Email alert
RSS2004 Vol. 16, No. 04
Recommend Articles
column
Display Method:
2004,
16.
Abstract:
PFL charged by magnetic flux compression generator (MFCG ) through a pulse transformer is analyzed by using the electrocircuit simulating code and taking MFCG as a current source. Compared with experiments, the simulation method is a reasonable approach. Results of simulation and experiment show: it is very efficient to improve the amplitude of the first peak of charging voltage by increasing the mutual inductance, especially the secondary inductance of pulase transformer, and the load current slope of MFCG, the resistivity of dielectric water of PFL also affects the amplitude of charging voltage.
PFL charged by magnetic flux compression generator (MFCG ) through a pulse transformer is analyzed by using the electrocircuit simulating code and taking MFCG as a current source. Compared with experiments, the simulation method is a reasonable approach. Results of simulation and experiment show: it is very efficient to improve the amplitude of the first peak of charging voltage by increasing the mutual inductance, especially the secondary inductance of pulase transformer, and the load current slope of MFCG, the resistivity of dielectric water of PFL also affects the amplitude of charging voltage.
2004,
16.
Abstract:
A type of improved C-band MILO is brought forward and its optimized model is designed through theoretic analysis and numerical simulations. According to theoretical analysis of the slow-wave structure (SWS) using the magnetically insulation principle, the cathode radius and primary SWS parameters of C-band MILO are chosen. Through numerical simulations by a 2.5-D PIC code, the impacts of several structure parameters of MILO on its output power are investigated. With 21GW(at 500kV) input-power, a 3.91GHz, 2.77GW average output power microwave is generated from the optimized MILO by simulation. The saturation time is 10ns. The average efficiency is over 13%．
A type of improved C-band MILO is brought forward and its optimized model is designed through theoretic analysis and numerical simulations. According to theoretical analysis of the slow-wave structure (SWS) using the magnetically insulation principle, the cathode radius and primary SWS parameters of C-band MILO are chosen. Through numerical simulations by a 2.5-D PIC code, the impacts of several structure parameters of MILO on its output power are investigated. With 21GW(at 500kV) input-power, a 3.91GHz, 2.77GW average output power microwave is generated from the optimized MILO by simulation. The saturation time is 10ns. The average efficiency is over 13%．
2004,
16.
Abstract:
The highfrequency characteristics of highpower millimeterwave diffraction radiation generator are analyzed in detail using both linear theory and PIC method. This paper presents a method of mode selection. Results show that highpower millimeter wave with good frequency spectrum purity can be obtained by reasonably adjusting the operating parameters such as the electron beam's current, voltage and the highfrequency structure's depth, radius, period. Through analyses it can be found that the device with h=0.05cm can generate singlefrequency and highpower radiation of 8mm wave band. Studies indicate that diffraction radiation generator with simpler structure can also generate singlefrequency and highpower radiation of millimeterwave band.
The highfrequency characteristics of highpower millimeterwave diffraction radiation generator are analyzed in detail using both linear theory and PIC method. This paper presents a method of mode selection. Results show that highpower millimeter wave with good frequency spectrum purity can be obtained by reasonably adjusting the operating parameters such as the electron beam's current, voltage and the highfrequency structure's depth, radius, period. Through analyses it can be found that the device with h=0.05cm can generate singlefrequency and highpower radiation of 8mm wave band. Studies indicate that diffraction radiation generator with simpler structure can also generate singlefrequency and highpower radiation of millimeterwave band.
2004,
16.
Abstract:
The Chopping-Peaking type high power bipolar pulse former, and studies its operating principle.The bipolar pulses with different forms are goined through adjusting the stwiches time. In ideal condition, the outputting bipolar high voltage pulses with the peak-peak voltage between the peaks of unlike polarity is equal to that of the double voltage of the injecting pulse. By tuning the gaps of chopping switch and peaking switch properly, the highest peak-peak voltage of 360kV is obtained with the injecting voltage of 205kV. The duration of the bipolar pulse can be changed,it's maximum is equal to the width of the injecting pulse.The steeper the injecting pulse,the higher the peak-peak voltage of the generated bipolar voltage pulse．
The Chopping-Peaking type high power bipolar pulse former, and studies its operating principle.The bipolar pulses with different forms are goined through adjusting the stwiches time. In ideal condition, the outputting bipolar high voltage pulses with the peak-peak voltage between the peaks of unlike polarity is equal to that of the double voltage of the injecting pulse. By tuning the gaps of chopping switch and peaking switch properly, the highest peak-peak voltage of 360kV is obtained with the injecting voltage of 205kV. The duration of the bipolar pulse can be changed,it's maximum is equal to the width of the injecting pulse.The steeper the injecting pulse,the higher the peak-peak voltage of the generated bipolar voltage pulse．
2004,
16.
Abstract:
Varying the span of each cavity from uniform to nonuniform, a new device called nonuniform threecavity transittime oscillator (NTCTTO) has been developed. By employing a SUPERFISH code, the high frequency features of a nonuniform threecavity resonator were investigated numerically. The influences of span change on TM0102π/3like mode and the corresponding frequency, on the zaxial component of the electric field and its radial distribution were studied. Results show whether the TM0102π/3like mode exists depends on the span of each cavity. When the TM0102π/3like mode exists, the influence of the span change on the corresponding frequency is small(the difference between the highest and the lowest frequency is less than 4%); when the first cavity gets longer, the zaxial com
Varying the span of each cavity from uniform to nonuniform, a new device called nonuniform threecavity transittime oscillator (NTCTTO) has been developed. By employing a SUPERFISH code, the high frequency features of a nonuniform threecavity resonator were investigated numerically. The influences of span change on TM0102π/3like mode and the corresponding frequency, on the zaxial component of the electric field and its radial distribution were studied. Results show whether the TM0102π/3like mode exists depends on the span of each cavity. When the TM0102π/3like mode exists, the influence of the span change on the corresponding frequency is small(the difference between the highest and the lowest frequency is less than 4%); when the first cavity gets longer, the zaxial com
2004,
16.
Abstract:
Application of optimization principle was employed to evaluate the parameter of nanosecond pulse signal measurement system by input waveform and output waveform. Input waveform was reconstructed from the output waveform. The calculated results agree with analysis and experiment results well. To test suitability of the methods, compared with waveform from integrator, the reconstructed waveform has better performance and accuracy.
Application of optimization principle was employed to evaluate the parameter of nanosecond pulse signal measurement system by input waveform and output waveform. Input waveform was reconstructed from the output waveform. The calculated results agree with analysis and experiment results well. To test suitability of the methods, compared with waveform from integrator, the reconstructed waveform has better performance and accuracy.
Measurement and research of the quality factor of quasioptical resonator by scalar network analyzer
2004,
16.
Abstract:
The quality factors of FabryPerot resonator was measured by scalar net work analyzer. A new method was approved to determine the number of the mode. The testing results given by AV3617 were presented and external quality factor, unloaded quality factor were calculated. The measurement error was also analyzed and the main aspect of measurement error was the frequency data of half power point. Depending on the high frequency resolution of HP83630A and using reference marker the precision was improved.
The quality factors of FabryPerot resonator was measured by scalar net work analyzer. A new method was approved to determine the number of the mode. The testing results given by AV3617 were presented and external quality factor, unloaded quality factor were calculated. The measurement error was also analyzed and the main aspect of measurement error was the frequency data of half power point. Depending on the high frequency resolution of HP83630A and using reference marker the precision was improved.
2004,
16.
Abstract:
The measurement of the effective aperture of a waveguide antenna marked N5 is discussed in this paper. The principle and the method of measurement are presented. And the results of the effective aperture for the antenna with the corresponding frequencies are given. Compared to the results measured by Russian, the measured data is reliable. It facilitates the precisely measurement of the output power of the HPM source. The measurement method used in this paper can also be applied to measure the gain and the effective aperture of other antennas.
The measurement of the effective aperture of a waveguide antenna marked N5 is discussed in this paper. The principle and the method of measurement are presented. And the results of the effective aperture for the antenna with the corresponding frequencies are given. Compared to the results measured by Russian, the measured data is reliable. It facilitates the precisely measurement of the output power of the HPM source. The measurement method used in this paper can also be applied to measure the gain and the effective aperture of other antennas.
2004,
16.
Abstract:
The input system, is a very important part for the gyroklystron amplifier. The driven signal is injected into the input cavity through the input coupler, which excites the RF field to modulate the electron beam. A input coupler for the Ka-Band second harmonic gyroklystron is proposed and studied by using three-dimensional electromagnetic code in this paper. High mode purity of a circular TE021 mode in an input cavity is obtained．
The input system, is a very important part for the gyroklystron amplifier. The driven signal is injected into the input cavity through the input coupler, which excites the RF field to modulate the electron beam. A input coupler for the Ka-Band second harmonic gyroklystron is proposed and studied by using three-dimensional electromagnetic code in this paper. High mode purity of a circular TE021 mode in an input cavity is obtained．
2004,
16.
Abstract:
A novel, Highly accurate numerical synthetic technique for determining the high frequency characteristics of six-avity with open boundary is presented. The numerical method based on the coupling of the finite difference method in time domain with the discrete fast Fourier transform is applied to calculate the first four eigenfrequencies and eigenfunctions of the six-ity with open boundary. The absorbing boundary condition for TEM wave is tested numerically,and it is applied to writing the code. The cold testing of the cavity is done and the results are good agreement with the numerical calculus results. The first four eigenfrequencies and eigenfunctions of the close cavity is calculated as well. The results of the calculation is the foundation of the theoretical analysis of the transit tim
A novel, Highly accurate numerical synthetic technique for determining the high frequency characteristics of six-avity with open boundary is presented. The numerical method based on the coupling of the finite difference method in time domain with the discrete fast Fourier transform is applied to calculate the first four eigenfrequencies and eigenfunctions of the six-ity with open boundary. The absorbing boundary condition for TEM wave is tested numerically,and it is applied to writing the code. The cold testing of the cavity is done and the results are good agreement with the numerical calculus results. The first four eigenfrequencies and eigenfunctions of the close cavity is calculated as well. The results of the calculation is the foundation of the theoretical analysis of the transit tim
2004,
16.
Abstract:
The consistent theory of microwave power coupling and the optimism coupling factor are analyzed in detail by equivalent circuit method in this paper. The relationship among the microwave power, coupling factor, beam loading and parameters of the accelerating cavity is presented with analytical formula. The microwave coupling progress during the macropulse of thermionic cathode RFgun is discussed and the explanation of experimental phenomena such as the deformation of microwave coupling mode is given.
The consistent theory of microwave power coupling and the optimism coupling factor are analyzed in detail by equivalent circuit method in this paper. The relationship among the microwave power, coupling factor, beam loading and parameters of the accelerating cavity is presented with analytical formula. The microwave coupling progress during the macropulse of thermionic cathode RFgun is discussed and the explanation of experimental phenomena such as the deformation of microwave coupling mode is given.
2004,
16.
Abstract:
The physical model of magnetic motional plasma (MMP) is defined. Adopting method of perturbation theory to derive dielectric rate tensor of system, MMP shows a completely different form of the dielectric tensor with the static magnetic plasma. The results, given by numerical computation for propagating longitudinal wave, reveal that resonant frequency of system nonlinearly enhance with the increasing of plasma density; At the same conditions resonant frequency of dextral wave is higher than that of sinistral wave, The resonant frequency of system enhances with longitudinal magnetic field descends for the propagating dextral electromagnetic wave, but for the sinistral one．
The physical model of magnetic motional plasma (MMP) is defined. Adopting method of perturbation theory to derive dielectric rate tensor of system, MMP shows a completely different form of the dielectric tensor with the static magnetic plasma. The results, given by numerical computation for propagating longitudinal wave, reveal that resonant frequency of system nonlinearly enhance with the increasing of plasma density; At the same conditions resonant frequency of dextral wave is higher than that of sinistral wave, The resonant frequency of system enhances with longitudinal magnetic field descends for the propagating dextral electromagnetic wave, but for the sinistral one．
2004,
16.
Abstract:
A general understanding of the microsecondconductiontime plasma opening switch in the conduction and opening phase is summarized. The snowplow model including the equations and its differential formation is described. A result with inner radius of 5 cm and outer radius of 7 cm is given. The POS conduction time is predicted to be 1 005ns. Also the simulation result points out that the phase of plasma thinning appears at radius of 5.75 cm.
A general understanding of the microsecondconductiontime plasma opening switch in the conduction and opening phase is summarized. The snowplow model including the equations and its differential formation is described. A result with inner radius of 5 cm and outer radius of 7 cm is given. The POS conduction time is predicted to be 1 005ns. Also the simulation result points out that the phase of plasma thinning appears at radius of 5.75 cm.
2004,
16.
Abstract:
A third order correlator is built based on the technique of cross correlation between the fundamental and second harmonic waves of femtosecond lasers. Using this correlator, the contrast ratio of femtosecond laser pulses from a typical CPA laser system is measured. The measurements show that the contrast ratio of the system is about 10６. There is a strony ASE beside the main pulse, lasting for a long time. The seed contrast ratio is about 10５. There is a little pulse at the 2ps before the main pulse and a small stage at the two sides of main pulse．
A third order correlator is built based on the technique of cross correlation between the fundamental and second harmonic waves of femtosecond lasers. Using this correlator, the contrast ratio of femtosecond laser pulses from a typical CPA laser system is measured. The measurements show that the contrast ratio of the system is about 10６. There is a strony ASE beside the main pulse, lasting for a long time. The seed contrast ratio is about 10５. There is a little pulse at the 2ps before the main pulse and a small stage at the two sides of main pulse．
2004,
16.
Abstract:
We measure dark current, photocurrent of GaAs detector before and after proton radiation with the energy of 7.5MeV and 20MeV.The result shows that when GaAs detectors are irradiated by proton with the energy of 7.5MeV, its resistance increases, and additional conduction decrease with the dose of proton increases. This phenomenon is especially evidence when GaAs detectors are irradiated both by the energy of 20MeV and 7.5MeV proton. We analyze this phenomena and dope out some properties of this kind of detector．
We measure dark current, photocurrent of GaAs detector before and after proton radiation with the energy of 7.5MeV and 20MeV.The result shows that when GaAs detectors are irradiated by proton with the energy of 7.5MeV, its resistance increases, and additional conduction decrease with the dose of proton increases. This phenomenon is especially evidence when GaAs detectors are irradiated both by the energy of 20MeV and 7.5MeV proton. We analyze this phenomena and dope out some properties of this kind of detector．
2004,
16.
Abstract:
This paper describes the fabrication of cobalt nanothin films by pulsed laser ablation of cobalt target in a hydrogen background gas. KrF laser and xy laser scanning apparatus is used, and cobalt target is rotated at a rate of 20Hz. The deposition environment and its effect on thin film surface morphology are analyzed, and mechanism of forming particles is discussed. The results show that under lower background gas pressure it inclines to form droplet because the collision among plasmas themselves is prominent. While isles and then form particles agglomerate under higher background gas pressure. Monodispersed cobalt nanoparticles grow at a repetition rare of 4Hz and 5Pa background gas.
This paper describes the fabrication of cobalt nanothin films by pulsed laser ablation of cobalt target in a hydrogen background gas. KrF laser and xy laser scanning apparatus is used, and cobalt target is rotated at a rate of 20Hz. The deposition environment and its effect on thin film surface morphology are analyzed, and mechanism of forming particles is discussed. The results show that under lower background gas pressure it inclines to form droplet because the collision among plasmas themselves is prominent. While isles and then form particles agglomerate under higher background gas pressure. Monodispersed cobalt nanoparticles grow at a repetition rare of 4Hz and 5Pa background gas.
2004,
16.
Abstract:
The paper concerns the improvement of two primary technologies for 3ω(351nm) shot experiment in SG-Ⅱfacility target area , which are 3ω target alignment laser and optical viewing system .The 1ω (1 053nm) laser is exported form the Nd:YLF laser and passes the KTP+BBO system to acquire the 3ωlaser. And the 3ω laser is couplingout with main laser. In order to improve the laser accurately position on the target, the reflection optical system is replaced by the transmission optical system, which avoids the effect of chromatic aberration.
The paper concerns the improvement of two primary technologies for 3ω(351nm) shot experiment in SG-Ⅱfacility target area , which are 3ω target alignment laser and optical viewing system .The 1ω (1 053nm) laser is exported form the Nd:YLF laser and passes the KTP+BBO system to acquire the 3ωlaser. And the 3ω laser is couplingout with main laser. In order to improve the laser accurately position on the target, the reflection optical system is replaced by the transmission optical system, which avoids the effect of chromatic aberration.
2004,
16.
Abstract:
A method based on Sagnac interferometer for UV ultrashort pulse amplification is introduced．It provides automatic and phaselocked recombination of multiplexed beams in principle．The effect of optical components' adjustment tolerance on the interferometer is analyzed．And a practical multiplexing scheme use polarization sensitive reflector and it's experimental result is presented．A pulse of 2~3mJ,50mm in diameter is sent to the amplifier and abtained a stable output of 100mg, with a maximum of 120mg.
A method based on Sagnac interferometer for UV ultrashort pulse amplification is introduced．It provides automatic and phaselocked recombination of multiplexed beams in principle．The effect of optical components' adjustment tolerance on the interferometer is analyzed．And a practical multiplexing scheme use polarization sensitive reflector and it's experimental result is presented．A pulse of 2~3mJ,50mm in diameter is sent to the amplifier and abtained a stable output of 100mg, with a maximum of 120mg.
2004,
16.
Abstract:
In order to evaluate the influence resulted from the difference between the situation in which fusion neutrons are measured by Cu activation method and the situation in which the calibration factor is obtained by accelerator neutron Cu activation method, the author, by further developing the MCNP code, calculated the angular correlated γγ coincidence detection efficiency. The correction of calculation is demonstrated by comparing the calculation with the experimental result and the difference of less than 3% between the two situations is concluded.
In order to evaluate the influence resulted from the difference between the situation in which fusion neutrons are measured by Cu activation method and the situation in which the calibration factor is obtained by accelerator neutron Cu activation method, the author, by further developing the MCNP code, calculated the angular correlated γγ coincidence detection efficiency. The correction of calculation is demonstrated by comparing the calculation with the experimental result and the difference of less than 3% between the two situations is concluded.
2004,
16.
Abstract:
An online inspection apparatus of optics damage in large scale laser facility is developed applying darkfield imaging technology. Experiments were carried out on a multipass amplifier. Optical defects, such as film damage, selffocusing filament and cranny on optical elements are inspected. Experimental results show that this apparatus can be used for online inspection of optics damage. Further improvements. that the image aberration should be decreased and the inspection range be extended are proposed.
An online inspection apparatus of optics damage in large scale laser facility is developed applying darkfield imaging technology. Experiments were carried out on a multipass amplifier. Optical defects, such as film damage, selffocusing filament and cranny on optical elements are inspected. Experimental results show that this apparatus can be used for online inspection of optics damage. Further improvements. that the image aberration should be decreased and the inspection range be extended are proposed.
2004,
16.
Abstract:
Potassium dihydrogen phosphate (KDP) crystals were baked at varied temperatures in the same procedure. Three kinds of interference techniques were used to investigate stressinduced birefringence in KDP crystals. It was found that the annealing temperature greatly affects the improvement of the homogeneity of KDP crystal. Obvious improvement of homogeneity of KDP crystal was found after annealing at 50℃. With the rise of the annealing temperature, the extinction ratio increased. Growth ghost disappeared after annealing at 110℃. The extinction ratio decreased when the crystals were annealed at very high temperature, such as 170℃.
Potassium dihydrogen phosphate (KDP) crystals were baked at varied temperatures in the same procedure. Three kinds of interference techniques were used to investigate stressinduced birefringence in KDP crystals. It was found that the annealing temperature greatly affects the improvement of the homogeneity of KDP crystal. Obvious improvement of homogeneity of KDP crystal was found after annealing at 50℃. With the rise of the annealing temperature, the extinction ratio increased. Growth ghost disappeared after annealing at 110℃. The extinction ratio decreased when the crystals were annealed at very high temperature, such as 170℃.
2004,
16.
Abstract:
In gaspuff Zpinch experiments, the snowplow model, one of the simplest and commonly used models, has been used to predict the implosion time from the generator current parameters, the load mass per unit length, and initial radius of annular gas load. After analyzing the physical model, the onedimensional motion equation and it's solutions in different configuration of the annular gas column are discussed in this paper. According to these formulas, the calculated Zpinch imploding time arriving at the certer are compared with the values of the three typical experiments(on Gamble Ⅱ, DoubleEAGLE and BLACKJACK5 respectively) with current 1.21~3.0MA. The comparison shows that the snowplow model is a tool in prediction of some experimental results to optimize the load parameters like t
In gaspuff Zpinch experiments, the snowplow model, one of the simplest and commonly used models, has been used to predict the implosion time from the generator current parameters, the load mass per unit length, and initial radius of annular gas load. After analyzing the physical model, the onedimensional motion equation and it's solutions in different configuration of the annular gas column are discussed in this paper. According to these formulas, the calculated Zpinch imploding time arriving at the certer are compared with the values of the three typical experiments(on Gamble Ⅱ, DoubleEAGLE and BLACKJACK5 respectively) with current 1.21~3.0MA. The comparison shows that the snowplow model is a tool in prediction of some experimental results to optimize the load parameters like t
2004,
16.
Abstract:
The propagation of twisted anisotropic Gaussian schell model (AGSM) beams in free space is studied by using the matrix method. The explicit propagation equations of beam parameters and detailed numerical calculation results are given to illustrate the propagation properties of AGSM beams and the influence of the twist term and spatial correlation．
The propagation of twisted anisotropic Gaussian schell model (AGSM) beams in free space is studied by using the matrix method. The explicit propagation equations of beam parameters and detailed numerical calculation results are given to illustrate the propagation properties of AGSM beams and the influence of the twist term and spatial correlation．
2004,
16.
Abstract:
The model of plasma chemistry was developed to predict the appropriate electron mean energy and flow rate and discharge pressure for the generation of singlet oxygen molecule, based on physical chemistry with a simple reaction model. The model included the collisions of atom with molecule and electron with other species. It was found that electron mean energy must be less than 2.5eV. An optimum electron mean energy can be found at constant discharge pressure and flow rate. Electron density and discharge pressure played the second role among the parameters.
The model of plasma chemistry was developed to predict the appropriate electron mean energy and flow rate and discharge pressure for the generation of singlet oxygen molecule, based on physical chemistry with a simple reaction model. The model included the collisions of atom with molecule and electron with other species. It was found that electron mean energy must be less than 2.5eV. An optimum electron mean energy can be found at constant discharge pressure and flow rate. Electron density and discharge pressure played the second role among the parameters.
2004,
16.
Abstract:
This paper presents the principle of real time measurement of the object angular vibration by laser speckles and analysis of interference pattern. From the discussion and simulation, some conclusions can be drawn．Ｆirst, relative system the parameter is smaller, the undulation of laser power that was detected is bigger. Its means the signal is better. Second, the undulation of laser power diverges oscillation with the optical receiver aperture increase. The receiving aperture of detector should be adjustable for optimization. Lastly the measurement range of system is restricted by the modulation parameter．
This paper presents the principle of real time measurement of the object angular vibration by laser speckles and analysis of interference pattern. From the discussion and simulation, some conclusions can be drawn．Ｆirst, relative system the parameter is smaller, the undulation of laser power that was detected is bigger. Its means the signal is better. Second, the undulation of laser power diverges oscillation with the optical receiver aperture increase. The receiving aperture of detector should be adjustable for optimization. Lastly the measurement range of system is restricted by the modulation parameter．
2004,
16.
Abstract:
Binary optics can be used for increasing optical performances，decreasing size and weight，and decreasing systems costs in numerous applications．Many types of optics can be fabricated using diffractive surfaces that standard refractive lenses are not possible．By means of hybrid diffractive-refractive，using two kind glasses，a method and processes of apochromats have been introduced to realize for decreasing secondary spectrum in long focus Telescope for secondary planet in detail．The research results showed：secondary spectrum do not affect the quality of sight field the in corrected Telescope．The correction method is simple and satisfiable.
Binary optics can be used for increasing optical performances，decreasing size and weight，and decreasing systems costs in numerous applications．Many types of optics can be fabricated using diffractive surfaces that standard refractive lenses are not possible．By means of hybrid diffractive-refractive，using two kind glasses，a method and processes of apochromats have been introduced to realize for decreasing secondary spectrum in long focus Telescope for secondary planet in detail．The research results showed：secondary spectrum do not affect the quality of sight field the in corrected Telescope．The correction method is simple and satisfiable.
2004,
16.
Abstract:
A new type coulpled wave equations, whose acoustic branch is rewritten in terms of displacement, is established to describe SBS process. One dimensional backward SBS is researched by solving this coupled wave equations numerically and displacement and velocity profile in the entrance surface of pump laser are obtained, and the characteristics of SBS induced stress is presented. Calculation shows that the SBS induced surface displacement and velocity can reach the magnitude of 0.1nm and 10m/s respectively when pump intensity is 2.0×1015W/m2, and the corresponding stress exceeds 10MPa.The calculation results by new type equations agree well with those by traditional methods．
A new type coulpled wave equations, whose acoustic branch is rewritten in terms of displacement, is established to describe SBS process. One dimensional backward SBS is researched by solving this coupled wave equations numerically and displacement and velocity profile in the entrance surface of pump laser are obtained, and the characteristics of SBS induced stress is presented. Calculation shows that the SBS induced surface displacement and velocity can reach the magnitude of 0.1nm and 10m/s respectively when pump intensity is 2.0×1015W/m2, and the corresponding stress exceeds 10MPa.The calculation results by new type equations agree well with those by traditional methods．
2004,
16.
Abstract:
This paper concerns the thermal lensing effect that occurs as laser going through an optical window, and its influence on beam quality. By the method of impetus theorem, 2D solution of the thermal conduction equation is derived, in the form of generalized Fourier series. Then, the finite element method is applied to simulate the thermal deformation as a plane stress problem. Combined with the thermal deformation and the shift of the refractive index with the temperature, the wavefront distortion is calculated without considering the opticstress effect. Furthermore, the beam quality on far field is discussed. Temperature rise, thermal deformation, wavefront distortion and beam quality of fused quartz(SiO2) window and white bijou(Al2O3) window irradiated by the annulus beam are simulated a
This paper concerns the thermal lensing effect that occurs as laser going through an optical window, and its influence on beam quality. By the method of impetus theorem, 2D solution of the thermal conduction equation is derived, in the form of generalized Fourier series. Then, the finite element method is applied to simulate the thermal deformation as a plane stress problem. Combined with the thermal deformation and the shift of the refractive index with the temperature, the wavefront distortion is calculated without considering the opticstress effect. Furthermore, the beam quality on far field is discussed. Temperature rise, thermal deformation, wavefront distortion and beam quality of fused quartz(SiO2) window and white bijou(Al2O3) window irradiated by the annulus beam are simulated a
2004,
16.
Abstract:
A model describing the closing of an ultrafast gas switch was established. In the model the switch closing is divided into two phases: gas breakdown and voltage collapse. The development of the discharge in the first phase for hydrogen and nitrogen was numerically simulated. The waveform of the voltage applied to a 1mm nitrogen gap was assumed as a linear rising followed by a flat top. The time delay of the gap breakdown as well as the breakdown voltage was determined for different gas pressure and risetime of charging voltage. The results show a good agreement with that from experiments using hydrogen gap.
A model describing the closing of an ultrafast gas switch was established. In the model the switch closing is divided into two phases: gas breakdown and voltage collapse. The development of the discharge in the first phase for hydrogen and nitrogen was numerically simulated. The waveform of the voltage applied to a 1mm nitrogen gap was assumed as a linear rising followed by a flat top. The time delay of the gap breakdown as well as the breakdown voltage was determined for different gas pressure and risetime of charging voltage. The results show a good agreement with that from experiments using hydrogen gap.
2004,
16.
Abstract:
In order to improve the accumulation of the injected beam, it is very necessary to restrain β oscillation because of injected system error. This thesis systematically introduces the research for injection beam instability, the design principle and circuit of the feedback system for restraining the injected β oscillation of HLS using the turn by turn system［１］. Meanwhile, it also provides the result of preliminary experiments. As the proof of the theory and pre-study, we use a relatively simple analog filter and phase shifter to counteract the kicker course, which causes the β oscillation. From experiment result, it can be seen that the obvious restraining effect using the feedback system. All of these are the foundations of development for feedback system of bunch-by-bunch and lower
In order to improve the accumulation of the injected beam, it is very necessary to restrain β oscillation because of injected system error. This thesis systematically introduces the research for injection beam instability, the design principle and circuit of the feedback system for restraining the injected β oscillation of HLS using the turn by turn system［１］. Meanwhile, it also provides the result of preliminary experiments. As the proof of the theory and pre-study, we use a relatively simple analog filter and phase shifter to counteract the kicker course, which causes the β oscillation. From experiment result, it can be seen that the obvious restraining effect using the feedback system. All of these are the foundations of development for feedback system of bunch-by-bunch and lower
2004,
16.
Abstract:
It is studied, with the analytic method and the MonteCarlo numerical simulation for the flash Xray radiography of the tungsten sphere, that the scattered exposure and its space distribution are influenced by the sphere radius, the configuration of cells in the sphere, and the distance between the back cone and the recording plane. The results show that the scattered component of exposure is not homogeneous in space and increase while the radius increases. Enlarge the distance from the back cone to the recording plane can mitigate this inhomogeneity. It can be confirmed that the back cone is the primary source of the scattered exposure, and that increasing the distance between the back cone and the recording plane can reduce the scattered exposure effectively.
It is studied, with the analytic method and the MonteCarlo numerical simulation for the flash Xray radiography of the tungsten sphere, that the scattered exposure and its space distribution are influenced by the sphere radius, the configuration of cells in the sphere, and the distance between the back cone and the recording plane. The results show that the scattered component of exposure is not homogeneous in space and increase while the radius increases. Enlarge the distance from the back cone to the recording plane can mitigate this inhomogeneity. It can be confirmed that the back cone is the primary source of the scattered exposure, and that increasing the distance between the back cone and the recording plane can reduce the scattered exposure effectively.
2004,
16.
Abstract:
To satisfy the requirements of HIRFL (Heavy Ion Research Facility in Lanzhou), series of experiments have been done to produce metallic ion beams. By now, numerous methods,including oven heating and MIVOC (metallic ion from volatile compounds), have been tested. Experiments results show that oven heating is much better than MIVOC. In most of our researches, emphasis was put upon the ion production of copper, zinc, nickel of different charge states. Among the obtained ion beams, 39eμA Cu12+, 30eμA Zn15+, 29eμA Ni10+ are the very representative ones. This paper presents the spectrums of the production of these three kinds of metallic ions as well as some phenomena and analysis on the oven heating experiment.
To satisfy the requirements of HIRFL (Heavy Ion Research Facility in Lanzhou), series of experiments have been done to produce metallic ion beams. By now, numerous methods,including oven heating and MIVOC (metallic ion from volatile compounds), have been tested. Experiments results show that oven heating is much better than MIVOC. In most of our researches, emphasis was put upon the ion production of copper, zinc, nickel of different charge states. Among the obtained ion beams, 39eμA Cu12+, 30eμA Zn15+, 29eμA Ni10+ are the very representative ones. This paper presents the spectrums of the production of these three kinds of metallic ions as well as some phenomena and analysis on the oven heating experiment.
2004,
16.
Abstract:
A 2.5D PIC simulation using KARAT code for inner charge propagation within biased charge collector for measuring HPIB was presented. The simulation results indicated that the charges were neutralized but the current non-neutralized in the biased charge collector. The influence of ions collected vs biased voltage of the collector was also simulated. －800V biased voltage can meet the measurement of 500keV HPIB, and this is consistent with the experimental results．
A 2.5D PIC simulation using KARAT code for inner charge propagation within biased charge collector for measuring HPIB was presented. The simulation results indicated that the charges were neutralized but the current non-neutralized in the biased charge collector. The influence of ions collected vs biased voltage of the collector was also simulated. －800V biased voltage can meet the measurement of 500keV HPIB, and this is consistent with the experimental results．
