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RSS2001 Vol. 13, No. 02
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2001,
13.
Abstract:
The paper presents a model which simulate the case of a intense electron beam striking the bremsstrahlung convert target to generate backstreaming ions. The redistribution of space charge potential with backstreaming ions in front of target, the dynamic behavior of the backstreaming ions, the effect of backstreaming ions on the focal spot at the target are obtained according to this model. A method of dynamic magnetic field compensation for reducing the influence of backstreaming ions on the focal spot is presented, whose effect is also simulated. The simulation result shows that the method is very effective.
The paper presents a model which simulate the case of a intense electron beam striking the bremsstrahlung convert target to generate backstreaming ions. The redistribution of space charge potential with backstreaming ions in front of target, the dynamic behavior of the backstreaming ions, the effect of backstreaming ions on the focal spot at the target are obtained according to this model. A method of dynamic magnetic field compensation for reducing the influence of backstreaming ions on the focal spot is presented, whose effect is also simulated. The simulation result shows that the method is very effective.
2001,
13.
Abstract:
New type，soft-switching capacitor-charging techniques are introduced. Major parameters of basic constant-current charging circuit are calculated. Simulated and measured waveforms are given. Under the adverse condition of high repetition rate and small capacitance, methods of improving the performance of basic circuit are proposed while keeping the advantages of constant current charging.
New type，soft-switching capacitor-charging techniques are introduced. Major parameters of basic constant-current charging circuit are calculated. Simulated and measured waveforms are given. Under the adverse condition of high repetition rate and small capacitance, methods of improving the performance of basic circuit are proposed while keeping the advantages of constant current charging.
2001,
13.
Abstract:
In roder to simulate the errosion effects of low earth orbital atomic oxygen and study the modification effects of atomic oxygen with materials surface, an atomic oxygen beam with flix in 1013 ~1016atom/cm2× s and energy in 6~10eV has been developed by means of microwave coaxial coupling discharge of molecular oxygen plus magnetic confine and collision and reflection with a biased metal target. The produced oxygen plasma has been measured by double probe technique. The obtained oxygen beam has been calibrateed by measuring the reaction rate of kaptan with the beam. The results shows that an atomic oxygen beam with flux in 2 1016 atoms× cm- 2× s- 1 and energy in 6~20eV can be obtained by this facility.
In roder to simulate the errosion effects of low earth orbital atomic oxygen and study the modification effects of atomic oxygen with materials surface, an atomic oxygen beam with flix in 1013 ~1016atom/cm2× s and energy in 6~10eV has been developed by means of microwave coaxial coupling discharge of molecular oxygen plus magnetic confine and collision and reflection with a biased metal target. The produced oxygen plasma has been measured by double probe technique. The obtained oxygen beam has been calibrateed by measuring the reaction rate of kaptan with the beam. The results shows that an atomic oxygen beam with flux in 2 1016 atoms× cm- 2× s- 1 and energy in 6~20eV can be obtained by this facility.
2001,
13.
Abstract:
The electron beam is deflected into and out interaction region by toroid in the electron cooling device for HIRFL-CSR. The magnetic field distribution in toroid and interface among toroid and solenoids is very complicated. The properties of the magnetic field in toroid give rise to a change in the transverse energy of the electron. A program was developed to study the spatial transverse energy distribution of electron in the beam as it moves through the toroid. The space charge effect was taken into account in the calculation. The simulation results show that the increase of the transverse energy can be minimized when the ratio of the central length of toroid and the cyclotron wavelength of electron is integer.
The electron beam is deflected into and out interaction region by toroid in the electron cooling device for HIRFL-CSR. The magnetic field distribution in toroid and interface among toroid and solenoids is very complicated. The properties of the magnetic field in toroid give rise to a change in the transverse energy of the electron. A program was developed to study the spatial transverse energy distribution of electron in the beam as it moves through the toroid. The space charge effect was taken into account in the calculation. The simulation results show that the increase of the transverse energy can be minimized when the ratio of the central length of toroid and the cyclotron wavelength of electron is integer.
2001,
13.
Abstract:
High-resolution X-ray photographing needs to focus intense relativistic electron beams of several thousand amperes on bremsstrahlung converter target, thereon forming a small and stable spot. In the ideal case,electron beams cn be focused to a poing. However, due to the influcence of such factrs as the space charge effect, the beam emittance, the spherical aberration of the lens, and the chromatic aberration, the minimization of the spot size of electron beams is limited. Furthermore, the corkscrew oscillaton of the beam centroid not only leads to the increase of the spot size but also to the distortion of the spot shape. The effects of solenoidal field on the spot size of intense relativistic electronic beams are analyzed and the minimal spot sizes limited by various factors are given. Th
High-resolution X-ray photographing needs to focus intense relativistic electron beams of several thousand amperes on bremsstrahlung converter target, thereon forming a small and stable spot. In the ideal case,electron beams cn be focused to a poing. However, due to the influcence of such factrs as the space charge effect, the beam emittance, the spherical aberration of the lens, and the chromatic aberration, the minimization of the spot size of electron beams is limited. Furthermore, the corkscrew oscillaton of the beam centroid not only leads to the increase of the spot size but also to the distortion of the spot shape. The effects of solenoidal field on the spot size of intense relativistic electronic beams are analyzed and the minimal spot sizes limited by various factors are given. Th
2001,
13.
Abstract:
The article determines the sensitivity of measuring proton(14-32MeV) fluence using thermoluminescence dosimeters(TLD) on theoretical grounds and performs the experiment research..The components, dimensions and dosimeric properties of the TLD used in this experiment are described. The energy losses, absorbed soses and proton in fluence sensitivities are calculated on the theoretical grounds. Two types of TLDs are used for measuring the proton fluence on 35MeV proton accelerator. The scattering beams are acquired by gold foil. The proton fluence uniformity of identical scattering distance and angle are miasured using TLDs. The proton fluence nonuniformity of identical scattering distance and different scattering angle are also measured by TLDs. The proton fluton fluence nonuniformity rations
The article determines the sensitivity of measuring proton(14-32MeV) fluence using thermoluminescence dosimeters(TLD) on theoretical grounds and performs the experiment research..The components, dimensions and dosimeric properties of the TLD used in this experiment are described. The energy losses, absorbed soses and proton in fluence sensitivities are calculated on the theoretical grounds. Two types of TLDs are used for measuring the proton fluence on 35MeV proton accelerator. The scattering beams are acquired by gold foil. The proton fluence uniformity of identical scattering distance and angle are miasured using TLDs. The proton fluence nonuniformity of identical scattering distance and different scattering angle are also measured by TLDs. The proton fluton fluence nonuniformity rations
2001,
13.
Abstract:
The effects of the round edge beam hole on the frequency and wake field are studied using variational method, which allows for rounded iris disk hole without any approximation shape treatment. The frequencies and wakefields of accelerating mode and dipole mode are studied for different edge radius cases, including the flat edge shape that is often used to approximately represent the actual structure geometry. The edge hole shape has weak effect on the frequency, but strong effect on the wakefield. The study shows that the amounts of wakefields are not precise enough with the assumption of the flat beam hole instead of round edge. The shape assumption brings loss factor 15% err for the most dangerous EH16 mode.
The effects of the round edge beam hole on the frequency and wake field are studied using variational method, which allows for rounded iris disk hole without any approximation shape treatment. The frequencies and wakefields of accelerating mode and dipole mode are studied for different edge radius cases, including the flat edge shape that is often used to approximately represent the actual structure geometry. The edge hole shape has weak effect on the frequency, but strong effect on the wakefield. The study shows that the amounts of wakefields are not precise enough with the assumption of the flat beam hole instead of round edge. The shape assumption brings loss factor 15% err for the most dangerous EH16 mode.
2001,
13.
Abstract:
In this paper, the differential relation between optic parameter and lattice parameter in electron storage ring of HLS is presented; the lattice parameter at downriver is evaluated and analyzed when the optic parameter at upriver is changed. Using the expression the lattice parameters is calculated when the Wiggle is inserted, satisfying the need of the improment of NSRL (National Synchrotron Radiation Lab.). Considering this relation, the lattice is designed renewedly in order to reduce the b function where the Wiggler was inserted.
In this paper, the differential relation between optic parameter and lattice parameter in electron storage ring of HLS is presented; the lattice parameter at downriver is evaluated and analyzed when the optic parameter at upriver is changed. Using the expression the lattice parameters is calculated when the Wiggle is inserted, satisfying the need of the improment of NSRL (National Synchrotron Radiation Lab.). Considering this relation, the lattice is designed renewedly in order to reduce the b function where the Wiggler was inserted.
2001,
13.
Abstract:
An optical klystron (OK), which means for harmonic generation FEL, is designed and constructed with NdFeB magnets. The analysis equations for designing the OK are listed. The design result was checked by 3-dimensional electromagnetic computation software, the Opera3d. The buncher of the OK and its induction field in the middle plane of the OK, computed with Opera3d are respectively shown. The measured B-H curve of the magnet used in the computation is given. The computed induction field in the beam axis by Opera3d matches well with the field measured by 0.1mm 0.1mm hall probe. The typical parameters of the optical klystron are listed. The magnet gaps of the three OK undulator sections can be independently tuned from 40mm to 140mm. After the OK spontaneous emission is got at the beam
An optical klystron (OK), which means for harmonic generation FEL, is designed and constructed with NdFeB magnets. The analysis equations for designing the OK are listed. The design result was checked by 3-dimensional electromagnetic computation software, the Opera3d. The buncher of the OK and its induction field in the middle plane of the OK, computed with Opera3d are respectively shown. The measured B-H curve of the magnet used in the computation is given. The computed induction field in the beam axis by Opera3d matches well with the field measured by 0.1mm 0.1mm hall probe. The typical parameters of the optical klystron are listed. The magnet gaps of the three OK undulator sections can be independently tuned from 40mm to 140mm. After the OK spontaneous emission is got at the beam
2001,
13.
Abstract:
According to a simple calculation model, both the power spectrum formula and the coherent harmonic radiation formula are derived. With these formulae, the coherent harmonic radiation of asymmetrical optical klystron configuration is discussed. For the storage ring coherent harmonic FEL in Hefei, a method of the coherent harmonic radiation of asymmetrical optical klystron configuration is investigated, and the detailed calculation results are given. Thus adjusting the parameters of optical klystron and outer laser makes the resonant wavelength of radiation section to equal to the second harmonic wavelength of outer laser, and the coherent strengthen factor 109 can be acquired.
According to a simple calculation model, both the power spectrum formula and the coherent harmonic radiation formula are derived. With these formulae, the coherent harmonic radiation of asymmetrical optical klystron configuration is discussed. For the storage ring coherent harmonic FEL in Hefei, a method of the coherent harmonic radiation of asymmetrical optical klystron configuration is investigated, and the detailed calculation results are given. Thus adjusting the parameters of optical klystron and outer laser makes the resonant wavelength of radiation section to equal to the second harmonic wavelength of outer laser, and the coherent strengthen factor 109 can be acquired.
2001,
13.
Abstract:
As the fourth generation light source hard X-ray SASE free-electron laser has many unique properties superior to the 3rd synchrotron radiation: higher brightness (ten orders of magnitude of peak spectral brightness and three~five orders of magnitude of pulse duration shorter than the 3rd synchrotron radiation currently achieved), shorter pulse(two orders of magnitude of pulse duration shorter than the 3rd synchrotron radiation, down to sub-pi-cosecond) , shorter wavelength down to 0.1nm etc.. SASE issbased on the principle of high gain free electron lasers, and technologies of photoinjector and linear accelerator. The development history of SASE, the basic theory, the typical configuration, the main physical characteristics and the requirements for electron beam is described.
As the fourth generation light source hard X-ray SASE free-electron laser has many unique properties superior to the 3rd synchrotron radiation: higher brightness (ten orders of magnitude of peak spectral brightness and three~five orders of magnitude of pulse duration shorter than the 3rd synchrotron radiation currently achieved), shorter pulse(two orders of magnitude of pulse duration shorter than the 3rd synchrotron radiation, down to sub-pi-cosecond) , shorter wavelength down to 0.1nm etc.. SASE issbased on the principle of high gain free electron lasers, and technologies of photoinjector and linear accelerator. The development history of SASE, the basic theory, the typical configuration, the main physical characteristics and the requirements for electron beam is described.
2001,
13.
Abstract:
In this paper, the power spectral density was employed as the specification criterion of the large aperture optical elements. The transfer function of the testing system has been demarcated. Furthermore, the main errors appeared in the testing process and their influences have been discussed in detail. The results show that the low frequency erroe,which caused by the plcement, affect the testing result. And the high frequency error, which caused by the interfeerene, does not have more effect on the testing.
In this paper, the power spectral density was employed as the specification criterion of the large aperture optical elements. The transfer function of the testing system has been demarcated. Furthermore, the main errors appeared in the testing process and their influences have been discussed in detail. The results show that the low frequency erroe,which caused by the plcement, affect the testing result. And the high frequency error, which caused by the interfeerene, does not have more effect on the testing.
2001,
13.
Abstract:
Through the Finite element Analysis (FEA) on the resonator mirror, which absorbs the heat at the front and back surfaces during the operation of high-energy density laser, the thermal displacement distributions are presented under different heat flux and constraint conditions. It is indicated that improving the reflective rate, adopting new mirror substrate material and optimizing the constraint condition of the mirror is an effective method for reducing mirror thermal deformation.
Through the Finite element Analysis (FEA) on the resonator mirror, which absorbs the heat at the front and back surfaces during the operation of high-energy density laser, the thermal displacement distributions are presented under different heat flux and constraint conditions. It is indicated that improving the reflective rate, adopting new mirror substrate material and optimizing the constraint condition of the mirror is an effective method for reducing mirror thermal deformation.
2001,
13.
Abstract:
By using finite Hankel transform, the paper derives the solution to the thermo-mechanically coupled vibrations of an axisymmetric circular plate which is subjected to irradiation of a high power laser beam on one of its surfaces and has boundary conditions of a constant temperature and a special displacement-force confinement on its circumference. Three plates of different materials are calculated. The present analytical and FEM results are in accordance with each other and indicate that the effects of thermo-mechanical coupling on the thermo-elastic vibrations of plates are pertinent to the material properties. For some materials, the effects of thermo-mechanical coupling are of significance, and for others, they are of insignificance.
By using finite Hankel transform, the paper derives the solution to the thermo-mechanically coupled vibrations of an axisymmetric circular plate which is subjected to irradiation of a high power laser beam on one of its surfaces and has boundary conditions of a constant temperature and a special displacement-force confinement on its circumference. Three plates of different materials are calculated. The present analytical and FEM results are in accordance with each other and indicate that the effects of thermo-mechanical coupling on the thermo-elastic vibrations of plates are pertinent to the material properties. For some materials, the effects of thermo-mechanical coupling are of significance, and for others, they are of insignificance.
2001,
13.
Abstract:
The influence of geometry of reflector on pumping performance of Xe flash-lamp array are analyzed by Monto-Carlo simulation methods in this paper. A novel reflector is proposed, which is simile in form to involute, and has advantages of smaller width than that of standard involute. Simulation results by ray-tracing method show that the transport efficiency Em of pumping energy in the reflector of new geometric shape (imitation of involute) is 90% approximately, when its geometric modified index p ³ 0.80 in 6 Xe lamps cavity. The reflectors with section shape of incomplete involute or imitation of involute, as an altermative of standard involute, are useful to increase pumoing energy in Chinese SG-III high power laser facility, when it’s length of pumping cavity is shorter than that n
The influence of geometry of reflector on pumping performance of Xe flash-lamp array are analyzed by Monto-Carlo simulation methods in this paper. A novel reflector is proposed, which is simile in form to involute, and has advantages of smaller width than that of standard involute. Simulation results by ray-tracing method show that the transport efficiency Em of pumping energy in the reflector of new geometric shape (imitation of involute) is 90% approximately, when its geometric modified index p ³ 0.80 in 6 Xe lamps cavity. The reflectors with section shape of incomplete involute or imitation of involute, as an altermative of standard involute, are useful to increase pumoing energy in Chinese SG-III high power laser facility, when it’s length of pumping cavity is shorter than that n
2001,
13.
Abstract:
The laser damage of HfO2 /SiO2 high reflector coating with and without l /2 silica overcoat was studied in detail respectively, the damage threshold and possibility was measured by using a 1064nm longitude mode, 10ns Nd: YAG laser, the laser damage size and morphology were observed and analyzed by using a Normaski microscope, main conclusions are as follows: (1) The l / 2 silica overcoat does affect laser damage threshold of HfO2 /SiO2 high reflector coating significantly，and increase the laser damage threshold of coating up to 1.5 times; (2) According to laser damage morphologies, l / 2 silica overcoat can reduced the serious damage of HfO2 /SiO2 high reflector coating, and prevent catastrophic damage of the hafnia top layer; (3) For multi-shot laser pulse, l / 2 silica overcoat can grea
The laser damage of HfO2 /SiO2 high reflector coating with and without l /2 silica overcoat was studied in detail respectively, the damage threshold and possibility was measured by using a 1064nm longitude mode, 10ns Nd: YAG laser, the laser damage size and morphology were observed and analyzed by using a Normaski microscope, main conclusions are as follows: (1) The l / 2 silica overcoat does affect laser damage threshold of HfO2 /SiO2 high reflector coating significantly，and increase the laser damage threshold of coating up to 1.5 times; (2) According to laser damage morphologies, l / 2 silica overcoat can reduced the serious damage of HfO2 /SiO2 high reflector coating, and prevent catastrophic damage of the hafnia top layer; (3) For multi-shot laser pulse, l / 2 silica overcoat can grea
2001,
13.
Abstract:
Through the analysis and experiments on the far field beam spot drift and deform during the high-energy density chemical oxygen iodine laser operation, the conclusion that the alignment of the reflex mirrors in the resonator takes a very important roles is gotten. It is indicated that to improve the stability of the resonator box and the alignment of the reflex mirrors in the resonator before the laser operation is an effective method for decreasing the output far field beam spot drift and deformation.
Through the analysis and experiments on the far field beam spot drift and deform during the high-energy density chemical oxygen iodine laser operation, the conclusion that the alignment of the reflex mirrors in the resonator takes a very important roles is gotten. It is indicated that to improve the stability of the resonator box and the alignment of the reflex mirrors in the resonator before the laser operation is an effective method for decreasing the output far field beam spot drift and deformation.
2001,
13.
Abstract:
Chaotic dynamics and chaos control have become a great challenge in nonlinear laser systems and its advances are reviewed in this article mainly based on the ring cavity laser systems. The principle and stability conditions for time-delay feedback control are analyzed and applied to chaos control in the laser systems. Other advanced methods of chaos control, such as weak spatial perturbation and occasional proportional feedback technique, are discussed. Prospects of chaos control for applications (such as improvement of laser power and performance , synchronized chaos secure communication and information processing) are pointed out finally.
Chaotic dynamics and chaos control have become a great challenge in nonlinear laser systems and its advances are reviewed in this article mainly based on the ring cavity laser systems. The principle and stability conditions for time-delay feedback control are analyzed and applied to chaos control in the laser systems. Other advanced methods of chaos control, such as weak spatial perturbation and occasional proportional feedback technique, are discussed. Prospects of chaos control for applications (such as improvement of laser power and performance , synchronized chaos secure communication and information processing) are pointed out finally.
2001,
13.
Abstract:
Starting from the cold dispersion relation, which is employed to numerically calculate eigenfrequencies for the double-gqp spil cavity, thereby the resonant frequency for the split cavity TM010 mode are obtained and the distributing character of p -mode are discussed. Accordingly, the split cavity can be used as double-gap output cavity. And then the double-gap output cavity is designed by using the 2.5D, relativistic, fully electromagnetic, PIC code KARAT, and more optimizing the construct of output cavity. At last by modulating the different construct parameters, the cold tests are carried on, and by which the low-QL output cavity of center frequency 3.74GHz and 7.8 of load QL is developed.
Starting from the cold dispersion relation, which is employed to numerically calculate eigenfrequencies for the double-gqp spil cavity, thereby the resonant frequency for the split cavity TM010 mode are obtained and the distributing character of p -mode are discussed. Accordingly, the split cavity can be used as double-gap output cavity. And then the double-gap output cavity is designed by using the 2.5D, relativistic, fully electromagnetic, PIC code KARAT, and more optimizing the construct of output cavity. At last by modulating the different construct parameters, the cold tests are carried on, and by which the low-QL output cavity of center frequency 3.74GHz and 7.8 of load QL is developed.
2001,
13.
Abstract:
During the past few years there has been extraordinary progress in developing fast Z-pinches for intense, high-energy density X-ray sources. The source is produced by converting the imploding Z-pinch material’s kinetic energy into the radiation, as it stagnates on the axis of load. The Sandia Z machine in this configuration routinely produces 2 MJ of soft X-ray with peck powers of ~ 200TW utilizing tungsten wire array loads. The theoretical analysis of the gas-puff Z-Pinch load to produce dense plasma X-ray source on “YANG” accelerator (~1.2MV, 1.5MA, 12 0ns) is researched in this paper. The annular radius, gas density and another parameters of the Z-Pinch load on “YANG” accelerator are presented. These parameters are available for to design a Z-pinch load.
During the past few years there has been extraordinary progress in developing fast Z-pinches for intense, high-energy density X-ray sources. The source is produced by converting the imploding Z-pinch material’s kinetic energy into the radiation, as it stagnates on the axis of load. The Sandia Z machine in this configuration routinely produces 2 MJ of soft X-ray with peck powers of ~ 200TW utilizing tungsten wire array loads. The theoretical analysis of the gas-puff Z-Pinch load to produce dense plasma X-ray source on “YANG” accelerator (~1.2MV, 1.5MA, 12 0ns) is researched in this paper. The annular radius, gas density and another parameters of the Z-Pinch load on “YANG” accelerator are presented. These parameters are available for to design a Z-pinch load.
2001,
13.
Abstract:
In this paper, modulation of the space charge in a magnetically insulated transmission line oscillator (MILO) caused by the radio-frequency field (including the radiation wave field and the space charge wave field) is researched at first. Formula of the first order component of the harmonic current at saturation (nonlinear regime) is obtained. When the space charge wave is considered, it will enhance the harmonic current on condition that the signal is small and the radiation wave is in phase with the space charge wave, but the case is not certain with a large signal. The harmonic current will enhance with the increasing of the voltage on the diode and reduce with the increasing of the operating frequency and the saturation length.
In this paper, modulation of the space charge in a magnetically insulated transmission line oscillator (MILO) caused by the radio-frequency field (including the radiation wave field and the space charge wave field) is researched at first. Formula of the first order component of the harmonic current at saturation (nonlinear regime) is obtained. When the space charge wave is considered, it will enhance the harmonic current on condition that the signal is small and the radiation wave is in phase with the space charge wave, but the case is not certain with a large signal. The harmonic current will enhance with the increasing of the voltage on the diode and reduce with the increasing of the operating frequency and the saturation length.
2001,
13.
Abstract:
There can exist two kinds of ion-acoustic waves in a plasma, i.e. fast mode and slow mode, if the plasma consists of two ion species which masses are greatly different from each other. Fast and slow mode are mainly due to the motions of light ions and heavy ions, respectively. A systematic perturbation method is used to analytically calculate the frequencies and damping rates of the two modes. The method developed by McKinstrie et al, is based upon the expansion of plasma dispersion relation in a power series of Ti /Te, where Ti,e are te ion and electron temperatures. Comparing with the results obtained from numerical solution shows that the formulae obtained in this paper can give more accurate results than previous studies, such as presented by Williams et al.
There can exist two kinds of ion-acoustic waves in a plasma, i.e. fast mode and slow mode, if the plasma consists of two ion species which masses are greatly different from each other. Fast and slow mode are mainly due to the motions of light ions and heavy ions, respectively. A systematic perturbation method is used to analytically calculate the frequencies and damping rates of the two modes. The method developed by McKinstrie et al, is based upon the expansion of plasma dispersion relation in a power series of Ti /Te, where Ti,e are te ion and electron temperatures. Comparing with the results obtained from numerical solution shows that the formulae obtained in this paper can give more accurate results than previous studies, such as presented by Williams et al.
2001,
13.
Abstract:
By use of scheme of grounded capacitor terminal with the preionization and a new low resistance cable, electromagnetism disturbing and earth-potential raising has been restrained, meanwhile the higher efficiency of energy conversion has been gotten. Therefore, satisfy and improve the performance of power conditioning system of high power laser driver in inertial confinement fusion, optimizing power conditioning system of 4×2 layer amplifier. With preionization the flash-lamp current waveform becomes favorable for improving the amplifier efficiency.
By use of scheme of grounded capacitor terminal with the preionization and a new low resistance cable, electromagnetism disturbing and earth-potential raising has been restrained, meanwhile the higher efficiency of energy conversion has been gotten. Therefore, satisfy and improve the performance of power conditioning system of high power laser driver in inertial confinement fusion, optimizing power conditioning system of 4×2 layer amplifier. With preionization the flash-lamp current waveform becomes favorable for improving the amplifier efficiency.
2001,
13.
Abstract:
When diagnostic holes of hohlraum are heated by its radiation, the plasmas produced will reduce the mount of radiation reaching detectors,from which hohlraum’s temperature is determined. A model has been established to study the transmissivity of diagnostic holes on hohlraum heated by Shengguang-II lasers. It is found that the region with r >0.2 gcm-3 plays a major role in radiation shield. The transmissivity we gave under that condition is 0.72.
When diagnostic holes of hohlraum are heated by its radiation, the plasmas produced will reduce the mount of radiation reaching detectors,from which hohlraum’s temperature is determined. A model has been established to study the transmissivity of diagnostic holes on hohlraum heated by Shengguang-II lasers. It is found that the region with r >0.2 gcm-3 plays a major role in radiation shield. The transmissivity we gave under that condition is 0.72.
2001,
13.
Abstract:
The hybrid algorithm, combing Hill-climbing and Simulated Annealing, and hollowed-out mask are adopted to design and fabricate the diffractive optical element (DOE) with diameter 80mm, to realize beam smoothing for the fundamental wave and the third harmonic wave of Nd:YAG laser. The edge of the DOE is measured by the profilometer, which shows a rather large etching depth error exists. The performance of the DOE is experimentally studied with a pulse-operating Nd:YAG laser. Focused spots have been obtained with the corresponding design size and sharp edge, while a large top modulation exists too. The feasibility of the DOE used in the solid laser beam smoothing is preliminary proved by these firstly obtained experimental results.
The hybrid algorithm, combing Hill-climbing and Simulated Annealing, and hollowed-out mask are adopted to design and fabricate the diffractive optical element (DOE) with diameter 80mm, to realize beam smoothing for the fundamental wave and the third harmonic wave of Nd:YAG laser. The edge of the DOE is measured by the profilometer, which shows a rather large etching depth error exists. The performance of the DOE is experimentally studied with a pulse-operating Nd:YAG laser. Focused spots have been obtained with the corresponding design size and sharp edge, while a large top modulation exists too. The feasibility of the DOE used in the solid laser beam smoothing is preliminary proved by these firstly obtained experimental results.
2001,
13.
Abstract:
The X-ray spectra emitted from laser-produced Au plasmas in the range 0.3-0.4nm were analyzied and interpreted by using the Spin-Orbit-Splitted Array model. The plasmas were created by using a beam of a frequency-tripled 1.05m m Nd-glass laser focused onto a microdot target of gold.The pulse width was 800ps and the laser energy was about 12J. The emitted X-ray was analyzed by a pentaerythritol(PET) crystal spectrograph and recorded on Tianjing New-III X-ray films. On the assumption of the mono-temperatured local-thermodynamical-equilibrium approximation, the electronic temperature was obtained from the intensity ratio of two unresolved transition arrays, and the experimental spectra were simulated.
The X-ray spectra emitted from laser-produced Au plasmas in the range 0.3-0.4nm were analyzied and interpreted by using the Spin-Orbit-Splitted Array model. The plasmas were created by using a beam of a frequency-tripled 1.05m m Nd-glass laser focused onto a microdot target of gold.The pulse width was 800ps and the laser energy was about 12J. The emitted X-ray was analyzed by a pentaerythritol(PET) crystal spectrograph and recorded on Tianjing New-III X-ray films. On the assumption of the mono-temperatured local-thermodynamical-equilibrium approximation, the electronic temperature was obtained from the intensity ratio of two unresolved transition arrays, and the experimental spectra were simulated.
2001,
13.
Abstract:
The characteristics of front-end light, a key problem in EFISI(Echelon-Free Induced Spatial Incoherence), is analyzed in this paper, and a new type partially coherence light source is researched here. According to electrooptical properties of nematic liquid crystal, two type liquid crystal are used as scattering materials to carry out the experimental study of partially coherence light source designed for EFISI. The relationship between applied voltage and energy transmittivity, uniformity, coherence of scattering light is obtained. Results show that both intensities and uniformity of scattering light can be improved, at the same time coherence can be decreased through changing the applied electrical field. So the partially coherence light source can be approached
The characteristics of front-end light, a key problem in EFISI(Echelon-Free Induced Spatial Incoherence), is analyzed in this paper, and a new type partially coherence light source is researched here. According to electrooptical properties of nematic liquid crystal, two type liquid crystal are used as scattering materials to carry out the experimental study of partially coherence light source designed for EFISI. The relationship between applied voltage and energy transmittivity, uniformity, coherence of scattering light is obtained. Results show that both intensities and uniformity of scattering light can be improved, at the same time coherence can be decreased through changing the applied electrical field. So the partially coherence light source can be approached
