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RSS2004 Vol. 16, No. 11
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2004,
16.
Abstract:
Image taken by a fiber optic taper coupled CCD camera system characterizes the great difference among its pixels responsivity. This difference will obviously degrades image quality and makes it difficulty to get a clear image. The flat field correction method especially for the system mentioned above is a very useful method to get a better clear image. The flat field correction method includes three steps:1.A black background image is firstly obtained from such a system under the certain temperature and integration time; 2.The image which will be treated as a reference image for flat field correction should be taken under uniformity irradiation as possible and the same temperature and integration time;3.Subtracting the black background image from the reference image will obtain an importan
Image taken by a fiber optic taper coupled CCD camera system characterizes the great difference among its pixels responsivity. This difference will obviously degrades image quality and makes it difficulty to get a clear image. The flat field correction method especially for the system mentioned above is a very useful method to get a better clear image. The flat field correction method includes three steps:1.A black background image is firstly obtained from such a system under the certain temperature and integration time; 2.The image which will be treated as a reference image for flat field correction should be taken under uniformity irradiation as possible and the same temperature and integration time;3.Subtracting the black background image from the reference image will obtain an importan
2004,
16.
Abstract:
The DC-SC photoinjector at Peking University is designed to provide an electron beam of average current 1mA with the energy of 2~3MeV and normalized rms transverse emittance of 3πmm-mrad at an 81.25MHz repetition rate. The test facility has been completely installed in our lab. In this paper some of the ongoing experimental activities are summarized. First results from the cold test of superconducting cavity have been presented. According the results, we have improved the main coupler to repress the multipacting. The beam test of 100μA on the DC gun has been done, photocathode preparation chamber can produce Cs2Te cathodes (5%@266nm), and the laser system can provide laser pulse with 266nm wavelength. The time synchronization between laser and RF power has been achieved by a timing stabi
The DC-SC photoinjector at Peking University is designed to provide an electron beam of average current 1mA with the energy of 2~3MeV and normalized rms transverse emittance of 3πmm-mrad at an 81.25MHz repetition rate. The test facility has been completely installed in our lab. In this paper some of the ongoing experimental activities are summarized. First results from the cold test of superconducting cavity have been presented. According the results, we have improved the main coupler to repress the multipacting. The beam test of 100μA on the DC gun has been done, photocathode preparation chamber can produce Cs2Te cathodes (5%@266nm), and the laser system can provide laser pulse with 266nm wavelength. The time synchronization between laser and RF power has been achieved by a timing stabi
2004,
16.
Abstract:
Present fundamental equations of thermoelastic deformation of thermal barrier coating(TBC) irradiated by laser in the condition of plane strain. Series solutions of steady temperature field are derived. Thermoelastic stress field in TBC is studied by means of variational principle of complementary energy. The distributed characters of maximal stresses and interfacial ones and the effects of some physical parameters on stresses are investigated. The results show that the main factor caused destroy of TBC is tensile stress; The interfacial stresses are comparatively feeble, but concentrate at the free edge; The peeling stresses are stronger than shearing ones and are important reason for failure of coating. Increase of coating’s thickness changes the distribution of stresses in the directio
Present fundamental equations of thermoelastic deformation of thermal barrier coating(TBC) irradiated by laser in the condition of plane strain. Series solutions of steady temperature field are derived. Thermoelastic stress field in TBC is studied by means of variational principle of complementary energy. The distributed characters of maximal stresses and interfacial ones and the effects of some physical parameters on stresses are investigated. The results show that the main factor caused destroy of TBC is tensile stress; The interfacial stresses are comparatively feeble, but concentrate at the free edge; The peeling stresses are stronger than shearing ones and are important reason for failure of coating. Increase of coating’s thickness changes the distribution of stresses in the directio
2004,
16.
Abstract:
An annular square intensity distribution with linear non-uniformity in the x direction is used to model the high-power laser, a detailed numerical simulation is performed to study the high-power laser propagation in a beam control system by means of a four-dimensional simulation code. It is shown that the thermal effect decreases the peak intensity and beam focusability in the far field. The non-uniformity of the initial beam results in a further decrease of the peak intensity and beam focusability, leads to a shift of the center of beam gravity and peak intensity, and astigmatism in the far field. The transversal wind and axial wind both suppress the thermal effect. The axial wind does not cause a shift of the center of beam gravity and astigmatism in the far field, but it takes a longer
An annular square intensity distribution with linear non-uniformity in the x direction is used to model the high-power laser, a detailed numerical simulation is performed to study the high-power laser propagation in a beam control system by means of a four-dimensional simulation code. It is shown that the thermal effect decreases the peak intensity and beam focusability in the far field. The non-uniformity of the initial beam results in a further decrease of the peak intensity and beam focusability, leads to a shift of the center of beam gravity and peak intensity, and astigmatism in the far field. The transversal wind and axial wind both suppress the thermal effect. The axial wind does not cause a shift of the center of beam gravity and astigmatism in the far field, but it takes a longer
2004,
16.
Abstract:
By combining the rate equation (RE) model with the chemical kinetics model, the effects of gain saturation models and chemical reaction systems on the performance of COIL are discussed in this paper. A premixed one-dimensional model is assumed for the flow field, and a chemical kinetics of 10 components and 21 reactions is adopted. The effects of undecomposed iodine molecular, yield of excited oxygen, content of water and temperature on the power of COIL are analyzed and calculated.The computational results show that much more energy is expanded in the processes of mixing and reaction if the flux of iodine is too much, and that much less flux of iodine results in lower gain, which is not benefit to extracting energy．
By combining the rate equation (RE) model with the chemical kinetics model, the effects of gain saturation models and chemical reaction systems on the performance of COIL are discussed in this paper. A premixed one-dimensional model is assumed for the flow field, and a chemical kinetics of 10 components and 21 reactions is adopted. The effects of undecomposed iodine molecular, yield of excited oxygen, content of water and temperature on the power of COIL are analyzed and calculated.The computational results show that much more energy is expanded in the processes of mixing and reaction if the flux of iodine is too much, and that much less flux of iodine results in lower gain, which is not benefit to extracting energy．
2004,
16.
Abstract:
Experiments that use single-pulse laser to ablate small steel ball in atmosphere were conducted. In these experiments, the propulsion efficiency parameters were obtained and different phenomena for the steel ball in front and back of the focus were analyzed in detail. To get a series of experiment data, experiments for different mbient conditions and different target materials were conducted and the propulsion parameters were obtained, and the experiment data were compared with those of overseas and numerical results.Experimental results showed that the material of target and the laser intensity were the main factors influenced the mechanical coupling coefficient(cm), and the cm value increased a few with the decreased of ambient pressure.
Experiments that use single-pulse laser to ablate small steel ball in atmosphere were conducted. In these experiments, the propulsion efficiency parameters were obtained and different phenomena for the steel ball in front and back of the focus were analyzed in detail. To get a series of experiment data, experiments for different mbient conditions and different target materials were conducted and the propulsion parameters were obtained, and the experiment data were compared with those of overseas and numerical results.Experimental results showed that the material of target and the laser intensity were the main factors influenced the mechanical coupling coefficient(cm), and the cm value increased a few with the decreased of ambient pressure.
2004,
16.
Abstract:
In this paper, the simulation and theoretical analysis of Nilike Ag Xraylaser (XRL) are included, which are driven by 1.06μm premainpulse with a power of 1.2×1013W/cm2. It is verified that, employing 23mm target, XRL can obtain effective amplification, which agrees with experiments. Power nonuniformity along focus line, induced by single cylindrical lens, is also considered. According to theoretical simulation, adopting curve target can effectively overcome the effect of reflection and the disadvantage of this nonuniformity. Lower limit of drive power needed by output of Nilike Ag XRL, predicted by theoretical simulation, also agrees with experiments. Theoretical simulation shows that, using 1% pre-pulse, if appropriate optimization of time interval between preand main puls
In this paper, the simulation and theoretical analysis of Nilike Ag Xraylaser (XRL) are included, which are driven by 1.06μm premainpulse with a power of 1.2×1013W/cm2. It is verified that, employing 23mm target, XRL can obtain effective amplification, which agrees with experiments. Power nonuniformity along focus line, induced by single cylindrical lens, is also considered. According to theoretical simulation, adopting curve target can effectively overcome the effect of reflection and the disadvantage of this nonuniformity. Lower limit of drive power needed by output of Nilike Ag XRL, predicted by theoretical simulation, also agrees with experiments. Theoretical simulation shows that, using 1% pre-pulse, if appropriate optimization of time interval between preand main puls
2004,
16.
Abstract:
The effects of vacuum annealing with different temperature gradient on 355nm Al2O3/MgF2 HR coatings were investigated. A number of samples had been prepared by electron beam evaporation using the same deposition process at optimal deposition temperature of 280℃. After deposition samples were annealed in the coating chamber for three hours with different temperature gradient. The structure of samples had been characterized by X-ray diffraction (XRD). Laser-induced damage threshold (LIDT) was measured by a 355 nm pulsed laser with a pulse width of 8 ns. Transmittance and reflectance of the samples were measured by Lambda 900 Spectrometer. It is found that different temperature gradient of annealing leads to different structures，LIDT and absorption of samples. Decreasing the temperature gra
The effects of vacuum annealing with different temperature gradient on 355nm Al2O3/MgF2 HR coatings were investigated. A number of samples had been prepared by electron beam evaporation using the same deposition process at optimal deposition temperature of 280℃. After deposition samples were annealed in the coating chamber for three hours with different temperature gradient. The structure of samples had been characterized by X-ray diffraction (XRD). Laser-induced damage threshold (LIDT) was measured by a 355 nm pulsed laser with a pulse width of 8 ns. Transmittance and reflectance of the samples were measured by Lambda 900 Spectrometer. It is found that different temperature gradient of annealing leads to different structures，LIDT and absorption of samples. Decreasing the temperature gra
2004,
16.
Abstract:
When adopting mode-locked Nd:YAG laser to choose single pulse, KD*P Pockels cell is usually used. The half wavelength voltage is 6.6 kV to the laser of 1.06μm wavelength. In recent years, cold cathode thyratron KN-22 is widely used in circuit, but here KN-22 is replaced by MOSFET. The circuit with MOSFET has stable and credible performance, it can output a pulse of －6.6~－8kV and the pulse width can be adjusted from 5ns to 10ns. The circuit has a short time jitter (0.5ns), a delay of 30ns and high probability of selecting single pulse (100%). No abnormity is found after using a long time and the circuit can be also used as chopper and pulse shearer．
When adopting mode-locked Nd:YAG laser to choose single pulse, KD*P Pockels cell is usually used. The half wavelength voltage is 6.6 kV to the laser of 1.06μm wavelength. In recent years, cold cathode thyratron KN-22 is widely used in circuit, but here KN-22 is replaced by MOSFET. The circuit with MOSFET has stable and credible performance, it can output a pulse of －6.6~－8kV and the pulse width can be adjusted from 5ns to 10ns. The circuit has a short time jitter (0.5ns), a delay of 30ns and high probability of selecting single pulse (100%). No abnormity is found after using a long time and the circuit can be also used as chopper and pulse shearer．
2004,
16.
Abstract:
Using cavity ring-down spectrometer technique, the precise measurement system for the high reflectivity of COIL mirrors has been built. At the straight ring-down cavity condition, some factors that may affect the accuracy of the measurement system was estimated systematically. And the correspondent experiments were carried out too. The experiments results show that the high reflectivity of the COIL mirrors could be precisely measured by the measurement system with precision of 10－5. And the measurement results were accuracy and reliable under mode matching of test light and ring-down cavity.
Using cavity ring-down spectrometer technique, the precise measurement system for the high reflectivity of COIL mirrors has been built. At the straight ring-down cavity condition, some factors that may affect the accuracy of the measurement system was estimated systematically. And the correspondent experiments were carried out too. The experiments results show that the high reflectivity of the COIL mirrors could be precisely measured by the measurement system with precision of 10－5. And the measurement results were accuracy and reliable under mode matching of test light and ring-down cavity.
2004,
16.
Abstract:
This paper reports the experimental research on the interaction of ultra-short and ultra-intense laser with Cu foil target. The spatial distributions and yield of the protons with different target thicknesses were recorded by nuclear track detector CR39. And the proton energy spectrum was measured by Thomson magnetic spectrometer. The results show that about 105~106 high energy protons jet only in the direction normal to the surface of target within a little cone angle. A sharp cutoff energy exists in the proton energy spectrum, and it depends on the target thickness.
This paper reports the experimental research on the interaction of ultra-short and ultra-intense laser with Cu foil target. The spatial distributions and yield of the protons with different target thicknesses were recorded by nuclear track detector CR39. And the proton energy spectrum was measured by Thomson magnetic spectrometer. The results show that about 105~106 high energy protons jet only in the direction normal to the surface of target within a little cone angle. A sharp cutoff energy exists in the proton energy spectrum, and it depends on the target thickness.
2004,
16.
Abstract:
The experimental investigation on X-ray laser is performed using two driving prepulses at the "Xingguang-Ⅱ" device. The experimental method and result are reported. The experiment didn't find remarkable enhancement of the output energy of X-ray laser using two prepulses than using one prepulse. One of the reasons maybe the driving laser energy is too low. Utilizing MED103 procedure to imitate calculation, it gives the same result as the experiment.
The experimental investigation on X-ray laser is performed using two driving prepulses at the "Xingguang-Ⅱ" device. The experimental method and result are reported. The experiment didn't find remarkable enhancement of the output energy of X-ray laser using two prepulses than using one prepulse. One of the reasons maybe the driving laser energy is too low. Utilizing MED103 procedure to imitate calculation, it gives the same result as the experiment.
2004,
16.
Abstract:
The paper analyzes several EMI modes during the charging and discharging periods of the power system of the 4×2 multisegment amplifiers. In order to deal these EMI modes, the methods of grounding one terminal of the capacitor, single grounding of the whole power system, preionization shielding, optic fiber isolation and other measures were adopted. The whole system runs more safely, stably and reliably after adopting these measures．
The paper analyzes several EMI modes during the charging and discharging periods of the power system of the 4×2 multisegment amplifiers. In order to deal these EMI modes, the methods of grounding one terminal of the capacitor, single grounding of the whole power system, preionization shielding, optic fiber isolation and other measures were adopted. The whole system runs more safely, stably and reliably after adopting these measures．
2004,
16.
Abstract:
The newly developed LD-pumped oscillator is ring structured. This oscillator has such advantages as almost 100% possibility for single-longitude-mode output, high stability for the waveform and amplitude of the output pulse. These advantage make it convenient to be united with the multipass amplifier system. Experimental research on the united LD-pumped oscillator and the multipass amplifier has got great achievement. The output energy has attained 1 252J, which is the highest energy for single beamline solid-state laser in our country. The pulse width for this shot is 1.26ns, and the size for this shot is 20cm×20cm. So the average power density is 2.5GW/cm2.
The newly developed LD-pumped oscillator is ring structured. This oscillator has such advantages as almost 100% possibility for single-longitude-mode output, high stability for the waveform and amplitude of the output pulse. These advantage make it convenient to be united with the multipass amplifier system. Experimental research on the united LD-pumped oscillator and the multipass amplifier has got great achievement. The output energy has attained 1 252J, which is the highest energy for single beamline solid-state laser in our country. The pulse width for this shot is 1.26ns, and the size for this shot is 20cm×20cm. So the average power density is 2.5GW/cm2.
2004,
16.
Abstract:
A compact L-band magnetically insulated transmission line oscillator(MILO),which has a new-type mode converter and a vewtype beam dump which increases a beam dump disk,a noe-cavity RF choke and a carefully designed impedance discontinuity between the choke-vane section and the SWS-vane section, is experimentally investigated. The compact MILO is driven by a self-built 600kV, 8Ω, 100ns pulser:SPARK０１.When the input voltage is 515～538kV, and the diode current is 58～61kA, high power microwaves of the TM01 mode are generated from the device with a frequency of 1.76～1.78GHz, an output power of 2.2～2.5GW, and the power conversion efficiency of 7.3%～7.9% in experiments. In this case, the duration of the effective voltage (above the threshold voltage, 500kV) is 30ns, and the duration o
A compact L-band magnetically insulated transmission line oscillator(MILO),which has a new-type mode converter and a vewtype beam dump which increases a beam dump disk,a noe-cavity RF choke and a carefully designed impedance discontinuity between the choke-vane section and the SWS-vane section, is experimentally investigated. The compact MILO is driven by a self-built 600kV, 8Ω, 100ns pulser:SPARK０１.When the input voltage is 515～538kV, and the diode current is 58～61kA, high power microwaves of the TM01 mode are generated from the device with a frequency of 1.76～1.78GHz, an output power of 2.2～2.5GW, and the power conversion efficiency of 7.3%～7.9% in experiments. In this case, the duration of the effective voltage (above the threshold voltage, 500kV) is 30ns, and the duration o
2004,
16.
Abstract:
Many high-power microwave (HPM) sources utilize an azimuthally symmetric output mode, like the TM01 circular waveguide or the coaxial TEM modes. If radiated directly these modes produce a doughnut-shaped pattern, with a bore-sight null. A novel mode-conversion technique for transforming the azimuthally symmetric mode to one with a more desirable radiated pattern is described and analyzed. The novel approach is as follows: first, the coaxial TEM mode is converted to TE11 fan-shaped waveguide mode by inserting fins into the coaxial waveguide, then the coaxial TE11 mode is got by varying the length of the fins, finally the coaxial TE11 mode is transformed to TE11 circular waveguide mode. A mode converter for 3.8GHz based on this principle is designed and optimized. The calculated results show
Many high-power microwave (HPM) sources utilize an azimuthally symmetric output mode, like the TM01 circular waveguide or the coaxial TEM modes. If radiated directly these modes produce a doughnut-shaped pattern, with a bore-sight null. A novel mode-conversion technique for transforming the azimuthally symmetric mode to one with a more desirable radiated pattern is described and analyzed. The novel approach is as follows: first, the coaxial TEM mode is converted to TE11 fan-shaped waveguide mode by inserting fins into the coaxial waveguide, then the coaxial TE11 mode is got by varying the length of the fins, finally the coaxial TE11 mode is transformed to TE11 circular waveguide mode. A mode converter for 3.8GHz based on this principle is designed and optimized. The calculated results show
2004,
16.
Abstract:
Considering azimuthal symmetrical harmonics and higher order harmonics in non-vane area, using field matching method and boundary condition of the ridge-loaded ring-plane slow wave structure, the dispersion equation of vane-loaded helical slow-wave structure is obtained, and coupling impedance and attenuation constant is deduced on the basis of the dispersion equation. The numerical simulation by MAFIA is compared with the theoretical calculation and experiment. They have consistent curve trend, which may explain the physics essence of the slow wave structure. The effect of the dispersion is discussed for different vane angles. The method provides a means for other types of vane-load helical slow-wave structures.
Considering azimuthal symmetrical harmonics and higher order harmonics in non-vane area, using field matching method and boundary condition of the ridge-loaded ring-plane slow wave structure, the dispersion equation of vane-loaded helical slow-wave structure is obtained, and coupling impedance and attenuation constant is deduced on the basis of the dispersion equation. The numerical simulation by MAFIA is compared with the theoretical calculation and experiment. They have consistent curve trend, which may explain the physics essence of the slow wave structure. The effect of the dispersion is discussed for different vane angles. The method provides a means for other types of vane-load helical slow-wave structures.
2004,
16.
Abstract:
According to the coupled-mode theory of variable crosssection waveguide and differential equations which the axial profile function of electric field satisfies, the program with auto optimized function was written. The influence of taper angle, cavity dissipation and mismatch of output cavity and external circuit on resonant frequency, quality factor and field profile was studied in detail. It further established the base of the interaction of highfrequency field with electron beam and of output cavity．
According to the coupled-mode theory of variable crosssection waveguide and differential equations which the axial profile function of electric field satisfies, the program with auto optimized function was written. The influence of taper angle, cavity dissipation and mismatch of output cavity and external circuit on resonant frequency, quality factor and field profile was studied in detail. It further established the base of the interaction of highfrequency field with electron beam and of output cavity．
2004,
16.
Abstract:
Because of the needs of variable pulse width, variable frequency and variable power of LD in the laser fuze communication systems, a model of the driver circuit is brought out for the system based on the circuits’s principle. Using retriggerable monostable multivibrators to provide the trigger signal and double MOS driver to drive the LD, with a lot of experiments, emulations and comparisons, the variable frequency, pulse width and power driver circuit is designed. And the pulse frequency and width can be changed easily for its situations. The dirver circuit has large range frefuency modulated from 10Hz to 2kHz and large range pulse width modulated from several nanoseconds to several hundreds nanoseconds. So the whole system capability and reliability can be improved greatly.
Because of the needs of variable pulse width, variable frequency and variable power of LD in the laser fuze communication systems, a model of the driver circuit is brought out for the system based on the circuits’s principle. Using retriggerable monostable multivibrators to provide the trigger signal and double MOS driver to drive the LD, with a lot of experiments, emulations and comparisons, the variable frequency, pulse width and power driver circuit is designed. And the pulse frequency and width can be changed easily for its situations. The dirver circuit has large range frefuency modulated from 10Hz to 2kHz and large range pulse width modulated from several nanoseconds to several hundreds nanoseconds. So the whole system capability and reliability can be improved greatly.
2004,
16.
Abstract:
The major subjects of RF window design for high average power gyroklystron amplifiers are to reduce the reflectivity and absorption power in order to enhance amplifier's stability and protect output window. In this paper, the window's reflection and absorption are analyzed in detail. As an example, a sapphire window of 9mm in diameter and 1.351mm in thickness for 10kW, 34GHz, TE01 gyroklystron amplifier is presented. Its reflectivity is less than 1% if process error is within 2%, and its absorbing power is about 2.5W while the output average power is 10kW. As the window's reflectivity is sensitive to its thickness error, the thickness must be strictly controlled in processing．
The major subjects of RF window design for high average power gyroklystron amplifiers are to reduce the reflectivity and absorption power in order to enhance amplifier's stability and protect output window. In this paper, the window's reflection and absorption are analyzed in detail. As an example, a sapphire window of 9mm in diameter and 1.351mm in thickness for 10kW, 34GHz, TE01 gyroklystron amplifier is presented. Its reflectivity is less than 1% if process error is within 2%, and its absorbing power is about 2.5W while the output average power is 10kW. As the window's reflectivity is sensitive to its thickness error, the thickness must be strictly controlled in processing．
2004,
16.
Abstract:
Using the self-consistent linear field theory, Cherenkov radiation excitated by the beam-wave interaction of a thin annular relativistic electron beam in a plasma-filled, dielectric coaxial cylindrical waveguide was analyzed. The dispersion equation of the interaction, the synchronized condition and the wave growth rate were derived. The energy exchange between the wave and the electron beam in the presence of background plasma was discussed, and the effects of plasma density on the dispersion characteristics, the wave growth rate and the beam-wave energy exchange were calculated and discussed. It was clear that the Cherenkov radiation is result of the coupling between the slow TM mode propagated along the waveguide and the negative-energy space-charge mode propagated along the beam, and t
Using the self-consistent linear field theory, Cherenkov radiation excitated by the beam-wave interaction of a thin annular relativistic electron beam in a plasma-filled, dielectric coaxial cylindrical waveguide was analyzed. The dispersion equation of the interaction, the synchronized condition and the wave growth rate were derived. The energy exchange between the wave and the electron beam in the presence of background plasma was discussed, and the effects of plasma density on the dispersion characteristics, the wave growth rate and the beam-wave energy exchange were calculated and discussed. It was clear that the Cherenkov radiation is result of the coupling between the slow TM mode propagated along the waveguide and the negative-energy space-charge mode propagated along the beam, and t
2004,
16.
Abstract:
Based on the static electricfield simulation, the structures of diode and insulator, as well as the position and shape of guiding magnetic-field are designed and optimized. Then the experiments of repetition rate and intense current electron-beam diode are carried out on high voltage generator, and the experimental waveforms are brought forth. The compares of the cathode emission character at different vacuum and different cathode materials are presented. The output electron-beam current of graphite and metal cathode are both stable with repetition rate at the candition of p＜0.01Pa. The designed diode can deliver intense electron-beam pulse of 500kV/5kA, pulse width 40ns, repetition rate 100Hz．
Based on the static electricfield simulation, the structures of diode and insulator, as well as the position and shape of guiding magnetic-field are designed and optimized. Then the experiments of repetition rate and intense current electron-beam diode are carried out on high voltage generator, and the experimental waveforms are brought forth. The compares of the cathode emission character at different vacuum and different cathode materials are presented. The output electron-beam current of graphite and metal cathode are both stable with repetition rate at the candition of p＜0.01Pa. The designed diode can deliver intense electron-beam pulse of 500kV/5kA, pulse width 40ns, repetition rate 100Hz．
2004,
16.
Abstract:
It is important to study the shielding effectiveness to reduce the electromagnetic interference and to protect electronic components. In this paper the shielding effectiveness of aperture arrays on different shapes is calculated and analyzed. The effects of the spaces between the adjacent apertures are analyzed. The results show that the penetration coefficient (PC) of a circle aperture array is the smallest, the one of a square aperture array is medium, and the one of a honey aperture array is the biggest, but their spectrums are almost the same. While for a dumbbell aperture array, because the contour shape is very different with the former aperture arrays, its magnetic current distribution is very different with the other’s. Thus the PC of a dumbbell aperture array is bigger than the o
It is important to study the shielding effectiveness to reduce the electromagnetic interference and to protect electronic components. In this paper the shielding effectiveness of aperture arrays on different shapes is calculated and analyzed. The effects of the spaces between the adjacent apertures are analyzed. The results show that the penetration coefficient (PC) of a circle aperture array is the smallest, the one of a square aperture array is medium, and the one of a honey aperture array is the biggest, but their spectrums are almost the same. While for a dumbbell aperture array, because the contour shape is very different with the former aperture arrays, its magnetic current distribution is very different with the other’s. Thus the PC of a dumbbell aperture array is bigger than the o
2004,
16.
Abstract:
The nonlinear beam-wave interaction in coupled-cavity TWT working in plasma-cavity hybrid mode, was studied using the theory of mode expansion, and the nonlinear beam-wave interaction self-consistent working equations have been obtained. The space-charge field with plasma-background was analyzed using the Green's function. A simulation program has been programmed to analyze the nonlinear characteristics in the plasma-cavity hybrid mode coupled-cavity TWT, such as the gain, efficiency, output power. The results show that the warm bandwidth can reach (20~30)% and the efficiency can be more than 50% in coupled-cavity TWT working in plasma-cavity hybrid mode.
The nonlinear beam-wave interaction in coupled-cavity TWT working in plasma-cavity hybrid mode, was studied using the theory of mode expansion, and the nonlinear beam-wave interaction self-consistent working equations have been obtained. The space-charge field with plasma-background was analyzed using the Green's function. A simulation program has been programmed to analyze the nonlinear characteristics in the plasma-cavity hybrid mode coupled-cavity TWT, such as the gain, efficiency, output power. The results show that the warm bandwidth can reach (20~30)% and the efficiency can be more than 50% in coupled-cavity TWT working in plasma-cavity hybrid mode.
2004,
16.
Abstract:
A novel high voltage pulse generator is developed for the simulation of HEMP according to the standard of IEC61000-2-9 and MIL-STD-461E. The generator can produce both single and repeated pulse. Its double-exponential output has a rise time less than 3ns, with the pulse width around 58ns and amplitude up to 4kV. It can also generate square wave with rise time less than 2ns and amplitude up to 4kV. The circuit design and experimental test of the pulse generator are introduced in this paper. The test result is also presented to show the difference of the interference effect produced by the new generator and the original HEMP defined in MIL-STD-461D.
A novel high voltage pulse generator is developed for the simulation of HEMP according to the standard of IEC61000-2-9 and MIL-STD-461E. The generator can produce both single and repeated pulse. Its double-exponential output has a rise time less than 3ns, with the pulse width around 58ns and amplitude up to 4kV. It can also generate square wave with rise time less than 2ns and amplitude up to 4kV. The circuit design and experimental test of the pulse generator are introduced in this paper. The test result is also presented to show the difference of the interference effect produced by the new generator and the original HEMP defined in MIL-STD-461D.
2004,
16.
Abstract:
Using the primary program 3DRun given by code VC++, multiplication effect of secondary emission microwave electron gun(SEMEG) is investigated. The relation between multiplication effect and length of cavity and electric field in the gun is studied with onedimension simulation. The Longitudinal bunching and energy focusing of out electrons is calculated in detail at 10mm length of cavity and 5.4MV/m electric field in the gun. The beam dynamics with space charge effect is also investigated with 3DRun. The emittance of out beam is calculated. With simulation and analysis, it is proved that SEMEG can provide high-current, low-emittance electron pulse．
Using the primary program 3DRun given by code VC++, multiplication effect of secondary emission microwave electron gun(SEMEG) is investigated. The relation between multiplication effect and length of cavity and electric field in the gun is studied with onedimension simulation. The Longitudinal bunching and energy focusing of out electrons is calculated in detail at 10mm length of cavity and 5.4MV/m electric field in the gun. The beam dynamics with space charge effect is also investigated with 3DRun. The emittance of out beam is calculated. With simulation and analysis, it is proved that SEMEG can provide high-current, low-emittance electron pulse．
2004,
16.
Abstract:
The key technologies of building a high repetition rate solid state switch were studied with two power MOSFET components, two MOSFET drivers, and fiber as high voltage isolator and optical data link. These technologies are trigger signal high voltage isolation technology, power MOSFET drive technology, power MOSFET parallel link and series link technology. Outputs of 1kV, 13A, 4MHz repetition rate on single MOSFET switch, 1.6kV, 2MHz repetition rate on two series MOSFET switch,and 130A, and 2MHz repetition rate output on two parallel MOSFET switch have been got．
The key technologies of building a high repetition rate solid state switch were studied with two power MOSFET components, two MOSFET drivers, and fiber as high voltage isolator and optical data link. These technologies are trigger signal high voltage isolation technology, power MOSFET drive technology, power MOSFET parallel link and series link technology. Outputs of 1kV, 13A, 4MHz repetition rate on single MOSFET switch, 1.6kV, 2MHz repetition rate on two series MOSFET switch,and 130A, and 2MHz repetition rate output on two parallel MOSFET switch have been got．
2004,
16.
Abstract:
The finite element method (FEM) is introduced to design a structure of cathode groupware for an electron curtain accelerator. An optimum structure of groupware and parameters of its heat source W wire have been designed. An uniform temperature distribution of 1 400~1 430℃ on the narrow planar LaB6 cathode has been predicted, which is enough to emit sufficient electron beam. In order to insure exact thermal physical parameters (such as heat emissivity and heat conductivity) of all the materials, an additional iterative algorithm is adopted. It takes only four iterations to get the convergent result. The method makes analysis process more efficient and compact. Experiment has proved the validity．
The finite element method (FEM) is introduced to design a structure of cathode groupware for an electron curtain accelerator. An optimum structure of groupware and parameters of its heat source W wire have been designed. An uniform temperature distribution of 1 400~1 430℃ on the narrow planar LaB6 cathode has been predicted, which is enough to emit sufficient electron beam. In order to insure exact thermal physical parameters (such as heat emissivity and heat conductivity) of all the materials, an additional iterative algorithm is adopted. It takes only four iterations to get the convergent result. The method makes analysis process more efficient and compact. Experiment has proved the validity．
2004,
16.
Abstract:
Modified three gradient method is a method to measure beam emittance developed from three gradient method which has been widely used in beam diagnostics. Beam radius' evolution versus focusing current can be fitted by a cross-over curve calculated from the K-V envelope equation through which the cross-over curve depends on beam radius, divergence in the initial plane and beam emittance. An approximation of the emittance can be got by the fitting program. In this paper beam radius under different focusing current was measured with Cerenkov radiation method; Time-resolved beam profile was recorded by a streak camera; A numerical fitting program, based on the K-V equation, was developed; Influence of beam radius and divergence in the initial plane and emittance on the cross-over curve were st
Modified three gradient method is a method to measure beam emittance developed from three gradient method which has been widely used in beam diagnostics. Beam radius' evolution versus focusing current can be fitted by a cross-over curve calculated from the K-V envelope equation through which the cross-over curve depends on beam radius, divergence in the initial plane and beam emittance. An approximation of the emittance can be got by the fitting program. In this paper beam radius under different focusing current was measured with Cerenkov radiation method; Time-resolved beam profile was recorded by a streak camera; A numerical fitting program, based on the K-V equation, was developed; Influence of beam radius and divergence in the initial plane and emittance on the cross-over curve were st
2004,
16.
Abstract:
An intelligent tuning system for the high current LIA is being designed at Laboratory of Accelerator Physics and Application, Institute of Fluid Physics. The goal to build the system is to adjust the beam centroid trajectory automatically for “Dragon - I”, which is a 20MeV, 2.5kA, 60ns pulsed electron LIA under construction. The simulation results show that to obtain pulsed electron beams with good quality and to reduce corkscrew amplitude, beam trajectory tuning is necessary. Three tuning methods adopted in the system are tuning manually, computer clone tuning and intelligent tuning. Both simulation and experiments have been performed to obtain the tuning curve of the first steering coil in the first cell. Details of the design, the tuning strategy and some of the tuning simulation and
An intelligent tuning system for the high current LIA is being designed at Laboratory of Accelerator Physics and Application, Institute of Fluid Physics. The goal to build the system is to adjust the beam centroid trajectory automatically for “Dragon - I”, which is a 20MeV, 2.5kA, 60ns pulsed electron LIA under construction. The simulation results show that to obtain pulsed electron beams with good quality and to reduce corkscrew amplitude, beam trajectory tuning is necessary. Three tuning methods adopted in the system are tuning manually, computer clone tuning and intelligent tuning. Both simulation and experiments have been performed to obtain the tuning curve of the first steering coil in the first cell. Details of the design, the tuning strategy and some of the tuning simulation and
2004,
16.
Abstract:
To extend the switch lifetime by minimizing electrode erosion, rotary arc gapswitches (RAG) were proposed. The rotation of the arc can be achieved by providing an external rotating magnetic field from outside or by self-induced magnetic field. Since the railgap switch has the advantages of low impedance, long burn-out life, wide operating range and low jitter time. Combining the RAG and rail-gap together, a switch were designed, and the characteristic of the switch has been studied by experment. The switch has low jitter and wide operating voltage range. The results indicate that the RAG switch employing a sharp knifeedge electrode as a third trigger electrode can distinctly reduce the electrode erosion and prolong the lifetime. The surface conditions and photomicrographs of the elec
To extend the switch lifetime by minimizing electrode erosion, rotary arc gapswitches (RAG) were proposed. The rotation of the arc can be achieved by providing an external rotating magnetic field from outside or by self-induced magnetic field. Since the railgap switch has the advantages of low impedance, long burn-out life, wide operating range and low jitter time. Combining the RAG and rail-gap together, a switch were designed, and the characteristic of the switch has been studied by experment. The switch has low jitter and wide operating voltage range. The results indicate that the RAG switch employing a sharp knifeedge electrode as a third trigger electrode can distinctly reduce the electrode erosion and prolong the lifetime. The surface conditions and photomicrographs of the elec
2004,
16.
Abstract:
In this work, TiNi shape memory alloy films on oxidized single crystal Si substrate were successfully prepared by cosputtering of TiNi target with a separated Ti target. The transformation behavior was investigated by differential scanning calorimeter (DSC) and in-situ XRD. 60 keV H+ ions implantation shifted martensite transformation start/finish temperature Ms/Mf and austenite transformation start/finish temperature As/Af to lower temperature, whereas H+ implantation had little effect on the Rphase transformation temperatures Rs and Rf. glance incidence XRD results showed that titanium hydride formed after H+ implantation .The change of transformation temperatures can be attributed to the formation of hydride．
In this work, TiNi shape memory alloy films on oxidized single crystal Si substrate were successfully prepared by cosputtering of TiNi target with a separated Ti target. The transformation behavior was investigated by differential scanning calorimeter (DSC) and in-situ XRD. 60 keV H+ ions implantation shifted martensite transformation start/finish temperature Ms/Mf and austenite transformation start/finish temperature As/Af to lower temperature, whereas H+ implantation had little effect on the Rphase transformation temperatures Rs and Rf. glance incidence XRD results showed that titanium hydride formed after H+ implantation .The change of transformation temperatures can be attributed to the formation of hydride．
