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RSS1997 Vol. 09, No. 01
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1997,
09.
Abstract:
A method for measuring laser ablation depth with time-integrated crystal spectrometer is introduced in the paper. Ablation depth, mass ablation rate and ablation pressure for aluminium and C8H8 material driven by laser are obtained from experimental data. Finally the experimental results are analyzed and discussed.
A method for measuring laser ablation depth with time-integrated crystal spectrometer is introduced in the paper. Ablation depth, mass ablation rate and ablation pressure for aluminium and C8H8 material driven by laser are obtained from experimental data. Finally the experimental results are analyzed and discussed.
1997,
09.
Abstract:
A dynamic spot diagnostic system has been developed to quantitatively measure the instability of a Continuous-Wave Chemical Oxygen Iodine Laser(CW-COIL). The system can measure the real time changes in drift, vibration of low frequency, intensity profile and spot diameter for the CW-COIL laser beam. The cause that induces the instability of laser beam was tentatively analyzed in this paper. The experimental results provided a basis for improving the COIL laser and for studying the laser-material interactions.
A dynamic spot diagnostic system has been developed to quantitatively measure the instability of a Continuous-Wave Chemical Oxygen Iodine Laser(CW-COIL). The system can measure the real time changes in drift, vibration of low frequency, intensity profile and spot diameter for the CW-COIL laser beam. The cause that induces the instability of laser beam was tentatively analyzed in this paper. The experimental results provided a basis for improving the COIL laser and for studying the laser-material interactions.
1997,
09.
Abstract:
Resonant absorption of a P-polarized laser light which obliquely incidents on an inhomogeneous plasma slab with a linear density profile, is simulated by a 2-D multitime-scale electromagnetic relativistic particle simulation code. Structure of self-consistent field and density profile of plasma in the corona are presented. Excitation of plasma wave, steepening of density profile and the production of cavitations are observed by numerical simulation.
Resonant absorption of a P-polarized laser light which obliquely incidents on an inhomogeneous plasma slab with a linear density profile, is simulated by a 2-D multitime-scale electromagnetic relativistic particle simulation code. Structure of self-consistent field and density profile of plasma in the corona are presented. Excitation of plasma wave, steepening of density profile and the production of cavitations are observed by numerical simulation.
1997,
09.
Abstract:
An 1-D pulse FEL simulation code is applied to study the accelerator noise effects on CIAE far-infrared FEL oscillator. The laser power instability and spectral center shift due to the time jitter and energy ripple of the electron micropulse are modeled by the code, and the roles of the noise frequency, amplitude as well as the optical cavity detuning in the noise effects on the FEL are exhibited in the simulation.
An 1-D pulse FEL simulation code is applied to study the accelerator noise effects on CIAE far-infrared FEL oscillator. The laser power instability and spectral center shift due to the time jitter and energy ripple of the electron micropulse are modeled by the code, and the roles of the noise frequency, amplitude as well as the optical cavity detuning in the noise effects on the FEL are exhibited in the simulation.
1997,
09.
Abstract:
Based on fast Fourial transform (FFT), a method of the equivalent spatial frequency transmission has been proposed and applied to calculate resonator modes of the axis-asymmetric positive confocal resonators with a one-dimensional variable reflectivity mirror (1D VRM) used for slab lasers, which have been then compared with the results of the axis- asymmetric positive confocal resonator with a uniform reflectivity mirror (URM), and with a two-dimensional rotationally-symmetrical variable reflectivity mirror (2D VRM), respectively. In our calculations the resonator axis-asymmetry and gain saturation characteristics of the active medium have been considered. Numerical calculation results have demonstrated that the 1D VRM axis-asymmetric positive confocal resonator has the advantage of provid
Based on fast Fourial transform (FFT), a method of the equivalent spatial frequency transmission has been proposed and applied to calculate resonator modes of the axis-asymmetric positive confocal resonators with a one-dimensional variable reflectivity mirror (1D VRM) used for slab lasers, which have been then compared with the results of the axis- asymmetric positive confocal resonator with a uniform reflectivity mirror (URM), and with a two-dimensional rotationally-symmetrical variable reflectivity mirror (2D VRM), respectively. In our calculations the resonator axis-asymmetry and gain saturation characteristics of the active medium have been considered. Numerical calculation results have demonstrated that the 1D VRM axis-asymmetric positive confocal resonator has the advantage of provid
1997,
09.
Abstract:
Electro-optical switch with plasma electrodes is one of critical components in high power ICF drivers based on the large aperture multipass amplifier array scheme. To investigate problems related to this technology an 80mm 80mm Pockels cell using a plasma electrode formed by a glow discharge on either side of a KDP crystal was designed and constructed and the switching performance was tested. This letter describes the configuration of the Pockels cell, the plasma electrode formation by glow discharge, the switch pulse generation and output performance, as well as the measurement of the switching speed and the switching efficiency across the aperture. Some typical results in the switching experiment are given.
Electro-optical switch with plasma electrodes is one of critical components in high power ICF drivers based on the large aperture multipass amplifier array scheme. To investigate problems related to this technology an 80mm 80mm Pockels cell using a plasma electrode formed by a glow discharge on either side of a KDP crystal was designed and constructed and the switching performance was tested. This letter describes the configuration of the Pockels cell, the plasma electrode formation by glow discharge, the switch pulse generation and output performance, as well as the measurement of the switching speed and the switching efficiency across the aperture. Some typical results in the switching experiment are given.
1997,
09.
Abstract:
An experiment setup of far field divergence angle time-resolved measurement for the high power lasers are described in this paper. The far field divergence angle of kW level CW oxygen iodine laser are measured. Finally the experiment results and analyses are presented.
An experiment setup of far field divergence angle time-resolved measurement for the high power lasers are described in this paper. The far field divergence angle of kW level CW oxygen iodine laser are measured. Finally the experiment results and analyses are presented.
1997,
09.
Abstract:
In the frame of channel theory, we have solved the rate equations for populations of all ions and level populations of all excited states, which can provide realistic atomic simulations. As an example, we have studied the recombination X-ray laser for hydrogen-like lithium and discussed the possibility of lasing with respect to the ground state.
In the frame of channel theory, we have solved the rate equations for populations of all ions and level populations of all excited states, which can provide realistic atomic simulations. As an example, we have studied the recombination X-ray laser for hydrogen-like lithium and discussed the possibility of lasing with respect to the ground state.
1997,
09.
Abstract:
On the basis of research of the mass, heat transfer process and the chemical dynamics in Singlet Oxygen Generator(SOG), a rotating disk type SOG was developed and used for a high power supersonic Chemical Oxygen-Iodine Laser (COIL). The results show that the partial pressure of O2(1D ) can reach to 333.3~519.9Pa, the concentration of O2(1D ) is up to 50%~68%, chlorine utilization is greater than 90% and the content of H2O in gas flow is less than 10%.
On the basis of research of the mass, heat transfer process and the chemical dynamics in Singlet Oxygen Generator(SOG), a rotating disk type SOG was developed and used for a high power supersonic Chemical Oxygen-Iodine Laser (COIL). The results show that the partial pressure of O2(1D ) can reach to 333.3~519.9Pa, the concentration of O2(1D ) is up to 50%~68%, chlorine utilization is greater than 90% and the content of H2O in gas flow is less than 10%.
1997,
09.
Abstract:
The inversion and gain of the electron-collisional excitation pumping X-ray laser depend on four parameters (electron density Ne, electron temperature Te, width of gain region D R and velocity gradient of lasing medium dv/dz) describing the internal state of plasmas. As an example, the dependence of the inversion and gain of laser lines at 19.6nm, 23.2nm and 23.6nm in neon-like germanium ion on Ne and Te is studied in this paper. In the gain region with a typical spatial width (D R=100m m）and velocity gradient of lasing medium (dv/dz=1.3 109s-1）,the effect of resonance lines-trapping on the gain is discussed and the objective regions of gain are given for these laser lines. In addition, the effect of dielectronic recombination process on charge-state distribution is discussed.
The inversion and gain of the electron-collisional excitation pumping X-ray laser depend on four parameters (electron density Ne, electron temperature Te, width of gain region D R and velocity gradient of lasing medium dv/dz) describing the internal state of plasmas. As an example, the dependence of the inversion and gain of laser lines at 19.6nm, 23.2nm and 23.6nm in neon-like germanium ion on Ne and Te is studied in this paper. In the gain region with a typical spatial width (D R=100m m）and velocity gradient of lasing medium (dv/dz=1.3 109s-1）,the effect of resonance lines-trapping on the gain is discussed and the objective regions of gain are given for these laser lines. In addition, the effect of dielectronic recombination process on charge-state distribution is discussed.
1997,
09.
Abstract:
The dependence of the reflectivity in Stimulated Brillouin Scattering (SBS)on the fluctuations of the pumping intensity was analysized theoretically. The reflectivity stability was close to the pumping stability while the pumping intensity was 1.9 times of SBS threshold. The reflectivity fluctuations were 2.4% less than the pumping fluctuations while the pumping intensity was 5 times greater than SBS threshold.
The dependence of the reflectivity in Stimulated Brillouin Scattering (SBS)on the fluctuations of the pumping intensity was analysized theoretically. The reflectivity stability was close to the pumping stability while the pumping intensity was 1.9 times of SBS threshold. The reflectivity fluctuations were 2.4% less than the pumping fluctuations while the pumping intensity was 5 times greater than SBS threshold.
1997,
09.
Abstract:
This paper describes the performance of a novel system. The system is mainly composed of a magnetic scanning system, a slit, a fluorescent screen and a CCD camera. The system is able to measure the actual phase diagram of a relativistic electron beam (4~10MeV).
This paper describes the performance of a novel system. The system is mainly composed of a magnetic scanning system, a slit, a fluorescent screen and a CCD camera. The system is able to measure the actual phase diagram of a relativistic electron beam (4~10MeV).
1997,
09.
Abstract:
In this paper, the effects of the optical klystron on the beam (such as emmittance, energy spread, damping, closed orbit, the vertical tune, and the distortions of the vertical focus) are discussed. We present a compensated method of the distortion of Twiss parameters.
In this paper, the effects of the optical klystron on the beam (such as emmittance, energy spread, damping, closed orbit, the vertical tune, and the distortions of the vertical focus) are discussed. We present a compensated method of the distortion of Twiss parameters.
1997,
09.
Abstract:
Neodumium-dopted LNA crystal promises to be used in ultrashort laser pulse because of it having wide spectrum bandwidth, high gain, high dopted concentration, and wide absorption bandwidth for multiful pump source type. The new-mode lasing material was applied to negative feedback controlled mode locking technique on the facility. As a result, 5ps laser pulse near transform-limit was obtained.
Neodumium-dopted LNA crystal promises to be used in ultrashort laser pulse because of it having wide spectrum bandwidth, high gain, high dopted concentration, and wide absorption bandwidth for multiful pump source type. The new-mode lasing material was applied to negative feedback controlled mode locking technique on the facility. As a result, 5ps laser pulse near transform-limit was obtained.
1997,
09.
Abstract:
By use of the self-consistent linear field theory, 3D perturbation of electrons affected by the perturbed electromagnetic fields is generally discussed. And Cherenkov radiations excited by a thin annular relativistic electron beam and a solid relativistic electron beam in a plasma-filled, dielectric lined slow-wave waveguide are analysed in detail, respectively. The dispersion equations of the beam-wave interaction are derived. It抯 clearly shown that the beam-wave interaction results from the coupling of the TM mode in the plasma-filled, dielectric lined slow-wave waveguide to the beam mode via the electron beam. Finally, the growth rates of wave are obtained, and the effect of plasma density and the electron beam radius on the growth rate of the wave is calculated and discussed.
By use of the self-consistent linear field theory, 3D perturbation of electrons affected by the perturbed electromagnetic fields is generally discussed. And Cherenkov radiations excited by a thin annular relativistic electron beam and a solid relativistic electron beam in a plasma-filled, dielectric lined slow-wave waveguide are analysed in detail, respectively. The dispersion equations of the beam-wave interaction are derived. It抯 clearly shown that the beam-wave interaction results from the coupling of the TM mode in the plasma-filled, dielectric lined slow-wave waveguide to the beam mode via the electron beam. Finally, the growth rates of wave are obtained, and the effect of plasma density and the electron beam radius on the growth rate of the wave is calculated and discussed.
1997,
09.
Abstract:
The calculation of the intensity second moment of the uniform plane wave far field diffraction spot have discussed and numerical the variation of the second moment with the different cut percentage of high spatial frequency component has given simulation of calculation. It was difficult to judge the beam quality of the uniform plane wave by the way of M2 factor in principle, but how much high spatial frequency to cut off is prescribed, the process may be executed. This cut of high spatial frequency component will occur in measurement of beam spatial parameters.
The calculation of the intensity second moment of the uniform plane wave far field diffraction spot have discussed and numerical the variation of the second moment with the different cut percentage of high spatial frequency component has given simulation of calculation. It was difficult to judge the beam quality of the uniform plane wave by the way of M2 factor in principle, but how much high spatial frequency to cut off is prescribed, the process may be executed. This cut of high spatial frequency component will occur in measurement of beam spatial parameters.
1997,
09.
Abstract:
This paper analyzes how to obtain higher harmonic component of magnetic field of the Wiggler, proposes a new type of the modified wiggler梩he U form modified Wiggler, optimizes the parameters of the modified Wiggler, discusses the trajectory of the electron and the spontaneous emission spectrum of the modified Wiggler. To prove the theory, a model including six periods had been made, and the distribution of the field of the model had been measured. The result of measuring verifies the theory on the whole.
This paper analyzes how to obtain higher harmonic component of magnetic field of the Wiggler, proposes a new type of the modified wiggler梩he U form modified Wiggler, optimizes the parameters of the modified Wiggler, discusses the trajectory of the electron and the spontaneous emission spectrum of the modified Wiggler. To prove the theory, a model including six periods had been made, and the distribution of the field of the model had been measured. The result of measuring verifies the theory on the whole.
1997,
09.
Abstract:
X-ray laser target is of great importance to X 杛ay laser experiments. In this article, various kinds of X-ray laser targets are prepared in accordence with the different requirments of X-ray laser experiments. Measurements are emplored to provide the accurate parameters of the targets.
X-ray laser target is of great importance to X 杛ay laser experiments. In this article, various kinds of X-ray laser targets are prepared in accordence with the different requirments of X-ray laser experiments. Measurements are emplored to provide the accurate parameters of the targets.
1997,
09.
Abstract:
In the experimental study of X-ray laser with Ge plasma as the gain medium, cylindrical plasma can be obtained with transverse width very narrow when Cu target inlaid with Ge was used, thus it will contribute to achieve the single mode output of x-ray laser. Experiment studies of Cu targets inlaid with Ge is presented in this paper.
In the experimental study of X-ray laser with Ge plasma as the gain medium, cylindrical plasma can be obtained with transverse width very narrow when Cu target inlaid with Ge was used, thus it will contribute to achieve the single mode output of x-ray laser. Experiment studies of Cu targets inlaid with Ge is presented in this paper.
1997,
09.
Abstract:
The distribution function of the particles is gained with the statistical mechanics method for intense beam. The theory unites the existing potential well distortion theory and the microwave instability to explain the bunch lengthening. It is more important that the theory proves the bunch lengthening is a multi-bunch effect in nature. So the importance of the narrow-band impedance to the bunch lengthening is pointed out.
The distribution function of the particles is gained with the statistical mechanics method for intense beam. The theory unites the existing potential well distortion theory and the microwave instability to explain the bunch lengthening. It is more important that the theory proves the bunch lengthening is a multi-bunch effect in nature. So the importance of the narrow-band impedance to the bunch lengthening is pointed out.
1997,
09.
Abstract:
Aerosol-induced laser breakdown thresholds has been discussed in different optic parameter or in different micro-meter sized particles using a mode-locked Nd:YAG laser with 123.61ps pulse duration irradiates aerosol particles (Al2O3、ZnO、ZrO2、18th glass) that are suspended in air. Following results are obtained:breakdown thresholds for aerosol particles (d >30m m) are 2~3 order of magnitude below those for clean air (d >1m m). Air breakdown threshold is lower as laser radius increasing or aerosol particle size increasing. The threshold depends on particles composition The threshold is higher as laser wavelength decreasing.
Aerosol-induced laser breakdown thresholds has been discussed in different optic parameter or in different micro-meter sized particles using a mode-locked Nd:YAG laser with 123.61ps pulse duration irradiates aerosol particles (Al2O3、ZnO、ZrO2、18th glass) that are suspended in air. Following results are obtained:breakdown thresholds for aerosol particles (d >30m m) are 2~3 order of magnitude below those for clean air (d >1m m). Air breakdown threshold is lower as laser radius increasing or aerosol particle size increasing. The threshold depends on particles composition The threshold is higher as laser wavelength decreasing.
1997,
09.
Abstract:
The influence of laser entrance holes?LEHs) radius on the capsule irradiation non-uniformity in cylindrical hohlraum has been studied. It is found that the influence of LEHs at on 2 order irradiation non-uniformity can be described by a family of curves that originate from a fixed point determined by position of laser spots but had nothing to do with LEHs, and that the radius of LEHs influence the grade of non-uniformity curve. The larger the radius is, the larger the grade of non-uniformity curve is. A semirandom simulation method was used to calculate the influence of LEHs on the capsule irradiation non-uniformity when other geometrical factors are given. Fitted the results, a linear relation between irradiation non-uniformity and radius of LEHs was found.
The influence of laser entrance holes?LEHs) radius on the capsule irradiation non-uniformity in cylindrical hohlraum has been studied. It is found that the influence of LEHs at on 2 order irradiation non-uniformity can be described by a family of curves that originate from a fixed point determined by position of laser spots but had nothing to do with LEHs, and that the radius of LEHs influence the grade of non-uniformity curve. The larger the radius is, the larger the grade of non-uniformity curve is. A semirandom simulation method was used to calculate the influence of LEHs on the capsule irradiation non-uniformity when other geometrical factors are given. Fitted the results, a linear relation between irradiation non-uniformity and radius of LEHs was found.
1997,
09.
Abstract:
A novel technique of Phase-Disturbed Plate(PDP) has been developed to suppress interference speckles in array line focus systems. The detailed theoretical analysis and numerical calculation results have been given. Finally, its engineering feasibility has been discussed.
A novel technique of Phase-Disturbed Plate(PDP) has been developed to suppress interference speckles in array line focus systems. The detailed theoretical analysis and numerical calculation results have been given. Finally, its engineering feasibility has been discussed.
1997,
09.
Abstract:
The measurement of the beam quality in a high energy chemical oxygen-iodine laser in kilowatts level with UR-90 cavity are completed. The results show that using UR-90 cavity is an efficient method for improving beam quality.
The measurement of the beam quality in a high energy chemical oxygen-iodine laser in kilowatts level with UR-90 cavity are completed. The results show that using UR-90 cavity is an efficient method for improving beam quality.
1997,
09.
Abstract:
A 3-D simulation code are developed for the x,y double-direction focusing electromagnet wiggler by integration equation method, and some simulated results for a high gain electromagnet wiggler is shown.
A 3-D simulation code are developed for the x,y double-direction focusing electromagnet wiggler by integration equation method, and some simulated results for a high gain electromagnet wiggler is shown.
1997,
09.
Abstract:
Based on the rear X-ray emitted from gold foil irradiated by intense laser beam. The novel targets and experimental method for soft-X-ray-driven ablation were studied. The primary ablation experiments for C8H8 sample were also performed.
Based on the rear X-ray emitted from gold foil irradiated by intense laser beam. The novel targets and experimental method for soft-X-ray-driven ablation were studied. The primary ablation experiments for C8H8 sample were also performed.
1997,
09.
Abstract:
A new kind of long slit soft x-ray streak camera is presented in this paper. The camera has a large working area of 0.1mm 30mm. Time distortion of the camera is minimized by improving the design of the electro-optical system of soft x-ray streak tube. The dynamic test shows that the camera has a temporal resolution of 5ps and a spatial resolution of 15Lp/mm along the slit length of 30mm at the fastest sweep speed of 2.5cm/ns. A new time distortion correction theory and its application is also presented.
A new kind of long slit soft x-ray streak camera is presented in this paper. The camera has a large working area of 0.1mm 30mm. Time distortion of the camera is minimized by improving the design of the electro-optical system of soft x-ray streak tube. The dynamic test shows that the camera has a temporal resolution of 5ps and a spatial resolution of 15Lp/mm along the slit length of 30mm at the fastest sweep speed of 2.5cm/ns. A new time distortion correction theory and its application is also presented.
1997,
09.
Abstract:
The physics, chemistry and spectral characteristics of Ti:sapphire crystal are described in details. The introduction to various Ti: sapphire laser and key techniques are in particular given. In addition, a brief overview on the international and domestic history, development and application of Ti: sapphire laser ,especially the state-of-the-art ultrashort pulse laser amplification techniques and systems are presented.
The physics, chemistry and spectral characteristics of Ti:sapphire crystal are described in details. The introduction to various Ti: sapphire laser and key techniques are in particular given. In addition, a brief overview on the international and domestic history, development and application of Ti: sapphire laser ,especially the state-of-the-art ultrashort pulse laser amplification techniques and systems are presented.
