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RSS2011 Vol. 23, No. 07
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2011,
23.
Abstract:
The recent development of neutron generation and diagnostics of fast Z-pinch are reviewed. The principle and configuration of fusion and fission hybrid reactor are briefly introduced. Current and magnetic impulse modeling and the debris shield design are examined for the interface between Z-pinch driver and hybrid reactor. The conclusion of this work is that the interface of post hole convolute and extended coaxial magnetically insulated transmission line is feasible and easily operated at primary test stand (PTS).
The recent development of neutron generation and diagnostics of fast Z-pinch are reviewed. The principle and configuration of fusion and fission hybrid reactor are briefly introduced. Current and magnetic impulse modeling and the debris shield design are examined for the interface between Z-pinch driver and hybrid reactor. The conclusion of this work is that the interface of post hole convolute and extended coaxial magnetically insulated transmission line is feasible and easily operated at primary test stand (PTS).
2011,
23.
Abstract:
One of the primary development orientations of solid state lasers is to realize the output with “3 highs” which is high average power, high beam quality and high efficiency. By combining the related research works and progress of solid state laser, the relationship of beam quality and output power for solid state laser is dissertated, and the fundamental scientific question that the beam quality nonlinearly decreases with the power increase is suggested. Some important techniques to solve the problems are reviewed and the possible and effective approaches to obtain the “3 highs” solid state laser are probed．
One of the primary development orientations of solid state lasers is to realize the output with “3 highs” which is high average power, high beam quality and high efficiency. By combining the related research works and progress of solid state laser, the relationship of beam quality and output power for solid state laser is dissertated, and the fundamental scientific question that the beam quality nonlinearly decreases with the power increase is suggested. Some important techniques to solve the problems are reviewed and the possible and effective approaches to obtain the “3 highs” solid state laser are probed．
2011,
23.
Abstract:
To improve the output power and chemical efficiency, a new method is put forward, which requires no notable change in the configurations and uses different gases as buffer gas. Some experiments are done on chemical oxygen-iodine laser (COIL) with an 11.7 cm gain length. When N2, Ar and CO2 are used as the primary and secondary buffer gases, change of the average molecular weight promotes the mixing between the primary and secondary gases. Experimental results confirm the possibility of improving the chemical efficiency. When N2 is used as the primary gas and Ar as the secondary gas, the highest output power and chemical efficiency are obtained as 3.09 kW and 30.2%.
To improve the output power and chemical efficiency, a new method is put forward, which requires no notable change in the configurations and uses different gases as buffer gas. Some experiments are done on chemical oxygen-iodine laser (COIL) with an 11.7 cm gain length. When N2, Ar and CO2 are used as the primary and secondary buffer gases, change of the average molecular weight promotes the mixing between the primary and secondary gases. Experimental results confirm the possibility of improving the chemical efficiency. When N2 is used as the primary gas and Ar as the secondary gas, the highest output power and chemical efficiency are obtained as 3.09 kW and 30.2%.
2011,
23.
Abstract:
By combining the methods of spray cooling heat transfer and micro-grooves phase change heat transfer, we design a heat sink based on throttle microgrooves phase change cooling theory. It has been proved by experiments that the vaporization rate of the coolant in the microgrooves of the cooler had reached 70%. The cooling efficiency increased rapidly while the coolant flow became smaller and the thermal management unit lighter. At the same time, we investigated the packaging of laser diode stacks with back surface cooling heat sink. Using the new technique of compound heat sink, AuSn alloy solder and the multi interface soldering, we completed the packaging of quasi-continuous wave (QCW) 3 kW laser diode stacks, with a packing spacing of 1.3 mm. It has been proved by experiments that this u
By combining the methods of spray cooling heat transfer and micro-grooves phase change heat transfer, we design a heat sink based on throttle microgrooves phase change cooling theory. It has been proved by experiments that the vaporization rate of the coolant in the microgrooves of the cooler had reached 70%. The cooling efficiency increased rapidly while the coolant flow became smaller and the thermal management unit lighter. At the same time, we investigated the packaging of laser diode stacks with back surface cooling heat sink. Using the new technique of compound heat sink, AuSn alloy solder and the multi interface soldering, we completed the packaging of quasi-continuous wave (QCW) 3 kW laser diode stacks, with a packing spacing of 1.3 mm. It has been proved by experiments that this u
2011,
23.
Abstract:
An experimental device with laser-induced breakdown spectroscopy(LIBS) for detecting the soil samples was built. The soil samples were researched by the device. According to the same latitude and different height, five locations in Bazimen landslide near Three Gorges Dam were selected to sample. The LIBS spectra of the five samples were obtained. The qualitative and quantitative analyses of Mg, Si, K, Al were performed. The result show that the content of these-elements decreased with the declining height.
An experimental device with laser-induced breakdown spectroscopy(LIBS) for detecting the soil samples was built. The soil samples were researched by the device. According to the same latitude and different height, five locations in Bazimen landslide near Three Gorges Dam were selected to sample. The LIBS spectra of the five samples were obtained. The qualitative and quantitative analyses of Mg, Si, K, Al were performed. The result show that the content of these-elements decreased with the declining height.
2011,
23.
Abstract:
Sub-aperture stitching can be used to measure large aperture optical components with low cost and high resolution by a small aperture interferometer. A program based on the improved sub-aperture stitching algorithm was compiled, and the platform for sub-aperture stitching test was established. The experimental stitching that tested a 120 mm×120 mm optical component by nine 60 mm×60 mm planar sub-apertures was performed. The peak-valley error of test was 2.37% and the root-mean-square error was only 0.27%.
Sub-aperture stitching can be used to measure large aperture optical components with low cost and high resolution by a small aperture interferometer. A program based on the improved sub-aperture stitching algorithm was compiled, and the platform for sub-aperture stitching test was established. The experimental stitching that tested a 120 mm×120 mm optical component by nine 60 mm×60 mm planar sub-apertures was performed. The peak-valley error of test was 2.37% and the root-mean-square error was only 0.27%.
2011,
23.
Abstract:
Based on the primary requirement for the magnetic field system in magnetic-bottle time-of-flight spectrometer, an appropriate combined inhomogeneous magnetic field system is designed. The inhomogeneous higher magnetic field part, with the highest field of 1.2 Ｔ, is produced by the combination of a permanent magnet and a pole piece with optimized shape. The magnet, known as NdFeB magnet, is one of rare earth permanent magnets in N52. The guiding uniform magnetic field of 1.0×10-3 T is provided by solenoid, with length of 3 m and radius of 3 cm. The pitch between the pole piece and the near end of used solenoid is determined to be 5 cm, which can satisfy the actual engineering needs．
Based on the primary requirement for the magnetic field system in magnetic-bottle time-of-flight spectrometer, an appropriate combined inhomogeneous magnetic field system is designed. The inhomogeneous higher magnetic field part, with the highest field of 1.2 Ｔ, is produced by the combination of a permanent magnet and a pole piece with optimized shape. The magnet, known as NdFeB magnet, is one of rare earth permanent magnets in N52. The guiding uniform magnetic field of 1.0×10-3 T is provided by solenoid, with length of 3 m and radius of 3 cm. The pitch between the pole piece and the near end of used solenoid is determined to be 5 cm, which can satisfy the actual engineering needs．
2011,
23.
Abstract:
Based on the computational fluid dynamics (CFD) software, an emluator for the optics and fluency coupling effects is established by means of the user defined function (UDF). Thermal blooming effects in a special tube with axial pipe flow are modeled. The simulated results indicate that the velocity distribution of the pipe flow is very asymmetric. However, the fluid density distribution is almost not changed without laser beam heating. As laser beam couples with the fluency, the fluid density distribution varies greatly. The heterogeneous fluid density distribution induces the optical path distinction of the double pearl eye form. This phenomenon is also observed in the previous experiments.
Based on the computational fluid dynamics (CFD) software, an emluator for the optics and fluency coupling effects is established by means of the user defined function (UDF). Thermal blooming effects in a special tube with axial pipe flow are modeled. The simulated results indicate that the velocity distribution of the pipe flow is very asymmetric. However, the fluid density distribution is almost not changed without laser beam heating. As laser beam couples with the fluency, the fluid density distribution varies greatly. The heterogeneous fluid density distribution induces the optical path distinction of the double pearl eye form. This phenomenon is also observed in the previous experiments.
2011,
23.
Abstract:
A matrix method is extended to solve the multimode coupling differential equations, and thereby the spectral characteristics of the chirped Bragg gratings in large-mode-area fibers (LMA FBGs) are studied theoretically. Unlike those of Bragg gratings in single mode optical fibers (SM FBGs), the reflection spectra of chirped LMA FBGs contain self-coupling and co-coupling peaks of the existing modes. For the chirped LMA FBGs, the reflectivity decreases and the reflection peaks split. These splits can be improved on some degree by Gaussian apodization function.
A matrix method is extended to solve the multimode coupling differential equations, and thereby the spectral characteristics of the chirped Bragg gratings in large-mode-area fibers (LMA FBGs) are studied theoretically. Unlike those of Bragg gratings in single mode optical fibers (SM FBGs), the reflection spectra of chirped LMA FBGs contain self-coupling and co-coupling peaks of the existing modes. For the chirped LMA FBGs, the reflectivity decreases and the reflection peaks split. These splits can be improved on some degree by Gaussian apodization function.
2011,
23.
Abstract:
The harmonic response analysis for the rotating mirror of ultra-high speed camera was presented based on the numerical analysis for obtaining the frequency-amplitude characteristic curves and stress contour under the sine excitation. There are two peak values at the 354 Hz and 1 600 Hz in the frequency-amplitude characteristic curves of rotating mirror, but the peak amplitude at 354 Hz is further larger than the other. The resonance zone of the first torsion and bending are repeated. The stress of the first bending is 358 times than the stress of rotating mirror under the uniform speed. Then, rotating mirror experimental analysis was carried out to obtain the frequency-amplitude characteristic curves of rotating mirror through the rotating mirror test system. In the displacement response c
The harmonic response analysis for the rotating mirror of ultra-high speed camera was presented based on the numerical analysis for obtaining the frequency-amplitude characteristic curves and stress contour under the sine excitation. There are two peak values at the 354 Hz and 1 600 Hz in the frequency-amplitude characteristic curves of rotating mirror, but the peak amplitude at 354 Hz is further larger than the other. The resonance zone of the first torsion and bending are repeated. The stress of the first bending is 358 times than the stress of rotating mirror under the uniform speed. Then, rotating mirror experimental analysis was carried out to obtain the frequency-amplitude characteristic curves of rotating mirror through the rotating mirror test system. In the displacement response c
2011,
23.
Abstract:
The analytical expression for the effective radius of curvature of rectangular Gaussian Schell-model (GSM) array beams propagating through atmospheric turbulence is derived. It is shown that the effective radius of curvature depends on the strength of turbulence, the beam parameters and the type of beam superposition. The effective radius of curvature decreases due to turbulence. However, for the superposition of the cross-spectral density function, effective radius of curvature is more sensitive to turbulence than that for the superposition of the intensity. In free space effective radius of curvature for the superposition of the cross-spectral density function is always larger than that for the superposition of the intensity. However, when the strength of turbulence increases, effective
The analytical expression for the effective radius of curvature of rectangular Gaussian Schell-model (GSM) array beams propagating through atmospheric turbulence is derived. It is shown that the effective radius of curvature depends on the strength of turbulence, the beam parameters and the type of beam superposition. The effective radius of curvature decreases due to turbulence. However, for the superposition of the cross-spectral density function, effective radius of curvature is more sensitive to turbulence than that for the superposition of the intensity. In free space effective radius of curvature for the superposition of the cross-spectral density function is always larger than that for the superposition of the intensity. However, when the strength of turbulence increases, effective
2011,
23.
Abstract:
The resonator’s cross section of high power chemical laser is commonly rectangle with large aspect ratio. Fast Fourier transform (FFT)method and thin gain sheet approximate calculation are used in simulating the optical resonators. Simulations give near field normalized intensity distribution, near field relative phase distribution and far field normalized intensity distribution. The output beam quality influenced by heterogeneous gain was analyzed. The numerical results also illustrated that the normalized central intensity of far field spot will turn dark along with the increasing of geometrical magnification. The method and results provide a theoretical basis for improving the beam quality.
The resonator’s cross section of high power chemical laser is commonly rectangle with large aspect ratio. Fast Fourier transform (FFT)method and thin gain sheet approximate calculation are used in simulating the optical resonators. Simulations give near field normalized intensity distribution, near field relative phase distribution and far field normalized intensity distribution. The output beam quality influenced by heterogeneous gain was analyzed. The numerical results also illustrated that the normalized central intensity of far field spot will turn dark along with the increasing of geometrical magnification. The method and results provide a theoretical basis for improving the beam quality.
2011,
23.
Abstract:
Based on a mode field coupling theory, a Gaussian approximation model to calculate the conversion efficiency of tapered fiber is presented. The simulation result is discussed and an experiment is conducted with 532 nm laser, multi-mode fiber (numerical aperture is 0.11, radius is 12.5 μm) and tapered-fiber (numerical aperture is 0.11, radius is (4±1)，(5±1)，(6±1)，(7±1) and (8±1) μm respectively) to measure conversion efficiency of tapered fiber. Good agreement is obtained between the experimental results and the theoretical calculations. A tapered fiber relay system is proposed to transport a laser beam with high power and good beam quality.
Based on a mode field coupling theory, a Gaussian approximation model to calculate the conversion efficiency of tapered fiber is presented. The simulation result is discussed and an experiment is conducted with 532 nm laser, multi-mode fiber (numerical aperture is 0.11, radius is 12.5 μm) and tapered-fiber (numerical aperture is 0.11, radius is (4±1)，(5±1)，(6±1)，(7±1) and (8±1) μm respectively) to measure conversion efficiency of tapered fiber. Good agreement is obtained between the experimental results and the theoretical calculations. A tapered fiber relay system is proposed to transport a laser beam with high power and good beam quality.
2011,
23.
Abstract:
Time-resolved force sensing technique was applied to the study on propulsive characteristics of water droplets for multi-pulse TEA (transversely excited at atmospheric pressure) CO2 laser propulsion. Laser-driven blast waves and associated flow dynamics in impulse generation processes of ablation of water droplets were studied through schlieren visualization. Experimental results show that coupling coefficient and specific impulse decrease as the interval between laser pulses and pulse numbers increase. The maximum speed of blast wave in the opposite and same direction of laser propagation is 10 km/s and 7 km/s, respectively. Time-resolved force and schlieren visualization results indicate that vaporization and blast waves dominate the impulse generation processes of water droplets for las
Time-resolved force sensing technique was applied to the study on propulsive characteristics of water droplets for multi-pulse TEA (transversely excited at atmospheric pressure) CO2 laser propulsion. Laser-driven blast waves and associated flow dynamics in impulse generation processes of ablation of water droplets were studied through schlieren visualization. Experimental results show that coupling coefficient and specific impulse decrease as the interval between laser pulses and pulse numbers increase. The maximum speed of blast wave in the opposite and same direction of laser propagation is 10 km/s and 7 km/s, respectively. Time-resolved force and schlieren visualization results indicate that vaporization and blast waves dominate the impulse generation processes of water droplets for las
2011,
23.
Abstract:
The mathematical model of coherent combination for rectangle beams array is established. Experimental results of Northrop Grumman Corporation are analyzed, such as two beam combination, four beam combination, eight beam combination. Then applying this model, it is simulated on the computer that intensity distribution of combined far-field spots changes in various conditions. Results show that aperture filling method determines the figure of far-field spots, and interval among beamlets determines distribution of energy and number of diffraction ring, and some useful results are obtained with Power-in-the-bucket calculation. The simulated results show, Power-in-the-bucket of far field spot descends with increasing distance among beamlets and number of beamlets.
The mathematical model of coherent combination for rectangle beams array is established. Experimental results of Northrop Grumman Corporation are analyzed, such as two beam combination, four beam combination, eight beam combination. Then applying this model, it is simulated on the computer that intensity distribution of combined far-field spots changes in various conditions. Results show that aperture filling method determines the figure of far-field spots, and interval among beamlets determines distribution of energy and number of diffraction ring, and some useful results are obtained with Power-in-the-bucket calculation. The simulated results show, Power-in-the-bucket of far field spot descends with increasing distance among beamlets and number of beamlets.
2011,
23.
Abstract:
A new type high accuracy 2×2 array diffraction grating structure is proposed, which has good structure stability in design method of modularization and frame structure. Designed micro-nano adjusting unit consists of differential thread and piezoelectricity driver, that realize micro-nano adjustment request of tiled-grating. Design and manufacture questions about essential parts is discussed. Preliminary test of experiment prototype indicates that the coplanar maximum relative error is 17 μm, minimum adjustment precision of micro-nano adjusting unit is possible to achieve 1.8 nm, and the resolution is 0.9 nm. The optical path experiment indicates that tiling adjusting mechanism may fast and real-time adjust 2×2 array diffraction grating to meet requirements, and stable work time is large
A new type high accuracy 2×2 array diffraction grating structure is proposed, which has good structure stability in design method of modularization and frame structure. Designed micro-nano adjusting unit consists of differential thread and piezoelectricity driver, that realize micro-nano adjustment request of tiled-grating. Design and manufacture questions about essential parts is discussed. Preliminary test of experiment prototype indicates that the coplanar maximum relative error is 17 μm, minimum adjustment precision of micro-nano adjusting unit is possible to achieve 1.8 nm, and the resolution is 0.9 nm. The optical path experiment indicates that tiling adjusting mechanism may fast and real-time adjust 2×2 array diffraction grating to meet requirements, and stable work time is large
2011,
23.
Abstract:
The evaluation of uncertainty of spot encircled parameters measured with array detectors is the main goal in this paper. Firstly, the general definition and mathematical expression of spot encircled parameters are given. Secondly, three computation methods for spot encircled parameters measured with array detectors, including approximated encircled power method, exact encircled power method, equivalent encircled size method, are summarized and compared with each other. And the corresponding discrete expressions to the three computation methods are derived based on zero order approximation. Thirdly, general expressions of uncertainty of spot encircled parameters based on equivalent encircled size method are derived according to the transfer law of uncertainty. And then several simple forms
The evaluation of uncertainty of spot encircled parameters measured with array detectors is the main goal in this paper. Firstly, the general definition and mathematical expression of spot encircled parameters are given. Secondly, three computation methods for spot encircled parameters measured with array detectors, including approximated encircled power method, exact encircled power method, equivalent encircled size method, are summarized and compared with each other. And the corresponding discrete expressions to the three computation methods are derived based on zero order approximation. Thirdly, general expressions of uncertainty of spot encircled parameters based on equivalent encircled size method are derived according to the transfer law of uncertainty. And then several simple forms
2011,
23.
Abstract:
Ablation morphology on germanium surface using multi-pulse femtosecond laser is reported. The SEM and laser focus give magnified views of the ablated portion. The ablation morphology shows a periodic surface structure with various laser pulses. And the formation of amorphous rings and ripples in the damage spot is discussed. The ablation threshold is 1.2 J·cm-2 and the ablation depth with single femtosecond laser pulse is about 150 nm. It is meanful for research the interaction of femtosecond laser and material, and the application of femtosecond laser in micromachining.
Ablation morphology on germanium surface using multi-pulse femtosecond laser is reported. The SEM and laser focus give magnified views of the ablated portion. The ablation morphology shows a periodic surface structure with various laser pulses. And the formation of amorphous rings and ripples in the damage spot is discussed. The ablation threshold is 1.2 J·cm-2 and the ablation depth with single femtosecond laser pulse is about 150 nm. It is meanful for research the interaction of femtosecond laser and material, and the application of femtosecond laser in micromachining.
2011,
23.
Abstract:
According to definition of degree of paraxiality for a monochromatic light beam, the effects of a circular aperture and a rectangular aperture on the paraxiality of a plane wave have been investigated, respectively. Analytical expressions of degree of paraxiality for a plane wave diffracted by a circular aperture and a rectangular aperture have been derived. If a plane wave is diffracted by a circular aperture or a rectangular aperture, the corresponding paraxiality decreases, which means that degree of paraxiality of the diffracted plane wave is smaller than one. Decreasing quantity of degree of paraxiality is determined by the ratio of aperture dimension to incident wavelength. The numerical results show that degree of paraxiality of the diffracted plane wave quickly augments from zero a
According to definition of degree of paraxiality for a monochromatic light beam, the effects of a circular aperture and a rectangular aperture on the paraxiality of a plane wave have been investigated, respectively. Analytical expressions of degree of paraxiality for a plane wave diffracted by a circular aperture and a rectangular aperture have been derived. If a plane wave is diffracted by a circular aperture or a rectangular aperture, the corresponding paraxiality decreases, which means that degree of paraxiality of the diffracted plane wave is smaller than one. Decreasing quantity of degree of paraxiality is determined by the ratio of aperture dimension to incident wavelength. The numerical results show that degree of paraxiality of the diffracted plane wave quickly augments from zero a
2011,
23.
Abstract:
Design and performance of a closed cycle, repetitive frequency non-chain HF laser is described. Homogeneous glow discharge is formed with UV pre-ionization and transverse discharge structure. Optimal output parameters of single pulse operation are given by investigation of discharge characteristics in SF6 /C2H6 gas mixture and output characteristics of laser pulse. Operating stability of laser device in repetition-rate mode is researched with different gas flowing velocities, charging voltage and total pressure of gas mixture. It is shown that maximal output energy of laser pulse 0.6 J and peak power 3 MW are obtained. Total efficiency of laser device is about 2.4%. When gas mixture circulating with 3.5 m/s flowing velocity, maximal running frequency of 50 Hz is obtained and operating stab
Design and performance of a closed cycle, repetitive frequency non-chain HF laser is described. Homogeneous glow discharge is formed with UV pre-ionization and transverse discharge structure. Optimal output parameters of single pulse operation are given by investigation of discharge characteristics in SF6 /C2H6 gas mixture and output characteristics of laser pulse. Operating stability of laser device in repetition-rate mode is researched with different gas flowing velocities, charging voltage and total pressure of gas mixture. It is shown that maximal output energy of laser pulse 0.6 J and peak power 3 MW are obtained. Total efficiency of laser device is about 2.4%. When gas mixture circulating with 3.5 m/s flowing velocity, maximal running frequency of 50 Hz is obtained and operating stab
2011,
23.
Abstract:
In the process of measuring the reflectivity from material surface, the thermal radiation of the material irradiated by laser usually brings obvious interference on the measurement, thus introducing a large measurement error. The measurement accuracy of the reflectivity of the high temperature section can be greatly improved by following procedure: a detector whose transmitting wavelength is different from the loading laser’s wavelength is added first, thus the light strength signal of the thermal radiation at the laser loading section and the temperature dropping section after the laser stops is detected, and at last a comparison method is adopted to eliminate the thermal radiation interference in the process of reflectivity measurement．
In the process of measuring the reflectivity from material surface, the thermal radiation of the material irradiated by laser usually brings obvious interference on the measurement, thus introducing a large measurement error. The measurement accuracy of the reflectivity of the high temperature section can be greatly improved by following procedure: a detector whose transmitting wavelength is different from the loading laser’s wavelength is added first, thus the light strength signal of the thermal radiation at the laser loading section and the temperature dropping section after the laser stops is detected, and at last a comparison method is adopted to eliminate the thermal radiation interference in the process of reflectivity measurement．
2011,
23.
Abstract:
In order to enhance intensity of Ne-like Ar 46.9 nm soft X-ray laser pumped by capillary discharge, influences of main current waveform on Z-pinch process, time of lasing onset and laser intensity were studied. Rise-time of main current waveform was changed by varying conducting inductance of main switch. Experimental results with different rise-times show that amplitude of laser spike decreases with increasing rise-time, and time of lasing onset increases with increasing rise-time. In addition, influences of average current changing rate on laser intensity were studied. When inner diameter of capillary is 3 mm and initial pressure is 30 Pa, optimum average current changing rate is about 7.0×1011 A/s.
In order to enhance intensity of Ne-like Ar 46.9 nm soft X-ray laser pumped by capillary discharge, influences of main current waveform on Z-pinch process, time of lasing onset and laser intensity were studied. Rise-time of main current waveform was changed by varying conducting inductance of main switch. Experimental results with different rise-times show that amplitude of laser spike decreases with increasing rise-time, and time of lasing onset increases with increasing rise-time. In addition, influences of average current changing rate on laser intensity were studied. When inner diameter of capillary is 3 mm and initial pressure is 30 Pa, optimum average current changing rate is about 7.0×1011 A/s.
2011,
23.
Abstract:
The character of network communication by laser diffusion from sea surface was studied by Kirchhoff approximation. The backscattering coefficient and bistatic scattering coefficient were derived through computation of laser scattering fields from two-dimensional rough sea surface according to stationary phase method and optical geometry approach. And the shadowing effect was modified by shadowing function in the process of computation. The results were validated by experiments, showing the feasibility of network communication by laser diffusion from sea surface．
The character of network communication by laser diffusion from sea surface was studied by Kirchhoff approximation. The backscattering coefficient and bistatic scattering coefficient were derived through computation of laser scattering fields from two-dimensional rough sea surface according to stationary phase method and optical geometry approach. And the shadowing effect was modified by shadowing function in the process of computation. The results were validated by experiments, showing the feasibility of network communication by laser diffusion from sea surface．
2011,
23.
Abstract:
One 3-dimensional piezostage and one rotation stage are used in two-photon fabrication systems for controlling expose time and expose power with precision as high as 0.02 ms and 7 pW respectively. By accurate controlling expose time and laser power near polymerization threshold, 35 nm and 45 nm polymer line on cover glass are obtained respectively, which is only 1/22 and 1/17 of the laser wavelength used for fabrication. These results are the highest linewidth resolution obtained by two photon fabrication on cover glass until now. It is revealed that linewidth resolution can be improved efficiently with ultra-small reduction of the expose time or expose power near polymerization threshold. The further possible improvement for resolution of two-photon process was analyzed in the paper.
One 3-dimensional piezostage and one rotation stage are used in two-photon fabrication systems for controlling expose time and expose power with precision as high as 0.02 ms and 7 pW respectively. By accurate controlling expose time and laser power near polymerization threshold, 35 nm and 45 nm polymer line on cover glass are obtained respectively, which is only 1/22 and 1/17 of the laser wavelength used for fabrication. These results are the highest linewidth resolution obtained by two photon fabrication on cover glass until now. It is revealed that linewidth resolution can be improved efficiently with ultra-small reduction of the expose time or expose power near polymerization threshold. The further possible improvement for resolution of two-photon process was analyzed in the paper.
2011,
23.
Abstract:
The advantages and disadvantages of transmission and reflection expand system are analyzed for high-power laser. The secondary mirror is selected in the form of convex paraboloid and the primary mirror in the form of concave paraboloid, which the whole system is Cassegrain system without focus. The parameters of optical system are designed by ZEMAX software based on the expanding ratio and wave aberration. The base material and coating of mirror is analyzed for high-power laser and the copper is selected as the substrate. Then the optimal design is conducted for the coating of mirrors, which the reflectivity is above 98% for the near-infrared to far-infrared waveband. The designed optical system is measured by the interferometer with the smoothness of mirror RMS better than λ/40 as the be
The advantages and disadvantages of transmission and reflection expand system are analyzed for high-power laser. The secondary mirror is selected in the form of convex paraboloid and the primary mirror in the form of concave paraboloid, which the whole system is Cassegrain system without focus. The parameters of optical system are designed by ZEMAX software based on the expanding ratio and wave aberration. The base material and coating of mirror is analyzed for high-power laser and the copper is selected as the substrate. Then the optimal design is conducted for the coating of mirrors, which the reflectivity is above 98% for the near-infrared to far-infrared waveband. The designed optical system is measured by the interferometer with the smoothness of mirror RMS better than λ/40 as the be
2011,
23.
Abstract:
Based on the relative characteristics of stimulated bioluminescence and hydrodynamic flow, the experimental platform of stimulated bioluminescence in Couette flow was built. The hydrodynamic elements stimulated bioluminescence were analysised. The threshold of shear stress for stimulated bioluminescence of Lingulodinium polyedrum is 0.1 N/m2. And bioluminescence emission is the function of shear stress and increases with it when the shear stress exceeds the threshold. The shear stress distributions of submarine were simulated by FLUENT software. The results of calculation illustrate that the shear stress decreases with the increased length of wake of submarine and it can be decreased as the oscillation of sine wave in the near area. The shear stress of wake decreases rapidly and widely wit
Based on the relative characteristics of stimulated bioluminescence and hydrodynamic flow, the experimental platform of stimulated bioluminescence in Couette flow was built. The hydrodynamic elements stimulated bioluminescence were analysised. The threshold of shear stress for stimulated bioluminescence of Lingulodinium polyedrum is 0.1 N/m2. And bioluminescence emission is the function of shear stress and increases with it when the shear stress exceeds the threshold. The shear stress distributions of submarine were simulated by FLUENT software. The results of calculation illustrate that the shear stress decreases with the increased length of wake of submarine and it can be decreased as the oscillation of sine wave in the near area. The shear stress of wake decreases rapidly and widely wit
2011,
23.
Abstract:
The paper presents the consistent displacement method to model the kinematic interface joints according to their contact form in reflector systems. The finite element (FE) model of a reflector system is built subjected to the assuming, the modal analysis and the micro-vibration calculations are done on the FE model. The most error of computing first three order intrinsic frequencies is less 5%. The displacement root mean square (RMS) responses are consistent with results of tests, the displacement RMS errors about a great number of points are less 30%. Moreover, the transfer characteristics of four kinematic interface locals are consistent with results of the test. These results show that the method of modeling results the kinematic interface joints is feasible.
The paper presents the consistent displacement method to model the kinematic interface joints according to their contact form in reflector systems. The finite element (FE) model of a reflector system is built subjected to the assuming, the modal analysis and the micro-vibration calculations are done on the FE model. The most error of computing first three order intrinsic frequencies is less 5%. The displacement root mean square (RMS) responses are consistent with results of tests, the displacement RMS errors about a great number of points are less 30%. Moreover, the transfer characteristics of four kinematic interface locals are consistent with results of the test. These results show that the method of modeling results the kinematic interface joints is feasible.
2011,
23.
Abstract:
Taking advantage of the technique of surface discharge optical pumping, a XeF(C-A) laser which can operate in the repetition mode is developed. The maximal repetitive rate is up to 10 Hz. The influence of repetitive rate and gas flow rate on the stability of output energy is studied and the main factors which influence the stability of output energy are analyzed. The experimental results show that increasing the gas feed rate into laser chamber can improve the stability of output energy. The ideal output energy results of 20 laser pulses under different repetitive rate and optimal experimental conditions are given. Output energy more than 4 J and better stability can be obtained when laser device runs at 1, 2 and 5 Hz, respectively. When the gas feed rate is larger than 53 L/s, the stabili
Taking advantage of the technique of surface discharge optical pumping, a XeF(C-A) laser which can operate in the repetition mode is developed. The maximal repetitive rate is up to 10 Hz. The influence of repetitive rate and gas flow rate on the stability of output energy is studied and the main factors which influence the stability of output energy are analyzed. The experimental results show that increasing the gas feed rate into laser chamber can improve the stability of output energy. The ideal output energy results of 20 laser pulses under different repetitive rate and optimal experimental conditions are given. Output energy more than 4 J and better stability can be obtained when laser device runs at 1, 2 and 5 Hz, respectively. When the gas feed rate is larger than 53 L/s, the stabili
2011,
23.
Abstract:
The fabrication procedures of dual-layer cylindrical carbonized resorcinol formaldehyde (CRF) aerogel/polystyrene (CH) target were investigated. The organic cylindrical RF aerogel was synthesized by using sol-gel process and micro-shaped method, the cylindrical CRF aerogel was prepared by pyrolyzing the cylindrical RF aerogel under the protection of nitrogen. The density and diameter of cylindrical CRF aerogel were about 250 mg·cm-3 and 730 μm. The dual-media CRF/CH target with the length of about 1 mm and inner diameter of 730 μm was formed by using dip-coating and micro-cutting process. The preparation process of cylindrical RF and CRF aerogel was discussed. The scanning electron microscope (SEM) was used to measure the microstructure of cylindrical RF and CRF aerogel and the interfac
The fabrication procedures of dual-layer cylindrical carbonized resorcinol formaldehyde (CRF) aerogel/polystyrene (CH) target were investigated. The organic cylindrical RF aerogel was synthesized by using sol-gel process and micro-shaped method, the cylindrical CRF aerogel was prepared by pyrolyzing the cylindrical RF aerogel under the protection of nitrogen. The density and diameter of cylindrical CRF aerogel were about 250 mg·cm-3 and 730 μm. The dual-media CRF/CH target with the length of about 1 mm and inner diameter of 730 μm was formed by using dip-coating and micro-cutting process. The preparation process of cylindrical RF and CRF aerogel was discussed. The scanning electron microscope (SEM) was used to measure the microstructure of cylindrical RF and CRF aerogel and the interfac
2011,
23.
Abstract:
Experiments of frequency-tripled laser beam on the Al flat target are carried on the XINGGUANG Ⅱ laser facility. A flat-grating spectrometer is used to measure Al plasma X-ray in the range of 3 nm to 6 nm. Based on relativistic multi configuration interaction, and taking account of CI interaction and correction of Berit, L shell lines have been computed by Cowan codes. A total of 22 spectral features are identified, and calculations agree with experimental emission spectra. Results show that identified lines belong to transitions from 2s, 2p of L shell to 3s, 3p shell, even higher shell, and maximum difference between our measurements and theoretical results is only 0.06 nm. The results of oscillator strength and other theoretical results are consistent.
Experiments of frequency-tripled laser beam on the Al flat target are carried on the XINGGUANG Ⅱ laser facility. A flat-grating spectrometer is used to measure Al plasma X-ray in the range of 3 nm to 6 nm. Based on relativistic multi configuration interaction, and taking account of CI interaction and correction of Berit, L shell lines have been computed by Cowan codes. A total of 22 spectral features are identified, and calculations agree with experimental emission spectra. Results show that identified lines belong to transitions from 2s, 2p of L shell to 3s, 3p shell, even higher shell, and maximum difference between our measurements and theoretical results is only 0.06 nm. The results of oscillator strength and other theoretical results are consistent.
2011,
23.
Abstract:
Carbon aerogels (CA) were prepared from the sol-gel polycondensatin of resorcinol (R) and formaldehyde (F) as raw materials. They were then activated by carbon dioxide. The micro-structure and adsorption properties of hydrogen were analyzed by using thermal gravimetric analysis (TG), X-ray diffraction (XRD) and adsorption isotherms of hydrogen. The results show that CO2 activation doesn’t destroy the miropores framework of CA, but substantially increases the specific surface area. With the increase of activation temperature, the amorphous nature of the carbon aerogels becomes more apparent, the weight loss shows a significant increase, and the micropore volume, specific surface area and adsorption capacity of hydrogen increase firstly and then decrease. Thus the hydrogen adsorption capaci
Carbon aerogels (CA) were prepared from the sol-gel polycondensatin of resorcinol (R) and formaldehyde (F) as raw materials. They were then activated by carbon dioxide. The micro-structure and adsorption properties of hydrogen were analyzed by using thermal gravimetric analysis (TG), X-ray diffraction (XRD) and adsorption isotherms of hydrogen. The results show that CO2 activation doesn’t destroy the miropores framework of CA, but substantially increases the specific surface area. With the increase of activation temperature, the amorphous nature of the carbon aerogels becomes more apparent, the weight loss shows a significant increase, and the micropore volume, specific surface area and adsorption capacity of hydrogen increase firstly and then decrease. Thus the hydrogen adsorption capaci
2011,
23.
Abstract:
Image relay and angular multiplexing, which should be considered together in the design of high power excimer laser system, is reviewed. It’s important to select proper illumination setup and laser beam shaping techniques. Given the complex and special angular multiplexing scheme in high power excimer laser systems, some detailed conceptual layout schemes are given in the paper. After a brief description of lens array and reflective telescope objective, which combine the incoming beams to a common focus, a new schematic layout which uses the final targeting optics and one optical delay line array, to realize multiplexing and de-multiplexing simultaneously is first proposed in the paper.
Image relay and angular multiplexing, which should be considered together in the design of high power excimer laser system, is reviewed. It’s important to select proper illumination setup and laser beam shaping techniques. Given the complex and special angular multiplexing scheme in high power excimer laser systems, some detailed conceptual layout schemes are given in the paper. After a brief description of lens array and reflective telescope objective, which combine the incoming beams to a common focus, a new schematic layout which uses the final targeting optics and one optical delay line array, to realize multiplexing and de-multiplexing simultaneously is first proposed in the paper.
2011,
23.
Abstract:
Imaging velocity interferometer system for any reflector(VISAR) is an important diagnostic facility for the measurement of the shock wave velocity in the transparent material. An imaging VISAR has been installed and used in the SG-Ⅲ prototype laser facility. The key points and special techniques in designing an imaging VISAR are described in detail. Analyzing and testing the capability of the imaging VISAR indicates that the temporal resolution of the system is 30 ps, and the spatial resolution is better than 10 μm. Experiments are carried out on the SG-Ⅲ prototype laser facility and high quality interference images are obtained.
Imaging velocity interferometer system for any reflector(VISAR) is an important diagnostic facility for the measurement of the shock wave velocity in the transparent material. An imaging VISAR has been installed and used in the SG-Ⅲ prototype laser facility. The key points and special techniques in designing an imaging VISAR are described in detail. Analyzing and testing the capability of the imaging VISAR indicates that the temporal resolution of the system is 30 ps, and the spatial resolution is better than 10 μm. Experiments are carried out on the SG-Ⅲ prototype laser facility and high quality interference images are obtained.
2011,
23.
Abstract:
The polyimide (PI) films of pyromellitic dianhydride-oxydiamiline (PMDA-ODA) were fabricated using vapor deposition polymerization (VDP) method under high vacuum pressure of 10-4 Pa level. The influence of equipment, substrate temperature, the process of heating and deposition ratio of monomers on the surface roughness of the PI films was investigated. The surface topography of films was measured by interferometer microscopy and scanning electron microscopy (SEM), and the surface roughness was probed with atomic force microscopy（AFM）. The results show that consecutive films can be formed when the distance from steering flow pipe to substrate is 74 cm. The surface roughnesses are 291.2 nm and 61.9 nm respectively for one-step heating process and multi-step heating process, and
The polyimide (PI) films of pyromellitic dianhydride-oxydiamiline (PMDA-ODA) were fabricated using vapor deposition polymerization (VDP) method under high vacuum pressure of 10-4 Pa level. The influence of equipment, substrate temperature, the process of heating and deposition ratio of monomers on the surface roughness of the PI films was investigated. The surface topography of films was measured by interferometer microscopy and scanning electron microscopy (SEM), and the surface roughness was probed with atomic force microscopy（AFM）. The results show that consecutive films can be formed when the distance from steering flow pipe to substrate is 74 cm. The surface roughnesses are 291.2 nm and 61.9 nm respectively for one-step heating process and multi-step heating process, and
2011,
23.
Abstract:
Aiming at solving the problem of low pumping efficiency of typical Zr/KClO4 pump source for pyrotechnically pumped laser, influence of particle size of Zr powders on the combustion property of Zr/KClO4 was investigated. It was indicated when the particle size of Zr powders decreased from 61.375 μm to 18.675 μm, the ignition temperatures of Zr/KClO4 dropped from 506.40 ℃ to 492.42 ℃, flash radiation lasting time shortened from 60 ms to 25 ms, peak flash intensities increased about 1 times.Spectral measurement showed the radiation spectra of Zr/KClO4 were continuous spectra with superposition of selective linear or band emissions of excited atoms or molecules. With the decrease of Zr particle, the emission of molecular ZrO strengthened, and radiation effi
Aiming at solving the problem of low pumping efficiency of typical Zr/KClO4 pump source for pyrotechnically pumped laser, influence of particle size of Zr powders on the combustion property of Zr/KClO4 was investigated. It was indicated when the particle size of Zr powders decreased from 61.375 μm to 18.675 μm, the ignition temperatures of Zr/KClO4 dropped from 506.40 ℃ to 492.42 ℃, flash radiation lasting time shortened from 60 ms to 25 ms, peak flash intensities increased about 1 times.Spectral measurement showed the radiation spectra of Zr/KClO4 were continuous spectra with superposition of selective linear or band emissions of excited atoms or molecules. With the decrease of Zr particle, the emission of molecular ZrO strengthened, and radiation effi
2011,
23.
Abstract:
Diamonds have high thermal conductivity, resistivity and breakdown field, fast charge collection, low leakage current, wide band-gap, low dielectric constant, large carrier drift velocity and outstanding radiation hardness. A class of wide band-gap semiconductor offers an attractive alternative to Si and X-ray diode detector technologies for X-ray detection in inertial confinement fusion(ICF) experiments. Using chemical-vapor-deposited (CVD) technology, 1 mm×1 mm×2 mm(type-A) and 1 mm×1 mm×3 mm(type-B) diamonds were synthesized. The quality of the diamonds was examined by Ramma spectrum. The detectors was fielded and characteristics of these detectors were studied on a 8 ps pulse-wide laser equipment. The results indicate that rising time and FWHM of the detector system reach 60 ps and
Diamonds have high thermal conductivity, resistivity and breakdown field, fast charge collection, low leakage current, wide band-gap, low dielectric constant, large carrier drift velocity and outstanding radiation hardness. A class of wide band-gap semiconductor offers an attractive alternative to Si and X-ray diode detector technologies for X-ray detection in inertial confinement fusion(ICF) experiments. Using chemical-vapor-deposited (CVD) technology, 1 mm×1 mm×2 mm(type-A) and 1 mm×1 mm×3 mm(type-B) diamonds were synthesized. The quality of the diamonds was examined by Ramma spectrum. The detectors was fielded and characteristics of these detectors were studied on a 8 ps pulse-wide laser equipment. The results indicate that rising time and FWHM of the detector system reach 60 ps and
2011,
23.
Abstract:
Using electron beam evaporation, a 355 nm separator was designed by depositiing SiO2 and HfO2 alternatively. The coating has a reflectivity of larger than 99% at 355 nm through optimization and a transmittance larger than 99% at 532 nm and 1 064 nm. It has good electric-field distribution. The spectra of the fabricated coating is close to the designed one. The laser-induced damage threshold of the coating is 5.1 J/cm2. Morphology of laser-induced damage of the coating was characterized by differential interference contrast microscope．
Using electron beam evaporation, a 355 nm separator was designed by depositiing SiO2 and HfO2 alternatively. The coating has a reflectivity of larger than 99% at 355 nm through optimization and a transmittance larger than 99% at 532 nm and 1 064 nm. It has good electric-field distribution. The spectra of the fabricated coating is close to the designed one. The laser-induced damage threshold of the coating is 5.1 J/cm2. Morphology of laser-induced damage of the coating was characterized by differential interference contrast microscope．
2011,
23.
Abstract:
With metal alkoxide as precursor, Ta2O5 aerogels were prepared by sol-gel technique. The sol-gel process is found to be affected by water amount, catalyst amount and concentration of Ta(OC2H5)5. The gelation can only happen in the presence of strong acid as catalyst, and with the increase of acid strength, the gelation time is obviously decreased. With the continuous increase of water, the gelation time lengthens and then tends to be constant. Additionally, the gelation time increases and the theoretical density of Ta2O5aerogel decreases as the solvent amount increases. Through sol-gel process control along with supercritical drying technique, the Ta2O5 aerogel with a low density of 44 mg/cm3 was prepared.
With metal alkoxide as precursor, Ta2O5 aerogels were prepared by sol-gel technique. The sol-gel process is found to be affected by water amount, catalyst amount and concentration of Ta(OC2H5)5. The gelation can only happen in the presence of strong acid as catalyst, and with the increase of acid strength, the gelation time is obviously decreased. With the continuous increase of water, the gelation time lengthens and then tends to be constant. Additionally, the gelation time increases and the theoretical density of Ta2O5aerogel decreases as the solvent amount increases. Through sol-gel process control along with supercritical drying technique, the Ta2O5 aerogel with a low density of 44 mg/cm3 was prepared.
2011,
23.
Abstract:
Spherical nickel nanoparticles with about 75~200 nm in size were obtained by a liquid reduction method. The nickel nanoparticles/PS composites were synthesized via in situ polymerization method. XRD, FTIR, SEM and TG-DSC were respectively used to measure the properties of nickel nanoparticles, the microstructure of as-prepared composites samples, the distribution of nickel nanoparticles in PS and the thermodynamic parameters of as-prepared composites. The results show that the nickel nanoparticles will enhance the glass transition temperature of nano-Ni/PS composites. The enthalpy of composites is heightened by increasing of doping dose, and it reaches the top when the doping dose is from 1% to 2%. The specific heat of the composites will reduce with the doping dose of nickel nanoparticles
Spherical nickel nanoparticles with about 75~200 nm in size were obtained by a liquid reduction method. The nickel nanoparticles/PS composites were synthesized via in situ polymerization method. XRD, FTIR, SEM and TG-DSC were respectively used to measure the properties of nickel nanoparticles, the microstructure of as-prepared composites samples, the distribution of nickel nanoparticles in PS and the thermodynamic parameters of as-prepared composites. The results show that the nickel nanoparticles will enhance the glass transition temperature of nano-Ni/PS composites. The enthalpy of composites is heightened by increasing of doping dose, and it reaches the top when the doping dose is from 1% to 2%. The specific heat of the composites will reduce with the doping dose of nickel nanoparticles
2011,
23.
Abstract:
Temporal shaping of drive laser pulse was done by using pulse stacking method. Perfect result was measured by streak camera system. A quasi-ellipsoid shaping scheme based on pulse stacking was projected. The simulation results show: pulse stacking is benefit to improve the beam emittance; 8 micro pulses stacking is more effective than 4 micro pulses stacking; besides, the beam emittance will be further improved by quasi-ellipsoid shaping．
Temporal shaping of drive laser pulse was done by using pulse stacking method. Perfect result was measured by streak camera system. A quasi-ellipsoid shaping scheme based on pulse stacking was projected. The simulation results show: pulse stacking is benefit to improve the beam emittance; 8 micro pulses stacking is more effective than 4 micro pulses stacking; besides, the beam emittance will be further improved by quasi-ellipsoid shaping．
2011,
23.
Abstract:
Schottky diagnostics are often used in circular accelerators and in storage rings. A brief introduction on the longitudinal Schottky signal basics and a report on the elements of Schottky diagnostic system at CSRe are presented. The system consists of a pair of Schottky electrodes, λ/4 helical resonator, low noise amplifier and data acquisition device. Test measurement results of the frequency measurement and sensitivity measurement with 78Kr36+ beam of 481.88 MeV/u circulating in the storage ring CSRe are obtained. The results show that the system is sensitive to the beam current larger than 82 nA.
Schottky diagnostics are often used in circular accelerators and in storage rings. A brief introduction on the longitudinal Schottky signal basics and a report on the elements of Schottky diagnostic system at CSRe are presented. The system consists of a pair of Schottky electrodes, λ/4 helical resonator, low noise amplifier and data acquisition device. Test measurement results of the frequency measurement and sensitivity measurement with 78Kr36+ beam of 481.88 MeV/u circulating in the storage ring CSRe are obtained. The results show that the system is sensitive to the beam current larger than 82 nA.
2011,
23.
Abstract:
In order to get basic physical parameters of radiation environment for detector or sample irradiation experiment and optimal target material choice, Monte Carlo simulation software FLUKA is used to calculate parameters of mixed radiation environment in target chamber Ⅱ on E2 line of test beam. At last, physical parameters: secondary particles differential fluencies, secondary particles angular differential cross-section, dual differential energy spectrum, dose rate distribution are acquired.
In order to get basic physical parameters of radiation environment for detector or sample irradiation experiment and optimal target material choice, Monte Carlo simulation software FLUKA is used to calculate parameters of mixed radiation environment in target chamber Ⅱ on E2 line of test beam. At last, physical parameters: secondary particles differential fluencies, secondary particles angular differential cross-section, dual differential energy spectrum, dose rate distribution are acquired.
2011,
23.
Abstract:
The dielectric single-surface multipactor discharge was theoretically analyzed and numerically simulated. Firstly, the dynamics equations, and the distributions of initial emission energy and angle of secondary electrons were introduced, and the susceptibility curve of multipactor discharge was estimated and analyzed in theory depending on material characteristic of secondary emission. Secondly, Using Monte-Carlo method simulating the initial emission energy and angle, the susceptibility curve of multipactor discharge was studied and discussed compared with the theoretic results, and the relationship was given between the number of secondary electrons and time. Finally, considering electron beam loading and saturation, the particular Monte-Carlo method with fixed time step was adopted in s
The dielectric single-surface multipactor discharge was theoretically analyzed and numerically simulated. Firstly, the dynamics equations, and the distributions of initial emission energy and angle of secondary electrons were introduced, and the susceptibility curve of multipactor discharge was estimated and analyzed in theory depending on material characteristic of secondary emission. Secondly, Using Monte-Carlo method simulating the initial emission energy and angle, the susceptibility curve of multipactor discharge was studied and discussed compared with the theoretic results, and the relationship was given between the number of secondary electrons and time. Finally, considering electron beam loading and saturation, the particular Monte-Carlo method with fixed time step was adopted in s
2011,
23.
Abstract:
In this paper, a new type of circular polarizer is presented. Based on the characteristic of TE11 degenerate modes of circular waveguide and different phase velocities of long and short axes of elliptical waveguide, TE11 mode circular polarizer with elliptical waveguide is developed successfully. According to boundary conditions of microwave transmission, one incident TE11 mode is divided into two orthogonal TE11 modes with same magnitude. By adjusting length of elliptical waveguide, phase difference of two orthogonal TE11 modes is 90°, and conversion from linear polarization to circular polarization is realized. By FDTD software, circular polarizer is designed and optimized. Manufactured circular polarizer was measured by cold test and high-power microwav
In this paper, a new type of circular polarizer is presented. Based on the characteristic of TE11 degenerate modes of circular waveguide and different phase velocities of long and short axes of elliptical waveguide, TE11 mode circular polarizer with elliptical waveguide is developed successfully. According to boundary conditions of microwave transmission, one incident TE11 mode is divided into two orthogonal TE11 modes with same magnitude. By adjusting length of elliptical waveguide, phase difference of two orthogonal TE11 modes is 90°, and conversion from linear polarization to circular polarization is realized. By FDTD software, circular polarizer is designed and optimized. Manufactured circular polarizer was measured by cold test and high-power microwav
2011,
23.
Abstract:
A broad spectra detection system is developed, which includes the UV-ray imaging detector and X-ray imaging detector. By this system, the UV-ray and X-ray induced by dielectric breakdown which occures in vacuum under microwave field are diagnosed. The results show that the X-ray dose is 9.28×102～1.64×103 Gy in the environment and 5.38×102～1.09×103 Gy when dielectric breakdown occurs, as the operation parameters of HPM source is 100 Hz and 5 s. As the HPM pulses repetition frenquence and operation time increases, accordingly, the induced X-ray dose increases obviously. Furthermore, the UV-ray induced by HPM dielectric breakdown can be observed through this broad spectra detection system．
A broad spectra detection system is developed, which includes the UV-ray imaging detector and X-ray imaging detector. By this system, the UV-ray and X-ray induced by dielectric breakdown which occures in vacuum under microwave field are diagnosed. The results show that the X-ray dose is 9.28×102～1.64×103 Gy in the environment and 5.38×102～1.09×103 Gy when dielectric breakdown occurs, as the operation parameters of HPM source is 100 Hz and 5 s. As the HPM pulses repetition frenquence and operation time increases, accordingly, the induced X-ray dose increases obviously. Furthermore, the UV-ray induced by HPM dielectric breakdown can be observed through this broad spectra detection system．
2011,
23.
Abstract:
The Rayleigh hydrodynamic-instability theory is applied to determine the frequency range of jet oscillation waves in the liquid-droplet generator. The charged capacity of each liquid droplet and the intensity of electric deviation field are derived by analyzing the charge and deviation process. The quantitative relationship between the oscillation-wave frequency for the optimum deviation and the initial jet velocity as well as the width of the charged ring is determined. Under the conditions of the different pressure, 0.02, 0.03, 0.04, 0.05, and 0.06 MPa, for feeding materials, the initial velocity of the jet with the diameter of 0.10, 0.11, and 0.15 mm is measured, respectively.
The Rayleigh hydrodynamic-instability theory is applied to determine the frequency range of jet oscillation waves in the liquid-droplet generator. The charged capacity of each liquid droplet and the intensity of electric deviation field are derived by analyzing the charge and deviation process. The quantitative relationship between the oscillation-wave frequency for the optimum deviation and the initial jet velocity as well as the width of the charged ring is determined. Under the conditions of the different pressure, 0.02, 0.03, 0.04, 0.05, and 0.06 MPa, for feeding materials, the initial velocity of the jet with the diameter of 0.10, 0.11, and 0.15 mm is measured, respectively.
2011,
23.
Abstract:
The ion thruster plume model was established and a numerical simulation using the particle-in-cell method was adopted to obtain charge-exchange(CEX) ions distribution in the plume. The full approximation storage-algebraic multigrid method is used to update the electric field. A three dimensional parallel particle simulation code has been developed by using the compute unified device architecture for graphic processor unit. The results show that CEX ions will go toward outside of the ion beam due to the expansion structure of the electric potential and some will go back to the upstream of the ion thruster. The ion number density is three to four order lower than that in the beam. The backflow current of CEX ions will be reduced as the electric temperature in the plume is reduced.
The ion thruster plume model was established and a numerical simulation using the particle-in-cell method was adopted to obtain charge-exchange(CEX) ions distribution in the plume. The full approximation storage-algebraic multigrid method is used to update the electric field. A three dimensional parallel particle simulation code has been developed by using the compute unified device architecture for graphic processor unit. The results show that CEX ions will go toward outside of the ion beam due to the expansion structure of the electric potential and some will go back to the upstream of the ion thruster. The ion number density is three to four order lower than that in the beam. The backflow current of CEX ions will be reduced as the electric temperature in the plume is reduced.
2011,
23.
Abstract:
A model of a plane target under laser irradiation is used to numerically simulate the temperature distribution in different speed airflow, using the thermal coupling method of gas and solid. The results show that there is a higher equilibrium temperature over the plane target when there is no laser irradiation, and the heat transfer coefficient between air and the plane target increases with the airflow speed; with a maximum value occurring at the front edge of the target, it declines along the target length. When under laser irradiation in different cases, the temperature distribution in the plane is analyzed carefully, and the influence of aerodynamic heating, forced convection cooling and laser heating is focused to compare their thermal competition，which shows that the temperature di
A model of a plane target under laser irradiation is used to numerically simulate the temperature distribution in different speed airflow, using the thermal coupling method of gas and solid. The results show that there is a higher equilibrium temperature over the plane target when there is no laser irradiation, and the heat transfer coefficient between air and the plane target increases with the airflow speed; with a maximum value occurring at the front edge of the target, it declines along the target length. When under laser irradiation in different cases, the temperature distribution in the plane is analyzed carefully, and the influence of aerodynamic heating, forced convection cooling and laser heating is focused to compare their thermal competition，which shows that the temperature di
2011,
23.
Abstract:
The applicability, advantages and disadvantages of quasi-neutral assumption, Boltzmann distribution assumption, and particle model of electrons in the electric thruster flow simulation are analyzed. Based on the analysis, a new method: electron drift-diffusion approximation is presented, which is used to simulate the plasma movement in optical system of ion thruster, and its feasibility is verified in optical system simulation. Simulation results show the plasma potential distribution, ion phase space distribution and the electron density distribution is consistent with the results of the Boltzmann distribution assumption, and the feasibility of this new method is verified.
The applicability, advantages and disadvantages of quasi-neutral assumption, Boltzmann distribution assumption, and particle model of electrons in the electric thruster flow simulation are analyzed. Based on the analysis, a new method: electron drift-diffusion approximation is presented, which is used to simulate the plasma movement in optical system of ion thruster, and its feasibility is verified in optical system simulation. Simulation results show the plasma potential distribution, ion phase space distribution and the electron density distribution is consistent with the results of the Boltzmann distribution assumption, and the feasibility of this new method is verified.
2011,
23.
Abstract:
The dose produced by the hot electrons from the laser-foil target interaction has been measured by using a LiF thermoluminescence dosimeters (TLDs) stack. The hot electron energy distribution has been obtained from the mass stopping power of the electron in the LiF TLDs. The hot electron energy distribution of the PIC simulation is more consistent with the result from the experiment. The theoretical analysis proves that the resonance absorption is the primary mechanism of the electron acceleration.
The dose produced by the hot electrons from the laser-foil target interaction has been measured by using a LiF thermoluminescence dosimeters (TLDs) stack. The hot electron energy distribution has been obtained from the mass stopping power of the electron in the LiF TLDs. The hot electron energy distribution of the PIC simulation is more consistent with the result from the experiment. The theoretical analysis proves that the resonance absorption is the primary mechanism of the electron acceleration.
2011,
23.
Abstract:
This paper presents demonstration experiments on changing shock wave structure by dielectric barrier discharge (DBD). It shows that DBD can influence on the boundary layer. The intension of the shock wave decreases as the discharge obeys the flows, and it increases as the discharge disobeys the flows. When the discharge disobeys the flows, the ratio of pressure as discharge using three pairs electrode is greater than discharge using four pairs electrode. Because the discharge area is much smaller than the boundary layer in this experiment, the body force induced by plasma aerodynamic actuation is negligible compared with high speed flow aerodynamic force. Thus the effect on shock wave is pretty weak．
This paper presents demonstration experiments on changing shock wave structure by dielectric barrier discharge (DBD). It shows that DBD can influence on the boundary layer. The intension of the shock wave decreases as the discharge obeys the flows, and it increases as the discharge disobeys the flows. When the discharge disobeys the flows, the ratio of pressure as discharge using three pairs electrode is greater than discharge using four pairs electrode. Because the discharge area is much smaller than the boundary layer in this experiment, the body force induced by plasma aerodynamic actuation is negligible compared with high speed flow aerodynamic force. Thus the effect on shock wave is pretty weak．
2011,
23.
Abstract:
A lateral force sensor based on low birefringence photonic crystal fiber Sagnac interferometer is proposed. The sinusoidal interference spectrum is produced due to the initial lateral force which is pre-applied on the low birefringence fiber. The load placed on the fiber introduces extra birefringence and corresponding spectrum shift for measurement. The sensitivity achieved is 0.529 nm/(N·mm). The property of temperature-insensitivity is verified in the experiment with the temperature coefficient of -0.4 pm/℃ which can be neglected.
A lateral force sensor based on low birefringence photonic crystal fiber Sagnac interferometer is proposed. The sinusoidal interference spectrum is produced due to the initial lateral force which is pre-applied on the low birefringence fiber. The load placed on the fiber introduces extra birefringence and corresponding spectrum shift for measurement. The sensitivity achieved is 0.529 nm/(N·mm). The property of temperature-insensitivity is verified in the experiment with the temperature coefficient of -0.4 pm/℃ which can be neglected.
2011,
23.
Abstract:
Thermodynamic properties and electronic structure of surface heart cubic phase fcc-6Li2O is studied by DFT and quasi-harmonic Debye model. Thermal expansion coefficient of 6Li2O reduces obviously with increased pressure under any temperature. Under low pressure (less than 40 GPa), temperature can cause distinct variety of thermal expansion. Radius of O atom decreases rapidly with pressure, but change caused by temperature is obscure. Under lower pressure (less than 40 GPa), band gap reduces just a little with temperature. Whereas, changes caused by temperature will almost be ignored under high pressure (more than 40 GPa). With raising of pressure, transition of electrons in valence band to high level will produce increasing of band gap.
Thermodynamic properties and electronic structure of surface heart cubic phase fcc-6Li2O is studied by DFT and quasi-harmonic Debye model. Thermal expansion coefficient of 6Li2O reduces obviously with increased pressure under any temperature. Under low pressure (less than 40 GPa), temperature can cause distinct variety of thermal expansion. Radius of O atom decreases rapidly with pressure, but change caused by temperature is obscure. Under lower pressure (less than 40 GPa), band gap reduces just a little with temperature. Whereas, changes caused by temperature will almost be ignored under high pressure (more than 40 GPa). With raising of pressure, transition of electrons in valence band to high level will produce increasing of band gap.
2011,
23.
Abstract:
To study the velocity skin effect of railgun with solid armature, the relationships between the electromagnetic parameters and armature moving velocity were presented by Maxwell electromagnetic theory. The two-dimensional partial differential equations for electromagnetic field and temperature field in Cartesian coordinate system were set up; For a rectangular solid armature, the boundary conditions and excitation functions were described for the equations, the partial differential equations were resolved using finite difference method, the results were analyzed and the distributions of magnetic induction, temperature and current density within the rail and armature were obtained. The final results show that, the armature movement causes a high current density concentrating on the tail end
To study the velocity skin effect of railgun with solid armature, the relationships between the electromagnetic parameters and armature moving velocity were presented by Maxwell electromagnetic theory. The two-dimensional partial differential equations for electromagnetic field and temperature field in Cartesian coordinate system were set up; For a rectangular solid armature, the boundary conditions and excitation functions were described for the equations, the partial differential equations were resolved using finite difference method, the results were analyzed and the distributions of magnetic induction, temperature and current density within the rail and armature were obtained. The final results show that, the armature movement causes a high current density concentrating on the tail end
2011,
23.
Abstract:
A novel wide-spectrum electromagnetic pulse test system is designed. This system makes use of all-inductive isolated repetition frequency Marx generator to produce high-voltage pulse which is then fed into broadband antenna for wide-spectrum radiation through bipolar pulse-forming line. Working principle of this generator and forming principle of bipolar pulse are both introduced. By means of experiment, following qualifications of the system is concluded, output pulse voltage 500 kV, front edge 20 ns, repetition frequency 20 Hz, wide spectrum radiation factor 195 kV, center radiation frequency 200 MHz, spectrum width 37%. Test system has compact configuration and flexible operation and has also 360 degree rotation at azimuth radiation and the remote control function.
A novel wide-spectrum electromagnetic pulse test system is designed. This system makes use of all-inductive isolated repetition frequency Marx generator to produce high-voltage pulse which is then fed into broadband antenna for wide-spectrum radiation through bipolar pulse-forming line. Working principle of this generator and forming principle of bipolar pulse are both introduced. By means of experiment, following qualifications of the system is concluded, output pulse voltage 500 kV, front edge 20 ns, repetition frequency 20 Hz, wide spectrum radiation factor 195 kV, center radiation frequency 200 MHz, spectrum width 37%. Test system has compact configuration and flexible operation and has also 360 degree rotation at azimuth radiation and the remote control function.
2011,
23.
Abstract:
Applying the case signal model, a preliminary understanding of electromagnetic pulse(EMP) generated by detonations in space has been developed in this paper. Taking into account of the relativistic effects, recalculation of the formation time of the space charge limit was accomplished which suggested that once the space charge was formed, the system could be treated as in the quasi-steady situation. Based on that point, frequency of the space charge oscillations has been analytically derived and semi-numerically calculated. The results agree with each other very well. For observers in large distances, a net dipole moment can be resulted from the average movements of space charges. Calculations indicate that the peak value of the radiation signal in the far field always appears before the m
Applying the case signal model, a preliminary understanding of electromagnetic pulse(EMP) generated by detonations in space has been developed in this paper. Taking into account of the relativistic effects, recalculation of the formation time of the space charge limit was accomplished which suggested that once the space charge was formed, the system could be treated as in the quasi-steady situation. Based on that point, frequency of the space charge oscillations has been analytically derived and semi-numerically calculated. The results agree with each other very well. For observers in large distances, a net dipole moment can be resulted from the average movements of space charges. Calculations indicate that the peak value of the radiation signal in the far field always appears before the m
2011,
23.
Abstract:
In order to get important characteristic parameters of three kinds of domestic amorphous cores under the conditions of high frequency and fast pulses, frequency response and fast-pulse response of these cores are analyzed in detail in this paper. In the test circuit of a 1∶1 transformer, attenuation ratio of the response voltage increased from 0 to 50%~60% when the frequency of the sinusoidal source voltage increased from 1 MHz to 20 MHz. According to theoretical analysis, high-frequency eddy loss caused this voltage attenuation. Fast-pulse response of amorphous cores were also studied, and experimental results showed that these cores responded inferiorly to the amplitude and flat top of the square pulse when the pulse width was less than 30 ns. However, response signal and source signal
In order to get important characteristic parameters of three kinds of domestic amorphous cores under the conditions of high frequency and fast pulses, frequency response and fast-pulse response of these cores are analyzed in detail in this paper. In the test circuit of a 1∶1 transformer, attenuation ratio of the response voltage increased from 0 to 50%~60% when the frequency of the sinusoidal source voltage increased from 1 MHz to 20 MHz. According to theoretical analysis, high-frequency eddy loss caused this voltage attenuation. Fast-pulse response of amorphous cores were also studied, and experimental results showed that these cores responded inferiorly to the amplitude and flat top of the square pulse when the pulse width was less than 30 ns. However, response signal and source signal
2011,
23.
Abstract:
It was demonstrated, based on the PSPICE circuit simulation, that the sectioning number for the circuit simulation of an exponential transmission line should be determined as twice the line’s one-way electromagnetic wave transport time (electric length) divided by the wave-front of input pulse, owing to elimination of the wave reflections caused by artificial impedance discontinuity in the line’s circuit simulation model, which employs a serial and sectional transmission line with impedances constant in each section but stair-step-varied between sections, and with total electric length the same as that of the exponential line under simulation. A pulse of 112.2 ns wave-front propagates through an exponential water transmission line of 1 234.2 ns one-way transport time will give the best s
It was demonstrated, based on the PSPICE circuit simulation, that the sectioning number for the circuit simulation of an exponential transmission line should be determined as twice the line’s one-way electromagnetic wave transport time (electric length) divided by the wave-front of input pulse, owing to elimination of the wave reflections caused by artificial impedance discontinuity in the line’s circuit simulation model, which employs a serial and sectional transmission line with impedances constant in each section but stair-step-varied between sections, and with total electric length the same as that of the exponential line under simulation. A pulse of 112.2 ns wave-front propagates through an exponential water transmission line of 1 234.2 ns one-way transport time will give the best s
2011,
23.
Abstract:
A fiber Raman amplifier (FRA) with dual-longitudinal-modes narrow-linewidth output is reported. Firstly, the dual-longitudinal-modes seed light with 1.4 GHz frequency spacing and a power proportion of 3∶1 is obtained by a home-made dual-longitudinal-modes narrow-linewidth fiber laser operating at 1 079.7 nm. The linewidth of each longitudinal mode is about 10 MHz. Then, the dual-longitudinal-modes seed light is amplified to a maximal power of 1.07 W with 1 031 nm pump source. The linewidth, frequency spacing and power proportion of the two longitudinal modes of the seed light have been maintained during the amplification.
A fiber Raman amplifier (FRA) with dual-longitudinal-modes narrow-linewidth output is reported. Firstly, the dual-longitudinal-modes seed light with 1.4 GHz frequency spacing and a power proportion of 3∶1 is obtained by a home-made dual-longitudinal-modes narrow-linewidth fiber laser operating at 1 079.7 nm. The linewidth of each longitudinal mode is about 10 MHz. Then, the dual-longitudinal-modes seed light is amplified to a maximal power of 1.07 W with 1 031 nm pump source. The linewidth, frequency spacing and power proportion of the two longitudinal modes of the seed light have been maintained during the amplification.
2011,
23.
Abstract:
Experimental results of SGIII prototype facility show that dynamic distortion exists in streak camera. Simulations indicate that, if input light intensity becomes too large, space charge effect in image converter tube shall affect the focus of the electron beam and decrease the magnification, which result in dynamic distortion. With increase of current intensity, the dynamic distortion becomes more evident. All above assist us better understand the electric-optic system of image converter tube, and provide ideas for further experimental diagnostic design.
Experimental results of SGIII prototype facility show that dynamic distortion exists in streak camera. Simulations indicate that, if input light intensity becomes too large, space charge effect in image converter tube shall affect the focus of the electron beam and decrease the magnification, which result in dynamic distortion. With increase of current intensity, the dynamic distortion becomes more evident. All above assist us better understand the electric-optic system of image converter tube, and provide ideas for further experimental diagnostic design.
