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RSS2003 Vol. 15, No. 08
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2003,
15.
Abstract:
Cooling force in electron cooling system is closely related to the temperature of electron beam. The velocity of electron has the offset due to space charge of intense electron beam. In order to minimize this effect, a new type of electron gun to produce the hollow electron beam is firstly adopted in HIRFLCSR ecooler project. The hot ion beam is cooled by Coulomb interaction with intense and cold hollow electron beams. By analysis of space charge effect of solid and hollow electron beam respectively, the impact on the electron velocity and additional temperature due to the space charge field are preliminarily investigated.
Cooling force in electron cooling system is closely related to the temperature of electron beam. The velocity of electron has the offset due to space charge of intense electron beam. In order to minimize this effect, a new type of electron gun to produce the hollow electron beam is firstly adopted in HIRFLCSR ecooler project. The hot ion beam is cooled by Coulomb interaction with intense and cold hollow electron beams. By analysis of space charge effect of solid and hollow electron beam respectively, the impact on the electron velocity and additional temperature due to the space charge field are preliminarily investigated.
2003,
15.
Abstract:
The paper presents an upgraded close orbit distortion(COD) system and its application in phase II project of HLS, and introduces Bergoz's modules for COD signal process. The upgraded COD system, with resolution of processing electronics circuit up to 1μm and repetition error of system not greater than 10μm, is operated in routine. The measurement of dispersion validated the reliability of upgraded COD system. We have completed to position the beam in the magnetic center of a quadrupole using the high precision COD system and the beam based alignment system. We have accomplished global close orbit correction system and its application on line. The improved beam quality can provide a stable light source for users.
The paper presents an upgraded close orbit distortion(COD) system and its application in phase II project of HLS, and introduces Bergoz's modules for COD signal process. The upgraded COD system, with resolution of processing electronics circuit up to 1μm and repetition error of system not greater than 10μm, is operated in routine. The measurement of dispersion validated the reliability of upgraded COD system. We have completed to position the beam in the magnetic center of a quadrupole using the high precision COD system and the beam based alignment system. We have accomplished global close orbit correction system and its application on line. The improved beam quality can provide a stable light source for users.
2003,
15.
Abstract:
The accelerating tube is one of the most important parts in high current implanter which provides the desired energy and focusing for ion beam.The factors affecting focus characteristic in high current implanter with three gap acceleration tube are discussed. focusing degrees of different energy ion beam are computed, and the electric field required to prevent beam expansion due to space charge effect are analyzed. The beam envelope inside the three acceleration gap shows a decrease of the beam radius with the increase of the accelerating voltage ratio up to the optimal value. Beyond this optimal value the beam lines make a crossover with the axis of the accelerating tube.
The accelerating tube is one of the most important parts in high current implanter which provides the desired energy and focusing for ion beam.The factors affecting focus characteristic in high current implanter with three gap acceleration tube are discussed. focusing degrees of different energy ion beam are computed, and the electric field required to prevent beam expansion due to space charge effect are analyzed. The beam envelope inside the three acceleration gap shows a decrease of the beam radius with the increase of the accelerating voltage ratio up to the optimal value. Beyond this optimal value the beam lines make a crossover with the axis of the accelerating tube.
2003,
15.
Abstract:
Electromagnetic field theory and electron motion conservation equations are used to derive numerical model of transverse space-charge flow and magnetically insulated critical condition in plane and cylinder transmission lines. Through numerical simulation, this paper discusses discussed the influence of the voltage and the geometrical parameters on the transverse spacecharge flow and magnetically insulated performances.
Electromagnetic field theory and electron motion conservation equations are used to derive numerical model of transverse space-charge flow and magnetically insulated critical condition in plane and cylinder transmission lines. Through numerical simulation, this paper discusses discussed the influence of the voltage and the geometrical parameters on the transverse spacecharge flow and magnetically insulated performances.
2003,
15.
Abstract:
It is well known that the beam directly out of the thermionic cathode RFgun is not suitable for injection into a linear accelerator section. This kind of injection would produce an accelerated beam with a large energy spread because of the large phase-spread the particles coming into the accelerator section would have in the absence of compression. Magnetic bunch compression is one solution to this problem, and is most suitable for RF gun. In this paper, an alpha magnet is described, which is an asymmetric quadrupole. The scaled equation of motion and ideal trajectory in an alpha magnet are presented, and how the scaled form of the differential equation can be used to deduce some of the magnet's properties with numerical calculation method is shown.
It is well known that the beam directly out of the thermionic cathode RFgun is not suitable for injection into a linear accelerator section. This kind of injection would produce an accelerated beam with a large energy spread because of the large phase-spread the particles coming into the accelerator section would have in the absence of compression. Magnetic bunch compression is one solution to this problem, and is most suitable for RF gun. In this paper, an alpha magnet is described, which is an asymmetric quadrupole. The scaled equation of motion and ideal trajectory in an alpha magnet are presented, and how the scaled form of the differential equation can be used to deduce some of the magnet's properties with numerical calculation method is shown.
2003,
15.
Abstract:
This paper numerically studies the coupling of the ultrawide band electromagnetic pulse into mines. Some typical coupling results are presented for different incident angles and distances from the antenna to the mine. In order to investigate the coupling problem, this paper studies the perfectly marched layer used to truncate the lossy boundary, and provides the distributions of the electric field radiated from the TEM horn antenna fed by the UWB signal.
This paper numerically studies the coupling of the ultrawide band electromagnetic pulse into mines. Some typical coupling results are presented for different incident angles and distances from the antenna to the mine. In order to investigate the coupling problem, this paper studies the perfectly marched layer used to truncate the lossy boundary, and provides the distributions of the electric field radiated from the TEM horn antenna fed by the UWB signal.
2003,
15.
Abstract:
Primary investigation of X-ray Gabor zone plate coded imaging was performed based on the Xingguang II facility. Special designed CH foil burying W thread targets was irradiated with 3ω0 Nd laser large spot smoothing radition to generate a certain shape Plasma and special developed binary Gabor zone plate encode holography camera was used the image it. Integrate two shots with placing target in different position in z direction one got holograms come from plasma with certain 3D structure. Typical hologram was decoded with numerical reconstruction technique. Expected result was obtained.
Primary investigation of X-ray Gabor zone plate coded imaging was performed based on the Xingguang II facility. Special designed CH foil burying W thread targets was irradiated with 3ω0 Nd laser large spot smoothing radition to generate a certain shape Plasma and special developed binary Gabor zone plate encode holography camera was used the image it. Integrate two shots with placing target in different position in z direction one got holograms come from plasma with certain 3D structure. Typical hologram was decoded with numerical reconstruction technique. Expected result was obtained.
2003,
15.
Abstract:
When the laser driver for ICF works in the case of 3ns long pulse, the effect of transverse stimulated Raman scattering in tripler is more significant than that in the case of short pulse. This paper studies the damage of transverse stimulated Raman scattering in KD*P is compared with that in KDP and the relation between the effect of transverse stimulated Raman scatterin and gain coefficient. Therefore, it poesents theoretical evidences for choosing which type of crystal as tripler.
When the laser driver for ICF works in the case of 3ns long pulse, the effect of transverse stimulated Raman scattering in tripler is more significant than that in the case of short pulse. This paper studies the damage of transverse stimulated Raman scattering in KD*P is compared with that in KDP and the relation between the effect of transverse stimulated Raman scatterin and gain coefficient. Therefore, it poesents theoretical evidences for choosing which type of crystal as tripler.
2003,
15.
Abstract:
Investigation of Xray ring aperture coded imaging technique is performed aimed at the application of inertial confinement fusion research. The autocorrelations function of a ring aperture is calculated numerically. The effect of the function on the image reconstruction in the coded imaging is analyzed. A primary comparison of different image reconstruction treatment is gaven. Ring aperture coded imaging could have a better spatial resolution than the width of the ring with deconvolution reconstruction technique. Experimental demonstration of laser plasma Xray ring aperture coded imaging is performed on the Xingguang II facility and content results are obtained.
Investigation of Xray ring aperture coded imaging technique is performed aimed at the application of inertial confinement fusion research. The autocorrelations function of a ring aperture is calculated numerically. The effect of the function on the image reconstruction in the coded imaging is analyzed. A primary comparison of different image reconstruction treatment is gaven. Ring aperture coded imaging could have a better spatial resolution than the width of the ring with deconvolution reconstruction technique. Experimental demonstration of laser plasma Xray ring aperture coded imaging is performed on the Xingguang II facility and content results are obtained.
2003,
15.
Abstract:
The CH film is widely used in the inertial confinement fusion experiment for its excellent properties especially for the plasma and X-ray diagnoses. There are many methods to produce the CH film, and different method will lead to different application in the target fabrication. The method of hot wire assistance chemical vapor deposition to produce the CH film can enhance the deposition rate and keep low substrate temperature. This paper focuses on the effects of the hotwire current on the deposition rate and the surface morphology of the CH film. Experiments show that the deposition rate increases and the film surface roughness increases when the current increases. Based on these experiments the film production mechanism is discussed.
The CH film is widely used in the inertial confinement fusion experiment for its excellent properties especially for the plasma and X-ray diagnoses. There are many methods to produce the CH film, and different method will lead to different application in the target fabrication. The method of hot wire assistance chemical vapor deposition to produce the CH film can enhance the deposition rate and keep low substrate temperature. This paper focuses on the effects of the hotwire current on the deposition rate and the surface morphology of the CH film. Experiments show that the deposition rate increases and the film surface roughness increases when the current increases. Based on these experiments the film production mechanism is discussed.
2003,
15.
Abstract:
Measurement of radiation field near a implosion pellet M band Xray is a important area in ICF research.On the “SGⅡ” laser facility, M band Xray from Au plasma was measured in half hohlraum radiation from a hole about 200μm at the end. The experiment setup and typical results were given. The results indicate that angular distribution of M band Xray from the hole at the end of half hohlraum doesn't assume linear relationship with the cosine of eradiating angle, but angular distribution of O band Xray from the half hohlraum entry does.The results are very useful for the research of implosion experiment and target design.
Measurement of radiation field near a implosion pellet M band Xray is a important area in ICF research.On the “SGⅡ” laser facility, M band Xray from Au plasma was measured in half hohlraum radiation from a hole about 200μm at the end. The experiment setup and typical results were given. The results indicate that angular distribution of M band Xray from the hole at the end of half hohlraum doesn't assume linear relationship with the cosine of eradiating angle, but angular distribution of O band Xray from the half hohlraum entry does.The results are very useful for the research of implosion experiment and target design.
2003,
15.
Abstract:
There are a number of high altitude nuclear electromagnetic pulse (HEMP) waveform standards for equipment and systems on susceptibility to the testing effects. These typical HEMP standards include IEC6100029, MILSTD461E and some other publication standards such as Bell Laboratory's etc. The time domain parameters, amplitude spectrum, and the cumulative energy fluence of these HEMP waveforms are compared in this paper. The results show that earlytime HEMP in IEC6100029(equals to MILSTD461E) is less severe than HEMP in the 'publication 1976' and Bell laboratory standard except for slots coupling as the former have slightly shorter rise time and more wide 3dB bandwidth. In the end, the influence on the HEMP simulation and effects due to the change of HEMP standard are also
There are a number of high altitude nuclear electromagnetic pulse (HEMP) waveform standards for equipment and systems on susceptibility to the testing effects. These typical HEMP standards include IEC6100029, MILSTD461E and some other publication standards such as Bell Laboratory's etc. The time domain parameters, amplitude spectrum, and the cumulative energy fluence of these HEMP waveforms are compared in this paper. The results show that earlytime HEMP in IEC6100029(equals to MILSTD461E) is less severe than HEMP in the 'publication 1976' and Bell laboratory standard except for slots coupling as the former have slightly shorter rise time and more wide 3dB bandwidth. In the end, the influence on the HEMP simulation and effects due to the change of HEMP standard are also
2003,
15.
Abstract:
of diode are studied numerically in this paper. The results show that the beam generated by the diode has an energy spread，even with constant applied voltage. Additionally, external magnetic field has great but reverse influence on the impedance of lowimpedance diode, which is, according to the author's analysis, the result of the change of the electron's track due to external magnetic field. If the beam current is less than the critical one for selfpinch, the impedance will be constant with the variation of external magnetic field.The energy spectrum of the electron beam generated by lowimpedance diode and the influence of external magnetic field on the impedance
of diode are studied numerically in this paper. The results show that the beam generated by the diode has an energy spread，even with constant applied voltage. Additionally, external magnetic field has great but reverse influence on the impedance of lowimpedance diode, which is, according to the author's analysis, the result of the change of the electron's track due to external magnetic field. If the beam current is less than the critical one for selfpinch, the impedance will be constant with the variation of external magnetic field.The energy spectrum of the electron beam generated by lowimpedance diode and the influence of external magnetic field on the impedance
2003,
15.
Abstract:
This paper numerically studies the coupling of the ultrawide band electromagnetic pulse into mines. Some typical coupling results are presented for different incident angles and distances from the antenna to the mine. In order to investigate the coupling problem, this paper studies the perfectly marched layer used to truncate the lossy boundary, and provides the distributions of the electric field radiated from the TEM horn antenna fed by the UWB signal.
This paper numerically studies the coupling of the ultrawide band electromagnetic pulse into mines. Some typical coupling results are presented for different incident angles and distances from the antenna to the mine. In order to investigate the coupling problem, this paper studies the perfectly marched layer used to truncate the lossy boundary, and provides the distributions of the electric field radiated from the TEM horn antenna fed by the UWB signal.
2003,
15.
Abstract:
In this paper, the beam dynamics in micropulse electron gun (MPG) is studied using SEEG (Secondary Electron Emission Gun) program. First, without the consideration of the space charge effect, the process of longitudinal direction beam bunching in MPG is given. Second, the formation of the saturation current affected by the space charge effect and bunching effect is studied in details. Then, the design and optimization of the micropulse gun cavity and the simulation results of the cavity by SEEG are given. At last, the scheme of a experimental micropulse gun designed by Tsinghua University is introduced.
In this paper, the beam dynamics in micropulse electron gun (MPG) is studied using SEEG (Secondary Electron Emission Gun) program. First, without the consideration of the space charge effect, the process of longitudinal direction beam bunching in MPG is given. Second, the formation of the saturation current affected by the space charge effect and bunching effect is studied in details. Then, the design and optimization of the micropulse gun cavity and the simulation results of the cavity by SEEG are given. At last, the scheme of a experimental micropulse gun designed by Tsinghua University is introduced.
2003,
15.
Abstract:
The reflection properties of the TM01，TM02 modes of the circular waveguide by overmoded SWS are investigated by solving the Sparameters matrix with the method of the finite element method, and the difference between the reflection characteristics of two ports due to the asymmetry because of the introduction of the resonant cavity into one end of the SWS are analyzed. The numerical calculation results show that the reflection to the TM01 mode inputted into the port without resonant cavity increases while the reflection to the TM01 mode inputted into the port with resonant cavity decreases. The reasons that the introduction of the resonant cavity can reduce the needed period number of the SWSs and enhance the output microwave power efficiency are also demonstrated.
The reflection properties of the TM01，TM02 modes of the circular waveguide by overmoded SWS are investigated by solving the Sparameters matrix with the method of the finite element method, and the difference between the reflection characteristics of two ports due to the asymmetry because of the introduction of the resonant cavity into one end of the SWS are analyzed. The numerical calculation results show that the reflection to the TM01 mode inputted into the port without resonant cavity increases while the reflection to the TM01 mode inputted into the port with resonant cavity decreases. The reasons that the introduction of the resonant cavity can reduce the needed period number of the SWSs and enhance the output microwave power efficiency are also demonstrated.
2003,
15.
Abstract:
The primary experimental study on radial transit time oscillator (RTTO) was carried out. Under nonoptimized conditions, a microwave with the output peak power of above 30MW was generated at frequency 3.66GHz. The dependence of microwave power on the diode voltage and current are presented in this paper. The results obtained from this work agree with those from theoretical analysis and particle simulation.
The primary experimental study on radial transit time oscillator (RTTO) was carried out. Under nonoptimized conditions, a microwave with the output peak power of above 30MW was generated at frequency 3.66GHz. The dependence of microwave power on the diode voltage and current are presented in this paper. The results obtained from this work agree with those from theoretical analysis and particle simulation.
2003,
15.
Abstract:
By employing the limited Hankel integral transform, heat conduction and thermal deformation of optical windows induced by annularlydistributed laser beam are theoretically studied. The temperature increment and thermal deformation fields are expressed as infinite series. Then the theoretical results for sapphire and fused silica optical windows are calculated and compared with those from experiments. It is found that in 4s of irradiation, remarkable temperature rise occurs mainly in the irradiated annular area while its distribution over the whole window is far from a uniform one, so does the thermal deformation. Among all the parameters of materials', the absorption coefficient to incident laser and thermal expansion coefficient, and thermal diffusion coefficient are of the most importa
By employing the limited Hankel integral transform, heat conduction and thermal deformation of optical windows induced by annularlydistributed laser beam are theoretically studied. The temperature increment and thermal deformation fields are expressed as infinite series. Then the theoretical results for sapphire and fused silica optical windows are calculated and compared with those from experiments. It is found that in 4s of irradiation, remarkable temperature rise occurs mainly in the irradiated annular area while its distribution over the whole window is far from a uniform one, so does the thermal deformation. Among all the parameters of materials', the absorption coefficient to incident laser and thermal expansion coefficient, and thermal diffusion coefficient are of the most importa
2003,
15.
Abstract:
In this paper, tool's diamond coating are fabricated on tungsten carbide by pulsed UV laser surface pretreatment. The adhesion of diamond coatings under different laser pretreatment conditions are evaluated using indentation test. The optimum laser pretreatment conditions is obtained. Diamond coating tools are actually tested by machining of SiC-Al composite materials. The adhesion of diamond coating to tungsten carbide was greatly improved by the pulsed-UV-laser substrate pretreatment.
In this paper, tool's diamond coating are fabricated on tungsten carbide by pulsed UV laser surface pretreatment. The adhesion of diamond coatings under different laser pretreatment conditions are evaluated using indentation test. The optimum laser pretreatment conditions is obtained. Diamond coating tools are actually tested by machining of SiC-Al composite materials. The adhesion of diamond coating to tungsten carbide was greatly improved by the pulsed-UV-laser substrate pretreatment.
2003,
15.
Abstract:
The effects of energy and flux of electrons on Kapton/Al thermal control coatings were investigated. The spectral reflectance before and after irradiations of electrons was insitu measured. Experimental results show that the spectral reflectivity of Kapton/Al coatings was apparently degraded in the 300~1 200nm wavelength range of solar electromagnetic rays after electron irradiation. Under the exposure to electrons, no charging effects were found on the surface of Kapton films as an ioninduced conducting polymer. After electron irradiation, an “annealing” or “bleaching” effect occurred on the Kapton/Al coatings. For a given irradiation flux, the increment in solar absorptance of Kapton/Al coatings increased with electron energy. The relation of the increment in solar absorptance of
The effects of energy and flux of electrons on Kapton/Al thermal control coatings were investigated. The spectral reflectance before and after irradiations of electrons was insitu measured. Experimental results show that the spectral reflectivity of Kapton/Al coatings was apparently degraded in the 300~1 200nm wavelength range of solar electromagnetic rays after electron irradiation. Under the exposure to electrons, no charging effects were found on the surface of Kapton films as an ioninduced conducting polymer. After electron irradiation, an “annealing” or “bleaching” effect occurred on the Kapton/Al coatings. For a given irradiation flux, the increment in solar absorptance of Kapton/Al coatings increased with electron energy. The relation of the increment in solar absorptance of
2003,
15.
Abstract:
A series of contrast experiments were done to obtain the influence of vertical vane on flow inflexion, the loss of stagnation pressure and cavity static pressure. The cause of influence of the vane on diffuser flowfield is expounded by analysis. The vane can increase the length of supersonic region, the stability of cavity pressure, and reduce the loss of stagnation pressure thus to increase the pressure recover coefficient. The vane thickness has great influence on cavity static pressure, so the thickness must be controlled to avoid coming into being the normal shock.
A series of contrast experiments were done to obtain the influence of vertical vane on flow inflexion, the loss of stagnation pressure and cavity static pressure. The cause of influence of the vane on diffuser flowfield is expounded by analysis. The vane can increase the length of supersonic region, the stability of cavity pressure, and reduce the loss of stagnation pressure thus to increase the pressure recover coefficient. The vane thickness has great influence on cavity static pressure, so the thickness must be controlled to avoid coming into being the normal shock.
2003,
15.
Abstract:
Starting from the Collins formula, focusing properties of unapertured sinhGaussian beam are studied by using the encircled-power method. It is found that the axial intensity of focused sinh-Gaussian beams vanishes, so that Li-Wolf's approach to the focal shift fails. The encircled-power method is introduced to define the beam width and real focal plane of focused sinh-Gaussian beams, thus their focal shift can be determined. Numerical calculations are performed and show that the focal shift in focused sinh-Gaussian beams depends on the Fresnel number and decentered parameter, and increases with decreasing them. The optimal focusing of sinh-Gaussian beams is also analyzed.
Starting from the Collins formula, focusing properties of unapertured sinhGaussian beam are studied by using the encircled-power method. It is found that the axial intensity of focused sinh-Gaussian beams vanishes, so that Li-Wolf's approach to the focal shift fails. The encircled-power method is introduced to define the beam width and real focal plane of focused sinh-Gaussian beams, thus their focal shift can be determined. Numerical calculations are performed and show that the focal shift in focused sinh-Gaussian beams depends on the Fresnel number and decentered parameter, and increases with decreasing them. The optimal focusing of sinh-Gaussian beams is also analyzed.
2003,
15.
Abstract:
It has been demonstrated that methods of clamping for laser mirrors affect thermal deformation greatly. The characteristics of several clamping methods are analyzed and the corresponding thermal deformation and largest stress of silicon mirror are calculated. It is concluded that the clamping method with buckling ring has an advantage over the pressing method with clamp plate in PV value of deformation on mirror surface. Moreover, the stress fractures for mirrors with these methods of clamping are analyzed.
It has been demonstrated that methods of clamping for laser mirrors affect thermal deformation greatly. The characteristics of several clamping methods are analyzed and the corresponding thermal deformation and largest stress of silicon mirror are calculated. It is concluded that the clamping method with buckling ring has an advantage over the pressing method with clamp plate in PV value of deformation on mirror surface. Moreover, the stress fractures for mirrors with these methods of clamping are analyzed.
2003,
15.
Abstract:
Using the concept of equivalent resonators, dynamical characteristics of highpower solidstate multirod laser resonators are analyzed. The general expressions for equivalent gparameters and equivalent resonator length of multirod resonators are derived which permit us to obtain the dynamical characteristic curve and critical refractive powers on the equivalent gparameter diagram for multirod resonators and to illustrate their dynamical characteristics with numerical examples. In addition, the method of compensating a discrepance of the refractive power by a suitable adjustment of the distances between the mirror and the rod is discussed and the related analytical formula is given.
Using the concept of equivalent resonators, dynamical characteristics of highpower solidstate multirod laser resonators are analyzed. The general expressions for equivalent gparameters and equivalent resonator length of multirod resonators are derived which permit us to obtain the dynamical characteristic curve and critical refractive powers on the equivalent gparameter diagram for multirod resonators and to illustrate their dynamical characteristics with numerical examples. In addition, the method of compensating a discrepance of the refractive power by a suitable adjustment of the distances between the mirror and the rod is discussed and the related analytical formula is given.
