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RSS2011 Vol. 23, No. 01
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2011,
23.
Abstract:
The jet cooling technology was introduced and used in the cooling of high power laser mirror, then the water jet cooled mirror was designed. Computational fluid dynamics method was adopted to simulate the jet in a hole by the fluid analysis module FLOTRAN of the finite element analysis software ANSYS, then the influence on the capability of heat transfer of the parameters of the hole was discussed and optimization of the parameters was achieved. The results show that great capability of heat transfer can be achieved by using the jet cooling technology, with simple structure and good controllability, and the heat transfer coefficient can be higher than 100 kW/(m2·K).
The jet cooling technology was introduced and used in the cooling of high power laser mirror, then the water jet cooled mirror was designed. Computational fluid dynamics method was adopted to simulate the jet in a hole by the fluid analysis module FLOTRAN of the finite element analysis software ANSYS, then the influence on the capability of heat transfer of the parameters of the hole was discussed and optimization of the parameters was achieved. The results show that great capability of heat transfer can be achieved by using the jet cooling technology, with simple structure and good controllability, and the heat transfer coefficient can be higher than 100 kW/(m2·K).
2011,
23.
Abstract:
A TEA CO2 laser was employed to ablate atomized droplets for laser propulsion. Parabolic and conic nozzles were chosen for study. Total impulse was derived from the piezoelectric sensor data. Experimental results indicated that specific impulse and internal efficiency were increased to 102 s and 26.1% respectively. For short nozzles, propulsive characteristics increased as focusing site was moved nearer to the top of nozzles. Propulsive characteristics of parabolic nozzles were better than that of conical nozzles.
A TEA CO2 laser was employed to ablate atomized droplets for laser propulsion. Parabolic and conic nozzles were chosen for study. Total impulse was derived from the piezoelectric sensor data. Experimental results indicated that specific impulse and internal efficiency were increased to 102 s and 26.1% respectively. For short nozzles, propulsive characteristics increased as focusing site was moved nearer to the top of nozzles. Propulsive characteristics of parabolic nozzles were better than that of conical nozzles.
2011,
23.
Abstract:
A method of using the air-hole collapsed technology of photonic crystal fiber(PCF) to make surface plasmon resonance (SPR) sensors has been proposed. The air-hole completely collapsed PCF-SPR sensor model has been established and simulated. All-fibered wavelength-detection PCF-SPR sensors were constructed, and a supercontinuum source was used to do the correlated experiments. When air is the ambient medium to be tested, the measured resonance wavelength is 465 nm, which accords with the simulation.
A method of using the air-hole collapsed technology of photonic crystal fiber(PCF) to make surface plasmon resonance (SPR) sensors has been proposed. The air-hole completely collapsed PCF-SPR sensor model has been established and simulated. All-fibered wavelength-detection PCF-SPR sensors were constructed, and a supercontinuum source was used to do the correlated experiments. When air is the ambient medium to be tested, the measured resonance wavelength is 465 nm, which accords with the simulation.
2011,
23.
Abstract:
The 7050 aluminum alloy was processed by laser shock processing (LSP) with high energy repetition rate Nd:glass laser. With unchanged pump power, pressure waveform was measured by polyvinylidene fluoride (PVDF) and the oscilloscope, the surface residual stress of 7050 aluminum alloy was measured by X-ray diffraction, surface roughness was analysed by non-contact optical profiler, the micro-mechanism of the shock pressure, the residual stress and roughness was studied after LSP. Results show that under the condition of unchanged pump power, with the increase of amplified spontaneous emission, the shock pressure and the compressive residual stress of the sample surface gradually decrease, the surface roughness gradually increase.
The 7050 aluminum alloy was processed by laser shock processing (LSP) with high energy repetition rate Nd:glass laser. With unchanged pump power, pressure waveform was measured by polyvinylidene fluoride (PVDF) and the oscilloscope, the surface residual stress of 7050 aluminum alloy was measured by X-ray diffraction, surface roughness was analysed by non-contact optical profiler, the micro-mechanism of the shock pressure, the residual stress and roughness was studied after LSP. Results show that under the condition of unchanged pump power, with the increase of amplified spontaneous emission, the shock pressure and the compressive residual stress of the sample surface gradually decrease, the surface roughness gradually increase.
2011,
23.
Abstract:
The mini-channel cooling system with cylinder disturbed flow is proposed for highpower laser cooling. Using deionized-water as working fluid, heat transfer and pressure drop characters of mini-channel heat radiators with and without disturbed flow are experimentally studied. It is found that the pressure drop per unit length is proportional to Reynolds number, and the disturbed flow has the slight effect on pressure drop. There is an optimal Reynolds number at which the difference of transfer performance between these two kinds of radiators are largest. General empirical formulas are proposed to evaluate heat transfer performance of mini-channel radiators with consideration of Nusselt number as functions of Reynolds number in the mini-channels with and without disturbed flow. The thermal
The mini-channel cooling system with cylinder disturbed flow is proposed for highpower laser cooling. Using deionized-water as working fluid, heat transfer and pressure drop characters of mini-channel heat radiators with and without disturbed flow are experimentally studied. It is found that the pressure drop per unit length is proportional to Reynolds number, and the disturbed flow has the slight effect on pressure drop. There is an optimal Reynolds number at which the difference of transfer performance between these two kinds of radiators are largest. General empirical formulas are proposed to evaluate heat transfer performance of mini-channel radiators with consideration of Nusselt number as functions of Reynolds number in the mini-channels with and without disturbed flow. The thermal
2011,
23.
Abstract:
An all-fiber high-efficiency supercontinuum source based on photonic crystal fiber with low nonlinear coefficient was demonstrated. The pulse train with 5 ps duration, 20 MHz repetition rate, and 50 mW average power output from a mode locked fiber laser was amplified by a 15 μm-diameter large mode fiber amplifier. The output fiber of the amplifier was mode-matched to the photonic crystal fiber using two pieces of short fibers with narrower mode diameter. By pumping the 20 m long low nonlinear coefficient phontonic crystal fiber, a supercontinuum with wavelength extension over 650～1 700 nm was obtained. The output power of the generated supercontinuum was 670 mW pumped by 740 mW input amplified pulses, which implies a conversion efficiency over 90%. The supercontinuum generation process w
An all-fiber high-efficiency supercontinuum source based on photonic crystal fiber with low nonlinear coefficient was demonstrated. The pulse train with 5 ps duration, 20 MHz repetition rate, and 50 mW average power output from a mode locked fiber laser was amplified by a 15 μm-diameter large mode fiber amplifier. The output fiber of the amplifier was mode-matched to the photonic crystal fiber using two pieces of short fibers with narrower mode diameter. By pumping the 20 m long low nonlinear coefficient phontonic crystal fiber, a supercontinuum with wavelength extension over 650～1 700 nm was obtained. The output power of the generated supercontinuum was 670 mW pumped by 740 mW input amplified pulses, which implies a conversion efficiency over 90%. The supercontinuum generation process w
2011,
23.
Abstract:
Laser bars with 808 nm wavelength are designed and fabricated based on GaAs/AlGaAs graded-index waveguide separate confinement hetero structure single quantum well chip. The enhancement in output power, electro-optical conversion efficiency, slope efficiency and spectral properties has been observed in the laser bars with ridge tops and recesses, which can limit the injection current into the active region. The restrictions in lateral diffusion of the current are enhanced with the deepening of the recess, thus improving the electro-optical properties of the bars．
Laser bars with 808 nm wavelength are designed and fabricated based on GaAs/AlGaAs graded-index waveguide separate confinement hetero structure single quantum well chip. The enhancement in output power, electro-optical conversion efficiency, slope efficiency and spectral properties has been observed in the laser bars with ridge tops and recesses, which can limit the injection current into the active region. The restrictions in lateral diffusion of the current are enhanced with the deepening of the recess, thus improving the electro-optical properties of the bars．
2011,
23.
Abstract:
Fine structure of the temporal distribution of stacked chirped pulse is discussed with different spectral width, phase and chirp. The peak power of stacked pulse is 1.5 to 3.0 times of narrow band pulse with small variation of spectral width and it is always 3.0 times of narrowband pulse with random phase fluctuation. Theoretical nonlinear propagation model of stack pulse is established. Numerical simulation shows that stacked chirped pulse has larger small scale modulation gain than narrow band pulse with the same energy. It is indicated that nonlinear optical damage may occur when we use stacked chirped pulse in high power laser systems.
Fine structure of the temporal distribution of stacked chirped pulse is discussed with different spectral width, phase and chirp. The peak power of stacked pulse is 1.5 to 3.0 times of narrow band pulse with small variation of spectral width and it is always 3.0 times of narrowband pulse with random phase fluctuation. Theoretical nonlinear propagation model of stack pulse is established. Numerical simulation shows that stacked chirped pulse has larger small scale modulation gain than narrow band pulse with the same energy. It is indicated that nonlinear optical damage may occur when we use stacked chirped pulse in high power laser systems.
2011,
23.
Abstract:
For the navigation accuracy of strapdown inertial navigation system (SINS) degrades with time, a scheme of vehicle integrated navigation based on laser Doppler velocimeter (LDV) combined with SINS is proposed. Through establishing the state and measurement equations, practical Kalman filter for the integrated system is designed and system simulations are then carried out. It can be concluded that the SINS/LDV integration system can reduce the accumulated error of SINS effectively so that self-contained navigation of high accuracy could be realized. The position accuracy and velocity accuracy are increased by 2 orders and 1 order of magnitude with the SINS/LDV system, respectively, when the velocity measurement accuracy of LDV is 0.1%.
For the navigation accuracy of strapdown inertial navigation system (SINS) degrades with time, a scheme of vehicle integrated navigation based on laser Doppler velocimeter (LDV) combined with SINS is proposed. Through establishing the state and measurement equations, practical Kalman filter for the integrated system is designed and system simulations are then carried out. It can be concluded that the SINS/LDV integration system can reduce the accumulated error of SINS effectively so that self-contained navigation of high accuracy could be realized. The position accuracy and velocity accuracy are increased by 2 orders and 1 order of magnitude with the SINS/LDV system, respectively, when the velocity measurement accuracy of LDV is 0.1%.
2011,
23.
Abstract:
The design of fused silica transmission blazed grating based on modal method is presented under Littrow mounting. A -1st transmitted order blazed grating is designed at the wavelength of 1.06 μm. The first two modes (i.e. mode 0 and mode 1) propagate through the grating with different effective indices and couple out at the grating-substrate interface. And a high diffraction efficiency of -1st transmitted order can be achieved if the first two modes have a phase difference of odd multiple of π. The diffraction performance of the blazed grating is analyzed by the rigorous coupled-wave analysis theory. The design of blazed grating based on modal method matches the analysis perfectly.
The design of fused silica transmission blazed grating based on modal method is presented under Littrow mounting. A -1st transmitted order blazed grating is designed at the wavelength of 1.06 μm. The first two modes (i.e. mode 0 and mode 1) propagate through the grating with different effective indices and couple out at the grating-substrate interface. And a high diffraction efficiency of -1st transmitted order can be achieved if the first two modes have a phase difference of odd multiple of π. The diffraction performance of the blazed grating is analyzed by the rigorous coupled-wave analysis theory. The design of blazed grating based on modal method matches the analysis perfectly.
2011,
23.
Abstract:
The closed-form expressions for the mean-squared beam width and the angular spread of cosh-Gaussian (ChG) array beams propagating through atmospheric turbulence are derived by the integral transform technique. The condition in which ChG array beams have the same directionality as single Gaussian beam is given. It is shown that the angular spread of ChG array beams for coherent combination is smaller than that for incoherent combination, while the latter is less sensitive to turbulence. For coherent combination, the angular spread oscillates when the decentered parameter, waist width and relative separation distance of beams vary. And the oscillatory behavior becomes weaker in turbulence. For incoherent combination, the angular spread is independent of the relative separation distance of be
The closed-form expressions for the mean-squared beam width and the angular spread of cosh-Gaussian (ChG) array beams propagating through atmospheric turbulence are derived by the integral transform technique. The condition in which ChG array beams have the same directionality as single Gaussian beam is given. It is shown that the angular spread of ChG array beams for coherent combination is smaller than that for incoherent combination, while the latter is less sensitive to turbulence. For coherent combination, the angular spread oscillates when the decentered parameter, waist width and relative separation distance of beams vary. And the oscillatory behavior becomes weaker in turbulence. For incoherent combination, the angular spread is independent of the relative separation distance of be
2011,
23.
Abstract:
Based on the extended Huygens-Fresnel principle and the definition of second-order moments of the Wigner distribution function, the propagation formula for the M2-factor of Hermite-Gaussian(H-G) beams propagating in turbulent atmosphere has been derived. Taking into account the Tatarskii spectrum, major factors affecting the M2-factor of H-G beams have been discussed. The results show that the M2-factor in turbulence depends mainly on the beam order, the waist size and wavelength of the beams, the structure constant of refractive-index fluctuations of turbulence and the propagation distance. The M2-factor of H-G beams in turbulent atmosphere increases obviously as the beam order, the structure constant of refractive-index fluctuations of turbulen
Based on the extended Huygens-Fresnel principle and the definition of second-order moments of the Wigner distribution function, the propagation formula for the M2-factor of Hermite-Gaussian(H-G) beams propagating in turbulent atmosphere has been derived. Taking into account the Tatarskii spectrum, major factors affecting the M2-factor of H-G beams have been discussed. The results show that the M2-factor in turbulence depends mainly on the beam order, the waist size and wavelength of the beams, the structure constant of refractive-index fluctuations of turbulence and the propagation distance. The M2-factor of H-G beams in turbulent atmosphere increases obviously as the beam order, the structure constant of refractive-index fluctuations of turbulen
2011,
23.
Abstract:
Some efforts have been made on developing an optical streak image tube: creating a unique electro-optics configuration of streak image tube with large sweep range and high temporal resolution, designing a proper travelling-wave deflection system to improve the deflecting image quality at large deflection angle, and combining the post-acceleration and external image intensifying technique to solve the limitation on detection sensitivity in large streaking area. Preliminary experiments show that the image tube’s temporal resolution is 5 ps within 5 ns sweep range, i.e. the ratio of temporal resolution to time range reaches 1/1 000.
Some efforts have been made on developing an optical streak image tube: creating a unique electro-optics configuration of streak image tube with large sweep range and high temporal resolution, designing a proper travelling-wave deflection system to improve the deflecting image quality at large deflection angle, and combining the post-acceleration and external image intensifying technique to solve the limitation on detection sensitivity in large streaking area. Preliminary experiments show that the image tube’s temporal resolution is 5 ps within 5 ns sweep range, i.e. the ratio of temporal resolution to time range reaches 1/1 000.
2011,
23.
Abstract:
A copper micro-channel phase-change heat sink has been developed for cooling high power continual laser diode based on coupling of boiling-cavitation in micro-channel. Its exterior size was 20 mm×12 mm×1.6 mm. The length of channel was estimated through 2D numerical calculation, and the width, depth and separation were determined according to processing conditions. The electron-optic efficiency, output wavelength and the relation between input current and output power were measured experimentally when LD output power changes from 0 to 100 W. The cooling refrigerant was R134a. The thermal resistance of heat sink was measured as 0.3 ℃/W, when the magnetic drive gear pump operated at 50 r/s motor speed.
A copper micro-channel phase-change heat sink has been developed for cooling high power continual laser diode based on coupling of boiling-cavitation in micro-channel. Its exterior size was 20 mm×12 mm×1.6 mm. The length of channel was estimated through 2D numerical calculation, and the width, depth and separation were determined according to processing conditions. The electron-optic efficiency, output wavelength and the relation between input current and output power were measured experimentally when LD output power changes from 0 to 100 W. The cooling refrigerant was R134a. The thermal resistance of heat sink was measured as 0.3 ℃/W, when the magnetic drive gear pump operated at 50 r/s motor speed.
2011,
23.
Abstract:
This paper proposes an infrared diffusion imaging and multi-point calibration method to measure the far-field beam quality parameters of the high-power laser. The high-energy pulse laser spot’s images are obtained with an imaging detector by laying the diffuse reflection target in far field. The pulse-width and peak power of the laser are measured using an energy detector which is put behind a hole at the center of the target plane. According to the energy calibration of the laser spot’s images, the energy and power distribution, the total energy and the corresponding beam quality parameters of the far field high-energy pulse laser beam are attained. This method has been applied to measuring the parameters of a high-energy TEA CO2 laser. The measured cross-section radius of fa
This paper proposes an infrared diffusion imaging and multi-point calibration method to measure the far-field beam quality parameters of the high-power laser. The high-energy pulse laser spot’s images are obtained with an imaging detector by laying the diffuse reflection target in far field. The pulse-width and peak power of the laser are measured using an energy detector which is put behind a hole at the center of the target plane. According to the energy calibration of the laser spot’s images, the energy and power distribution, the total energy and the corresponding beam quality parameters of the far field high-energy pulse laser beam are attained. This method has been applied to measuring the parameters of a high-energy TEA CO2 laser. The measured cross-section radius of fa
2011,
23.
Abstract:
Based on the fact that the motion (i.e. azimuth, elevation and their derivative velocities), amplitude and size of infrared target could be acquired simultaneously, a multi-feature association based approach is presented to track infrared dim moving target. The characters of the infrared imaging tracking system are first analyzed, and the motion, amplitude and size of target of interest are modeled as second order stationary random signals. The probability of motion, amplitude and size of measurement originated as target of interest is then estimated by Gaussian distribution. Subsequently, the combined probability of motion, amplitude and size is derived by probabilistic data association (PDA), and their weight coefficients are estimated adaptively according to their fluctuations. Finally,
Based on the fact that the motion (i.e. azimuth, elevation and their derivative velocities), amplitude and size of infrared target could be acquired simultaneously, a multi-feature association based approach is presented to track infrared dim moving target. The characters of the infrared imaging tracking system are first analyzed, and the motion, amplitude and size of target of interest are modeled as second order stationary random signals. The probability of motion, amplitude and size of measurement originated as target of interest is then estimated by Gaussian distribution. Subsequently, the combined probability of motion, amplitude and size is derived by probabilistic data association (PDA), and their weight coefficients are estimated adaptively according to their fluctuations. Finally,
2011,
23.
Abstract:
1 064 nm antireflection/532 nm high-reflection bichromatic coatings with and without barrier layer were fabricated on the UBK7 substrate using electron beam evaporation technique. The optical property and laser-induced damage threshold(LIDT) of the coatings were investigated, respectively. Compared with the coatings without barrier layer, the 1 064 nm LIDT of the bichromatic coatings with SiO2 barrier layer is 49.6% higher. By analyzing the morphology and depth information of laser-induced damage spots, and the standing wave electric field distribution of the film stacks, the mechanisms of 1 064 nm and 532 nm laser-induced damages of the bichromatic coatings were discussed. The results show that SiO2 barrier layer strengthens the coatings-substrate interface, and ther
1 064 nm antireflection/532 nm high-reflection bichromatic coatings with and without barrier layer were fabricated on the UBK7 substrate using electron beam evaporation technique. The optical property and laser-induced damage threshold(LIDT) of the coatings were investigated, respectively. Compared with the coatings without barrier layer, the 1 064 nm LIDT of the bichromatic coatings with SiO2 barrier layer is 49.6% higher. By analyzing the morphology and depth information of laser-induced damage spots, and the standing wave electric field distribution of the film stacks, the mechanisms of 1 064 nm and 532 nm laser-induced damages of the bichromatic coatings were discussed. The results show that SiO2 barrier layer strengthens the coatings-substrate interface, and ther
2011,
23.
Abstract:
Using copper sulfate as the precursor and hydrochloric acid as the additive, dendrite-like copper crystals（DLCCs）with micrometer size and face-cubic structure were successfully fabricated by electrochemical deposition at room temperature. Effects of experimental parameters, such as concentrations of sulfate acid, copper sulfate, and hydrochloric acid, current density and deposition time, on size and structure of the DLCCs were investigated. It is indicated that the concentration of sulfate acid does not affect the crystal structure markedly. Whereas fractal structure of copper becomes much clearer with the increasing of the copper ion concentration. When the current density is improved from 0.4 to 1.6 A·cm-2/sup>, the deposit translates into open structure with much more dendrite-
Using copper sulfate as the precursor and hydrochloric acid as the additive, dendrite-like copper crystals（DLCCs）with micrometer size and face-cubic structure were successfully fabricated by electrochemical deposition at room temperature. Effects of experimental parameters, such as concentrations of sulfate acid, copper sulfate, and hydrochloric acid, current density and deposition time, on size and structure of the DLCCs were investigated. It is indicated that the concentration of sulfate acid does not affect the crystal structure markedly. Whereas fractal structure of copper becomes much clearer with the increasing of the copper ion concentration. When the current density is improved from 0.4 to 1.6 A·cm-2/sup>, the deposit translates into open structure with much more dendrite-
2011,
23.
Abstract:
In order to understand the effect of defect distribution on damage behaviors of optical films, the damage morpho-logies, damage processes and absorptive features are experimentally investigated for the multi-layer dielectric reflective films and single-layer sol-gel anti-reflective films. The results show that defects can be classified from functional property besides from morphological and optical properties. In other words, the laser resistance capability of different defects can be distinguished with their damage thresholds. The damage thresholds of optical films are very consistent with the density distributions and thermal absorptivities of defects. According to the damage threshold evolutions, the defects can be effectively classified and judged, and the distribution properties of fu
In order to understand the effect of defect distribution on damage behaviors of optical films, the damage morpho-logies, damage processes and absorptive features are experimentally investigated for the multi-layer dielectric reflective films and single-layer sol-gel anti-reflective films. The results show that defects can be classified from functional property besides from morphological and optical properties. In other words, the laser resistance capability of different defects can be distinguished with their damage thresholds. The damage thresholds of optical films are very consistent with the density distributions and thermal absorptivities of defects. According to the damage threshold evolutions, the defects can be effectively classified and judged, and the distribution properties of fu
2011,
23.
Abstract:
A method for controlling the spatial-frequency errors in computer controlled optical surfacing process (CCOS) is brought forward. The mechanism of middle and high spatial-frequency errors in polishing is studied, error factors are assorted, and the wear function of polishing tool, concentration changing function of slurry and system revised function are established. Then the Preston function is modified, and a dwell function algorithm is established based on the discrete last-squares method. The application shows that, the method can reduce residual errors on optical surface, and thus improve the CCOS precision.
A method for controlling the spatial-frequency errors in computer controlled optical surfacing process (CCOS) is brought forward. The mechanism of middle and high spatial-frequency errors in polishing is studied, error factors are assorted, and the wear function of polishing tool, concentration changing function of slurry and system revised function are established. Then the Preston function is modified, and a dwell function algorithm is established based on the discrete last-squares method. The application shows that, the method can reduce residual errors on optical surface, and thus improve the CCOS precision.
2011,
23.
Abstract:
Accelerated protons in laser-plasma interactions are originated from the hydrocarbon contaminant affiliating on the target surface. A novel scheme of double-layer target is proposed to provide a stable and strong proton source. The Double-layer targets were designed and manufactured by sputtering 200 nm thick Au on 2.5 μm thick Mylar films. The measurement of proton beams in laser-plasma interaction was done by magnetic spectrometer and CR-39 solid state nuclear track detectors. The experimental results suggest that the double-layer target can efficiently increase the yield of protons, and may improve the quality of proton beams.
Accelerated protons in laser-plasma interactions are originated from the hydrocarbon contaminant affiliating on the target surface. A novel scheme of double-layer target is proposed to provide a stable and strong proton source. The Double-layer targets were designed and manufactured by sputtering 200 nm thick Au on 2.5 μm thick Mylar films. The measurement of proton beams in laser-plasma interaction was done by magnetic spectrometer and CR-39 solid state nuclear track detectors. The experimental results suggest that the double-layer target can efficiently increase the yield of protons, and may improve the quality of proton beams.
2011,
23.
Abstract:
The surface modification of PS films treated in aqueous hydrochloric solution by ozone aeration has been studied to enhance the interaction between PS and PVA films, and further to increase the survival rate of PS-PVA hollow microspheres. The halfquantitative analysis using FTIR spectra shows that the treatment in aqueous hydrochloric solution introduces carbonyl and hydroxyl groups onto the PS surface, and the contact angle measurements show that the surface of the treated PS film becomes hydrophilic. The strength of interaction between PS and PVA films before and after modification has been investigated by nanoindentation method, which shows an increase of 40% after treatment.
The surface modification of PS films treated in aqueous hydrochloric solution by ozone aeration has been studied to enhance the interaction between PS and PVA films, and further to increase the survival rate of PS-PVA hollow microspheres. The halfquantitative analysis using FTIR spectra shows that the treatment in aqueous hydrochloric solution introduces carbonyl and hydroxyl groups onto the PS surface, and the contact angle measurements show that the surface of the treated PS film becomes hydrophilic. The strength of interaction between PS and PVA films before and after modification has been investigated by nanoindentation method, which shows an increase of 40% after treatment.
2011,
23.
Abstract:
The Shenguang Ⅲ facility general diagnostic instrument manipulator provides a diagnostic platform to insert or retract various diagnostic systems into and out of the target chamber. It provides precision radial positioning and pointing capability, and it can carry diagnostic systems to specific position. It can also ensure the installation, debugging and maintaining of diagnostic system without affecting the vacuum in the target chamber. Installed on the Shenguang Ⅲ prototype facility, it provides the radial positioning accuracy of 36 μm, and the pointing precision of 13 μm in X direction and 8 μm in Y direction. Full path positioning repeatability is 20 μm in radial direction, 30 μm in X direction and 12 μm in Y direction. Laser shot testing with X-ray framing camera indicates tha
The Shenguang Ⅲ facility general diagnostic instrument manipulator provides a diagnostic platform to insert or retract various diagnostic systems into and out of the target chamber. It provides precision radial positioning and pointing capability, and it can carry diagnostic systems to specific position. It can also ensure the installation, debugging and maintaining of diagnostic system without affecting the vacuum in the target chamber. Installed on the Shenguang Ⅲ prototype facility, it provides the radial positioning accuracy of 36 μm, and the pointing precision of 13 μm in X direction and 8 μm in Y direction. Full path positioning repeatability is 20 μm in radial direction, 30 μm in X direction and 12 μm in Y direction. Laser shot testing with X-ray framing camera indicates tha
2011,
23.
Abstract:
Fresnel zone plate has a dominating focus and a series of high-order foci, it will be influenced by advanced diffraction when used as an imaging device. A Gabor zone plate has only one focus, it has much better diffraction properties. However, it is hard to fabricate. The emergence of quasi-random-dot-array binary Gabor zone plates can solve this problem. In this paper, design of quasi-random-dot-array binary Gabor zone plates is introduced, and diffraction properties of Fresnel zone plate and binary Gabor zone plate are simulated by optimized program. Analyzing and comparing the simulation show that the quasi-random-dot-array binary Gabor zone plate could restrain advanced diffraction．
Fresnel zone plate has a dominating focus and a series of high-order foci, it will be influenced by advanced diffraction when used as an imaging device. A Gabor zone plate has only one focus, it has much better diffraction properties. However, it is hard to fabricate. The emergence of quasi-random-dot-array binary Gabor zone plates can solve this problem. In this paper, design of quasi-random-dot-array binary Gabor zone plates is introduced, and diffraction properties of Fresnel zone plate and binary Gabor zone plate are simulated by optimized program. Analyzing and comparing the simulation show that the quasi-random-dot-array binary Gabor zone plate could restrain advanced diffraction．
2011,
23.
Abstract:
Based on the Coulomb’s law and the current continuity equation, this paper solutes the electric field of the charged particles group at a certain point in space, and considers a series of reasonable approximation. The two-dimensional space-charge-limited flow first-level approximating formula in the axial symmetry column conductor is obtained. The result reveals that for a limited plane the computed charge-limited flow by the two-dimensional is bigger than that by the classical one dimension formula.
Based on the Coulomb’s law and the current continuity equation, this paper solutes the electric field of the charged particles group at a certain point in space, and considers a series of reasonable approximation. The two-dimensional space-charge-limited flow first-level approximating formula in the axial symmetry column conductor is obtained. The result reveals that for a limited plane the computed charge-limited flow by the two-dimensional is bigger than that by the classical one dimension formula.
2011,
23.
Abstract:
An X-ray power measuring system composed of slit, scintillator and phototube is used to diagnose the characteristic parameters of soft X-ray generated in the implosion of Al wire array Z-pinch experiments on the S-300 facility at Kurchatov Institute. Wire array loads based on zero-dimension thin shell model are designed for experiments. For single wire array load, the experiment gets an X-ray power of (0.31±0.19) TW, total radiated energy of (16.40±7.45) kJ, and pulse width of (18.41±5.00) ns. For nested wire array load, an X-ray power of (0.37±0.12 ) TW, total radiated energy of (16.93±3.99) kJ, and pulse width of (13.45±3.50) ns are achieved. The experimental results of different wire array loads show that the total energy achieved by nested wire array is 19.4% higher than that of
An X-ray power measuring system composed of slit, scintillator and phototube is used to diagnose the characteristic parameters of soft X-ray generated in the implosion of Al wire array Z-pinch experiments on the S-300 facility at Kurchatov Institute. Wire array loads based on zero-dimension thin shell model are designed for experiments. For single wire array load, the experiment gets an X-ray power of (0.31±0.19) TW, total radiated energy of (16.40±7.45) kJ, and pulse width of (18.41±5.00) ns. For nested wire array load, an X-ray power of (0.37±0.12 ) TW, total radiated energy of (16.93±3.99) kJ, and pulse width of (13.45±3.50) ns are achieved. The experimental results of different wire array loads show that the total energy achieved by nested wire array is 19.4% higher than that of
2011,
23.
Abstract:
This paper focuses on the fabrication and half-life time of the gas-illed polystyrene hohlraum. There are two ways to fabricate the polystyrene hohlraum, i.e. spin coating with polystyrene solution and dip coating with molten polystyrene. Experiments show that many bubbles and orientation crystallization exist in the plastic hohlraum made by polystyrene melt, and the hohlraum can hardly retain gas due to too many cracks in it after the removal of copper mandrels. Plastic hohlraums made by spin coating, 10 to 30 μm in thickness and 5 to 20 nm in surface finish, are sealed with 0.3~0.4 μm thick polyimide films. The halflife time of these hohlraums filled with kropton gas is more than 24 h measured by X-ray fluorescence spectrometry．Holded in a gas container, the gas can keep about 92% o
This paper focuses on the fabrication and half-life time of the gas-illed polystyrene hohlraum. There are two ways to fabricate the polystyrene hohlraum, i.e. spin coating with polystyrene solution and dip coating with molten polystyrene. Experiments show that many bubbles and orientation crystallization exist in the plastic hohlraum made by polystyrene melt, and the hohlraum can hardly retain gas due to too many cracks in it after the removal of copper mandrels. Plastic hohlraums made by spin coating, 10 to 30 μm in thickness and 5 to 20 nm in surface finish, are sealed with 0.3~0.4 μm thick polyimide films. The halflife time of these hohlraums filled with kropton gas is more than 24 h measured by X-ray fluorescence spectrometry．Holded in a gas container, the gas can keep about 92% o
2011,
23.
Abstract:
The quasi-monoenergetic beam of 14.7 MeV D3He-fusion protons generated by laser implosion has very important application in proton radiography. Using the FLUKA Monte Carlo code, this paper simulates the diagnosis of the implosions by protons. The simulation focuses on the effect of proton number on imaging quality, proton radiography of direct-driven implosion and indirect-driven implosion, and proton radiography at different time during implosions. The result indicates that the beam of 14.7 MeV D3He-fusion protons is quasi-monoenergetic and small sized, and can be used in the dynamic radiography of ICF implosions.
The quasi-monoenergetic beam of 14.7 MeV D3He-fusion protons generated by laser implosion has very important application in proton radiography. Using the FLUKA Monte Carlo code, this paper simulates the diagnosis of the implosions by protons. The simulation focuses on the effect of proton number on imaging quality, proton radiography of direct-driven implosion and indirect-driven implosion, and proton radiography at different time during implosions. The result indicates that the beam of 14.7 MeV D3He-fusion protons is quasi-monoenergetic and small sized, and can be used in the dynamic radiography of ICF implosions.
2011,
23.
Abstract:
The wide-aperture input cavities with three coupling structures are addressed, and the field distributions of the cold cavities and beam modulation after the electron beams propagate through the input cavity gaps are analyzed. The results show that the fields with single scallop coupling hole and annular coupling hole in operation mode are more uniform than that with double-scallop coupling hole. For large scale drift tubes, the loaded quality factors of the input cavity with annular coupling hole are lower than those with single scallop coupling hole, and the cavity with annular coupling hole matches well with input waveguides. With the same input microwave power, the beam modulation and the power absorption from driving microwaves in the annular coupling hole input cavity are better than
The wide-aperture input cavities with three coupling structures are addressed, and the field distributions of the cold cavities and beam modulation after the electron beams propagate through the input cavity gaps are analyzed. The results show that the fields with single scallop coupling hole and annular coupling hole in operation mode are more uniform than that with double-scallop coupling hole. For large scale drift tubes, the loaded quality factors of the input cavity with annular coupling hole are lower than those with single scallop coupling hole, and the cavity with annular coupling hole matches well with input waveguides. With the same input microwave power, the beam modulation and the power absorption from driving microwaves in the annular coupling hole input cavity are better than
2011,
23.
Abstract:
A quantitative study was conducted on stress reaction in rat induced by 35 GHz millimeter wave. Long-range correlations analysis of the rat electroencephalogram (EEG) was investigated. The scaling exponents α1 and α2 were calculated by detrended fluctuation analysis (DFA) method. The exponent α1 shows that the high frequency EEG component is characterized by Brownian noise before irradiated by 35 GHz millimeter wave while it has long-range correlations during irradiation. The exponent α2 shows that the low frequency EEG component has long-range correlations before irradiation while it is characterized by Brownian noise during irradiation. Introducing stress parameter k(k=α2/α1), the average change rate of k was used to evaluate the intensity of stress in rat evoked by 35 GHz millimet
A quantitative study was conducted on stress reaction in rat induced by 35 GHz millimeter wave. Long-range correlations analysis of the rat electroencephalogram (EEG) was investigated. The scaling exponents α1 and α2 were calculated by detrended fluctuation analysis (DFA) method. The exponent α1 shows that the high frequency EEG component is characterized by Brownian noise before irradiated by 35 GHz millimeter wave while it has long-range correlations during irradiation. The exponent α2 shows that the low frequency EEG component has long-range correlations before irradiation while it is characterized by Brownian noise during irradiation. Introducing stress parameter k(k=α2/α1), the average change rate of k was used to evaluate the intensity of stress in rat evoked by 35 GHz millimet
2011,
23.
Abstract:
A dual-band coaxial horn feed applied in the field high power microwaves is proposed with theoretical analysis and numerical simulation. It is fed by circular waveguide with horizontal corrugations at 4.15 GHz and by coaxial waveguide at 1.75 GHz. Unwanted higher order modes at low frequency can be limited effectively by reducing the outer radius of the coaxial waveguide, and vertical corrugations located at the coaxial waveguide can improve radiation characteristics at high frequency effectively at the same time. With mode matching theory determining the scatter matrix of the feed, the theoretical results and simulation results agree well with each other. It is shown that the dual-band horn feed is compact with low side lobes and azimuthally symmetrical radiation patterns.
A dual-band coaxial horn feed applied in the field high power microwaves is proposed with theoretical analysis and numerical simulation. It is fed by circular waveguide with horizontal corrugations at 4.15 GHz and by coaxial waveguide at 1.75 GHz. Unwanted higher order modes at low frequency can be limited effectively by reducing the outer radius of the coaxial waveguide, and vertical corrugations located at the coaxial waveguide can improve radiation characteristics at high frequency effectively at the same time. With mode matching theory determining the scatter matrix of the feed, the theoretical results and simulation results agree well with each other. It is shown that the dual-band horn feed is compact with low side lobes and azimuthally symmetrical radiation patterns.
2011,
23.
Abstract:
Based on the magnetized plasma constitutive equation, a modified uniaxial perfectly matched layer (M-UPML) absorbing boundary condition (ABC) for anisotropic dispersion media is proposed. The UPML is extended to intercept anisotropic dispersion media through the equivalent relative permittivity. M-UPML finite-difference time-domain method (FDTD) iteration formulas are deduced. Half-space reflection coefficients of nonmagnetic and magnetized plasmas are computed. The results are in agreement with the analytic solutions, and show that the M-UPML ABC has good absorption effect.
Based on the magnetized plasma constitutive equation, a modified uniaxial perfectly matched layer (M-UPML) absorbing boundary condition (ABC) for anisotropic dispersion media is proposed. The UPML is extended to intercept anisotropic dispersion media through the equivalent relative permittivity. M-UPML finite-difference time-domain method (FDTD) iteration formulas are deduced. Half-space reflection coefficients of nonmagnetic and magnetized plasmas are computed. The results are in agreement with the analytic solutions, and show that the M-UPML ABC has good absorption effect.
2011,
23.
Abstract:
Polymeric Mach-Zehnder rib waveguide is an important component in polymeric integrated electro-optic devices. A new technique is used for computing the optical field distribution of the fundamental and higher order modes for TE modes of a polymeric Mach-Zehnder rib waveguide. The technique is based on the combination of the effective index method and the variational method，and has advantages such as high precision, low calculation complexity and high efficiency, which can provide theoretical reference and optimization method for the fabrication of polymeric electro-optic devices. Important parameters of the waveguide are discussed and their relations with the optical power propagation and loss characteristics are investigated by using the finite difference beam propagation method. The opt
Polymeric Mach-Zehnder rib waveguide is an important component in polymeric integrated electro-optic devices. A new technique is used for computing the optical field distribution of the fundamental and higher order modes for TE modes of a polymeric Mach-Zehnder rib waveguide. The technique is based on the combination of the effective index method and the variational method，and has advantages such as high precision, low calculation complexity and high efficiency, which can provide theoretical reference and optimization method for the fabrication of polymeric electro-optic devices. Important parameters of the waveguide are discussed and their relations with the optical power propagation and loss characteristics are investigated by using the finite difference beam propagation method. The opt
2011,
23.
Abstract:
A rectangular waveguide two-way power combiner with the center frequency of 0.225 THz is designed. The distribution of electric field and the efficiency of the combiner are investigated by numerical calculation and simulation. The numerical calculation shows that the combined peak electric field decreases as the phase difference of the two input waves increases. The position of the combined peak electric field moves away from the input port with the increase of the space between the two input waveguides. The results of simulation are in agreement with those of the numerical calculation. The simulation shows that the efficiency of the combiner is higher than 90% and the bandwidth is 10 GHz, when the phase difference between the two input waves is less than 35°.
A rectangular waveguide two-way power combiner with the center frequency of 0.225 THz is designed. The distribution of electric field and the efficiency of the combiner are investigated by numerical calculation and simulation. The numerical calculation shows that the combined peak electric field decreases as the phase difference of the two input waves increases. The position of the combined peak electric field moves away from the input port with the increase of the space between the two input waveguides. The results of simulation are in agreement with those of the numerical calculation. The simulation shows that the efficiency of the combiner is higher than 90% and the bandwidth is 10 GHz, when the phase difference between the two input waves is less than 35°.
2011,
23.
Abstract:
It is necessary to obtain permittivity and permeability of microwave-absorbing material FeSiAl. Based upon transmissionreflection method, the complex electromagnetic parameters of FeSiAl were measured by dint of VNA (vector network analyzer). The simulations were done with CST Microwave Studio. Experiments and simulations both indicate that the gap between samples and the test fixture influences the parameter results seriously. Consequently several mixed samples of powdered FeSiAl and paraffin were made with different mixing percentages. They maintained stable electromagnetic characteristics in a broad microwave band. The electromagnetic parameters of FeSiAl were extracted from the mixture’s electromagnetic parameters based upon optimal equivalent formulas accurately．
It is necessary to obtain permittivity and permeability of microwave-absorbing material FeSiAl. Based upon transmissionreflection method, the complex electromagnetic parameters of FeSiAl were measured by dint of VNA (vector network analyzer). The simulations were done with CST Microwave Studio. Experiments and simulations both indicate that the gap between samples and the test fixture influences the parameter results seriously. Consequently several mixed samples of powdered FeSiAl and paraffin were made with different mixing percentages. They maintained stable electromagnetic characteristics in a broad microwave band. The electromagnetic parameters of FeSiAl were extracted from the mixture’s electromagnetic parameters based upon optimal equivalent formulas accurately．
2011,
23.
Abstract:
A whole pretuning system was established and automatic measuring of the copper model of a 1.3 GHz 9-cell superconducting cavity was realized based on the commonly used theory of the tuning of multicell cavity’s field flatness. For the bead pull measurement of the field profile, a Labview program was written to acquire data and control the step motor cooperatively. A Java program was written to calculate the frequency correction of each cell by a series of matrix manipulation of the field profile data. Then one of the 9 cells was squeezed or stretched according to the estimated frequency correction. With the procedure repeated for several times, the multicell cavity was tuned to the design frequency and field flatness with good accuracy．
A whole pretuning system was established and automatic measuring of the copper model of a 1.3 GHz 9-cell superconducting cavity was realized based on the commonly used theory of the tuning of multicell cavity’s field flatness. For the bead pull measurement of the field profile, a Labview program was written to acquire data and control the step motor cooperatively. A Java program was written to calculate the frequency correction of each cell by a series of matrix manipulation of the field profile data. Then one of the 9 cells was squeezed or stretched according to the estimated frequency correction. With the procedure repeated for several times, the multicell cavity was tuned to the design frequency and field flatness with good accuracy．
2011,
23.
Abstract:
Synchrotron radiation interferometers, based on Van Citterut-Zernike theorem, are developed to measure the electron transverse beam size and emittance in the Shanghai Synchrotron Radiation Facility (SSRF) storage ring. The major engineering considerations including the optical layout, key devices, signal processing method and software architecture of data acquisition are analyzed. The system commissioning and optimization of operation parameters have been done with beam experiments. The beam experimental results show that measurement accuracy depends significantly on CCD gain and exposure time setting. Random measurement uncertainty is minimized to micron level with CCD setting of 0 dB gain and 200 ms exposure time. The electron transverse beam size of SSRF storage ring is measured precise
Synchrotron radiation interferometers, based on Van Citterut-Zernike theorem, are developed to measure the electron transverse beam size and emittance in the Shanghai Synchrotron Radiation Facility (SSRF) storage ring. The major engineering considerations including the optical layout, key devices, signal processing method and software architecture of data acquisition are analyzed. The system commissioning and optimization of operation parameters have been done with beam experiments. The beam experimental results show that measurement accuracy depends significantly on CCD gain and exposure time setting. Random measurement uncertainty is minimized to micron level with CCD setting of 0 dB gain and 200 ms exposure time. The electron transverse beam size of SSRF storage ring is measured precise
2011,
23.
Abstract:
The control of power supply is the key point in the design of HIRFL-CSR system. Based on ARM+FPGA+AD/DA and state-space equation techniques, the design of digital adjustor applied in the power supply system for HIRFL-CSR in Lanzhou is realized. The digital adjustor can accomplish an adjustment control of fifth order and lower. ARM is used as the core of the control system to deal with the multi-threaded task and the precision of power adjustment control is implemented mainly by FPGA and AD/DA techniques. The embedded gigabit fiber interface can transmit the digital signal from external DSP board and the system uses optoelectronic isolator to inhibit interference signals for 32 bit input/output digital signals. Field test has proved that this digital adjustor can meet HIRFL-CSR’s control p
The control of power supply is the key point in the design of HIRFL-CSR system. Based on ARM+FPGA+AD/DA and state-space equation techniques, the design of digital adjustor applied in the power supply system for HIRFL-CSR in Lanzhou is realized. The digital adjustor can accomplish an adjustment control of fifth order and lower. ARM is used as the core of the control system to deal with the multi-threaded task and the precision of power adjustment control is implemented mainly by FPGA and AD/DA techniques. The embedded gigabit fiber interface can transmit the digital signal from external DSP board and the system uses optoelectronic isolator to inhibit interference signals for 32 bit input/output digital signals. Field test has proved that this digital adjustor can meet HIRFL-CSR’s control p
2011,
23.
Abstract:
The filling pattern is multi-bunch in Hefei Light Source (HLS). The optical shutter can pick single bunch from multi-bunch for streak camera system to measure, and thus largely reduces the power of input light and protects the vulnerable photocathode of streak camera effectively. The principle of the optical shutter system is presented, and a system is designed according to the wavelength and repetition frequency of light pulse, and the dimension and length of bunches in HLS. The characteristics of electro-optic modulator (EOM), high voltage driver and high speed synchronous divider are presented. The alignment and debugging of the system are introduced, and the measurements using oscilloscope and streak camera are presented.
The filling pattern is multi-bunch in Hefei Light Source (HLS). The optical shutter can pick single bunch from multi-bunch for streak camera system to measure, and thus largely reduces the power of input light and protects the vulnerable photocathode of streak camera effectively. The principle of the optical shutter system is presented, and a system is designed according to the wavelength and repetition frequency of light pulse, and the dimension and length of bunches in HLS. The characteristics of electro-optic modulator (EOM), high voltage driver and high speed synchronous divider are presented. The alignment and debugging of the system are introduced, and the measurements using oscilloscope and streak camera are presented.
2011,
23.
Abstract:
The beam halo generation in a high-intensity proton radio frequency quadrupole (RFQ) accelerator is one of the key issues, as the beam halo will probably result in beam loss in the downstream linac. A special beam transport line and the measurement system are to be built to study the beam halo generation in the accelerator driven subcritical system (ADS) RFQ accelerator. The measurement of the beam profile, especially the halo distribution is the core of this study. In this paper, the layout of the detectors in the beam transport line is presented. The mechanical design and simulations of the detectors are also presented, including the thermal simulation and material selection of the scanning wires, the design and R&D study of the driving and control system of the detectors, the design and
The beam halo generation in a high-intensity proton radio frequency quadrupole (RFQ) accelerator is one of the key issues, as the beam halo will probably result in beam loss in the downstream linac. A special beam transport line and the measurement system are to be built to study the beam halo generation in the accelerator driven subcritical system (ADS) RFQ accelerator. The measurement of the beam profile, especially the halo distribution is the core of this study. In this paper, the layout of the detectors in the beam transport line is presented. The mechanical design and simulations of the detectors are also presented, including the thermal simulation and material selection of the scanning wires, the design and R&D study of the driving and control system of the detectors, the design and
2011,
23.
Abstract:
Copper loss on Linac causes non-uniform thermal deformation and frequency shift of the cavities. The traditional thermal design method empirically requires to control the temperature variation of the accelerator tube within 3 ℃, since the actual frequency shift is difficult to obtain. A new approach has been proposed and implemented. It controls resonant frequency dispersion of the cavities directly, instead of temperature variation. A 3D reconstruction technique, which utilizes skinning surface modeling theory, is employed to rebuild the deformed model of cavities from finite element method (FEA) model. The reconstructed models are imported into Microwave Studio to solve the resonant frequencies of all the cavities to realize thermo-structure-electromagnetic field coupling analysis. The
Copper loss on Linac causes non-uniform thermal deformation and frequency shift of the cavities. The traditional thermal design method empirically requires to control the temperature variation of the accelerator tube within 3 ℃, since the actual frequency shift is difficult to obtain. A new approach has been proposed and implemented. It controls resonant frequency dispersion of the cavities directly, instead of temperature variation. A 3D reconstruction technique, which utilizes skinning surface modeling theory, is employed to rebuild the deformed model of cavities from finite element method (FEA) model. The reconstructed models are imported into Microwave Studio to solve the resonant frequencies of all the cavities to realize thermo-structure-electromagnetic field coupling analysis. The
2011,
23.
Abstract:
The working principle of the laser-induced breakdown spectroscopy (LIBS) was interpreted, and how the surface optical properties of metallic materials affects the laser-induced plasma radiation intensity was analyzed. An LIBS experimental system in the air was set up and the laser plasma emission spectrum intensity of carbon coatings with different thickness measured. The results show that the spectral line intensity of the laser-induced plasma increases by 16% to 22% when a bunch of high-energy laser (5 J) acts on the steel sample with a 8 μm thick carbon coating. It proves to be feasible that the laser-induced plasma radiation intensity can be increased by coating a carbon layer on the surface of the steel sample.
The working principle of the laser-induced breakdown spectroscopy (LIBS) was interpreted, and how the surface optical properties of metallic materials affects the laser-induced plasma radiation intensity was analyzed. An LIBS experimental system in the air was set up and the laser plasma emission spectrum intensity of carbon coatings with different thickness measured. The results show that the spectral line intensity of the laser-induced plasma increases by 16% to 22% when a bunch of high-energy laser (5 J) acts on the steel sample with a 8 μm thick carbon coating. It proves to be feasible that the laser-induced plasma radiation intensity can be increased by coating a carbon layer on the surface of the steel sample.
2011,
23.
Abstract:
The neutron energy spectra of Be(d, n) reaction source for deuteron energy of 20 MeV at an angle of 0° was measured using time-of-flight techniques and the n-γ discrimination properties of a BC501A liquid scintillation detector. The energy range of the whole neutron spectra measured in the experiment was 0.7 MeV to 25.0 MeV. The fluence of neutron beam was determined by a stilbene scintillation detector which was normalized to the well-calibrated BC501A liquid scintillation detector. Based on the Be (d, n) reaction neutron source, the neutron response of a thin plastic scintillation detector in the energy range of 0.75 MeV to 15.75 MeV was measured by single particle method. The results obtained from the experiment agree with Monte Carlo simulations considering the relative uncertainty o
The neutron energy spectra of Be(d, n) reaction source for deuteron energy of 20 MeV at an angle of 0° was measured using time-of-flight techniques and the n-γ discrimination properties of a BC501A liquid scintillation detector. The energy range of the whole neutron spectra measured in the experiment was 0.7 MeV to 25.0 MeV. The fluence of neutron beam was determined by a stilbene scintillation detector which was normalized to the well-calibrated BC501A liquid scintillation detector. Based on the Be (d, n) reaction neutron source, the neutron response of a thin plastic scintillation detector in the energy range of 0.75 MeV to 15.75 MeV was measured by single particle method. The results obtained from the experiment agree with Monte Carlo simulations considering the relative uncertainty o
2011,
23.
Abstract:
Colorful nickel is produced by scanning nickel films with femtosecond laser pulses. SEM images show that the surface of the colorful nickel is full of laser-induced periodic surface structures covered with nanostructures, whose period is from 480 nm to 510 nm. UV-Vis-NIR spectrophotometer analyses indicate that the reflectance of the colorful nickel decreases sharply in a wide wavelength range from 200 nm to 2 200 nm. NiO is also found in the samples studied with Raman spectra.
Colorful nickel is produced by scanning nickel films with femtosecond laser pulses. SEM images show that the surface of the colorful nickel is full of laser-induced periodic surface structures covered with nanostructures, whose period is from 480 nm to 510 nm. UV-Vis-NIR spectrophotometer analyses indicate that the reflectance of the colorful nickel decreases sharply in a wide wavelength range from 200 nm to 2 200 nm. NiO is also found in the samples studied with Raman spectra.
2011,
23.
Abstract:
The probability of the electron-positron pair creation in vacuum by a time-dependent solution-like electric field is calculated. It has been found that, in order to have prominent pair production, the electric field intensity should be higher than the Schwinger threshold and the pulse duration should be longer than a threshold. The former condition guarantees that the electron in the negative energy state could gain enough energy to transit into a positive-energy state in Compton time. The latter condition is related to momentum requirement for the transition.
The probability of the electron-positron pair creation in vacuum by a time-dependent solution-like electric field is calculated. It has been found that, in order to have prominent pair production, the electric field intensity should be higher than the Schwinger threshold and the pulse duration should be longer than a threshold. The former condition guarantees that the electron in the negative energy state could gain enough energy to transit into a positive-energy state in Compton time. The latter condition is related to momentum requirement for the transition.
2011,
23.
Abstract:
In order to obtain physical mechanism of plasma generated by hypervelocity impact, the energy distribution of hypervelocity impact of an LY12 aluminum projectile into an LY12 aluminum target was analyzed in all the physical processes, related to energy consumption of melting phase transition, vapor phase transition and plasma formation. Factors influencing vaporization and plasma formation were disclosed in every physical stages during the formation of impact ejecta. In addition, additional heating mechanism and physical mechanism of formation and expansion of plasma plume were included after impacting. The model description of every physical process was also given.
In order to obtain physical mechanism of plasma generated by hypervelocity impact, the energy distribution of hypervelocity impact of an LY12 aluminum projectile into an LY12 aluminum target was analyzed in all the physical processes, related to energy consumption of melting phase transition, vapor phase transition and plasma formation. Factors influencing vaporization and plasma formation were disclosed in every physical stages during the formation of impact ejecta. In addition, additional heating mechanism and physical mechanism of formation and expansion of plasma plume were included after impacting. The model description of every physical process was also given.
2011,
23.
Abstract:
To investigate the novel characteristics of negative refractive index materials(NRIMs), a test device was designed and fabricated based on the Snell law to measure the refractive characteristics of an X-band (8.2~12.4 GHz) NRIM sample consisting of ferrimagnetic materials and wire array. The refractive characteristics of the wedge-shaped paraffin sample and NRIM sample were tested with the device, respectively. The measurements of the paraffin sample demonstrate the validity of the fabricated device. The measurements of the NRIM sample exhibit the material’s negative refraction characteristic, which is then proven by the wave beam shift characteristic of the parallel-plate NRIM with electromagnetic simulations.
To investigate the novel characteristics of negative refractive index materials(NRIMs), a test device was designed and fabricated based on the Snell law to measure the refractive characteristics of an X-band (8.2~12.4 GHz) NRIM sample consisting of ferrimagnetic materials and wire array. The refractive characteristics of the wedge-shaped paraffin sample and NRIM sample were tested with the device, respectively. The measurements of the paraffin sample demonstrate the validity of the fabricated device. The measurements of the NRIM sample exhibit the material’s negative refraction characteristic, which is then proven by the wave beam shift characteristic of the parallel-plate NRIM with electromagnetic simulations.
2011,
23.
Abstract:
The frequency spectrum analysis of 252Cf Neutron source is an extremely important method in nuclear stochastic signal processing. Focused on the special “0” and “1” structure of neutron pulse series, this paper proposes a fast-correlation algorithm to improve the computational rate of the spectrum analysis system. And the multi-core processor technology is employed as well as multi-threaded programming techniques of LabVIEW to construct frequency spectrum analysis system of 252Cf neutron source based on LabVIEW.It not only obtains the auto-correlation and cross correlation results, but also auto-power spectrum, cross-power spectrum and ratio of spectral density. The results show that: analysis tools based on LabVIEW improve the fast auto-correlation and cross corr
The frequency spectrum analysis of 252Cf Neutron source is an extremely important method in nuclear stochastic signal processing. Focused on the special “0” and “1” structure of neutron pulse series, this paper proposes a fast-correlation algorithm to improve the computational rate of the spectrum analysis system. And the multi-core processor technology is employed as well as multi-threaded programming techniques of LabVIEW to construct frequency spectrum analysis system of 252Cf neutron source based on LabVIEW.It not only obtains the auto-correlation and cross correlation results, but also auto-power spectrum, cross-power spectrum and ratio of spectral density. The results show that: analysis tools based on LabVIEW improve the fast auto-correlation and cross corr
2011,
23.
Abstract:
The process of the quenching Ni-Co alloy prepared by melt-spinning technology is simulated by molecular dynamics simulation, and the structure characteristics of Ni-Co alloy are studied at different cooling rates. The simulation shows that, the alloy solidification process is sensitive to the cooling rate, and the formation of binary Ni-Co amorphous structure needs a high cooling rate above 80 K/ps. Add additional elements can reduce the required cooling rate of the materials. The alloy is completely crystalline at the cooling rate of 75 K/ps, and the structural change happens, especially at 375 K.
The process of the quenching Ni-Co alloy prepared by melt-spinning technology is simulated by molecular dynamics simulation, and the structure characteristics of Ni-Co alloy are studied at different cooling rates. The simulation shows that, the alloy solidification process is sensitive to the cooling rate, and the formation of binary Ni-Co amorphous structure needs a high cooling rate above 80 K/ps. Add additional elements can reduce the required cooling rate of the materials. The alloy is completely crystalline at the cooling rate of 75 K/ps, and the structural change happens, especially at 375 K.
2011,
23.
Abstract:
Enhancing frequency is an effective method to enhance the power density of a power supply. In order to protect switching devices in the high-frequency capacitor charging power supply (CCPS), the mechanism and influencing factors of reverse peak voltages were investigated based on the series resonant capacitor-charging power supply. Several methods to inhibit the peak voltages were introduced. Fundamental principles of absorption circuit were analyzed, and circuit parameters were selected and optimized by simulation. Then the feasibility of absorption circuit was verified by the test of a 40 kW/50 kHz capacitor-charging power supply.
Enhancing frequency is an effective method to enhance the power density of a power supply. In order to protect switching devices in the high-frequency capacitor charging power supply (CCPS), the mechanism and influencing factors of reverse peak voltages were investigated based on the series resonant capacitor-charging power supply. Several methods to inhibit the peak voltages were introduced. Fundamental principles of absorption circuit were analyzed, and circuit parameters were selected and optimized by simulation. Then the feasibility of absorption circuit was verified by the test of a 40 kW/50 kHz capacitor-charging power supply.
2011,
23.
Abstract:
The paper studies the performance of the triggered corona stabilized (TCS) rod-panel switch designed. The switch works steadily at trigger mode when it is operated in air at atmospheric pressure. The jitter and breakdown delay can be controlled down four nanoseconds and thirty six nanoseconds, respectively. The breakdown delay can be roughly reduced and the switch stability can be further enhanced through shortening the trigger gap.
The paper studies the performance of the triggered corona stabilized (TCS) rod-panel switch designed. The switch works steadily at trigger mode when it is operated in air at atmospheric pressure. The jitter and breakdown delay can be controlled down four nanoseconds and thirty six nanoseconds, respectively. The breakdown delay can be roughly reduced and the switch stability can be further enhanced through shortening the trigger gap.
2011,
23.
Abstract:
For the serious electromagnetic interference (EMI) problem in fuze arisen from volume constraints in the application of pulsed laser fuze to medium/small caliber conventional ammunition, the paper analyzes the necessity of adopting anti-interference measures internally with the principle of transmitter and receiver modules. Dual shielding which inhibits radiated interference (RI) and multi-filtering technique composed of linear impedance stabilization circuit, buffer network, CM-DM integrated choke, which inhibits conducted interference are proposed by analyzing EMI mechanism of transmitter module and receiver module. Simulations show that steel shield with the thickness of 1.55×10-3 m has good shielding effect on RI. Experiments prove that the peak value of receiver module interference s
For the serious electromagnetic interference (EMI) problem in fuze arisen from volume constraints in the application of pulsed laser fuze to medium/small caliber conventional ammunition, the paper analyzes the necessity of adopting anti-interference measures internally with the principle of transmitter and receiver modules. Dual shielding which inhibits radiated interference (RI) and multi-filtering technique composed of linear impedance stabilization circuit, buffer network, CM-DM integrated choke, which inhibits conducted interference are proposed by analyzing EMI mechanism of transmitter module and receiver module. Simulations show that steel shield with the thickness of 1.55×10-3 m has good shielding effect on RI. Experiments prove that the peak value of receiver module interference s
2011,
23.
Abstract:
In this paper, an equivalent circuit calculation model of the single stage helical magnetic flux compression generators is developed. The inductance and resistance of the generator are formulated based on the assumption of zero-dimensional model. A calculation code is programmed to compute the generator parameters and the change of current, inner voltage, resistivity and temperature during the charging and operating period of the generator. The calculated results prove that the model can provide an accurate prediction for designing magnetic flux compression generators.
In this paper, an equivalent circuit calculation model of the single stage helical magnetic flux compression generators is developed. The inductance and resistance of the generator are formulated based on the assumption of zero-dimensional model. A calculation code is programmed to compute the generator parameters and the change of current, inner voltage, resistivity and temperature during the charging and operating period of the generator. The calculated results prove that the model can provide an accurate prediction for designing magnetic flux compression generators.
2011,
23.
Abstract:
The fractionalturn ratio pulse transformer was theoretically analyzed, including the relationship between rise time and the number of secondary winding turns, area of magnetic core cross section as well as voltagetime product. A 1:43.4 turn ratio pulse transformer was designed and built accordingly. The secondary leakage inductance is 157.3 μH and the stray capacitance is 412 pF. The rise time is 894 ns in low voltage test. High voltage test of the pulse transformer connected with a 420 Ω fictitious load has been performed in oil. An output pulse with a peak voltage of 42.7 kV and a rise time of 917 ns was generated．
The fractionalturn ratio pulse transformer was theoretically analyzed, including the relationship between rise time and the number of secondary winding turns, area of magnetic core cross section as well as voltagetime product. A 1:43.4 turn ratio pulse transformer was designed and built accordingly. The secondary leakage inductance is 157.3 μH and the stray capacitance is 412 pF. The rise time is 894 ns in low voltage test. High voltage test of the pulse transformer connected with a 420 Ω fictitious load has been performed in oil. An output pulse with a peak voltage of 42.7 kV and a rise time of 917 ns was generated．
2011,
23.
Abstract:
A spiral parallel-plates Blumlein line with polypropylene dielectric and film aluminum electrodes was designed. With the gap switches connected, its discharging characteristics were studied. Simulation and experimental results show that the increase in switch inductance slows down the rising of pulses and introduces reflections. The energy loss caused by film electrode resistance lowers the pulse top. The existence of distributed capacitance coupling leads to pre-pulsing in output waveform voltage while the voltage-sharing electrodes have no effects on discharging characteristics.
A spiral parallel-plates Blumlein line with polypropylene dielectric and film aluminum electrodes was designed. With the gap switches connected, its discharging characteristics were studied. Simulation and experimental results show that the increase in switch inductance slows down the rising of pulses and introduces reflections. The energy loss caused by film electrode resistance lowers the pulse top. The existence of distributed capacitance coupling leads to pre-pulsing in output waveform voltage while the voltage-sharing electrodes have no effects on discharging characteristics.
2011,
23.
Abstract:
A cell module of linear transformer driver (LTD), based on Blumlein pulse forming network (PFN), is designed. Two Blumlein PFNs with 20 Ω resistance are symmetrically connected with the LTD’s primary coil. The connection reduces the design difficulty of PFN and improves the output pulse quality. High voltage pulses are derived from a 10 Ω matching load connected with the LTD’s secondary coil. The output pulse of the LTD module is about 200 ns in duration with a rise time of about 55 ns and a flat top of about 100 ns．
A cell module of linear transformer driver (LTD), based on Blumlein pulse forming network (PFN), is designed. Two Blumlein PFNs with 20 Ω resistance are symmetrically connected with the LTD’s primary coil. The connection reduces the design difficulty of PFN and improves the output pulse quality. High voltage pulses are derived from a 10 Ω matching load connected with the LTD’s secondary coil. The output pulse of the LTD module is about 200 ns in duration with a rise time of about 55 ns and a flat top of about 100 ns．
2011,
23.
Abstract:
The effects of surface roughness, field enhancement factor, current and gas pressure on self-breakdown voltage of a stackable multigap switch used for fast linear transformer driver are investigated. The mean self-breakdown voltage has no remarkable change and the dispersancy of self-breakdown voltage is under 1.5% when the surface roughness is 0.4 μm to 0.8 μm. The electrode erosion is symmetrical and the dispersancy of self-breakdown voltage is under 2.0% when the field enhancement factor is 1.20 and 1.30. The dispersancy of self-breakdown voltage increase almost two times as the current is changed from 1.1 kA to 30.0 kA. The dispersancy of selfbreakdown voltage increases from 1.5% to 3.6% when the gas pressure is changed from 0.04 MPa to 0.30 MPa. Some methods of reducing the disp
The effects of surface roughness, field enhancement factor, current and gas pressure on self-breakdown voltage of a stackable multigap switch used for fast linear transformer driver are investigated. The mean self-breakdown voltage has no remarkable change and the dispersancy of self-breakdown voltage is under 1.5% when the surface roughness is 0.4 μm to 0.8 μm. The electrode erosion is symmetrical and the dispersancy of self-breakdown voltage is under 2.0% when the field enhancement factor is 1.20 and 1.30. The dispersancy of self-breakdown voltage increase almost two times as the current is changed from 1.1 kA to 30.0 kA. The dispersancy of selfbreakdown voltage increases from 1.5% to 3.6% when the gas pressure is changed from 0.04 MPa to 0.30 MPa. Some methods of reducing the disp
2011,
23.
Abstract:
A new reliability estimation algorithm for metallized film pulse capacitor was brought forward based on step-down stress accelerated degradation testing (SDSADT) method. The SDSADT was expounded, and the key procedure in the reliability estimation, i.e. testing data conversion, was fully explained. Then reliability assessment arithmetics based on pseudo failure lifetime and random degradation path were proposed. A numerical example was given to illustrate the algorithm. The results show that, at the same estimation precision, this algorithm can have a testing time 45% shorter than that based on constant sdtress accelerated degradation method.
A new reliability estimation algorithm for metallized film pulse capacitor was brought forward based on step-down stress accelerated degradation testing (SDSADT) method. The SDSADT was expounded, and the key procedure in the reliability estimation, i.e. testing data conversion, was fully explained. Then reliability assessment arithmetics based on pseudo failure lifetime and random degradation path were proposed. A numerical example was given to illustrate the algorithm. The results show that, at the same estimation precision, this algorithm can have a testing time 45% shorter than that based on constant sdtress accelerated degradation method.
2011,
23.
Abstract:
The fractionalturn ratio pulse transformer was theoretically analyzed, including the relationship between rise time and the number of secondary winding turns, area of magnetic core cross section as well as voltagetime product. A 1:43.4 turn ratio pulse transformer was designed and built accordingly. The secondary leakage inductance is 157.3 μH and the stray capacitance is 412 pF. The rise time is 894 ns in low voltage test. High voltage test of the pulse transformer connected with a 420 Ω fictitious load has been performed in oil. An output pulse with a peak voltage of 42.7 kV and a rise time of 917 ns was generated．
The fractionalturn ratio pulse transformer was theoretically analyzed, including the relationship between rise time and the number of secondary winding turns, area of magnetic core cross section as well as voltagetime product. A 1:43.4 turn ratio pulse transformer was designed and built accordingly. The secondary leakage inductance is 157.3 μH and the stray capacitance is 412 pF. The rise time is 894 ns in low voltage test. High voltage test of the pulse transformer connected with a 420 Ω fictitious load has been performed in oil. An output pulse with a peak voltage of 42.7 kV and a rise time of 917 ns was generated．
2011,
23.
Abstract:
With Fourier optics, the general expression of far-field intensity of coherently combined beam has been derived, which is affected by single beams phase and amplitude fluctuation due to jitters in the system. The analysis using one-dimensional laser array shows that, the intensity peak becomes sharper and the energy centers in a smaller angle as the number of combined beams increases. The maximum intensity of far field reduces due to the jitters and the background appears, deteriorating the symmetry and quality of far field. Therefore, the stochastic fluctuation of phase should be controlled within 3/8 for single light source of the laser array; the more the beams are combined, the less the influence of the system jitters on far field characteristics is.
With Fourier optics, the general expression of far-field intensity of coherently combined beam has been derived, which is affected by single beams phase and amplitude fluctuation due to jitters in the system. The analysis using one-dimensional laser array shows that, the intensity peak becomes sharper and the energy centers in a smaller angle as the number of combined beams increases. The maximum intensity of far field reduces due to the jitters and the background appears, deteriorating the symmetry and quality of far field. Therefore, the stochastic fluctuation of phase should be controlled within 3/8 for single light source of the laser array; the more the beams are combined, the less the influence of the system jitters on far field characteristics is.
2011,
23.
Abstract:
The mode field distributions at different wavelengths in the first bandgap of all-solid photonic bandgap fibers were numerically studied by multipole method. The corresponding 2D distributions of the normalized intensity were obtained by the same method. The mode field distributions in x and y directions were shown as the two directions were representative in the fiber with six-fold rotational symmetry. In the long-wavelength regime the mode field radii in the two directions are not equal and both decrease as the wavelength increases, which is different from the change in total internal reflection fibers.
The mode field distributions at different wavelengths in the first bandgap of all-solid photonic bandgap fibers were numerically studied by multipole method. The corresponding 2D distributions of the normalized intensity were obtained by the same method. The mode field distributions in x and y directions were shown as the two directions were representative in the fiber with six-fold rotational symmetry. In the long-wavelength regime the mode field radii in the two directions are not equal and both decrease as the wavelength increases, which is different from the change in total internal reflection fibers.
