet remanence.
Pure permanent-magnet undulator consists of many magnets. The unavoidable remanence divergence of these magnets causes the undulator magnetic field error, which will affect the functional mode of the storage ring and the quality of the spontaneous emission spectrum. Optimizing permanent-magnet undulator magnets ordering using simulated annealing algorithm before installing undulator magnets, the first field integral can be reduced to 10－6 T·m, the second integral to 10－6 T·m2 and the peak field error to less than 10－4. The optimized results are independent of the initial solution. This paper gives the optimizing process in detail and puts forward a method to quickly calculate the peak field error and field integral according to the magnet remanence.
