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RSS2008 Vol. 20, No. 03
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2008,
20.
Abstract:
Using the model of self-consistent for transport dynamics in semiconductors, taking the silicon film as example, the temperature effects on the heat capacity of carrier and lattice, thermal conductivity, relaxation time have been studied with a finite difference method. The primary researches in this paper are on the thermal response of 2 μm Si film irradiated by 500 fs laser pulse. The numerical results indicate that after having been heated for 0.69 ps, the maximum electron temperature at the front surface occurs, after about 4.8 ps the temperature is nearly thermally equilibrated. The temperature of carriers change is rapidly because the heat capacity of carrier changes rapidly. The linear absorption and the rate of change of the carrier energy density due to the changes of the carrier
Using the model of self-consistent for transport dynamics in semiconductors, taking the silicon film as example, the temperature effects on the heat capacity of carrier and lattice, thermal conductivity, relaxation time have been studied with a finite difference method. The primary researches in this paper are on the thermal response of 2 μm Si film irradiated by 500 fs laser pulse. The numerical results indicate that after having been heated for 0.69 ps, the maximum electron temperature at the front surface occurs, after about 4.8 ps the temperature is nearly thermally equilibrated. The temperature of carriers change is rapidly because the heat capacity of carrier changes rapidly. The linear absorption and the rate of change of the carrier energy density due to the changes of the carrier
2008,
20.
Abstract:
According to American ANSI criterion, different laser pulse divergence angle and laser pulse’s eye-safe maximal energy ratio in altitude of 0 to 12 km are simulated. Two schemes about laser pulse’s eye-safe maximal energy distribution of 532 nm and 1 064 nm wavelength are provided: (1) laser beam divergence angle is 0.3 mrad, maximal threshold energy ratio of 532 and 1 064 nm lasers is 1∶2. (2) laser beam divergence angle is 0.4 mrad, maximal threshold energy ratio of 532 and 1 064 nm lasers is 1∶1. Signal-to-noise ratio for mode atmosphere detection using the two schemes are also analyzed. Analysis shows that the two schemes can ensure both eye safety on the ground and measuring quality.
According to American ANSI criterion, different laser pulse divergence angle and laser pulse’s eye-safe maximal energy ratio in altitude of 0 to 12 km are simulated. Two schemes about laser pulse’s eye-safe maximal energy distribution of 532 nm and 1 064 nm wavelength are provided: (1) laser beam divergence angle is 0.3 mrad, maximal threshold energy ratio of 532 and 1 064 nm lasers is 1∶2. (2) laser beam divergence angle is 0.4 mrad, maximal threshold energy ratio of 532 and 1 064 nm lasers is 1∶1. Signal-to-noise ratio for mode atmosphere detection using the two schemes are also analyzed. Analysis shows that the two schemes can ensure both eye safety on the ground and measuring quality.
2008,
20.
Abstract:
A threefaced rotating mirror with honeycomb cellular structure in the ultra-high speed camera was presented in this paper, and the mechanical traits of such a structural three-faced aluminous rotating mirror were analyzed by use of FEM. The data indicate that the ultimate deformation magnitude of the mirror surface with width 17.325 mm and length 32.5 mm is 0.547 μm under the rotating speed of 5×104 r/min which is 16% times of nonhoneycomb cellular rotating mirror, the same with the beryllium rotating mirror, and the ultimate stress in this mirror is smaller than that of the former aluminous mirror．
A threefaced rotating mirror with honeycomb cellular structure in the ultra-high speed camera was presented in this paper, and the mechanical traits of such a structural three-faced aluminous rotating mirror were analyzed by use of FEM. The data indicate that the ultimate deformation magnitude of the mirror surface with width 17.325 mm and length 32.5 mm is 0.547 μm under the rotating speed of 5×104 r/min which is 16% times of nonhoneycomb cellular rotating mirror, the same with the beryllium rotating mirror, and the ultimate stress in this mirror is smaller than that of the former aluminous mirror．
2008,
20.
Abstract:
To suppress intrinsic noise and improve signal-to-noise in the interferometric system, a new light source named ring source is described. The reason that the ring source can reduce the intrinsic noise while preserving the fringe contrast of the interferogram is given. Using the fringe contrast and the spatial frequency of the intrinsic noise, the outer and inner radii of the ring source are obtained. Experiments of comparing with traditional point source show that ring source can suppress coherent noise effectively and preserve the fringe contrast. The power spectral density of intrinsic noise is less than one tenth that of point source at spatial frequency less than 2.5 mm-1 and the signal-to-noise ratio is more than twice that of point source at spatial frequency less than 2 mm-1.
To suppress intrinsic noise and improve signal-to-noise in the interferometric system, a new light source named ring source is described. The reason that the ring source can reduce the intrinsic noise while preserving the fringe contrast of the interferogram is given. Using the fringe contrast and the spatial frequency of the intrinsic noise, the outer and inner radii of the ring source are obtained. Experiments of comparing with traditional point source show that ring source can suppress coherent noise effectively and preserve the fringe contrast. The power spectral density of intrinsic noise is less than one tenth that of point source at spatial frequency less than 2.5 mm-1 and the signal-to-noise ratio is more than twice that of point source at spatial frequency less than 2 mm-1.
2008,
20.
Abstract:
A mathematic model of passive self-Q-switched microchip laser under pre-pumping mechanisms was presented. Using this model, the repetition rate, pulse width and peak power of laser pulses train were accurately obtained under given pumping conditions. In order to examine the model, the experiments of pre-pumping passive Q-switched Cr4+,Nd3+:YAG lasers were designed under corresponding pumping conditions. The experimental results agree well with the numerical simulation results. It illuminates that peak power of the laser pulses increases along with the rising of entire pumping rate; however, laser pulse width decreases as the entire pumping rate rises. Both speeds of decrease and increase slow down when the entire pumping rate goes far from the threshold. Moreover, the deviation between the
A mathematic model of passive self-Q-switched microchip laser under pre-pumping mechanisms was presented. Using this model, the repetition rate, pulse width and peak power of laser pulses train were accurately obtained under given pumping conditions. In order to examine the model, the experiments of pre-pumping passive Q-switched Cr4+,Nd3+:YAG lasers were designed under corresponding pumping conditions. The experimental results agree well with the numerical simulation results. It illuminates that peak power of the laser pulses increases along with the rising of entire pumping rate; however, laser pulse width decreases as the entire pumping rate rises. Both speeds of decrease and increase slow down when the entire pumping rate goes far from the threshold. Moreover, the deviation between the
2008,
20.
Abstract:
Characteristics of X-ray and spout direction of heat plasma flow were studied on Shenguang-Ⅱ laser facility. Using of pinhole X-ray camera, X-ray photons from the plasma of aluminum (Al) irradiated by 1.053 μm laser, was measured and analysed. It is observed that the spatial distribution of X-ray photons in Al plasma for tilted irradiation is symmetic at the center of the target. The spout direction of heat plasma flow is inferred by the distribution contour of X-ray photons. The experimental results show that the spout direction of heat plasma flow is normal to target plane and the output intensity of X-ray photons does not increase significantly for tilted laser incidence. Uniformity of laser energy deposition is improved by superposing tilted incident and laser perpendicularly incide
Characteristics of X-ray and spout direction of heat plasma flow were studied on Shenguang-Ⅱ laser facility. Using of pinhole X-ray camera, X-ray photons from the plasma of aluminum (Al) irradiated by 1.053 μm laser, was measured and analysed. It is observed that the spatial distribution of X-ray photons in Al plasma for tilted irradiation is symmetic at the center of the target. The spout direction of heat plasma flow is inferred by the distribution contour of X-ray photons. The experimental results show that the spout direction of heat plasma flow is normal to target plane and the output intensity of X-ray photons does not increase significantly for tilted laser incidence. Uniformity of laser energy deposition is improved by superposing tilted incident and laser perpendicularly incide
2008,
20.
Abstract:
X-ray spectrograph with a cylindrical curved convex crystal was designed for wire array Z-pinch experiments. Taking into consideration the effect of X-ray source size and rocking curve of crystal, ray tracing techniques were used for exploring the dispersion, spectral resolution, spatial resolution and their dependences on parameters of the spectrograph. The results show that size of X-ray source and its distance to the crystal influence spectral resolutions more than the other parameters. Increasing this distance improves the spectral resolution, but worsens spatial resolving power. A mica crystal spectrograph was then tested successfully on “Qiangguang-Ⅰ” pulsed power facility. Time integrated X-ray spectrographs of aluminum wire array Z-pinch plasmas were recorded.
X-ray spectrograph with a cylindrical curved convex crystal was designed for wire array Z-pinch experiments. Taking into consideration the effect of X-ray source size and rocking curve of crystal, ray tracing techniques were used for exploring the dispersion, spectral resolution, spatial resolution and their dependences on parameters of the spectrograph. The results show that size of X-ray source and its distance to the crystal influence spectral resolutions more than the other parameters. Increasing this distance improves the spectral resolution, but worsens spatial resolving power. A mica crystal spectrograph was then tested successfully on “Qiangguang-Ⅰ” pulsed power facility. Time integrated X-ray spectrographs of aluminum wire array Z-pinch plasmas were recorded.
2008,
20.
Abstract:
Characteristics of X-ray and spout direction of heat plasma flow were studied on Shenguang-Ⅱ laser facility. Using of pinhole X-ray camera, X-ray photons from the plasma of aluminum (Al) irradiated by 1.053 μm laser, was measured and analysed. It is observed that the spatial distribution of X-ray photons in Al plasma for tilted irradiation is symmetic at the center of the target. The spout direction of heat plasma flow is inferred by the distribution contour of X-ray photons. The experimental results show that the spout direction of heat plasma flow is normal to target plane and the output intensity of X-ray photons does not increase significantly for tilted laser incidence. Uniformity of laser energy deposition is improved by superposing tilted incident and laser perpendicularly incide
Characteristics of X-ray and spout direction of heat plasma flow were studied on Shenguang-Ⅱ laser facility. Using of pinhole X-ray camera, X-ray photons from the plasma of aluminum (Al) irradiated by 1.053 μm laser, was measured and analysed. It is observed that the spatial distribution of X-ray photons in Al plasma for tilted irradiation is symmetic at the center of the target. The spout direction of heat plasma flow is inferred by the distribution contour of X-ray photons. The experimental results show that the spout direction of heat plasma flow is normal to target plane and the output intensity of X-ray photons does not increase significantly for tilted laser incidence. Uniformity of laser energy deposition is improved by superposing tilted incident and laser perpendicularly incide
2008,
20.
Abstract:
Hot electron spectrum in the interaction of femtosecond laser with solid target was measured by experiment on the 100 TW laser. The energy spectrum, yield, fluence and energy deposit range of hot electron transport in target were obtained. It is shown that the fluence and total energy of hot electrons decreases with the increase of target thickness, 80％ hot electrons energy deposits in the place infront of the target about pulse width of femtosecond laser, and energy deposit range of hot electrons increases with the increase of pulse width of femtosecond laser, which is induced by the static electric field effect.
Hot electron spectrum in the interaction of femtosecond laser with solid target was measured by experiment on the 100 TW laser. The energy spectrum, yield, fluence and energy deposit range of hot electron transport in target were obtained. It is shown that the fluence and total energy of hot electrons decreases with the increase of target thickness, 80％ hot electrons energy deposits in the place infront of the target about pulse width of femtosecond laser, and energy deposit range of hot electrons increases with the increase of pulse width of femtosecond laser, which is induced by the static electric field effect.
2008,
20.
Abstract:
Single layers of MgF2 were deposited upon super polished fused-silica substrates by resistance boat evaporation at different temperatures from 200 ℃ to 350 ℃ by increasing step of 50 ℃. The transmittance and reflectance spectra were measured and the root-mean-square surface roughness was determined. The total optical loss and scattering loss were calculated. The laser-induced damage threshold(LIDT) was characterized at the wavelength of 355 nm for certain samples. It was found that the total optical loss and the root-mean-square surface roughness increased with the increasing of the deposition temperature. At the short wavelength period the increasing total optical loss at certain deposition temperature was mainly caused by absorption while scattering loss occupied a very low percentage
Single layers of MgF2 were deposited upon super polished fused-silica substrates by resistance boat evaporation at different temperatures from 200 ℃ to 350 ℃ by increasing step of 50 ℃. The transmittance and reflectance spectra were measured and the root-mean-square surface roughness was determined. The total optical loss and scattering loss were calculated. The laser-induced damage threshold(LIDT) was characterized at the wavelength of 355 nm for certain samples. It was found that the total optical loss and the root-mean-square surface roughness increased with the increasing of the deposition temperature. At the short wavelength period the increasing total optical loss at certain deposition temperature was mainly caused by absorption while scattering loss occupied a very low percentage
2008,
20.
Abstract:
MgF2 anti-reflective thin films were successfully prepared in methanol media via sol-gel process using magnesium acetate and hydrofluoric acid as reactants. The influence of processing temperature on MgF2 sols was investigated. As-synthesized MgF2 sol was used to deposit AR films on quartz substrate, which could be applied for 355 nm UV laser. The results showed that MgF2 thin films had low refractive index, small surface roughness and good anti-reflective property in the UV region and high laser-induced damage threshold (LIDT) at 355 nm (6 ns pulses). The refractive index at 355 nm wavelength of film decreased with the increase of processing temperature. The transmittance and LIDT of quartz substrate with double-side MgF2 films both reached the maximum value, that is, 99.4% for transmitta
MgF2 anti-reflective thin films were successfully prepared in methanol media via sol-gel process using magnesium acetate and hydrofluoric acid as reactants. The influence of processing temperature on MgF2 sols was investigated. As-synthesized MgF2 sol was used to deposit AR films on quartz substrate, which could be applied for 355 nm UV laser. The results showed that MgF2 thin films had low refractive index, small surface roughness and good anti-reflective property in the UV region and high laser-induced damage threshold (LIDT) at 355 nm (6 ns pulses). The refractive index at 355 nm wavelength of film decreased with the increase of processing temperature. The transmittance and LIDT of quartz substrate with double-side MgF2 films both reached the maximum value, that is, 99.4% for transmitta
2008,
20.
Abstract:
A new flux-resolution optical design method of Kirkpatrick-Baez microscope (KB microscope) is proposed. In X-ray imaging diagnostics of inertial confinement fusion(ICF), spatial resolution and flux are always the key parameters. While the traditional optical design of KB microscope is to correct on-axis spherical aberration and astigmatic aberration, flux-resolution method is based on lateral aberration of full field and astigmatic aberration. Thus the spatial resolution related to field dimension and light flux can be estimated. By the expressions of spatial resolution and actual limits in ICF, rules of how to set original structure and optical design flow are summarized. An instance is presented and it shows that the design has met the original targets and overcome the shortcomings of im
A new flux-resolution optical design method of Kirkpatrick-Baez microscope (KB microscope) is proposed. In X-ray imaging diagnostics of inertial confinement fusion(ICF), spatial resolution and flux are always the key parameters. While the traditional optical design of KB microscope is to correct on-axis spherical aberration and astigmatic aberration, flux-resolution method is based on lateral aberration of full field and astigmatic aberration. Thus the spatial resolution related to field dimension and light flux can be estimated. By the expressions of spatial resolution and actual limits in ICF, rules of how to set original structure and optical design flow are summarized. An instance is presented and it shows that the design has met the original targets and overcome the shortcomings of im
2008,
20.
Abstract:
Based on interfacial polymerization reaction, PS-RF double shell microspheres were synthesized using polystyrene (PS) hollow microspheres as template, RF solution as precursor and dibutyl phthalate as dispersant. The factors, such as the choice of RF solution and oil, prepolymerization time, stirring rate and solidification temperature, which affect the process, have been preliminarily discussed. As the polymerization reaction was occurring in the following conditions: RF solution was 25%, the molar ratio of resorcinol to sodium carbonate was 100, prepolymerization time was 24 hours, stirring rate was 120～200 r/min, and solidification temperature was 35 ℃, the experiment has fabricated PS-RF double-layered hollow microsphere, whose degree of sphericity and concentricity are over 95% and
Based on interfacial polymerization reaction, PS-RF double shell microspheres were synthesized using polystyrene (PS) hollow microspheres as template, RF solution as precursor and dibutyl phthalate as dispersant. The factors, such as the choice of RF solution and oil, prepolymerization time, stirring rate and solidification temperature, which affect the process, have been preliminarily discussed. As the polymerization reaction was occurring in the following conditions: RF solution was 25%, the molar ratio of resorcinol to sodium carbonate was 100, prepolymerization time was 24 hours, stirring rate was 120～200 r/min, and solidification temperature was 35 ℃, the experiment has fabricated PS-RF double-layered hollow microsphere, whose degree of sphericity and concentricity are over 95% and
2008,
20.
Abstract:
In this paper, Nb films with different thicknesses were fabricated by DC magnetron sputtering. The deposition rate, surface roughness, crystal structure of Nb films at different sputtering thicknesses were studied, and the RMS roughness of the Nb film was in 1×10-1 nm level. The stress and preferred orientation of Nb films were studied. The AFM images showed that the films were compact and smooth. The X-ray diffraction results indicated that Nb films were body-centered cubic structure with a preferred orientation of (110). The stress in the Nb films increased with the increase of the thickness of Nb film and reached a maximum of 1.015 1 GPa when the thickness was 200 nm, after that the stress decreased with the increase of the thickness of the Nb film.
In this paper, Nb films with different thicknesses were fabricated by DC magnetron sputtering. The deposition rate, surface roughness, crystal structure of Nb films at different sputtering thicknesses were studied, and the RMS roughness of the Nb film was in 1×10-1 nm level. The stress and preferred orientation of Nb films were studied. The AFM images showed that the films were compact and smooth. The X-ray diffraction results indicated that Nb films were body-centered cubic structure with a preferred orientation of (110). The stress in the Nb films increased with the increase of the thickness of Nb film and reached a maximum of 1.015 1 GPa when the thickness was 200 nm, after that the stress decreased with the increase of the thickness of the Nb film.
2008,
20.
Abstract:
A calibration method of absolute response for TianjinⅢ X-ray film on Beijing Synchrotron Radiation Facility was introduced. In experiment,a shutter and standard detector were used to control the exposure time and integrated light intensity, hence the absolute light intensity recorded by the film could be obtained, and optical density was obtained by scanning the film with densitometer. In data processing, the shutter response was calibrated and the non-homogeneous source distribution was studied, which could reduce the uncertainty of light intensity. The experimental data of the absolute response between absolute light intensity and the optical density at photo energy of 1keV and 1.5keV were obtained respectively, the experimental results were fitted with Henke’s theoretic formula to obt
A calibration method of absolute response for TianjinⅢ X-ray film on Beijing Synchrotron Radiation Facility was introduced. In experiment,a shutter and standard detector were used to control the exposure time and integrated light intensity, hence the absolute light intensity recorded by the film could be obtained, and optical density was obtained by scanning the film with densitometer. In data processing, the shutter response was calibrated and the non-homogeneous source distribution was studied, which could reduce the uncertainty of light intensity. The experimental data of the absolute response between absolute light intensity and the optical density at photo energy of 1keV and 1.5keV were obtained respectively, the experimental results were fitted with Henke’s theoretic formula to obt
2008,
20.
Abstract:
N,N′-diphenyl glyoxaline-3, 4, 9, 10-perylene tetracarboxylic diimide(PV) was synthesized from perylene-3,4,9,10-tetracarboxylic acid bisanhydride and o-phenylenediamine. The product was purified by vacuum sublimation with 68% yield and more than 95% purity and characterized by FTIR, UV/Vis, elemental analysis and TG. Results showed that PV could be easily obtained from PTCDA with high yield. UV/Vis spectra of PV’s DMF solution had two strong absorption peaks in 450 to 750 nm. The onset decomposition temperature of PV was about 510 ℃, which indicates that PV has high thermal stabilization.
N,N′-diphenyl glyoxaline-3, 4, 9, 10-perylene tetracarboxylic diimide(PV) was synthesized from perylene-3,4,9,10-tetracarboxylic acid bisanhydride and o-phenylenediamine. The product was purified by vacuum sublimation with 68% yield and more than 95% purity and characterized by FTIR, UV/Vis, elemental analysis and TG. Results showed that PV could be easily obtained from PTCDA with high yield. UV/Vis spectra of PV’s DMF solution had two strong absorption peaks in 450 to 750 nm. The onset decomposition temperature of PV was about 510 ℃, which indicates that PV has high thermal stabilization.
2008,
20.
Abstract:
The output cavity with abrupt changes in radius for gyroklystron is studied using the mode-matching technique to build scattering matrix. A FORTRAN code is developed to calculate the scattering matrix. The effects of the cavity’s length and radius, the coupling aperture’s radius and thickness on the resonance characteristics of output cavity for Ka-band TE01 gyroklystron are analyzed. At the same time, the high frequency field distribution in the cavity is presented. The simulation result of output cavity obtained by the code shows good agreement with HFSS code simulation. Comparing the simulation result with the cold-test experimental result, the difference of quality factor is only 1.65% and the deviation of resonance frequency is 10 MHz.
The output cavity with abrupt changes in radius for gyroklystron is studied using the mode-matching technique to build scattering matrix. A FORTRAN code is developed to calculate the scattering matrix. The effects of the cavity’s length and radius, the coupling aperture’s radius and thickness on the resonance characteristics of output cavity for Ka-band TE01 gyroklystron are analyzed. At the same time, the high frequency field distribution in the cavity is presented. The simulation result of output cavity obtained by the code shows good agreement with HFSS code simulation. Comparing the simulation result with the cold-test experimental result, the difference of quality factor is only 1.65% and the deviation of resonance frequency is 10 MHz.
2008,
20.
Abstract:
Radial line helical rectangular array antenna is a new antenna which realizes the directional radiation of circularly polarized microwave, and can be easily assembled to a high gain antenna. In this paper, the fundamental theory is introduced, and a helical rectangular array antenna of 16-element using two kinds of coupling probes is put forward. The numerical simulation result shows that at 4.0 GHz, the gain of the antenna is 18.24 dB and the axial ratio at the normal direction is 1.065. In the range of 3.8 GHz to 4.2 GHz, the gain is greater than 17.89 dB, the axial ratio is below 1.2, the voltage standing wave ratio is below 1.3, and the aperture efficiency is over 85%.
Radial line helical rectangular array antenna is a new antenna which realizes the directional radiation of circularly polarized microwave, and can be easily assembled to a high gain antenna. In this paper, the fundamental theory is introduced, and a helical rectangular array antenna of 16-element using two kinds of coupling probes is put forward. The numerical simulation result shows that at 4.0 GHz, the gain of the antenna is 18.24 dB and the axial ratio at the normal direction is 1.065. In the range of 3.8 GHz to 4.2 GHz, the gain is greater than 17.89 dB, the axial ratio is below 1.2, the voltage standing wave ratio is below 1.3, and the aperture efficiency is over 85%.
2008,
20.
Abstract:
According to the requirement of miniaturization, a kind of radiation antenna model integrated with mode converter for the compact L-band magnetically insulated transmission line oscillator(MILO) is put forward. The model uses dielectric and metal board for phase shift. It can greatly shorten the physical length of the mode converter. Based on this model, an integrated radiation antenna is investigated. The radiation antenna is designed and optimized by numerical calculation. The antenna’s characteristics such as far-field patterns, gains and physical length are also obtained.
According to the requirement of miniaturization, a kind of radiation antenna model integrated with mode converter for the compact L-band magnetically insulated transmission line oscillator(MILO) is put forward. The model uses dielectric and metal board for phase shift. It can greatly shorten the physical length of the mode converter. Based on this model, an integrated radiation antenna is investigated. The radiation antenna is designed and optimized by numerical calculation. The antenna’s characteristics such as far-field patterns, gains and physical length are also obtained.
2008,
20.
Abstract:
To protect electronic systems against high power microwave, a plasma waveguide limiter is presented. The threshold breakdown electric fields of He, Ne, Ar, Xe and H2, which are filled in the limiter, are deduced as a function of gas pressure and microwave frequency. Under high pressure (1 333~133 320 Pa), the breakdown fields increase as pressure increases, and Ne has the lowest breakdown field compared with the other gases. Under low pressure (1.333 2~133.32 Pa), the breakdown fields decrease as pressure increases, and Xe has the lowest breakdown field. The breakdown field of gases under high pressure is higher than that of gases under low pressure. The calculation results show that the limiter filled with Xe with pressure about 133.32 Pa can protect the electronic systems against high p
To protect electronic systems against high power microwave, a plasma waveguide limiter is presented. The threshold breakdown electric fields of He, Ne, Ar, Xe and H2, which are filled in the limiter, are deduced as a function of gas pressure and microwave frequency. Under high pressure (1 333~133 320 Pa), the breakdown fields increase as pressure increases, and Ne has the lowest breakdown field compared with the other gases. Under low pressure (1.333 2~133.32 Pa), the breakdown fields decrease as pressure increases, and Xe has the lowest breakdown field. The breakdown field of gases under high pressure is higher than that of gases under low pressure. The calculation results show that the limiter filled with Xe with pressure about 133.32 Pa can protect the electronic systems against high p
2008,
20.
Abstract:
Obtaining long-pulse high power microwave(HPM) is one of the most important aims for HPM sources technology. In the paper, difficulties in generating long pulse HPM for sources using slow-wave structures are discussed from the view point of physical mechanism, and some suggestions are given. By using of a long pulse pulsed power driver and an overmoded slow-wave structure HPM source, X-band long pulse HPM generating experiments were carried out. In the experiments, a kind of dielectric-copper cathode was adopted and the slow-wave structures of the HPM device were coated with Cr film. Under the condition of guiding magnetic field of 0.7 T, diode voltage of 400 kV，beam current of 10 kA with duration of 200 ns, an X-band long pulse HPM was obtained with power of 500 MW, duration of 100 ns an
Obtaining long-pulse high power microwave(HPM) is one of the most important aims for HPM sources technology. In the paper, difficulties in generating long pulse HPM for sources using slow-wave structures are discussed from the view point of physical mechanism, and some suggestions are given. By using of a long pulse pulsed power driver and an overmoded slow-wave structure HPM source, X-band long pulse HPM generating experiments were carried out. In the experiments, a kind of dielectric-copper cathode was adopted and the slow-wave structures of the HPM device were coated with Cr film. Under the condition of guiding magnetic field of 0.7 T, diode voltage of 400 kV，beam current of 10 kA with duration of 200 ns, an X-band long pulse HPM was obtained with power of 500 MW, duration of 100 ns an
2008,
20.
Abstract:
The linear kinetic theory and nonlinear self-consistent model for outer-slotted-coaxial waveguide cyclotron autoresonance maser(CARM) amplifiers with axis-encircling beam are presented. Good agreement is found between the simulations and the kinetic theory in the linear regime. The choice of the electron beam current is discussed for suppressing the absolute instability. Using a 700 kV, 100 A axis-encircling beam with electron beam velocity pitch of 0.8, nonlinear self-consistent analysis predicts that TE51 CARM amplifier can have a peak output power of 6.27 MW and a peak efficiency of 8.96 %.
The linear kinetic theory and nonlinear self-consistent model for outer-slotted-coaxial waveguide cyclotron autoresonance maser(CARM) amplifiers with axis-encircling beam are presented. Good agreement is found between the simulations and the kinetic theory in the linear regime. The choice of the electron beam current is discussed for suppressing the absolute instability. Using a 700 kV, 100 A axis-encircling beam with electron beam velocity pitch of 0.8, nonlinear self-consistent analysis predicts that TE51 CARM amplifier can have a peak output power of 6.27 MW and a peak efficiency of 8.96 %.
2008,
20.
Abstract:
The two dimensional photonic crystal cavities are simulated using Ansoft HFSS. Some significant parameters and factors that affect the characteristics of photonic crystal cavity, including the spatial structure of the inserted rods, the permittivity of dielectric rods, the radii and distance of rods etc, are analyzed. At the same time, the general discipline is summarized. The results show that when the radii of the dielectric rods increase, the frequency of the same mode will increase, and in the high order mode, it has a minimal value when the rod radius is 0.4 mm. When the permittivities of dielectric rods increase, the number of regular modes decrease. Further more, there is no fundamental mode which is important for using high order mode only. Considering only the change of the distan
The two dimensional photonic crystal cavities are simulated using Ansoft HFSS. Some significant parameters and factors that affect the characteristics of photonic crystal cavity, including the spatial structure of the inserted rods, the permittivity of dielectric rods, the radii and distance of rods etc, are analyzed. At the same time, the general discipline is summarized. The results show that when the radii of the dielectric rods increase, the frequency of the same mode will increase, and in the high order mode, it has a minimal value when the rod radius is 0.4 mm. When the permittivities of dielectric rods increase, the number of regular modes decrease. Further more, there is no fundamental mode which is important for using high order mode only. Considering only the change of the distan
Three dimensional analysis and simulation of input cavity for S-band relativistic klystron amplifier
2008,
20.
Abstract:
In this paper, high frequency characteristics analysis on an input cavity of an S-band relativistic klystron amplifier is presented. The influence of large coupling hole on symmetry and uniformity of the electric field in the gap region is discussed and a bias design in the input cavity is used to reduce the influence. The field in the gap region are sensitive to the coupling hole size and when the coupling hole is closer to the axis, the field in the gap region is more asymmetric. A three-dimension fully electromagnetic particle-in-cell(PIC) code is used to simulate the fundamental harmonic modulated current while the electron beam is propagating the input cavity gap. The simulation results show that the amplitude of the fundamental harmonic modulated current is relative to the gap voltag
In this paper, high frequency characteristics analysis on an input cavity of an S-band relativistic klystron amplifier is presented. The influence of large coupling hole on symmetry and uniformity of the electric field in the gap region is discussed and a bias design in the input cavity is used to reduce the influence. The field in the gap region are sensitive to the coupling hole size and when the coupling hole is closer to the axis, the field in the gap region is more asymmetric. A three-dimension fully electromagnetic particle-in-cell(PIC) code is used to simulate the fundamental harmonic modulated current while the electron beam is propagating the input cavity gap. The simulation results show that the amplitude of the fundamental harmonic modulated current is relative to the gap voltag
2008,
20.
Abstract:
Periodic permanent magnet focusing system for five-beam traveling-wave tube has been studied using the 3-D traveling-wave tubes simulation code developed by ourselves. Static magnetic field and beam transmission characteristics were analyzed . and the transverse magnetic field inside the outer beam tunnels and their effect on beam transmission were described. The results show that the PPM focusing system has good magnetic distribution and beam focusing capacity, when its structure is properly designed, the transverse magnetic field has little effect on outer tunnel beam transmission.
Periodic permanent magnet focusing system for five-beam traveling-wave tube has been studied using the 3-D traveling-wave tubes simulation code developed by ourselves. Static magnetic field and beam transmission characteristics were analyzed . and the transverse magnetic field inside the outer beam tunnels and their effect on beam transmission were described. The results show that the PPM focusing system has good magnetic distribution and beam focusing capacity, when its structure is properly designed, the transverse magnetic field has little effect on outer tunnel beam transmission.
2008,
20.
Abstract:
The characteristics of current induced by HEMP on cable’s shielding layer has been researched by multiresolution analysis in time domain. There are several factors, including height from cable to ground, length of cable and direction of incident HEMP, having effect on the current. The relationship between the induced current and the factors is analyzed. The analysis shows that, the higher the height from cable to ground is, the bigger the amplitude of the induced current is. It also indicates that, the amplitude, rising time and FWHM of the induced current are increasing while the length of the cable is getting longer until they all reach their own maxima. The distribution of the induced current along the cable with normal HEMP incidence is different from that with oblique incidence, and
The characteristics of current induced by HEMP on cable’s shielding layer has been researched by multiresolution analysis in time domain. There are several factors, including height from cable to ground, length of cable and direction of incident HEMP, having effect on the current. The relationship between the induced current and the factors is analyzed. The analysis shows that, the higher the height from cable to ground is, the bigger the amplitude of the induced current is. It also indicates that, the amplitude, rising time and FWHM of the induced current are increasing while the length of the cable is getting longer until they all reach their own maxima. The distribution of the induced current along the cable with normal HEMP incidence is different from that with oblique incidence, and
Analysis of higher-order modes of multipactor in magnetically insulated transmission line oscillator
2008,
20.
Abstract:
Based on the physical analysis of the multipactor for magnetically insulated transmission line oscillator (MILO)， the higher-order resonance modes of multipactor in MILO are analyzed and calculated.The results show that the susceptibility region, in which the multipactor occurs, of the higher-order resonance modes is much smaller than that of the basic resonance mode. so the multipactor discharge is more importance of the basic mode than of the higher-order modes．
Based on the physical analysis of the multipactor for magnetically insulated transmission line oscillator (MILO)， the higher-order resonance modes of multipactor in MILO are analyzed and calculated.The results show that the susceptibility region, in which the multipactor occurs, of the higher-order resonance modes is much smaller than that of the basic resonance mode. so the multipactor discharge is more importance of the basic mode than of the higher-order modes．
2008,
20.
Abstract:
A new low-impedance of HPM source called radial three-cavity transit time oscillator is proposed based on the transition radiation and the low-impedance character of the radial structure. The oscillator is consisted of three side-coupling coaxial cavities which have the same cavity height. Circle symmetrical models are designed to effect with the electrons which moving in the radial direction. Through the PIC simulation, A C-band oscillator is designed, and the average operation power of 7.4 GW at 4.1 GHz is obtained, when excited by a 450 keV, 60 kA radial electron beam, with an impedance of 7.5 Ω. The vital character lines are obtained by simulation. Analysis result reveals that the oscillator has the basic characters of the transit time effect, and is of a transition radiation oscillat
A new low-impedance of HPM source called radial three-cavity transit time oscillator is proposed based on the transition radiation and the low-impedance character of the radial structure. The oscillator is consisted of three side-coupling coaxial cavities which have the same cavity height. Circle symmetrical models are designed to effect with the electrons which moving in the radial direction. Through the PIC simulation, A C-band oscillator is designed, and the average operation power of 7.4 GW at 4.1 GHz is obtained, when excited by a 450 keV, 60 kA radial electron beam, with an impedance of 7.5 Ω. The vital character lines are obtained by simulation. Analysis result reveals that the oscillator has the basic characters of the transit time effect, and is of a transition radiation oscillat
2008,
20.
Abstract:
Ultra broadband radiation(UWB) performance of microwave radiated from plasma is introduced by this paper. Based on analysis of both current waveform and microwave signal waveform received by horn antenna, some factors referring to radiation mechanism are analyzed：there are TEM and TM modals of electromagnetic waves between cathode and anode; magnetic field excited by current flowing through the plasma itself makes the waves in plasma slow waves；there are two exciting factors, one is the electrons moving with acceleration, and the other is abruptly fall of anode voltage the caused by anode spots spray. The reason of broadband radiation is that the electrons with different velocities transfer energy to the waves of corresponding phase velocity.
Ultra broadband radiation(UWB) performance of microwave radiated from plasma is introduced by this paper. Based on analysis of both current waveform and microwave signal waveform received by horn antenna, some factors referring to radiation mechanism are analyzed：there are TEM and TM modals of electromagnetic waves between cathode and anode; magnetic field excited by current flowing through the plasma itself makes the waves in plasma slow waves；there are two exciting factors, one is the electrons moving with acceleration, and the other is abruptly fall of anode voltage the caused by anode spots spray. The reason of broadband radiation is that the electrons with different velocities transfer energy to the waves of corresponding phase velocity.
2008,
20.
Abstract:
The magnetic insulation establishment in a pulsed power transmission line has been analyzed. The analysis involves in the interaction and dependence between the breakdown of the transmission line and the magnetic insulation. It illustrates how the emission and the distribution patterns of the electrons contribute to the establishment of magnetic insulation. In addition, it shows how the distribution of electrons impacts the operating impedance of the transmission line. Based on the magnetic insulation steady-state models, an operating impedance calculation method is proposed using steady-state impedance to substitute the transient operating impedance. Through simulating transmission lines with varying radius, it is clarified that the regional operating impedances in different geometrical r
The magnetic insulation establishment in a pulsed power transmission line has been analyzed. The analysis involves in the interaction and dependence between the breakdown of the transmission line and the magnetic insulation. It illustrates how the emission and the distribution patterns of the electrons contribute to the establishment of magnetic insulation. In addition, it shows how the distribution of electrons impacts the operating impedance of the transmission line. Based on the magnetic insulation steady-state models, an operating impedance calculation method is proposed using steady-state impedance to substitute the transient operating impedance. Through simulating transmission lines with varying radius, it is clarified that the regional operating impedances in different geometrical r
2008,
20.
Abstract:
Principle of operation of the traditional magnetic pulse compression(MPC) system is described. A magnetic pulse compression system is presented which does not contain external remagnetization circuits that are commonly used in magnetic compressors. To understand the magnetic switch operation in detail and to model the performance of magnetic switch, a Pspice model of the MPC system is designed. Circuit analysis of compressor and charging system accounting for nonlinear processes in magnetic switches is presented. Typical timing diagrams of pulse compressor working on a 500 W resistive load illustrated that in order to realize the desired pulse, 6 ms and 500 ns magnetization period would be required for PT1 and MS1, respectively. Two compression stages suffice to form -27 kV, about 70 ns FW
Principle of operation of the traditional magnetic pulse compression(MPC) system is described. A magnetic pulse compression system is presented which does not contain external remagnetization circuits that are commonly used in magnetic compressors. To understand the magnetic switch operation in detail and to model the performance of magnetic switch, a Pspice model of the MPC system is designed. Circuit analysis of compressor and charging system accounting for nonlinear processes in magnetic switches is presented. Typical timing diagrams of pulse compressor working on a 500 W resistive load illustrated that in order to realize the desired pulse, 6 ms and 500 ns magnetization period would be required for PT1 and MS1, respectively. Two compression stages suffice to form -27 kV, about 70 ns FW
2008,
20.
Abstract:
A method of circuit simulation of magnetically insulated transmission line(MITL) driving a wire array to implode has been introduced. Based on TLCODE, an MITL has been divided into a lot of lossy transmission line elements, and each element comprises a segment of lossless transmission line and a grounded resistor. According to magnetic insulation theorem the element states were determined. For the state before magnetic insulation the loss current of each lossy element is calculated by the relationship between space-charge-limited(SCL) flow and conducting current, while for the state after magnetic insulation its loss current is determined by the impedance matching condition between two adjacent lossy elements. The equations describing the wire array to implode, the TLCODE equations, the fl
A method of circuit simulation of magnetically insulated transmission line(MITL) driving a wire array to implode has been introduced. Based on TLCODE, an MITL has been divided into a lot of lossy transmission line elements, and each element comprises a segment of lossless transmission line and a grounded resistor. According to magnetic insulation theorem the element states were determined. For the state before magnetic insulation the loss current of each lossy element is calculated by the relationship between space-charge-limited(SCL) flow and conducting current, while for the state after magnetic insulation its loss current is determined by the impedance matching condition between two adjacent lossy elements. The equations describing the wire array to implode, the TLCODE equations, the fl
2008,
20.
Abstract:
Based on laminar flow model, the analytical expression of the electromagnetic spatial distribution in the transmission line under the magnetically insulated stable state is presented from line voltage and current. On that basis, the equivalent inductance and capacitance of the transmission line under the magnetically insulated stable-state are calculated in consideration of the space charge effect for the improvement of unit model of circuit code. With the method presented by this paper, the equivalent inductance and capacitance of MITL-A of Z accelerator under magnetic insulated stable state are computed. The result shows that the equivalent capacitance increases with the enhancement of the space charge effect while the equivalent inductance decreases with the enhancement of the space-ele
Based on laminar flow model, the analytical expression of the electromagnetic spatial distribution in the transmission line under the magnetically insulated stable state is presented from line voltage and current. On that basis, the equivalent inductance and capacitance of the transmission line under the magnetically insulated stable-state are calculated in consideration of the space charge effect for the improvement of unit model of circuit code. With the method presented by this paper, the equivalent inductance and capacitance of MITL-A of Z accelerator under magnetic insulated stable state are computed. The result shows that the equivalent capacitance increases with the enhancement of the space charge effect while the equivalent inductance decreases with the enhancement of the space-ele
2008,
20.
Abstract:
There are special demands of detector for neutron stimulated emission computed tomography (NSECT). To discuss the possible application in NSECT, the performance of traditional array detector was presented through simulation. A correction method of summing additional signals from adjacent crystals was proposed based on the spectrum of single bismuth germanium oxide (BGO). The spectrum with correction becomes much better than previous one, and the spatial resolution obtained is also be appropriate.
There are special demands of detector for neutron stimulated emission computed tomography (NSECT). To discuss the possible application in NSECT, the performance of traditional array detector was presented through simulation. A correction method of summing additional signals from adjacent crystals was proposed based on the spectrum of single bismuth germanium oxide (BGO). The spectrum with correction becomes much better than previous one, and the spatial resolution obtained is also be appropriate.
2008,
20.
Abstract:
Pure Ti films were fabricated by bias sputtering. The deposition rate, the density and the surface topography of the Ti films at different negative bias were studied. The results show that the deposition rate is weakly affected when the bias power is low. As the bias voltage increases, the deposition rate decreases strongly due to the increase of the layer density and the resputtering phenomena. The film density increased and saturated to nearly bulk value at a bias voltage of -119.1 V. SEM view indicates that the columnar-type structure of Ti films can be destroyed by applying negative bias. The experiments demonstrated that a dense Ti film with more smooth surface can be produced by applying negative bias.
Pure Ti films were fabricated by bias sputtering. The deposition rate, the density and the surface topography of the Ti films at different negative bias were studied. The results show that the deposition rate is weakly affected when the bias power is low. As the bias voltage increases, the deposition rate decreases strongly due to the increase of the layer density and the resputtering phenomena. The film density increased and saturated to nearly bulk value at a bias voltage of -119.1 V. SEM view indicates that the columnar-type structure of Ti films can be destroyed by applying negative bias. The experiments demonstrated that a dense Ti film with more smooth surface can be produced by applying negative bias.
2008,
20.
Abstract:
1.064 μm pulsed laser induced ripple damage on SiO2 film which was deposited on K9 glass substrate by electron beam evaporation,was been investigated. The profile of K9 glass was analyzed by scan electronics microscope (SEM ), and the defects on the film were measured by using surface thermal lens (STL). The distribution of light reflected from these defects and bubbles was simulated by finite elements analysis. The experimental results showed that some defects was in the film, and lots of bubbles were found in the K9 glass as well. The simulated results showed that there were ripple damage structure was infected by the reflex laser, the width of stripes increased with the increase of the bubble depth. When the defects were erose, the ripple damage structure might become parallel. And wh
1.064 μm pulsed laser induced ripple damage on SiO2 film which was deposited on K9 glass substrate by electron beam evaporation,was been investigated. The profile of K9 glass was analyzed by scan electronics microscope (SEM ), and the defects on the film were measured by using surface thermal lens (STL). The distribution of light reflected from these defects and bubbles was simulated by finite elements analysis. The experimental results showed that some defects was in the film, and lots of bubbles were found in the K9 glass as well. The simulated results showed that there were ripple damage structure was infected by the reflex laser, the width of stripes increased with the increase of the bubble depth. When the defects were erose, the ripple damage structure might become parallel. And wh
2008,
20.
Abstract:
By getting insight into the main affecting factors on the property of streak image tube and keeping the designing orientation on the improvement of such three performance parameters as temporal resolution, spatial resolution and dynamic range, an optimized scheme is achieved with introduction of an auxiliary accelerating electrode in the neighborhood of fluorescent screen. It is an equal-diameter spiral dielectric electrode, which can bring about a uniform axial accelerating field. Correspording discussion indicates that the electrode can optimize the performance of streak image tube in the following aspects: increasing the screen-intersected velocity of electrons and hence the screen brightness, decreasing the transition time span and relevant dispersion between the deflection plates and
By getting insight into the main affecting factors on the property of streak image tube and keeping the designing orientation on the improvement of such three performance parameters as temporal resolution, spatial resolution and dynamic range, an optimized scheme is achieved with introduction of an auxiliary accelerating electrode in the neighborhood of fluorescent screen. It is an equal-diameter spiral dielectric electrode, which can bring about a uniform axial accelerating field. Correspording discussion indicates that the electrode can optimize the performance of streak image tube in the following aspects: increasing the screen-intersected velocity of electrons and hence the screen brightness, decreasing the transition time span and relevant dispersion between the deflection plates and
2008,
20.
Abstract:
The ratios of good event, energy deposition of gamma and neutron with different offsets are obtained by the model of pinhole imaging based on Geant4 system. The effect on the point spread function(PSF) of neutron pinhole imaging caused by the high gamma ray background is simulated and analyzed. The results show that with the offsets less than 1 cm the ratios of good event, peak value of energy deposition, total energy deposition of gamma and neutron are 0.40~0.42, 0.63~0.65, 0.46~0.49, respectively; with the offsets greater than 1 cm the ratios fall obviously, i.e., the impact of gamma on neutron decreases. With the same offset, the distribution of PSF of gamma is smaller than that of neutron, and the distribution of PSF of the two particles’ superposition is between that of gamma and tha
The ratios of good event, energy deposition of gamma and neutron with different offsets are obtained by the model of pinhole imaging based on Geant4 system. The effect on the point spread function(PSF) of neutron pinhole imaging caused by the high gamma ray background is simulated and analyzed. The results show that with the offsets less than 1 cm the ratios of good event, peak value of energy deposition, total energy deposition of gamma and neutron are 0.40~0.42, 0.63~0.65, 0.46~0.49, respectively; with the offsets greater than 1 cm the ratios fall obviously, i.e., the impact of gamma on neutron decreases. With the same offset, the distribution of PSF of gamma is smaller than that of neutron, and the distribution of PSF of the two particles’ superposition is between that of gamma and tha
2008,
20.
Abstract:
A ferroelectric electron gun was designed and fabricated. The simulation and preliminary experimental results of the gun are reported. The gun uses a planar Ba0.67Sr0.33TiO3 (BST67/33)cathode in a Pierce geometry. The gun voltage can reach 80 kV with the pulse width of 80 ns. The designed perveance of the gun is 0.15×10-6 A·V-3/2. In the experiment, the gun voltage gradually increases from 30 kV to 56 kV, and the emission current increases from 0.7 A to 2.5 A. The perveance of the gun is measured as 0.2×10-6 A·V-3/2, mearly the same as the designed value.
A ferroelectric electron gun was designed and fabricated. The simulation and preliminary experimental results of the gun are reported. The gun uses a planar Ba0.67Sr0.33TiO3 (BST67/33)cathode in a Pierce geometry. The gun voltage can reach 80 kV with the pulse width of 80 ns. The designed perveance of the gun is 0.15×10-6 A·V-3/2. In the experiment, the gun voltage gradually increases from 30 kV to 56 kV, and the emission current increases from 0.7 A to 2.5 A. The perveance of the gun is measured as 0.2×10-6 A·V-3/2, mearly the same as the designed value.
2008,
20.
Abstract:
The design of control system for beam in RIBLL Ⅱ and CSRe has been introduced, including the design of software and hardware. Using technology of Java, COM, Oracle, ARM, DSP and FPGA in control system is to control power devices in real time and control the and control the beam effectively and simultaneously. The control system has been used in RIBLL Ⅱ to control beam, which shows that this system is highly reliable and stable.
The design of control system for beam in RIBLL Ⅱ and CSRe has been introduced, including the design of software and hardware. Using technology of Java, COM, Oracle, ARM, DSP and FPGA in control system is to control power devices in real time and control the and control the beam effectively and simultaneously. The control system has been used in RIBLL Ⅱ to control beam, which shows that this system is highly reliable and stable.
