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RSS2002 Vol. 14, No. 02
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2002,
14.
Abstract:
A beam profile diagnostic system of high current, short pulse electron based on Cerenkov radiation is introduced. Cerenkov radiation signals produced by thin quartz foil placed in the beam path are detected with streak camera. Experiments confirming Cerenkov radiation and time-resolved beam profile measurement are realized with this system on the 2MeV injector of CAEP. The resolution of the system is estimated to be about 0.74 mm and 1.75ns.
A beam profile diagnostic system of high current, short pulse electron based on Cerenkov radiation is introduced. Cerenkov radiation signals produced by thin quartz foil placed in the beam path are detected with streak camera. Experiments confirming Cerenkov radiation and time-resolved beam profile measurement are realized with this system on the 2MeV injector of CAEP. The resolution of the system is estimated to be about 0.74 mm and 1.75ns.
2002,
14.
Abstract:
This paper analyses the mechanism responsible for focusing intense relativistic electron beams by the use of YBa2Cu3O7-d high-temperature superconductor lens. The transporting and focusing effects of the superconductor lens are confirmed in the experiments. The results show that the superconductor lens possesses obvious focusing effects, and makes the distribution of the electrons focused in the beam transverse-section evener.
This paper analyses the mechanism responsible for focusing intense relativistic electron beams by the use of YBa2Cu3O7-d high-temperature superconductor lens. The transporting and focusing effects of the superconductor lens are confirmed in the experiments. The results show that the superconductor lens possesses obvious focusing effects, and makes the distribution of the electrons focused in the beam transverse-section evener.
2002,
14.
Abstract:
A coaxial multi-gap multi-channel closing switch with stainless steel spring ring gap is designed and investigated. The switch is triggered by a pulse applied to the cylindrical electrode outside the discharging channel through parasitic capacitance coupling. The jitter of the switch is reduced by several short distance gas gaps in series, and its inductance is reduced by multi-channel discharge. The switch chamber is filled with 0.3MP a N2 gas, and its operating voltage and conducting current are about 100kV and 200kA, respectively. The experimental results indicate that the switch is of low inductance (15～30nH), low jitter (～3ns), and stable breakdown performance.
A coaxial multi-gap multi-channel closing switch with stainless steel spring ring gap is designed and investigated. The switch is triggered by a pulse applied to the cylindrical electrode outside the discharging channel through parasitic capacitance coupling. The jitter of the switch is reduced by several short distance gas gaps in series, and its inductance is reduced by multi-channel discharge. The switch chamber is filled with 0.3MP a N2 gas, and its operating voltage and conducting current are about 100kV and 200kA, respectively. The experimental results indicate that the switch is of low inductance (15～30nH), low jitter (～3ns), and stable breakdown performance.
2002,
14.
Abstract:
In developing gas filled hohlra um targets, fabrication of polyimide with thickness no more than 1m m plays an important role, and its kernel technology is synthetic polypyromellitamic acid. Th e solution viscosity is measured during the synthetic process by the method of supersonic wave. Preliminary experiments have been performed to determine the effects of reaction conditions in order to get high molecular weight in the solution. The best synthetic condition is concluded as follows: solid pyromellitic dianhydride should be added to diamine solutions, mole ratio of dianhydride and diamine should be 1.01～1.02∶1, the reaction temperature should be 0～5℃, water in solvent should be least and reaction should be stopped in suitable time.
In developing gas filled hohlra um targets, fabrication of polyimide with thickness no more than 1m m plays an important role, and its kernel technology is synthetic polypyromellitamic acid. Th e solution viscosity is measured during the synthetic process by the method of supersonic wave. Preliminary experiments have been performed to determine the effects of reaction conditions in order to get high molecular weight in the solution. The best synthetic condition is concluded as follows: solid pyromellitic dianhydride should be added to diamine solutions, mole ratio of dianhydride and diamine should be 1.01～1.02∶1, the reaction temperature should be 0～5℃, water in solvent should be least and reaction should be stopped in suitable time.
2002,
14.
Abstract:
The designing rules of new data file formats of laser irradiation experiments are introduced in this paper. Object-oriented programs are designed in studying experimental data of the laser facilities. The new format data files are combinations of the experiment data and diagnostic configuration data, which are applied in data processing and analysis. The edit of agnostic configuration data in data acquisition program is also d escribed.
The designing rules of new data file formats of laser irradiation experiments are introduced in this paper. Object-oriented programs are designed in studying experimental data of the laser facilities. The new format data files are combinations of the experiment data and diagnostic configuration data, which are applied in data processing and analysis. The edit of agnostic configuration data in data acquisition program is also d escribed.
2002,
14.
Abstract:
Through spectral analysis method, a theoretical analysis of wavefront aberration is made in intense laser system. The random phase screen is applied to reconstruct the wavefront in the domain of low spatial frequency, and a new iterative algorithm is proposed and used to reconstruct the wavefront in the domain of high spatial frequency. With the reconstructed wavefront, the effect of the wavefront aberration on the function of CSG is calculated. The preliminary conclusion is presented, which shows the rule of the tolerance of input wavefont aberration for CSG.
Through spectral analysis method, a theoretical analysis of wavefront aberration is made in intense laser system. The random phase screen is applied to reconstruct the wavefront in the domain of low spatial frequency, and a new iterative algorithm is proposed and used to reconstruct the wavefront in the domain of high spatial frequency. With the reconstructed wavefront, the effect of the wavefront aberration on the function of CSG is calculated. The preliminary conclusion is presented, which shows the rule of the tolerance of input wavefont aberration for CSG.
2002,
14.
Abstract:
Beam sampling grating are used to sending a known fraction of transmitted light into a calormeter for energy diagnostics in final focusing optical system of ICF. This paper discusses diffractive efficiency as a function of period, depth, duty cycle and incident angel. The algorithm that we applied is rigorous coupled-wave analysis. By calculation, we can get some useful informations for practical fabrication of the beam sampling grating.
Beam sampling grating are used to sending a known fraction of transmitted light into a calormeter for energy diagnostics in final focusing optical system of ICF. This paper discusses diffractive efficiency as a function of period, depth, duty cycle and incident angel. The algorithm that we applied is rigorous coupled-wave analysis. By calculation, we can get some useful informations for practical fabrication of the beam sampling grating.
2002,
14.
Abstract:
This paper presents the method of linear weight-sum to beam positioning budget on the basis of ICF request on targeting the approach of equal or unequal probability to allocate errors to each optical element. Based on the relationship between the motion of the optical components and beam position on target, The position error budget of the optical components was evaluated, which was referred to as the maximum range. Lots of raytrace were performed, the position error budget were modified by law of the normal distribution. An overview of position error budget of the components provided.
This paper presents the method of linear weight-sum to beam positioning budget on the basis of ICF request on targeting the approach of equal or unequal probability to allocate errors to each optical element. Based on the relationship between the motion of the optical components and beam position on target, The position error budget of the optical components was evaluated, which was referred to as the maximum range. Lots of raytrace were performed, the position error budget were modified by law of the normal distribution. An overview of position error budget of the components provided.
2002,
14.
Abstract:
The wavefront power spectral density (PSD) can give the spatial frequency distribution of wavefront aberration, limit the waviness and the roughness, and specify the large components employed in high power density solid-state laser for inertial confinement fusion (ICF). The definition and the calculation of the PSD are given in this article. In experiment, a large phase shifting Fizeau interferometer was used to test the transmis sive wavefront of a Nd glass, creating the one dimension wavefront PSD. Same time, relationship between the PSD and the RMS is shown in the paper.
The wavefront power spectral density (PSD) can give the spatial frequency distribution of wavefront aberration, limit the waviness and the roughness, and specify the large components employed in high power density solid-state laser for inertial confinement fusion (ICF). The definition and the calculation of the PSD are given in this article. In experiment, a large phase shifting Fizeau interferometer was used to test the transmis sive wavefront of a Nd glass, creating the one dimension wavefront PSD. Same time, relationship between the PSD and the RMS is shown in the paper.
2002,
14.
Abstract:
Holographic interferometry is a effective measurement method to diagnose the electronic density of laser plasma.It has very high temporal and spatial resolution.In this paper, ultraviolet Holographic interferometry system on “XG-Ⅱ” is interpreted briefly,and the experimental results are presented.
Holographic interferometry is a effective measurement method to diagnose the electronic density of laser plasma.It has very high temporal and spatial resolution.In this paper, ultraviolet Holographic interferometry system on “XG-Ⅱ” is interpreted briefly,and the experimental results are presented.
2002,
14.
Abstract:
A kind of new phase aberration correcting method is introduced—using a phase countervailing mirror to correct t he low-frequency phase error. This method is mainly aimed to correct the static phase aberration caused by the fishing error on the optics. With random phase screen simulating the low-frequency phase aberration of the amplifiers, and the other effect of amplifiers on the beam is neglected, a beam propagation is setup. A new concept of equivalent phase plate is introduced and the phase of the mirror, as the invert phase of the equivalent phase plate, is easy to get. Finally, simulation of the correcting course was done.
A kind of new phase aberration correcting method is introduced—using a phase countervailing mirror to correct t he low-frequency phase error. This method is mainly aimed to correct the static phase aberration caused by the fishing error on the optics. With random phase screen simulating the low-frequency phase aberration of the amplifiers, and the other effect of amplifiers on the beam is neglected, a beam propagation is setup. A new concept of equivalent phase plate is introduced and the phase of the mirror, as the invert phase of the equivalent phase plate, is easy to get. Finally, simulation of the correcting course was done.
2002,
14.
Abstract:
It benefits to decrease the engineering cost and to debase the technical crisis that analysis polarizer composed of amplifier Nd3+:glass slabs located with the Brewster angle in large scale multi-passes laser facility. The relationships of the isolation efficiency with the numbers of slab, the growth of the amplifizer and the switch efficiency of Pockels cell are calculated theoretically. The experimental results indicated that the output energy of this isolation system is 1:8 as Pockels cell working on and off.
It benefits to decrease the engineering cost and to debase the technical crisis that analysis polarizer composed of amplifier Nd3+:glass slabs located with the Brewster angle in large scale multi-passes laser facility. The relationships of the isolation efficiency with the numbers of slab, the growth of the amplifizer and the switch efficiency of Pockels cell are calculated theoretically. The experimental results indicated that the output energy of this isolation system is 1:8 as Pockels cell working on and off.
2002,
14.
Abstract:
Intense pulse X-ray is used to irradiate Si-SiO2 interface. C-V curves and I-V curves are tested be fore and after X-ray irradiation. Experiment results show that C-V curves have the following changes under intense pulse X-ray irradiation: (1) Flatband Volt age of high frequency C-V has a little positive drift, sodoes the gate volt age in depletion region, which is different from a negative drift under low-power pulse X-ray irradiation; (2) Oxide capacitance of low and high frequency C-V lift after intense pulse X-ray irradiation; (3) Minimum capacitance of high frequency C-V lifts after intense pulse X-ray irradiation. Experiment results also show that slopes of I-V subthreshold curves have gradually aber rant under six times intense pulse X-ray irradiation. One reason is that intense pul
Intense pulse X-ray is used to irradiate Si-SiO2 interface. C-V curves and I-V curves are tested be fore and after X-ray irradiation. Experiment results show that C-V curves have the following changes under intense pulse X-ray irradiation: (1) Flatband Volt age of high frequency C-V has a little positive drift, sodoes the gate volt age in depletion region, which is different from a negative drift under low-power pulse X-ray irradiation; (2) Oxide capacitance of low and high frequency C-V lift after intense pulse X-ray irradiation; (3) Minimum capacitance of high frequency C-V lifts after intense pulse X-ray irradiation. Experiment results also show that slopes of I-V subthreshold curves have gradually aber rant under six times intense pulse X-ray irradiation. One reason is that intense pul
2002,
14.
Abstract:
By making use of our own program mPND1D for modeling of the semiconductor devices, The response of a PIN diode limiter to the high power microwave (HPM) is calculated, results for different conditions have been compared, and also we analyzed the diode cutoff frequency for microwave sources. The results show that the cutoff frequency increases with the rising of the source amplitude , and it decreases with the decreasing of pulse length and device temperature.
By making use of our own program mPND1D for modeling of the semiconductor devices, The response of a PIN diode limiter to the high power microwave (HPM) is calculated, results for different conditions have been compared, and also we analyzed the diode cutoff frequency for microwave sources. The results show that the cutoff frequency increases with the rising of the source amplitude , and it decreases with the decreasing of pulse length and device temperature.
2002,
14.
Abstract:
This paper describes a neuro-fuzzy system to process the data of microwave effects on the comp uters. Base on the neuro-fuzzy system, the evaluation model of microwave effect s is developed. Compared with the original experiment sample, the neuro-fuzzy system gave very close results. Meanwhile, the evaluation model developed in this paper can predict the interference threshold for similar effect events if sufficient data have been analyzed. The neuro-fuzzy system has potential app lication to data processing of microwave effects.
This paper describes a neuro-fuzzy system to process the data of microwave effects on the comp uters. Base on the neuro-fuzzy system, the evaluation model of microwave effect s is developed. Compared with the original experiment sample, the neuro-fuzzy system gave very close results. Meanwhile, the evaluation model developed in this paper can predict the interference threshold for similar effect events if sufficient data have been analyzed. The neuro-fuzzy system has potential app lication to data processing of microwave effects.
2002,
14.
Abstract:
This paper introduces the characteristic of electromagnetic pulse produced during electrostatic discharge(ESD EM P). The method producing ESD EMP by ESD simulator was studied, and the waveform and frequency spectrum of the ESD EMP was given Based on the study of ESD simulator, the ESD EMP was produced firstly in GTEM cell by the cooperating of the ESD simulator and GTEM cell. The ESD EMP produced by this method was repeated and Well-distributed, and it has good linearity. The experiments show that the simulator can simulate the ESD EMP in laboratory.
This paper introduces the characteristic of electromagnetic pulse produced during electrostatic discharge(ESD EM P). The method producing ESD EMP by ESD simulator was studied, and the waveform and frequency spectrum of the ESD EMP was given Based on the study of ESD simulator, the ESD EMP was produced firstly in GTEM cell by the cooperating of the ESD simulator and GTEM cell. The ESD EMP produced by this method was repeated and Well-distributed, and it has good linearity. The experiments show that the simulator can simulate the ESD EMP in laboratory.
2002,
14.
Abstract:
A spontaneous Raman imaging system which can monitor the concentrations of major species in flow field in real time has been described. The results of the low pressure O2 are presented and the lowest pressure we measure is 133Pa. This technique can be calibrated in real time by an introduction of a known amount of N2. The error is less than 8%. The measurement precision of O2(a1Δ) concentration will be improved largely when this technique is applied to monitor chemical oxygen-iodine laser singlet oxygen generator performance.
A spontaneous Raman imaging system which can monitor the concentrations of major species in flow field in real time has been described. The results of the low pressure O2 are presented and the lowest pressure we measure is 133Pa. This technique can be calibrated in real time by an introduction of a known amount of N2. The error is less than 8%. The measurement precision of O2(a1Δ) concentration will be improved largely when this technique is applied to monitor chemical oxygen-iodine laser singlet oxygen generator performance.
2002,
14.
Abstract:
The concept of damage morphology criterion is eatablished to study how the different failure modes of optical materials irradiated by CW laser appear under different interaction conditions. The analytic solutions of temperature and stress profiles generated during laser he ating are obtained by the way of Hankel transform, then damage thresholds for elastic failure and melting are determined respectively. The dependence of damage form on material properties and laser parameters is evaluated and the simplified relationship is presented to predict the damage form of optical materials irradiated by CW laser. At last, experiment results are presented to prove the validity of the damage morphology criterion.
The concept of damage morphology criterion is eatablished to study how the different failure modes of optical materials irradiated by CW laser appear under different interaction conditions. The analytic solutions of temperature and stress profiles generated during laser he ating are obtained by the way of Hankel transform, then damage thresholds for elastic failure and melting are determined respectively. The dependence of damage form on material properties and laser parameters is evaluated and the simplified relationship is presented to predict the damage form of optical materials irradiated by CW laser. At last, experiment results are presented to prove the validity of the damage morphology criterion.
2002,
14.
Abstract:
In order to increase the coupling efficiency of diode laser arrays side-pumped slab laser and efficiently the mode of slab laser, the wave-guide coupling system with the high coupling efficiency has been designed by means of a ray-tracing method. The large end surface of the coupling system is connected with high power diode laser arrays, and the small end surface is connected with the laser slab. The experimental results show that the optical coupling efficiency was 85%, and an output beam with a uniform profile has been achieved in the slab. The wave-guide systems have been used in laser experiment, and the near diffraction-limited beam has been obtained in the slab laser.
In order to increase the coupling efficiency of diode laser arrays side-pumped slab laser and efficiently the mode of slab laser, the wave-guide coupling system with the high coupling efficiency has been designed by means of a ray-tracing method. The large end surface of the coupling system is connected with high power diode laser arrays, and the small end surface is connected with the laser slab. The experimental results show that the optical coupling efficiency was 85%, and an output beam with a uniform profile has been achieved in the slab. The wave-guide systems have been used in laser experiment, and the near diffraction-limited beam has been obtained in the slab laser.
2002,
14.
Abstract:
The differential equation followed by increase of smallscale instability in both of gain and loss media is obtained from the nonlinear wave equation based on Bespalov-Talanov theory. A comparison of different properties of small-scale self-focusing intense laser in two media is analyzed. Variations of cutoff spatial frequency, the fastest growing frequency, integral exponential gain of perturbation with different parameters are specified. Two expressions of maximal and minimal distance of ripple increase are obtained and effect of gain and loss on filamentsforming distance is deduced.
The differential equation followed by increase of smallscale instability in both of gain and loss media is obtained from the nonlinear wave equation based on Bespalov-Talanov theory. A comparison of different properties of small-scale self-focusing intense laser in two media is analyzed. Variations of cutoff spatial frequency, the fastest growing frequency, integral exponential gain of perturbation with different parameters are specified. Two expressions of maximal and minimal distance of ripple increase are obtained and effect of gain and loss on filamentsforming distance is deduced.
2002,
14.
Abstract:
The effects of undulator phase errors on the Free Electron Laser small signal gain is analyzed and discussed. The gain reduction factor due to the phase error is given analytically for low-gain regimes, it shows that degradation of the gain is similar to that of the spontaneous radiation, has a simple exponential relation with square of the rms phase error, and the linear variation part of phase error induces the position shift of maxi mum gain. The result also shows that the Madey's theorem still hold in the presence of phase error. The gain reduction factor due to the phase error for high-gain regimes also can be given in a simple way.
The effects of undulator phase errors on the Free Electron Laser small signal gain is analyzed and discussed. The gain reduction factor due to the phase error is given analytically for low-gain regimes, it shows that degradation of the gain is similar to that of the spontaneous radiation, has a simple exponential relation with square of the rms phase error, and the linear variation part of phase error induces the position shift of maxi mum gain. The result also shows that the Madey's theorem still hold in the presence of phase error. The gain reduction factor due to the phase error for high-gain regimes also can be given in a simple way.
2002,
14.
Abstract:
The Zernike modal wavefront reconstruction error of Hartmann sensor on measuring the atmospheric disturbed wavefront analyzed in this paper. It’s shown that the wavefront reconstruction error is concerned with sub-aperture configuration type and the total Zernike mode number used in wavefront reconstruction algorithm. Experiential formulas to calculate the wavefront reconstruction error of a Hartmann sensor in Kolmogorov turbulence are also deduced. The experimenal data are analyzed and compared between two Hartmann sensors with 8x8 and 32x32 sub-apertures configuration respectively.
The Zernike modal wavefront reconstruction error of Hartmann sensor on measuring the atmospheric disturbed wavefront analyzed in this paper. It’s shown that the wavefront reconstruction error is concerned with sub-aperture configuration type and the total Zernike mode number used in wavefront reconstruction algorithm. Experiential formulas to calculate the wavefront reconstruction error of a Hartmann sensor in Kolmogorov turbulence are also deduced. The experimenal data are analyzed and compared between two Hartmann sensors with 8x8 and 32x32 sub-apertures configuration respectively.
2002,
14.
Abstract:
The Errors in the paper entitled “M2 factor and mode coefficients of partially coherent Gaussian beams” (X. Chu and B. Zhang) published in 〈High Power Laser & Particle Beams〉12(6), (Nov.), 2000 (cited as Chu's paper) are point out and analyzed physically. First, the new result could not be found in Chu's paper, because the same method and same results were given in Ref. ［1］ and ［2］ published in 〈Opt. Lett.〉, 23 (13) July, 1. 1998 (Gori F, Santarsiero M, Borghi R, and Guattari G), and , 38(25), Sept. 1, 1999 (Santarsiero M, Gori F, Borghi R, and Guattari G.) , respectively. Moreover, in Chu's paper any physical interpretation about the subjects "how to determine the waist size v0 in a unique way" and "how to experimentally realize their partially coherent Gaussian beam
The Errors in the paper entitled “M2 factor and mode coefficients of partially coherent Gaussian beams” (X. Chu and B. Zhang) published in 〈High Power Laser & Particle Beams〉12(6), (Nov.), 2000 (cited as Chu's paper) are point out and analyzed physically. First, the new result could not be found in Chu's paper, because the same method and same results were given in Ref. ［1］ and ［2］ published in 〈Opt. Lett.〉, 23 (13) July, 1. 1998 (Gori F, Santarsiero M, Borghi R, and Guattari G), and , 38(25), Sept. 1, 1999 (Santarsiero M, Gori F, Borghi R, and Guattari G.) , respectively. Moreover, in Chu's paper any physical interpretation about the subjects "how to determine the waist size v0 in a unique way" and "how to experimentally realize their partially coherent Gaussian beam
2002,
14.
Abstract:
The paper introduces three beam measurement systems based on the VXI bus in Hefei Light Source(HLS)，Hefei storage ring’s DC current transformer measurement system(DCCT)，beam close orbit detection system(COD) and photon position measurement system. Three measurement systems are integrated in one VXI DAQ module. An IPC controls the systems through an MXI2 cable, and supplys the service of sending data package in the LAN. The software is programmed by LabVIEW, which reduces bus much developing work.
The paper introduces three beam measurement systems based on the VXI bus in Hefei Light Source(HLS)，Hefei storage ring’s DC current transformer measurement system(DCCT)，beam close orbit detection system(COD) and photon position measurement system. Three measurement systems are integrated in one VXI DAQ module. An IPC controls the systems through an MXI2 cable, and supplys the service of sending data package in the LAN. The software is programmed by LabVIEW, which reduces bus much developing work.
2002,
14.
Abstract:
A new analytic model describing photovoltaic effect in photovoltaic infrared detectors is put forward, which disposes the relation between photoelectron concentrations at the two sides of the depletion region of a p-n junction in common cases while Lu Qisheng’s analytic model does in special case. By comparison among the new model, Lu’s model and another analytic model, it is explained why the former two models, different from the latter, can explain signal saturation effect which is observed in photovoltaic infrared detectors under laser irradiation.
A new analytic model describing photovoltaic effect in photovoltaic infrared detectors is put forward, which disposes the relation between photoelectron concentrations at the two sides of the depletion region of a p-n junction in common cases while Lu Qisheng’s analytic model does in special case. By comparison among the new model, Lu’s model and another analytic model, it is explained why the former two models, different from the latter, can explain signal saturation effect which is observed in photovoltaic infrared detectors under laser irradiation.
2002,
14.
Abstract:
The spectrum of temperature fluctuations have been measured by 1m m and 10m m diameter wires. A method for measuring outer scale is presented. The results of measurement show that at least 50% temperature spectra deviate from kolmogorov's “－5/3 low” over complex terrain. The results measured by a single sensor and a couple of sensors respectively agree well with each other. 80% of the outer scales are less than 7 meters.
The spectrum of temperature fluctuations have been measured by 1m m and 10m m diameter wires. A method for measuring outer scale is presented. The results of measurement show that at least 50% temperature spectra deviate from kolmogorov's “－5/3 low” over complex terrain. The results measured by a single sensor and a couple of sensors respectively agree well with each other. 80% of the outer scales are less than 7 meters.
2002,
14.
Abstract:
The laser output window is very important to the high power lasers. But when the power is very high the conventional output crystal window can not meet the needs of lasers. And the aerodynamic window can take the place of crystal window. This paper analyzes the current study situations and requirement for aerodynamic windows in the field of high power lasers, and then discusses the differences similarities of the laser beam quality evaluating factors' properties. According as the properties of aerodynamic windows it proposes a method of evaluating the laser beam quality of aerodynamic windows for high power lasers using Strehl ratio, at the same time using the beam factor as accessorial factor. This evaluating method is independent of the types of aerodynamic windows, and has been used in
The laser output window is very important to the high power lasers. But when the power is very high the conventional output crystal window can not meet the needs of lasers. And the aerodynamic window can take the place of crystal window. This paper analyzes the current study situations and requirement for aerodynamic windows in the field of high power lasers, and then discusses the differences similarities of the laser beam quality evaluating factors' properties. According as the properties of aerodynamic windows it proposes a method of evaluating the laser beam quality of aerodynamic windows for high power lasers using Strehl ratio, at the same time using the beam factor as accessorial factor. This evaluating method is independent of the types of aerodynamic windows, and has been used in
2002,
14.
Abstract:
In this paper, the progress of the study on long-range propagation of ultrashort and ultrastrong laser pulses in air is outlined and the corresponding models are introduced, in which the dynamical spatial replenishment model is emphasized, the coupling equation originated from it and the corresponding numerical results are given. The validity of the models for different cases are analyzed.
In this paper, the progress of the study on long-range propagation of ultrashort and ultrastrong laser pulses in air is outlined and the corresponding models are introduced, in which the dynamical spatial replenishment model is emphasized, the coupling equation originated from it and the corresponding numerical results are given. The validity of the models for different cases are analyzed.
2002,
14.
Abstract:
A systematic in vestigation to the responses of specimens made of LY12 aluminum alloy subjected to different levels of pre-load and heated with different heating-rate is performed using a Glee ble-1500 thermal-mechanical material testing system. The near-tip metallurgra phics is also observed and analyzed. The investigation results show that both temperature and heating-rate play significant roles in the mechanical behavior o f LY12. For the same level of pre-load, an increase in heating-rate will increase both the yield and fracture temperature, and the high heating-rate induced inconsistence of local temperature accounts for the severe defect in the material and the failure of the meterial.
A systematic in vestigation to the responses of specimens made of LY12 aluminum alloy subjected to different levels of pre-load and heated with different heating-rate is performed using a Glee ble-1500 thermal-mechanical material testing system. The near-tip metallurgra phics is also observed and analyzed. The investigation results show that both temperature and heating-rate play significant roles in the mechanical behavior o f LY12. For the same level of pre-load, an increase in heating-rate will increase both the yield and fracture temperature, and the high heating-rate induced inconsistence of local temperature accounts for the severe defect in the material and the failure of the meterial.
2002,
14.
Abstract:
The study on high power laser diode arrays end-pumping Nd：YLF laser amplifier is discussed in this paper. The amplifier’s coupling structure ineludes a microlens which collimates the pumping light and a lensduct which focuses it into the laser rod. Its coupling efficiency is up to 72.2%. The slope efficiency of the laser oscillator composed by the amplifier is 35.9%. A small signal gain of 2.66 is obtained at 1053nm.
The study on high power laser diode arrays end-pumping Nd：YLF laser amplifier is discussed in this paper. The amplifier’s coupling structure ineludes a microlens which collimates the pumping light and a lensduct which focuses it into the laser rod. Its coupling efficiency is up to 72.2%. The slope efficiency of the laser oscillator composed by the amplifier is 35.9%. A small signal gain of 2.66 is obtained at 1053nm.
2002,
14.
Abstract:
The paper introduces the measurement and research of some beam parameters using tune measurement system for Hefei Light So urce (HLS), which include the betatron tune, beta function, natural chromaticity , corrected chromaticity, and central frequency. Additionally, it also describes the measurement of the influence of DC clearing electrodes on the betatron tune shift and gives, some measurement results. The measurement results are compared with the theoretical values and they are in good agreement.
The paper introduces the measurement and research of some beam parameters using tune measurement system for Hefei Light So urce (HLS), which include the betatron tune, beta function, natural chromaticity , corrected chromaticity, and central frequency. Additionally, it also describes the measurement of the influence of DC clearing electrodes on the betatron tune shift and gives, some measurement results. The measurement results are compared with the theoretical values and they are in good agreement.
2002,
14.
Abstract:
In this paper, the distributions of temperature and thermal stress in the transparent optical materials, resulting from the laser energy-absorption of a defect, were obtained analytically. When the shape of the defect is point-like, the maximum value of normal stress in y-direction locates on the boundary. With the increase of x coordinate, the stress decreases obviously. But when the shape of flaw is changed to linear, the normal stress in y-direction is minimum at the boundary and is singular at two ends of the linear flaw. Based on a simple crack model, the relative stress intensity factor (SIF) and effects of various parameters on SIF were analyzed and discussed. The main conclusions include that SIF increase monotonously with the enlargement of the ratio between the crack length and t
In this paper, the distributions of temperature and thermal stress in the transparent optical materials, resulting from the laser energy-absorption of a defect, were obtained analytically. When the shape of the defect is point-like, the maximum value of normal stress in y-direction locates on the boundary. With the increase of x coordinate, the stress decreases obviously. But when the shape of flaw is changed to linear, the normal stress in y-direction is minimum at the boundary and is singular at two ends of the linear flaw. Based on a simple crack model, the relative stress intensity factor (SIF) and effects of various parameters on SIF were analyzed and discussed. The main conclusions include that SIF increase monotonously with the enlargement of the ratio between the crack length and t
2002,
14.
Abstract:
Besides the conventional single-pulset rain generation, the Ti: sapphire laser system sometimes produces two or even more pulses should proper conditions be satisfied. By treating the pulse propagati on within the laser gain medium with the help of split-step Fourier method, independently taking into account of the dispersion originating from the prism sequence, and making use of a generalized pulsewidth formula, the double-pulse formation process is numerically simulated in a self-consistent scheme. It is revealed that the condition of a tiny net negative dispersion with strong chirp is mandatory. The double-pulse generation manifests itself in a narrow range of physical parameters, thereby pose it as a metastable state.
Besides the conventional single-pulset rain generation, the Ti: sapphire laser system sometimes produces two or even more pulses should proper conditions be satisfied. By treating the pulse propagati on within the laser gain medium with the help of split-step Fourier method, independently taking into account of the dispersion originating from the prism sequence, and making use of a generalized pulsewidth formula, the double-pulse formation process is numerically simulated in a self-consistent scheme. It is revealed that the condition of a tiny net negative dispersion with strong chirp is mandatory. The double-pulse generation manifests itself in a narrow range of physical parameters, thereby pose it as a metastable state.
2002,
14.
Abstract:
Large area glow discharge plasma that is transparent and highly conductive can be used as electrodes in Pockels cell to extend the switch aperture. To investigate this technology, a glow discharging chamber with a clear aperture of 5cm×5cm was constructed, and hollow cathode, button cathode, pin cathode, bar cathode and bar anode were designed and produced. Using CCD imaging system, the discharging uniformity of different cathodes was tested with bar anode and under the different pressure pre-ionization voltage and main discharging voltage. A uniform plasma can be obtained with a hollow cathode when the pre-ionization voltage is about 700V, the pressure is about 30Pa, and the main discharging voltage is about 4kV, which can be used for the plasma electrode of Pockels cell.
Large area glow discharge plasma that is transparent and highly conductive can be used as electrodes in Pockels cell to extend the switch aperture. To investigate this technology, a glow discharging chamber with a clear aperture of 5cm×5cm was constructed, and hollow cathode, button cathode, pin cathode, bar cathode and bar anode were designed and produced. Using CCD imaging system, the discharging uniformity of different cathodes was tested with bar anode and under the different pressure pre-ionization voltage and main discharging voltage. A uniform plasma can be obtained with a hollow cathode when the pre-ionization voltage is about 700V, the pressure is about 30Pa, and the main discharging voltage is about 4kV, which can be used for the plasma electrode of Pockels cell.
2002,
14.
Abstract:
This paper theoretically explores the non-Fourier heat conduction process initiated by a rectangular pulsed heat source in a finite slab with insulated boundaries. Green's function and finite integral transform technique are used to obtain analytical solutions for tempera ture fields in the slab. The propagation and reflection of thermal wave, the effects of heat source and slab's geometric parameter on temperature fields are discussed. It is found that temperature wave frequency at a given location in the s lab is relevant to slab's thickness and its thermal relaxation time while the amplitude of temperature wave bears a relation with heat source's distribution are a and pulse duration.
This paper theoretically explores the non-Fourier heat conduction process initiated by a rectangular pulsed heat source in a finite slab with insulated boundaries. Green's function and finite integral transform technique are used to obtain analytical solutions for tempera ture fields in the slab. The propagation and reflection of thermal wave, the effects of heat source and slab's geometric parameter on temperature fields are discussed. It is found that temperature wave frequency at a given location in the s lab is relevant to slab's thickness and its thermal relaxation time while the amplitude of temperature wave bears a relation with heat source's distribution are a and pulse duration.
2002,
14.
Abstract:
The article presents a new algorithm of wavefront reconstruction based on the cyclic radial shear interferomerter. The algorithm is a technique that the actual wavefront can be reconstructed directly and accurately from the distribution of phase difference which is obtained from the radial shearing pattern by Fourier transform profilometry. It can help to measure accurately the distorted wavefront of ICF in-process. An experiment is presented to test the algorithm.
The article presents a new algorithm of wavefront reconstruction based on the cyclic radial shear interferomerter. The algorithm is a technique that the actual wavefront can be reconstructed directly and accurately from the distribution of phase difference which is obtained from the radial shearing pattern by Fourier transform profilometry. It can help to measure accurately the distorted wavefront of ICF in-process. An experiment is presented to test the algorithm.
2002,
14.
Abstract:
The employment principle of HF(hydrogen fluoride) overtone chemical laser is described in brief in the article, and a new high supersonic low temperature nozzle manufactured is introduced in detail, including its structure and the experimental parameters set method. In the experiments on the laser, gain is observed. Several valuable results can be concluded by analyzing the measured experimental data. Test and measure methods in nozzle experiments established and the numerical simulation method of value are introduced.
The employment principle of HF(hydrogen fluoride) overtone chemical laser is described in brief in the article, and a new high supersonic low temperature nozzle manufactured is introduced in detail, including its structure and the experimental parameters set method. In the experiments on the laser, gain is observed. Several valuable results can be concluded by analyzing the measured experimental data. Test and measure methods in nozzle experiments established and the numerical simulation method of value are introduced.
