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RSS2001 Vol. 13, No. 06
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2001,
13.
Abstract:
A 2-1/2D cylindrical full electromagnetic particle-in-cell code is used to simulate magnetic field penetration in plasma erosion opening switch. The simulation results show that the penetrat ion of magnetic field into plasma is due to Hall field on the condition that the characteristic Hall length is small compared with the ion collisionless skin depth. Strong two dimensional effect on the field penetrating speed should be included in the fluid analysis for a plasma space distribution with high density gradient. The region where the magnetic field has penetrated shows no neutral characteristic, and the electric field can accelerate ions to the cathode and form the vacuum sheath.
A 2-1/2D cylindrical full electromagnetic particle-in-cell code is used to simulate magnetic field penetration in plasma erosion opening switch. The simulation results show that the penetrat ion of magnetic field into plasma is due to Hall field on the condition that the characteristic Hall length is small compared with the ion collisionless skin depth. Strong two dimensional effect on the field penetrating speed should be included in the fluid analysis for a plasma space distribution with high density gradient. The region where the magnetic field has penetrated shows no neutral characteristic, and the electric field can accelerate ions to the cathode and form the vacuum sheath.
2001,
13.
Abstract:
According to the requirements of driving flash-lamp, a high pulsed power supply (PPS) based on capacitors as energy storage elements is designed. This paper analyzes in detail the faults of high pulsed power supply for high power laser. Such as capacitor internal short-circuit, main bus breakdown to ground, flashlamp sudden short or break. The fault current and voltage waveforms were given by circuit simulations. Based on the analysis and computation, the protection strategy with the fast fuse and ZnO was put forward, which can reduce the demage of PPS to the lower extent and provent the personnel safe and collateral property from the all threats. The preliminary experiments demonstrated that the design of the PPS can satisfy the project requirements.
According to the requirements of driving flash-lamp, a high pulsed power supply (PPS) based on capacitors as energy storage elements is designed. This paper analyzes in detail the faults of high pulsed power supply for high power laser. Such as capacitor internal short-circuit, main bus breakdown to ground, flashlamp sudden short or break. The fault current and voltage waveforms were given by circuit simulations. Based on the analysis and computation, the protection strategy with the fast fuse and ZnO was put forward, which can reduce the demage of PPS to the lower extent and provent the personnel safe and collateral property from the all threats. The preliminary experiments demonstrated that the design of the PPS can satisfy the project requirements.
2001,
13.
Abstract:
In room temperature the fuel gas storage halflife of the thin-wall (wall-thicknees less than 1m m) glass microsphere is only a few days, it is difficult to be used for ICF. To efficiently prolong the half-life of such type targets, and meet the need of ICF experiments, the special device for storing the targets was developed. All the targets are immerged in liquid-nitrogen (LN2), after being sealed in vacuum. During this period the change of Si 1.74keV X-ray counts were measured a few times with the low energy X-ray multi-channel analyzer. The results of experiment indicate that, in the environment of - 96℃, the fuel storage half-life of target has been successfully extended to 100~300d from 3~10d. However, the surface roughness of target was not obviously changed.
In room temperature the fuel gas storage halflife of the thin-wall (wall-thicknees less than 1m m) glass microsphere is only a few days, it is difficult to be used for ICF. To efficiently prolong the half-life of such type targets, and meet the need of ICF experiments, the special device for storing the targets was developed. All the targets are immerged in liquid-nitrogen (LN2), after being sealed in vacuum. During this period the change of Si 1.74keV X-ray counts were measured a few times with the low energy X-ray multi-channel analyzer. The results of experiment indicate that, in the environment of - 96℃, the fuel storage half-life of target has been successfully extended to 100~300d from 3~10d. However, the surface roughness of target was not obviously changed.
2001,
13.
Abstract:
The wavelengths, weighted oscillator strength, Einstein transition coefficients for H-like ions Mg11+, Al12+ were calculated by using the General-purpose Relativistic Atomic Structure Program. The results show that the wavelengths are in good agreement with the experimental data available. In addition, making full use of the results, our present work uses the isoelectronic line ratio measurement to improve the temperature diagnosis method of reference, namely, utilizes the alike spectral line pair of the same ionized state of two labelled atoms with adjacent atomic numbers (D Z= 1, 2) to measure the electronic temperature, for obtaining accurate results of the electronic temperature.
The wavelengths, weighted oscillator strength, Einstein transition coefficients for H-like ions Mg11+, Al12+ were calculated by using the General-purpose Relativistic Atomic Structure Program. The results show that the wavelengths are in good agreement with the experimental data available. In addition, making full use of the results, our present work uses the isoelectronic line ratio measurement to improve the temperature diagnosis method of reference, namely, utilizes the alike spectral line pair of the same ionized state of two labelled atoms with adjacent atomic numbers (D Z= 1, 2) to measure the electronic temperature, for obtaining accurate results of the electronic temperature.
2001,
13.
Abstract:
Based upon instantaneous output spectra of xenon flashlamp, a unique dynamic modeling program has been constructed to predict the gain performance of multisegment Nd: glass laser amplifiers. The model, which includes the all dynamic modulations from flashlamp discharging to laser outputting, may be used in laser amplifier system optimizations. The influences of disk thickness and Nd2O3 doping level on gain performance are studied with the modeling program. Under the condition of the same pumping lever, the stored fluence and the small signal gain are determined by the doping-thick ness products(Nd ion concentration by slab thickness)in the MAS slab.
Based upon instantaneous output spectra of xenon flashlamp, a unique dynamic modeling program has been constructed to predict the gain performance of multisegment Nd: glass laser amplifiers. The model, which includes the all dynamic modulations from flashlamp discharging to laser outputting, may be used in laser amplifier system optimizations. The influences of disk thickness and Nd2O3 doping level on gain performance are studied with the modeling program. Under the condition of the same pumping lever, the stored fluence and the small signal gain are determined by the doping-thick ness products(Nd ion concentration by slab thickness)in the MAS slab.
2001,
13.
Abstract:
The main principle of Relativistic Two-Stream Amplifier (RTSA) is the two-stream interaction mechanism. This two-stream interaction mechanism generates the two-stream instability. In the R TSA, there are two concentric circular beams and they propagate through the wave guide in the same direction. The energy exchanging is between the inner beam and outer beam, and the output power of microwave at the end cavity (output cavity) of RTSA is only pumped from the outer electron beam. The effect of inner beam supports the two-stream instability. And for a high power signal, the linear theory does not fit and the nonlinear theory is adopted. Using the MA GIC PIC simulation program, the author simulated the S-band RTSA, studied the two-stream interaction mechanism and deeply understood the two-str
The main principle of Relativistic Two-Stream Amplifier (RTSA) is the two-stream interaction mechanism. This two-stream interaction mechanism generates the two-stream instability. In the R TSA, there are two concentric circular beams and they propagate through the wave guide in the same direction. The energy exchanging is between the inner beam and outer beam, and the output power of microwave at the end cavity (output cavity) of RTSA is only pumped from the outer electron beam. The effect of inner beam supports the two-stream instability. And for a high power signal, the linear theory does not fit and the nonlinear theory is adopted. Using the MA GIC PIC simulation program, the author simulated the S-band RTSA, studied the two-stream interaction mechanism and deeply understood the two-str
2001,
13.
Abstract:
With a bunching segment and a shortened first cell, the 4+1/2 cell RF gun produced in CAEP has been proved experimentally to be effective in reducing electron back bombardment. The analysis of the electric field distribution and electron motion in bunching segment of multi cell RF gun is presented in this paper. The electron capture efficiency and electron trajectory with different initial phase are calculated using Runge-Kutta method. The function of the bunching segment is discussed. The calculated parameters of the 4+1/2 cell RF gun agree well with the experimental results.
With a bunching segment and a shortened first cell, the 4+1/2 cell RF gun produced in CAEP has been proved experimentally to be effective in reducing electron back bombardment. The analysis of the electric field distribution and electron motion in bunching segment of multi cell RF gun is presented in this paper. The electron capture efficiency and electron trajectory with different initial phase are calculated using Runge-Kutta method. The function of the bunching segment is discussed. The calculated parameters of the 4+1/2 cell RF gun agree well with the experimental results.
2001,
13.
Abstract:
In this paper, experiments of a lateral semi-insulating GaAs photoconductive semiconductor switch triggered by nano-second and pico-second and femto-second laser pulse are reported. The switches have all-solid-state insulated by multi-layer transparent dielectrics. Dark insulating intensity of the 8 mm-gap GaAs switch reached to 30kV. Jitter-free current wave form of the 3 mm-gap and 8 mm-gap GaAs switches were observed when triggered by the laser pulse. The current could be as high as 560A when the 3 mm-gap switch was under the voltage of 2 kV and triggered with 8 ns and 1.2 mJ laser pulse. The same device also revealed good temperal characteristics when trigger with pico-second laser and 108 repeat frequency laser pulse strings. The rising time the 3 mm-gap switch response is less than 2
In this paper, experiments of a lateral semi-insulating GaAs photoconductive semiconductor switch triggered by nano-second and pico-second and femto-second laser pulse are reported. The switches have all-solid-state insulated by multi-layer transparent dielectrics. Dark insulating intensity of the 8 mm-gap GaAs switch reached to 30kV. Jitter-free current wave form of the 3 mm-gap and 8 mm-gap GaAs switches were observed when triggered by the laser pulse. The current could be as high as 560A when the 3 mm-gap switch was under the voltage of 2 kV and triggered with 8 ns and 1.2 mJ laser pulse. The same device also revealed good temperal characteristics when trigger with pico-second laser and 108 repeat frequency laser pulse strings. The rising time the 3 mm-gap switch response is less than 2
2001,
13.
Abstract:
UWB (ultra-wideband) scattering signal can provide direct observation of time signatures and natural time-gating. This feature is useful in identifying structural response mechanisms and is essential when realizing the inverse scattering target imaging. With the development of UWB pulser and antenna and waveform sampling, the acquisition of UWB scattering signal in time-domain become available gradually. In this paper, the mea surement technology in time-domain and data processing method of scattering pulse from the perfect conductive scattered illuminated by UWB electromagnetic pulse is described. The physical mechanism of scattering, the procedure for measurement and distillation of scattering signal and the method of calculating the impulse response of scattering object is also depicted
UWB (ultra-wideband) scattering signal can provide direct observation of time signatures and natural time-gating. This feature is useful in identifying structural response mechanisms and is essential when realizing the inverse scattering target imaging. With the development of UWB pulser and antenna and waveform sampling, the acquisition of UWB scattering signal in time-domain become available gradually. In this paper, the mea surement technology in time-domain and data processing method of scattering pulse from the perfect conductive scattered illuminated by UWB electromagnetic pulse is described. The physical mechanism of scattering, the procedure for measurement and distillation of scattering signal and the method of calculating the impulse response of scattering object is also depicted
2001,
13.
Abstract:
In this paper, the formula of power density of waveguide with annular plasma filled in finite magnetic field has been derived. In order to increase output power of high-power microwave devices, some parameters must be taken into account, such as the thickness and the density of the annular plasma. Through careful calculation, it has been found that there are great influences to the power density by the plasma density, annular plasma thickness. The influential mechanism has been analyzed by calculating the electric field distributed on the transverse direction.
In this paper, the formula of power density of waveguide with annular plasma filled in finite magnetic field has been derived. In order to increase output power of high-power microwave devices, some parameters must be taken into account, such as the thickness and the density of the annular plasma. Through careful calculation, it has been found that there are great influences to the power density by the plasma density, annular plasma thickness. The influential mechanism has been analyzed by calculating the electric field distributed on the transverse direction.
2001,
13.
Abstract:
In this paper, the nonlinear coup led equations are presented and the pulse properties of an optical parametric chirped pulse amplification(OPCPA) system are studied. By numerical simulation, it is discovered that signal temporal profiles and spectral profiles broaden after saturated amplification, but the pulse and spectra broadening don't affect the S/N coefficient of the compressed pulse. Analysis and discussions are also given.
In this paper, the nonlinear coup led equations are presented and the pulse properties of an optical parametric chirped pulse amplification(OPCPA) system are studied. By numerical simulation, it is discovered that signal temporal profiles and spectral profiles broaden after saturated amplification, but the pulse and spectra broadening don't affect the S/N coefficient of the compressed pulse. Analysis and discussions are also given.
2001,
13.
Abstract:
The experiments of EMP coupling to shielded cable have been done in the horizontally polarized dipole radiator. The test system of the experiment and the measurement method are both introduced in this article. The tested coaxial cable is under different conditions—the cable is above the ground or on the ground, both terminals are open circuit, short circuit or one is open and the other is short. The core and the sheath are connected via a resistance of 50W . The results of the experiments are analysed based on double transmission lines theory and good agreement is obtained.
The experiments of EMP coupling to shielded cable have been done in the horizontally polarized dipole radiator. The test system of the experiment and the measurement method are both introduced in this article. The tested coaxial cable is under different conditions—the cable is above the ground or on the ground, both terminals are open circuit, short circuit or one is open and the other is short. The core and the sheath are connected via a resistance of 50W . The results of the experiments are analysed based on double transmission lines theory and good agreement is obtained.
2001,
13.
Abstract:
In this paper, the transmission character of the periodically capacitor loaded coaxial transmission line is analyzed. We applied this kind of transmission line into the 1/4 wavelength transmission line cavity design. With both the transmission line theory and numerical simulation methods, we obtained the resonating frequency and Q factor as functions of the disk radius and the disk numbers. The possibility of this kind of met hod in decreasing the cavity's volume is discussed and its application in the design of the RF cavity of a proton cyclotron is presented as well in the paper.
In this paper, the transmission character of the periodically capacitor loaded coaxial transmission line is analyzed. We applied this kind of transmission line into the 1/4 wavelength transmission line cavity design. With both the transmission line theory and numerical simulation methods, we obtained the resonating frequency and Q factor as functions of the disk radius and the disk numbers. The possibility of this kind of met hod in decreasing the cavity's volume is discussed and its application in the design of the RF cavity of a proton cyclotron is presented as well in the paper.
2001,
13.
Abstract:
The system and the method of the Ag－ and He collision experiment are described, and the distinguishing feature of this experiment system is that only one detector was used. The single-elect rondetachment cross-sections of Ag－ in collision with He has been measured in the energy range of 5~30keV by the growth-rate method. The typical value of the cross section of Ag－ impacting on He at 20keV is 6.6×10－16cm2. The experimental uncertainty of the results is about ±8% in this work.
The system and the method of the Ag－ and He collision experiment are described, and the distinguishing feature of this experiment system is that only one detector was used. The single-elect rondetachment cross-sections of Ag－ in collision with He has been measured in the energy range of 5~30keV by the growth-rate method. The typical value of the cross section of Ag－ impacting on He at 20keV is 6.6×10－16cm2. The experimental uncertainty of the results is about ±8% in this work.
2001,
13.
Abstract:
Photo-cathode superconducting accelerator experiment system include Nd:YAG Mode-locked laser, Cs2Te cathode, 2+1/2 RF gun, L band 3.5MW Microwave source, 1.3GHz superconducting cavity, 500W continue microwave source, coaxial input coupler, 4.2K cryostat, helium liquefied system, control system, beam diagnostic, and vacuum system. In June 2001, the experiment of this system have been done in CAEP. The electron beam energy gained in superconducting cavity is 0.58MeV, micro-pulse current is 0.1A.
Photo-cathode superconducting accelerator experiment system include Nd:YAG Mode-locked laser, Cs2Te cathode, 2+1/2 RF gun, L band 3.5MW Microwave source, 1.3GHz superconducting cavity, 500W continue microwave source, coaxial input coupler, 4.2K cryostat, helium liquefied system, control system, beam diagnostic, and vacuum system. In June 2001, the experiment of this system have been done in CAEP. The electron beam energy gained in superconducting cavity is 0.58MeV, micro-pulse current is 0.1A.
2001,
13.
Abstract:
Several factors, which influence beam qualities during relativistic intense electron beams transportation, have been analyzed systematically in this report. Aimed at the principal contradictions manifested in the different energy areas of beam, corresponding measurements are adopted to restrain the harmful effects of space charge, fluctuation of transporting magnetic fields, corkscrew motion or BBU instability respectively. All the measurements can be summed up in choice of appropriate radius of beam and matched transport magnetic field on the design of beam transport system. The principal strategy of transport field arrangement is presented, and the overall arrangements of beam transport system of “SL-I” LIA are described.
Several factors, which influence beam qualities during relativistic intense electron beams transportation, have been analyzed systematically in this report. Aimed at the principal contradictions manifested in the different energy areas of beam, corresponding measurements are adopted to restrain the harmful effects of space charge, fluctuation of transporting magnetic fields, corkscrew motion or BBU instability respectively. All the measurements can be summed up in choice of appropriate radius of beam and matched transport magnetic field on the design of beam transport system. The principal strategy of transport field arrangement is presented, and the overall arrangements of beam transport system of “SL-I” LIA are described.
2001,
13.
Abstract:
The development of beambased alignment system for Hefei Light Source (HLS) is presented. In this system, a switchable shunt resistor was installed on quadrupole to bypass a small percentage of the magnet current, and solid-state relays were used to switch the shunt resistor. The system can be used to measure the offset of the beam position monitor (BPM) with respect to the magnetic center of a quadrupole. Some measurement results for HLS are given.
The development of beambased alignment system for Hefei Light Source (HLS) is presented. In this system, a switchable shunt resistor was installed on quadrupole to bypass a small percentage of the magnet current, and solid-state relays were used to switch the shunt resistor. The system can be used to measure the offset of the beam position monitor (BPM) with respect to the magnetic center of a quadrupole. Some measurement results for HLS are given.
2001,
13.
Abstract:
A new united aerodynamic window is investigated and it combined the axial injection and vacuum pump together. The reformed window have many new character, the throat area can be adjusted by a circle valve and the multi-pole board is stored in injector, sealing cavity and suction cavity respectively. Many work have been done on it, the sealing quality and beam quality have been reported in the former work. The latest work is that a distance auto-motived system has been done. With the gas pressure in bottle is changing, the valve can be adjusted by the auto-motived system. And only one bottle can be enough to usage.It is joined with the COIL laser and works successfully. The latest results are the lowest sealing pressure is only 0.67KPa, the exhausted gas is 35g/s and the Strhl ratio is up t
A new united aerodynamic window is investigated and it combined the axial injection and vacuum pump together. The reformed window have many new character, the throat area can be adjusted by a circle valve and the multi-pole board is stored in injector, sealing cavity and suction cavity respectively. Many work have been done on it, the sealing quality and beam quality have been reported in the former work. The latest work is that a distance auto-motived system has been done. With the gas pressure in bottle is changing, the valve can be adjusted by the auto-motived system. And only one bottle can be enough to usage.It is joined with the COIL laser and works successfully. The latest results are the lowest sealing pressure is only 0.67KPa, the exhausted gas is 35g/s and the Strhl ratio is up t
2001,
13.
Abstract:
NCl(a1D ) and NCl(b1S ) were produced from the reaction of HN3 with Cl generated by the microwave discharge of Cl2. The emission spectrum of NCl(a1D ) and NCl(b1S ) were observe d and their intensities dependent on the Cl2 flow rate and the ratio of He flow rate to Cl2 flow rate were investigated. The results suggest that there is a n optimum range of Cl2 flow rate for the intensity of NCl(a1D ) and NCl(b1S ) emission at a fixed He flow rate, and the optimum ratio of He flow rate to C l2 flow rate increases with the increasing He flow rate. The optimum He∶Cl2 is 30∶1 to 100∶1 under this experimental conditions（He flow rate being 5~40 L/min）.
NCl(a1D ) and NCl(b1S ) were produced from the reaction of HN3 with Cl generated by the microwave discharge of Cl2. The emission spectrum of NCl(a1D ) and NCl(b1S ) were observe d and their intensities dependent on the Cl2 flow rate and the ratio of He flow rate to Cl2 flow rate were investigated. The results suggest that there is a n optimum range of Cl2 flow rate for the intensity of NCl(a1D ) and NCl(b1S ) emission at a fixed He flow rate, and the optimum ratio of He flow rate to C l2 flow rate increases with the increasing He flow rate. The optimum He∶Cl2 is 30∶1 to 100∶1 under this experimental conditions（He flow rate being 5~40 L/min）.
2001,
13.
Abstract:
Based on the diffraction integral theory, the quasi-focused characteristics of a laser beam with waviness modulation have been studied theoretically and numerically in the paper. The effect of waviness modulation and defocused distances on the energy-concentration-rate and intensity distribution as well as pattern of defocused spot have been analyzed in detail. The computing results show that to control the defocused distance or to decrease the size of waviness modulation in the median frequency will improve the energy-concentration of focal spot.
Based on the diffraction integral theory, the quasi-focused characteristics of a laser beam with waviness modulation have been studied theoretically and numerically in the paper. The effect of waviness modulation and defocused distances on the energy-concentration-rate and intensity distribution as well as pattern of defocused spot have been analyzed in detail. The computing results show that to control the defocused distance or to decrease the size of waviness modulation in the median frequency will improve the energy-concentration of focal spot.
2001,
13.
Abstract:
Shearing interferometer is used to investigate the degradation of light beam quality caused by the aerodynamic window's flow field. The principle of investigation is described. The problem of fringe patterns analyzing is solved. In the experiment, the degradation of light beam quality which is caused by the free-vortex aerodynamic window's flow field working in steady states is investigated.
Shearing interferometer is used to investigate the degradation of light beam quality caused by the aerodynamic window's flow field. The principle of investigation is described. The problem of fringe patterns analyzing is solved. In the experiment, the degradation of light beam quality which is caused by the free-vortex aerodynamic window's flow field working in steady states is investigated.
2001,
13.
Abstract:
In interferometry, the interesting information is mostly concerned in cross-correlation function (CCF), which will generate the modulation of interference patterns. So with the Fresnel diffraction theory and Collins equation, the propagation of CCF in dividing-wavefront interferometry is studied in this paper. And the formula about its propagation in terms of optical matrix elements is given. The intensity distribution of interference patterns in Mechelson and Shearing Interferometer is also analyzed.
In interferometry, the interesting information is mostly concerned in cross-correlation function (CCF), which will generate the modulation of interference patterns. So with the Fresnel diffraction theory and Collins equation, the propagation of CCF in dividing-wavefront interferometry is studied in this paper. And the formula about its propagation in terms of optical matrix elements is given. The intensity distribution of interference patterns in Mechelson and Shearing Interferometer is also analyzed.
2001,
13.
Abstract:
The nuclear reactor pumped lasing model (NRPLM) was proposed and the power efficiency function was derived in the present work. The power efficiency was studied as a function of cell pressure, xenon concentration, He and Ar fractions. The lasing model was checked using experimental results. The parameters of the efficiency function were obtained. The relationship between the parameters and their influence on the efficiency were explored. The present work will benefit the future experimental designs.
The nuclear reactor pumped lasing model (NRPLM) was proposed and the power efficiency function was derived in the present work. The power efficiency was studied as a function of cell pressure, xenon concentration, He and Ar fractions. The lasing model was checked using experimental results. The parameters of the efficiency function were obtained. The relationship between the parameters and their influence on the efficiency were explored. The present work will benefit the future experimental designs.
2001,
13.
Abstract:
The similar propagation property of flattened Gaussian beams (FGBs) and super-Gaussian beams (SGBs) is studied i n the rectangular coordinate system. It is shown that two FGB and SGB with the same M2-factor but different waist width exhibit similar intensity distributions at the position of the equal generalized Fresnel number, as they propagate through an unapertured ABCD optical system. For the apertured case and focusing by a spherically aberrated lens, similar intensity profiles at the equal propagation distance can be also obtained, if the two FGB and SGB have the same M2-factor and waist width.
The similar propagation property of flattened Gaussian beams (FGBs) and super-Gaussian beams (SGBs) is studied i n the rectangular coordinate system. It is shown that two FGB and SGB with the same M2-factor but different waist width exhibit similar intensity distributions at the position of the equal generalized Fresnel number, as they propagate through an unapertured ABCD optical system. For the apertured case and focusing by a spherically aberrated lens, similar intensity profiles at the equal propagation distance can be also obtained, if the two FGB and SGB have the same M2-factor and waist width.
2001,
13.
Abstract:
Starting from Collins integral, t he focusing characteristics of Gaussian beams passing through a bifocal lens are studied. Analytical expressions for the axial intensity, waist widths and posit ions in the x and y directions are derived for the unapertured case. It is pointed out by detailed numerical calculations that the point of maximum intensity along the axis is located closer to one waist or at the position of one waist, but it can not exceed the larger focal point of the lens. Moreover, the shift relative to the waist position increases with increasing aperture effect.
Starting from Collins integral, t he focusing characteristics of Gaussian beams passing through a bifocal lens are studied. Analytical expressions for the axial intensity, waist widths and posit ions in the x and y directions are derived for the unapertured case. It is pointed out by detailed numerical calculations that the point of maximum intensity along the axis is located closer to one waist or at the position of one waist, but it can not exceed the larger focal point of the lens. Moreover, the shift relative to the waist position increases with increasing aperture effect.
2001,
13.
Abstract:
In this paper, the transferring characteristics of detecting error to Adaptive Optical System (AOS) under realistic atmospheric turbulence are researched. Results show that the residual error will be increased due to beacon light’s decreasing when Shack-Hartmann wavefront sensor is used in probing very low-light-level object. Because a constant term caused by sky background light is concluded in the control residual error besides another terms, it is demanded that the aberration of S-H WFS calibrating optical system be very small.
In this paper, the transferring characteristics of detecting error to Adaptive Optical System (AOS) under realistic atmospheric turbulence are researched. Results show that the residual error will be increased due to beacon light’s decreasing when Shack-Hartmann wavefront sensor is used in probing very low-light-level object. Because a constant term caused by sky background light is concluded in the control residual error besides another terms, it is demanded that the aberration of S-H WFS calibrating optical system be very small.
2001,
13.
Abstract:
An introduction is given to the principle, method and experiment system of measurement of small-signal gain on solid propellant combustion driven CO2 gasdynamic laser. Measure optical path design of small-signal gain, operating principle of thermistor infrared detector, design of filter and amplifier circuit of gain output signal and hardware configuration as well as rules and methods of software development of data acquisiti on system are mainly presented. The typical experimental results are also given, which show that the amplification method can measure the smallsignal gain accurately.
An introduction is given to the principle, method and experiment system of measurement of small-signal gain on solid propellant combustion driven CO2 gasdynamic laser. Measure optical path design of small-signal gain, operating principle of thermistor infrared detector, design of filter and amplifier circuit of gain output signal and hardware configuration as well as rules and methods of software development of data acquisiti on system are mainly presented. The typical experimental results are also given, which show that the amplification method can measure the smallsignal gain accurately.
2001,
13.
Abstract:
The thermalelastic model of laser irradiating optical material is established. Analytical method is applied to study the tensile profile induced by laser irradiation in disk sample, and the laser induced damage thresholds are evaluated independently under three mechanical boundaries: free, fixed and arbitrary. The results show that mechanical boundaries have great influence on laser induced damage threshold(LIDT), and optimal boundary under which tensile stress is eliminated is available theoretically when particular arbitrary boundary is applied.
The thermalelastic model of laser irradiating optical material is established. Analytical method is applied to study the tensile profile induced by laser irradiation in disk sample, and the laser induced damage thresholds are evaluated independently under three mechanical boundaries: free, fixed and arbitrary. The results show that mechanical boundaries have great influence on laser induced damage threshold(LIDT), and optimal boundary under which tensile stress is eliminated is available theoretically when particular arbitrary boundary is applied.
2001,
13.
Abstract:
Vanadium dioxide thin films have been irradiated by electron beam with energy of 1.7MeV and fluence of 1.25×1013/cm2, 1.25×1014/cm2, 1.25×1015/cm2 respectively. Structure and V ion valence of the films have been studied by X-ray diffraction and X-ray photoelectron spectroscopy before and after electron irradiation, and their phase-transition properties have been characterized by optical transmittance analysis methods. The results show that the valence variation of V ion and the changes of XRD patterns of the irradiated samples have been detected, and the optical properties during phase-transition process have been changed obviously by electron irradiation.
Vanadium dioxide thin films have been irradiated by electron beam with energy of 1.7MeV and fluence of 1.25×1013/cm2, 1.25×1014/cm2, 1.25×1015/cm2 respectively. Structure and V ion valence of the films have been studied by X-ray diffraction and X-ray photoelectron spectroscopy before and after electron irradiation, and their phase-transition properties have been characterized by optical transmittance analysis methods. The results show that the valence variation of V ion and the changes of XRD patterns of the irradiated samples have been detected, and the optical properties during phase-transition process have been changed obviously by electron irradiation.
