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RSS2008 Vol. 20, No. 04
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2008,
20.
Abstract:
A precise simulation the focus anisoplanatism error of Yunnan observatory 1.2 m 61-element laser guide star adaptive optics system, which caused by laser beacon at a finite range travels a different path than does the light from natural star at a infinite range. This error can be eliminated by use of laser guide stars. However, there are two sources of error limit multiple beacon adaptive optical system, beacon position measurement error and conic tilt error. Analysis the two errors when project two to five laser guide stars. The result showed that with the increase of high and number of laser beam, especially the focus anisoplanatism of Na laser guide stars could reduced to 1 rad2.
A precise simulation the focus anisoplanatism error of Yunnan observatory 1.2 m 61-element laser guide star adaptive optics system, which caused by laser beacon at a finite range travels a different path than does the light from natural star at a infinite range. This error can be eliminated by use of laser guide stars. However, there are two sources of error limit multiple beacon adaptive optical system, beacon position measurement error and conic tilt error. Analysis the two errors when project two to five laser guide stars. The result showed that with the increase of high and number of laser beam, especially the focus anisoplanatism of Na laser guide stars could reduced to 1 rad2.
2008,
20.
Abstract:
Polarimetric parameters and polarization imaging of camouflage net were measured to study the effect of polarization remote sensing on the camoulflage targets.It is found that the polarization degree of camouflage net was greatly influenced by the condition of detection and characteristics of materials, such as reflectance, refractive index and roughness of surface. The interaction between incident light and camouflage coating can be divided into two parts, surface scattering and volume scattering. Surface scattering act as a function of polarization and volume scattering act as a function of depolarization.The polarimetric characteristics of camouflage targets were different from natural background. Compared with traditional remote sensing, polarization remote sensing can find the camoufl
Polarimetric parameters and polarization imaging of camouflage net were measured to study the effect of polarization remote sensing on the camoulflage targets.It is found that the polarization degree of camouflage net was greatly influenced by the condition of detection and characteristics of materials, such as reflectance, refractive index and roughness of surface. The interaction between incident light and camouflage coating can be divided into two parts, surface scattering and volume scattering. Surface scattering act as a function of polarization and volume scattering act as a function of depolarization.The polarimetric characteristics of camouflage targets were different from natural background. Compared with traditional remote sensing, polarization remote sensing can find the camoufl
2008,
20.
Abstract:
In this paper, based on the iterative method of finite-difference, 3-D instantaneoos and stable temperature distribution of square slice in the Nd:YAG disk laser under super-Gaussian pump light are calculated. Using the thermal balance differential equation and boundary condition of thermal elasticity body, 3-D thermal stress distribution from the 3-D temperature distribution was obtained. The iterative method of finite-difference avoids the problem of solving the super-large sparseness matrix, thus occupies less random memory and calculates faster than the normal finite-element method. The calculated results of temperature and thermal stress distribution in Nd:YAG slice are coincident with the experimental ones.
In this paper, based on the iterative method of finite-difference, 3-D instantaneoos and stable temperature distribution of square slice in the Nd:YAG disk laser under super-Gaussian pump light are calculated. Using the thermal balance differential equation and boundary condition of thermal elasticity body, 3-D thermal stress distribution from the 3-D temperature distribution was obtained. The iterative method of finite-difference avoids the problem of solving the super-large sparseness matrix, thus occupies less random memory and calculates faster than the normal finite-element method. The calculated results of temperature and thermal stress distribution in Nd:YAG slice are coincident with the experimental ones.
2008,
20.
Abstract:
Linear chirped pulse amplification at single pass free-electron laser（FEL） amplifier has been performed by means of the modified 1D time-dependent FEL code，and the averaged output power of pulses as functions of undulator length at different chirped parameters is given through numerical simulations．The peak power and width of the final compressed pulse with different chirped parameters have been computed．The results of numerical stimulations show that the peak power and width of the final compressed pulse are influenced mainly by the chirped parameter and the FEL bandwidth，and compressing the pulse amplified by single pass FEL is a feasible means of producing ultra short FEL pulses．
Linear chirped pulse amplification at single pass free-electron laser（FEL） amplifier has been performed by means of the modified 1D time-dependent FEL code，and the averaged output power of pulses as functions of undulator length at different chirped parameters is given through numerical simulations．The peak power and width of the final compressed pulse with different chirped parameters have been computed．The results of numerical stimulations show that the peak power and width of the final compressed pulse are influenced mainly by the chirped parameter and the FEL bandwidth，and compressing the pulse amplified by single pass FEL is a feasible means of producing ultra short FEL pulses．
2008,
20.
Abstract:
Aerial target under day-time condition shows complex imaging characteristics, like misshapen and blur edges, even flickering and inconsecutive imaging, which become a bottleneck of detecting and tracking targets in tracking system. Point spread functio (PSF) is determined combining with the feed information of tracking process and use a new model of image restoration proposed by Ben-Ezra is used to deblur the motion target. Association networks model with linking mechanism is constructed with similarity based on accompanying values of the target features of flickering image and losing of target. Simulations are conducted using the proposed method for image sequences, which obtain the good results.
Aerial target under day-time condition shows complex imaging characteristics, like misshapen and blur edges, even flickering and inconsecutive imaging, which become a bottleneck of detecting and tracking targets in tracking system. Point spread functio (PSF) is determined combining with the feed information of tracking process and use a new model of image restoration proposed by Ben-Ezra is used to deblur the motion target. Association networks model with linking mechanism is constructed with similarity based on accompanying values of the target features of flickering image and losing of target. Simulations are conducted using the proposed method for image sequences, which obtain the good results.
2008,
20.
Abstract:
A method of controlling chaotic behavior in erbium-doped fiber dual-ring laser is proposed by using couplers to feed the laser outputs back into the system and control the decay rate of the system indirectly. The chaotic fiber laser is controlled by selecting appropriate feedback coefficients which are defined by the decay rate and the coupling coefficient of the system. The simulation results show that couplers are used to modulate the decay rate and the feedback coefficient, and the chaotic fiber can be controlled into the single-leriod, dual-period and stable states respectively. The larger the feedback coefficients is, the faster the laser enters into a stable state.
A method of controlling chaotic behavior in erbium-doped fiber dual-ring laser is proposed by using couplers to feed the laser outputs back into the system and control the decay rate of the system indirectly. The chaotic fiber laser is controlled by selecting appropriate feedback coefficients which are defined by the decay rate and the coupling coefficient of the system. The simulation results show that couplers are used to modulate the decay rate and the feedback coefficient, and the chaotic fiber can be controlled into the single-leriod, dual-period and stable states respectively. The larger the feedback coefficients is, the faster the laser enters into a stable state.
2008,
20.
Abstract:
In this paper, the ablation mechanisms of carbon fiber reinforced E-51 epoxy composite irradiated by repetition frequency laser whose wavelength was 1 064 nm were studied, and the effects of maximum power density, irradiation time, frequency and pulse width on the thermal ablation rate were discussed. The thermal analysis results indicate that the resin matrix begins to ablate while the temperature of the composite surface reaches the pyrolysis temperature, which is as low as 300 ℃. The ablation of carbon fiber is caused by vaporization when the temperature reaches vaporization point, while the avoidance of carbon oxidation is attributed to the protection of pyrolysis gas. With the maximum power density or frequency increasing, the thermal ablation rate raises at first and then tends to a
In this paper, the ablation mechanisms of carbon fiber reinforced E-51 epoxy composite irradiated by repetition frequency laser whose wavelength was 1 064 nm were studied, and the effects of maximum power density, irradiation time, frequency and pulse width on the thermal ablation rate were discussed. The thermal analysis results indicate that the resin matrix begins to ablate while the temperature of the composite surface reaches the pyrolysis temperature, which is as low as 300 ℃. The ablation of carbon fiber is caused by vaporization when the temperature reaches vaporization point, while the avoidance of carbon oxidation is attributed to the protection of pyrolysis gas. With the maximum power density or frequency increasing, the thermal ablation rate raises at first and then tends to a
2008,
20.
Abstract:
To study the starting characteristic of directly drained CW DF/HF chemical lasers(DDCL), a single-nozzle small-scale model of DDCL gas channel was set up, and a series of experiments were conducted with different working mediums and several diffusers. The effect of gas dynamic parameters of medium on the starting characteristic and minimum area of diffuser throat was also studied. The experimental results are compared with those caculated by one-dimension Steady State Theory. In addition, the effect of the base of the nozzle on the starting characteristic is discussed, and the comparison between two types of bases is made. The result indicates that the most effective means for improving the performance of DDCL is to operate with high specific heat ratio, low molecular weight primary gas an
To study the starting characteristic of directly drained CW DF/HF chemical lasers(DDCL), a single-nozzle small-scale model of DDCL gas channel was set up, and a series of experiments were conducted with different working mediums and several diffusers. The effect of gas dynamic parameters of medium on the starting characteristic and minimum area of diffuser throat was also studied. The experimental results are compared with those caculated by one-dimension Steady State Theory. In addition, the effect of the base of the nozzle on the starting characteristic is discussed, and the comparison between two types of bases is made. The result indicates that the most effective means for improving the performance of DDCL is to operate with high specific heat ratio, low molecular weight primary gas an
2008,
20.
Abstract:
Continuous triangle waveform as the magnetic field current of scanning magnet can give good uniformity degree of radiation in industrial radiation accelerator. This paper introduced the design of a scanning magnet power-supply used in a 10 MeV industrial radiation accelerator. The scanning magnet powersupply can produce continuous triangle waveform current. The frequency can be adjusted by step length of 1 Hz ranged from 20 Hz to 50 Hz, and the peak-to-peak current is 20 A. The principle of triangle waveform modulator, linear degree of triangle waveform, control system based on singlechip and it's antijamming measure in industrial circumstance are presented. Both theoretical analysis and result of application show that linear degree of scanning and uniformity degree radiation of th
Continuous triangle waveform as the magnetic field current of scanning magnet can give good uniformity degree of radiation in industrial radiation accelerator. This paper introduced the design of a scanning magnet power-supply used in a 10 MeV industrial radiation accelerator. The scanning magnet powersupply can produce continuous triangle waveform current. The frequency can be adjusted by step length of 1 Hz ranged from 20 Hz to 50 Hz, and the peak-to-peak current is 20 A. The principle of triangle waveform modulator, linear degree of triangle waveform, control system based on singlechip and it's antijamming measure in industrial circumstance are presented. Both theoretical analysis and result of application show that linear degree of scanning and uniformity degree radiation of th
2008,
20.
Abstract:
Based on the experimental device of the water spiral pulse forming line(PFL) type electron beam accelerator, the effect of inductance between the middle and outer cylinders of PFL on diode voltage is theoretically and experimentally studied in this paper. The formulae are introduced, with which the effect of inductance on diode voltage is calculated. In addition, the diode voltage waveform is simulated through the Pspice software. The theoretical and simulated results agree well with the experimental results, which show that large inductance between middle and outer cylinders can shorten the waveform flat part of diode voltage, increase waveform rise time and reduce the diode peak voltage. When the inductance is smaller than 200 nH, a nearly square voltage waveform can be obtained in field
Based on the experimental device of the water spiral pulse forming line(PFL) type electron beam accelerator, the effect of inductance between the middle and outer cylinders of PFL on diode voltage is theoretically and experimentally studied in this paper. The formulae are introduced, with which the effect of inductance on diode voltage is calculated. In addition, the diode voltage waveform is simulated through the Pspice software. The theoretical and simulated results agree well with the experimental results, which show that large inductance between middle and outer cylinders can shorten the waveform flat part of diode voltage, increase waveform rise time and reduce the diode peak voltage. When the inductance is smaller than 200 nH, a nearly square voltage waveform can be obtained in field
2008,
20.
Abstract:
The C band MILO is simulated by the 3-D PIC code KARAT program in order to study the reason of frequent higher order modes in experiment and their influence on the performance of MILO. Higher order modes are caused by wave-beam action under condition of non-symmetry excitation mechanism in simulation, similar to those found in experiment. The mode of 4.01 GHz is identified and concluded as transformed through coaxial- line from the TM11 mode rising in slow-wave cavities. The other two higher order modes of 3.67 GHz and 4.53 GHz could not be concluded now.
The C band MILO is simulated by the 3-D PIC code KARAT program in order to study the reason of frequent higher order modes in experiment and their influence on the performance of MILO. Higher order modes are caused by wave-beam action under condition of non-symmetry excitation mechanism in simulation, similar to those found in experiment. The mode of 4.01 GHz is identified and concluded as transformed through coaxial- line from the TM11 mode rising in slow-wave cavities. The other two higher order modes of 3.67 GHz and 4.53 GHz could not be concluded now.
2008,
20.
Abstract:
A 324 MHz drift-tube linac(DTL) is designed for proton cancer therapy. The design demands low power dissipation and short tank. The DTL accelerates beam from 2.5 MeV to 7 MeV, with RF power of 265 kW and total length of 1.9 m. The DTL uses permanent-quadrupole magnet(PQM) inside the drift tubes arranged in an FODO lattice. A new matching method is designed. In stead of the traditional beam transport line, the first four cells in DTL are designed as matching section. It causes the beam ellipse from radio-frequency quadrupole linac(RFQ) to satisfy conditions specified by the DTL periodic structure. The dynamics simulation was performed with PARMILA, and almost no emittance growth has been found.
A 324 MHz drift-tube linac(DTL) is designed for proton cancer therapy. The design demands low power dissipation and short tank. The DTL accelerates beam from 2.5 MeV to 7 MeV, with RF power of 265 kW and total length of 1.9 m. The DTL uses permanent-quadrupole magnet(PQM) inside the drift tubes arranged in an FODO lattice. A new matching method is designed. In stead of the traditional beam transport line, the first four cells in DTL are designed as matching section. It causes the beam ellipse from radio-frequency quadrupole linac(RFQ) to satisfy conditions specified by the DTL periodic structure. The dynamics simulation was performed with PARMILA, and almost no emittance growth has been found.
2008,
20.
Abstract:
A femto-second electron bunch facility has been constructed and commissioned at the Shanghai Institute of Applied Physics(SINAP). The linac of this facility consists of an S-band thermionic cathode RF-gun, an alpha magnet and a SLAC-type accelerating tube to generate a beam, then compress the micro-bunches, and finally accelerate the beam to 20~30 MeV. Preliminary experimental result shows that the length of the micro-bunches is about 250 fs. The measured beam parameters of this facility are presented in this paper.
A femto-second electron bunch facility has been constructed and commissioned at the Shanghai Institute of Applied Physics(SINAP). The linac of this facility consists of an S-band thermionic cathode RF-gun, an alpha magnet and a SLAC-type accelerating tube to generate a beam, then compress the micro-bunches, and finally accelerate the beam to 20~30 MeV. Preliminary experimental result shows that the length of the micro-bunches is about 250 fs. The measured beam parameters of this facility are presented in this paper.
2008,
20.
Abstract:
hiver was used for getting and storaging data from IOCs of accelerator control system. Software, client and web human-machine interfaces were developed for computer users to retrieval data online or off-line intelligently. This system is convenient and has run stably for several months. With this system the processing and analyzing data can be more efficiently collected by researchers. Thus the system meets the needs of the HLS machine operation and machinery research．
hiver was used for getting and storaging data from IOCs of accelerator control system. Software, client and web human-machine interfaces were developed for computer users to retrieval data online or off-line intelligently. This system is convenient and has run stably for several months. With this system the processing and analyzing data can be more efficiently collected by researchers. Thus the system meets the needs of the HLS machine operation and machinery research．
2008,
20.
Abstract:
This paper describes the characters of a control system EPICS, which is popular in large accelerator laboratories in the world. It is a software toolkit for building process control system for a wide variety of experimental and industrial applications. Its software tools provide independent and expandable modules for system configuration, distributed process control, run-time database, alarm manager, etc. This paper describes the process of creating device support module for the magnet power supply device with serial port and the skeleton of the control system. It also describes the characters of ASYN software. And this work prepares for building the control system of the 30 MeV linac. The EPICS toolkit will be applied in the control system of the linac in FEL research, with satisfactory
This paper describes the characters of a control system EPICS, which is popular in large accelerator laboratories in the world. It is a software toolkit for building process control system for a wide variety of experimental and industrial applications. Its software tools provide independent and expandable modules for system configuration, distributed process control, run-time database, alarm manager, etc. This paper describes the process of creating device support module for the magnet power supply device with serial port and the skeleton of the control system. It also describes the characters of ASYN software. And this work prepares for building the control system of the 30 MeV linac. The EPICS toolkit will be applied in the control system of the linac in FEL research, with satisfactory
2008,
20.
Abstract:
The dimensions of the electron gun are obtained by means of comparing algorithm to match objective perveance with the data in the database. Objective dimensions is acquired by the reduced scale method. An objective function is introduced, which takes account of perveance,beam waist and laminarity. A simplex method is applied to optimize the objective function to gain better electron laminar flow. The design of electron gun based on comparing algorithm and simplex method is efficient and has general application in electron guns with various properties.
The dimensions of the electron gun are obtained by means of comparing algorithm to match objective perveance with the data in the database. Objective dimensions is acquired by the reduced scale method. An objective function is introduced, which takes account of perveance,beam waist and laminarity. A simplex method is applied to optimize the objective function to gain better electron laminar flow. The design of electron gun based on comparing algorithm and simplex method is efficient and has general application in electron guns with various properties.
Diagnosis of hydrogen plasmas at low temperature and low pressure by spectroscopy and Langmuir probe
2008,
20.
Abstract:
The emission spectroscopy and I-V characteristics of hydrogen plasmas excited in helicon-wave plasma chemical vapor deposition(HWP-CVD) device have been measured by emission spectroscopy method and Langmuir probe. The density of the excited hydrogen atoms, plasma density and electron energy distribution function(EEDF) were analyzed by corona model and Druyvestey method. The results indicate that the density of the excited hydrogen atoms increases with the increase of input power while decreases with the increase of pressure. The plasma density increase linearly with the increase of input power and reaches 1012 cm-3. The plasma density increases to a peak value and then decreases with the increase of pressure. The electron average energy increases gradually then gets saturated with the inc
The emission spectroscopy and I-V characteristics of hydrogen plasmas excited in helicon-wave plasma chemical vapor deposition(HWP-CVD) device have been measured by emission spectroscopy method and Langmuir probe. The density of the excited hydrogen atoms, plasma density and electron energy distribution function(EEDF) were analyzed by corona model and Druyvestey method. The results indicate that the density of the excited hydrogen atoms increases with the increase of input power while decreases with the increase of pressure. The plasma density increase linearly with the increase of input power and reaches 1012 cm-3. The plasma density increases to a peak value and then decreases with the increase of pressure. The electron average energy increases gradually then gets saturated with the inc
2008,
20.
Abstract:
Development of quantum-dot-array diffraction grating (QDADG)with single order diffraction properties is important for laser fusion research. The diffraction principle and fabrication method are introduced in this article. Diffraction properties of quantum-dot-array diffraction grating are studied when visible light radiates grating with different wavelength and incidence angle. It shows that QDADG can get rid of the influence of high order diffraction, which will solve the key problem (i.e. distortion from high order diffraction) of the present diffraction grating spectroscopy. QDADG for visible light is a potential alternative for X-ray, extreme ultraviolet and microwave diagnoses．
Development of quantum-dot-array diffraction grating (QDADG)with single order diffraction properties is important for laser fusion research. The diffraction principle and fabrication method are introduced in this article. Diffraction properties of quantum-dot-array diffraction grating are studied when visible light radiates grating with different wavelength and incidence angle. It shows that QDADG can get rid of the influence of high order diffraction, which will solve the key problem (i.e. distortion from high order diffraction) of the present diffraction grating spectroscopy. QDADG for visible light is a potential alternative for X-ray, extreme ultraviolet and microwave diagnoses．
2008,
20.
Abstract:
To satisfy the special requirement of the X-ray diagnosis instrument which needs long working distance and wide spectrum measurement in ICF, a new two-channel curved crystal spectrometer has been designed according to the reflecting geometry of convexity. The spectrometer diffracts X-ray by Si(111) and Qz(10—10) curved crystals with overlapping coverage of 0.30~0.65 nm, and the spectra are recorded by X-CCD detectors. The spectrometers has been applied to diagnostics with Shenguang-Ⅲ Prototype. Data analysis demonstrates that the spectra of experiment are accord with those of the theoretical simulation.
To satisfy the special requirement of the X-ray diagnosis instrument which needs long working distance and wide spectrum measurement in ICF, a new two-channel curved crystal spectrometer has been designed according to the reflecting geometry of convexity. The spectrometer diffracts X-ray by Si(111) and Qz(10—10) curved crystals with overlapping coverage of 0.30~0.65 nm, and the spectra are recorded by X-CCD detectors. The spectrometers has been applied to diagnostics with Shenguang-Ⅲ Prototype. Data analysis demonstrates that the spectra of experiment are accord with those of the theoretical simulation.
2008,
20.
Abstract:
In order to optimize the soft X-ray lens design, obtain high power density soft X-ray without other particles by combining it with plasma radiant point, experiments of measuring transmission efficiency with the power density range of 6×106～1.5×107 W/cm2 for the X-ray capillary on Qiangguang Ⅰ facility were carried out. The results show that, for the capillary of glass DM308, basically, the power density of the output soft X-ray from the capillary is linear with the power density of the incidence soft X-ray; when the power density of the incidence soft X-ray is 1.2×107 W/cm2, the average transmission efficiency is 16.3%. Based on the experiment results, soft X-ray lens were made, and power density 2.1×109 W/cm2 of soft X-ray without plasma fragment was obtained at the focal point.
In order to optimize the soft X-ray lens design, obtain high power density soft X-ray without other particles by combining it with plasma radiant point, experiments of measuring transmission efficiency with the power density range of 6×106～1.5×107 W/cm2 for the X-ray capillary on Qiangguang Ⅰ facility were carried out. The results show that, for the capillary of glass DM308, basically, the power density of the output soft X-ray from the capillary is linear with the power density of the incidence soft X-ray; when the power density of the incidence soft X-ray is 1.2×107 W/cm2, the average transmission efficiency is 16.3%. Based on the experiment results, soft X-ray lens were made, and power density 2.1×109 W/cm2 of soft X-ray without plasma fragment was obtained at the focal point.
2008,
20.
Abstract:
Fe-doped hydrogenated amorphous carbon (a-C:H:Fe) films were deposited from T2B/ferrocene/H2 gas mixtures by plasma enhanced metal organic chemical vapor deposition(PEMOCVD). X-ray photoelectron spectroscopy(XPS) was used to probe the composition of deposited a-C:H:Fe films. Deposition rate, surface topography, thermal stability and optical gap were also measured by surface profiler, FESEM, thermal gravity analysis and UV-visible spectroscopy. The investigation results show that the deposition rate of the a-C:H:Fe films is rapider, and the surface grains are smaller than that of the a-C:H films. The a-C:H:Fe films are carbonized more easily than the a-C:H films, as their Tauc optical gap becomes 0.3 eV narrower than that of the a-C:H films.
Fe-doped hydrogenated amorphous carbon (a-C:H:Fe) films were deposited from T2B/ferrocene/H2 gas mixtures by plasma enhanced metal organic chemical vapor deposition(PEMOCVD). X-ray photoelectron spectroscopy(XPS) was used to probe the composition of deposited a-C:H:Fe films. Deposition rate, surface topography, thermal stability and optical gap were also measured by surface profiler, FESEM, thermal gravity analysis and UV-visible spectroscopy. The investigation results show that the deposition rate of the a-C:H:Fe films is rapider, and the surface grains are smaller than that of the a-C:H films. The a-C:H:Fe films are carbonized more easily than the a-C:H films, as their Tauc optical gap becomes 0.3 eV narrower than that of the a-C:H films.
2008,
20.
Abstract:
A side-on shadowgraph system was developed to dectect the velocity of the target in the equation of state experiments, using the visible laser as detection beam. The equation of state experiments were carried out on the high power excimer laser system called “HeavenⅠ” with laser wavelength of 248.5 nm. The velocity of 50 μm thick aluminum target was 3.28 km/s with laser intensity of 8.3×1011 W/cm2, and the velocity of 13 μm thick aluminum target with 100 μm thick ablator was 2.52 km/s with laser intensity of 4.7×1011 W/cm2. Through analysing the error between the experiment and the caculation, the maximum angle between detection beam and target was 2.06°, and the error cased by such an angle could be neglected for the accuracy of the experiments.
A side-on shadowgraph system was developed to dectect the velocity of the target in the equation of state experiments, using the visible laser as detection beam. The equation of state experiments were carried out on the high power excimer laser system called “HeavenⅠ” with laser wavelength of 248.5 nm. The velocity of 50 μm thick aluminum target was 3.28 km/s with laser intensity of 8.3×1011 W/cm2, and the velocity of 13 μm thick aluminum target with 100 μm thick ablator was 2.52 km/s with laser intensity of 4.7×1011 W/cm2. Through analysing the error between the experiment and the caculation, the maximum angle between detection beam and target was 2.06°, and the error cased by such an angle could be neglected for the accuracy of the experiments.
2008,
20.
Abstract:
In FDTD calculation of layered media, it is difficulty to set the slant incident plane wave in arbitrary layered background media. To solve this problem, 1D Maxwell's equations including oblique incident angle are derived based on 2D equations for TM and TE modes,they are then used to simulate plane wave slanting along the connective boundaries in layered media. Computations aiming at the fused silica covered with thin film indicate the electromagnetic wave impels perfectly in each layer and validate the scheme for introducing plane wave. The computation of damaged component holding vacuum bubble is also given to illuminate the application．
In FDTD calculation of layered media, it is difficulty to set the slant incident plane wave in arbitrary layered background media. To solve this problem, 1D Maxwell's equations including oblique incident angle are derived based on 2D equations for TM and TE modes,they are then used to simulate plane wave slanting along the connective boundaries in layered media. Computations aiming at the fused silica covered with thin film indicate the electromagnetic wave impels perfectly in each layer and validate the scheme for introducing plane wave. The computation of damaged component holding vacuum bubble is also given to illuminate the application．
2008,
20.
Abstract:
A aperture-coupling directional coupler between rectangular waveguide and circular waveguide through small aperture was designed to measure the output power of high power microwave devices. The formulas of single-hole coupling degree were made out with loose-coupling theory. Numerical computation of aperture was made by MATLAB. The compared results show that the theory was reasonable. Based on the results of single hole coupling, some useful conclusions were derived about multi-hole coupling. Single hole coupler can not realize directional coupling, but even numbers of holes can.The results are ualuable for theoretical research and application as well．
A aperture-coupling directional coupler between rectangular waveguide and circular waveguide through small aperture was designed to measure the output power of high power microwave devices. The formulas of single-hole coupling degree were made out with loose-coupling theory. Numerical computation of aperture was made by MATLAB. The compared results show that the theory was reasonable. Based on the results of single hole coupling, some useful conclusions were derived about multi-hole coupling. Single hole coupler can not realize directional coupling, but even numbers of holes can.The results are ualuable for theoretical research and application as well．
2008,
20.
Abstract:
Stripline beam position monitors(BPM) can be used as a nonintercepting emittance monitor and it is independent of the beam distribution. Usually, difference over sum method is used to pick up the quadrupole component. This paper puts forward two new methods’ log-ratio method and combination method. The analysis and comparison of these methods are introduced. Combination method is the best, and log-ratio method is better than difference over sum method. Changing the current of quadrupole magnets m times (more than six times) upstream from BPM to change the transfer matrix and measuring the quadrupole component for each change, the emittance can be calculated.
Stripline beam position monitors(BPM) can be used as a nonintercepting emittance monitor and it is independent of the beam distribution. Usually, difference over sum method is used to pick up the quadrupole component. This paper puts forward two new methods’ log-ratio method and combination method. The analysis and comparison of these methods are introduced. Combination method is the best, and log-ratio method is better than difference over sum method. Changing the current of quadrupole magnets m times (more than six times) upstream from BPM to change the transfer matrix and measuring the quadrupole component for each change, the emittance can be calculated.
2008,
20.
Abstract:
According to the relationship between the parameters of PIN diode and temperature,power response characteristics of PIN diode limiter at different temperatures are simulated with a limiter circuit model which is based on the base area ambipolar carrier transport equation of PIN diode in Pspice. The results show that the power loss in the limiter is increased when the temperature increass. A temperature control system was employed in the experiment. The experimental results agree with the simulation results. After one thermal shock,it is observed that the limiting capacity of the limiter is weakened.
According to the relationship between the parameters of PIN diode and temperature,power response characteristics of PIN diode limiter at different temperatures are simulated with a limiter circuit model which is based on the base area ambipolar carrier transport equation of PIN diode in Pspice. The results show that the power loss in the limiter is increased when the temperature increass. A temperature control system was employed in the experiment. The experimental results agree with the simulation results. After one thermal shock,it is observed that the limiting capacity of the limiter is weakened.
2008,
20.
Abstract:
Based on the widely used monopole on conducting plane,the response characters of antenna exposed to high electromagnetic pulse,high power microwave and ultra wideband electromagnetic pulse were analysed by moment method,and the time domain and frequency domain response waveforms of the three types electromagnetic pulse coupled to the antenna was calculated.The monopole response waveform of the narrowband pulse is much similar to the incident waveform,the peak current is 100 A,60 A and 10.3 A ordinally,boosting the demand for higher power capacity of the actual high power limiters.
Based on the widely used monopole on conducting plane,the response characters of antenna exposed to high electromagnetic pulse,high power microwave and ultra wideband electromagnetic pulse were analysed by moment method,and the time domain and frequency domain response waveforms of the three types electromagnetic pulse coupled to the antenna was calculated.The monopole response waveform of the narrowband pulse is much similar to the incident waveform,the peak current is 100 A,60 A and 10.3 A ordinally,boosting the demand for higher power capacity of the actual high power limiters.
2008,
20.
Abstract:
Irradiation effects of proton and gamma-ray on a CVD diamond detector were studied on Beijing Tandem accelerator and 60Co source. The decrease of the detector’s signal current was less than 3.5% after irradiated by 1013 cm-2,9 MeV continuous protons. Dark current didn’t change obviously after the proton irradiation. The calculated radiation damage coefficient is 1.3×1016 μm-1·cm2, which is much higher than that of Si PIN detectors. The signal current increased a little after irradiated by 10.32 C/kg and 1.25 MeV γ-ray, as the electrons excited by γ-ray can deduce traps in diamond. And the increase is less than 0.7%. Diamond detector has high radiation hardness and can be used in high radiation detection.
Irradiation effects of proton and gamma-ray on a CVD diamond detector were studied on Beijing Tandem accelerator and 60Co source. The decrease of the detector’s signal current was less than 3.5% after irradiated by 1013 cm-2,9 MeV continuous protons. Dark current didn’t change obviously after the proton irradiation. The calculated radiation damage coefficient is 1.3×1016 μm-1·cm2, which is much higher than that of Si PIN detectors. The signal current increased a little after irradiated by 10.32 C/kg and 1.25 MeV γ-ray, as the electrons excited by γ-ray can deduce traps in diamond. And the increase is less than 0.7%. Diamond detector has high radiation hardness and can be used in high radiation detection.
2008,
20.
Abstract:
ZnO thin films on various substrates were prepared by in situ oxidation of RF sputtered Zn3N2 films. The structural and photoluminscent properties of ZnO films were measured by X-ray diffraction (XRD), scanning electron microscopy (SEM) and photoluminescence (PL). XRD results showed that Zn3N2 films had been completely transformed into ZnO films after in situ oxidization at 500 ℃ for 3 h. The films on glass and fused silica glass substrates had no preferential orientation while the films on Si (100) substrates exhibited (002)axis preferred orientation. PL measurements showed that ZnO films on Si (100) and fused silica glass substrates possessed good photoluminscent properties with strong near band edge excitonic UV emission and weak defect-related deep-level emission in the visible region
ZnO thin films on various substrates were prepared by in situ oxidation of RF sputtered Zn3N2 films. The structural and photoluminscent properties of ZnO films were measured by X-ray diffraction (XRD), scanning electron microscopy (SEM) and photoluminescence (PL). XRD results showed that Zn3N2 films had been completely transformed into ZnO films after in situ oxidization at 500 ℃ for 3 h. The films on glass and fused silica glass substrates had no preferential orientation while the films on Si (100) substrates exhibited (002)axis preferred orientation. PL measurements showed that ZnO films on Si (100) and fused silica glass substrates possessed good photoluminscent properties with strong near band edge excitonic UV emission and weak defect-related deep-level emission in the visible region
2008,
20.
Abstract:
By solving Laplace’s equation with the first class boundary condition, the analytical expression of the axial potential distribution in a typical triode immersion objective was achieved. Based on the related expression, effect of the geometrical parameters and potential ones on the focusing properties of the electrostatic lens is illustrated. The optained conclusions are that ununiformity of the axial electric field directly results in the relatively weakened focusing field, together with the improvement of particles’ temporal and spatial dispersion. The achieved modulating means are as follows: augment of the potential value and aperture size of the modulating electrode, increase of the intervals between modulating electrode and accelerating one, decrease of that of cathode and the form
By solving Laplace’s equation with the first class boundary condition, the analytical expression of the axial potential distribution in a typical triode immersion objective was achieved. Based on the related expression, effect of the geometrical parameters and potential ones on the focusing properties of the electrostatic lens is illustrated. The optained conclusions are that ununiformity of the axial electric field directly results in the relatively weakened focusing field, together with the improvement of particles’ temporal and spatial dispersion. The achieved modulating means are as follows: augment of the potential value and aperture size of the modulating electrode, increase of the intervals between modulating electrode and accelerating one, decrease of that of cathode and the form
2008,
20.
Abstract:
To apply industrial computed tomography (CT) technology to reverse engineering effectively, an industrial CT slicing image preprocessing system is developed. The system involves three parts, which deal with image process, contour fitting and data format transform. Using professional software of reverse engineering, the output IGES format data of the system can be reconstructed into 3D CAD model directly, which reduces workload of reconstructing 3D CAD model. On the other hand, the output DXF format data of the system can be processed by AutoCAD directly, which improves flexibility of the system. Furthermore, the precision of fitted contour is improved by means of calculating the centre and radius of fitted arc based on weighted method. Finally, the correctness of this system is proved wi
To apply industrial computed tomography (CT) technology to reverse engineering effectively, an industrial CT slicing image preprocessing system is developed. The system involves three parts, which deal with image process, contour fitting and data format transform. Using professional software of reverse engineering, the output IGES format data of the system can be reconstructed into 3D CAD model directly, which reduces workload of reconstructing 3D CAD model. On the other hand, the output DXF format data of the system can be processed by AutoCAD directly, which improves flexibility of the system. Furthermore, the precision of fitted contour is improved by means of calculating the centre and radius of fitted arc based on weighted method. Finally, the correctness of this system is proved wi
2008,
20.
Abstract:
The weak damage induced by 0.28 MeV Zn+ ion implantation was studied in AlAs/GaAs and GaAs/Ga0.92In0.08. As superlattice samples using Raman spectroscopy. The variation of the average strain in the implanted layers with the implantation dose was evaluated. It was found that the strain levels caused by ion implantation in the dose range of 5×1013 cm－2 to 5×1014 cm－2 were lower than the reported maximum un-relaxed strain of bulk GaAs. It was shown that the lattice strain caused by ion implantation had become saturated at high implantation doses,indicating that the defect emergence and recombination had reached equilibrium and resulted in a uniform strain field．
The weak damage induced by 0.28 MeV Zn+ ion implantation was studied in AlAs/GaAs and GaAs/Ga0.92In0.08. As superlattice samples using Raman spectroscopy. The variation of the average strain in the implanted layers with the implantation dose was evaluated. It was found that the strain levels caused by ion implantation in the dose range of 5×1013 cm－2 to 5×1014 cm－2 were lower than the reported maximum un-relaxed strain of bulk GaAs. It was shown that the lattice strain caused by ion implantation had become saturated at high implantation doses,indicating that the defect emergence and recombination had reached equilibrium and resulted in a uniform strain field．
2008,
20.
Abstract:
The channeling effect and radiation of charged particles in the superlattice quantum well are predicted. The motion behaviors of a charged particle in the superlattice quantum well are described by using sine-squared potential. In the frame of the classical mechanics the motion equation of a particle is reduced to the pendulum equation by using the sine-squared potential. The solution of the equation and the period of the particle motion are expressed exactly by means of Jacobian elliptic function and elliptic integral. The radiation energy and radiation intensity of the charged particles are derived。The results show that the radiation energy entered the X-energy zone for a particle with an energy of 100 MeV. It is possible to take the radiation as an X-Laser or a γ-laser.
The channeling effect and radiation of charged particles in the superlattice quantum well are predicted. The motion behaviors of a charged particle in the superlattice quantum well are described by using sine-squared potential. In the frame of the classical mechanics the motion equation of a particle is reduced to the pendulum equation by using the sine-squared potential. The solution of the equation and the period of the particle motion are expressed exactly by means of Jacobian elliptic function and elliptic integral. The radiation energy and radiation intensity of the charged particles are derived。The results show that the radiation energy entered the X-energy zone for a particle with an energy of 100 MeV. It is possible to take the radiation as an X-Laser or a γ-laser.
2008,
20.
Abstract:
The location and the shape of emitting surface in plasma ion source determine the extraction character of ion beam, and they always depend on the parameters of plasma, the configuration of electrodes and the extraction voltage, etc. They always automatically adjust to a certain state. In this paper, a 2D theoretical method to estimate these two factors, namely, an unmagnetized plasma can not penetrate a region with an applied vacuum dc electric field magnitude above a critical value. Thus the location and the shape of ion emitting surface can be found by solving the equation of Laplace of extraction system directly. Simultaneously, numerical simulation experiments of the location and the shape of ion emitting surface and the extraction beam current in different extraction systems based on
The location and the shape of emitting surface in plasma ion source determine the extraction character of ion beam, and they always depend on the parameters of plasma, the configuration of electrodes and the extraction voltage, etc. They always automatically adjust to a certain state. In this paper, a 2D theoretical method to estimate these two factors, namely, an unmagnetized plasma can not penetrate a region with an applied vacuum dc electric field magnitude above a critical value. Thus the location and the shape of ion emitting surface can be found by solving the equation of Laplace of extraction system directly. Simultaneously, numerical simulation experiments of the location and the shape of ion emitting surface and the extraction beam current in different extraction systems based on
2008,
20.
Abstract:
In order to obtain good etching effect, parameters as working pressure and ratio of gas flux for etching processes with and without Al mask were studied. The results are as follows: under the same conditions, etching rate varies little; whether or not having Al mask on a: CH films have no effect on etching rate; when gas flux is fixed, etching rate descends with bulk ratio of argon and oxygen increasing. In this study, the best etching conditions are using pure oxygen gas, flux of 4 mL·s-1, working pressure of 9.9×10-2 Pa, microwave current of 80 mA, bias of -90 V. Under these conditions, fabricated micro-gear has vertical sidewall, small degree of distortion. Micro-gear could be released from the substrate using HF solution.
In order to obtain good etching effect, parameters as working pressure and ratio of gas flux for etching processes with and without Al mask were studied. The results are as follows: under the same conditions, etching rate varies little; whether or not having Al mask on a: CH films have no effect on etching rate; when gas flux is fixed, etching rate descends with bulk ratio of argon and oxygen increasing. In this study, the best etching conditions are using pure oxygen gas, flux of 4 mL·s-1, working pressure of 9.9×10-2 Pa, microwave current of 80 mA, bias of -90 V. Under these conditions, fabricated micro-gear has vertical sidewall, small degree of distortion. Micro-gear could be released from the substrate using HF solution.
2008,
20.
Abstract:
The medium-type fast-neutron detector responds to direct neutron irradiation and it has an extreme effect on its design and practical applications. Monte-Carlo simulation programs based on Geant4 toolkit are developed to study the neutron direct radiation response sensitivity of the medium-type fast-neutron detector. The emission of the charged heavy particles of commonly used materials of detector’s sensitive unit due to neutron incidence is simulated. The result shows that the selection of the materials of the charge collector, the threshold absorber and the rear isolator directly affect on the response sensitivity of neutron direct radiation. The response sensitivity of neutron direct radiation contributes about 6% to the total neutron sensitivity in the present sensitive unit which us
The medium-type fast-neutron detector responds to direct neutron irradiation and it has an extreme effect on its design and practical applications. Monte-Carlo simulation programs based on Geant4 toolkit are developed to study the neutron direct radiation response sensitivity of the medium-type fast-neutron detector. The emission of the charged heavy particles of commonly used materials of detector’s sensitive unit due to neutron incidence is simulated. The result shows that the selection of the materials of the charge collector, the threshold absorber and the rear isolator directly affect on the response sensitivity of neutron direct radiation. The response sensitivity of neutron direct radiation contributes about 6% to the total neutron sensitivity in the present sensitive unit which us
2008,
20.
Abstract:
A symmetrical pulsed high magnetic field generator is equipped to generate high magnetic field of 18 T, and its field period is about 10 μs. The energy storage of the equipment depends on the pulsed capacitor. Its transmission system consists of a flat transmission line, cables and gas switches. The load is a single circular winding. For the two symmetrical loads to work at the same moment, a synchro trigger system is made, whose time dispersion is about 20 ns. When the working voltage of the generator and the synchro trigger system come up to 28 kV and 49 kV, respectively, and the air pressure of the gas switch reaches about 80 kPa, the highest intensity of magnetization in the center of the winding is 18 T.
A symmetrical pulsed high magnetic field generator is equipped to generate high magnetic field of 18 T, and its field period is about 10 μs. The energy storage of the equipment depends on the pulsed capacitor. Its transmission system consists of a flat transmission line, cables and gas switches. The load is a single circular winding. For the two symmetrical loads to work at the same moment, a synchro trigger system is made, whose time dispersion is about 20 ns. When the working voltage of the generator and the synchro trigger system come up to 28 kV and 49 kV, respectively, and the air pressure of the gas switch reaches about 80 kPa, the highest intensity of magnetization in the center of the winding is 18 T.
2008,
20.
Abstract:
A high voltage and high repetition rate sub-nanosecond gas switch is designed. Rise-time and fall-time of a sharpened pulse can be varied by turning two group of rotary knobs outside the cavity to adjust the peaking and chopping spaces. Results of experiments prove that the switch can work steadily at 5 Hz repetition rate and output a pulse with 278 kV peak voltage and 620 ps width, or works at 100 Hz repetition rate and output a pulse with 270 kV peak voltage and 700 ps width. The switch has been successfully used in high power pulse systems.
A high voltage and high repetition rate sub-nanosecond gas switch is designed. Rise-time and fall-time of a sharpened pulse can be varied by turning two group of rotary knobs outside the cavity to adjust the peaking and chopping spaces. Results of experiments prove that the switch can work steadily at 5 Hz repetition rate and output a pulse with 278 kV peak voltage and 620 ps width, or works at 100 Hz repetition rate and output a pulse with 270 kV peak voltage and 700 ps width. The switch has been successfully used in high power pulse systems.
2008,
20.
Abstract:
Based on a combination of pulse transformer and distributed electrical parameter pulse forming line(PFL), a high power pulse generating and forming technology is introduced. The basic plan theory and method is briefly summarized, and an integrative generator of pulse transformer and PFL is developed. With the coaxial open cores of the transformer acting as the inner and outer conductors of PFL, this device unifies two important individual parts and has a compact configuration. The high-voltage generator can steadily obtain output pulse voltage of 760 kV, peak power of 23 GW and more than 40 ns pulse duration when the transformer keeps a voltage of 1.65 MV at a burst of 100 Hz.
Based on a combination of pulse transformer and distributed electrical parameter pulse forming line(PFL), a high power pulse generating and forming technology is introduced. The basic plan theory and method is briefly summarized, and an integrative generator of pulse transformer and PFL is developed. With the coaxial open cores of the transformer acting as the inner and outer conductors of PFL, this device unifies two important individual parts and has a compact configuration. The high-voltage generator can steadily obtain output pulse voltage of 760 kV, peak power of 23 GW and more than 40 ns pulse duration when the transformer keeps a voltage of 1.65 MV at a burst of 100 Hz.
