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RSS2003 Vol. 15, No. 09
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2003,
15.
Abstract:
This paper presents the study on the coaxial diskloaded waveguide as the slowwave structure of the relativistic traveling wave tube(RTWT). The inner conductor is employed in this structure to improve the characteristics of such slowwave system. The paper emphasizes the smallsignal analysis of the RTWT with coaxial diskloaded waveguide, and discusses the influence of the beam parameters and the structure dimensions on the smallsignal gain and phase velocity of slowwave, the results provides the theoretical basis for the design of the coaxial diskloaded RTWT.
This paper presents the study on the coaxial diskloaded waveguide as the slowwave structure of the relativistic traveling wave tube(RTWT). The inner conductor is employed in this structure to improve the characteristics of such slowwave system. The paper emphasizes the smallsignal analysis of the RTWT with coaxial diskloaded waveguide, and discusses the influence of the beam parameters and the structure dimensions on the smallsignal gain and phase velocity of slowwave, the results provides the theoretical basis for the design of the coaxial diskloaded RTWT.
2003,
15.
Abstract:
A tapered rectangular diskloaded gyroTWT amplifier with tapered guiding magnetic field and disk height, and partially decreasing period length is presented. The gain and the bandwidth are derived, the effect of the beam current, guide magnetic field, and input power on the output is numerically calculated. The output power is 88kW to 103kW with 16.63% to 24.11% relative bandwidth.
A tapered rectangular diskloaded gyroTWT amplifier with tapered guiding magnetic field and disk height, and partially decreasing period length is presented. The gain and the bandwidth are derived, the effect of the beam current, guide magnetic field, and input power on the output is numerically calculated. The output power is 88kW to 103kW with 16.63% to 24.11% relative bandwidth.
2003,
15.
Abstract:
By employing a 2.5-D PIC code, the three-cavity transit-time oscillator (TCO) is simulated numerically and the details are presented. It is found that the TCO can modulate REB, that the modulated beam can be converted to HPM, and that the frequency of microwave accords with theoretical ones. The relations between output power and span of inverse diode and that between output power and r-distance of extractor are obtained. Furthermore, the relation between output power and span of foils is presented and it accords with that of the linear theory. A 600MW, 5 GHz peak output power microwave is generated by simulation, with 400 kV electron beam voltage and 4 kA current. The start time to oscillate is about 3.5 ns. The peak efficiency is over 37%.
By employing a 2.5-D PIC code, the three-cavity transit-time oscillator (TCO) is simulated numerically and the details are presented. It is found that the TCO can modulate REB, that the modulated beam can be converted to HPM, and that the frequency of microwave accords with theoretical ones. The relations between output power and span of inverse diode and that between output power and r-distance of extractor are obtained. Furthermore, the relation between output power and span of foils is presented and it accords with that of the linear theory. A 600MW, 5 GHz peak output power microwave is generated by simulation, with 400 kV electron beam voltage and 4 kA current. The start time to oscillate is about 3.5 ns. The peak efficiency is over 37%.
2003,
15.
Abstract:
In this paper, the transmissionline method are used to calculate the HEMP induced skin current in cable shielding near ground. The change law of cable skin current with waveform injecting field, cable length and grounding state of shielding layer of cable was obtained. The calculating results indicate that the waveform of skin current is closely related with the skingrounding condition and when the peak magnitudes of injecting field are uniform, the wider the waveform of injecting field, the larger the skin current. A part of calculated results are compared with the calculated ones of FDTD method and experimental ones. There is good consistence between them.
In this paper, the transmissionline method are used to calculate the HEMP induced skin current in cable shielding near ground. The change law of cable skin current with waveform injecting field, cable length and grounding state of shielding layer of cable was obtained. The calculating results indicate that the waveform of skin current is closely related with the skingrounding condition and when the peak magnitudes of injecting field are uniform, the wider the waveform of injecting field, the larger the skin current. A part of calculated results are compared with the calculated ones of FDTD method and experimental ones. There is good consistence between them.
2003,
15.
Abstract:
Based on the 1D single electron theory of the interaction between the electron and microwave, the generation and the oscillation of microwave in the foldaway concentric cylinders resonant cavity are analyzed. Employing a 2.5-D PIC code, A radial klystron oscillator with foldaway concentric cylinders resonant cavity is simulated numerically. With a 380kV and 18kA electron beam, a peak value power of 1GW,1.52GHz output microwave is generated by simulation. As the electron beam is strongly nonlinearly modulated by the microwave in the cavity, the output microwave has harmonic components of different frequency.
Based on the 1D single electron theory of the interaction between the electron and microwave, the generation and the oscillation of microwave in the foldaway concentric cylinders resonant cavity are analyzed. Employing a 2.5-D PIC code, A radial klystron oscillator with foldaway concentric cylinders resonant cavity is simulated numerically. With a 380kV and 18kA electron beam, a peak value power of 1GW,1.52GHz output microwave is generated by simulation. As the electron beam is strongly nonlinearly modulated by the microwave in the cavity, the output microwave has harmonic components of different frequency.
2003,
15.
Abstract:
In this paper, the coupling of two modulation cavities in a relativistic klytron oscillator is studied using a field method. A relation of the coupling coefficient with the size. gap of the cavity and waveguide and the distance between two cavities is derived, and the calculating value of the coupling coefficient agrees with its experimental one basically.
In this paper, the coupling of two modulation cavities in a relativistic klytron oscillator is studied using a field method. A relation of the coupling coefficient with the size. gap of the cavity and waveguide and the distance between two cavities is derived, and the calculating value of the coupling coefficient agrees with its experimental one basically.
2003,
15.
Abstract:
A new SBS model, which is described as self stokes seeding (SSS), is brought forward and its mechanism is researched. The SBS coupled wave equations are solved numerically and laser induced stress is obtained spatially. Theoretical model is established to study the damage process inuced by SSS process and damage thresholds are calculated. Physical chracteristics which should be embodied by SBS damage mechanism are analyzed, and the dependence of laser pulse width and interaction length on damage thresholds is presented. The theoretical research shows that the SBS induced damage mostly happens at the entrance surface of pump laser and the threshold intensity is inversely proportional to laser pulse width and the interaction length.
A new SBS model, which is described as self stokes seeding (SSS), is brought forward and its mechanism is researched. The SBS coupled wave equations are solved numerically and laser induced stress is obtained spatially. Theoretical model is established to study the damage process inuced by SSS process and damage thresholds are calculated. Physical chracteristics which should be embodied by SBS damage mechanism are analyzed, and the dependence of laser pulse width and interaction length on damage thresholds is presented. The theoretical research shows that the SBS induced damage mostly happens at the entrance surface of pump laser and the threshold intensity is inversely proportional to laser pulse width and the interaction length.
2003,
15.
Abstract:
The influence of uncaptured electron on energy conversion efficiency in multiphoton nonlinear Compton scattering has been studied by using a particle theory and the inelastic collision model about electron and photon. It is found that the expansion width of the circular frequency optical spectrum of the scattered photons in multiphoton nonlinear Compton effect increases with the incident electron velocity increase and the increase of the photon number by the electron absorpted at the same time，and it reduces when the inelastic collision between electron and photon increases. The expression of the direct ratio lowering of the energy conversion efficiency by electron incident speed in multiphoton nonlinear Compton scattering and a method of lowering the loss with low energy electron i
The influence of uncaptured electron on energy conversion efficiency in multiphoton nonlinear Compton scattering has been studied by using a particle theory and the inelastic collision model about electron and photon. It is found that the expansion width of the circular frequency optical spectrum of the scattered photons in multiphoton nonlinear Compton effect increases with the incident electron velocity increase and the increase of the photon number by the electron absorpted at the same time，and it reduces when the inelastic collision between electron and photon increases. The expression of the direct ratio lowering of the energy conversion efficiency by electron incident speed in multiphoton nonlinear Compton scattering and a method of lowering the loss with low energy electron i
2003,
15.
Abstract:
The principle and experimental setup that can measure the chlorine utilization in singlet oxygen generator (SOG) for COIL have been introduced, and the results from the tests that contacted on a 0.1mol/s SOG has been presented. The error in the chlorine utilization measurement is less than 12%. The additional experiment is needless that the error is minished because we can get the chlorine utilization by the ratio of relative intensity of Raman spectrum. So the measurement efficiency is improved.
The principle and experimental setup that can measure the chlorine utilization in singlet oxygen generator (SOG) for COIL have been introduced, and the results from the tests that contacted on a 0.1mol/s SOG has been presented. The error in the chlorine utilization measurement is less than 12%. The additional experiment is needless that the error is minished because we can get the chlorine utilization by the ratio of relative intensity of Raman spectrum. So the measurement efficiency is improved.
2003,
15.
Abstract:
Pulsed laser induced ripple damage on an aluminum film mirror has been investigated from experiments. Ripples have been found at the periphery of damage site using atomforce microscope(AFM)，in most cases, several set of ripples appear at the same time in the same area. A laser interference theoretical model has been presented to explain pulsed laser induced ripples at the periphery of damage site in optical surface. This model assumes that the impurity grain or laser induced sphere-like distortion at the surface of optical sample reflects or scatters laser beam to its periphery area, and this reflected or scattered beam interferes with laser beam irradiated directly on this area. So the beam spatial profile becomes periodic and ripple damage morphology forms instantly. A simulated exper
Pulsed laser induced ripple damage on an aluminum film mirror has been investigated from experiments. Ripples have been found at the periphery of damage site using atomforce microscope(AFM)，in most cases, several set of ripples appear at the same time in the same area. A laser interference theoretical model has been presented to explain pulsed laser induced ripples at the periphery of damage site in optical surface. This model assumes that the impurity grain or laser induced sphere-like distortion at the surface of optical sample reflects or scatters laser beam to its periphery area, and this reflected or scattered beam interferes with laser beam irradiated directly on this area. So the beam spatial profile becomes periodic and ripple damage morphology forms instantly. A simulated exper
2003,
15.
Abstract:
From the electric field distribution and the phase shift requirement for the film, the mirror coating in COIL resonator at 45 deg incidence angle is designed using multiple frequency design method. A new high reflection design at two wavelengths (632.8nm and 1315nm) is attained with 180 deg phase retard at 1315nm. Compared with the conventional design, the thickness of high refractive index material of the new design is reduced largely. Hopefully, the performance of the mirror can be improved greatly.
From the electric field distribution and the phase shift requirement for the film, the mirror coating in COIL resonator at 45 deg incidence angle is designed using multiple frequency design method. A new high reflection design at two wavelengths (632.8nm and 1315nm) is attained with 180 deg phase retard at 1315nm. Compared with the conventional design, the thickness of high refractive index material of the new design is reduced largely. Hopefully, the performance of the mirror can be improved greatly.
2003,
15.
Abstract:
电子束; 离子辅助; 离子束溅射; 薄膜特性 The optical thin films, including single thin films of ZrO2, TiO2, Al2O3 and AR coatings, were respectively prepared by Ebeam, ion assisted deposition and ion beam sputtering. Then these thin films' properties were measured by several methods, such as profilemeter, atomic force microscopy, surface thermal lensing and Xray diffraction. The thin films' refractive index, surface roughness, absorption and microstructure were given and discussed. Finally, the conclusion was drawn: the option of proper technique to fabricate optical thin films is ion assisted deposition.
电子束; 离子辅助; 离子束溅射; 薄膜特性 The optical thin films, including single thin films of ZrO2, TiO2, Al2O3 and AR coatings, were respectively prepared by Ebeam, ion assisted deposition and ion beam sputtering. Then these thin films' properties were measured by several methods, such as profilemeter, atomic force microscopy, surface thermal lensing and Xray diffraction. The thin films' refractive index, surface roughness, absorption and microstructure were given and discussed. Finally, the conclusion was drawn: the option of proper technique to fabricate optical thin films is ion assisted deposition.
2003,
15.
Abstract:
The transformation of HermiteGaussian (HG) beams through a complicated optical system with multiple hardedged apertures is studied using Wen's method. A closedform propagation expression is derived which provides the main advantage of the fast algorithm, so that the computational time is great reduced. The propagation of Gaussian beams through such a type of optical system can be regarded as a special case in our theoretical model. Numerical examples of HG beams propagating through multiple aperturelens optical systems by using our formula are given, which show a good consistent with those by straightforward integral of the Collins formula. Further extension of the method and results obtained in this paper is discussed.
The transformation of HermiteGaussian (HG) beams through a complicated optical system with multiple hardedged apertures is studied using Wen's method. A closedform propagation expression is derived which provides the main advantage of the fast algorithm, so that the computational time is great reduced. The propagation of Gaussian beams through such a type of optical system can be regarded as a special case in our theoretical model. Numerical examples of HG beams propagating through multiple aperturelens optical systems by using our formula are given, which show a good consistent with those by straightforward integral of the Collins formula. Further extension of the method and results obtained in this paper is discussed.
2003,
15.
Abstract:
The generation of intense highspeed optical pulses has made possible a wide range of new experiments designed to study the characteristics of the optical pulse itself and the interaction of light with matter. For the quantitative and accurate measurement of the optical pulse parameters is essential, and it is the purpose of this paper to review the principles and characteristics of most methods currently available for measuring highspeed optical pulses (from nanosecond to attosecond), including electrooptical streak cameras, high speed pulses sampling, secondharmonic generation, frequencyresolved optical gating and spectral phase interferometry for direct electricfield reconstruction. Moreover, the recent rapid developments of these methods are also introduced. Some suggestions
The generation of intense highspeed optical pulses has made possible a wide range of new experiments designed to study the characteristics of the optical pulse itself and the interaction of light with matter. For the quantitative and accurate measurement of the optical pulse parameters is essential, and it is the purpose of this paper to review the principles and characteristics of most methods currently available for measuring highspeed optical pulses (from nanosecond to attosecond), including electrooptical streak cameras, high speed pulses sampling, secondharmonic generation, frequencyresolved optical gating and spectral phase interferometry for direct electricfield reconstruction. Moreover, the recent rapid developments of these methods are also introduced. Some suggestions
2003,
15.
Abstract:
After considering Kerr nonlinear effect, group velocity dispersion of host and gain distribution of active particle in laser amplifying medium, a basic equation describing the propagation of an optical pulse in laser amplifying medium has been deduced. Besides, the profile and power spectrum of a ps superGaussion pulse along Nd３＋：glass laser amplifying medium length have been disscussed when its central frequency coincides with peak frequency of gain of laser amplifying medium.
After considering Kerr nonlinear effect, group velocity dispersion of host and gain distribution of active particle in laser amplifying medium, a basic equation describing the propagation of an optical pulse in laser amplifying medium has been deduced. Besides, the profile and power spectrum of a ps superGaussion pulse along Nd３＋：glass laser amplifying medium length have been disscussed when its central frequency coincides with peak frequency of gain of laser amplifying medium.
Numerical simulation and scheme design for laser beam combination of stimulated Brillouin scattering
2003,
15.
Abstract:
A novel scheme for multistage serial stimulated Brillouin scattering(SBS) laser beam combination was presented and numerical simulations were made. In the scheme, six pumping beams with equal energy and pulse width pumped six SBS cells respectively, and a seed beam was injected and passed the six SBS cells in sequence. Numerical simulation shows that six KrF pumping beams with energy of 45J and pulse width of 23ns produce an output Stokes beam with energy of 141.89J and pulse width of 670ps. Numerical simulation also shows that shorter output pulse duration can be obtained, while medium gain is higher and phonon lifetime is shorter.
A novel scheme for multistage serial stimulated Brillouin scattering(SBS) laser beam combination was presented and numerical simulations were made. In the scheme, six pumping beams with equal energy and pulse width pumped six SBS cells respectively, and a seed beam was injected and passed the six SBS cells in sequence. Numerical simulation shows that six KrF pumping beams with energy of 45J and pulse width of 23ns produce an output Stokes beam with energy of 141.89J and pulse width of 670ps. Numerical simulation also shows that shorter output pulse duration can be obtained, while medium gain is higher and phonon lifetime is shorter.
2003,
15.
Abstract:
In this paper, computational code MFCG Ⅱ of the explosive magnetic field compression generator (MFCG) are developed based on the analytic formulas of magnetic field, current intensity and induced current for the process of charge and compression. Under the same conditions, computational results obtained by 2-D MHD MFCG Ⅱ code coincide with those obtained by 2-D MHD MFCG Ⅰ for the patterns of same parameters. Therefore , the concerned physical problems can be analysed and explained by MFCG Ⅱ in MFCG tests.
In this paper, computational code MFCG Ⅱ of the explosive magnetic field compression generator (MFCG) are developed based on the analytic formulas of magnetic field, current intensity and induced current for the process of charge and compression. Under the same conditions, computational results obtained by 2-D MHD MFCG Ⅱ code coincide with those obtained by 2-D MHD MFCG Ⅰ for the patterns of same parameters. Therefore , the concerned physical problems can be analysed and explained by MFCG Ⅱ in MFCG tests.
2003,
15.
Abstract:
Nanosized copper particles were prepared by flowlevitation method. The analyses based on transmission electron microscope (TEM) have been carried out in order to evaluate the average particle size of particles. The relationship between the average particle size and inert gases speed in different temperature and pressure has been established. Combining these characteristic curves, the manufacturing parameter can be obtained. The results shows that the particle size of nanosized copper gradually decreases by reduce the temperature of metal fused drop or increase gases speed. Moreover, to increase the inert gases pressure will deerease the average particle size at 1 200℃.
Nanosized copper particles were prepared by flowlevitation method. The analyses based on transmission electron microscope (TEM) have been carried out in order to evaluate the average particle size of particles. The relationship between the average particle size and inert gases speed in different temperature and pressure has been established. Combining these characteristic curves, the manufacturing parameter can be obtained. The results shows that the particle size of nanosized copper gradually decreases by reduce the temperature of metal fused drop or increase gases speed. Moreover, to increase the inert gases pressure will deerease the average particle size at 1 200℃.
2003,
15.
Abstract:
Distribution of electromagnetic field in the space of Htype RF ion source is researched theoretically. Threedimensional vector graphs of electric field intensity and magnetic induction density in the space of RF ion source are calculated and plotted by Mafia software. The conclusion that axial electric field intensity is more important during the breakdown of RF ion source is made out by comparing it and azimuthal electric field intensity before breakdown, and then, the breakdown criterion of RF ion source is calculated, which is reasonably in agreement with experimental data.
Distribution of electromagnetic field in the space of Htype RF ion source is researched theoretically. Threedimensional vector graphs of electric field intensity and magnetic induction density in the space of RF ion source are calculated and plotted by Mafia software. The conclusion that axial electric field intensity is more important during the breakdown of RF ion source is made out by comparing it and azimuthal electric field intensity before breakdown, and then, the breakdown criterion of RF ion source is calculated, which is reasonably in agreement with experimental data.
2003,
15.
Abstract:
In this paper, using the expanded fully relativistic multiconfiguration DiracFock code, we have calculated more than 200 fine-structure energy levels, radiative lifetime and various transition parameters in Mg-like ions Mn13+ and Zn18+, the results are in good agreement with the recent experimental data.
In this paper, using the expanded fully relativistic multiconfiguration DiracFock code, we have calculated more than 200 fine-structure energy levels, radiative lifetime and various transition parameters in Mg-like ions Mn13+ and Zn18+, the results are in good agreement with the recent experimental data.
2003,
15.
Abstract:
Electromagnetic field theory and electron motion conservation equations are used to derive numerical model of transverse spacecharge flow and magnetically insulated critical condition in conical transmission lines. Through numerical calculation, we have discussed the influence of the voltage and the cone's geometrical parameters on the transverse spacecharge flow and magnetically insulated performances. The higher the voltage is, the larger the spacecharge flow without magnetic field, and the better magnetically insutated performances. The geometrical factor K in the three geometrical parameters of the lines has the greatest influence on the transmission performances.
Electromagnetic field theory and electron motion conservation equations are used to derive numerical model of transverse spacecharge flow and magnetically insulated critical condition in conical transmission lines. Through numerical calculation, we have discussed the influence of the voltage and the cone's geometrical parameters on the transverse spacecharge flow and magnetically insulated performances. The higher the voltage is, the larger the spacecharge flow without magnetic field, and the better magnetically insutated performances. The geometrical factor K in the three geometrical parameters of the lines has the greatest influence on the transmission performances.
2003,
15.
Abstract:
Two new methods using metastable helium atomic beam to fabricate nanostructures are introduced. A metastable helium atomic beam effusing out of atom source is firstly cooled by transversally in cident laser. This well-collimated atomic beam traveling through the light standingwave whose direction is perpendicular to atomic beam is quenched, and channeling effect happens in atomic density distribution. In this paper the basic principle of this technique based on mask made of light and theoretical analysis as well as simulation results are given. The principle of another method based on physical mask and SAM(selfassembled monolayers) resists are presented, the SAM on substrate is destroyed by deposited metastable atoms on substrate, and the nanometer-scale structure will be fabricated wi
Two new methods using metastable helium atomic beam to fabricate nanostructures are introduced. A metastable helium atomic beam effusing out of atom source is firstly cooled by transversally in cident laser. This well-collimated atomic beam traveling through the light standingwave whose direction is perpendicular to atomic beam is quenched, and channeling effect happens in atomic density distribution. In this paper the basic principle of this technique based on mask made of light and theoretical analysis as well as simulation results are given. The principle of another method based on physical mask and SAM(selfassembled monolayers) resists are presented, the SAM on substrate is destroyed by deposited metastable atoms on substrate, and the nanometer-scale structure will be fabricated wi
2003,
15.
Abstract:
This paper gives a description of the principle of the magnetic gap control system of the optical klystron for the coherent harmonic generation storage-ring free-electron laser in the National Synchrotron Radiation Laboratory. The hardware construction and software flowchart are illustrated for reliably engineering implementation of the system. The three parts of optical klystron, modulator, dispersive section and radiator can be adjusted separately or simultaneously, and the resolution can reach 20μm and the precision 5μm. By means of optimizing the position monitoring instrument of the system, the resolution and the precision can be improved to 1.0μm and 0.2μm respectively. The vacuum chamber of the storage ring between the optical klystron is free of destruction by multi-protection
This paper gives a description of the principle of the magnetic gap control system of the optical klystron for the coherent harmonic generation storage-ring free-electron laser in the National Synchrotron Radiation Laboratory. The hardware construction and software flowchart are illustrated for reliably engineering implementation of the system. The three parts of optical klystron, modulator, dispersive section and radiator can be adjusted separately or simultaneously, and the resolution can reach 20μm and the precision 5μm. By means of optimizing the position monitoring instrument of the system, the resolution and the precision can be improved to 1.0μm and 0.2μm respectively. The vacuum chamber of the storage ring between the optical klystron is free of destruction by multi-protection
