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RSS2009 Vol. 21, No. 01
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2009,
21.
Abstract:
The gas circulation system in TEA CO2 laser is very important. The parameters, the structure and the design of the system are analyzed. A symmetric structure is adopted and an axial blower and a plate-fin heat exchanger are selected. Using volume flux method, the gas velocity in the discharge zone is determined. The static pressure parameters of the fan are determined, taking into account of the additional resistance.The gas circulation system has an average gas velocity of 84.8 m/s, with inhomogeneity 4.2% longitudinally and 0.38% horizontally respectively. Under the condition of a discharge volume of 2.5×10-3 m3, a single pulse injection energy of 276 J, and a discharge pulse width at 150 ns, the system successfully achieves an even and steady glow discharge at a repetition rate of 400
The gas circulation system in TEA CO2 laser is very important. The parameters, the structure and the design of the system are analyzed. A symmetric structure is adopted and an axial blower and a plate-fin heat exchanger are selected. Using volume flux method, the gas velocity in the discharge zone is determined. The static pressure parameters of the fan are determined, taking into account of the additional resistance.The gas circulation system has an average gas velocity of 84.8 m/s, with inhomogeneity 4.2% longitudinally and 0.38% horizontally respectively. Under the condition of a discharge volume of 2.5×10-3 m3, a single pulse injection energy of 276 J, and a discharge pulse width at 150 ns, the system successfully achieves an even and steady glow discharge at a repetition rate of 400
2009,
21.
Abstract:
By analyzing the turbulent impinging jets of fluid jet polishing, the article established two physical models for the fluid jet polishing: vertical and oblique impinging jets models. Researched the characteristics of fluid jet polishing, found that the RNG k-e model is more suited for the polishing model compared with kinds of fluid models, because it can calculate the model with badly crooked streamlines accurately. Discrete model with finite volume method was gotten and the equations of fluid model with the second order upwind scheme were discretized. Then, the vertical and the oblique impinging jets models were simulated using SIMPLEC algorithm, and the continuous fluid field and the discrete phase grain field of fluid jet polishing model were derived, and the distributions of pressure
By analyzing the turbulent impinging jets of fluid jet polishing, the article established two physical models for the fluid jet polishing: vertical and oblique impinging jets models. Researched the characteristics of fluid jet polishing, found that the RNG k-e model is more suited for the polishing model compared with kinds of fluid models, because it can calculate the model with badly crooked streamlines accurately. Discrete model with finite volume method was gotten and the equations of fluid model with the second order upwind scheme were discretized. Then, the vertical and the oblique impinging jets models were simulated using SIMPLEC algorithm, and the continuous fluid field and the discrete phase grain field of fluid jet polishing model were derived, and the distributions of pressure
2009,
21.
Abstract:
The influences of the pump absorption coefficient on the temperature distribution along the fiber are analyzed for fiber lasers in theory based on the thermal conduction equations. It is shown that the temperature of the fiber with low absorption coefficient is comparatively low and the temperature distribution is very smooth, so the thermal damage can be effectively avoided. According to the analysis, an Yb-doped photonic crystal fiber with the pump absorption coefficient of 1.45 dB/m is used for the fiber laser in the experiment. 428.5 W single-mode continuous-wave output power is achieved at the pump power of 560 W. The slope efficiency of the system is 76.5% and the beam quality factor M2<1.2. The temperature of the fiber is measured at 25 cm from the fiber ends which are cooled with c
The influences of the pump absorption coefficient on the temperature distribution along the fiber are analyzed for fiber lasers in theory based on the thermal conduction equations. It is shown that the temperature of the fiber with low absorption coefficient is comparatively low and the temperature distribution is very smooth, so the thermal damage can be effectively avoided. According to the analysis, an Yb-doped photonic crystal fiber with the pump absorption coefficient of 1.45 dB/m is used for the fiber laser in the experiment. 428.5 W single-mode continuous-wave output power is achieved at the pump power of 560 W. The slope efficiency of the system is 76.5% and the beam quality factor M2<1.2. The temperature of the fiber is measured at 25 cm from the fiber ends which are cooled with c
2009,
21.
Abstract:
A continuous wave DF/HF chemical laser adopting TRIP technique has been numerically studied. According to the 3 dimensional flowfield with chemical reaction and without lasing, the simulation results show that the mixing enhancement of TRIP jets is obvious. The flow streams diffuse more quickly to the central line of the secondary nozzle (about 5 mm behind the nozzel exit plane), and the small signal gain is higher than that in the cases without TRIP jets. The mixing mechanism is analyzed to be stretching and distorting the interface between main and secondary streams. The TRIP jets creat weak vortices at the same time which dissipate soon after generation and affect the flowfield mildly.
A continuous wave DF/HF chemical laser adopting TRIP technique has been numerically studied. According to the 3 dimensional flowfield with chemical reaction and without lasing, the simulation results show that the mixing enhancement of TRIP jets is obvious. The flow streams diffuse more quickly to the central line of the secondary nozzle (about 5 mm behind the nozzel exit plane), and the small signal gain is higher than that in the cases without TRIP jets. The mixing mechanism is analyzed to be stretching and distorting the interface between main and secondary streams. The TRIP jets creat weak vortices at the same time which dissipate soon after generation and affect the flowfield mildly.
2009,
21.
Abstract:
A math model of beam quality control has been established and the beam quality evaluation parameter is presented. A duallenses beam quality optimized optical system has been designed for the small measuring probe. It not only keeps beam uniformity but also guarantees the refinement of laser beam, so that the positioning error caused by laser beam can be restrained effectively. Experiments show its feasibility. The beam quality controlled by the optimized system, whose RMS error is only 6.3 mm at its measuring range within positive and negative 5 mm, is superior to those controlled by the focalized and collimated system.
A math model of beam quality control has been established and the beam quality evaluation parameter is presented. A duallenses beam quality optimized optical system has been designed for the small measuring probe. It not only keeps beam uniformity but also guarantees the refinement of laser beam, so that the positioning error caused by laser beam can be restrained effectively. Experiments show its feasibility. The beam quality controlled by the optimized system, whose RMS error is only 6.3 mm at its measuring range within positive and negative 5 mm, is superior to those controlled by the focalized and collimated system.
2009,
21.
Abstract:
Structured background suppression is difficult for dim and small targets detection.bilateral filtering could get information of image geometric, photometric and local structure similarites, and is non-iterative, local and simple, a background suppression algorithm based on bilateral filtering wa presented to solve the problem, and local gradient statistics was introduced to suppress background details and enhance target information for improving entire image contrast and signal to noise ratio (SNR). When compared with wavelet filtering algorithm through subject inspection and value index, several groups of experimental results demonstrate that the presented algorithm can suppress complicated background in the dim and small target image effectively．
Structured background suppression is difficult for dim and small targets detection.bilateral filtering could get information of image geometric, photometric and local structure similarites, and is non-iterative, local and simple, a background suppression algorithm based on bilateral filtering wa presented to solve the problem, and local gradient statistics was introduced to suppress background details and enhance target information for improving entire image contrast and signal to noise ratio (SNR). When compared with wavelet filtering algorithm through subject inspection and value index, several groups of experimental results demonstrate that the presented algorithm can suppress complicated background in the dim and small target image effectively．
Frequency-response characteristics of dispersed support for the surface of large-aperture components
2009,
21.
Abstract:
In the case of the multi-point support for a thin mirror with a diameter of 600 mm, the paper studied the frequency-response of components’ surface, which was influenced by different support schemes. A one-dimensional beam model of dispersed support units had been established. The feasibility of the peak-to-valley(P-V), RMS values as support optimization objective functions was discussed. The result is that the values of P-V, RMS can not be the correct evaluation of the surface in the frequency domain response. Then, the frequency-response characteristics influenced by the interval and size of support units were analyzed. According to the results, the ideal support scheme is: the diameters of the center and lateral support units are 10 mm; the support unit interval is 125 mm.
In the case of the multi-point support for a thin mirror with a diameter of 600 mm, the paper studied the frequency-response of components’ surface, which was influenced by different support schemes. A one-dimensional beam model of dispersed support units had been established. The feasibility of the peak-to-valley(P-V), RMS values as support optimization objective functions was discussed. The result is that the values of P-V, RMS can not be the correct evaluation of the surface in the frequency domain response. Then, the frequency-response characteristics influenced by the interval and size of support units were analyzed. According to the results, the ideal support scheme is: the diameters of the center and lateral support units are 10 mm; the support unit interval is 125 mm.
2009,
21.
Abstract:
Based on the propagation model for the wideband ultra-short pulse, the coupled equations which determine the interaction process among pump, idle and signal pulses in the LBO crystal are studied by the fourth-order Runge-Kutta methods. The simulation results are as follows: the synchronization time jitter induces the pedestal generation, which possesses plentiful energy and can not be removed in the compression stage, therefore, the pulse duration stretches and the contrast ratio of the femto-second pulses decreases seriously, for example, the prepulse stretches from 0.2 ps to 0.7 ps when the synchronization time jitter changed from 0 to 150 ps; Using the longer duration and smoother shape pump pulse can restrain the time jitter effectively, and choosing suitable length of the nonlinear cr
Based on the propagation model for the wideband ultra-short pulse, the coupled equations which determine the interaction process among pump, idle and signal pulses in the LBO crystal are studied by the fourth-order Runge-Kutta methods. The simulation results are as follows: the synchronization time jitter induces the pedestal generation, which possesses plentiful energy and can not be removed in the compression stage, therefore, the pulse duration stretches and the contrast ratio of the femto-second pulses decreases seriously, for example, the prepulse stretches from 0.2 ps to 0.7 ps when the synchronization time jitter changed from 0 to 150 ps; Using the longer duration and smoother shape pump pulse can restrain the time jitter effectively, and choosing suitable length of the nonlinear cr
2009,
21.
Abstract:
A high-Coulomb two-electrode spark gap switch was developed. Its static characteristic was studied and the fitting formula for its self-breakdown probability was derived. It is found that the self-breakdown voltage increases linearly with the working gas pressure, and the voltage becomes more dispersive as the pressure increases. The comparison results between numerical simulation and experiments show that, the self-breakdown probability agrees well with the Welbull relationship with two parameters. This work could be a reference for the selection of switch working pressure and inflated-gas pressure, which meets the stability demand of the power conditioning system.
A high-Coulomb two-electrode spark gap switch was developed. Its static characteristic was studied and the fitting formula for its self-breakdown probability was derived. It is found that the self-breakdown voltage increases linearly with the working gas pressure, and the voltage becomes more dispersive as the pressure increases. The comparison results between numerical simulation and experiments show that, the self-breakdown probability agrees well with the Welbull relationship with two parameters. This work could be a reference for the selection of switch working pressure and inflated-gas pressure, which meets the stability demand of the power conditioning system.
2009,
21.
Abstract:
In order to enhance the returned photon numbers in lunar laser ranging, adaptive optics is considered to be applied to the 1.2 m telescope of Yunnan observatory to correct the telescope tracking error and the laser beam jitter caused by the turbulence. According to the low contrast extended character of the lunar surface, atmospheric tip-tilts were computed with cross correlation and absolute difference algorithms based on the collected lunar surface images. Long exposure images of the lunar surface were simulated with atmospheric tip-tilts being and not being compensated. The contrast of the lunar surface images were enhanced when the atmospheric tip-tilts were compensated. It is revealed that the absolute difference algorithm is better in computing the atmospheric tip-tilt in lunar laser
In order to enhance the returned photon numbers in lunar laser ranging, adaptive optics is considered to be applied to the 1.2 m telescope of Yunnan observatory to correct the telescope tracking error and the laser beam jitter caused by the turbulence. According to the low contrast extended character of the lunar surface, atmospheric tip-tilts were computed with cross correlation and absolute difference algorithms based on the collected lunar surface images. Long exposure images of the lunar surface were simulated with atmospheric tip-tilts being and not being compensated. The contrast of the lunar surface images were enhanced when the atmospheric tip-tilts were compensated. It is revealed that the absolute difference algorithm is better in computing the atmospheric tip-tilt in lunar laser
2009,
21.
Abstract:
The optical gradient force patterns in focal region of radially polarized beams is investigated. The pure phase plate consists of three concentric zones: center circle zone, inner annular zone and outer annular zone. And the phase variance of annular zone is adjustable. The tunable phase plate can be implemented through liquid crystal spatial light modulator, which can conveniently alter the phase shift and polarization rotation angle of each section of the incident laser beam in the control of computer. Numerical simulations show that the evolution of the focal shape is evident by changing polarization rotation angle of each section portion of the vector beam. Consequently, the optical gradient force patterns will change and some interesting optical trap patterns may occur, which shows th
The optical gradient force patterns in focal region of radially polarized beams is investigated. The pure phase plate consists of three concentric zones: center circle zone, inner annular zone and outer annular zone. And the phase variance of annular zone is adjustable. The tunable phase plate can be implemented through liquid crystal spatial light modulator, which can conveniently alter the phase shift and polarization rotation angle of each section of the incident laser beam in the control of computer. Numerical simulations show that the evolution of the focal shape is evident by changing polarization rotation angle of each section portion of the vector beam. Consequently, the optical gradient force patterns will change and some interesting optical trap patterns may occur, which shows th
2009,
21.
Abstract:
A nanopoporous copper was synthesized by free corrosion dealloying in the 0.1 mol/L HCl solution. Micro-structure and composition of the sample before and after dealloying were characterized by a scanning electron microscope and an energy dispersive analysis of X-ray. There was selective dissolution of manganese from Mn-Cu alloy in the 0.1 mol/L HCl solution, and the nanoporous copper with a uniform porous structure in three-dimensional network, an average ligament size of 53 nm and an average pore size of 140 nm was prepared.
A nanopoporous copper was synthesized by free corrosion dealloying in the 0.1 mol/L HCl solution. Micro-structure and composition of the sample before and after dealloying were characterized by a scanning electron microscope and an energy dispersive analysis of X-ray. There was selective dissolution of manganese from Mn-Cu alloy in the 0.1 mol/L HCl solution, and the nanoporous copper with a uniform porous structure in three-dimensional network, an average ligament size of 53 nm and an average pore size of 140 nm was prepared.
2009,
21.
Abstract:
Based on the fundamental theory of improving structure stability, with the finite-element method (FEM), the research on the structure stability of the superstructure was performed. The results indicates that the third modal shape of the superstructure is the most important factor in the stability of the large aperture mirror, and the the weak link is the frame. With the stiffener with optimized position used between the frame and the concrete-filled steel tubular structure adopted for the frame, etc, the stability of the superstructure could be improved effectively. At last, the stability scheme of the superstructure was proposed which could satisfy the stability requirement of large aperture mirrors.
Based on the fundamental theory of improving structure stability, with the finite-element method (FEM), the research on the structure stability of the superstructure was performed. The results indicates that the third modal shape of the superstructure is the most important factor in the stability of the large aperture mirror, and the the weak link is the frame. With the stiffener with optimized position used between the frame and the concrete-filled steel tubular structure adopted for the frame, etc, the stability of the superstructure could be improved effectively. At last, the stability scheme of the superstructure was proposed which could satisfy the stability requirement of large aperture mirrors.
2009,
21.
Abstract:
A planar cryotarget system for the inertial-confinement-fusion(ICF) experiments was set up with the low-temperature resource provided by a Gifford-McMahon cryocooler. The cooling power and the cooling rate of the planar cryotarget system were examined as functions of temperature. This system can reach a lowest temperature of 10 K, and its cooling powers are 3 W at 14 K and 6.5 W at 18.6 K. The cooling rate can be artificially adjusted. Using this system, the argon and hydrogen vapors at 300 K are condensed to liquid or solid in a cylindrical target cell. With the help of Mach-Zehnder interference, the planar cryotarget system is also applied to reveal that the ICF capsules are structurally deformed with decreasing the temperatures．
A planar cryotarget system for the inertial-confinement-fusion(ICF) experiments was set up with the low-temperature resource provided by a Gifford-McMahon cryocooler. The cooling power and the cooling rate of the planar cryotarget system were examined as functions of temperature. This system can reach a lowest temperature of 10 K, and its cooling powers are 3 W at 14 K and 6.5 W at 18.6 K. The cooling rate can be artificially adjusted. Using this system, the argon and hydrogen vapors at 300 K are condensed to liquid or solid in a cylindrical target cell. With the help of Mach-Zehnder interference, the planar cryotarget system is also applied to reveal that the ICF capsules are structurally deformed with decreasing the temperatures．
2009,
21.
Abstract:
Nano-crystalline beryllium-Coppery BeCu alloy is prepared by the melt-spin method. It was characterized by X-ray diffraction,scanning electron microscope and electron spectroscopy,and its structure was compared with of the original state of the alloy CuBe. Result shows that:reasonable rapid solidification technology can decrease grain size of the CuBe alloy to 30 nm around, changing the grain morphology of the alloy; something like CuBe intermetallic compounds can be found. ln Be-doped Cu, a large number of small dispersion of the second phase particles appear in the rapid solidification alloy the solid solubility of the alloy is eahanced, and eutectoid reaction happen．
Nano-crystalline beryllium-Coppery BeCu alloy is prepared by the melt-spin method. It was characterized by X-ray diffraction,scanning electron microscope and electron spectroscopy,and its structure was compared with of the original state of the alloy CuBe. Result shows that:reasonable rapid solidification technology can decrease grain size of the CuBe alloy to 30 nm around, changing the grain morphology of the alloy; something like CuBe intermetallic compounds can be found. ln Be-doped Cu, a large number of small dispersion of the second phase particles appear in the rapid solidification alloy the solid solubility of the alloy is eahanced, and eutectoid reaction happen．
2009,
21.
Abstract:
The temporal and spectral characteristic of two stacked chirped pulses are given based on the principle and model of the chirped pulse stacking. And the temporal modulation, spectral modulation and the nonlinear frequency chirp are analyzed. Some characteristics of the stacked pulse amplification are studied by evaluating the nonlinear Schrdinger equation. The amplification result changes with the modified chirped parameters, and the frequency chirp of the output pulse is also changed greatly. The result shows that self-phase modulation plays a main role in changing the spectral and frequency chirp of the amplified stacked pulse.
The temporal and spectral characteristic of two stacked chirped pulses are given based on the principle and model of the chirped pulse stacking. And the temporal modulation, spectral modulation and the nonlinear frequency chirp are analyzed. Some characteristics of the stacked pulse amplification are studied by evaluating the nonlinear Schrdinger equation. The amplification result changes with the modified chirped parameters, and the frequency chirp of the output pulse is also changed greatly. The result shows that self-phase modulation plays a main role in changing the spectral and frequency chirp of the amplified stacked pulse.
2009,
21.
Abstract:
Low-density hydrophobic silica aerogels were produced by modification of conventional silica aerogels via substitution of －OH groups by trimethylsilyls. IR spectra and thermogravimeturic anglyses were to characterize the aerogels before and after modification, And the diameter changes of modified and unmodified aerogel micro cylinders were tracked using a measuring microscope. The results show that the hydrophobic silica aerogels possess much higher stability than hydrophilic ones due to the diminishment of －OH groups and the radial shrinkage ratio of cylinder samples decreases dramatically from 30% down to 3% after modification．
Low-density hydrophobic silica aerogels were produced by modification of conventional silica aerogels via substitution of －OH groups by trimethylsilyls. IR spectra and thermogravimeturic anglyses were to characterize the aerogels before and after modification, And the diameter changes of modified and unmodified aerogel micro cylinders were tracked using a measuring microscope. The results show that the hydrophobic silica aerogels possess much higher stability than hydrophilic ones due to the diminishment of －OH groups and the radial shrinkage ratio of cylinder samples decreases dramatically from 30% down to 3% after modification．
2009,
21.
Abstract:
The gas-filled hohlraum targets is one of the most important targets in the inertial confinement fusion experiments. There are three ways to fill the hohlraum with necessary gases: filling gas at the same time of or before the shot, or before the experiment. This paper focused on the fabrication of gas-filled targets without gas source. Based on the design of the targets assembly, a seris of gas-filled targets were finished, whose hohlraum materials were Au, plastic and glass. Experiments show that the half life time of the target is no less than 341 hours for Kr-filled glass hohlraum, and the amount of leaded gas is no more than 2% of the total gas in the target within 3 h. Remote-place shooting could be realized by keeping the finished target in a high pressure gas-retention tank during
The gas-filled hohlraum targets is one of the most important targets in the inertial confinement fusion experiments. There are three ways to fill the hohlraum with necessary gases: filling gas at the same time of or before the shot, or before the experiment. This paper focused on the fabrication of gas-filled targets without gas source. Based on the design of the targets assembly, a seris of gas-filled targets were finished, whose hohlraum materials were Au, plastic and glass. Experiments show that the half life time of the target is no less than 341 hours for Kr-filled glass hohlraum, and the amount of leaded gas is no more than 2% of the total gas in the target within 3 h. Remote-place shooting could be realized by keeping the finished target in a high pressure gas-retention tank during
2009,
21.
Abstract:
A procedure of synthesis of organic/inorganic hybrid wetgels derived from methacryloxypropyltrimethoxysilane based silsesquioxane(MPMS-SSO) by ultra-violet ray(UV) cure was demonstrated. Hybrid aerogels were obtained through CO2 supercritical fluid drying process. The as-synthesized aerogels were characterized by field-emission scanning electron microscopy(SEM), high resolution transmission electron microscopy(TEM), Brunauer-EmmettTeler(BET). The field-emission SEM micrograph shows that, the aerogels are made up of 3-D pearlnecklace like tangling networks and the diameters of the backbone particles are of 20~30 nm. The high resolution TEM micrograph indicates that there are some holes with diameters about 5~10 nm in backbone. The BET results reveal that the aerogel specific surface are
A procedure of synthesis of organic/inorganic hybrid wetgels derived from methacryloxypropyltrimethoxysilane based silsesquioxane(MPMS-SSO) by ultra-violet ray(UV) cure was demonstrated. Hybrid aerogels were obtained through CO2 supercritical fluid drying process. The as-synthesized aerogels were characterized by field-emission scanning electron microscopy(SEM), high resolution transmission electron microscopy(TEM), Brunauer-EmmettTeler(BET). The field-emission SEM micrograph shows that, the aerogels are made up of 3-D pearlnecklace like tangling networks and the diameters of the backbone particles are of 20~30 nm. The high resolution TEM micrograph indicates that there are some holes with diameters about 5~10 nm in backbone. The BET results reveal that the aerogel specific surface are
2009,
21.
Abstract:
A cyclotron superradiance(SR) which combines the merits of cyclotron and SR has a potential advantage in developing superradiant HPM sources operating at millimeter and submillimeter wavebands. The working characteristics of the cyclotron SR was analyzed using 3D PIC simulation,based on which the working parameters were optimized. A square relation between the beam pulse width and the peak power was given, which proved that the system worked in the SR regime. Preliminary experiment shows that when the beam parameters were 210 kV, 250 A and the guiding magnetic field was 1.73 T, microwave pulses were acquired, with the peak power of 6 MW, the peak power conversion efficiency of 11.4%, the frequency of 37.2 GHz and TE01 output mode. The results are in accordance with the simulation ones.
A cyclotron superradiance(SR) which combines the merits of cyclotron and SR has a potential advantage in developing superradiant HPM sources operating at millimeter and submillimeter wavebands. The working characteristics of the cyclotron SR was analyzed using 3D PIC simulation,based on which the working parameters were optimized. A square relation between the beam pulse width and the peak power was given, which proved that the system worked in the SR regime. Preliminary experiment shows that when the beam parameters were 210 kV, 250 A and the guiding magnetic field was 1.73 T, microwave pulses were acquired, with the peak power of 6 MW, the peak power conversion efficiency of 11.4%, the frequency of 37.2 GHz and TE01 output mode. The results are in accordance with the simulation ones.
2009,
21.
Abstract:
Three-dimensional fluid equations, steady-state differential equation and reasonable boundary conditions of cylindrical hollow cathode are presented, some parameters have been calculated such as particle density distribution, electron energy and the distribution of electric field. Under the pressure of 6 666.1~13 332.2 Pa and the voltage of 150~300 V discharge, it is found that reducing the dimension of the cathode can enhance the negative glow space, and increasing pressure will enhance the electron density. The simulated results show that the discharge parameters are strongly dependent on voltage and pressure of the microhollow cathode.
Three-dimensional fluid equations, steady-state differential equation and reasonable boundary conditions of cylindrical hollow cathode are presented, some parameters have been calculated such as particle density distribution, electron energy and the distribution of electric field. Under the pressure of 6 666.1~13 332.2 Pa and the voltage of 150~300 V discharge, it is found that reducing the dimension of the cathode can enhance the negative glow space, and increasing pressure will enhance the electron density. The simulated results show that the discharge parameters are strongly dependent on voltage and pressure of the microhollow cathode.
2009,
21.
Abstract:
The microwave discharge experiments of dielectric window were performed in vacuum under X-band HPM with the frequency of 9.4 GHz and the power of 1 GW. Several typical dielectric window materials, i.e., PTFE, PMMA, LDPE and HDPE, were employed, and the influence of different surface treatments as notching and polishing was investigated. After microwave breakdown experiments, the surface morphology of dielectric samples were analyzed with the macroscopic and microcosmic view. It was found that there were obvious single-surface tree-like breakage phenomena occurred along the direction of microwave electric field, and the surface destroy status was significantly affected by the different surface treatment. It is considered that the tree-like depredation channels are closely related to the app
The microwave discharge experiments of dielectric window were performed in vacuum under X-band HPM with the frequency of 9.4 GHz and the power of 1 GW. Several typical dielectric window materials, i.e., PTFE, PMMA, LDPE and HDPE, were employed, and the influence of different surface treatments as notching and polishing was investigated. After microwave breakdown experiments, the surface morphology of dielectric samples were analyzed with the macroscopic and microcosmic view. It was found that there were obvious single-surface tree-like breakage phenomena occurred along the direction of microwave electric field, and the surface destroy status was significantly affected by the different surface treatment. It is considered that the tree-like depredation channels are closely related to the app
2009,
21.
Abstract:
Physical model for the X-band dual-frequency coaxial relativistic backward wave oscillator(RBWO) was suggested. The dispersion equation and the dispersion properties of the coaxial SWS were numerically investigated. The properties of dual-frequency RBWO were investigated and optimized with electromagnetic simulation method. The optimized parameters are as follows: corrugation period numbers are 10 and 4, corrugation periods are 0.50 cm and 0.73 cm, and corrugation amplitudes are 0.13 cm and 0.21 cm for the first and the second sections respectively. The average radius of slow wave structure is 2.9 cm. The results show that steady dual frequencies microwave power outputs are generated with operating voltage of 510 kV, beam current of 9.4 kA and external guiding magnetic field intensity of 0
Physical model for the X-band dual-frequency coaxial relativistic backward wave oscillator(RBWO) was suggested. The dispersion equation and the dispersion properties of the coaxial SWS were numerically investigated. The properties of dual-frequency RBWO were investigated and optimized with electromagnetic simulation method. The optimized parameters are as follows: corrugation period numbers are 10 and 4, corrugation periods are 0.50 cm and 0.73 cm, and corrugation amplitudes are 0.13 cm and 0.21 cm for the first and the second sections respectively. The average radius of slow wave structure is 2.9 cm. The results show that steady dual frequencies microwave power outputs are generated with operating voltage of 510 kV, beam current of 9.4 kA and external guiding magnetic field intensity of 0
2009,
21.
Abstract:
With the purpose of evaluating the ability for a metallic rectangular enclosure with an array of circular apertures and a printed circuit board(PCB) against the external electromagnetic interference, a waveguide equivalent circuit model was established, the analytical formulation of shielding effectiveness(SE) was derived from the equivalent circuit, and a simple and high-effective approach was proposed. In the case of the enclosure without PCB, the approach is identified with that in the reference. With respect to the SE of the PCB loaded enclosure, the calculated results using the present approach are in well agreement with those obtained by commercially available numerical tool CST. The results show that the comparison between electric field orientations parallel and perpendicular to th
With the purpose of evaluating the ability for a metallic rectangular enclosure with an array of circular apertures and a printed circuit board(PCB) against the external electromagnetic interference, a waveguide equivalent circuit model was established, the analytical formulation of shielding effectiveness(SE) was derived from the equivalent circuit, and a simple and high-effective approach was proposed. In the case of the enclosure without PCB, the approach is identified with that in the reference. With respect to the SE of the PCB loaded enclosure, the calculated results using the present approach are in well agreement with those obtained by commercially available numerical tool CST. The results show that the comparison between electric field orientations parallel and perpendicular to th
2009,
21.
Abstract:
The propagation attenuation characteristics of electromagnetic wave penetrating different media are analyzed applying the theory of the electromagnetic plane wave and Fresnel formulas. They are numerically compared by adopting different parameters such as polarization, incident angle, dielectric permittivity, conductivity, tangent of dielectric loss angle and frequency. The total transmission loss versus frequency is simulated for often-used walls such as common concrete wall, 37 brick wall, 24 brick wall, hollow plasterboard, cement board with polystyrene, wood block and organic glass. The attenuation characteristics of new walls and hollow clay brick walls are analyzed. The simulation results are also compared with laboratory measurements and that from referenced literatures, which shows
The propagation attenuation characteristics of electromagnetic wave penetrating different media are analyzed applying the theory of the electromagnetic plane wave and Fresnel formulas. They are numerically compared by adopting different parameters such as polarization, incident angle, dielectric permittivity, conductivity, tangent of dielectric loss angle and frequency. The total transmission loss versus frequency is simulated for often-used walls such as common concrete wall, 37 brick wall, 24 brick wall, hollow plasterboard, cement board with polystyrene, wood block and organic glass. The attenuation characteristics of new walls and hollow clay brick walls are analyzed. The simulation results are also compared with laboratory measurements and that from referenced literatures, which shows
2009,
21.
Abstract:
With ion beam assisted reactive deposition, hafnia films were prepared at different bias voltages of the APS ion source in the range from 50 V to 140 V on silicon disks and ultraviolet quartz glasses (JGS1) in the Leybold APS 1 104 coating system, where metallic hafnium was used as the starting material. The Lambda 900 spectrophotometer was employed to measure the transmittance spectra of the deposited films. The composition and microstructure were measured with XPS and XRD measurements. AFM was used to characterize the surface morphology and roughness. It is shown that the short ultraviolet optical loss will decrease with the reduction of the bias voltage of the APS ion source when it changes between the two ranges of 140~120 V and 90~ 50 V, but it is not sensitive to the bias voltage in
With ion beam assisted reactive deposition, hafnia films were prepared at different bias voltages of the APS ion source in the range from 50 V to 140 V on silicon disks and ultraviolet quartz glasses (JGS1) in the Leybold APS 1 104 coating system, where metallic hafnium was used as the starting material. The Lambda 900 spectrophotometer was employed to measure the transmittance spectra of the deposited films. The composition and microstructure were measured with XPS and XRD measurements. AFM was used to characterize the surface morphology and roughness. It is shown that the short ultraviolet optical loss will decrease with the reduction of the bias voltage of the APS ion source when it changes between the two ranges of 140~120 V and 90~ 50 V, but it is not sensitive to the bias voltage in
2009,
21.
Abstract:
The Rayleigh scattering method is widely adopted in measuring cluster size. In general, it is considered that the intensity of scattering corresponds to the cluster size directly. However, this paper deduces that the intensity is not only related to cluster size, but also to gas density and binding probability. It suggests that gas density should be taken into account in analyzing the measurement results of Rayleigh scattering method. Furthermore, the method is applied in measuring the size distribution of argon cluster along the axis of nozzle. It is found that the cluster size doesn’t vary linearly along the nozzle axis, whereas it reaches maximum at a certain position which depends on some parameters including the background pressure．
The Rayleigh scattering method is widely adopted in measuring cluster size. In general, it is considered that the intensity of scattering corresponds to the cluster size directly. However, this paper deduces that the intensity is not only related to cluster size, but also to gas density and binding probability. It suggests that gas density should be taken into account in analyzing the measurement results of Rayleigh scattering method. Furthermore, the method is applied in measuring the size distribution of argon cluster along the axis of nozzle. It is found that the cluster size doesn’t vary linearly along the nozzle axis, whereas it reaches maximum at a certain position which depends on some parameters including the background pressure．
2009,
21.
Abstract:
In order to reduce the influence of scatter for radiography and increase the precision of the reconstructed object, the double-axis radiography system is proposed on the basis of using specific collimators. The double-axis radiography system has one collimator on each radiography axis, and the two collimators have different collimating angles. with such system the simulation radiography is carried out. The results show that the scatter from one axis to the other axis in radiography is large, and it is mainly from the front window. And it is reduced greatly by putting the lead block in the direction from front window to the detector on the other axis. The collimated angles for the FTO double-axis radiography is 2.24° and 1.15° according to the combining information and requirement of scat
In order to reduce the influence of scatter for radiography and increase the precision of the reconstructed object, the double-axis radiography system is proposed on the basis of using specific collimators. The double-axis radiography system has one collimator on each radiography axis, and the two collimators have different collimating angles. with such system the simulation radiography is carried out. The results show that the scatter from one axis to the other axis in radiography is large, and it is mainly from the front window. And it is reduced greatly by putting the lead block in the direction from front window to the detector on the other axis. The collimated angles for the FTO double-axis radiography is 2.24° and 1.15° according to the combining information and requirement of scat
2009,
21.
Abstract:
Properties for metamaterial electromagnetic cloak with elliptical volume under TE wave irradiation are analyzed using finite element method (FEM). Computation results show that 0.5% deviation of the permittivity, permeability and conductivity from the parameters of the perfect cloak affects the electricfield distributions in the outer region of the cloak. The perfect cloak can exclude the electromagnetic fields from the interior region without perturbing exterior fields and therefore the different objects in it can be effectively hidden from to the outer regions．
Properties for metamaterial electromagnetic cloak with elliptical volume under TE wave irradiation are analyzed using finite element method (FEM). Computation results show that 0.5% deviation of the permittivity, permeability and conductivity from the parameters of the perfect cloak affects the electricfield distributions in the outer region of the cloak. The perfect cloak can exclude the electromagnetic fields from the interior region without perturbing exterior fields and therefore the different objects in it can be effectively hidden from to the outer regions．
2009,
21.
Abstract:
In order to obtain the most suitable optical fields to trap the Rayleigh particles, the expression of the minimum particle radius for Bessel beams capture was deduct through the electromagnetism model, and transverse forces and potential depths were calculated for Rayleigh particles in Bessel and Gaussian beams respectively. The results indicate that Rayleigh particles can be stably trapped under an incident power of 4 W only at the maximum of the optical fields, and the positions of trapping particles in the optical fields are the maximum and the secondary maximum for an incident power of 6 W. With similar laser parameters, Gaussian beams can not overtake the influences of Brownian motion to capture the Rayleigh-particles as Bessel beams do. Therefore, Bessel beams are better to trap the
In order to obtain the most suitable optical fields to trap the Rayleigh particles, the expression of the minimum particle radius for Bessel beams capture was deduct through the electromagnetism model, and transverse forces and potential depths were calculated for Rayleigh particles in Bessel and Gaussian beams respectively. The results indicate that Rayleigh particles can be stably trapped under an incident power of 4 W only at the maximum of the optical fields, and the positions of trapping particles in the optical fields are the maximum and the secondary maximum for an incident power of 6 W. With similar laser parameters, Gaussian beams can not overtake the influences of Brownian motion to capture the Rayleigh-particles as Bessel beams do. Therefore, Bessel beams are better to trap the
Polarized bidirectional reflectance distribution function by subsurface defects of optical component
2009,
21.
Abstract:
Polarized bidirectional reflectance distribution function(PBRDF) of light scattered by subsurface defect(SSD) was derived on the foundation of Jones scattering matrix by use of right handed basis set. Four kinds of PBRDF changing with azimuth angle were calculated and compared at different incident angles, and three-dimensional BRDFpp which indicates p polarized scattered light due to p polarized incident light were obtained at different incident angles. The results show that BRDFpp by SSD depends strongly on incident angle, scattering angle and azimuth angle. The azimuth angle of minimal BRDFpp decreases with the increase of incident angle.
Polarized bidirectional reflectance distribution function(PBRDF) of light scattered by subsurface defect(SSD) was derived on the foundation of Jones scattering matrix by use of right handed basis set. Four kinds of PBRDF changing with azimuth angle were calculated and compared at different incident angles, and three-dimensional BRDFpp which indicates p polarized scattered light due to p polarized incident light were obtained at different incident angles. The results show that BRDFpp by SSD depends strongly on incident angle, scattering angle and azimuth angle. The azimuth angle of minimal BRDFpp decreases with the increase of incident angle.
2009,
21.
Abstract:
Based on the formula of range and that of real efficient secondary electron yield from metal, the relation among energy exponent, incident energy and the real efficient secondary electron yield at high incident electron energy was derived. Based on the relation between the real efficient secondary electron yield and secondary electron yield at high incident electron energy of metal, the relation among the energy exponent, incident energy and the secondary electron yield at high incident electron energy was derived. The energy exponents (n) of the primary electrons hitting on gold and silver is computed with experimental results. The experimental results also validate the relation among the incident energy,energy exponent and the secondary electron yield at high incident electron energy for
Based on the formula of range and that of real efficient secondary electron yield from metal, the relation among energy exponent, incident energy and the real efficient secondary electron yield at high incident electron energy was derived. Based on the relation between the real efficient secondary electron yield and secondary electron yield at high incident electron energy of metal, the relation among the energy exponent, incident energy and the secondary electron yield at high incident electron energy was derived. The energy exponents (n) of the primary electrons hitting on gold and silver is computed with experimental results. The experimental results also validate the relation among the incident energy,energy exponent and the secondary electron yield at high incident electron energy for
2009,
21.
Abstract:
The water switches in induction voltage adder are designed. The electrode of output switch is plate to annular and the electrode of peaking switch is annular. Selfbreak characters of water switches under 300 ns pulsed voltage are studied. The spacing of switches is determined under different Marx charging voltage as well. The experimental result indicates that the switches are reliable with low jitters. The peaking switch cooperates well with the main switch, which can sharp the main pulse and reduce the amplitude of prepulse. The selfbreak experimental data of output switch accords well with Martin’s formula．
The water switches in induction voltage adder are designed. The electrode of output switch is plate to annular and the electrode of peaking switch is annular. Selfbreak characters of water switches under 300 ns pulsed voltage are studied. The spacing of switches is determined under different Marx charging voltage as well. The experimental result indicates that the switches are reliable with low jitters. The peaking switch cooperates well with the main switch, which can sharp the main pulse and reduce the amplitude of prepulse. The selfbreak experimental data of output switch accords well with Martin’s formula．
2009,
21.
Abstract:
A low jitter 6 MV/300 kJ Marx generator has been developed for the primary test stand(PTS) which will be built for Z-pinch studies at Institute of Fluid Physics, CAEP. The generator is designed as a leading triggering circuit based on the S-type structure. It is composed of sixty 100 kV/1 mF capacitors and thirty 200 kV low jitter ring rail field distortion switches developed by Institute of Fluid Physics. The experimental results reveal that the serial capacitance of the Marx generator is 16.7 nF, the serial inductance is 13.5 mH and the serial resistance is 3.2 Ω. As the charging voltage of the capacitors is 80 kV, the working storage energy of the Marx generator is 192 kJ, the measured output voltage is 4.3 MV, the erection time is about 175 ns and its RMS jitter is less than 7.0 ns. T
A low jitter 6 MV/300 kJ Marx generator has been developed for the primary test stand(PTS) which will be built for Z-pinch studies at Institute of Fluid Physics, CAEP. The generator is designed as a leading triggering circuit based on the S-type structure. It is composed of sixty 100 kV/1 mF capacitors and thirty 200 kV low jitter ring rail field distortion switches developed by Institute of Fluid Physics. The experimental results reveal that the serial capacitance of the Marx generator is 16.7 nF, the serial inductance is 13.5 mH and the serial resistance is 3.2 Ω. As the charging voltage of the capacitors is 80 kV, the working storage energy of the Marx generator is 192 kJ, the measured output voltage is 4.3 MV, the erection time is about 175 ns and its RMS jitter is less than 7.0 ns. T
2009,
21.
Abstract:
A 10-stage wave erection Marx generator was modified from resistively isolated configuration to inductively isolated configuration for the investigation on its repetitive operation characteristics. Through a single shot experiment powered by a constant voltage charging device, it is found that when discharging in N2, the generator has the same output waveforms for both isolation configurations; but when discharging in SF6, it has a faster rise time for the resistively isolated configuration than that for the inductively isolated configuration, and the reason for this phenomenon was analyzed preliminarily. By enhancing the charging current, the pulsant problem for repetitive charging with constant current charging device was solved, and then, repetitive operation experiments were carried ou
A 10-stage wave erection Marx generator was modified from resistively isolated configuration to inductively isolated configuration for the investigation on its repetitive operation characteristics. Through a single shot experiment powered by a constant voltage charging device, it is found that when discharging in N2, the generator has the same output waveforms for both isolation configurations; but when discharging in SF6, it has a faster rise time for the resistively isolated configuration than that for the inductively isolated configuration, and the reason for this phenomenon was analyzed preliminarily. By enhancing the charging current, the pulsant problem for repetitive charging with constant current charging device was solved, and then, repetitive operation experiments were carried ou
