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RSS2000 Vol. 12, No. 06
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2000,
12.
Abstract:
The power spectral density (PSD) was used to be the specific standard of the large aperture optical components. Its definition and calculation has analyzed in detail, and the results were given consequently. And we discussed how to calculate the averaged PSD in deferent situation was discussed.
The power spectral density (PSD) was used to be the specific standard of the large aperture optical components. Its definition and calculation has analyzed in detail, and the results were given consequently. And we discussed how to calculate the averaged PSD in deferent situation was discussed.
2000,
12.
Abstract:
Six- and ten-state close-coupling calculations are carried out by using the R-matrix method to obtain photoionization cross section of the ground state of C II ion. The incident photon energy ranges from 1.8Ry to 4.3Ry. The calculated results in Length and Velocity formulations agree very well. The cross sections contain complicated resonance structure. Our results are also in good agreement with those of the Opacity Project. The difference between the six-and ten-state close-coupling calculations shows that the resonance series converging to higher ionization thresholds will disturb the lower Rydberg resonances. The energy levels of singly and doubly excited states can be determined by the resonance structures of partial and individual cross sections.
Six- and ten-state close-coupling calculations are carried out by using the R-matrix method to obtain photoionization cross section of the ground state of C II ion. The incident photon energy ranges from 1.8Ry to 4.3Ry. The calculated results in Length and Velocity formulations agree very well. The cross sections contain complicated resonance structure. Our results are also in good agreement with those of the Opacity Project. The difference between the six-and ten-state close-coupling calculations shows that the resonance series converging to higher ionization thresholds will disturb the lower Rydberg resonances. The energy levels of singly and doubly excited states can be determined by the resonance structures of partial and individual cross sections.
2000,
12.
Abstract:
Partially coherent Gaussian beams which can be expanded into an independent superposition of Hermite-Gaussian modes have been analyzed. The analytical expressions for the mode coefficients, the weighting factors and the M2-factor of partially coherent Gaussian beams have been derived. Relation of weighting factors and M2-factor has been discussed. It can be shown from the research work that the mode coefficients, the M2-factor and the mode structure can be determined by means of intensity detection.
Partially coherent Gaussian beams which can be expanded into an independent superposition of Hermite-Gaussian modes have been analyzed. The analytical expressions for the mode coefficients, the weighting factors and the M2-factor of partially coherent Gaussian beams have been derived. Relation of weighting factors and M2-factor has been discussed. It can be shown from the research work that the mode coefficients, the M2-factor and the mode structure can be determined by means of intensity detection.
2000,
12.
Abstract:
A simplified blur model of luminescent glass screen caused by Compton electron scattering is set up based on the Compton scattering theory. The influence of the screen thickness on the screen spatial resolution is given through numerical analysis. Then the screen spatial resolution is experimentally measured by an experiment carried out on 12 MeV linear accelerator, and the result accord with the calculated ones.
A simplified blur model of luminescent glass screen caused by Compton electron scattering is set up based on the Compton scattering theory. The influence of the screen thickness on the screen spatial resolution is given through numerical analysis. Then the screen spatial resolution is experimentally measured by an experiment carried out on 12 MeV linear accelerator, and the result accord with the calculated ones.
2000,
12.
Abstract:
The propagation property of Gaussian beam traveling through graded-index media with Kerr nonlinearity is investigated using the aberrationless theory of self-focusing. Expressions for the spot size and the beam radius of curvature of Gaussian beam are obtained. It is shown that the propagation property of Gaussian beams depends on the competition between the diffraction effect and the combined effect of nonlinearity and graded-index. The graded-index tends to shorten the self-focusing distance.
The propagation property of Gaussian beam traveling through graded-index media with Kerr nonlinearity is investigated using the aberrationless theory of self-focusing. Expressions for the spot size and the beam radius of curvature of Gaussian beam are obtained. It is shown that the propagation property of Gaussian beams depends on the competition between the diffraction effect and the combined effect of nonlinearity and graded-index. The graded-index tends to shorten the self-focusing distance.
2000,
12.
Abstract:
One key step for full field correction is to match the main laser amplitude distribution with beacon amplitude distribution on deformable mirror 2 in two-deformable-mirror adaptive optics. Amplitude and phase corrections for turbulence are studied based on Y-G wavefront retrieval algorithms. The results show that full field corrections can improve Strehl ratio by a factor of 1.27 to 2.50 compared with phase-only correction. For a distance of 10m between deformable mirror1 and deformable mirror 2, the factor is from 1.13 to 1.50.
One key step for full field correction is to match the main laser amplitude distribution with beacon amplitude distribution on deformable mirror 2 in two-deformable-mirror adaptive optics. Amplitude and phase corrections for turbulence are studied based on Y-G wavefront retrieval algorithms. The results show that full field corrections can improve Strehl ratio by a factor of 1.27 to 2.50 compared with phase-only correction. For a distance of 10m between deformable mirror1 and deformable mirror 2, the factor is from 1.13 to 1.50.
2000,
12.
Abstract:
A method to describe the frequency conversion of aberrated beams was develiped. Based on the statistical optics method, the second harmonic generation of phase-aberrted beams with thin crystal and a Gaussian random variable phase aberration .were investigated. The calculated results of the fundamental wave and the second harmonic wave with the profiles of non-uniform and aberrated phase ae given in detail.
A method to describe the frequency conversion of aberrated beams was develiped. Based on the statistical optics method, the second harmonic generation of phase-aberrted beams with thin crystal and a Gaussian random variable phase aberration .were investigated. The calculated results of the fundamental wave and the second harmonic wave with the profiles of non-uniform and aberrated phase ae given in detail.
2000,
12.
Abstract:
Analysis of phase difference of spherical laser window is presented, which includes unequality of optical path caused by window itself and disuniformity of refration index and strain caused by thermal and photoelastic effects. The distribution of phase difference is calculated with differential method. It indicates that choice of window parameters influence the distribution of phase serious. The optimal parameters of laser window can be given based on thermal and photoelastic effects according to center intensity of far field beam to minimize the influence on beam quality.
Analysis of phase difference of spherical laser window is presented, which includes unequality of optical path caused by window itself and disuniformity of refration index and strain caused by thermal and photoelastic effects. The distribution of phase difference is calculated with differential method. It indicates that choice of window parameters influence the distribution of phase serious. The optimal parameters of laser window can be given based on thermal and photoelastic effects according to center intensity of far field beam to minimize the influence on beam quality.
2000,
12.
Abstract:
The melt depth and liquid/solid interface move velocity during the laser induced periodic structure were numerical calculated by laser heating model. The melt and re-solidify phenomena of the substrate is investigated, the origination laser induced periodic structure is Rayleight-Taylor instability, and the spatial period is calculated by hydrodynamic equations.
The melt depth and liquid/solid interface move velocity during the laser induced periodic structure were numerical calculated by laser heating model. The melt and re-solidify phenomena of the substrate is investigated, the origination laser induced periodic structure is Rayleight-Taylor instability, and the spatial period is calculated by hydrodynamic equations.
2000,
12.
Abstract:
In this work the electron state of Cu and Au clusters obtained by plused laser deposition on surface of Ni, Mo, C and NaCl(100) was studied by X-ray photoelectron spectroscopy(XPS); The initial and final state contributions of electron binding energy were separated by combination of XPS peak Cu2p3/2 and Cu L3M4,5M4,5 Auger transition, their relationship with Cu surface atomic concentration was obtained and the explanation was given. XPS, RBS and TEM were used to study the growth of Au clusters on the surface of NaCl(100), average height and surface coverage of Au clusters at different surface atomic concentration were obtained by calculations.
In this work the electron state of Cu and Au clusters obtained by plused laser deposition on surface of Ni, Mo, C and NaCl(100) was studied by X-ray photoelectron spectroscopy(XPS); The initial and final state contributions of electron binding energy were separated by combination of XPS peak Cu2p3/2 and Cu L3M4,5M4,5 Auger transition, their relationship with Cu surface atomic concentration was obtained and the explanation was given. XPS, RBS and TEM were used to study the growth of Au clusters on the surface of NaCl(100), average height and surface coverage of Au clusters at different surface atomic concentration were obtained by calculations.
2000,
12.
Abstract:
Angular separation of real zenith angle beacon and project laser due to atmospheric dispersion is calculated in this paper. Several factors, such as weather, site, project zenith angle and beacon wavelength, are under consideration. Project zenith angle and beacon wavelength have much influence on the angular separation. Weather and site have relatively less influence on the angular separation. The larger the project zenith angle is, the larger the angular separation is. Beacon wavelength should be close to the wavelength of the project laser and longer wavelength is profitable.
Angular separation of real zenith angle beacon and project laser due to atmospheric dispersion is calculated in this paper. Several factors, such as weather, site, project zenith angle and beacon wavelength, are under consideration. Project zenith angle and beacon wavelength have much influence on the angular separation. Weather and site have relatively less influence on the angular separation. The larger the project zenith angle is, the larger the angular separation is. Beacon wavelength should be close to the wavelength of the project laser and longer wavelength is profitable.
2000,
12.
Abstract:
This paper presents theoretical and experimental researches on the effects of axial guiding magnetic field on microwave power radiated from relativistic backward oscillators. 2.5 dimensions particle-in-cell numerical simulations were done at first. When magnetic field falls the competition between TE mode and TM01 mode contributes to decrease the pulse power of microwave. In addition, cyclotron resonant absorbing was observed. Experiments were made then, which demonstrates that the experimental results are consistent with those of numerical simulation in some degree.
This paper presents theoretical and experimental researches on the effects of axial guiding magnetic field on microwave power radiated from relativistic backward oscillators. 2.5 dimensions particle-in-cell numerical simulations were done at first. When magnetic field falls the competition between TE mode and TM01 mode contributes to decrease the pulse power of microwave. In addition, cyclotron resonant absorbing was observed. Experiments were made then, which demonstrates that the experimental results are consistent with those of numerical simulation in some degree.
2000,
12.
Abstract:
The method of moment based on voltage integral equation is described. It can be used to calculate the capacitance of multiconductor transmission lines with circular section. The computed results of three types of shielded cables with one or multiple inner conductors are presented.
The method of moment based on voltage integral equation is described. It can be used to calculate the capacitance of multiconductor transmission lines with circular section. The computed results of three types of shielded cables with one or multiple inner conductors are presented.
2000,
12.
Abstract:
To realize the requirement of SASE FEL to electron beam, this paper optimizes the design of photo-cathode RF gun and considers the emittance compensation techniques specifically. It also makes the simulation of the particle dynamics with PARMELA. At last it gives out the optimized parameters of the initialized electron beam to minimize the normalized transverse emittance.
To realize the requirement of SASE FEL to electron beam, this paper optimizes the design of photo-cathode RF gun and considers the emittance compensation techniques specifically. It also makes the simulation of the particle dynamics with PARMELA. At last it gives out the optimized parameters of the initialized electron beam to minimize the normalized transverse emittance.
2000,
12.
Abstract:
The finite-difference time-domain method is used to research the rule of the transient electromagnetic field coupled to the cavity that has many apetures on it. The coupling effects of different bandwidth and different polarized direction are described in this paper. When the polarized direction of the incident wave are parallel to the short side of the apeture, the coupled energy will attain the maximum. If the bandwith and the risetime are shorter, then the energy coupled to the cavity are greater.
The finite-difference time-domain method is used to research the rule of the transient electromagnetic field coupled to the cavity that has many apetures on it. The coupling effects of different bandwidth and different polarized direction are described in this paper. When the polarized direction of the incident wave are parallel to the short side of the apeture, the coupled energy will attain the maximum. If the bandwith and the risetime are shorter, then the energy coupled to the cavity are greater.
2000,
12.
Abstract:
As the driving laser of photoinjector, there are many hard requirements, for example the low timing jitter (<2ps), the narrow pulse width, the high peak power, and etc. According to its characters, the paper discusses the Driving Laser of CAEP Photoinjector, which is made of the oscillator, timing stabilizer, the amplifier, and etc. The theoretical analysis and some experimental results are also presented in the paper.
As the driving laser of photoinjector, there are many hard requirements, for example the low timing jitter (<2ps), the narrow pulse width, the high peak power, and etc. According to its characters, the paper discusses the Driving Laser of CAEP Photoinjector, which is made of the oscillator, timing stabilizer, the amplifier, and etc. The theoretical analysis and some experimental results are also presented in the paper.
2000,
12.
Abstract:
The design idea, the characteristic parameters and the beam dynamical result of a novel 4+1/2 cells microwave electron gun are presented in this paper. 400~ 1000mA of the macropulse current, 1~ 2kW average electron beam power and duty factor 1 10- 3 have been achieved when the inputted microwave source power is 3.2MW.
The design idea, the characteristic parameters and the beam dynamical result of a novel 4+1/2 cells microwave electron gun are presented in this paper. 400~ 1000mA of the macropulse current, 1~ 2kW average electron beam power and duty factor 1 10- 3 have been achieved when the inputted microwave source power is 3.2MW.
2000,
12.
Abstract:
With the help of electron cooling code, the influence of the main parameters of electron cooling device on the cooling time was simulated, cooling times of 238U91+ ion with the energy 400MeV/u at different parameters were calculated, and the factors which influence the cooling time were analyzed in this paper.
With the help of electron cooling code, the influence of the main parameters of electron cooling device on the cooling time was simulated, cooling times of 238U91+ ion with the energy 400MeV/u at different parameters were calculated, and the factors which influence the cooling time were analyzed in this paper.
2000,
12.
Abstract:
Beam Breakup (BBU) Instabilities resulted from interaction of beam and cavity will deteriorate beam quality. Transverse impedances reflect the degree of such interaction. This paper reports the result of simulation of transverse impedances of three different induction accelerating cavities. the calculated impedances using MAFIA fit to the measured impedances very well.
Beam Breakup (BBU) Instabilities resulted from interaction of beam and cavity will deteriorate beam quality. Transverse impedances reflect the degree of such interaction. This paper reports the result of simulation of transverse impedances of three different induction accelerating cavities. the calculated impedances using MAFIA fit to the measured impedances very well.
2000,
12.
Abstract:
A therapy beam energy range is 6-16MeV dual photon Linac with RF power feedback has been developed. Its maximum radiation field is 40cm 40cm and the dual photon dose rate are more than 360 cGy / (min× m). The design concept and design performances of HM-J16 accelerator are briefly described in this paper.
A therapy beam energy range is 6-16MeV dual photon Linac with RF power feedback has been developed. Its maximum radiation field is 40cm 40cm and the dual photon dose rate are more than 360 cGy / (min× m). The design concept and design performances of HM-J16 accelerator are briefly described in this paper.
2000,
12.
Abstract:
An analysis of principle of a biased Faraday cup for measuring ion beams density and the main reasons related to the measuring accuracy were presented. An array of mini biased collimated Faraday cups was manufactured for the measurement of ion beam density of a compact 200kV high power ion beam source. In the experiments the maximum density of ion beam was in the center of the beam, and it was about 170A/cm2.
An analysis of principle of a biased Faraday cup for measuring ion beams density and the main reasons related to the measuring accuracy were presented. An array of mini biased collimated Faraday cups was manufactured for the measurement of ion beam density of a compact 200kV high power ion beam source. In the experiments the maximum density of ion beam was in the center of the beam, and it was about 170A/cm2.
2000,
12.
Abstract:
The dielectric ring thickness of pinch-reflex ion diode is roughly calculated, the effect of dielectric ring thickness of 200kV pinch-reflex ion diode on ion beams and diode electric parameters is studied. The experimental results show when dielectric ring thickness in the range of 2~3mm the accelerator system can work in good condition with high ion beam and total beam currents.
The dielectric ring thickness of pinch-reflex ion diode is roughly calculated, the effect of dielectric ring thickness of 200kV pinch-reflex ion diode on ion beams and diode electric parameters is studied. The experimental results show when dielectric ring thickness in the range of 2~3mm the accelerator system can work in good condition with high ion beam and total beam currents.
2000,
12.
Abstract:
According to the simulation results with MAFIA code, The cooling system of the new B1 Buncher cavity has been introduced. With the aide of the constant thermo-flux model, the temperature distribution, the total discharge and the highest temperature have been calculated, the decrease of shunt impendence and the shift of the resonate frequency due to temperature increase have been discussed also.
According to the simulation results with MAFIA code, The cooling system of the new B1 Buncher cavity has been introduced. With the aide of the constant thermo-flux model, the temperature distribution, the total discharge and the highest temperature have been calculated, the decrease of shunt impendence and the shift of the resonate frequency due to temperature increase have been discussed also.
2000,
12.
Abstract:
An analytical method has been used to study the non-uniformity of plane radiation field produced by lasers heating hohlraum. The results given by this method are well consistent with that given by numerical simulation. The scale of hohlraum which can produce plane radiation field with minimum radiation non-uniformity was predicted by this means.
An analytical method has been used to study the non-uniformity of plane radiation field produced by lasers heating hohlraum. The results given by this method are well consistent with that given by numerical simulation. The scale of hohlraum which can produce plane radiation field with minimum radiation non-uniformity was predicted by this means.
2000,
12.
Abstract:
Based on Fourier Optics，an analytic expression of diffraction efficiency is deduced from the scale diffraction theory. Moreover， the diffraction efficiency of CSG corresponding to fabrication errors is analyzed systematically and simulated using computer. The results of simulation provide theoretical instructions for practical fabrications.
Based on Fourier Optics，an analytic expression of diffraction efficiency is deduced from the scale diffraction theory. Moreover， the diffraction efficiency of CSG corresponding to fabrication errors is analyzed systematically and simulated using computer. The results of simulation provide theoretical instructions for practical fabrications.
2000,
12.
Abstract:
Transmission grating efficiencies for soft x rays at several photon energies were calibrated on Beijing Synchrotron Radiation Facility, and the experimental results have been obtained. Then, a new model was developed to simulate the calibrated grating efficiencies, which the grating wires were assumed to have quasi-trapezoidal cross sections. Model calculations are in good agreement with the experimental results.
Transmission grating efficiencies for soft x rays at several photon energies were calibrated on Beijing Synchrotron Radiation Facility, and the experimental results have been obtained. Then, a new model was developed to simulate the calibrated grating efficiencies, which the grating wires were assumed to have quasi-trapezoidal cross sections. Model calculations are in good agreement with the experimental results.
2000,
12.
Abstract:
In the paper, the principle of the scattering technique was applied in measuring the total X-ray dose and The filter-fluorescence was applied in measuring the X-ray spectrum on high-temperature plasma was described. The method of dealing with the X-ray spectrum and the total X-ray dose was established. The result of the experiment was got Successfully. The uncertainty of the total X-ray dose at the measuring spot was about ± 23%.
In the paper, the principle of the scattering technique was applied in measuring the total X-ray dose and The filter-fluorescence was applied in measuring the X-ray spectrum on high-temperature plasma was described. The method of dealing with the X-ray spectrum and the total X-ray dose was established. The result of the experiment was got Successfully. The uncertainty of the total X-ray dose at the measuring spot was about ± 23%.
2000,
12.
Abstract:
This paper introduced the principle of the Fresnel-zone-plate coded imaging, and design a Fresnel zone plate coded image camera with high spatial resolution. A experimental simulation with two-aperture visible light source is made. The result shows that this coded image camera can reveal the source distribution truly.
This paper introduced the principle of the Fresnel-zone-plate coded imaging, and design a Fresnel zone plate coded image camera with high spatial resolution. A experimental simulation with two-aperture visible light source is made. The result shows that this coded image camera can reveal the source distribution truly.
2000,
12.
Abstract:
The technological processes of polystyrene (PS) initial granules and the hollow microshells formed on a vertical drop furnace from the granules dealt with a foamer are investigated. The initial granules are produced by one step emulsion techniques. Influences of phase ratio and stirring intensity on diameter distributions of initial granuales are discussed., and alcohol is selected as a foamer according to the boiling point and solubility. Then effects of temperatures、gaseous compositions and pressures inside the furnace on the quality of PS microshells fabricated from the granules are experimented. As a result, optimal conditions are selected to make PS microshells with outer diameters of 400～900m m , wall-thickness of 2~10m m and concentricity better than 95%.
The technological processes of polystyrene (PS) initial granules and the hollow microshells formed on a vertical drop furnace from the granules dealt with a foamer are investigated. The initial granules are produced by one step emulsion techniques. Influences of phase ratio and stirring intensity on diameter distributions of initial granuales are discussed., and alcohol is selected as a foamer according to the boiling point and solubility. Then effects of temperatures、gaseous compositions and pressures inside the furnace on the quality of PS microshells fabricated from the granules are experimented. As a result, optimal conditions are selected to make PS microshells with outer diameters of 400～900m m , wall-thickness of 2~10m m and concentricity better than 95%.
2000,
12.
Abstract:
Time-resolved Thomson scattering was successfully performed to diagnose the parameters of laser-produced gold plasma.The time dependence of and ion drift velocity ui was also obtained to benchmark hydrodynamic simulations.
Time-resolved Thomson scattering was successfully performed to diagnose the parameters of laser-produced gold plasma.The time dependence of and ion drift velocity ui was also obtained to benchmark hydrodynamic simulations.
