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RSS2002 Vol. 14, No. 05
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2002,
14.
Abstract:
Linear introduction accelerator is expected to generate small diameter xray spots with high intensity． The interaction of the electron beam with plasmas generated at the xray converter will make the spot on target increase with time and debase the x ray dose and the imaging resolving power. A distributed target is developed which has about 24 pieces of thin 0.05mm tantalum films distributed over 1cm． Due to the structure adoption, the distributed target material over a large volume decreases the energy deposition per unit volume and hence reduces the temperature of target surface, then reduces the initial plasma formalizing and its expansion velocity. In this paper, the comparison and analysis with two kinds of target structures are presented using numerical calculation and experimen
Linear introduction accelerator is expected to generate small diameter xray spots with high intensity． The interaction of the electron beam with plasmas generated at the xray converter will make the spot on target increase with time and debase the x ray dose and the imaging resolving power. A distributed target is developed which has about 24 pieces of thin 0.05mm tantalum films distributed over 1cm． Due to the structure adoption, the distributed target material over a large volume decreases the energy deposition per unit volume and hence reduces the temperature of target surface, then reduces the initial plasma formalizing and its expansion velocity. In this paper, the comparison and analysis with two kinds of target structures are presented using numerical calculation and experimen
2002,
14.
Abstract:
Building time and jitter of the Marx generator are mainly depend on work state of spark gap switch during operating. Meanwhile they are related to amplitude and polarity of trigging voltage. The paper briefly describes physical process of conductance of gas spark gap switch. In order to minimize building time and jitter, experiments were performed to optimize work state related parameters of the Marx generator. As result, the total building time and jitter are (1629±8.4)ns for HeavenΙ electron beam accelerator. It fills the jitter requirement of MOPA system less than 20ns．
Building time and jitter of the Marx generator are mainly depend on work state of spark gap switch during operating. Meanwhile they are related to amplitude and polarity of trigging voltage. The paper briefly describes physical process of conductance of gas spark gap switch. In order to minimize building time and jitter, experiments were performed to optimize work state related parameters of the Marx generator. As result, the total building time and jitter are (1629±8.4)ns for HeavenΙ electron beam accelerator. It fills the jitter requirement of MOPA system less than 20ns．
2002,
14.
Abstract:
The incident angles have a heavy effect on the intense pulsed electr on beam energy deposition profile, energy deposition fraction and beam current transmission fraction in material. This article presents electron beam energy deposition profile and energy deposition fraction versus electron energy(0.5-2.0MeV), at various incident angles for three aluminum targets of various thickness via theoretical calculation. The intense pulsed electron beam current transmission fractions versus electron energy(0.4-1.4MeV) at various incident a ngles for three thickness of carbon targets were also theoretically calculated. The calculation results indicate that the deposition energy in unit mass of material surface layer increases with the rise of electron beam incident angle, and electron beam with low
The incident angles have a heavy effect on the intense pulsed electr on beam energy deposition profile, energy deposition fraction and beam current transmission fraction in material. This article presents electron beam energy deposition profile and energy deposition fraction versus electron energy(0.5-2.0MeV), at various incident angles for three aluminum targets of various thickness via theoretical calculation. The intense pulsed electron beam current transmission fractions versus electron energy(0.4-1.4MeV) at various incident a ngles for three thickness of carbon targets were also theoretically calculated. The calculation results indicate that the deposition energy in unit mass of material surface layer increases with the rise of electron beam incident angle, and electron beam with low
2002,
14.
Abstract:
This article presents a BPM (Beam Position Monitor) calibration system developed for phase II of HLS (Hefei Synchrotron Radiation Light Source). The paper describes the development of the test stand and emphasizes key technique that guarantees mechanical accuracy of the system. The test equipment is of erect type and the geometric accuracy of ±0.01mm is obtained. The system has been served for calibrating BPM pickups, which are mounted in vacuum chambers of inject section. The electrical center of the BPMs is measured with respect to the geometrical center in the calibration machine. The eligible vacuum chambers have been installed in the storage ring.
This article presents a BPM (Beam Position Monitor) calibration system developed for phase II of HLS (Hefei Synchrotron Radiation Light Source). The paper describes the development of the test stand and emphasizes key technique that guarantees mechanical accuracy of the system. The test equipment is of erect type and the geometric accuracy of ±0.01mm is obtained. The system has been served for calibrating BPM pickups, which are mounted in vacuum chambers of inject section. The electrical center of the BPMs is measured with respect to the geometrical center in the calibration machine. The eligible vacuum chambers have been installed in the storage ring.
2002,
14.
Abstract:
The investigation on the solid liner implosion driven by the high energy density physical facility FP1 is reviewed in this paper. The contents include the characteristics of FP1 and the main physics experiments of Al liner implosion, two liner impact, micro jet or ejection, and dynamic pulsed buckling. The tipical results of these experiments which have been carried out on the facility are described.
The investigation on the solid liner implosion driven by the high energy density physical facility FP1 is reviewed in this paper. The contents include the characteristics of FP1 and the main physics experiments of Al liner implosion, two liner impact, micro jet or ejection, and dynamic pulsed buckling. The tipical results of these experiments which have been carried out on the facility are described.
2002,
14.
Abstract:
The Mach number of the gas flow from the supersonic nozzle in a gaspuff Zpinch was determined by the two pressure transducer method. The measured Mach number rises with time and reaches to a maximum value of 4.25 that is close to 4.8, the value from a steadystate gas flow calculation. This result shows that the steadystate gas flow calculation can be used to estimate the Mach number of gas flow from a supersonic nozzle in gas puff Zpinch.
The Mach number of the gas flow from the supersonic nozzle in a gaspuff Zpinch was determined by the two pressure transducer method. The measured Mach number rises with time and reaches to a maximum value of 4.25 that is close to 4.8, the value from a steadystate gas flow calculation. This result shows that the steadystate gas flow calculation can be used to estimate the Mach number of gas flow from a supersonic nozzle in gas puff Zpinch.
2002,
14.
Abstract:
This paper presents some preliminary results of a laser synchrotron source (LSS) based on Compton/Thomson scattering of electron and laser beams in headon and offaxis geometry. This approach opens a new route toward ultrashort, highbrightness, quasimonochromatic tunable Xray / γray source by utilizing existing technology of the linear accelerator technology and highpower, highrepetition rate laser system.
This paper presents some preliminary results of a laser synchrotron source (LSS) based on Compton/Thomson scattering of electron and laser beams in headon and offaxis geometry. This approach opens a new route toward ultrashort, highbrightness, quasimonochromatic tunable Xray / γray source by utilizing existing technology of the linear accelerator technology and highpower, highrepetition rate laser system.
2002,
14.
Abstract:
Energy spectrum analytic system of 200MeV linear accelerator in NSRL is used to detect the beam energy and to guild the machine adjustment. This paper shows the former status of the system, and analyses some of its shortcomings. In the NSRL projectII, the system is redesigned, and has been installed recently. This paper also describes the results of physics computation and some newest preliminary experiments.
Energy spectrum analytic system of 200MeV linear accelerator in NSRL is used to detect the beam energy and to guild the machine adjustment. This paper shows the former status of the system, and analyses some of its shortcomings. In the NSRL projectII, the system is redesigned, and has been installed recently. This paper also describes the results of physics computation and some newest preliminary experiments.
2002,
14.
Abstract:
A 100kV/2A threephase constantcurrent repetitiverate charging equipment was designed and constructed. A threephase LC converter is adopted as constantcurrent power source. Six Insulated Gate Bipolar Transistors(IGBTs) are connected in parallel to control the stop of charge. A Programmable Logical Controller(PLC) is the central element of the control unit. The equipment is used in the repetitiverate discharge features test of the switch. It works stably under the conditions of 2A charging current, 10Hz operating voltage, 100kV repetitiverate and 1μF capacitor.
A 100kV/2A threephase constantcurrent repetitiverate charging equipment was designed and constructed. A threephase LC converter is adopted as constantcurrent power source. Six Insulated Gate Bipolar Transistors(IGBTs) are connected in parallel to control the stop of charge. A Programmable Logical Controller(PLC) is the central element of the control unit. The equipment is used in the repetitiverate discharge features test of the switch. It works stably under the conditions of 2A charging current, 10Hz operating voltage, 100kV repetitiverate and 1μF capacitor.
2002,
14.
Abstract:
The characteristics of stimulated Brillouin scattering reflectivity and pulse compression ratio for broadband (15GHz) KrF laser radiation pump in SF6 gas are investigated numerically and experimentally in this paper. It has obtained that a peak reflectivity of 40% and 45% has been measured at 1.6MPa with lenses of focal length 15cm and 30cm, respectively, and a saturated region of SBS reflectivity is discovered at pump energy above 60mJ. SBS pulse compression ratio decreases with pump energy at 0.85MPa.and the maximum of pulse compression ration measured is 5. SBS numerical mode for a broadband multimode KrF laser pump has been built up in this paper. The basic premises of the mode are that SBS arises from each laser line with coupling to some extent. In this paper numerical results have b
The characteristics of stimulated Brillouin scattering reflectivity and pulse compression ratio for broadband (15GHz) KrF laser radiation pump in SF6 gas are investigated numerically and experimentally in this paper. It has obtained that a peak reflectivity of 40% and 45% has been measured at 1.6MPa with lenses of focal length 15cm and 30cm, respectively, and a saturated region of SBS reflectivity is discovered at pump energy above 60mJ. SBS pulse compression ratio decreases with pump energy at 0.85MPa.and the maximum of pulse compression ration measured is 5. SBS numerical mode for a broadband multimode KrF laser pump has been built up in this paper. The basic premises of the mode are that SBS arises from each laser line with coupling to some extent. In this paper numerical results have b
2002,
14.
Abstract:
The laser combustion diagnostic system was developed. With tunable lasers, the temperatures and species in methaneair flame were given by laserinduced fluorescence, Raman scattering and CARS. The spectralfit precision was less than 10% for single shot measurement. The fluorescence images of OH were obtained in the alcohol and methaneair flames. The structures of the temperature fields were analyzed.
The laser combustion diagnostic system was developed. With tunable lasers, the temperatures and species in methaneair flame were given by laserinduced fluorescence, Raman scattering and CARS. The spectralfit precision was less than 10% for single shot measurement. The fluorescence images of OH were obtained in the alcohol and methaneair flames. The structures of the temperature fields were analyzed.
2002,
14.
Abstract:
A novel tabletop Ti: Sapphire/ KrF ultrashort pulse laser system was developed for laser matter interaction researches in CIAE. The characterization and optimization of output parameters of this UV shortpulse laser system were described in this letter. With the use and properly choosing parameters of off axis amplification scheme and prism pair pulse compressor, the laser system achieved in an output of 50mJ energy, 220fs pulse duration at 248nm wavelength, and the beam was focused to an intensity of 1017W/cm2 on target.
A novel tabletop Ti: Sapphire/ KrF ultrashort pulse laser system was developed for laser matter interaction researches in CIAE. The characterization and optimization of output parameters of this UV shortpulse laser system were described in this letter. With the use and properly choosing parameters of off axis amplification scheme and prism pair pulse compressor, the laser system achieved in an output of 50mJ energy, 220fs pulse duration at 248nm wavelength, and the beam was focused to an intensity of 1017W/cm2 on target.
2002,
14.
Abstract:
Stimulated Brillouin Scattering (SBS) is a process to product the phase conjugated light. Now it is being pursued as a means for pulse compression, beam combination and wavefront reversal. To achieve a high quality short pulse beam, to select a proper medium is very important. In this paper, the effect of parameters of Brillouin mediums on pulse compression of Stimulated Brillouin Scattering process used as a SBS generator are shown theoretically and experimentally. The theoretical model includes transient process, absorption of medium, and pump depletion. The results show that pulse compression ratio is 8 in 0.68MPa. Dependence of pulse compression on the acoustic lifetime and Brillouin gain coefficients is investigated respectively. The results show that pulse compression versus parame
Stimulated Brillouin Scattering (SBS) is a process to product the phase conjugated light. Now it is being pursued as a means for pulse compression, beam combination and wavefront reversal. To achieve a high quality short pulse beam, to select a proper medium is very important. In this paper, the effect of parameters of Brillouin mediums on pulse compression of Stimulated Brillouin Scattering process used as a SBS generator are shown theoretically and experimentally. The theoretical model includes transient process, absorption of medium, and pump depletion. The results show that pulse compression ratio is 8 in 0.68MPa. Dependence of pulse compression on the acoustic lifetime and Brillouin gain coefficients is investigated respectively. The results show that pulse compression versus parame
2002,
14.
Abstract:
The influence of the ponderomotive force on interaction of the ultrashort pulse laser with the solid plasma was studied by measuring the frequency shift induced by the movement of plasma critical surface. When laser intensity reache 1017W/cm2, the ponderomotive force reduced the thermal expanding velocity of laserinduced plasma, and produced a very steep density profile. In this case, the vacuum heating becomes the dominant absorption mechanism instead of the resonant absorption.
The influence of the ponderomotive force on interaction of the ultrashort pulse laser with the solid plasma was studied by measuring the frequency shift induced by the movement of plasma critical surface. When laser intensity reache 1017W/cm2, the ponderomotive force reduced the thermal expanding velocity of laserinduced plasma, and produced a very steep density profile. In this case, the vacuum heating becomes the dominant absorption mechanism instead of the resonant absorption.
2002,
14.
Abstract:
Some important technological problems with stable operation of the twoside electron beam pumped main amplifier used in the “Heavn1” high power KrF excimer laser system are described. They are the problems of the electric breakdown of the insulator support for water dielectric transmission lines, anode foil installation of large area electron beam diode, shape of Hibachi ribs that contact the pressure foil, and formation of diode post pulses and their damage to the anode foil and cathode emitter. Emphasis is put on the effect of different mainswitch breakdown times on diode post pulses and the determination of the optimal breakdown time.
Some important technological problems with stable operation of the twoside electron beam pumped main amplifier used in the “Heavn1” high power KrF excimer laser system are described. They are the problems of the electric breakdown of the insulator support for water dielectric transmission lines, anode foil installation of large area electron beam diode, shape of Hibachi ribs that contact the pressure foil, and formation of diode post pulses and their damage to the anode foil and cathode emitter. Emphasis is put on the effect of different mainswitch breakdown times on diode post pulses and the determination of the optimal breakdown time.
2002,
14.
Abstract:
A time and spaceresolved flatgrating spectrometer is developed. It is composed of a varied linespace grating with 2 400 lp/mm or 1 200 lp/mm, a gated MCP framing camera and an optical CCD system. The principle, the construction and adjustment method of the spectrometer are presented. With this spectrometer the timeresolved emission spectrum of Al plasma are measured in “Xingguang” laser facility and the time and spaceresolved absorption spectrum of Al plasma is observed in “Shenguang” laser facility respectively. The spectrum resolution is about 0.02~0.05nm.
A time and spaceresolved flatgrating spectrometer is developed. It is composed of a varied linespace grating with 2 400 lp/mm or 1 200 lp/mm, a gated MCP framing camera and an optical CCD system. The principle, the construction and adjustment method of the spectrometer are presented. With this spectrometer the timeresolved emission spectrum of Al plasma are measured in “Xingguang” laser facility and the time and spaceresolved absorption spectrum of Al plasma is observed in “Shenguang” laser facility respectively. The spectrum resolution is about 0.02~0.05nm.
2002,
14.
Abstract:
1w and 3 w near field beam quality for highintensity THG have been measured, and 3 w near field beam quality measured in experiments is compared with that simulated and calculated. Especially, the errors produced in simulation and calculation of near field beam quality for highintensity THG are investigated. By analyzing major factors not being considered that affect 3w near field beam quality in simulation and calculation, it is suggested that the simulating code be improved. Indispensable methods are discussed to improve 3w near field beam quality. The article is of reference value for further study on theories and experiments．
1w and 3 w near field beam quality for highintensity THG have been measured, and 3 w near field beam quality measured in experiments is compared with that simulated and calculated. Especially, the errors produced in simulation and calculation of near field beam quality for highintensity THG are investigated. By analyzing major factors not being considered that affect 3w near field beam quality in simulation and calculation, it is suggested that the simulating code be improved. Indispensable methods are discussed to improve 3w near field beam quality. The article is of reference value for further study on theories and experiments．
2002,
14.
Abstract:
A nonlinear evolution equation for the radiation field in magnetically insulated transmission line oscillator (MILO) is derived and the threshold conditions of the nonlinear unstable solution are studied. The results show: (1) The instability will arise when the ratio of the nonlinear growth rate to the linear growth rate is lower than 1.2 even if the detuning is arbitrarily slight. (2) If the value of g and γ (the ratio of the nonlinear growth rate to the linear growth rate for the phase) is far from g+γ=1, the instability arises easily because of the critical value of detuning becoming smaller and the critical value of linear growth rate becoming larger. (3) For the larger linear growth rate, the instability solution is relatively difficult.
A nonlinear evolution equation for the radiation field in magnetically insulated transmission line oscillator (MILO) is derived and the threshold conditions of the nonlinear unstable solution are studied. The results show: (1) The instability will arise when the ratio of the nonlinear growth rate to the linear growth rate is lower than 1.2 even if the detuning is arbitrarily slight. (2) If the value of g and γ (the ratio of the nonlinear growth rate to the linear growth rate for the phase) is far from g+γ=1, the instability arises easily because of the critical value of detuning becoming smaller and the critical value of linear growth rate becoming larger. (3) For the larger linear growth rate, the instability solution is relatively difficult.
2002,
14.
Abstract:
When an electron beam is injected into plasma, an ionchannel might form if the beam density is relatively high. A dispersion equation of a circular cylindrical waveguide with the ionchannel taken into account is given in this paper. The properties of dispersion and wave growth rates have also been discussed for two cases, one is that the ionchannel was taken into account, and the other is that the ionchannel was neglected.
When an electron beam is injected into plasma, an ionchannel might form if the beam density is relatively high. A dispersion equation of a circular cylindrical waveguide with the ionchannel taken into account is given in this paper. The properties of dispersion and wave growth rates have also been discussed for two cases, one is that the ionchannel was taken into account, and the other is that the ionchannel was neglected.
2002,
14.
Abstract:
Based on the mode coupling theory, this paper analyzes the critical angle of the TE01—TM11 mode converter completely by traditional waveguide axis constant curvature. Energy converted from TE01 to TM11 mode by all under the critical angle with multimode factor is got. The actual optimum angle of energy complete conversion is in the neighborhood of critical angle, and conversion efficiency is related to the curvature of bent waveguide.
Based on the mode coupling theory, this paper analyzes the critical angle of the TE01—TM11 mode converter completely by traditional waveguide axis constant curvature. Energy converted from TE01 to TM11 mode by all under the critical angle with multimode factor is got. The actual optimum angle of energy complete conversion is in the neighborhood of critical angle, and conversion efficiency is related to the curvature of bent waveguide.
2002,
14.
Abstract:
In photocathode RF gun, the Schottky effect in process of photoemission and electron lognitudinal accelerating process bring forth a linear work range in which electron charge out of gun is linear proportion to laser injection phase . According to the result ,we develop a method that can be used to measure time jitter between laser pulse and RF wave. The method can attain to high precision and small error. On general photoinjector condition, the precision is almost 1.15fs，the error is almost 0.23fs.
In photocathode RF gun, the Schottky effect in process of photoemission and electron lognitudinal accelerating process bring forth a linear work range in which electron charge out of gun is linear proportion to laser injection phase . According to the result ,we develop a method that can be used to measure time jitter between laser pulse and RF wave. The method can attain to high precision and small error. On general photoinjector condition, the precision is almost 1.15fs，the error is almost 0.23fs.
2002,
14.
Abstract:
The feasibility of propagating annular IREB in periodic permanent magnetic (PPM) field is studied. The PPM field is calculated first using the finite element magnetic method (FEMM). Then forces acting on IREB’s electron in such magnetic field are analyzed by fluid model and the radial force equation in modified Mathieu function form is drawn. Finally a 2.5D particle incell (PIC) simulation code is used to investigate the physical process of the IREB’s propagation. It is found that the stable propagation for IREB is relative to not only the beam plasma density and it’s equilibrium position but also the magnetic field intensity and it’s space period length. The conclusion is drawn that s
The feasibility of propagating annular IREB in periodic permanent magnetic (PPM) field is studied. The PPM field is calculated first using the finite element magnetic method (FEMM). Then forces acting on IREB’s electron in such magnetic field are analyzed by fluid model and the radial force equation in modified Mathieu function form is drawn. Finally a 2.5D particle incell (PIC) simulation code is used to investigate the physical process of the IREB’s propagation. It is found that the stable propagation for IREB is relative to not only the beam plasma density and it’s equilibrium position but also the magnetic field intensity and it’s space period length. The conclusion is drawn that s
2002,
14.
Abstract:
A particle�incell (PIC) code is used to simulate the physical mechanism and interaction process of the relativistic backward wave oscillator (RBWO) filled with neutral gas. The simulation results reveal the production process of the plasma due to the collision of the relativistic electron beam (REB) with the neutral gas injected previously into the BWO tube. It is well known that the collision produced plasma may efficiently neutralize the space charge effect of the REB and enhance the production rate of the high power microwave. Our simulation results verify the above conclusion. It is shown that the increasing of the neutral gas density makes the output frequency obviously upper shift and the output power and energy conversion efficiency in the RBWO filled with neutral gas are higher
A particle�incell (PIC) code is used to simulate the physical mechanism and interaction process of the relativistic backward wave oscillator (RBWO) filled with neutral gas. The simulation results reveal the production process of the plasma due to the collision of the relativistic electron beam (REB) with the neutral gas injected previously into the BWO tube. It is well known that the collision produced plasma may efficiently neutralize the space charge effect of the REB and enhance the production rate of the high power microwave. Our simulation results verify the above conclusion. It is shown that the increasing of the neutral gas density makes the output frequency obviously upper shift and the output power and energy conversion efficiency in the RBWO filled with neutral gas are higher
2002,
14.
Abstract:
The angular multipexing system is the chief part in the MOPA. It links the mainoscillator, preamplifier and main amplifier up together, and acts as a laser pulse wide compressor. The angular multipexing system can make full use of the electron energy in the cavity of preamplifier and main amplifier and the electron pulse width to amplify mainoscillator laser pulse in order to improve the power density on the target.The configuration of the angular multipexing system of the MOPA used in HeavenI is introduced in this article. Some advices are given to make an optimization based on the its performance in these year．
The angular multipexing system is the chief part in the MOPA. It links the mainoscillator, preamplifier and main amplifier up together, and acts as a laser pulse wide compressor. The angular multipexing system can make full use of the electron energy in the cavity of preamplifier and main amplifier and the electron pulse width to amplify mainoscillator laser pulse in order to improve the power density on the target.The configuration of the angular multipexing system of the MOPA used in HeavenI is introduced in this article. Some advices are given to make an optimization based on the its performance in these year．
2002,
14.
Abstract:
The soft aperture slots and multi spatial filters had been used to transmit the same phase of laser beams, the characters measurement system of 4×2×3 multislabamplifier design has been optimized by a program of Fresnel, where the sizes of pinholes of spatial filters which influence laser propagation have been analized here, the design optimization result also discussed, and the methods and results obtained in this paper are applicable to the design of high power solid laser amplifier system.
The soft aperture slots and multi spatial filters had been used to transmit the same phase of laser beams, the characters measurement system of 4×2×3 multislabamplifier design has been optimized by a program of Fresnel, where the sizes of pinholes of spatial filters which influence laser propagation have been analized here, the design optimization result also discussed, and the methods and results obtained in this paper are applicable to the design of high power solid laser amplifier system.
2002,
14.
Abstract:
This paper presents how to recognize targets under complicated background of cloud in sky by stimulating optical correlation. Some factors influencing recognition are calculated, such as changes of background intensity, edge detection of input image or matched filter and so on. Simulation results show that targets can be found in weaker background by direct optical correlation of input image and its matched filter without edge detection. When background becomes stronger, edge detection of input image is the key to improve target recognition capacity, but it weakens the intensity of correlative peak.
This paper presents how to recognize targets under complicated background of cloud in sky by stimulating optical correlation. Some factors influencing recognition are calculated, such as changes of background intensity, edge detection of input image or matched filter and so on. Simulation results show that targets can be found in weaker background by direct optical correlation of input image and its matched filter without edge detection. When background becomes stronger, edge detection of input image is the key to improve target recognition capacity, but it weakens the intensity of correlative peak.
2002,
14.
Abstract:
In the numerical simulation of 3D amplified spontaneous emission(ASE), we have investigated the effects of side reflection of ASE and the spectrum line shapes (Gaussian, Lorentzion and Square hat forms) of KrF spontaneous emission, including the influence of space grids in calculation. The ranges that ASE can affect the amplification quality of the Heaven 1 preamplifier are gotten. We have found that the ASE effects of square hat pulse can be twice of that of Lorentzion pulse, and the extraction efficiency will be decreased about 40%. From our calculation, we learn that the efficiency can decline to about 35% if we include the influence of ASE with square hat pulse and reflection coefficient of 0.2, in contrasting with the situation which not considering the ASE effects.
In the numerical simulation of 3D amplified spontaneous emission(ASE), we have investigated the effects of side reflection of ASE and the spectrum line shapes (Gaussian, Lorentzion and Square hat forms) of KrF spontaneous emission, including the influence of space grids in calculation. The ranges that ASE can affect the amplification quality of the Heaven 1 preamplifier are gotten. We have found that the ASE effects of square hat pulse can be twice of that of Lorentzion pulse, and the extraction efficiency will be decreased about 40%. From our calculation, we learn that the efficiency can decline to about 35% if we include the influence of ASE with square hat pulse and reflection coefficient of 0.2, in contrasting with the situation which not considering the ASE effects.
2002,
14.
Abstract:
In this paper, the kinetics of XeF(C-A) laser were presented. The structures of the surface discharge optically pumping source and the laser devices were introduced. Experimental study and numerical simulation of XeF(CA) laser, as well as the detection of the density of XeF2 were summarized. The development of the radiative source technology was described. The energy deposition efficiency over 80% has been obtained on a module of impacted sectioned surface discharge source and the average deposit power density is about 27MW/cm. The framing photographs of discharge plasma channel under different conditions have been obtained. For multichannel discharge source, the symmetrical synchronous discharge and the photodissociation waves have been obtained.
In this paper, the kinetics of XeF(C-A) laser were presented. The structures of the surface discharge optically pumping source and the laser devices were introduced. Experimental study and numerical simulation of XeF(CA) laser, as well as the detection of the density of XeF2 were summarized. The development of the radiative source technology was described. The energy deposition efficiency over 80% has been obtained on a module of impacted sectioned surface discharge source and the average deposit power density is about 27MW/cm. The framing photographs of discharge plasma channel under different conditions have been obtained. For multichannel discharge source, the symmetrical synchronous discharge and the photodissociation waves have been obtained.
2002,
14.
Abstract:
The freevortex aerodynamic window(FADW) can take the place of the conventional crystal output window sealing the lower pressure laser cavity of high energy lasers effectively. But the supersonic flow of the FADW will introduce some deformation to the output high power laser beam so it is necessary to compensate the disturbed laser beam using the adaptive optical system. This paper studies the compensation of the wavefront deformation of the FADW under the ideal designing situation using the 37 subapertures indoor adaptive optical system.It discusses the principle of the adaptive optical system and gives the experimental method and compensaton results. The results show that this 37 subapertures indoor adaptive optical system can compensate the wavefront deformation of the FADW under the des
The freevortex aerodynamic window(FADW) can take the place of the conventional crystal output window sealing the lower pressure laser cavity of high energy lasers effectively. But the supersonic flow of the FADW will introduce some deformation to the output high power laser beam so it is necessary to compensate the disturbed laser beam using the adaptive optical system. This paper studies the compensation of the wavefront deformation of the FADW under the ideal designing situation using the 37 subapertures indoor adaptive optical system.It discusses the principle of the adaptive optical system and gives the experimental method and compensaton results. The results show that this 37 subapertures indoor adaptive optical system can compensate the wavefront deformation of the FADW under the des
2002,
14.
Abstract:
In this paper, the atmospheric transmittances, the attenuation coefficient and the absorption coefficient of spectrum lines 20P4 and 20P5 of HF overtone laser are studied. The attenuation coefficient of 20P4 is 0.26～0.27km-1，and that of 20P5 is 2.24～2.28km-1. The absorption coefficient of 20P5 is 20 times bigger than that of 20P4. Simple theoretical analysis indicates that line 20P4 is the optimum line in selecting lines of HF overtone laser.
In this paper, the atmospheric transmittances, the attenuation coefficient and the absorption coefficient of spectrum lines 20P4 and 20P5 of HF overtone laser are studied. The attenuation coefficient of 20P4 is 0.26～0.27km-1，and that of 20P5 is 2.24～2.28km-1. The absorption coefficient of 20P5 is 20 times bigger than that of 20P4. Simple theoretical analysis indicates that line 20P4 is the optimum line in selecting lines of HF overtone laser.
2002,
14.
Abstract:
Experimental investigations were performed for amplification of ultrashort pulse laser with HeavenI ebeam pumped KrF amplifier in CIAE. A 50mJ, 420fs UV ultrashort pulse was amplified to 2-3J energy, 1.2ps pulse duration, and 2TW laser power. Experimental technique such as synchronization were describe, some parameters such as nonlinear absorb coefficient were measured in experiment. As a result, it is possible to achieve ultrastrong UV laser wih intensity higher than 1019W/cm2 in recently years．
Experimental investigations were performed for amplification of ultrashort pulse laser with HeavenI ebeam pumped KrF amplifier in CIAE. A 50mJ, 420fs UV ultrashort pulse was amplified to 2-3J energy, 1.2ps pulse duration, and 2TW laser power. Experimental technique such as synchronization were describe, some parameters such as nonlinear absorb coefficient were measured in experiment. As a result, it is possible to achieve ultrastrong UV laser wih intensity higher than 1019W/cm2 in recently years．
2002,
14.
Abstract:
The matrix decomposition and equivalent transformation of nonsymmetrical optical systems are studied by using matrix method in optics. The method introduced by Arsenault is extended to decomposing a 4×4 matrix, the determinant of the corresponding block matrix is zero.The decomposition of symmetrization optical systems is performed to illustrate the application of the method.
The matrix decomposition and equivalent transformation of nonsymmetrical optical systems are studied by using matrix method in optics. The method introduced by Arsenault is extended to decomposing a 4×4 matrix, the determinant of the corresponding block matrix is zero.The decomposition of symmetrization optical systems is performed to illustrate the application of the method.
2002,
14.
Abstract:
The film structure determined temperature and standing wave field's characters which formed in laser irradiated optical thin film is presented, the temperature and standing wave fields is calculated for IR filter as an example. The research on damage characters in laser irradiated IR filter is proposed with 1.06μm Qswitched Nd:YAG laser with pulse duration of 10ns and spot diameter of 0.61mm. From the analysis to the laser damaged IR filter, it is discovered that the initial filter damage did occurr in the inner layer, thus the experiment validated the calculated result of temperature and standing wave fields existed in filter. It is valuable to improve the IR filter's hardness against laser.
The film structure determined temperature and standing wave field's characters which formed in laser irradiated optical thin film is presented, the temperature and standing wave fields is calculated for IR filter as an example. The research on damage characters in laser irradiated IR filter is proposed with 1.06μm Qswitched Nd:YAG laser with pulse duration of 10ns and spot diameter of 0.61mm. From the analysis to the laser damaged IR filter, it is discovered that the initial filter damage did occurr in the inner layer, thus the experiment validated the calculated result of temperature and standing wave fields existed in filter. It is valuable to improve the IR filter's hardness against laser.
2002,
14.
Abstract:
Pulsed lasers of two different durations (30 ns, 500 fs) are used to deposit Hydrogenfree Diamond Like Carbon (DLC) films over large areas. Analysis of DLC films shows remarkable mechanical, optical, electrical, and chemical properties that are close to those of diamond. By optical emission spectroscopy and ion probe, the effects of plasma characteristic on DLC film are on experimentally studied. Amorphous silicon films deposited by PLD are also experimentally studied．
Pulsed lasers of two different durations (30 ns, 500 fs) are used to deposit Hydrogenfree Diamond Like Carbon (DLC) films over large areas. Analysis of DLC films shows remarkable mechanical, optical, electrical, and chemical properties that are close to those of diamond. By optical emission spectroscopy and ion probe, the effects of plasma characteristic on DLC film are on experimentally studied. Amorphous silicon films deposited by PLD are also experimentally studied．
2002,
14.
Abstract:
The method using diaphragm to change the mode volume ratio between the forward and the reverse mode to suppress the reverse mode in the symmetric confocal ring resonators is presented. And the different effects of the reverse mode suppression for positive and negative branch are described by the theoretical analyses, respectively.
The method using diaphragm to change the mode volume ratio between the forward and the reverse mode to suppress the reverse mode in the symmetric confocal ring resonators is presented. And the different effects of the reverse mode suppression for positive and negative branch are described by the theoretical analyses, respectively.
2002,
14.
Abstract:
By using the secondorder moments method and generalized HuygensFresnel diffraction integral, the optical system used for symmetrizing Hermite Gaussian beams with real argument is applied to study the transformation of astigmatic HermiteGaussian beams with complex argument. It is shown that the secondorder matrix of HermiteGaussian beams with complex argument passing through this system can be symmetrized．However， the spot shape of the beams has not a rotational symmetry . Therefore, such type of symmetrization system for beams with real argument is not suitable for beams with complex argument.
By using the secondorder moments method and generalized HuygensFresnel diffraction integral, the optical system used for symmetrizing Hermite Gaussian beams with real argument is applied to study the transformation of astigmatic HermiteGaussian beams with complex argument. It is shown that the secondorder matrix of HermiteGaussian beams with complex argument passing through this system can be symmetrized．However， the spot shape of the beams has not a rotational symmetry . Therefore, such type of symmetrization system for beams with real argument is not suitable for beams with complex argument.
2002,
14.
Abstract:
A thermoplastic, the MeltMount 1.704 doped with carbon as an index matching material is used to suppress the transverse parasitic lasing in a 8cm Ti: sapphire laser amplifier disk. It increases the oscillation threshold from 13 to 2100 theoretically. The practical procedure of applying the material to the crystal is described. This will help in the realization of the first petawatt Ti: sapphire laser system in the world.
A thermoplastic, the MeltMount 1.704 doped with carbon as an index matching material is used to suppress the transverse parasitic lasing in a 8cm Ti: sapphire laser amplifier disk. It increases the oscillation threshold from 13 to 2100 theoretically. The practical procedure of applying the material to the crystal is described. This will help in the realization of the first petawatt Ti: sapphire laser system in the world.
