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RSS2000 Vol. 12, No. 08
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2000,
12.
Abstract:
It has the advantages of largely decrease the discharging parameters of PEPC through magnetron cathode. The results of experiments which in different size of cathode, different strength of magnetic and different gas pressure indicate that the uniform discharge can be got in a large range of magnetic strength. The small change of the sizes of cathode hardly effects the parameters and uniformity of discharge. The best parameters of glow discharge for 300mm×300mm discharging chamber is given out.
It has the advantages of largely decrease the discharging parameters of PEPC through magnetron cathode. The results of experiments which in different size of cathode, different strength of magnetic and different gas pressure indicate that the uniform discharge can be got in a large range of magnetic strength. The small change of the sizes of cathode hardly effects the parameters and uniformity of discharge. The best parameters of glow discharge for 300mm×300mm discharging chamber is given out.
2000,
12.
Abstract:
A system for measuring optical performance of plasma electrode Pockels cell (PEPC) electron-optical switches is constructed, which provide with time and space resolution capabilities. The optical layout used to diagnose performance of the 240mm×240mm PEPC are described. And the results of experiment are given．
A system for measuring optical performance of plasma electrode Pockels cell (PEPC) electron-optical switches is constructed, which provide with time and space resolution capabilities. The optical layout used to diagnose performance of the 240mm×240mm PEPC are described. And the results of experiment are given．
2000,
12.
Abstract:
Based on the requirement of the ICF drive system project, beam position stability budget is preliminarily evaluated by the motion of optical components being related to beam position on target. To adjust as to meet stability requirement, the type B standard uncertainty, ray-tracing, finite element analyses are applied. Simultaneously based on the structure random vibration theory, the optical support structures will be represented as a single degree of freedom system with a structural mode, the stability allocations for the different sources of input or excitation can be derived.
Based on the requirement of the ICF drive system project, beam position stability budget is preliminarily evaluated by the motion of optical components being related to beam position on target. To adjust as to meet stability requirement, the type B standard uncertainty, ray-tracing, finite element analyses are applied. Simultaneously based on the structure random vibration theory, the optical support structures will be represented as a single degree of freedom system with a structural mode, the stability allocations for the different sources of input or excitation can be derived.
2000,
12.
Abstract:
Based on the Belpalov-Talanov theory, considering the vacuum propagation of light, the power growth of small scale ripple for slab amplifiers is calculated. The factors which effect on the value and spatial maximum spatial frequencies of the power growth are analyzed.
Based on the Belpalov-Talanov theory, considering the vacuum propagation of light, the power growth of small scale ripple for slab amplifiers is calculated. The factors which effect on the value and spatial maximum spatial frequencies of the power growth are analyzed.
2000,
12.
Abstract:
Self-focusing rings of circle symmetric super-Gaussian laser beam (CSSGLB) with high intensity travelling in Nd:glass medium, are described in detail with numerically solution to the nonlinear Schdinger equation. When a CSSGLB with initial perturbations travelling in this medium, the self-focusing rings are to be broken up and form high intense filaments. This phenomenon showed the instability of the self-focusing rings .The high intensity filaments may destroy the medium．
Self-focusing rings of circle symmetric super-Gaussian laser beam (CSSGLB) with high intensity travelling in Nd:glass medium, are described in detail with numerically solution to the nonlinear Schdinger equation. When a CSSGLB with initial perturbations travelling in this medium, the self-focusing rings are to be broken up and form high intense filaments. This phenomenon showed the instability of the self-focusing rings .The high intensity filaments may destroy the medium．
2000,
12.
Abstract:
Nowadays almost all advanced computer languages can give false random numbers. Two methods were developed to produce normal school random numbers, and the produced numbers were used in a beam transmission simulating software to analyze the stability of the layout of a large laser facility. The software has been successfully used to analyze the stability of the layout of the four-pass amplifying system of the prototype of Shenguang Ⅲ.
Nowadays almost all advanced computer languages can give false random numbers. Two methods were developed to produce normal school random numbers, and the produced numbers were used in a beam transmission simulating software to analyze the stability of the layout of a large laser facility. The software has been successfully used to analyze the stability of the layout of the four-pass amplifying system of the prototype of Shenguang Ⅲ.
2000,
12.
Abstract:
For the characterization of ICF plasmas, A 2ω probe laser at the xingguang-Ⅱ laser facility was implemented. A total energy of >5J,a focal spot size of order 100μm was demonstrated for target shots. It fulfills high-power requirements for laser-plasma interaction experiments. The 2ω probe laser is now routinely used for laser-plasma diagnostics experiment．
For the characterization of ICF plasmas, A 2ω probe laser at the xingguang-Ⅱ laser facility was implemented. A total energy of >5J,a focal spot size of order 100μm was demonstrated for target shots. It fulfills high-power requirements for laser-plasma interaction experiments. The 2ω probe laser is now routinely used for laser-plasma diagnostics experiment．
2000,
12.
Abstract:
The high power pulse laser energy spread is researched by statistic method, the energy spread is described in this paper. Supposing the output energy spread be known, the relation between the average energy and the probability of that which output energy is bigger than a given value is also described. Supposing the injected energy and parameters of optical elements obey normal distribution, basing on the multi-pass amplifier system where the main amplifier has 9 slabs and the booster has 5 slabs, the output energy spread about 1ns exponential injected pulse is simulated．
The high power pulse laser energy spread is researched by statistic method, the energy spread is described in this paper. Supposing the output energy spread be known, the relation between the average energy and the probability of that which output energy is bigger than a given value is also described. Supposing the injected energy and parameters of optical elements obey normal distribution, basing on the multi-pass amplifier system where the main amplifier has 9 slabs and the booster has 5 slabs, the output energy spread about 1ns exponential injected pulse is simulated．
2000,
12.
Abstract:
The characteristics of a super-Gaussian beam propagating in the amplifier of stacked-slabs have been simulated after resolving the nonlinear Schrdinger equation with the split step Fourier numerical method. The fact which influence the laser propagating in the amplifier of stacked-slabs have been studied, including the waist parameter and order number of super-Gaussian beam and the free space of laser propagation. The light intensities dependent evolutions of a super-Gaussian beam propagating in the amplifier of stacked-slabs have been also analyzed ．
The characteristics of a super-Gaussian beam propagating in the amplifier of stacked-slabs have been simulated after resolving the nonlinear Schrdinger equation with the split step Fourier numerical method. The fact which influence the laser propagating in the amplifier of stacked-slabs have been studied, including the waist parameter and order number of super-Gaussian beam and the free space of laser propagation. The light intensities dependent evolutions of a super-Gaussian beam propagating in the amplifier of stacked-slabs have been also analyzed ．
2000,
12.
Abstract:
Through analysis of the self-excitation oscillation, methods were found to restraint the self-excitation oscilation in the two-pass amplification by experiment on the two-pass amplification of high power solid-state laser facility without a insulator. The methods can also be used to resolve the problems of self-excitation oscillation on the four-pass amplification.
Through analysis of the self-excitation oscillation, methods were found to restraint the self-excitation oscilation in the two-pass amplification by experiment on the two-pass amplification of high power solid-state laser facility without a insulator. The methods can also be used to resolve the problems of self-excitation oscillation on the four-pass amplification.
2000,
12.
Abstract:
Thermal recovery of the 4×2×3 multi-segment amplifiers that will be used for SGIII laser facility was presented. A lumped mass model was used to investigate the thermal recovery processes of the flash lamps, blast shield, and laser slab. A 3-D finite element model was used to investigate in detail the time related spatial temperature distribution of the laser slab. The preliminary calculating results indicate that, with an optimization thermal recovery, we can reduce the thermal gradient and the average temperature of the slab to an acceptable value．
Thermal recovery of the 4×2×3 multi-segment amplifiers that will be used for SGIII laser facility was presented. A lumped mass model was used to investigate the thermal recovery processes of the flash lamps, blast shield, and laser slab. A 3-D finite element model was used to investigate in detail the time related spatial temperature distribution of the laser slab. The preliminary calculating results indicate that, with an optimization thermal recovery, we can reduce the thermal gradient and the average temperature of the slab to an acceptable value．
2000,
12.
Abstract:
The basic definitions and optimization method for design of high power solidstate lasers for Inertial Confinement Fusion (ICF) drivers were clarified. The preliminary optimized design for a fourpass amplification system was given based on the conducted criterion of the figure of merits (FOM) and restrictions.
The basic definitions and optimization method for design of high power solidstate lasers for Inertial Confinement Fusion (ICF) drivers were clarified. The preliminary optimized design for a fourpass amplification system was given based on the conducted criterion of the figure of merits (FOM) and restrictions.
2000,
12.
Abstract:
Based on the Frantz-Nodvik formula, the saturation fluency of a Nd3+ doped phosphate glass under short pulse was obtained, through measuring the small signal gain, input fluency and output fluency of the amplifier whose gain material was made from the glass to be measured. By analyzing of the measured data, the experiential formula of saturation fluency verse output fluency was also obtained.
Based on the Frantz-Nodvik formula, the saturation fluency of a Nd3+ doped phosphate glass under short pulse was obtained, through measuring the small signal gain, input fluency and output fluency of the amplifier whose gain material was made from the glass to be measured. By analyzing of the measured data, the experiential formula of saturation fluency verse output fluency was also obtained.
2000,
12.
Abstract:
The property of the PSD (Power Spectral Density) distribution of the laser wavefront producing the focal spot with the wings is analyzed, whether the KPP, for controlling the shape and the intensity distribution of the focal spot, is put in or not. Based on the requirement of the focusing spot without the wings in the high power laser driver, the control demands of the aberrant wavefront of the incident laser beam is obtained．
The property of the PSD (Power Spectral Density) distribution of the laser wavefront producing the focal spot with the wings is analyzed, whether the KPP, for controlling the shape and the intensity distribution of the focal spot, is put in or not. Based on the requirement of the focusing spot without the wings in the high power laser driver, the control demands of the aberrant wavefront of the incident laser beam is obtained．
2000,
12.
Abstract:
A 40J laser system, which is called Beamlet", is built at XingguangⅡlaser facility. The system's source is split from XingguangⅡlaser facility and includes an amplifier chain, an energy supply system and a support shelves. The results of analog calculation for the whole system indicates that the gain is large enough for the design of 40J and ΔB less than 1.8. A new type of whole cavity water cooling amplifier is applied in this system. The experiments of small signal gain factor and gain homogenization on such amplifier show that the gain factor βis 0.034cm-1and gain homogenization is 91.84%.The result indicates the new type amplifier is fit for the design requirement of the laser system．
A 40J laser system, which is called Beamlet", is built at XingguangⅡlaser facility. The system's source is split from XingguangⅡlaser facility and includes an amplifier chain, an energy supply system and a support shelves. The results of analog calculation for the whole system indicates that the gain is large enough for the design of 40J and ΔB less than 1.8. A new type of whole cavity water cooling amplifier is applied in this system. The experiments of small signal gain factor and gain homogenization on such amplifier show that the gain factor βis 0.034cm-1and gain homogenization is 91.84%.The result indicates the new type amplifier is fit for the design requirement of the laser system．
2000,
12.
Abstract:
Based on analyzing the features of low frequency phase noise of laser beam, RMS of phase gradient was introduced to characterize it and the corresponding wavefront model was constructed by using random phase screen. The primary relationship between the size of the focal spot and RMS of phase gradient was also given by simulation calculation.
Based on analyzing the features of low frequency phase noise of laser beam, RMS of phase gradient was introduced to characterize it and the corresponding wavefront model was constructed by using random phase screen. The primary relationship between the size of the focal spot and RMS of phase gradient was also given by simulation calculation.
2000,
12.
Abstract:
A method for etalon design is reported, which is used for the calibration for sweep non-linearity of streak camera and the test of its dynamic range. with appropriate etalon, and the method of intensity correction dot by dot, the sweep non-linearity of C1587 streak camera has been calibrated and automatically corrected by computer.
A method for etalon design is reported, which is used for the calibration for sweep non-linearity of streak camera and the test of its dynamic range. with appropriate etalon, and the method of intensity correction dot by dot, the sweep non-linearity of C1587 streak camera has been calibrated and automatically corrected by computer.
2000,
12.
Abstract:
In order to improve the stability reliability safety of power-conditioning system of laser driver, we develop a set of testing and controlling system for experimental bed of the power-conditioning system. The system use RS-232 serial communication designing program for several threads. To finish the abreast process and with the high capability of anti-jamming. It can control the platform automatically perform data and processing analyzing data. The report was seemed on screen, can also print it. The laser facility may refer to the result of the system.
In order to improve the stability reliability safety of power-conditioning system of laser driver, we develop a set of testing and controlling system for experimental bed of the power-conditioning system. The system use RS-232 serial communication designing program for several threads. To finish the abreast process and with the high capability of anti-jamming. It can control the platform automatically perform data and processing analyzing data. The report was seemed on screen, can also print it. The laser facility may refer to the result of the system.
2000,
12.
Abstract:
With many advantages, scientific grade CCD camera has been applied to diagnose the quality of laser beam in the field of highpower solid laser. Linear dynamic range is one of the most important characteristics. A new method calibrating the dynamic range for CAS-512A CCD system with optical wedge is reported.
With many advantages, scientific grade CCD camera has been applied to diagnose the quality of laser beam in the field of highpower solid laser. Linear dynamic range is one of the most important characteristics. A new method calibrating the dynamic range for CAS-512A CCD system with optical wedge is reported.
2000,
12.
Abstract:
The purpose of this experiment is to describe that high-power large-aperture, square beam off-axis two-pass amplifier in multi-pass laser amplifier facility have been realized, and the gain coefficient of the laser amplifier have been tested. Under the condition of charge voltage 22kV and pump-energy density 10.24J/cm3, obtain small signal gain coefficient 4.08%cm-1.
The purpose of this experiment is to describe that high-power large-aperture, square beam off-axis two-pass amplifier in multi-pass laser amplifier facility have been realized, and the gain coefficient of the laser amplifier have been tested. Under the condition of charge voltage 22kV and pump-energy density 10.24J/cm3, obtain small signal gain coefficient 4.08%cm-1.
2000,
12.
Abstract:
Due to the requirement of laser conditioning system of ICF drive. A Nd: YAG laser system with high power and high beam quality is developed. Compared to current common laser system, it has an apparent improvement in temporal shape and beam quality. The system applies several technologies and teaches as following: a single longitudinal mode oscillator with a passive Q-switch; SBS pulse compressing technology; SBS pulse phase-conjugation technology; image relay technology and high efficient pumping cavity. Its main technology indexes are listed as pulse width 3ns ，energy 1.1J，far field diverge angle 0.3mrad,repitition frequency 10Hz．
Due to the requirement of laser conditioning system of ICF drive. A Nd: YAG laser system with high power and high beam quality is developed. Compared to current common laser system, it has an apparent improvement in temporal shape and beam quality. The system applies several technologies and teaches as following: a single longitudinal mode oscillator with a passive Q-switch; SBS pulse compressing technology; SBS pulse phase-conjugation technology; image relay technology and high efficient pumping cavity. Its main technology indexes are listed as pulse width 3ns ，energy 1.1J，far field diverge angle 0.3mrad,repitition frequency 10Hz．
2000,
12.
Abstract:
A 240mm×240mm plasma electrode Pockels cell is constructed. Using a planer magnetron cathode a uniform plasma discharge covered the full aperture on either side of the KDP crystal is produced. A rectangular switch pulse with 50ns rise time,500ns pulse width and ≤±2% surge in the top platform is shaped by a pulse forming network. Measurements of the optical performance show that the static transmittance of 85.8%, extinction ratio of 132, switching efficiency of 97.6% and switching rise time of 95ns are obtained.
A 240mm×240mm plasma electrode Pockels cell is constructed. Using a planer magnetron cathode a uniform plasma discharge covered the full aperture on either side of the KDP crystal is produced. A rectangular switch pulse with 50ns rise time,500ns pulse width and ≤±2% surge in the top platform is shaped by a pulse forming network. Measurements of the optical performance show that the static transmittance of 85.8%, extinction ratio of 132, switching efficiency of 97.6% and switching rise time of 95ns are obtained.
2000,
12.
Abstract:
The overall characteristics of high efficiency third harmonic conversion for type Ⅰ/type Ⅱ angledetuning and type Ⅱ/type Ⅱ polarization mismatch schemes (two doubler and two tripler) have been analyzed by numeric simulation with high power large dynamic input fundamental waves. The effects of partial polarization beam on both schemes have also been simulated. The results show that the type Ⅰ/type Ⅱ angeldetuning scheme is better than type Ⅱ/type Ⅱ polarization mismatch scheme under above conditions.
The overall characteristics of high efficiency third harmonic conversion for type Ⅰ/type Ⅱ angledetuning and type Ⅱ/type Ⅱ polarization mismatch schemes (two doubler and two tripler) have been analyzed by numeric simulation with high power large dynamic input fundamental waves. The effects of partial polarization beam on both schemes have also been simulated. The results show that the type Ⅰ/type Ⅱ angeldetuning scheme is better than type Ⅱ/type Ⅱ polarization mismatch scheme under above conditions.
2000,
12.
Abstract:
The non-linear 2ndharmonic conversion effect of the KDP crystal is researched and its effect to measurement accuracy of the laser pulse width. Experimental results show that: in condition of small signal and Gaussian beams, the 1stharmonic laser pulse width is times of that of the 2ndharmonic one with type Ⅱ KDP crystal whose thickness is 1～3cm; Due to the nonGaussian beams, the halfwidth of the 1stharmonic pulse equals to the quarter width of the 2ndharmonic pulse. With higher power density and energy conversion efficiency, the rate between the 1stharmonic pulse width and the 2ndharmonic one vary seriously．
The non-linear 2ndharmonic conversion effect of the KDP crystal is researched and its effect to measurement accuracy of the laser pulse width. Experimental results show that: in condition of small signal and Gaussian beams, the 1stharmonic laser pulse width is times of that of the 2ndharmonic one with type Ⅱ KDP crystal whose thickness is 1～3cm; Due to the nonGaussian beams, the halfwidth of the 1stharmonic pulse equals to the quarter width of the 2ndharmonic pulse. With higher power density and energy conversion efficiency, the rate between the 1stharmonic pulse width and the 2ndharmonic one vary seriously．
2000,
12.
Abstract:
Type Ⅰ/ Type Ⅱ angledetuning tripling frequency scheme of KDP crystal was chose for triple harmonic conversion with large aperture and high power. Based on threewave mixing nonlinear coupling equation, wrote a twodimension program for numerical simulation triple harmonic conversion by introducing discrete Fourier transform and a fourthorder Runge-Kutta integrating method. With the code, conversion features and efficiencies of second and third harmonics were calculated with different thickness of crystal and different angledetuning. Tripling frequency system assuming that the intensity distribution of 1ω is super Gaussian distribution with sixthorder is optimized. The results showed that the system has both broad dynamic range and more high conversion efficiency.
Type Ⅰ/ Type Ⅱ angledetuning tripling frequency scheme of KDP crystal was chose for triple harmonic conversion with large aperture and high power. Based on threewave mixing nonlinear coupling equation, wrote a twodimension program for numerical simulation triple harmonic conversion by introducing discrete Fourier transform and a fourthorder Runge-Kutta integrating method. With the code, conversion features and efficiencies of second and third harmonics were calculated with different thickness of crystal and different angledetuning. Tripling frequency system assuming that the intensity distribution of 1ω is super Gaussian distribution with sixthorder is optimized. The results showed that the system has both broad dynamic range and more high conversion efficiency.
2000,
12.
Abstract:
The isolate of discharge chamber is a key issue of metal material shell PEPC. We have constructed the testing facilities for breakthrough and modulating discharge respectively. Testing samples of anodized film include three kinds of thickness which are 30μm、60μm and 100μm respectively. Experiments and theoretical analysis display that the breakdown threshold of the film depends mainly on the thickness of non-hole layer, and the basic thickness for the isolating of PEPC's glow discharge chamber is 60μm.
The isolate of discharge chamber is a key issue of metal material shell PEPC. We have constructed the testing facilities for breakthrough and modulating discharge respectively. Testing samples of anodized film include three kinds of thickness which are 30μm、60μm and 100μm respectively. Experiments and theoretical analysis display that the breakdown threshold of the film depends mainly on the thickness of non-hole layer, and the basic thickness for the isolating of PEPC's glow discharge chamber is 60μm.
2000,
12.
Abstract:
The application of GS algorithm in the phase analysis of high-power laser is described. Through simulations, the good iterative results are given. This provides the database for designing appropriate phase plate, and also gives a phase measurement method for beam diagnose system.
The application of GS algorithm in the phase analysis of high-power laser is described. Through simulations, the good iterative results are given. This provides the database for designing appropriate phase plate, and also gives a phase measurement method for beam diagnose system.
