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RSS2004 Vol. 16, No. 10
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2004,
16.
Abstract:
Atom lens generated by a laser standing wave can be used to focus an atomic beam to nanometer dimensions. Aberrations exist in atom lens owing to the influence of velocity spread, beam spread, wave nature of atoms and so on. Two theoretical models were built to describe atom lens. Spherical aberration, chromatic aberration and the aberration caused by angular spread were analyzed with semiclassical model, and diffractive aberration was analyzed using quantum model. Simulation results show that aberration originates mainly from beam spread, and diffractive aberration is larger than spherical aberration and chromatic aberration. Three solutions of optimization of experimental parameters, adding beam mask and using etching technologies for improving atom lithography quality are presented.
Atom lens generated by a laser standing wave can be used to focus an atomic beam to nanometer dimensions. Aberrations exist in atom lens owing to the influence of velocity spread, beam spread, wave nature of atoms and so on. Two theoretical models were built to describe atom lens. Spherical aberration, chromatic aberration and the aberration caused by angular spread were analyzed with semiclassical model, and diffractive aberration was analyzed using quantum model. Simulation results show that aberration originates mainly from beam spread, and diffractive aberration is larger than spherical aberration and chromatic aberration. Three solutions of optimization of experimental parameters, adding beam mask and using etching technologies for improving atom lithography quality are presented.
2004,
16.
Abstract:
For finitethickness media with convective surface losses, the threedimensional temperature distributions of solid materials which are due to absorption of laser light with a Gaussian powerdensity profile, are calculated using the wellknown Green's function methods. Some expressions and theoretical profiles of the temperature distributions as functions of the size and the thickness of a substrate are obtained. The results of the calculations show that the temperature rise is closely related to the nature of the medium itself (specific heat, thermal conductivity, density), as well as to the absorption coefficient of medium, the parameters of the incident laser (power density, energy distribution, spot size, irradiating time), and the convective heattransfer coefficient. The tempera
For finitethickness media with convective surface losses, the threedimensional temperature distributions of solid materials which are due to absorption of laser light with a Gaussian powerdensity profile, are calculated using the wellknown Green's function methods. Some expressions and theoretical profiles of the temperature distributions as functions of the size and the thickness of a substrate are obtained. The results of the calculations show that the temperature rise is closely related to the nature of the medium itself (specific heat, thermal conductivity, density), as well as to the absorption coefficient of medium, the parameters of the incident laser (power density, energy distribution, spot size, irradiating time), and the convective heattransfer coefficient. The tempera
2004,
16.
Abstract:
The system for effective area measurement of laser spot on target plane was designed based on the definition of effective area. A 12bit CCD camera is used for the effecive area measurement. A bmp image of the beam profile is stored. This image is processing by software to evaluate the ratio of total energy and peak fluence (effective area). Some test results were given using effective area measurement system. The system was employed in the laser induced damage threshold test and it is helpful to improving the precision of laser induced damage threshold test.
The system for effective area measurement of laser spot on target plane was designed based on the definition of effective area. A 12bit CCD camera is used for the effecive area measurement. A bmp image of the beam profile is stored. This image is processing by software to evaluate the ratio of total energy and peak fluence (effective area). Some test results were given using effective area measurement system. The system was employed in the laser induced damage threshold test and it is helpful to improving the precision of laser induced damage threshold test.
Ｅxperimental and simulative investigation of HYLTE nozzle's mixed flowfield in DF/HF chemical lasers
2004,
16.
Abstract:
The flowfield of hypersonic low temperature(HYLTE)nozzle in continuous wave DF/HF chemical lasers was visualized by laser induced iodine fluorescence(LIIF) and simulated by the CFD software FLUENT. The results from the two methods were compared and basically accord with each other. In the condition given in the article, the oxidant flow was drilled by the fuel. It was compressed first and expanded later.The two streams mixed enough at the plane 10m away from the exit plane. The experimental results show that the direction of the fuel stream changed slightly while the simulative result indicated that the fuel stream flowed almost along the x axis．
The flowfield of hypersonic low temperature(HYLTE)nozzle in continuous wave DF/HF chemical lasers was visualized by laser induced iodine fluorescence(LIIF) and simulated by the CFD software FLUENT. The results from the two methods were compared and basically accord with each other. In the condition given in the article, the oxidant flow was drilled by the fuel. It was compressed first and expanded later.The two streams mixed enough at the plane 10m away from the exit plane. The experimental results show that the direction of the fuel stream changed slightly while the simulative result indicated that the fuel stream flowed almost along the x axis．
2004,
16.
Abstract:
Numerical analysis for Ybdoped doubleclad fiber lasers is carried out. The simulative results include dependence of laser output power on pump power, fiber length, output mirror reflectivity and the differences of output performance for the cases of oneend and twoend pumps. The fiber laser experiment has been performed in the case of twoend open cavity. When incident pump power was 8.84W, the output power of 3.16W was attained with coupling efficiency of 77% and slope efficiency 375%. The experimental data are in agreement with numerical analysis results.
Numerical analysis for Ybdoped doubleclad fiber lasers is carried out. The simulative results include dependence of laser output power on pump power, fiber length, output mirror reflectivity and the differences of output performance for the cases of oneend and twoend pumps. The fiber laser experiment has been performed in the case of twoend open cavity. When incident pump power was 8.84W, the output power of 3.16W was attained with coupling efficiency of 77% and slope efficiency 375%. The experimental data are in agreement with numerical analysis results.
2004,
16.
Abstract:
Acousto-optic programmable filters (AOPDF) can compensate in real time for groupdelay dispersion. This feature can be used in femtosecond chirped-pulse amplification to compensate dispersion adaptively. An analytical expression relating the group delay at the output of the AOPDF to the input acoustic signal was obtained with coupled-wave theory in the case of collinear bulk acousto-optic interactions. Numerical simulations in the LiNbO3 crystal are shown to support the principle of arbitrary group-delay control with an AOPDF.
Acousto-optic programmable filters (AOPDF) can compensate in real time for groupdelay dispersion. This feature can be used in femtosecond chirped-pulse amplification to compensate dispersion adaptively. An analytical expression relating the group delay at the output of the AOPDF to the input acoustic signal was obtained with coupled-wave theory in the case of collinear bulk acousto-optic interactions. Numerical simulations in the LiNbO3 crystal are shown to support the principle of arbitrary group-delay control with an AOPDF.
2004,
16.
Abstract:
When the capillary discharge device runs with prepulse and mainpulse, its efficiency of energy transferring by bumping to X-ray laser rises. The control of trigger delay time from prepulse to mainpulse is very important for this device. Based on the introduction of the circuit to generate prepulse, the delay circuit which consists of IC chip is applied in the highvoltage fast discharge system by the technology of photoelectric coupling and pulse transformer isolation, the delay time can be adjusted continuously, and the experimental results about the adjustment of pulses are given, the results prove that the delay time of the circuit is from 2μs to 50μs and it is good for producing soft X-ray laser．
When the capillary discharge device runs with prepulse and mainpulse, its efficiency of energy transferring by bumping to X-ray laser rises. The control of trigger delay time from prepulse to mainpulse is very important for this device. Based on the introduction of the circuit to generate prepulse, the delay circuit which consists of IC chip is applied in the highvoltage fast discharge system by the technology of photoelectric coupling and pulse transformer isolation, the delay time can be adjusted continuously, and the experimental results about the adjustment of pulses are given, the results prove that the delay time of the circuit is from 2μs to 50μs and it is good for producing soft X-ray laser．
2004,
16.
Abstract:
In this paper,a combination of integral and differential methods were applied to calculate the mode characteristics of beamconvereting annular resonator with various chemical annular gain medium.Two designs were compared:one is designed without beam rotaion in the compact leg,and the other with beam rotating 90°. It shows that beam rotation in the compact leg has little effect on the mode characteristics,when the resonator is aligned perfectly.However,when the resonator is misaligned,beam rotation in the compact leg can not only sustain zerolevel mode, but also get better beam quality and output power than the resonator without beam rotation. In practice resonators can not be aligned perfectly,so beam rotation is necessary to beamconverting annular resonator.
In this paper,a combination of integral and differential methods were applied to calculate the mode characteristics of beamconvereting annular resonator with various chemical annular gain medium.Two designs were compared:one is designed without beam rotaion in the compact leg,and the other with beam rotating 90°. It shows that beam rotation in the compact leg has little effect on the mode characteristics,when the resonator is aligned perfectly.However,when the resonator is misaligned,beam rotation in the compact leg can not only sustain zerolevel mode, but also get better beam quality and output power than the resonator without beam rotation. In practice resonators can not be aligned perfectly,so beam rotation is necessary to beamconverting annular resonator.
2004,
16.
Abstract:
In high power laser system, a small size phasedistortion wavefront measure is necessary to compensate and control the wavefront of laser beam with intermediate frequency. Array Fresnel zone plates splitting wavefront and the Southwell model of zonal wavefront reconstruction arithmetic are presented, the effect of the sub-apertures of wavefront sensor and variation range of distorted phase on wavefront reconstruction are analyzed in detail, and a suitable number 20×２０～３０×３０ of array Fresnel zone plates is given. Simulation results show the error of wavefront reconstruction with this method is small than one-tenth wavelength．
In high power laser system, a small size phasedistortion wavefront measure is necessary to compensate and control the wavefront of laser beam with intermediate frequency. Array Fresnel zone plates splitting wavefront and the Southwell model of zonal wavefront reconstruction arithmetic are presented, the effect of the sub-apertures of wavefront sensor and variation range of distorted phase on wavefront reconstruction are analyzed in detail, and a suitable number 20×２０～３０×３０ of array Fresnel zone plates is given. Simulation results show the error of wavefront reconstruction with this method is small than one-tenth wavelength．
2004,
16.
Abstract:
The influences of homogeneous, layered and fractional improved conductivity soil on transient grounding resistance (TGR) under pulsed discharging current are analyzed by using FDTD method in this paper. The results show that the ground conductivity has significant influence on TGR. In homogeneous soil, TGR and the influence of the buried depth of the grounding conductor on TGR decrease with increasing ground conductivity. In layered soil, the grounding conductor should be buried in the high conductivity layered soil, and not near the layered boundary. The locally improved conductivity will decrease TGR,and TGR is sensitive to this locally improved soil volume.And for the locally improved soil where the conductivity is enough large, the farther increasing of the conductivity has little effe
The influences of homogeneous, layered and fractional improved conductivity soil on transient grounding resistance (TGR) under pulsed discharging current are analyzed by using FDTD method in this paper. The results show that the ground conductivity has significant influence on TGR. In homogeneous soil, TGR and the influence of the buried depth of the grounding conductor on TGR decrease with increasing ground conductivity. In layered soil, the grounding conductor should be buried in the high conductivity layered soil, and not near the layered boundary. The locally improved conductivity will decrease TGR,and TGR is sensitive to this locally improved soil volume.And for the locally improved soil where the conductivity is enough large, the farther increasing of the conductivity has little effe
2004,
16.
Abstract:
In this paper , computational code MFCGⅢ of the explosive magnetic field compression generator (MFCG) are developed based on the analytic formulas of magnetic field , stream function and induced current for the process of charge and compression. Under the same conditions , computational results obtained by 2-D MFCGⅢ code coincide with results obtained by experiment. Therefore , the design optimization can be achieve by MFCGⅢ for MFCG tests and the concerned physical problems can be analyzed and explained by MFCGⅢ in MFCG tests．
In this paper , computational code MFCGⅢ of the explosive magnetic field compression generator (MFCG) are developed based on the analytic formulas of magnetic field , stream function and induced current for the process of charge and compression. Under the same conditions , computational results obtained by 2-D MFCGⅢ code coincide with results obtained by experiment. Therefore , the design optimization can be achieve by MFCGⅢ for MFCG tests and the concerned physical problems can be analyzed and explained by MFCGⅢ in MFCG tests．
2004,
16.
Abstract:
The coupling wave theory is utilized to analyze the process of modes coupling in circular tapers feed. The relationships of modes coupling and radiation performance in different geometical form feeds were obtained. Based on the calculations, a prototype feed has been designed and measured. These measurements demonstrate good agreement with computer prediction using couplingwave theory software. All that make a base for designing a high power circular Gaussian feed.
The coupling wave theory is utilized to analyze the process of modes coupling in circular tapers feed. The relationships of modes coupling and radiation performance in different geometical form feeds were obtained. Based on the calculations, a prototype feed has been designed and measured. These measurements demonstrate good agreement with computer prediction using couplingwave theory software. All that make a base for designing a high power circular Gaussian feed.
2004,
16.
Abstract:
This paper describes the thermal and structural analysis of the electron gun cathode and its support structure using ANSYS package. With this package the temperature and thermal expansion of the cathode and its support have been computed. In the hot condition the effects of the thermalstress to the shot distance, waist radius, perveance and compress ratio of the electron beam have been brought out by TWTCAD. Good agreement is observed between the numerical and experimental results. The influences of the thermal expansion of the cathod and its support on the beam behavior werer discussed.The results presented here are beneficial to the design of the TWT．
This paper describes the thermal and structural analysis of the electron gun cathode and its support structure using ANSYS package. With this package the temperature and thermal expansion of the cathode and its support have been computed. In the hot condition the effects of the thermalstress to the shot distance, waist radius, perveance and compress ratio of the electron beam have been brought out by TWTCAD. Good agreement is observed between the numerical and experimental results. The influences of the thermal expansion of the cathod and its support on the beam behavior werer discussed.The results presented here are beneficial to the design of the TWT．
2004,
16.
Abstract:
The finite-difference time-domain method is used to numerically simulate electromagnetic field distribution of horizontally-polarized electromagnetic pulse simulators. Some important factors representative of simulator performance such as waveform, spatial variation and uniformity are studied. The rise time of EMP generated by the simulator is 10ns, approximately the same as the rise time of voltage source. Waveform of EMP is greatly different from that of the voltage pulse. Electric field attenuates rapidly along the horizonal axis. This kind of antenna can generate uniformly distributed EMP with high electric field strength and short rise time in a large area(≥50m,horizontal directions)．
The finite-difference time-domain method is used to numerically simulate electromagnetic field distribution of horizontally-polarized electromagnetic pulse simulators. Some important factors representative of simulator performance such as waveform, spatial variation and uniformity are studied. The rise time of EMP generated by the simulator is 10ns, approximately the same as the rise time of voltage source. Waveform of EMP is greatly different from that of the voltage pulse. Electric field attenuates rapidly along the horizonal axis. This kind of antenna can generate uniformly distributed EMP with high electric field strength and short rise time in a large area(≥50m,horizontal directions)．
2004,
16.
Abstract:
This paper describes the gain and bandwidth of multiple beam klystron(MBK) with M beams and N cavities, presents the formula to describe the relation of the gain and bandwidth of the small signal with structural parameters of the device and the beam parameters, gives the curves of gain versus frequency in the various parameters, and analyzes the effects of multiple cavities on gain and multiple beam on bandwidth. Finally it estimates the gain bandwidth of a MBK is 8.1%.
This paper describes the gain and bandwidth of multiple beam klystron(MBK) with M beams and N cavities, presents the formula to describe the relation of the gain and bandwidth of the small signal with structural parameters of the device and the beam parameters, gives the curves of gain versus frequency in the various parameters, and analyzes the effects of multiple cavities on gain and multiple beam on bandwidth. Finally it estimates the gain bandwidth of a MBK is 8.1%.
2004,
16.
Abstract:
This paper gives an accurate calculation model of microwave being absorbed in atmosphere which expands the traditional approximate algorithm that ignores the change of temperature, humidity and pressure and is limited by transmission distance, simulates the absorption attenuation in atmosphere of a certain area in our country according to its weather data from actual measurements, and finally analyses the propagation characteristic of microwave changing with frequency, elevation angle and season, and briefly explains the practical significance of this research in microwave remote sensing．
This paper gives an accurate calculation model of microwave being absorbed in atmosphere which expands the traditional approximate algorithm that ignores the change of temperature, humidity and pressure and is limited by transmission distance, simulates the absorption attenuation in atmosphere of a certain area in our country according to its weather data from actual measurements, and finally analyses the propagation characteristic of microwave changing with frequency, elevation angle and season, and briefly explains the practical significance of this research in microwave remote sensing．
2004,
16.
Abstract:
In this paper, the induced current in the finite cable near ground is calculated by FDTD method when exposed to HEMP,HPM and UWB pulse respectively. The numerical results indicate that the induced current varies with the length of cable, incident angle and the conductivity of ground. With the same electric field intensity, the HEMP induced current is the largest one among the three induced currents. There's almost no comparable difference between the induced currents in the 5m and 20m cable when exposed to HPM and UWB pulse. The larger the conductivity of ground is, the more quickly the induced current attenuates. When the cable is grounded at one end the current at the grounded end will increase.
In this paper, the induced current in the finite cable near ground is calculated by FDTD method when exposed to HEMP,HPM and UWB pulse respectively. The numerical results indicate that the induced current varies with the length of cable, incident angle and the conductivity of ground. With the same electric field intensity, the HEMP induced current is the largest one among the three induced currents. There's almost no comparable difference between the induced currents in the 5m and 20m cable when exposed to HPM and UWB pulse. The larger the conductivity of ground is, the more quickly the induced current attenuates. When the cable is grounded at one end the current at the grounded end will increase.
2004,
16.
Abstract:
In this paper, with the consideration of the radial thickness of the helix, the tape helix model is suggested for the vaneloaded helical slowwave structures. By taking the sicretesupports bars into some continuous dielectric tube regions, the expressions of attenuation constant are obtained. The effect on loss of the envelope, the vane and the helix material conductivity are all taken into account. This model can increase the calculated value of the attenuation constant. The results indicate that the loss of the helix occupies most of the whole loss.
In this paper, with the consideration of the radial thickness of the helix, the tape helix model is suggested for the vaneloaded helical slowwave structures. By taking the sicretesupports bars into some continuous dielectric tube regions, the expressions of attenuation constant are obtained. The effect on loss of the envelope, the vane and the helix material conductivity are all taken into account. This model can increase the calculated value of the attenuation constant. The results indicate that the loss of the helix occupies most of the whole loss.
2004,
16.
Abstract:
This paper presents experimental results on an L-band relativistic klystron amplifier in Sinus 700 accelerator. It includes the modulation of intense relativistic electron beam(IREB) after driving through gaps of the input-cavity and the idler cavity, and microwave extraction from the modulated IREB. Annular electron beams of voltage 750kV, current 8.6kA, diameter 57mm, thickness 2mm were produced from annular foilless diode, and 2.1GW/15ns,1.7GW/18ns,0.75GW/30ns output peak microwave power were observed after three cavities,respectively. The efficiency is 14%～33%, and the gain is about 32～40dB.At the same time, microwave pulseshortening was found in experiment．
This paper presents experimental results on an L-band relativistic klystron amplifier in Sinus 700 accelerator. It includes the modulation of intense relativistic electron beam(IREB) after driving through gaps of the input-cavity and the idler cavity, and microwave extraction from the modulated IREB. Annular electron beams of voltage 750kV, current 8.6kA, diameter 57mm, thickness 2mm were produced from annular foilless diode, and 2.1GW/15ns,1.7GW/18ns,0.75GW/30ns output peak microwave power were observed after three cavities,respectively. The efficiency is 14%～33%, and the gain is about 32～40dB.At the same time, microwave pulseshortening was found in experiment．
2004,
16.
Abstract:
The Rosseland mean opacity of hohlraum gold wall can be increased by adding other materials such as gadolinium to gold. At 0.1g/cm3 density and various radiation temperatures, the AuGd mixtures with equal fractional number density yield highest opacities. Using onedimension radiation hydrodynamics code RT87 combined with the Rosseland mean opacity database and state equations at multipleionized area, the radiation temperature of pure Au and AuGd mixture wall hohlraum were investigated under the condition of Xray source produced at ShenguangII laser facility. The simulation results show radiation energy loss of the wall decrease and radiation temperature increase 0.1~0.2MK for AuGd mixture hohlraum.
The Rosseland mean opacity of hohlraum gold wall can be increased by adding other materials such as gadolinium to gold. At 0.1g/cm3 density and various radiation temperatures, the AuGd mixtures with equal fractional number density yield highest opacities. Using onedimension radiation hydrodynamics code RT87 combined with the Rosseland mean opacity database and state equations at multipleionized area, the radiation temperature of pure Au and AuGd mixture wall hohlraum were investigated under the condition of Xray source produced at ShenguangII laser facility. The simulation results show radiation energy loss of the wall decrease and radiation temperature increase 0.1~0.2MK for AuGd mixture hohlraum.
2004,
16.
Abstract:
With the development of largescale high power laser system, large size shortwaveband（such as 355nm）antireflective coatings are needed. In this paper, the SolGel deriving SiO2 nanostructure shortwaveband antireflective coatings were prepared. Ellipsometer, FTIR, UVVisVIR spectrometer and AFM were used to characterize the properties of the films. The refractive index of the film is about 1.22, and the thickness is 75nm. The reflectance of the film（on silica substrate）at 355nm is reduced to 0.2％. The scratchresistant property of film was improved obviously after ammonia treatment, the maximum transmission values of the film are only reoluced 0.13% and 0.39% after 20 and 50 times scratch by the tampon with dirty. After surface modification the hydrophobicity of the film is
With the development of largescale high power laser system, large size shortwaveband（such as 355nm）antireflective coatings are needed. In this paper, the SolGel deriving SiO2 nanostructure shortwaveband antireflective coatings were prepared. Ellipsometer, FTIR, UVVisVIR spectrometer and AFM were used to characterize the properties of the films. The refractive index of the film is about 1.22, and the thickness is 75nm. The reflectance of the film（on silica substrate）at 355nm is reduced to 0.2％. The scratchresistant property of film was improved obviously after ammonia treatment, the maximum transmission values of the film are only reoluced 0.13% and 0.39% after 20 and 50 times scratch by the tampon with dirty. After surface modification the hydrophobicity of the film is
2004,
16.
Abstract:
This paper introduces the electroless plating technique to fabricate integral hohlraum Cu target. Catalyzed by the metal surface of the pretreated PMMA axis, the reducing reaction deposits Cu on the axis and then the axis is etched and the surface passivation of the Cu plating is performed. Cu target obtained by this technique can meet the requirements of ICF targets,which has:(1) a surface of no porosity and no crackle; (2) a 17μm thick wall which can retain it's erectile form; (3) a plating of even thichness and of 99.2% Cu content; (4) the passivated surfae which shows no obvious change in 4 weeks. This fabrication technique provides a way to make other metal and alloy integral hohlraum targets for ICF.
This paper introduces the electroless plating technique to fabricate integral hohlraum Cu target. Catalyzed by the metal surface of the pretreated PMMA axis, the reducing reaction deposits Cu on the axis and then the axis is etched and the surface passivation of the Cu plating is performed. Cu target obtained by this technique can meet the requirements of ICF targets,which has:(1) a surface of no porosity and no crackle; (2) a 17μm thick wall which can retain it's erectile form; (3) a plating of even thichness and of 99.2% Cu content; (4) the passivated surfae which shows no obvious change in 4 weeks. This fabrication technique provides a way to make other metal and alloy integral hohlraum targets for ICF.
2004,
16.
Abstract:
The ps laser probe is a 308nm diagnostic light source for laser plasma diagnosis. It coverts a pulse of lns 1 054nm into a pulse of 263nm by double times frequency conversion, then it compresses 1ns to 30ps(FWHM) and the wavelength is shifted to 308nm by stimulated Raman scattering, at last the output laser is a pulse of output energy over 1mJ and 30ps.The experimental result is that the ps laser probe is output pulse of over 1mJ energy and 30ps(FWHM), and it runs over 90% stable rate, it accords with anticipated aim.
The ps laser probe is a 308nm diagnostic light source for laser plasma diagnosis. It coverts a pulse of lns 1 054nm into a pulse of 263nm by double times frequency conversion, then it compresses 1ns to 30ps(FWHM) and the wavelength is shifted to 308nm by stimulated Raman scattering, at last the output laser is a pulse of output energy over 1mJ and 30ps.The experimental result is that the ps laser probe is output pulse of over 1mJ energy and 30ps(FWHM), and it runs over 90% stable rate, it accords with anticipated aim.
2004,
16.
Abstract:
The third harmonic conversion of type I/ type II angledetuning scheme of KDP has been studied. And the effects of the walkoff in the third harmonic generation was investigated. A splitstep algorithm based on the Fast Fourier Transform and a RungeKutta integrator is used. As a result, the walkoff decreased not only the tripling efficiency but also the harmonic beams quality. When the waist radius of the fundamental wave is small, the walkoff is the main factor that makes the SHG and THG conversion efficiency decrease, while the effect of detuning angle is little. As the waist radius of the fundamental wave increases, the effect of the walkoff slowly reduces and the effect of detuning angle increases.
The third harmonic conversion of type I/ type II angledetuning scheme of KDP has been studied. And the effects of the walkoff in the third harmonic generation was investigated. A splitstep algorithm based on the Fast Fourier Transform and a RungeKutta integrator is used. As a result, the walkoff decreased not only the tripling efficiency but also the harmonic beams quality. When the waist radius of the fundamental wave is small, the walkoff is the main factor that makes the SHG and THG conversion efficiency decrease, while the effect of detuning angle is little. As the waist radius of the fundamental wave increases, the effect of the walkoff slowly reduces and the effect of detuning angle increases.
2004,
16.
Abstract:
Multifunctional cavity(MFC) is one of the most important parts of beam transport system in the “DragonⅠ” LIA. An MFC assembles the flange for vacuum pumps, the drifting tube for electron beam and the BPM for beam diagnostics on line together. Moreover, MFC is convenient to the machine repairing. In this paper, the key points of the MFC design are presented the alignment and repairability are clarified, the continuity of magnetic field is analyzed, the transverse impedance is simulated, and the methods to lower its transverse impedance are presented. The application of MFC has not only simplified the structure of beam transport line, but also improved its performances.
Multifunctional cavity(MFC) is one of the most important parts of beam transport system in the “DragonⅠ” LIA. An MFC assembles the flange for vacuum pumps, the drifting tube for electron beam and the BPM for beam diagnostics on line together. Moreover, MFC is convenient to the machine repairing. In this paper, the key points of the MFC design are presented the alignment and repairability are clarified, the continuity of magnetic field is analyzed, the transverse impedance is simulated, and the methods to lower its transverse impedance are presented. The application of MFC has not only simplified the structure of beam transport line, but also improved its performances.
2004,
16.
Abstract:
Northwest Institute of Nuclear Technology has imported an SOS-based pulsed generator with capacity of repetitive operating from Russia. The generator has the highest peak power and the highest average power among similar generators around the world. The structure is introduced and testing results are described in this paper. With varying of load, the S-5N generator has output voltage of 400~600kV, output current of 2~3kA, FWHM of 40~60ns and output energy of 40~65J per pulse. In the condition of 500Hz repetitive operating, the average output power is up to 30kW. The generator can operate continuously at repetition frequency of 300Hz and 3min at 500Hz.
Northwest Institute of Nuclear Technology has imported an SOS-based pulsed generator with capacity of repetitive operating from Russia. The generator has the highest peak power and the highest average power among similar generators around the world. The structure is introduced and testing results are described in this paper. With varying of load, the S-5N generator has output voltage of 400~600kV, output current of 2~3kA, FWHM of 40~60ns and output energy of 40~65J per pulse. In the condition of 500Hz repetitive operating, the average output power is up to 30kW. The generator can operate continuously at repetition frequency of 300Hz and 3min at 500Hz.
2004,
16.
Abstract:
Ceramic dielectric material is characterized of high dielectric constant and high working electric field. According to the excellent performance of the ceramic, this paper theoretically analyzes the capacitors made from such materials, which can work in oscillated discharging circuit in the frequency from some kHz to several MHz with slow-aging．The reliability of high energy density multilayer ceramic capacitor （MLC）has been studied by the 1μF/500V species with DC voltage withstanding 750V 1min test and repeated chargedischarge in the frequency of 100Hz. The results show that under the operating voltage of 500V(the energy density reachs 720J/L), the MLC has long lifetime over 107 shot times and large output peak current of 320A in the frequency of 50kHz, and steady electric perfo
Ceramic dielectric material is characterized of high dielectric constant and high working electric field. According to the excellent performance of the ceramic, this paper theoretically analyzes the capacitors made from such materials, which can work in oscillated discharging circuit in the frequency from some kHz to several MHz with slow-aging．The reliability of high energy density multilayer ceramic capacitor （MLC）has been studied by the 1μF/500V species with DC voltage withstanding 750V 1min test and repeated chargedischarge in the frequency of 100Hz. The results show that under the operating voltage of 500V(the energy density reachs 720J/L), the MLC has long lifetime over 107 shot times and large output peak current of 320A in the frequency of 50kHz, and steady electric perfo
2004,
16.
Abstract:
During the pulse compression process, dynamic parameters of magntic core experience two phase of unsaturated and saturated, and which correspond to a half hysteresis cycle. The diagnosis of the winding current and the change rate of magntic flux on the magnetic core provides necessary value for determining the hysteresis cycle, saturated magnetic flux intensity and retentiveness of magntic core. Principle of this diagnosis and method of dynamic parameters on magnetic core are discussed. The schematic circuit and optimizing method of circuit elements for diagnosis equipment are also given as well as the experimental results.
During the pulse compression process, dynamic parameters of magntic core experience two phase of unsaturated and saturated, and which correspond to a half hysteresis cycle. The diagnosis of the winding current and the change rate of magntic flux on the magnetic core provides necessary value for determining the hysteresis cycle, saturated magnetic flux intensity and retentiveness of magntic core. Principle of this diagnosis and method of dynamic parameters on magnetic core are discussed. The schematic circuit and optimizing method of circuit elements for diagnosis equipment are also given as well as the experimental results.
2004,
16.
Abstract:
It is shown that the propagation of chargedparticle beam can be made in complete analogy with the transmission of ellipseGaussian light beam in paraxial approximation. Based on this similarity, the ABCDlike law for chargedparticle beam transport with transversal divergence is developed by means of a complex curvature radius of chargedparticle beam in which its real part shows the beam characteristics of convergent and divergent and its imaginary part shows the beam radius. From this, chargedparticle beam as a whole is thought of as a single ellipse Gaussian lightlike beam whose emittance plays the role of wavelength. In particular, this analogy gives an insight that it is hopeful to attain possible coherent chargedparticle beam in favorable accelerator environment.
It is shown that the propagation of chargedparticle beam can be made in complete analogy with the transmission of ellipseGaussian light beam in paraxial approximation. Based on this similarity, the ABCDlike law for chargedparticle beam transport with transversal divergence is developed by means of a complex curvature radius of chargedparticle beam in which its real part shows the beam characteristics of convergent and divergent and its imaginary part shows the beam radius. From this, chargedparticle beam as a whole is thought of as a single ellipse Gaussian lightlike beam whose emittance plays the role of wavelength. In particular, this analogy gives an insight that it is hopeful to attain possible coherent chargedparticle beam in favorable accelerator environment.
2004,
16.
Abstract:
Accurate mechanical axis alignment is a basic requirement for assembling a linear induction accelerator (LIA). The total length of an LIA is usually over thirty or fifty meters, and it consists of many induction cells. By using a laser tracker a new method of mechanical axis alignment for LIA is established to achieve the high accuracy. This paper introduces the method and gives implimentation step and point position measure errors of the mechanical axis alignment. During the alignment process a 55mlong alignment control survey net is built, and the theoretic revision of the coordinate of the control survey net is presented.
Accurate mechanical axis alignment is a basic requirement for assembling a linear induction accelerator (LIA). The total length of an LIA is usually over thirty or fifty meters, and it consists of many induction cells. By using a laser tracker a new method of mechanical axis alignment for LIA is established to achieve the high accuracy. This paper introduces the method and gives implimentation step and point position measure errors of the mechanical axis alignment. During the alignment process a 55mlong alignment control survey net is built, and the theoretic revision of the coordinate of the control survey net is presented.
2004,
16.
Abstract:
Active feedback systems are required to suppress CBI in BEPCⅡ. The BEPCⅡ transverse feedback system mainly includes three parts:the signal detection, the signal process and the kicker as the key part. The magnitude of feedback power is a very important parameter that is closely related to the design of the kicker. The stripline electrodes are used as the kicker in BEPCⅡ. In this paper the numeric modelling by means of the Hewlett&Packard high frequency structure simulation code and the simulation result of the kicker is given. The simulation result is almost same as the result coming from the formula and the reflection coefficient is less than 7 percent in the bandwidth of DC250MHz, the 1 300Ω shunt impedance can be achieved in the frequency of 250MHz, so 123 watts feedback power shoul
Active feedback systems are required to suppress CBI in BEPCⅡ. The BEPCⅡ transverse feedback system mainly includes three parts:the signal detection, the signal process and the kicker as the key part. The magnitude of feedback power is a very important parameter that is closely related to the design of the kicker. The stripline electrodes are used as the kicker in BEPCⅡ. In this paper the numeric modelling by means of the Hewlett&Packard high frequency structure simulation code and the simulation result of the kicker is given. The simulation result is almost same as the result coming from the formula and the reflection coefficient is less than 7 percent in the bandwidth of DC250MHz, the 1 300Ω shunt impedance can be achieved in the frequency of 250MHz, so 123 watts feedback power shoul
2004,
16.
Abstract:
The relation between the line attenuation coefficient and the material thickness of FTO has been studied, and the function between them has been given. The results show that the efficient linear attenuation coefficient decreases when the thickness of material increases in the transmission direction of Xray. Specially，the average efficient attenuation coefficient in the FTO is 0.838cm－1 for tungsten with precision of 4.5% and 0.297cm－1 for copper with precision of 5.0%. The spectrum effect on attenuation coefficient is less than 5%. The material densities can be reconstructed with such precision.
The relation between the line attenuation coefficient and the material thickness of FTO has been studied, and the function between them has been given. The results show that the efficient linear attenuation coefficient decreases when the thickness of material increases in the transmission direction of Xray. Specially，the average efficient attenuation coefficient in the FTO is 0.838cm－1 for tungsten with precision of 4.5% and 0.297cm－1 for copper with precision of 5.0%. The spectrum effect on attenuation coefficient is less than 5%. The material densities can be reconstructed with such precision.
