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RSS2004 Vol. 16, No. 09
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2004,
16.
Abstract:
The model for simulating the laser beam propagation through the beam path indoor was described. Because no heat removal occurs by forced convection in the beam path, thermal conduction and natural convection dominate. The results show that the thermal effect produced by the high energy laser in the beam path can distort the beam and affect the beam quality. Because of the thermal effect in the beam path, with 10kW laser power, the radius of encircled energy is 3.1 times that of no the thermal effect, and the Strehl ratio falls 60%.
The model for simulating the laser beam propagation through the beam path indoor was described. Because no heat removal occurs by forced convection in the beam path, thermal conduction and natural convection dominate. The results show that the thermal effect produced by the high energy laser in the beam path can distort the beam and affect the beam quality. Because of the thermal effect in the beam path, with 10kW laser power, the radius of encircled energy is 3.1 times that of no the thermal effect, and the Strehl ratio falls 60%.
2004,
16.
Abstract:
Taking account of spatial dependence in the propagation direction of focused laser beams, the SBS process in fused silica glass is simulated numerically. The dependence of pump energy on SBS reflectivity is presented, which shows good agreement with Yoshida's experiment results. The "focused spike" in scattering pulse is observed theoretically and the influence of SBS on optical damage, under focusing condition, is discussed. The simulation shows that under the condition of focal pumping the presence of SBS would strongly limit the amplitude of stress induced by single longitudinal laser.
Taking account of spatial dependence in the propagation direction of focused laser beams, the SBS process in fused silica glass is simulated numerically. The dependence of pump energy on SBS reflectivity is presented, which shows good agreement with Yoshida's experiment results. The "focused spike" in scattering pulse is observed theoretically and the influence of SBS on optical damage, under focusing condition, is discussed. The simulation shows that under the condition of focal pumping the presence of SBS would strongly limit the amplitude of stress induced by single longitudinal laser.
2004,
16.
Abstract:
By a HartmannShack sensor with 37 lenslets at 419Hz , the aerooptical characteristics of a heated air flow were measured. Using modal Zernike reconstructor, a series of dynamic optical path difference (OPD) distribution were obtained, and then Strehl ratioes were calculated. The test gives the results with different flow parameters : mean center flow velocity from 43m/s to 8 m/s and temperature from 44℃ to 85℃ . And the velocities of vortical structures were calculated by correlation analysis. The results show the OPD distribution educed by coherent structure in shear layer changes with flow parameters. When the temperature is more than 65℃,its influence on strehl ratio is not obvious.
By a HartmannShack sensor with 37 lenslets at 419Hz , the aerooptical characteristics of a heated air flow were measured. Using modal Zernike reconstructor, a series of dynamic optical path difference (OPD) distribution were obtained, and then Strehl ratioes were calculated. The test gives the results with different flow parameters : mean center flow velocity from 43m/s to 8 m/s and temperature from 44℃ to 85℃ . And the velocities of vortical structures were calculated by correlation analysis. The results show the OPD distribution educed by coherent structure in shear layer changes with flow parameters. When the temperature is more than 65℃,its influence on strehl ratio is not obvious.
2004,
16.
Abstract:
A diodepumped Nd:YAG disk laser with high efficiency is reported. A fourpass optical coupling system is well design to obtain a nearly flat top pump profile. An average output power of 101 W is achieved from one single disk with a thickness of 1mm. The average pumping power of the diode laser array is 252W with an electrical to optical efficiency of more than 45%. The optical efficiency of the laser system is 40% and the electrical to optical efficiency is more than 18%.
A diodepumped Nd:YAG disk laser with high efficiency is reported. A fourpass optical coupling system is well design to obtain a nearly flat top pump profile. An average output power of 101 W is achieved from one single disk with a thickness of 1mm. The average pumping power of the diode laser array is 252W with an electrical to optical efficiency of more than 45%. The optical efficiency of the laser system is 40% and the electrical to optical efficiency is more than 18%.
2004,
16.
Abstract:
Couple-mode analysis can describe the output field of the phase-locked diodelaser arrays (DLA) in an external cavity. The eigenvalue equation for a phase-locked DLA has been deduced, the corresponding eigenvalues and eigenvectors have been get analytically. Furthermore, the near-field distributions and the farfield patterns are presented for various supermode, when the elements influence are individually taken into account．
Couple-mode analysis can describe the output field of the phase-locked diodelaser arrays (DLA) in an external cavity. The eigenvalue equation for a phase-locked DLA has been deduced, the corresponding eigenvalues and eigenvectors have been get analytically. Furthermore, the near-field distributions and the farfield patterns are presented for various supermode, when the elements influence are individually taken into account．
2004,
16.
Abstract:
Experimental of singlet delta oxygen generation by RF discharge under conditions of using pure oxygen and its mixtures with argon were studied. It was discussed in detail the dependence of singlet delta oxygen yield on oxygen flow rate, the ratio of oxygen over argon and gas pressure. The experimental results show that singlet delta oxygen yield decreases with gas pressure increases. The experimental conditions were: the radio frequency was 13.56MHz, the RF power was up to 500W, the oxygen partial pressure was 133.0~399.0Pa, the flow rate of oxygen and argon was 0～1.4mmol/s and 0～2.1mmol/s, respectively. Singlet delta oxygen yield up to 17.5% was achieved．
Experimental of singlet delta oxygen generation by RF discharge under conditions of using pure oxygen and its mixtures with argon were studied. It was discussed in detail the dependence of singlet delta oxygen yield on oxygen flow rate, the ratio of oxygen over argon and gas pressure. The experimental results show that singlet delta oxygen yield decreases with gas pressure increases. The experimental conditions were: the radio frequency was 13.56MHz, the RF power was up to 500W, the oxygen partial pressure was 133.0~399.0Pa, the flow rate of oxygen and argon was 0～1.4mmol/s and 0～2.1mmol/s, respectively. Singlet delta oxygen yield up to 17.5% was achieved．
2004,
16.
Abstract:
A theoretical model of dynamicequilibrium iodine supply system was built. An iodine supply system for COIL based upon that model was designed, which has only 1/8 volume, 1/3 weight, and takes half the time to preheat as the conventional staticcapacity iodine supply system does. Experimental results show that the stability of the system is reliable, especially for a long operation; and iodine flow rate can be conveniently adjusted in a wide range. With these merits, it meets the need of experimental optimization of iodine flowrate for COIL.
A theoretical model of dynamicequilibrium iodine supply system was built. An iodine supply system for COIL based upon that model was designed, which has only 1/8 volume, 1/3 weight, and takes half the time to preheat as the conventional staticcapacity iodine supply system does. Experimental results show that the stability of the system is reliable, especially for a long operation; and iodine flow rate can be conveniently adjusted in a wide range. With these merits, it meets the need of experimental optimization of iodine flowrate for COIL.
2004,
16.
Abstract:
The soft X-ray laser Mach-Zehnder interferometer is an important tool to measure the electron densities of a laser-produced plasma near the critical surface. The design of a multilayer beam splitter at 13.9nm for soft X-ray laser Mach-Zehnder interferometer is completed based on the standard of maximizing product of reflectivity and transmission of the beam splitter. The beam splitters which is Mo/Si multilayers on 10mm×10mm area Si-3N-4 membrane are fabricated using the magnetron sputtering. The figure error of the beam splitter has reached the deep nanometer magnitude by using optical profiler and the product of reflectivity and transmission measured by synchrotron radiation is up to 4%．
The soft X-ray laser Mach-Zehnder interferometer is an important tool to measure the electron densities of a laser-produced plasma near the critical surface. The design of a multilayer beam splitter at 13.9nm for soft X-ray laser Mach-Zehnder interferometer is completed based on the standard of maximizing product of reflectivity and transmission of the beam splitter. The beam splitters which is Mo/Si multilayers on 10mm×10mm area Si-3N-4 membrane are fabricated using the magnetron sputtering. The figure error of the beam splitter has reached the deep nanometer magnitude by using optical profiler and the product of reflectivity and transmission measured by synchrotron radiation is up to 4%．
2004,
16.
Abstract:
On the basis of analyzing low-light-level (LLL) TV imaging system, this paper presents conditions required and generation method of LLL scene digital image data suitable for LLL TV imaging system simulation. Focusing on the second generation proximity focusing system and the third generation imager intensifier system, energy gain theoretical model of LLL TV imaging system is derived. Then, main noise sources of the system are modeled by introducing 3D noise model. At last, the assessment method of the degression of image enhancement algorithm on image noise is proposed.Simulative results show that the high frequency information becomes blur after being transfered through the system, signal to noise ratio reduces because of introduction of noise，and image quality and contrast are greatly
On the basis of analyzing low-light-level (LLL) TV imaging system, this paper presents conditions required and generation method of LLL scene digital image data suitable for LLL TV imaging system simulation. Focusing on the second generation proximity focusing system and the third generation imager intensifier system, energy gain theoretical model of LLL TV imaging system is derived. Then, main noise sources of the system are modeled by introducing 3D noise model. At last, the assessment method of the degression of image enhancement algorithm on image noise is proposed.Simulative results show that the high frequency information becomes blur after being transfered through the system, signal to noise ratio reduces because of introduction of noise，and image quality and contrast are greatly
2004,
16.
Abstract:
A lamp pumped CW Nd:YAG laser is presented in this paper. The main factors, which affect output power and beam quality of high power solidstate laser module, are theoretically analyzed. It is included that improving the laser efficiency to decrease the stable range of the diopter( increasing the thermal focus), to decrease the product of beam parameter, and improving the beam quality of output laser. Total electrooptics efficiency of lamp pumped YAG crystal as high as 4% is attained, and output power is 647W with beam parameter product 22mm·mrad.
A lamp pumped CW Nd:YAG laser is presented in this paper. The main factors, which affect output power and beam quality of high power solidstate laser module, are theoretically analyzed. It is included that improving the laser efficiency to decrease the stable range of the diopter( increasing the thermal focus), to decrease the product of beam parameter, and improving the beam quality of output laser. Total electrooptics efficiency of lamp pumped YAG crystal as high as 4% is attained, and output power is 647W with beam parameter product 22mm·mrad.
2004,
16.
Abstract:
To measure the atmospheric optical turbulence, the microtemperature sensor is often used. But statistic average time can affect the measuring results of temperature structure constants. From analyzing the source data the average time can be set as 5~15 seconds. In the measuring period of microtemperature, the results will be erroneous when the environmental influence exists or the instrument state is not proper. Most of these situations can be found out from the source data analysis. One method of data differentiation was presented and discussed. First, error data was removed according to the experiment records. Second, if some data was abnormally large or small, the spectrum of source data of temperature difference was used to determine the facticity of data. These two steps could ens
To measure the atmospheric optical turbulence, the microtemperature sensor is often used. But statistic average time can affect the measuring results of temperature structure constants. From analyzing the source data the average time can be set as 5~15 seconds. In the measuring period of microtemperature, the results will be erroneous when the environmental influence exists or the instrument state is not proper. Most of these situations can be found out from the source data analysis. One method of data differentiation was presented and discussed. First, error data was removed according to the experiment records. Second, if some data was abnormally large or small, the spectrum of source data of temperature difference was used to determine the facticity of data. These two steps could ens
2004,
16.
Abstract:
Timeresolved measurement system of Xray spectroscopy was constructed by coupling a gated MCP with a flat crystal spectrometer, and the Kshell emission spectra from the corona of laserirradiated aluminum plasma, were measured with a time delay of about 1ns and with an exposure time of about 200ps. Using the approximation of steady collisionalradiative equilibrium model, the interstage line intensity ratios of the Kshell lines of aluminum were given as a function of electron temperature and density. The electron temperatures were deduced from the line intensity ratios. The diagnosed electron temperatures of the plasmas were 1.190(1±27%),1.165(1±27%), and 1.525(1±27%)keV respectively at laser intensity of 2.319×1014, 1.937×1014, and 3.946×1014W/cm2 。
Timeresolved measurement system of Xray spectroscopy was constructed by coupling a gated MCP with a flat crystal spectrometer, and the Kshell emission spectra from the corona of laserirradiated aluminum plasma, were measured with a time delay of about 1ns and with an exposure time of about 200ps. Using the approximation of steady collisionalradiative equilibrium model, the interstage line intensity ratios of the Kshell lines of aluminum were given as a function of electron temperature and density. The electron temperatures were deduced from the line intensity ratios. The diagnosed electron temperatures of the plasmas were 1.190(1±27%),1.165(1±27%), and 1.525(1±27%)keV respectively at laser intensity of 2.319×1014, 1.937×1014, and 3.946×1014W/cm2 。
2004,
16.
Abstract:
Measuring ICF neutron yield by Pb activation is performed in the target chamber, but calibrating the Pb detect system using an accelerator neutron source is not performed in the target chamber. The difference between the measuring environment and the calibrating environment will affect the measurement accuracy, for the neutrons scattered by the target chamber will contribute to the production of radionuclide 207mPb which emits detectable γ radiations.In this paper, by Monte Carlo method, the effect on the measurement accuracy has been calculated and the result is less than 1‰.This effect is defined as the ratio of the number of 207mPb(Ns) generated from the target chamberscattered neutron activation to the number of 207mPb(N) generated without target chamber existing. The target chambe
Measuring ICF neutron yield by Pb activation is performed in the target chamber, but calibrating the Pb detect system using an accelerator neutron source is not performed in the target chamber. The difference between the measuring environment and the calibrating environment will affect the measurement accuracy, for the neutrons scattered by the target chamber will contribute to the production of radionuclide 207mPb which emits detectable γ radiations.In this paper, by Monte Carlo method, the effect on the measurement accuracy has been calculated and the result is less than 1‰.This effect is defined as the ratio of the number of 207mPb(Ns) generated from the target chamberscattered neutron activation to the number of 207mPb(N) generated without target chamber existing. The target chambe
2004,
16.
Abstract:
A 10mm caliber twostage doublepass offaxis amplifying system was described, and the 5mm×5mm caliber laser pulse was amplified. The coupling system of high power LD array tightside directlypumping Nd:YLF rod was used. The characters of amplifying system and each amplification in different pump currents and input energy were analyzed by theory and experiment. In experiment when 1.58mJ energy was injected into the soft 5mm×5mm diaphragm, 129.2mJ energy was output, and energy extract efficiency was 19.5%.
A 10mm caliber twostage doublepass offaxis amplifying system was described, and the 5mm×5mm caliber laser pulse was amplified. The coupling system of high power LD array tightside directlypumping Nd:YLF rod was used. The characters of amplifying system and each amplification in different pump currents and input energy were analyzed by theory and experiment. In experiment when 1.58mJ energy was injected into the soft 5mm×5mm diaphragm, 129.2mJ energy was output, and energy extract efficiency was 19.5%.
2004,
16.
Abstract:
In this paper, the Xray radiograph technology, which is used for wallthickness measurement of multilayer plastic microsphere, is expounded in detail. The mechanism that Xray is absorbed by the material of plastic shell used as a highgain target in ICF is investigated theoretically. The theoretical analysis and experiment prove that, in vacuum environment, the Xray tube works under 10kV voltage and outputs Xray of 8keV energy, the best image of shell with good contrast and clear interface can be obtained. This technique offers a good measuring method to the shells making．
In this paper, the Xray radiograph technology, which is used for wallthickness measurement of multilayer plastic microsphere, is expounded in detail. The mechanism that Xray is absorbed by the material of plastic shell used as a highgain target in ICF is investigated theoretically. The theoretical analysis and experiment prove that, in vacuum environment, the Xray tube works under 10kV voltage and outputs Xray of 8keV energy, the best image of shell with good contrast and clear interface can be obtained. This technique offers a good measuring method to the shells making．
2004,
16.
Abstract:
Alignment accuracy of the cavity mirror in multipass amplifier is very high. Aiming at the requirements on alignment precision of cavity mirror in high power lasers, using image relaying of pinholes and the principle of beam automatic alignment, a scheme to align the cavity mirror is designed. It has been demonstrated on the simulation experiment system of the SGⅢ prototype facility. The main amplifier's adjustment can be finished in 15min. The centering precision of the system is less than 05% of the beam diameter. The pointing precision of the system are less than 0.3".
Alignment accuracy of the cavity mirror in multipass amplifier is very high. Aiming at the requirements on alignment precision of cavity mirror in high power lasers, using image relaying of pinholes and the principle of beam automatic alignment, a scheme to align the cavity mirror is designed. It has been demonstrated on the simulation experiment system of the SGⅢ prototype facility. The main amplifier's adjustment can be finished in 15min. The centering precision of the system is less than 05% of the beam diameter. The pointing precision of the system are less than 0.3".
2004,
16.
Abstract:
An analytical expression of diffraction efficiency of color separation grating (CSG) was deduced from the scalar diffraction theory and Fourier optics. Moreover, the relation between diffraction efficiency and phase delay was analyzed. If the phasedelays brought by different parts of CSG meet corresponding conditions, the incident wave will be diffracted into one of the three central diffraction orders with highest efficiency. In addition, some errors, including etched depth error and duty cycle error, induced by two different fabricating processes were analyzed and compared. In ICF studies, CSG, which are fabricated by the two processes, have the same fluctuation range in diffraction efficiency for the third harmonic when tolerated etched errors are the same. Duty cycle errors can bring
An analytical expression of diffraction efficiency of color separation grating (CSG) was deduced from the scalar diffraction theory and Fourier optics. Moreover, the relation between diffraction efficiency and phase delay was analyzed. If the phasedelays brought by different parts of CSG meet corresponding conditions, the incident wave will be diffracted into one of the three central diffraction orders with highest efficiency. In addition, some errors, including etched depth error and duty cycle error, induced by two different fabricating processes were analyzed and compared. In ICF studies, CSG, which are fabricated by the two processes, have the same fluctuation range in diffraction efficiency for the third harmonic when tolerated etched errors are the same. Duty cycle errors can bring
2004,
16.
Abstract:
The improved confinement phase was observed during modulating toroidal current on the Hefei superconducting Tokamak7 (HT7 ). This improved plasma confinement phase is characterized by suppressing magnetohydrodynamic (MHD) instabilities effectively thus increased the central line averaged electron density and the central electron temperature about 33%, output steeper density profiles, and reduced hydrogen radiation from the edge as well. The global energy confinement time was increased by 27%~45%; The impurity radiation was reduced by modulation of plasma toroidal current; Particle confinement time was increased about two times; A more strong radial negative electric field formed inside the limiter. The radial electric field during modulating current was calculated and disscussed.
The improved confinement phase was observed during modulating toroidal current on the Hefei superconducting Tokamak7 (HT7 ). This improved plasma confinement phase is characterized by suppressing magnetohydrodynamic (MHD) instabilities effectively thus increased the central line averaged electron density and the central electron temperature about 33%, output steeper density profiles, and reduced hydrogen radiation from the edge as well. The global energy confinement time was increased by 27%~45%; The impurity radiation was reduced by modulation of plasma toroidal current; Particle confinement time was increased about two times; A more strong radial negative electric field formed inside the limiter. The radial electric field during modulating current was calculated and disscussed.
2004,
16.
Abstract:
In order to study the probability of high gain soft Xray laser in 3p3s transition of electron collisional excitation in neonlike ions of argon , a simulation of gas puff column with initial density 6.632×10－3g/cm3 irradiating by 1.5ps double pulses with a 1.2ns separation is presented. The results show that a wide region in which the abundance of the neonlike ion is more than 50% and the free electron density is more than 1020cm－3 is obtained. The short main pulse rapidly heats electrons to a temperature of higher than 1keV, and a high gain region is produced by collision of high density free electrons with Nelike argon ions .The gain region occurs about at a time scale of duration of pumping laser pulse, and its width is more than 100μm. The gain coefficient is 200~300cm－1.
In order to study the probability of high gain soft Xray laser in 3p3s transition of electron collisional excitation in neonlike ions of argon , a simulation of gas puff column with initial density 6.632×10－3g/cm3 irradiating by 1.5ps double pulses with a 1.2ns separation is presented. The results show that a wide region in which the abundance of the neonlike ion is more than 50% and the free electron density is more than 1020cm－3 is obtained. The short main pulse rapidly heats electrons to a temperature of higher than 1keV, and a high gain region is produced by collision of high density free electrons with Nelike argon ions .The gain region occurs about at a time scale of duration of pumping laser pulse, and its width is more than 100μm. The gain coefficient is 200~300cm－1.
2004,
16.
Abstract:
This paper describes the principle of plasma electrooptical switch driving system. The system use plasma electrooptical switch system in high power ICF drivers based on large aperture size (for example, 300mm×300mm) multipass amplifier array scheme. The systems can product strict sequential correlated five highvoltage strongcurrent pulses. These pulses are loaded on longitudinal Pockels cell full of inert gas through three coaxial cables. As the electrooptical switch with plasma electrodes has unique advantage of high efficient, fast for on/off, high precision, large aperture size and high laser damage threshold, it has become an ideal switch system in new generation of ultrahigh power laser system.
This paper describes the principle of plasma electrooptical switch driving system. The system use plasma electrooptical switch system in high power ICF drivers based on large aperture size (for example, 300mm×300mm) multipass amplifier array scheme. The systems can product strict sequential correlated five highvoltage strongcurrent pulses. These pulses are loaded on longitudinal Pockels cell full of inert gas through three coaxial cables. As the electrooptical switch with plasma electrodes has unique advantage of high efficient, fast for on/off, high precision, large aperture size and high laser damage threshold, it has become an ideal switch system in new generation of ultrahigh power laser system.
2004,
16.
Abstract:
The high power Ubitron amplifier with coaxial waveguide is researched using the nonlinear theory in three dimensions. The Ubitron amplifier utilizes an annular electron beam interacting with TE01 mode in a coaxial waveguide. By numerical simulations, the output power of 2.24MW with 10.9% efficiency and 35％ bandwidth in Kuband is gained. The results show that the selffields of the electron beam tend to reduce saturation power, narrow the bandwidth and lower gain. So the effects of selffields should be considered in designing the Ubitron amplifier. Using wiggler taper, the efficiency is up to 12.3%.
The high power Ubitron amplifier with coaxial waveguide is researched using the nonlinear theory in three dimensions. The Ubitron amplifier utilizes an annular electron beam interacting with TE01 mode in a coaxial waveguide. By numerical simulations, the output power of 2.24MW with 10.9% efficiency and 35％ bandwidth in Kuband is gained. The results show that the selffields of the electron beam tend to reduce saturation power, narrow the bandwidth and lower gain. So the effects of selffields should be considered in designing the Ubitron amplifier. Using wiggler taper, the efficiency is up to 12.3%.
2004,
16.
Abstract:
In this paper, the quasiperiodic boundary conditions in the computer code MAFIA was used to determine the effect on dispersion and onaxis interaction impedance of helical slowwave structure. The Finite Element Method softwareANSYS was used to simulate the helix pressed distortion. And then the effect of pressed helix in helical slowwave structure on TWT coldtest characteristics was analysed in detail. The results show that both dispersion and onaxis interaction impedance of helical slowwave structure increase due to helix deformation generally, when the radial relative deformation is less than 1%.While radial relative deformation is more than 1%, the onaxis interaction impedance will decrease.
In this paper, the quasiperiodic boundary conditions in the computer code MAFIA was used to determine the effect on dispersion and onaxis interaction impedance of helical slowwave structure. The Finite Element Method softwareANSYS was used to simulate the helix pressed distortion. And then the effect of pressed helix in helical slowwave structure on TWT coldtest characteristics was analysed in detail. The results show that both dispersion and onaxis interaction impedance of helical slowwave structure increase due to helix deformation generally, when the radial relative deformation is less than 1%.While radial relative deformation is more than 1%, the onaxis interaction impedance will decrease.
2004,
16.
Abstract:
The intense field of high power microwave causes ionization of neutral particle in atmosphere and the plasma comes into being. The ionization frequency of neutral particle relates to electric field intensity and atmospheric pressure. This paper presents the interaction between electron and air neutral molecules in comparatively wide region. When an impulse of high power microwave is propagated, the variation of electron concentration and refractive index accompanying with that of effective electric-field also intensity is also introduced．
The intense field of high power microwave causes ionization of neutral particle in atmosphere and the plasma comes into being. The ionization frequency of neutral particle relates to electric field intensity and atmospheric pressure. This paper presents the interaction between electron and air neutral molecules in comparatively wide region. When an impulse of high power microwave is propagated, the variation of electron concentration and refractive index accompanying with that of effective electric-field also intensity is also introduced．
2004,
16.
Abstract:
In this paper, the mechanism of microwave generation in vircator is studied analytically, the formula of the small signal gain and the scaling law of the saturated power are given. The conclusion is that the coherent radiation in vircator is generated by the modulated electron current reflected from the virtual cathode. When the injection current is slightly larger than the first critical current, there is the highest radiation gain region, but the reflective current is smaller; when the injection current is slightly larger than the second critical current, there is a high radiation gain region, the reflective current is large too.
In this paper, the mechanism of microwave generation in vircator is studied analytically, the formula of the small signal gain and the scaling law of the saturated power are given. The conclusion is that the coherent radiation in vircator is generated by the modulated electron current reflected from the virtual cathode. When the injection current is slightly larger than the first critical current, there is the highest radiation gain region, but the reflective current is smaller; when the injection current is slightly larger than the second critical current, there is a high radiation gain region, the reflective current is large too.
2004,
16.
Abstract:
Taking the advantages of neural network control method for nonlinear complex systems, control of beam halo-chaos in the periodic focusing channels of high intensity accelerators is studied by feed-forward back-propagating neural network selfadaptation method. The envelope radius of highintensity proton beam can reach the matched beam radius by selecting suitable control structure of neural network and the linear feedback coefficient, and adjusting the right-coefficient of neural network. The beam halochaos is obviously suppressed and amplitude shake is largely reduced when the neural network self-adaptation control is applied．
Taking the advantages of neural network control method for nonlinear complex systems, control of beam halo-chaos in the periodic focusing channels of high intensity accelerators is studied by feed-forward back-propagating neural network selfadaptation method. The envelope radius of highintensity proton beam can reach the matched beam radius by selecting suitable control structure of neural network and the linear feedback coefficient, and adjusting the right-coefficient of neural network. The beam halochaos is obviously suppressed and amplitude shake is largely reduced when the neural network self-adaptation control is applied．
2004,
16.
Abstract:
An introduction was given to beam profile monitoring system based on image acquisition facilities using fluorescent target. The method of data processing and image intensification was emphasized in the paper. On the bases of this research, a software system was designed to realize image data acquisition, data processing and realtime measuring of ion beam parameters. The software system has good reliability, visual display and friendly interface.
An introduction was given to beam profile monitoring system based on image acquisition facilities using fluorescent target. The method of data processing and image intensification was emphasized in the paper. On the bases of this research, a software system was designed to realize image data acquisition, data processing and realtime measuring of ion beam parameters. The software system has good reliability, visual display and friendly interface.
2004,
16.
Abstract:
This paper presents the magnetic field parametric selfadaptive method for controlling the beamhalochaos in the periodfocusing channel. The method is applied to the multiparticle model with the periodfocusing magnetic field channel. The PIC simulation results show that beam halochaos for four different kinds of initial proton beams can be controlled effectively, respectively. The beam halos and its regeneration can be eliminated. This method is easy to realize in experiment .The research offers a valuable reference for the design of the periodic focusing channels in the highcurrent linear proton accelerators．
This paper presents the magnetic field parametric selfadaptive method for controlling the beamhalochaos in the periodfocusing channel. The method is applied to the multiparticle model with the periodfocusing magnetic field channel. The PIC simulation results show that beam halochaos for four different kinds of initial proton beams can be controlled effectively, respectively. The beam halos and its regeneration can be eliminated. This method is easy to realize in experiment .The research offers a valuable reference for the design of the periodic focusing channels in the highcurrent linear proton accelerators．
2004,
16.
Abstract:
The Xray transport of flash radiograph about FTO（French test object）was studied. Within the recording plane at 3m, the direct and scattering exposures, the directscattering ratio, the spatial spectrum distributions of direct and scattering exposure and flux are respectively given by means of MonteCarlo simulation. It can be concluded from these results that the back cone, from which 97% scattering exposure comes, is the primary scattering source and the key component which makes the spatial distribution of scattering exposure nonuniformity 58%. The minimum directscattering ratio of the radiograph system is so small that the direct exposure can be ignored in comparison with the scattering exposure. The record method with high resolution is used during the simulation, and the recon
The Xray transport of flash radiograph about FTO（French test object）was studied. Within the recording plane at 3m, the direct and scattering exposures, the directscattering ratio, the spatial spectrum distributions of direct and scattering exposure and flux are respectively given by means of MonteCarlo simulation. It can be concluded from these results that the back cone, from which 97% scattering exposure comes, is the primary scattering source and the key component which makes the spatial distribution of scattering exposure nonuniformity 58%. The minimum directscattering ratio of the radiograph system is so small that the direct exposure can be ignored in comparison with the scattering exposure. The record method with high resolution is used during the simulation, and the recon
2004,
16.
Abstract:
In this paper, the basic theory of optical transition radiation(OTR) is described. The schemes of experiments on an electron beam of 18MeV, 2.7kA using OTR are presented. In the diagnostics of such an intense beam, some difficulties including strong visible light and Xray background interference and so on, have been solved. The characteristic pattern of OTR is obtained. With OTR method, the beam profile, energy, divergence and emittence were measured. The preliminary results show that OTR method is an effective way for intense beam diagnostics.
In this paper, the basic theory of optical transition radiation(OTR) is described. The schemes of experiments on an electron beam of 18MeV, 2.7kA using OTR are presented. In the diagnostics of such an intense beam, some difficulties including strong visible light and Xray background interference and so on, have been solved. The characteristic pattern of OTR is obtained. With OTR method, the beam profile, energy, divergence and emittence were measured. The preliminary results show that OTR method is an effective way for intense beam diagnostics.
2004,
16.
Abstract:
The injection and extraction deflectors of CSR are made of wrought aluminium with surface anodic oxidation. From the results of MAFIA calculation, the fillet radius and the width of the high voltage electrode are set to 20mm and 60mm respectively, in order to have enough homogeneous electric field region and to improve its withstand voltage. Half of the cutting electrode is a set of tungsten filaments which has a diameter of 0.1mm, and the other half is beaten tantalum. A deflector model was built and tested under the simulated running condition. The experimental result is in accord with theoretical analysis．
The injection and extraction deflectors of CSR are made of wrought aluminium with surface anodic oxidation. From the results of MAFIA calculation, the fillet radius and the width of the high voltage electrode are set to 20mm and 60mm respectively, in order to have enough homogeneous electric field region and to improve its withstand voltage. Half of the cutting electrode is a set of tungsten filaments which has a diameter of 0.1mm, and the other half is beaten tantalum. A deflector model was built and tested under the simulated running condition. The experimental result is in accord with theoretical analysis．
2004,
16.
Abstract:
The paper introduces the Genetic Algorithms(GA) theory and the design point applied to the process of beam tuning in accelerator. It gives the design method about automatic beam tuning in accelerator which is based on GA, and moreover compiles a GA program that is used to carry out a computer simulation experiment in view of a section of beam line in HIRFL. Thus the paper proves the feasibility of automatic beam tuning based upon GA, and at the same time points out future research direction about the technology of automatic beam tuning．
The paper introduces the Genetic Algorithms(GA) theory and the design point applied to the process of beam tuning in accelerator. It gives the design method about automatic beam tuning in accelerator which is based on GA, and moreover compiles a GA program that is used to carry out a computer simulation experiment in view of a section of beam line in HIRFL. Thus the paper proves the feasibility of automatic beam tuning based upon GA, and at the same time points out future research direction about the technology of automatic beam tuning．
2004,
16.
Abstract:
Based on analysis and comparison of overseas designs of vacuum insulator stacks(VIS) of Zpinch devices, the paper summarizes and discusses the key points of VIS designing and manufacturing. Firstly, it describes the way of VIS development in general, then details the following key points: electrostatic numerical simulation, inductance parameter calculation and circuit simulation, flashover probability analysis, VIS structure stability analysis and material selection. Finally, the paper dicusses the optimization and further application of flashover probability analysis method.
Based on analysis and comparison of overseas designs of vacuum insulator stacks(VIS) of Zpinch devices, the paper summarizes and discusses the key points of VIS designing and manufacturing. Firstly, it describes the way of VIS development in general, then details the following key points: electrostatic numerical simulation, inductance parameter calculation and circuit simulation, flashover probability analysis, VIS structure stability analysis and material selection. Finally, the paper dicusses the optimization and further application of flashover probability analysis method.
