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RSS2009 Vol. 21, No. 05
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2009,
21.
Abstract:
The so-called beacon difficulty in adaptive optics can be partly overcome by applying laser guide star subsystem. The simplified calculation model for spatial power spectra of main error in a laser guide star adaptive optics system is presented. Compared with the commonly used Monte-Carlo method, this method is more efficient and faster to evaluate the performance of such laser guide star adaptive optics system.
The so-called beacon difficulty in adaptive optics can be partly overcome by applying laser guide star subsystem. The simplified calculation model for spatial power spectra of main error in a laser guide star adaptive optics system is presented. Compared with the commonly used Monte-Carlo method, this method is more efficient and faster to evaluate the performance of such laser guide star adaptive optics system.
2009,
21.
Abstract:
A lens and a paraboloid nozzle were used to focus pulsed CO2 laser and generate impulse. Effects of single pulse energy on impulse coupling coefficient was studied with a highaccuracy compound pendulum and a light figure system. Extension range of pulse energy from 5 J to 70 J was obtained through adjusting working voltage of the laser and energy attenuation of silicon combinations in the experiment. In addition, schlieren photographs were taken by a nanosecond framed high speed camera at the pulse energy of 24 J. The results indicate that the impulse coupling coefficient kept constant when pulse energy ranged from 4 J to 9 J and from 32 J to 70 J respectively. From 9 J to 32 J, it changed between 6.5 and 21×10-5 N·s·J-1 following a linear increment. The schlieren photographs show tha
A lens and a paraboloid nozzle were used to focus pulsed CO2 laser and generate impulse. Effects of single pulse energy on impulse coupling coefficient was studied with a highaccuracy compound pendulum and a light figure system. Extension range of pulse energy from 5 J to 70 J was obtained through adjusting working voltage of the laser and energy attenuation of silicon combinations in the experiment. In addition, schlieren photographs were taken by a nanosecond framed high speed camera at the pulse energy of 24 J. The results indicate that the impulse coupling coefficient kept constant when pulse energy ranged from 4 J to 9 J and from 32 J to 70 J respectively. From 9 J to 32 J, it changed between 6.5 and 21×10-5 N·s·J-1 following a linear increment. The schlieren photographs show tha
2009,
21.
Abstract:
The convergence rate can be the limit of adaptive optics without a wave-front sensor in real-time applications. An improvement on the convergence rate of the stochastic parallel gradient descent(SPGD) algorithm is discussed by combing modal method with zonal method. Based on the SPGD algorithm, adaptive optics systems are simulated with a 61-element deformable mirror. Results show that the modified SPGD algorithm can converge much faster than that based only on zonal method when the same correction effect is obtained.
The convergence rate can be the limit of adaptive optics without a wave-front sensor in real-time applications. An improvement on the convergence rate of the stochastic parallel gradient descent(SPGD) algorithm is discussed by combing modal method with zonal method. Based on the SPGD algorithm, adaptive optics systems are simulated with a 61-element deformable mirror. Results show that the modified SPGD algorithm can converge much faster than that based only on zonal method when the same correction effect is obtained.
2009,
21.
Abstract:
In order to increase the wear life of 40Cr steel, preset laser cladding techniques were adopted with Fe-based alloy powders which were obtained on the 40Cr steel substrate. Wear tests were carried out with HT-500 wear tester to determine the rule of friction coefficient varying with temperature under dry friction condition. Moreover, the depth and width of wear scars were measured by surface roughness profiler. The micrographs of wear scar on cladding coating were scanned by SEM. The microhardness of both cladding coating and substrate were measured by HV-1000 microhardness instrument. As the tests show, under dry sliding condition, with the increase of temperature and wear time, the wear course became stable. The average friction coefficient reduced,the wear rate rose, the wear resistance
In order to increase the wear life of 40Cr steel, preset laser cladding techniques were adopted with Fe-based alloy powders which were obtained on the 40Cr steel substrate. Wear tests were carried out with HT-500 wear tester to determine the rule of friction coefficient varying with temperature under dry friction condition. Moreover, the depth and width of wear scars were measured by surface roughness profiler. The micrographs of wear scar on cladding coating were scanned by SEM. The microhardness of both cladding coating and substrate were measured by HV-1000 microhardness instrument. As the tests show, under dry sliding condition, with the increase of temperature and wear time, the wear course became stable. The average friction coefficient reduced,the wear rate rose, the wear resistance
2009,
21.
Abstract:
In this paper, the purpose of output pulsed laser with high-power and high beam quality is discussed, and the structure of unsymmetrical plane-concave resonator is analyzed theoretically. We have completed the laser, which could output high-power and high beam quality with single Nd: YAG rod pumped by double Xe-lamp and unsymmetrical plane-concave resonator. When the duty cycle was 9%, the average power of laser was nearly 480 W, beam parameters product was better than 12.7 mm·mrad and efficiency of electricity to light was nearly 4%, which matched the theoretical analysis well. The laser could be transmitted by optic fiber of 300 μm core diameter and its instability was less than ±1%. Processing experiment has proved that it had good cutting quality．
In this paper, the purpose of output pulsed laser with high-power and high beam quality is discussed, and the structure of unsymmetrical plane-concave resonator is analyzed theoretically. We have completed the laser, which could output high-power and high beam quality with single Nd: YAG rod pumped by double Xe-lamp and unsymmetrical plane-concave resonator. When the duty cycle was 9%, the average power of laser was nearly 480 W, beam parameters product was better than 12.7 mm·mrad and efficiency of electricity to light was nearly 4%, which matched the theoretical analysis well. The laser could be transmitted by optic fiber of 300 μm core diameter and its instability was less than ±1%. Processing experiment has proved that it had good cutting quality．
2009,
21.
Abstract:
Eddy-covariance and profile measurements over snow were carried out at the 35 m tower in Hefei from Jan 28, 2008 to Feb 1, 2008. A similarity function was presented for the stable atmospheric stratification, and then refractive index structure parameter for the optical turbulence was estimated using eddy-covariance and bulk methods based on the function. Results show that the atmosphere near snow surface was nearly neutral and stable during most of the time in the experiment; with the presented similarity function, the estimate results using the two methods agree well with the measured one; the refractive index structure parameter over the snow cover ranged from 1.9×10-16 to 1×10-14 m-2/3, and exhibited a clear diurnal dependence like that over lawn, ocean and desert.
Eddy-covariance and profile measurements over snow were carried out at the 35 m tower in Hefei from Jan 28, 2008 to Feb 1, 2008. A similarity function was presented for the stable atmospheric stratification, and then refractive index structure parameter for the optical turbulence was estimated using eddy-covariance and bulk methods based on the function. Results show that the atmosphere near snow surface was nearly neutral and stable during most of the time in the experiment; with the presented similarity function, the estimate results using the two methods agree well with the measured one; the refractive index structure parameter over the snow cover ranged from 1.9×10-16 to 1×10-14 m-2/3, and exhibited a clear diurnal dependence like that over lawn, ocean and desert.
2009,
21.
Abstract:
The interrelation between the temperature difference of the deuterium and tritium(DT) outer surface and roughness of the DT layer has been obtained in theory for the indirect drive targets of inertial confinement fusion. Taking the Laser Magajoule(LMJ) as a prototype, the effects of target misalignment from the center of the hohlraum on the axial axis and the nonuniformity of the capsule on the DT layer temperature profiles have been simulated with a CFD code (Fluent). Then, the thickness nonuniformities of the DT layer have been calculated with the theoretical expression. The results show that in order to satisfy the requirement of ignition, the target misalignment must be less than 8.5 μm, and the RMS roughness of the capsule should be controlled in 0.72 μm.
The interrelation between the temperature difference of the deuterium and tritium(DT) outer surface and roughness of the DT layer has been obtained in theory for the indirect drive targets of inertial confinement fusion. Taking the Laser Magajoule(LMJ) as a prototype, the effects of target misalignment from the center of the hohlraum on the axial axis and the nonuniformity of the capsule on the DT layer temperature profiles have been simulated with a CFD code (Fluent). Then, the thickness nonuniformities of the DT layer have been calculated with the theoretical expression. The results show that in order to satisfy the requirement of ignition, the target misalignment must be less than 8.5 μm, and the RMS roughness of the capsule should be controlled in 0.72 μm.
2009,
21.
Abstract:
A triple-orifice droplet generator was designed and developed for the size-controllable continuous fabrication of hollow foam micro-shells. Solutions of an internal water phase, an oil phase (trimethylpropane triacrylate monomer, dibutyl phthalate solvent, and benzoin ethyl ether initiator), and an external water phase were used to prepare micro-shells whose diameters are between 1.5 mm and 4.0 mm successfully. Characterization of the foam shells was carried out using a scanning electron microscope and X-ray radiography. The results show that cell diameters of the shells are not above 1 μm. The refractive index of the polymer framework is around 1.50. Furthurmore, the shells fabricated through the triple-orifice droplet generator have a high survival probability of 93% and exhibit narrow
A triple-orifice droplet generator was designed and developed for the size-controllable continuous fabrication of hollow foam micro-shells. Solutions of an internal water phase, an oil phase (trimethylpropane triacrylate monomer, dibutyl phthalate solvent, and benzoin ethyl ether initiator), and an external water phase were used to prepare micro-shells whose diameters are between 1.5 mm and 4.0 mm successfully. Characterization of the foam shells was carried out using a scanning electron microscope and X-ray radiography. The results show that cell diameters of the shells are not above 1 μm. The refractive index of the polymer framework is around 1.50. Furthurmore, the shells fabricated through the triple-orifice droplet generator have a high survival probability of 93% and exhibit narrow
2009,
21.
Abstract:
An electron optics model of axial symmetric cylinder is adopted, three-dimensional and two-dimensional model are established based on this model. The traces of electron beam are calculated, and image location is also obtained. The influences of the electrode shape, size and load on imaging are analyzed. The result indicates that the focusing electrode is more significant than the other electrodes, and load is the most critical parameter in the electron optics system.
An electron optics model of axial symmetric cylinder is adopted, three-dimensional and two-dimensional model are established based on this model. The traces of electron beam are calculated, and image location is also obtained. The influences of the electrode shape, size and load on imaging are analyzed. The result indicates that the focusing electrode is more significant than the other electrodes, and load is the most critical parameter in the electron optics system.
2009,
21.
Abstract:
The plasma temperature is an important factor in quantitative analysis by laser-induced breakdown spectroscopy(LIBS). The plasmas were generated by a Nd:YAG laser on the surface of sample and detected by an Echelle spectrograph and an Intensified Charge-Coupled Device(ICCD). The spectrum of 300 nm to 450 nm recorded several spectral lines of Ca component such as Ca Ⅱ 315.9 nm, Ca Ⅱ 317.9 nm, Ca Ⅱ 393.4 nm, Ca Ⅱ 396.9 nm, Ca Ⅰ 422.7 nm and so on. It is known that the change of plasma temperature has influence on the line intensity from the equation for quantitative LIBS analysis. It was assumed that the plasmas produced in the experiment were in local thermodynamic equilibrium(LTE). The temperature variations were deduced by the four one-ionized Ca spectral lines and the Boltzmann plot
The plasma temperature is an important factor in quantitative analysis by laser-induced breakdown spectroscopy(LIBS). The plasmas were generated by a Nd:YAG laser on the surface of sample and detected by an Echelle spectrograph and an Intensified Charge-Coupled Device(ICCD). The spectrum of 300 nm to 450 nm recorded several spectral lines of Ca component such as Ca Ⅱ 315.9 nm, Ca Ⅱ 317.9 nm, Ca Ⅱ 393.4 nm, Ca Ⅱ 396.9 nm, Ca Ⅰ 422.7 nm and so on. It is known that the change of plasma temperature has influence on the line intensity from the equation for quantitative LIBS analysis. It was assumed that the plasmas produced in the experiment were in local thermodynamic equilibrium(LTE). The temperature variations were deduced by the four one-ionized Ca spectral lines and the Boltzmann plot
2009,
21.
Abstract:
The result of full-screen sweeping rates of streak camera(SC) is obtained using a nonlinear-least-squares method. The uncertainty of this method is about 0.04%, far below SC’s systematic uncertainty. Full-screen result eliminates nonlinearity and space-distortion of sweeping rates, minimizes the error of SC’s measurement to about 1.5%. The robustness and time-efficiency of this method make full-screen calibration of time-domain and space-domain feasible．
The result of full-screen sweeping rates of streak camera(SC) is obtained using a nonlinear-least-squares method. The uncertainty of this method is about 0.04%, far below SC’s systematic uncertainty. Full-screen result eliminates nonlinearity and space-distortion of sweeping rates, minimizes the error of SC’s measurement to about 1.5%. The robustness and time-efficiency of this method make full-screen calibration of time-domain and space-domain feasible．
2009,
21.
Abstract:
A microchannel plate gated X-ray framing camera(XFC) was used to take pictures of Au plasma radial convergence in hohlraums on Shenguang-Ⅱ laser facility. According to XFC image manipulation by MATLAB and measurement of radiation temperature, hohlraum closure of Au plasma generally will not occur in hohlraums with sizes of 1 000 μm×1 800 μm and 1 200 μm×2 100 μm,on condition that there is no gas and low-Z filling in hohlraum, by laser beams with 351 nm wavelength, 2.4 ns pulse duration and 8×300 J energy on Shenguang-Ⅱ laser facility. While obvious hohlraum closure of Au plasma would occur in the standard hohlraum(800 μm×1 350 μm ) with the laser applied for about 1.5 ns. Additionally, XFC image manipulation unveiled Au plasma radial convergence speed in the three hohlraums, w
A microchannel plate gated X-ray framing camera(XFC) was used to take pictures of Au plasma radial convergence in hohlraums on Shenguang-Ⅱ laser facility. According to XFC image manipulation by MATLAB and measurement of radiation temperature, hohlraum closure of Au plasma generally will not occur in hohlraums with sizes of 1 000 μm×1 800 μm and 1 200 μm×2 100 μm,on condition that there is no gas and low-Z filling in hohlraum, by laser beams with 351 nm wavelength, 2.4 ns pulse duration and 8×300 J energy on Shenguang-Ⅱ laser facility. While obvious hohlraum closure of Au plasma would occur in the standard hohlraum(800 μm×1 350 μm ) with the laser applied for about 1.5 ns. Additionally, XFC image manipulation unveiled Au plasma radial convergence speed in the three hohlraums, w
2009,
21.
Abstract:
The theoretic model of framing camera’s gain attenuation is analyzed. The exponential attenuation curve of the gain along the pulse propagation time is simulated. An experiment to measure the coefficient of gain attenuation based on the gain attenuation theory is designed. Experiment result shows that the gain follows an exponential attenuation rule with a quotient of 0024 9 mm－１,the attenuation coefficient of the pulse is 0.003 56 mm－１. The loss of the pulse propagation along the MCP stripline is the leading reason of gain attenuation. But in the figure of a single stripline, the gain dose not follow the rule of exponential attenuation completely, instead, there is a gain increase at the stripline bottom. That is caused by the reflection of the pulse.The reflectance is about 24.2％.
The theoretic model of framing camera’s gain attenuation is analyzed. The exponential attenuation curve of the gain along the pulse propagation time is simulated. An experiment to measure the coefficient of gain attenuation based on the gain attenuation theory is designed. Experiment result shows that the gain follows an exponential attenuation rule with a quotient of 0024 9 mm－１,the attenuation coefficient of the pulse is 0.003 56 mm－１. The loss of the pulse propagation along the MCP stripline is the leading reason of gain attenuation. But in the figure of a single stripline, the gain dose not follow the rule of exponential attenuation completely, instead, there is a gain increase at the stripline bottom. That is caused by the reflection of the pulse.The reflectance is about 24.2％.
2009,
21.
Abstract:
The data processing procedure for imaging Velocity Interferometer System for Any Reflector(VISAR) has been listed with Fourier transform method. Fringe loss problem in shock wave experiment with imaging VISAR technique has been researched. The fringe loss image from the reference has been processed with Fourier transform method. The fringe image should be clear and uniform, and the one-dimensional Fourier transform method is recommended to reduce the difficulty in filtering the image. The method to confirm the loss point in the fringe loss has been provided. The difference between interference fringes for the opaque and transparent targets is discussed. It is concluded that the fringe from the transparent target should be preprocessed with extension technique before using the normal data
The data processing procedure for imaging Velocity Interferometer System for Any Reflector(VISAR) has been listed with Fourier transform method. Fringe loss problem in shock wave experiment with imaging VISAR technique has been researched. The fringe loss image from the reference has been processed with Fourier transform method. The fringe image should be clear and uniform, and the one-dimensional Fourier transform method is recommended to reduce the difficulty in filtering the image. The method to confirm the loss point in the fringe loss has been provided. The difference between interference fringes for the opaque and transparent targets is discussed. It is concluded that the fringe from the transparent target should be preprocessed with extension technique before using the normal data
2009,
21.
Abstract:
Radiation temperature could be quantified in indirect-drive ICF experiments. This paper introduces a new method for calculating radiation temperature without unfolding. It is a simple method which can provide the real time temperature. Radiation temperature obtained by this method is in accordance with that calculated by traditional methods with an uncertainty of about 7%. The result by measuring shock wave’s velocity has proved this method to be correct. With this method, we have built a new data processing system for 15-channel soft X-ray spectrometer.
Radiation temperature could be quantified in indirect-drive ICF experiments. This paper introduces a new method for calculating radiation temperature without unfolding. It is a simple method which can provide the real time temperature. Radiation temperature obtained by this method is in accordance with that calculated by traditional methods with an uncertainty of about 7%. The result by measuring shock wave’s velocity has proved this method to be correct. With this method, we have built a new data processing system for 15-channel soft X-ray spectrometer.
2009,
21.
Abstract:
The interaction of the plane voltage wave with a pair of 2-D inductor loaded and capacitor loaded transmission line metamaterial slabs is analysed. Under the conjugate matched condition, the voltage distributions inside and outside such paired slabs are derived. In particular, the z-directed wavenumber of the evanescent and propagating voltage wave is discussed. The simulation results show the voltage phase and magnitude at the front face of the pair are the same as that at the back face of the pair, which manifests that each of the spatial Fourier components, including propagating as well as evanescent waves, can completely pass through the conjugate matched slabs, indicating the complete tunneling effect．
The interaction of the plane voltage wave with a pair of 2-D inductor loaded and capacitor loaded transmission line metamaterial slabs is analysed. Under the conjugate matched condition, the voltage distributions inside and outside such paired slabs are derived. In particular, the z-directed wavenumber of the evanescent and propagating voltage wave is discussed. The simulation results show the voltage phase and magnitude at the front face of the pair are the same as that at the back face of the pair, which manifests that each of the spatial Fourier components, including propagating as well as evanescent waves, can completely pass through the conjugate matched slabs, indicating the complete tunneling effect．
2009,
21.
Abstract:
The equations of piecewise linear recursive convolution(PLRC) using finitedifference time-domain(FDTD) method for negativerefractive index materials are presented. The PLRCFDTD method is used to simulate the interaction of electromagnetic wave with negative refractive index materials and calculate the electromagnetic wave reflection coefficients of conductive plate coated with negative refractive index materials. Numerical results indicate that negative refraction index materials cover can greatly reduce the echo energy of targets. The higher the collision frequency and the lower the oscillation frequency, the better the absorption effect. And reflection coefficients are affected by collision frequency, oscillation frequency and distribution form of the material．
The equations of piecewise linear recursive convolution(PLRC) using finitedifference time-domain(FDTD) method for negativerefractive index materials are presented. The PLRCFDTD method is used to simulate the interaction of electromagnetic wave with negative refractive index materials and calculate the electromagnetic wave reflection coefficients of conductive plate coated with negative refractive index materials. Numerical results indicate that negative refraction index materials cover can greatly reduce the echo energy of targets. The higher the collision frequency and the lower the oscillation frequency, the better the absorption effect. And reflection coefficients are affected by collision frequency, oscillation frequency and distribution form of the material．
2009,
21.
Abstract:
Combing Maxwell equations and electron liquid equations, air ionization and breakdown caused by high power microwave(HPM) are analyzed using FDTD method. Comparing with the traditional approximate analysis, this method uses instantaneous electric field instead of equivalent electric field, and updates ionization frequency and collision frequency in each time step, so it can eliminate the error of analysis methods, which ignore the attenuation of electric amplitude during atmosphere breakdown. The change tendency of computed air breakdown threshold with altitude matches well with those in references, while the threshold values are a little larger. Finally, the impact of HPM amplitude, pulse width and altitude on air breakdown threshold are analyzed using this method.
Combing Maxwell equations and electron liquid equations, air ionization and breakdown caused by high power microwave(HPM) are analyzed using FDTD method. Comparing with the traditional approximate analysis, this method uses instantaneous electric field instead of equivalent electric field, and updates ionization frequency and collision frequency in each time step, so it can eliminate the error of analysis methods, which ignore the attenuation of electric amplitude during atmosphere breakdown. The change tendency of computed air breakdown threshold with altitude matches well with those in references, while the threshold values are a little larger. Finally, the impact of HPM amplitude, pulse width and altitude on air breakdown threshold are analyzed using this method.
2009,
21.
Abstract:
Physical and mathematical models of the magnetron injection gun(MIG) were constructed, and a code for MIG’s calculation was developed. A double anode magnetron injection gun for gyro-TWT amplifier working at 35 GHz, 70 kV and 10 A was designed and simulated by the progran, and optimized simulation results were obtained. The influence of the beam voltage and magnet field on electron beam performance was studied. The results show that the boundary element method is an effective approach for analysis of electron optics system in gyro-devices.
Physical and mathematical models of the magnetron injection gun(MIG) were constructed, and a code for MIG’s calculation was developed. A double anode magnetron injection gun for gyro-TWT amplifier working at 35 GHz, 70 kV and 10 A was designed and simulated by the progran, and optimized simulation results were obtained. The influence of the beam voltage and magnet field on electron beam performance was studied. The results show that the boundary element method is an effective approach for analysis of electron optics system in gyro-devices.
2009,
21.
Abstract:
Elliptical helical antennas are more suitable for satellite communications than traditional cylindrical helical antennas, whereas the circular polarization performance deteriorates, which restricts their wide applications. Two methods of improving radiation performance of axial mode helical antennas are combined and applied to elliptical helical antennas and an elliptical helical antenna with a parasitic helix wire and a variable pitch angle is proposed. A 5 coils elliptical helical antenna whose ratio of the short axis to the long axis is 0.65 is simulated by the FEKO software as an instance. It is found that the directivity is improved. Meanwhile, it has good circular polarization performance. The highest power gain is 12.86 dB within the band width of 2.2~4.2 GHz, which is 1.2 dB higher
Elliptical helical antennas are more suitable for satellite communications than traditional cylindrical helical antennas, whereas the circular polarization performance deteriorates, which restricts their wide applications. Two methods of improving radiation performance of axial mode helical antennas are combined and applied to elliptical helical antennas and an elliptical helical antenna with a parasitic helix wire and a variable pitch angle is proposed. A 5 coils elliptical helical antenna whose ratio of the short axis to the long axis is 0.65 is simulated by the FEKO software as an instance. It is found that the directivity is improved. Meanwhile, it has good circular polarization performance. The highest power gain is 12.86 dB within the band width of 2.2~4.2 GHz, which is 1.2 dB higher
2009,
21.
Abstract:
Based on the phase measurement principle of RF signals, the method of S-band relativistic klystron amplifier(RKA) phase measurement was put forward. The experiment of the 800 kW S-band RKA was performed and the phase measurement of S-band RKA was tested. The experimental results show that the phase difference between the input microwave and output microwave declined due to the increase of the beam voltage and decrease of the beam current, the phase difference did not vary with the amplitude of the input microwave and magnetic field．
Based on the phase measurement principle of RF signals, the method of S-band relativistic klystron amplifier(RKA) phase measurement was put forward. The experiment of the 800 kW S-band RKA was performed and the phase measurement of S-band RKA was tested. The experimental results show that the phase difference between the input microwave and output microwave declined due to the increase of the beam voltage and decrease of the beam current, the phase difference did not vary with the amplitude of the input microwave and magnetic field．
2009,
21.
Abstract:
Transient radiation response on CMOS circuits were investigated for different pulse widths. CMOS circuits 4007, 4069 and 6264 were irradiated using “Qiangguang-I” accelerator source. Latchup thresholds of CMOS inverters and upset level of CMOS SRAM with different pulse widths were obtained. The data clearly indicate dose-rate dependency on the pulse widths. The latchup threshold for 4007 and 4069 at 20 ns pulse width is 2 times that at 150 ns. The upset level for 6264 at 20 ns pulse width is 3 times that at 150 ns. The results show that the damage thresholds decrease with the increase of pulse widths．
Transient radiation response on CMOS circuits were investigated for different pulse widths. CMOS circuits 4007, 4069 and 6264 were irradiated using “Qiangguang-I” accelerator source. Latchup thresholds of CMOS inverters and upset level of CMOS SRAM with different pulse widths were obtained. The data clearly indicate dose-rate dependency on the pulse widths. The latchup threshold for 4007 and 4069 at 20 ns pulse width is 2 times that at 150 ns. The upset level for 6264 at 20 ns pulse width is 3 times that at 150 ns. The results show that the damage thresholds decrease with the increase of pulse widths．
2009,
21.
Abstract:
The BEPCⅡ is a double-ring collider with high current(0.91 A) and lots of,which had bunches(93 bunches). In order to inhibit the longitudinal oscillation (0-mode), a 0-mode beam feedback system was used never been used at the storage ring of the BEPCⅡ. It is made up of beam signal collection, filter, down conversion, phase detectior, phase shifter, etc. When the system runs, the longitudinal sideband will be suppressed by more than 10 dB. It shows that the system can inhibits the longitudinal oscillation effectively.
The BEPCⅡ is a double-ring collider with high current(0.91 A) and lots of,which had bunches(93 bunches). In order to inhibit the longitudinal oscillation (0-mode), a 0-mode beam feedback system was used never been used at the storage ring of the BEPCⅡ. It is made up of beam signal collection, filter, down conversion, phase detectior, phase shifter, etc. When the system runs, the longitudinal sideband will be suppressed by more than 10 dB. It shows that the system can inhibits the longitudinal oscillation effectively.
2009,
21.
Abstract:
Based on the detailed investigation in field programmable gate array(FPGA) radiation effects theory, a measurement system for radiation effects on static random access memory(SRAM)-based FPGA was developed. The testing principle of internal memory, function and power current was introduced. The hardware and software implement means of system were presented. Some important parameters for radiation effects on SRAM-based FPGA, such as configuration RAM upset section, block RAM upset section, function fault section and single event latchup section can be gained with this system. The transmission distance of the system can be over 50 m and the maximum number of tested gates can reach one million.
Based on the detailed investigation in field programmable gate array(FPGA) radiation effects theory, a measurement system for radiation effects on static random access memory(SRAM)-based FPGA was developed. The testing principle of internal memory, function and power current was introduced. The hardware and software implement means of system were presented. Some important parameters for radiation effects on SRAM-based FPGA, such as configuration RAM upset section, block RAM upset section, function fault section and single event latchup section can be gained with this system. The transmission distance of the system can be over 50 m and the maximum number of tested gates can reach one million.
2009,
21.
Abstract:
Temporal resolution of a soft X-ray picoseconds framing camera(XPFC) based on gated micro-channel plate (MCP) depends strong-nonlinearly on parameters of gating pulse (width, amplitude) and is much shorter than the gating pulse width, which the so-called “gain narrowing effect”. The temporal resolution and the gain narrowing effect exponent of the XPFC being gated by picoseconds electric pulse are computed and analyzed. So the estimated gain narrowing effect exponent is about 10.0 and the temporal resolution of the framing camera is about 1/3.16 times the width of the gating pulse. The simulations and experiments on the temporal resolution of the XPFC gated respectively by the gating pulse with (250 ps，-1 100 V) and (220 ps，-900 V) are presented. Simulation result of 78.8 ps and experi
Temporal resolution of a soft X-ray picoseconds framing camera(XPFC) based on gated micro-channel plate (MCP) depends strong-nonlinearly on parameters of gating pulse (width, amplitude) and is much shorter than the gating pulse width, which the so-called “gain narrowing effect”. The temporal resolution and the gain narrowing effect exponent of the XPFC being gated by picoseconds electric pulse are computed and analyzed. So the estimated gain narrowing effect exponent is about 10.0 and the temporal resolution of the framing camera is about 1/3.16 times the width of the gating pulse. The simulations and experiments on the temporal resolution of the XPFC gated respectively by the gating pulse with (250 ps，-1 100 V) and (220 ps，-900 V) are presented. Simulation result of 78.8 ps and experi
2009,
21.
Abstract:
Lots of attentions have been paid to spatial distribution, temporal profile, as well as spectrum reshapings in the design of kilojoule petawatt chirped pulse amplification(CPA) systems. The multilayer dielectric thin film reflector fabricated by top-down nano-fabrication processes can be used to realize the spectral reshaping of high power chirped pulses. In the design and fabrication of the reflector, it is necessary to determine the tolerance of ion beam etching appropriately based on the designed reflectivity. Therefore, the analytical expression for the tolerance of ion beam etching has been derived for the multilayer dielectric thin film reflector for spectral reshaping of the chirped pulse laser in the large energy and high power Nd:glass CPA system. The error limitation of ion beam
Lots of attentions have been paid to spatial distribution, temporal profile, as well as spectrum reshapings in the design of kilojoule petawatt chirped pulse amplification(CPA) systems. The multilayer dielectric thin film reflector fabricated by top-down nano-fabrication processes can be used to realize the spectral reshaping of high power chirped pulses. In the design and fabrication of the reflector, it is necessary to determine the tolerance of ion beam etching appropriately based on the designed reflectivity. Therefore, the analytical expression for the tolerance of ion beam etching has been derived for the multilayer dielectric thin film reflector for spectral reshaping of the chirped pulse laser in the large energy and high power Nd:glass CPA system. The error limitation of ion beam
2009,
21.
Abstract:
Numerical calculating on the defect mode in the one-dimensional (1-D) photonic crystal by the optical transmission matrix method was studied. We calculated and analyzed the relationship between refractive index of the defect layer and wavelength of the defect peak and the relationship between defective layer’s thickness and wavelength of the defect peak. It is found that with increasing of the defective layer’s thickness, the wavelength of the defect peak increases linearly. But much more defect peaks would be found when defective layer’s thickness comes to a constant. Additionally, refractive index of the defect layer increases linearly with the increasing wavelength of the defect peak. So, a more effective method of measuring refraction and dielectric constants in microwave field is p
Numerical calculating on the defect mode in the one-dimensional (1-D) photonic crystal by the optical transmission matrix method was studied. We calculated and analyzed the relationship between refractive index of the defect layer and wavelength of the defect peak and the relationship between defective layer’s thickness and wavelength of the defect peak. It is found that with increasing of the defective layer’s thickness, the wavelength of the defect peak increases linearly. But much more defect peaks would be found when defective layer’s thickness comes to a constant. Additionally, refractive index of the defect layer increases linearly with the increasing wavelength of the defect peak. So, a more effective method of measuring refraction and dielectric constants in microwave field is p
2009,
21.
Abstract:
quantum dot SiO2 stabilized SnO2 quantum dot were prepared by sol-gel-hydrothermal process. Then SnO2 quantum dot thin films were obtained by spin-coating with preprocess of well dispersing SnO2 quantum dots in SiO2 sol. The as-prepared SnO2 quantum dots showed tetragonal rutile crystal structure and quantum dot radius of about 4.0 nm. The optical band gap of the thin films was derived from UV-vis transmission spectra, with value of about 3.96 eV. The SnO2 quantum dot thin films showed multi-peak photoluminescence properties at room temperature, mainly excitation emission at 356 nm and defect emission at 388 nm．
quantum dot SiO2 stabilized SnO2 quantum dot were prepared by sol-gel-hydrothermal process. Then SnO2 quantum dot thin films were obtained by spin-coating with preprocess of well dispersing SnO2 quantum dots in SiO2 sol. The as-prepared SnO2 quantum dots showed tetragonal rutile crystal structure and quantum dot radius of about 4.0 nm. The optical band gap of the thin films was derived from UV-vis transmission spectra, with value of about 3.96 eV. The SnO2 quantum dot thin films showed multi-peak photoluminescence properties at room temperature, mainly excitation emission at 356 nm and defect emission at 388 nm．
2009,
21.
Abstract:
Optical properties of N-doped anatase TiO2 films prepared by N ion implantation have been studied. At first, TiO2 films were prepared by RF magnetron sputtering at different substrate temperatures. Then N ion implantations in the films were conducted at fluences of 5×1016, 1×1017 and 5×1017/cm2, respectively. X-ray diffraction(XRD) results show TiO2 is anatase. X-ray photoelectron spectroscopy(XPS) results reveal that N ions interact with TiO2 particles and form TiOxN2-x compound, which leads to the shift of the absorption edge. Simultaneously, the irradiation defects caused by N ion implantation also increase the absorption intensity of TiO2 films in the range of UV-Visible light．
Optical properties of N-doped anatase TiO2 films prepared by N ion implantation have been studied. At first, TiO2 films were prepared by RF magnetron sputtering at different substrate temperatures. Then N ion implantations in the films were conducted at fluences of 5×1016, 1×1017 and 5×1017/cm2, respectively. X-ray diffraction(XRD) results show TiO2 is anatase. X-ray photoelectron spectroscopy(XPS) results reveal that N ions interact with TiO2 particles and form TiOxN2-x compound, which leads to the shift of the absorption edge. Simultaneously, the irradiation defects caused by N ion implantation also increase the absorption intensity of TiO2 films in the range of UV-Visible light．
2009,
21.
Abstract:
According to the mean roughness and semisphere reflectivity of the gold plated polyester film surfaces, and based on the Kirchhoff’s approximation along with the pulse scattering mutual coherence function(MCF), we computed the double frequency scattering section(DFSS) changing with coherence bandwidth frequency difference and scattering angle for different incident angles of a laser (1.06 μm). For δ and Gaussion pulses incidence, scattering power patterns have been obtained with different scattering angle and time by two frequency MCF. The numerical results show that there exists a maximal DFSS in the mirror reflection direction. While the DFSS will decrease rapidly in the diffusing scattering direction with the increase of coherence bandwidth frequency difference. As to vertical inci
According to the mean roughness and semisphere reflectivity of the gold plated polyester film surfaces, and based on the Kirchhoff’s approximation along with the pulse scattering mutual coherence function(MCF), we computed the double frequency scattering section(DFSS) changing with coherence bandwidth frequency difference and scattering angle for different incident angles of a laser (1.06 μm). For δ and Gaussion pulses incidence, scattering power patterns have been obtained with different scattering angle and time by two frequency MCF. The numerical results show that there exists a maximal DFSS in the mirror reflection direction. While the DFSS will decrease rapidly in the diffusing scattering direction with the increase of coherence bandwidth frequency difference. As to vertical inci
2009,
21.
Abstract:
A photoconductive semiconductor switch(PCSS) with a gap of 20 mm was fabricated from semi-insulating GaAs. Triggered by a laser pulse with an incident optical energy of 9.9 mJ and a wavelength of 1 064 nm, photoconductivity tests of the PCSS were performed at different bias voltages. The peak photocurrent through the switch in pressurized SF6 at 0.2 MPa was 1.1 kA at a bias voltage of 50 kV. The analyses suggest that the closure of GaAs PCSS operating in nonlinear mode is not always due to the fact that the energy has been dumped from the charging system by comparing the charge initially stored in the capacitors and the charge through the switch. The on-state resistance of the switch employing extrinsic photoconductivity is calculated to be 2.71 Ω．
A photoconductive semiconductor switch(PCSS) with a gap of 20 mm was fabricated from semi-insulating GaAs. Triggered by a laser pulse with an incident optical energy of 9.9 mJ and a wavelength of 1 064 nm, photoconductivity tests of the PCSS were performed at different bias voltages. The peak photocurrent through the switch in pressurized SF6 at 0.2 MPa was 1.1 kA at a bias voltage of 50 kV. The analyses suggest that the closure of GaAs PCSS operating in nonlinear mode is not always due to the fact that the energy has been dumped from the charging system by comparing the charge initially stored in the capacitors and the charge through the switch. The on-state resistance of the switch employing extrinsic photoconductivity is calculated to be 2.71 Ω．
2009,
21.
Abstract:
Studying optical characteristics in the course of flashover in transformer oil is an effective way to explore breakdown mechanism of transformer oil. Optical signals were irregular pulses of 2~4 ns pulse-width and 30~50 mV amplitude at the pre-flashover stage. When approaching to flashover, the signals were turned into higher frequency one with pulse-widths of 1/2~1/3 ns and maximal amplitudes of about 70 mV, and these optical signals were immediately transformed into only one or two wave peaks having observably different amplitudes at the flashover stage. The optical signals reflected the development of streamer channels and changes of particles in channels in flashover. It is confirmed that photoionization is an important factor of flashover in transformer oil under nanosecond pulses.
Studying optical characteristics in the course of flashover in transformer oil is an effective way to explore breakdown mechanism of transformer oil. Optical signals were irregular pulses of 2~4 ns pulse-width and 30~50 mV amplitude at the pre-flashover stage. When approaching to flashover, the signals were turned into higher frequency one with pulse-widths of 1/2~1/3 ns and maximal amplitudes of about 70 mV, and these optical signals were immediately transformed into only one or two wave peaks having observably different amplitudes at the flashover stage. The optical signals reflected the development of streamer channels and changes of particles in channels in flashover. It is confirmed that photoionization is an important factor of flashover in transformer oil under nanosecond pulses.
Electromagnetic-field model for formation process of magnetic insulation without space-electron loss
2009,
21.
Abstract:
Through analyses on the exchange between the space-electron kinetic energy and interelectrode electromagnetic-field energy, and energy changes of the electromagnetic field on the magnetically insulated transmission line(MITL) cross-section, the quantitative relationship between the line voltage and current is pressented at the start and end during the formation process of the magnetical insulation without electron loss. After the application of this model to the MITL-A of Sandia Z-accelerator, it is found that: the formation process of magnetical insulation leads to the increase of line current and the decrease of line voltage; If the initial line current is infinite, the terminal line voltage and current are almost the same as the initial ones; If the ratio of the terminal space-electron
Through analyses on the exchange between the space-electron kinetic energy and interelectrode electromagnetic-field energy, and energy changes of the electromagnetic field on the magnetically insulated transmission line(MITL) cross-section, the quantitative relationship between the line voltage and current is pressented at the start and end during the formation process of the magnetical insulation without electron loss. After the application of this model to the MITL-A of Sandia Z-accelerator, it is found that: the formation process of magnetical insulation leads to the increase of line current and the decrease of line voltage; If the initial line current is infinite, the terminal line voltage and current are almost the same as the initial ones; If the ratio of the terminal space-electron
2009,
21.
Abstract:
A convoluted strip pulse forming line with zero thickness trace has been designed, which is all-solid and has low characteristic impedance. Through conformal mapping, the calculation method of its characteristic impedance the impedance is derived by converting the convoluted stripline into an asymmetric one. The simulation shows that the impedance will decrease because of trace offset, while the influence of asymmetry could be ignored when the ratio of trace width to the separation between ground planes is large enough. The relationship between asymmetric rate(the distance ratio of trace-upper plane to trace-lower plane) and the impedance is obtained. And the impedance will fluctuate within 5% when the rate less than 3.1, so the influence of asymmetry could be ignored in practical design
A convoluted strip pulse forming line with zero thickness trace has been designed, which is all-solid and has low characteristic impedance. Through conformal mapping, the calculation method of its characteristic impedance the impedance is derived by converting the convoluted stripline into an asymmetric one. The simulation shows that the impedance will decrease because of trace offset, while the influence of asymmetry could be ignored when the ratio of trace width to the separation between ground planes is large enough. The relationship between asymmetric rate(the distance ratio of trace-upper plane to trace-lower plane) and the impedance is obtained. And the impedance will fluctuate within 5% when the rate less than 3.1, so the influence of asymmetry could be ignored in practical design
