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RSS2010 Vol. 22, No. 07
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2010,
22.
Abstract:
To improve beam quality and focusability performance, an adaptive optical system, which is based on the phase-conjugated principle and consists of Hartmann-Shack sensor, deformable mirror, control unit and software, was installed in the SILEX-I laser facility to correct its wavefront aberrations. The wavefront data and far-field focal spots were measured and analyzed. The results show that, the peak-valley value of the wavefront decreases from 1.885 μm to 0.438 μm and the root mean square value reduces from 0.379 μm to 0.052 μm with this adaptive optical system. In addition, the far-field focal spot is improved and the energy in the region where the intensity of each point is greater than 1/e2 of the laser beam peak intensity is 72.4% of the total energy after the wavefront aberrations
To improve beam quality and focusability performance, an adaptive optical system, which is based on the phase-conjugated principle and consists of Hartmann-Shack sensor, deformable mirror, control unit and software, was installed in the SILEX-I laser facility to correct its wavefront aberrations. The wavefront data and far-field focal spots were measured and analyzed. The results show that, the peak-valley value of the wavefront decreases from 1.885 μm to 0.438 μm and the root mean square value reduces from 0.379 μm to 0.052 μm with this adaptive optical system. In addition, the far-field focal spot is improved and the energy in the region where the intensity of each point is greater than 1/e2 of the laser beam peak intensity is 72.4% of the total energy after the wavefront aberrations
2010,
22.
Abstract:
Laser-induced damage threshold of fused silica under 355 nm laser were measured before and after chemical etching, UV laser conditioning, and the combined processing. The area of damage spots increased with successive pulses irradiation. The results showed that the laser-induced damage threshold of processed samples increased while the area growth rate decreased. Mitigation of damage sites on fused silica by localized CO2 laser treatment was also investigated. The laser-induced damage threshold of treated damage sites was as high as the fused silica substrate by R-on-1 tests. The damage growth of treated sites on fused silica was mitigated effectively.
Laser-induced damage threshold of fused silica under 355 nm laser were measured before and after chemical etching, UV laser conditioning, and the combined processing. The area of damage spots increased with successive pulses irradiation. The results showed that the laser-induced damage threshold of processed samples increased while the area growth rate decreased. Mitigation of damage sites on fused silica by localized CO2 laser treatment was also investigated. The laser-induced damage threshold of treated damage sites was as high as the fused silica substrate by R-on-1 tests. The damage growth of treated sites on fused silica was mitigated effectively.
2010,
22.
Abstract:
The three-dimensional transverse defect model on exit surface of fused silica was established. Three-dimensional finite-difference time-domain method was used to simulate the electric field intensity distribution in the vicinity of transverse cracks on fused silica subsurface. The modulation of incident light field caused by the width, depth, length and gradient angle of the cracks was analyzed. The results show that the maximal electric field intensity in fused silica will be enhanced as the depth and length increase. The maximal electric field intensity tends to be a constant when the length exceeds 1 μm. The fused silica is more fragile while the crack configuration factor is 1～2. The effect of light intensity enhancement on the rear surface is more obvious when total internal reflect
The three-dimensional transverse defect model on exit surface of fused silica was established. Three-dimensional finite-difference time-domain method was used to simulate the electric field intensity distribution in the vicinity of transverse cracks on fused silica subsurface. The modulation of incident light field caused by the width, depth, length and gradient angle of the cracks was analyzed. The results show that the maximal electric field intensity in fused silica will be enhanced as the depth and length increase. The maximal electric field intensity tends to be a constant when the length exceeds 1 μm. The fused silica is more fragile while the crack configuration factor is 1～2. The effect of light intensity enhancement on the rear surface is more obvious when total internal reflect
2010,
22.
Abstract:
To study the influence of polarization direction on far field of laser array with coherent combining, an onedimension analyses model of fiber laser array is established, and using Fourier optics, the expression for the far field intensity of coherent combining beams is deduced when the polarization direction of a single cell is deviated. Numerical calculation results show that, with the increasing of the deviation the maximum intensity of center lobe reduces, and the minimum intensity is no longer zero. The deviation of the polarization direction will not change the symmetry of the energy distribution. For the the array with 5 fiber lasers, when the deviation angle is π/2, the peak intensity will reduce to about 68% of the original．
To study the influence of polarization direction on far field of laser array with coherent combining, an onedimension analyses model of fiber laser array is established, and using Fourier optics, the expression for the far field intensity of coherent combining beams is deduced when the polarization direction of a single cell is deviated. Numerical calculation results show that, with the increasing of the deviation the maximum intensity of center lobe reduces, and the minimum intensity is no longer zero. The deviation of the polarization direction will not change the symmetry of the energy distribution. For the the array with 5 fiber lasers, when the deviation angle is π/2, the peak intensity will reduce to about 68% of the original．
2010,
22.
Abstract:
The atmospheric temperature profile and its time-dependent variation have many applications in geophysical research area, thus a Rayleigh-Raman temperature lidar was constructed to obtain atmospheric temperature profiles with high spatial and temporal resolution. This paper, introduces the temperature measurement principle and the key parameters of the Rayleigh-Raman lidar. In terms of the temperature inversion algorithms, background noise subtraction and the wavelet denoising algorithm are used to enhance the signal to noise ratio. Comparisons between the measurement of our lidar and atmospheric data model, satellite measurements are conducted, respectively. The results show good agreements and verify the accuracy of the lidar system, which means the lidar measurement can be used in the
The atmospheric temperature profile and its time-dependent variation have many applications in geophysical research area, thus a Rayleigh-Raman temperature lidar was constructed to obtain atmospheric temperature profiles with high spatial and temporal resolution. This paper, introduces the temperature measurement principle and the key parameters of the Rayleigh-Raman lidar. In terms of the temperature inversion algorithms, background noise subtraction and the wavelet denoising algorithm are used to enhance the signal to noise ratio. Comparisons between the measurement of our lidar and atmospheric data model, satellite measurements are conducted, respectively. The results show good agreements and verify the accuracy of the lidar system, which means the lidar measurement can be used in the
2010,
22.
Abstract:
Through the fourth order Runge-Kutta formulas, the multimode rate equations, tailored to accommodate different pumping methods, are employed to evaluate the pumping efficiency and the signal power in the multimode fiber amplifier. The effect of the tiny change of fiber length (about millimeter level) on the output beam quality is studied. The beam quality factor varies quasi-periodically with the tiny change of fiber length. And the period is dependent on the propagation constant difference between the eigen modes of the amplifier.
Through the fourth order Runge-Kutta formulas, the multimode rate equations, tailored to accommodate different pumping methods, are employed to evaluate the pumping efficiency and the signal power in the multimode fiber amplifier. The effect of the tiny change of fiber length (about millimeter level) on the output beam quality is studied. The beam quality factor varies quasi-periodically with the tiny change of fiber length. And the period is dependent on the propagation constant difference between the eigen modes of the amplifier.
2010,
22.
Abstract:
Based on the theory of angular spectrum diffraction, the diffraction transmission of the cat-eye effect reflected light under oblique incidence is derived by two-dimensional discrete Fourier transform and projection combination of the two diffraction apertures. Through numerical computation, the variation laws of the diffraction field distribution with the incidence angle and diffraction distance are given. Then an experiment is conducted to validate the law affected by the incidence angle. The results show that the method used in this paper can exactly describe the diffraction field distribution of the cat-eye reflected light under large angle oblique incidence, and the effect of incidence angle increase on the diffraction mode of the light field can be equivalent to the effect of diffrac
Based on the theory of angular spectrum diffraction, the diffraction transmission of the cat-eye effect reflected light under oblique incidence is derived by two-dimensional discrete Fourier transform and projection combination of the two diffraction apertures. Through numerical computation, the variation laws of the diffraction field distribution with the incidence angle and diffraction distance are given. Then an experiment is conducted to validate the law affected by the incidence angle. The results show that the method used in this paper can exactly describe the diffraction field distribution of the cat-eye reflected light under large angle oblique incidence, and the effect of incidence angle increase on the diffraction mode of the light field can be equivalent to the effect of diffrac
2010,
22.
Abstract:
Based on Taylor’s frozen turbulence hypothesis, analytical expressions of scintillation and phase fluctuation power spectrum of the light wave propagation in atmosphere with different refractive index spectrum of turbulence were deduced. The influence of turbulent refractive index scaling exponent, inner scale together with outer scale on light wave power spectrum was discussed. Analytic results were summarized as follows. Firstly, with the increase of turbulent refractive index scaling exponent, the low-frequency spectrum of atmospheric scintillation isn’t only a constant, the high-frequency spectrum obeys the power law with an increasing exponent, and the slope of phase fluctuation power spectrum is increasing in the whole frequency range. Secondly, the bigger the turbulent inner scale
Based on Taylor’s frozen turbulence hypothesis, analytical expressions of scintillation and phase fluctuation power spectrum of the light wave propagation in atmosphere with different refractive index spectrum of turbulence were deduced. The influence of turbulent refractive index scaling exponent, inner scale together with outer scale on light wave power spectrum was discussed. Analytic results were summarized as follows. Firstly, with the increase of turbulent refractive index scaling exponent, the low-frequency spectrum of atmospheric scintillation isn’t only a constant, the high-frequency spectrum obeys the power law with an increasing exponent, and the slope of phase fluctuation power spectrum is increasing in the whole frequency range. Secondly, the bigger the turbulent inner scale
2010,
22.
Abstract:
The structure of a self-developed Mie Doppler lidar system is introduced. Aiming at the problems existing in the former system, the receiver sub-system, working time series, and scanning mode etc. were upgraded. Experimental results show that the spectrum stability of optical discriminator is improved by 2.8 times. The blind range of detection is eliminated. With 9 000 laser shot integration and 21.2 m vertical resolution, the averaged standard deviation of horizontal wind speed and direction over the altitude from 0 to 2.5 km for three consecutive 10 min measured by the modified Mie Doppler lidar are below 0.43 m/s and 7.7° with the maximum values of 1 m/s and 18.3°, respectively. Comparisons of lidar and wiresonde wind observations show good agreement. With 1 000 laser shot integration
The structure of a self-developed Mie Doppler lidar system is introduced. Aiming at the problems existing in the former system, the receiver sub-system, working time series, and scanning mode etc. were upgraded. Experimental results show that the spectrum stability of optical discriminator is improved by 2.8 times. The blind range of detection is eliminated. With 9 000 laser shot integration and 21.2 m vertical resolution, the averaged standard deviation of horizontal wind speed and direction over the altitude from 0 to 2.5 km for three consecutive 10 min measured by the modified Mie Doppler lidar are below 0.43 m/s and 7.7° with the maximum values of 1 m/s and 18.3°, respectively. Comparisons of lidar and wiresonde wind observations show good agreement. With 1 000 laser shot integration
2010,
22.
Abstract:
According to the extended Huygens-Fresnel integral, propagation formulas of the spectrum of partially coherent Gaussian-Schell model(GSM) rectangular array beams have been derived. The changes of on-axis and off-axis spectral shifts in free space have been analyzed quantitatively. The effects of array beam parameters and the spatial coherent parameter of array beamlets on the spectral shifts have been discussed in detail. The results show that the spectral shifts of GSM array beams in free space depend on the source spectral density, the spatial coherent parameter of array beamlets, as well as the array beam parameters, i.e., the number and the separation of beamlets. Especially, the effect of the array beam parameters on the relative spectral shifts is more obvious.
According to the extended Huygens-Fresnel integral, propagation formulas of the spectrum of partially coherent Gaussian-Schell model(GSM) rectangular array beams have been derived. The changes of on-axis and off-axis spectral shifts in free space have been analyzed quantitatively. The effects of array beam parameters and the spatial coherent parameter of array beamlets on the spectral shifts have been discussed in detail. The results show that the spectral shifts of GSM array beams in free space depend on the source spectral density, the spatial coherent parameter of array beamlets, as well as the array beam parameters, i.e., the number and the separation of beamlets. Especially, the effect of the array beam parameters on the relative spectral shifts is more obvious.
2010,
22.
Abstract:
The metallic supersonic nozzle of chemical oxygen-iodine laser(COIL) needs heating to keep warm in use, which makes its structure complicated and the failure rate is high. Several materials are considered to be suitable for fabricating non-heating supersonic nozzles. As an example, the temperature field of the nozzle made of polyimide is simulated numerically to verify the feasibility of the non-metallic non-heating nozzle. The results indicate that the nozzle made of polyimide can prevent heat transmitting and iodine vapor cooling effectively and meet the requirements of laser nozzles.
The metallic supersonic nozzle of chemical oxygen-iodine laser(COIL) needs heating to keep warm in use, which makes its structure complicated and the failure rate is high. Several materials are considered to be suitable for fabricating non-heating supersonic nozzles. As an example, the temperature field of the nozzle made of polyimide is simulated numerically to verify the feasibility of the non-metallic non-heating nozzle. The results indicate that the nozzle made of polyimide can prevent heat transmitting and iodine vapor cooling effectively and meet the requirements of laser nozzles.
2010,
22.
Abstract:
The pulse frequency-domain interferometry is introduced as a new measurement technology with femtosecond resolution. Its working principle and system structure are elaborated, and the time difference and phase difference are pointed out as the primary factors determining the fringe period in frequency-domain interferometer. The velocity profile of an aluminium foil pumped by an 800 nm, 0.7 mJ, 35 fs laser pulse was measured by the frequency-domain interferometry. The preliminary measurement shows that the maximal velocity is 960 m/s with a rise time less than 5.77 ps in the velocity profile.
The pulse frequency-domain interferometry is introduced as a new measurement technology with femtosecond resolution. Its working principle and system structure are elaborated, and the time difference and phase difference are pointed out as the primary factors determining the fringe period in frequency-domain interferometer. The velocity profile of an aluminium foil pumped by an 800 nm, 0.7 mJ, 35 fs laser pulse was measured by the frequency-domain interferometry. The preliminary measurement shows that the maximal velocity is 960 m/s with a rise time less than 5.77 ps in the velocity profile.
2010,
22.
Abstract:
Currently, it’s difficult to manufacture large area grating and multiple smaller pieces of grating blocks splice large area gratings.The grating blocks will slightly in splicing process. This paper analyzes the splicing grating’s normal deformation characteristics, builds the theoretical model of deformation, and calculates and analyses the case of two grating blocks splicing. It is found the light field diffraction caused by a tiny deformation can not be ignores. The tolerance of grating mechanical measures to prevent deformation are discussed.
Currently, it’s difficult to manufacture large area grating and multiple smaller pieces of grating blocks splice large area gratings.The grating blocks will slightly in splicing process. This paper analyzes the splicing grating’s normal deformation characteristics, builds the theoretical model of deformation, and calculates and analyses the case of two grating blocks splicing. It is found the light field diffraction caused by a tiny deformation can not be ignores. The tolerance of grating mechanical measures to prevent deformation are discussed.
2010,
22.
Abstract:
A method for effectively increasing mode field diameter (MFD) of photonic crystal fibers (PCFs) is demonstrated in this paper. Air holes in the cladding of a PCF will be collapse when the PCF is heated due to surface tension. Theoretical and experimental results show that energy loss is very low if the transition connecting the original PCF and the collapsed section is adiabatic. The collapse of air holes can effectively increase the MFD of PCFs. The increase of MFD can not only evidently enhance optical coupling efficiency and surface damage limit, but also apparently reduce splicing loss caused by the mismatch of MFDs with other conventional step fibers.
A method for effectively increasing mode field diameter (MFD) of photonic crystal fibers (PCFs) is demonstrated in this paper. Air holes in the cladding of a PCF will be collapse when the PCF is heated due to surface tension. Theoretical and experimental results show that energy loss is very low if the transition connecting the original PCF and the collapsed section is adiabatic. The collapse of air holes can effectively increase the MFD of PCFs. The increase of MFD can not only evidently enhance optical coupling efficiency and surface damage limit, but also apparently reduce splicing loss caused by the mismatch of MFDs with other conventional step fibers.
2010,
22.
Abstract:
Jones matrix of cube corner prism is deduced by means of ray tracing, and polarization model of cube corner prism is founded. The influence on polarization of incident polarized light by cube corner prism is analyzed. It is found that there exists special polarization azimuth at an incidence zone of cube corner prism, at which the incident linearly polarized light is still linearly polarized after being reflected by cube corner prism. A laser resonator with linearly polarized light is designed using this characteristic, thus the electric-optical Q-switch can be used in it. The beam quality of output laser is unaffected by the vertex and edge of cube corner prism. A laser developed based on the resonator can output energy above 300 mJ at 10 Hz, and the beam quality factor is about 2.
Jones matrix of cube corner prism is deduced by means of ray tracing, and polarization model of cube corner prism is founded. The influence on polarization of incident polarized light by cube corner prism is analyzed. It is found that there exists special polarization azimuth at an incidence zone of cube corner prism, at which the incident linearly polarized light is still linearly polarized after being reflected by cube corner prism. A laser resonator with linearly polarized light is designed using this characteristic, thus the electric-optical Q-switch can be used in it. The beam quality of output laser is unaffected by the vertex and edge of cube corner prism. A laser developed based on the resonator can output energy above 300 mJ at 10 Hz, and the beam quality factor is about 2.
2010,
22.
Abstract:
Experiments are conducted in a small transonic wind tunnel to investigate the impacts of the high-speed flow on the transmission features of light beam. Aberrated wavefronts of light beam travelling through the flow field in the wind tunnel test section with nominal Mach numbers 0.7, 2.0, 3.0 are measured by a Shack-Hartmann wavefront sensor based optical system. Some interesting results including the peak variation (PV), the root of mean square (RMS) and the far-field focal spot are obtained, which suggest that the influence of high-speed flow field increases with the increased flow speed, and the related aberration of wavefront grows rapidly especially when the Mach number is greater than 3.0. Thus it is essential to eliminate the severe disturbance of the flow field in the test section
Experiments are conducted in a small transonic wind tunnel to investigate the impacts of the high-speed flow on the transmission features of light beam. Aberrated wavefronts of light beam travelling through the flow field in the wind tunnel test section with nominal Mach numbers 0.7, 2.0, 3.0 are measured by a Shack-Hartmann wavefront sensor based optical system. Some interesting results including the peak variation (PV), the root of mean square (RMS) and the far-field focal spot are obtained, which suggest that the influence of high-speed flow field increases with the increased flow speed, and the related aberration of wavefront grows rapidly especially when the Mach number is greater than 3.0. Thus it is essential to eliminate the severe disturbance of the flow field in the test section
2010,
22.
Abstract:
Near-infrared laser diode arrays (LDA) are usually utilized as illuminated source for active laser illumination technology. The severe red exposure of 808nm LDA deteriorates its potential for military application. Due to the low response of CMOS to light beyond 900nm, LDA with 880nm wavelength is a good candidate for active laser illumination. The 880 nm LDA has been chosen as a new type of laser active illumination source. As the beam of the high-power LDA has large divergence and uneveness, the 880 nm LDA can not be used directly for active illumination. Thus high power 880 nm fiber-coupled diode lasers have been developed with a pair of micro step-mirrors for beam shaping. As a result, output power about 44.9 W of the fiber-coupled laser diode module is achieved, and electro-optical con
Near-infrared laser diode arrays (LDA) are usually utilized as illuminated source for active laser illumination technology. The severe red exposure of 808nm LDA deteriorates its potential for military application. Due to the low response of CMOS to light beyond 900nm, LDA with 880nm wavelength is a good candidate for active laser illumination. The 880 nm LDA has been chosen as a new type of laser active illumination source. As the beam of the high-power LDA has large divergence and uneveness, the 880 nm LDA can not be used directly for active illumination. Thus high power 880 nm fiber-coupled diode lasers have been developed with a pair of micro step-mirrors for beam shaping. As a result, output power about 44.9 W of the fiber-coupled laser diode module is achieved, and electro-optical con
2010,
22.
Abstract:
In order to increase the lead-free laser soldering speed, the laser parameters, properties of solder and substrate, laser soldering system and other influencing factors of the lead-free laser soldering are studied. The research shows that once the laser, the solder and the substrate are given, a laser soldering system equipped with two galvanometer scanners and an f-theta lens has obvious advantages in soldering speed as compared with the traditional laser soldering system with moving worktable or laser head, because the reflection of the laser beam through the scanning galvanometers overcomes the restriction of the mechanical inertia of the laser head and worktable. In addition, the path that laser beam has scanned in the process of soldering is optimized. The optimization can greatly sho
In order to increase the lead-free laser soldering speed, the laser parameters, properties of solder and substrate, laser soldering system and other influencing factors of the lead-free laser soldering are studied. The research shows that once the laser, the solder and the substrate are given, a laser soldering system equipped with two galvanometer scanners and an f-theta lens has obvious advantages in soldering speed as compared with the traditional laser soldering system with moving worktable or laser head, because the reflection of the laser beam through the scanning galvanometers overcomes the restriction of the mechanical inertia of the laser head and worktable. In addition, the path that laser beam has scanned in the process of soldering is optimized. The optimization can greatly sho
2010,
22.
Abstract:
A new phenomenon about crosstalk effect of CCD was discovered in the experiment of laser irradiating the interline transfer CCD camera. It is that a gap, adjoining the upper side of the main spot, appears on the crosstalk line and becomes smaller when laser becomes more intense. Through the analysis on the structure and process of interline transfer CCD image sensor, a new crosstalk mechanism is given to explain the phenomenon. In the process of vertical transfer action, the overflowing of signal charges in integral well to vertical CCD register makes the crosstalk line. When readout transfer action empties the integral well, the integral well needs time to be refilled, during which no signal charge overflows to vertical CCD register. While the main signal charge package that makes the ma
A new phenomenon about crosstalk effect of CCD was discovered in the experiment of laser irradiating the interline transfer CCD camera. It is that a gap, adjoining the upper side of the main spot, appears on the crosstalk line and becomes smaller when laser becomes more intense. Through the analysis on the structure and process of interline transfer CCD image sensor, a new crosstalk mechanism is given to explain the phenomenon. In the process of vertical transfer action, the overflowing of signal charges in integral well to vertical CCD register makes the crosstalk line. When readout transfer action empties the integral well, the integral well needs time to be refilled, during which no signal charge overflows to vertical CCD register. While the main signal charge package that makes the ma
2010,
22.
Abstract:
A nano and sub-nanosecond optical image framing recording system is presented here to meet the photography demands of 108～1010 Hz frequency in extreme conditions, such as laser flyer and Z-pinch. The overall system design and its principle are introduced. Several key techniques and solutions (such as precise synchronization, high voltage pulser etc). are put forward. The precise synchronization of sub-systems is carried out by a microcomputer and some precise delay units. Nano and sub-nanosecond rise time high voltage pulses are provided by an avalanche transistor array. Picosecond level time delay is generated by 8-bit programmable analog delay chip DS1023-25 and FPGA. Some key experiments have been completed and the experiment results such as 4 000 V high voltage pulse of rise time less
A nano and sub-nanosecond optical image framing recording system is presented here to meet the photography demands of 108～1010 Hz frequency in extreme conditions, such as laser flyer and Z-pinch. The overall system design and its principle are introduced. Several key techniques and solutions (such as precise synchronization, high voltage pulser etc). are put forward. The precise synchronization of sub-systems is carried out by a microcomputer and some precise delay units. Nano and sub-nanosecond rise time high voltage pulses are provided by an avalanche transistor array. Picosecond level time delay is generated by 8-bit programmable analog delay chip DS1023-25 and FPGA. Some key experiments have been completed and the experiment results such as 4 000 V high voltage pulse of rise time less
2010,
22.
Abstract:
To improve the precision and effective spectrum width of wavefront power spectrum density(PSD) at mid-spatial scale, double linear interpolation and six-sample-wide interpolation are proposed to patch invalid points and reduce aliasing noise, respectively. Double linear interpolation reduces discrete discontinuities and retains spectral structure of the valid areas, without adding visible middle and high spatial frequency errors existing in zero-filled method. Six-sample-wide interpolation effectively separates the signal from the aliasing noise and thus increases the effective spectrum upper limit of PSD from half of Nyquist frequency to Nyquist frequency. The validity of double linear interpolation and six-sample-wide interpolation is verified by computer simulation and experiment.
To improve the precision and effective spectrum width of wavefront power spectrum density(PSD) at mid-spatial scale, double linear interpolation and six-sample-wide interpolation are proposed to patch invalid points and reduce aliasing noise, respectively. Double linear interpolation reduces discrete discontinuities and retains spectral structure of the valid areas, without adding visible middle and high spatial frequency errors existing in zero-filled method. Six-sample-wide interpolation effectively separates the signal from the aliasing noise and thus increases the effective spectrum upper limit of PSD from half of Nyquist frequency to Nyquist frequency. The validity of double linear interpolation and six-sample-wide interpolation is verified by computer simulation and experiment.
2010,
22.
Abstract:
In this paper, modeling study is performed to reveal the plasma flow and heat transfer characteristics of the low-power argon arcjet thruster. The all-speed SIMPLE algorithm is used for the solution of the governing equations. Computed results are presented concerning the temperature, velocity, Mach number and streamline distributions within the thruster nozzle and concerning the current density distributions on the anode-nozzle surface under typical operating conditions. It is found that the heating of the gaseous propellant takes place mainly in the cathode and constrictor regions and the highest plasma temperature appears at the location near the cathode tip where the current density assumes its maximum value. The plasma axial-velocity and temperature profiles along the nozzle axis incr
In this paper, modeling study is performed to reveal the plasma flow and heat transfer characteristics of the low-power argon arcjet thruster. The all-speed SIMPLE algorithm is used for the solution of the governing equations. Computed results are presented concerning the temperature, velocity, Mach number and streamline distributions within the thruster nozzle and concerning the current density distributions on the anode-nozzle surface under typical operating conditions. It is found that the heating of the gaseous propellant takes place mainly in the cathode and constrictor regions and the highest plasma temperature appears at the location near the cathode tip where the current density assumes its maximum value. The plasma axial-velocity and temperature profiles along the nozzle axis incr
2010,
22.
Abstract:
To fabricate high quality hollow glass microspheres (HGMs) for inertial confinement fusion (ICF) targets by sol-gel technology, effects of furnace atmosphere composition on the transformation process from gel particles to HGMs and the resulting quality of HGMs were investigated by numerical simulation and experiments. The results show that the furnace atmosphere composition significantly affects the heat and mass transfer process between particles/microspheres and furnace atmosphere, but the falling velocity of the particles/microspheres in drop-tower furnace changes only slightly with the furnace atmosphere compositions. The heating-up rate of gel particles in heat-absorbing stage increases remarkably with the increase of the content of helium in the furnace atmosphere and increasing the
To fabricate high quality hollow glass microspheres (HGMs) for inertial confinement fusion (ICF) targets by sol-gel technology, effects of furnace atmosphere composition on the transformation process from gel particles to HGMs and the resulting quality of HGMs were investigated by numerical simulation and experiments. The results show that the furnace atmosphere composition significantly affects the heat and mass transfer process between particles/microspheres and furnace atmosphere, but the falling velocity of the particles/microspheres in drop-tower furnace changes only slightly with the furnace atmosphere compositions. The heating-up rate of gel particles in heat-absorbing stage increases remarkably with the increase of the content of helium in the furnace atmosphere and increasing the
2010,
22.
Abstract:
The quasi- monoenergetic proton beam generated from ultra- short ultra- intense laser pulse interacting with ultrathin double- layer target (both the thickness of the substrate layer and that of the acceleration layer are in nanometer scale) is examined by one- dimensional particle-in-cell simulation. The thickness of the substrate and the acceleration layer is crucial to the proton spectrum. The quasi-static electric field becomes stronger as the substrate layer thickness decreases, which results in the enhancement of the maximum proton energy. Reducing the acceleration layer thickness induces a more uniform quasi- static electric field. As a result, the proton spectrum becomes more monoenergetic with nearly unchanged mean energy. The quasi- monoenergetic proton with an energy spread of a
The quasi- monoenergetic proton beam generated from ultra- short ultra- intense laser pulse interacting with ultrathin double- layer target (both the thickness of the substrate layer and that of the acceleration layer are in nanometer scale) is examined by one- dimensional particle-in-cell simulation. The thickness of the substrate and the acceleration layer is crucial to the proton spectrum. The quasi-static electric field becomes stronger as the substrate layer thickness decreases, which results in the enhancement of the maximum proton energy. Reducing the acceleration layer thickness induces a more uniform quasi- static electric field. As a result, the proton spectrum becomes more monoenergetic with nearly unchanged mean energy. The quasi- monoenergetic proton with an energy spread of a
2010,
22.
Abstract:
The imaging characteristic of non-periodic multilayer Kirkpatrick-Baez(KB) microscope is analyzed based on propagation of rays, and contrasted with single layer and periodic multilayer KB microscopes. Compared with single layer KB microscope, multilayer KB microscope has bigger grazing angle, and wider field of view at the same resolution and collection efficiency. The reflectivity and energy resolution of periodic multilayer KB microscope is better than that of non-periodic multilayer KB microscope, but the non-periodic multilayer element has wider angular bandwidth and more uniform reflectivity, which improves the field of view and uniformity of image. The non-periodic multilayer mirrors with a grazing angle of 1.133 0° possess 0.3° angular bandwidth. Backlit by 8 keV X-ray tube, the i
The imaging characteristic of non-periodic multilayer Kirkpatrick-Baez(KB) microscope is analyzed based on propagation of rays, and contrasted with single layer and periodic multilayer KB microscopes. Compared with single layer KB microscope, multilayer KB microscope has bigger grazing angle, and wider field of view at the same resolution and collection efficiency. The reflectivity and energy resolution of periodic multilayer KB microscope is better than that of non-periodic multilayer KB microscope, but the non-periodic multilayer element has wider angular bandwidth and more uniform reflectivity, which improves the field of view and uniformity of image. The non-periodic multilayer mirrors with a grazing angle of 1.133 0° possess 0.3° angular bandwidth. Backlit by 8 keV X-ray tube, the i
2010,
22.
Abstract:
The correctable aberration modes space of the micromacined membrane deformable mirror(MMDM) is constructed through the singular value decomposition of the mirror’s influence function matrix. Analyzing the correction ability and range of MMDM for a set of orthogonal basis modes, a closed-loop iterative control algorithm for MMDM is introduced. By means of low-rank approximation of the influence function matrix, the algorithm can correct the aberration selectively by filtering out some aberration modes which can not be corrected easily. In experiments, the wavefront from a human eye is used as the incident wavefront of adaptive optics system. The range of the optimal correction mode number is determined by comparing the correction effects for human eye aberration with different numbers of m
The correctable aberration modes space of the micromacined membrane deformable mirror(MMDM) is constructed through the singular value decomposition of the mirror’s influence function matrix. Analyzing the correction ability and range of MMDM for a set of orthogonal basis modes, a closed-loop iterative control algorithm for MMDM is introduced. By means of low-rank approximation of the influence function matrix, the algorithm can correct the aberration selectively by filtering out some aberration modes which can not be corrected easily. In experiments, the wavefront from a human eye is used as the incident wavefront of adaptive optics system. The range of the optimal correction mode number is determined by comparing the correction effects for human eye aberration with different numbers of m
2010,
22.
Abstract:
A Dante spectrometer mirror calibration method is developed by recovery of X-ray benchmarks without installing reflectivity meter chamber and limit space in 4B7B beamline of BSRF. X-ray benchmark line is achieved by three beamlines aiming. High angle precision is realized by collimation, and chamber state surveillant system was adopted. Mirror calibration uncertainty of angle is 1.0 mrad for the experiment. High precise reflectivity curves have been acquired by repeat installation and in four directions of fixed angle mirror.
A Dante spectrometer mirror calibration method is developed by recovery of X-ray benchmarks without installing reflectivity meter chamber and limit space in 4B7B beamline of BSRF. X-ray benchmark line is achieved by three beamlines aiming. High angle precision is realized by collimation, and chamber state surveillant system was adopted. Mirror calibration uncertainty of angle is 1.0 mrad for the experiment. High precise reflectivity curves have been acquired by repeat installation and in four directions of fixed angle mirror.
2010,
22.
Abstract:
A line velocity interferometer for any reflector has been implemented at the Shenguang-Ⅱ laser facility. This instrument is the primary diagnostic for a variety of experiments involving laser-driven shock-wave propagation, materials characterization experiments and shock timing experiments. It measures velocities of interfaces, free surfaces and shock fronts traveling through transparent media. It can measure shock breakout time at temporal resolutions as low as 20 ps, and spatial resolution 10 μm. Experiments were carried out on the Shenguang-Ⅱ laser facility and high quality interference images were obtained.
A line velocity interferometer for any reflector has been implemented at the Shenguang-Ⅱ laser facility. This instrument is the primary diagnostic for a variety of experiments involving laser-driven shock-wave propagation, materials characterization experiments and shock timing experiments. It measures velocities of interfaces, free surfaces and shock fronts traveling through transparent media. It can measure shock breakout time at temporal resolutions as low as 20 ps, and spatial resolution 10 μm. Experiments were carried out on the Shenguang-Ⅱ laser facility and high quality interference images were obtained.
2010,
22.
Abstract:
The preparation of porous anodic aluminum oxide (AAO) templates has been studied with oxalic acid as electrolyte. The morphology of the as-prepared templates has been characterized by field-emission scanning electron microscope (FE-SEM). The pores distributed orderly and uniformly with the diameter ranging from 40 nm to 70 nm. The experimental results indicate that electrolyte concentration, oxidation voltage, oxidation temperature and oxidation time affect the structure of AAO templates. Ordered porous AAO templates can be derived without annealing and finishing. X-ray diffraction (XRD) analysis indicates that the aluminum oxide film is mainly composed of amorphous Al2O3/sub>.
The preparation of porous anodic aluminum oxide (AAO) templates has been studied with oxalic acid as electrolyte. The morphology of the as-prepared templates has been characterized by field-emission scanning electron microscope (FE-SEM). The pores distributed orderly and uniformly with the diameter ranging from 40 nm to 70 nm. The experimental results indicate that electrolyte concentration, oxidation voltage, oxidation temperature and oxidation time affect the structure of AAO templates. Ordered porous AAO templates can be derived without annealing and finishing. X-ray diffraction (XRD) analysis indicates that the aluminum oxide film is mainly composed of amorphous Al2O3/sub>.
2010,
22.
Abstract:
In order to prepare large size multilayer mirrors for extreme ultraviolet, soft X-ray and X-ray applications, the Mo/Si multilayer was deposited on flat substrate in diameter of 120 mm with the substrate scanning over rectangular targets. By adjusting the speed of substrate scanning over sputtering targets, the depositing rate can be controlled, and the uniformity of layer thickness is improved significantly. After deposition, period thicknesses of multilayer on different positions of the mirror were measured by an X-ray diffractometer. The measured results show that, within the diameter of 120 mm, the uniformity of period thickness is within 0.26%. The reflectivities on different positions of the multilayer mirror were measured at the National Synchrotron Radiation Laboratory. The results
In order to prepare large size multilayer mirrors for extreme ultraviolet, soft X-ray and X-ray applications, the Mo/Si multilayer was deposited on flat substrate in diameter of 120 mm with the substrate scanning over rectangular targets. By adjusting the speed of substrate scanning over sputtering targets, the depositing rate can be controlled, and the uniformity of layer thickness is improved significantly. After deposition, period thicknesses of multilayer on different positions of the mirror were measured by an X-ray diffractometer. The measured results show that, within the diameter of 120 mm, the uniformity of period thickness is within 0.26%. The reflectivities on different positions of the multilayer mirror were measured at the National Synchrotron Radiation Laboratory. The results
2010,
22.
Abstract:
It is important to characterize the dynamic hohlraum’s radiation and coupling efficiency in Z-pinch physical experiments. The difficulty in the columned dynamic hohlraums presents unique challenges and opportunities for target fabrication, especially their self-adaptivity. Columned dynamic hohlraums were developed. The low-density CHO foams were assembled and fixed by assistant clamp and their self-sustaining ability. In the condition of small strain, wire-arrays and foams can automatically adapt to the environment change of target chamber, through free rotation and slide in micron-level. The results show that, the dynamic hohlraums meet the requirement of the Z-pinch physics experiment, and is self-adaptive on the Angara-5-1 facility. The maximal X-ray temperature is 62.7 eV, and the res
It is important to characterize the dynamic hohlraum’s radiation and coupling efficiency in Z-pinch physical experiments. The difficulty in the columned dynamic hohlraums presents unique challenges and opportunities for target fabrication, especially their self-adaptivity. Columned dynamic hohlraums were developed. The low-density CHO foams were assembled and fixed by assistant clamp and their self-sustaining ability. In the condition of small strain, wire-arrays and foams can automatically adapt to the environment change of target chamber, through free rotation and slide in micron-level. The results show that, the dynamic hohlraums meet the requirement of the Z-pinch physics experiment, and is self-adaptive on the Angara-5-1 facility. The maximal X-ray temperature is 62.7 eV, and the res
2010,
22.
Abstract:
The preparation of poly(vinylcyclohexane) (PVCH) foam has been investigated via the thermally-induced phase separation technique and the freeze-drying technique. Polystyrene was saturated using heterogeneous hydrogenation techniques to prepare PVCH. Then low density foams were successfully prepared with the cyclohexane/dioxane solvent and a series of PVCH solutions with different concentrations, by the thermally-induced phase separation technique and the freeze-drying technique. The relation between polymer concentration and foam density was analyzed. The results show that polymer concentration has a good linear relationship with the actual density of PVCH foams and there is a fixed difference between the actual density and theoretic density, thus effectual control on the density of foams
The preparation of poly(vinylcyclohexane) (PVCH) foam has been investigated via the thermally-induced phase separation technique and the freeze-drying technique. Polystyrene was saturated using heterogeneous hydrogenation techniques to prepare PVCH. Then low density foams were successfully prepared with the cyclohexane/dioxane solvent and a series of PVCH solutions with different concentrations, by the thermally-induced phase separation technique and the freeze-drying technique. The relation between polymer concentration and foam density was analyzed. The results show that polymer concentration has a good linear relationship with the actual density of PVCH foams and there is a fixed difference between the actual density and theoretic density, thus effectual control on the density of foams
2010,
22.
Abstract:
A novel radial line power divider using single-circled probe coupling is proposed to realize the equalamplitude in-phase multiport power division of the high power microwave. An S-band 16-port power divider is designed by analyzing the coupling characteristics of the new probe. Numerical simulation and experimental measurement are conducted for the power divider. The experiment result shows that in the frequency range of 2.55 to 3.15 GHz, the voltage standing wave ratio (VSWR) is below 1.4, the insertion loss is below 0.3 dB, the amplitude imbalance is within ±0.5 dB, and the phase imbalance is within ±5°, which proves that the power divider can realize the equal-amplitude inphase power division over a wide frequency range．
A novel radial line power divider using single-circled probe coupling is proposed to realize the equalamplitude in-phase multiport power division of the high power microwave. An S-band 16-port power divider is designed by analyzing the coupling characteristics of the new probe. Numerical simulation and experimental measurement are conducted for the power divider. The experiment result shows that in the frequency range of 2.55 to 3.15 GHz, the voltage standing wave ratio (VSWR) is below 1.4, the insertion loss is below 0.3 dB, the amplitude imbalance is within ±0.5 dB, and the phase imbalance is within ±5°, which proves that the power divider can realize the equal-amplitude inphase power division over a wide frequency range．
2010,
22.
Abstract:
A novel Smith-Purcell interaction structure is presented. It is a coaxial structure including the outer curved mirrors and the middle cylindrical gratings of arbitrary shaped section. Inverting the curved mirrors and changing the position of gratings turn the structure into the improved one, in which greater current can be obtained with bigger-radius ring beam. And the radiation power increases by one order of magnitude. Theoretical analyses and numerical simulation results indicate that coherent radiation with peak power of a few hundred of MW can be achieved from the improved experimental model．
A novel Smith-Purcell interaction structure is presented. It is a coaxial structure including the outer curved mirrors and the middle cylindrical gratings of arbitrary shaped section. Inverting the curved mirrors and changing the position of gratings turn the structure into the improved one, in which greater current can be obtained with bigger-radius ring beam. And the radiation power increases by one order of magnitude. Theoretical analyses and numerical simulation results indicate that coherent radiation with peak power of a few hundred of MW can be achieved from the improved experimental model．
2010,
22.
Abstract:
A new type of X-band horn feed has been designed for the dielectric breakdown experiment of high power microwave(HPM) feed output window. The feed is made of a horn of variable flare angle and a movable dielectric cover. By adjusting the distance between the horn face and the dielectric cover, the electric field on the dielectric cover can be changed. Numerical simulation results show that under the VSWR less than 1.15 and E-plane being equal to H-plane, the variation of electric field intensity is about 32.6 kV·cm-1 to 87 kV·cm-1 for the distance changing from 0 mm to 400 mm. The need of electric field variation for dielectric breakdown is satisfied, when the degree of vacuum is ３×１０-3 Pa, and the pulse width is 20 ns. The experiment device is designed and processed according to the
A new type of X-band horn feed has been designed for the dielectric breakdown experiment of high power microwave(HPM) feed output window. The feed is made of a horn of variable flare angle and a movable dielectric cover. By adjusting the distance between the horn face and the dielectric cover, the electric field on the dielectric cover can be changed. Numerical simulation results show that under the VSWR less than 1.15 and E-plane being equal to H-plane, the variation of electric field intensity is about 32.6 kV·cm-1 to 87 kV·cm-1 for the distance changing from 0 mm to 400 mm. The need of electric field variation for dielectric breakdown is satisfied, when the degree of vacuum is ３×１０-3 Pa, and the pulse width is 20 ns. The experiment device is designed and processed according to the
2010,
22.
Abstract:
Ray-tracing is a key step to apply uniform geometrical theory of diffraction (UTD) in solving the problems of radiating and scattering by electrically large objects. An equation of one variable and four order for reflection points on spheres was deduced according to the reflection principle. Some reflection points were got based on the equation, and the far field pattern of a half-wave dipole near a sphere-cylinder model was given. The UTD result is proved correct by comparing it with the FEKO result. Simultaneously the tracing time is dramatically reduced and the operational precision is improved.
Ray-tracing is a key step to apply uniform geometrical theory of diffraction (UTD) in solving the problems of radiating and scattering by electrically large objects. An equation of one variable and four order for reflection points on spheres was deduced according to the reflection principle. Some reflection points were got based on the equation, and the far field pattern of a half-wave dipole near a sphere-cylinder model was given. The UTD result is proved correct by comparing it with the FEKO result. Simultaneously the tracing time is dramatically reduced and the operational precision is improved.
2010,
22.
Abstract:
The PIN diode under high power microwave is simulated by solving the semiconductor equations numerically. The influence of pulse width on the diode’s burnout is studied. The results show that the pulse power for burnout is nearly inversely proportional to the pulse width, if the pulse width is between several nanoseconds and microseconds. This phenomenon is also analyzed on the basis of Leenov’s model and Thevinen’s theorem. If the pulse width is changed from nanoseconds to microseconds, the thermal effect of the device changes from thermal insulation to thermal conduction and the absorbed power changes from proportional to the incident power to proportion to its square root, both of which lead to the influence of the pulse width.
The PIN diode under high power microwave is simulated by solving the semiconductor equations numerically. The influence of pulse width on the diode’s burnout is studied. The results show that the pulse power for burnout is nearly inversely proportional to the pulse width, if the pulse width is between several nanoseconds and microseconds. This phenomenon is also analyzed on the basis of Leenov’s model and Thevinen’s theorem. If the pulse width is changed from nanoseconds to microseconds, the thermal effect of the device changes from thermal insulation to thermal conduction and the absorbed power changes from proportional to the incident power to proportion to its square root, both of which lead to the influence of the pulse width.
2010,
22.
Abstract:
The limitations of conventional methods used to measure cable's shielding effectiveness are analyzed. The measurement of shielding effectiveness of cable with electromagnetic radiation method is presented based on the reciprocity theorem. According to the theorem and the definition of shielding effectiveness, the method can be used to measure cable's shielding effectiveness through the measurement of radiated field instead of the measurement of coupling field. The electromagnetic radiation method was used to measure the shielding effectiveness of cable with SYV50-5 cable for electromagnetic pulse. The measurement proves to be very efficient in cable’s shielding effectiveness test. As it has no special requirements but linearity on the media space, the reciprocity theorem can be applied re
The limitations of conventional methods used to measure cable's shielding effectiveness are analyzed. The measurement of shielding effectiveness of cable with electromagnetic radiation method is presented based on the reciprocity theorem. According to the theorem and the definition of shielding effectiveness, the method can be used to measure cable's shielding effectiveness through the measurement of radiated field instead of the measurement of coupling field. The electromagnetic radiation method was used to measure the shielding effectiveness of cable with SYV50-5 cable for electromagnetic pulse. The measurement proves to be very efficient in cable’s shielding effectiveness test. As it has no special requirements but linearity on the media space, the reciprocity theorem can be applied re
2010,
22.
Abstract:
A new style of monopole antenna is put forward, along with the design idea and structure model. The antenna fed by a coaxial line is top-loaded with a U-type load. Simulation and experiments have been conducted. The simulated results show that this antenna can radiate axial microwaves, it’s Gain is 8.33dBi, the axial ratio is －69.64 dB, the reflectance is 0.034, in the range of 3.83 GHz to 4.50 GHz , the reflectance is below 0.10. The experimental results show that it’s gain is 8.116 dBi, the VSWR is 1.098 at 4.0G Hz, in the range of 3.75 GHz to 4.50 GHz , the VSWR is below 1.2, the results of experiment consistent with the simulated results, validated each other．
A new style of monopole antenna is put forward, along with the design idea and structure model. The antenna fed by a coaxial line is top-loaded with a U-type load. Simulation and experiments have been conducted. The simulated results show that this antenna can radiate axial microwaves, it’s Gain is 8.33dBi, the axial ratio is －69.64 dB, the reflectance is 0.034, in the range of 3.83 GHz to 4.50 GHz , the reflectance is below 0.10. The experimental results show that it’s gain is 8.116 dBi, the VSWR is 1.098 at 4.0G Hz, in the range of 3.75 GHz to 4.50 GHz , the VSWR is below 1.2, the results of experiment consistent with the simulated results, validated each other．
2010,
22.
Abstract:
Some thermal analysis results of several heating structures for thermionic cathode electron gun by using ANSYS code and COMSOL code were presented in this paper, and some instructions for heating structure design were obtained. A series of heating structures of thermionic cathode were tested in experiments, verifying the results of the thermal analysis, and so an efficiency heating structure was attained. In this structure, at a heating power about 100 W, the temperature of cathode was more than 1 900 K which meets at the working temperature required by Ir-Ce cathode. Under a temperature of 1 800 K and the electric field on the cathode surface of 3.6×106 V/m, the Ir-Ce cathode gives a maximum emission current of 1.04 A and the emission current density of 13 A/cm2.
Some thermal analysis results of several heating structures for thermionic cathode electron gun by using ANSYS code and COMSOL code were presented in this paper, and some instructions for heating structure design were obtained. A series of heating structures of thermionic cathode were tested in experiments, verifying the results of the thermal analysis, and so an efficiency heating structure was attained. In this structure, at a heating power about 100 W, the temperature of cathode was more than 1 900 K which meets at the working temperature required by Ir-Ce cathode. Under a temperature of 1 800 K and the electric field on the cathode surface of 3.6×106 V/m, the Ir-Ce cathode gives a maximum emission current of 1.04 A and the emission current density of 13 A/cm2.
2010,
22.
Abstract:
The Marx solid-state modulator is a Marx-type electrical circuit designed to generate high voltage impulse for klystrons, which uses integrated gate bipolar transistors (IGBT) as switch. Because of the advantages, which are low cost, high availability and small size, the Marx modulator can circumvent the need of the modulator for International Linear Collider(ILC). This article briefly introduces the Marx cell, including the IGBT switch, the energy storage capacitors, HV power supply and the Marx control system. The Marx cell has passed the 12 kV test. It could be helpful for the modular production of the cell and the realization of multi-cells．
The Marx solid-state modulator is a Marx-type electrical circuit designed to generate high voltage impulse for klystrons, which uses integrated gate bipolar transistors (IGBT) as switch. Because of the advantages, which are low cost, high availability and small size, the Marx modulator can circumvent the need of the modulator for International Linear Collider(ILC). This article briefly introduces the Marx cell, including the IGBT switch, the energy storage capacitors, HV power supply and the Marx control system. The Marx cell has passed the 12 kV test. It could be helpful for the modular production of the cell and the realization of multi-cells．
2010,
22.
Abstract:
The responses of wires in a cylinder cavity caused by system generated electromagnetic pulse (SGEMP) comprehensive environment were simulated with FDTD, PIC methods and Holland thin line algorithm. The comprehensive environment includes transmitted X-ray, forward electrons and SGEMP field. The numerical results indicate that the biggest responses are caused by transmitted X-ray, and the smallest responses are caused by forward electrons. The response polarities of transmitted X-ray and forward electrons are opposite, and the response polarity of SGEMP field is related with the distribution of the field. Thus the transmitted X-ray would be the first concern in wires protection in the comprehensive environment.
The responses of wires in a cylinder cavity caused by system generated electromagnetic pulse (SGEMP) comprehensive environment were simulated with FDTD, PIC methods and Holland thin line algorithm. The comprehensive environment includes transmitted X-ray, forward electrons and SGEMP field. The numerical results indicate that the biggest responses are caused by transmitted X-ray, and the smallest responses are caused by forward electrons. The response polarities of transmitted X-ray and forward electrons are opposite, and the response polarity of SGEMP field is related with the distribution of the field. Thus the transmitted X-ray would be the first concern in wires protection in the comprehensive environment.
2010,
22.
Abstract:
The experiment phenomenon in a small-scale space when a kind of silicon diode is in the over-current state is described and explained through the voltage-regulated switch model. The relaxation oscillation is proved through temporal behavior of the thin-beam drift in a infinite space. Moreover, the simulation made with nonlinear equation mathematical model, which is applicable to chaos, demonstrates that under certain initial normalized current values and parameters, the simulation results are consistent with the experimental phenomena.
The experiment phenomenon in a small-scale space when a kind of silicon diode is in the over-current state is described and explained through the voltage-regulated switch model. The relaxation oscillation is proved through temporal behavior of the thin-beam drift in a infinite space. Moreover, the simulation made with nonlinear equation mathematical model, which is applicable to chaos, demonstrates that under certain initial normalized current values and parameters, the simulation results are consistent with the experimental phenomena.
2010,
22.
Abstract:
The design and primary experiment of the digital transverse bunch-by-bunch feedback system in Hefei light source are introduced. This transverse feedback system was developed to conquer the transverse coupled-bunch instabilities. It employed direct sampling front-end to simplify the electric circuits and tuning work. Because of the close tunes of horizontal and vertical directions. The FPGA code of the digital feedback processor was reprogramed to fulfill two-independent-feedback in one-processor. Through the beam test, the digital feedback system could suppress the transverse instabilities, and increase the injection beam current.
The design and primary experiment of the digital transverse bunch-by-bunch feedback system in Hefei light source are introduced. This transverse feedback system was developed to conquer the transverse coupled-bunch instabilities. It employed direct sampling front-end to simplify the electric circuits and tuning work. Because of the close tunes of horizontal and vertical directions. The FPGA code of the digital feedback processor was reprogramed to fulfill two-independent-feedback in one-processor. Through the beam test, the digital feedback system could suppress the transverse instabilities, and increase the injection beam current.
2010,
22.
Abstract:
Two in-vacuum undulators IVU25s and one elliptically polarized undulator EPU100 have been developed for the Shanghai Synchrotron Radiation Facility (SSRF). Two IVU25s with the same hybrid design contain about 636 Sm2Co17sub> magnet blocks with the dimension of 65 mm×25 mm×8.965 mm. The EPU100 of the APPLE-Ⅱ type contains about 668 NdFeB magnet blocks with the dimension of 35 mm×35 mm×25 mm. This paper presents the development of these magnet blocks, points out the basic factors which affect remanence distribution, magnetization deviation angle and mechanical dimension precision, and analyzes the basic principles. The magnetic properties, magnetic field quality and mechanical dimension precision of the developed magnet blocks satisfy the specifications of SSRF initial u
Two in-vacuum undulators IVU25s and one elliptically polarized undulator EPU100 have been developed for the Shanghai Synchrotron Radiation Facility (SSRF). Two IVU25s with the same hybrid design contain about 636 Sm2Co17sub> magnet blocks with the dimension of 65 mm×25 mm×8.965 mm. The EPU100 of the APPLE-Ⅱ type contains about 668 NdFeB magnet blocks with the dimension of 35 mm×35 mm×25 mm. This paper presents the development of these magnet blocks, points out the basic factors which affect remanence distribution, magnetization deviation angle and mechanical dimension precision, and analyzes the basic principles. The magnetic properties, magnetic field quality and mechanical dimension precision of the developed magnet blocks satisfy the specifications of SSRF initial u
2010,
22.
Abstract:
The analysis of power density spectrum (PDS) and integral PDS has been implemented for orbit noise analysis in the Shanghai Synchrotron Radiation Facility(SSRF) storage ring. The beam position monitor signal processing in Liberas, which are the orbit measurement electronics, and the PDS calculation algorithm (Welch method) are described in this paper. Then the measured orbit noise PDS and integral PDS are presented. The result indicates that the main orbit noise sources are ground vibration, girder resonant vibration and 50 Hz power supply noise. The orbit noise analysis is useful to reduce orbit noise and increase orbit stability.
The analysis of power density spectrum (PDS) and integral PDS has been implemented for orbit noise analysis in the Shanghai Synchrotron Radiation Facility(SSRF) storage ring. The beam position monitor signal processing in Liberas, which are the orbit measurement electronics, and the PDS calculation algorithm (Welch method) are described in this paper. Then the measured orbit noise PDS and integral PDS are presented. The result indicates that the main orbit noise sources are ground vibration, girder resonant vibration and 50 Hz power supply noise. The orbit noise analysis is useful to reduce orbit noise and increase orbit stability.
2010,
22.
Abstract:
A new high brightness injector based on a new photocathode RF electron gun is planned to be installed at Hefei light source. To get high quality electron bunch, precise control of beam position is required. The positional resolution of the beam position monitor (BPM) system designed for RF electron gun should be higher than 10 μm. A new type of cavity BPM with racetrack cavity is designed. The racetrack cavity is a cavity with a racetrack cross section, so that it has a pair of dipole modes with different resonant frequency and fixed polarization direction. The cross-talk problem is then solved. The 3D model of the cavity is simulated in MWS, and the theoretical performance of racetrack BPM and the optimization method are analysed. The theoretical resolution of racetrack cavity BPM can be
A new high brightness injector based on a new photocathode RF electron gun is planned to be installed at Hefei light source. To get high quality electron bunch, precise control of beam position is required. The positional resolution of the beam position monitor (BPM) system designed for RF electron gun should be higher than 10 μm. A new type of cavity BPM with racetrack cavity is designed. The racetrack cavity is a cavity with a racetrack cross section, so that it has a pair of dipole modes with different resonant frequency and fixed polarization direction. The cross-talk problem is then solved. The 3D model of the cavity is simulated in MWS, and the theoretical performance of racetrack BPM and the optimization method are analysed. The theoretical resolution of racetrack cavity BPM can be
2010,
22.
Abstract:
In terms of the features of flash X-ray radiographs, the typical edge detection algorithm in digital image processing can only provide thick edges and is noise susceptibile. Thus an edge detection method based on Facet model for detonation experiment images is proposed. This method absorbs the merits of its congeneric method and introduces orthogonal basis to simplify operation. It uses surface fitting methods to approximate locally the image intensity function, and then makes decisions regarding the edge locations using the partial derivatives of the fitted surface. The result shows that the obtained edges of the image are thin, smooth and continuous. The algorithm has a better immunity to the noise jamming of images, and can give accurate localization for isolated edges.
In terms of the features of flash X-ray radiographs, the typical edge detection algorithm in digital image processing can only provide thick edges and is noise susceptibile. Thus an edge detection method based on Facet model for detonation experiment images is proposed. This method absorbs the merits of its congeneric method and introduces orthogonal basis to simplify operation. It uses surface fitting methods to approximate locally the image intensity function, and then makes decisions regarding the edge locations using the partial derivatives of the fitted surface. The result shows that the obtained edges of the image are thin, smooth and continuous. The algorithm has a better immunity to the noise jamming of images, and can give accurate localization for isolated edges.
Experimental verification of negative refractive phenomena of photonic crystal in 10.6 μm wavelength
2010,
22.
Abstract:
A real-time detection system in 10.6 μm wavelength is introduced which is applied to experimental verification of negative refractive phenomena in photonic crystal at optical frequencies. The system is controlled by computer and it can move accurately and perform real-time sampling and drawing of the power of the refractive light automatically. The experimental system is credible and accurate. And the results of the experiment conform to the simulation result.
A real-time detection system in 10.6 μm wavelength is introduced which is applied to experimental verification of negative refractive phenomena in photonic crystal at optical frequencies. The system is controlled by computer and it can move accurately and perform real-time sampling and drawing of the power of the refractive light automatically. The experimental system is credible and accurate. And the results of the experiment conform to the simulation result.
2010,
22.
Abstract:
The uncertainty in delay and jitter measurement has been evaluated for the laser-triggered switch in the Z-pinch primary test stand (PTS) prototype module. The delay is defined as the time difference between the 10% amplitude points in rise edges of laser signal and dI/dt of the switch. A line can be fitted from the rise edge of the dI/dt waveform, whose slope determines the influence of amplitude measurement’s uncertainty on delay measurement's uncertainty. Thus the frequency response uncertainty of the measure system is included in the linear function, and the math model of delay uncertainty is founded from the linear function modified with the uncertainty from the time resolution of the digital oscillograph. The model of jitter uncertainty is founded from the definition of jitter, and
The uncertainty in delay and jitter measurement has been evaluated for the laser-triggered switch in the Z-pinch primary test stand (PTS) prototype module. The delay is defined as the time difference between the 10% amplitude points in rise edges of laser signal and dI/dt of the switch. A line can be fitted from the rise edge of the dI/dt waveform, whose slope determines the influence of amplitude measurement’s uncertainty on delay measurement's uncertainty. Thus the frequency response uncertainty of the measure system is included in the linear function, and the math model of delay uncertainty is founded from the linear function modified with the uncertainty from the time resolution of the digital oscillograph. The model of jitter uncertainty is founded from the definition of jitter, and
2010,
22.
Abstract:
Fused silica substrates were artificially contaminated to estimate the resistance against laser damage. Uniform thin contamination films (about 8 nm thick) were deposited on the substrates by Al sputtering. The laser induced damage threshold (LIDT) was tested at 355 nm with a 6.8 ns Nd:YAG laser in the air. Thermal absorption, thickness of the films and surface morphologies of fused silica before and after contamination were investigated by Stanford photo-thermal solutions, ellipsometer and optical microscope, respectively. The damage sites located on the clear fused silica, and on the input and output surface of the contaminated fused silica have been irradiated respectively with 355 nm pulsed laser. Photographs of the growth of the damaged sites have been taken by the microscope on line,
Fused silica substrates were artificially contaminated to estimate the resistance against laser damage. Uniform thin contamination films (about 8 nm thick) were deposited on the substrates by Al sputtering. The laser induced damage threshold (LIDT) was tested at 355 nm with a 6.8 ns Nd:YAG laser in the air. Thermal absorption, thickness of the films and surface morphologies of fused silica before and after contamination were investigated by Stanford photo-thermal solutions, ellipsometer and optical microscope, respectively. The damage sites located on the clear fused silica, and on the input and output surface of the contaminated fused silica have been irradiated respectively with 355 nm pulsed laser. Photographs of the growth of the damaged sites have been taken by the microscope on line,
2010,
22.
Abstract:
Co-based alloy and TiN/Co-based alloy composite coatings were obtained on low carbon steel surface by 5 kW CO2 laser. Microstructure, phases, micro-hardness, and sliding wear resistance of the coatings were studied. The results show that the Co-based alloy coating consists of γ-Co, ε-Co, Cr23C6, and the TiN/Co-based alloy composite coating consists of γ-Co, ε-Co, Cr23C6, TiN, TiC. The Co-based alloy coating is made up of flourishing γ-Co dendrite and eutectic structures. Equiaxed solid solution and fine eutectic structure are observed in the TiN/Co-based alloy composite coating. The influence of TiN particles on microstructure of the Co-based alloy coating is prominent that TiN refines the microstructure by changing it from dendrited to equiaxed grain.
Co-based alloy and TiN/Co-based alloy composite coatings were obtained on low carbon steel surface by 5 kW CO2 laser. Microstructure, phases, micro-hardness, and sliding wear resistance of the coatings were studied. The results show that the Co-based alloy coating consists of γ-Co, ε-Co, Cr23C6, and the TiN/Co-based alloy composite coating consists of γ-Co, ε-Co, Cr23C6, TiN, TiC. The Co-based alloy coating is made up of flourishing γ-Co dendrite and eutectic structures. Equiaxed solid solution and fine eutectic structure are observed in the TiN/Co-based alloy composite coating. The influence of TiN particles on microstructure of the Co-based alloy coating is prominent that TiN refines the microstructure by changing it from dendrited to equiaxed grain.
2010,
22.
Abstract:
An InGaAs/GaAs strained quantum-well was prepared by metal-organic chemical-vapor deposition(MOCVD) on GaAs substrate. The growth condition was chosen and a strained buffer layer(SBL) was adopted during the growth. A quantum-well emitting at 1 054 nm was prepared laser with tilted waveguide. The strained QW laser exhibited threshold current of 9 mA and slope efficiency of 0.4W/A (unused antireflection coating on the facets). The 1 054 nm spectral width of the strained QW laser was 1.6 nm at an injection current of 50 mA. The experimental results indicate: The optimized growth condition and the used strained buffer layer are propitious to significantly improve the laser performance, and the application of strained InGaAs/GaAs quantum-well to laser emitting at 1 054 nm is successful．
An InGaAs/GaAs strained quantum-well was prepared by metal-organic chemical-vapor deposition(MOCVD) on GaAs substrate. The growth condition was chosen and a strained buffer layer(SBL) was adopted during the growth. A quantum-well emitting at 1 054 nm was prepared laser with tilted waveguide. The strained QW laser exhibited threshold current of 9 mA and slope efficiency of 0.4W/A (unused antireflection coating on the facets). The 1 054 nm spectral width of the strained QW laser was 1.6 nm at an injection current of 50 mA. The experimental results indicate: The optimized growth condition and the used strained buffer layer are propitious to significantly improve the laser performance, and the application of strained InGaAs/GaAs quantum-well to laser emitting at 1 054 nm is successful．
2010,
22.
Abstract:
The physical model for the influence of single photon detector on the performance of quantum key distribution (QKD) system is analyzed according to the principle of QKD system and the operation mode of single photon detector. The relationship between the parameters of the single photon detector and the performance of the QKD system is also given. Various kinds of QKD systems are compared to derive a universal formula, which can describe the influence of single photon detector on any QKD scheme. The result shows that less time-slots of the single photon detector in the scheme may help to improve the performance of the QKD system.
The physical model for the influence of single photon detector on the performance of quantum key distribution (QKD) system is analyzed according to the principle of QKD system and the operation mode of single photon detector. The relationship between the parameters of the single photon detector and the performance of the QKD system is also given. Various kinds of QKD systems are compared to derive a universal formula, which can describe the influence of single photon detector on any QKD scheme. The result shows that less time-slots of the single photon detector in the scheme may help to improve the performance of the QKD system.
2010,
22.
Abstract:
The general mechanism of light transmission loss in optical fiber and the effects of optical fiber under γ-ray radiation environment are introduced. In order to measure the pulse γ-ray radiation-induced loss, an experimental measurement system is developed. Two kinds of pulse γ-ray devices with an average photon energy of 0.3 MeV, a pulse width of 25 ns, a dose rate of 2.03×107 Gy·s-1 and an average photon energy of 1.0 MeV, a pulse width of 25 ns, a dose rate of 5.32×109 Gy·s-1 are employed as irradiation sources in the experiment. The transient radiation-induced loss of pulsed γ-ray effecting on single-mode and multi-mode optical fibers has been measured. Optical fiber transmission systems with several different wavelength lasers such a
The general mechanism of light transmission loss in optical fiber and the effects of optical fiber under γ-ray radiation environment are introduced. In order to measure the pulse γ-ray radiation-induced loss, an experimental measurement system is developed. Two kinds of pulse γ-ray devices with an average photon energy of 0.3 MeV, a pulse width of 25 ns, a dose rate of 2.03×107 Gy·s-1 and an average photon energy of 1.0 MeV, a pulse width of 25 ns, a dose rate of 5.32×109 Gy·s-1 are employed as irradiation sources in the experiment. The transient radiation-induced loss of pulsed γ-ray effecting on single-mode and multi-mode optical fibers has been measured. Optical fiber transmission systems with several different wavelength lasers such a
2010,
22.
Abstract:
Through the theoretical analysis and simulation, the effects of impedance on the voltage transfer efficiency, energy transfer efficiency and peak power transfer efficiency when pulse forming network (PFN) discharges to the load directly and through the linear transformer driver (LTD) are discussed. Based on the one-stage LTD module, a series of experiments are carried out by changing the impedance of the load. The experiment show that the maximal energy transfer efficiency of 80.5% is achieved when the impedance of the load equals to the 2.5 Ω impedance of the PFN, with voltage transfer efficiency and peak power transfer efficiency being 84.1% and 73.9% respectively. The voltage transfer efficiency would increase to 99.0% when the impedance of load is 3.4 Ω, with voltage transfer efficie
Through the theoretical analysis and simulation, the effects of impedance on the voltage transfer efficiency, energy transfer efficiency and peak power transfer efficiency when pulse forming network (PFN) discharges to the load directly and through the linear transformer driver (LTD) are discussed. Based on the one-stage LTD module, a series of experiments are carried out by changing the impedance of the load. The experiment show that the maximal energy transfer efficiency of 80.5% is achieved when the impedance of the load equals to the 2.5 Ω impedance of the PFN, with voltage transfer efficiency and peak power transfer efficiency being 84.1% and 73.9% respectively. The voltage transfer efficiency would increase to 99.0% when the impedance of load is 3.4 Ω, with voltage transfer efficie
2010,
22.
Abstract:
This paper summarizes an experimental study of the multi-gap switch for fast linear transformer driver. The self-breakdown voltage testing has been conducted and the relation between self-breakdown voltage and gas pressure was obtained when the switch was filled with dry-air. As the pressure changed from 0 to 0.15 MPa, the self-breakdown voltage increased from 80 kV to 200 kV. An experimental study has been carried out on the triggering feature and discharge distribution property，and the uniform discharge distribution has been acquired after 5 000 shots, which can prolong the life of the switch. The switch filled with 0.15 MPa dry-air had 34.4 ns delay with 1.6 ns jitter operating at 78.5% of self-breakdown voltage and trigger voltage of 70kV. The switch is very simple in structure and as
This paper summarizes an experimental study of the multi-gap switch for fast linear transformer driver. The self-breakdown voltage testing has been conducted and the relation between self-breakdown voltage and gas pressure was obtained when the switch was filled with dry-air. As the pressure changed from 0 to 0.15 MPa, the self-breakdown voltage increased from 80 kV to 200 kV. An experimental study has been carried out on the triggering feature and discharge distribution property，and the uniform discharge distribution has been acquired after 5 000 shots, which can prolong the life of the switch. The switch filled with 0.15 MPa dry-air had 34.4 ns delay with 1.6 ns jitter operating at 78.5% of self-breakdown voltage and trigger voltage of 70kV. The switch is very simple in structure and as
2010,
22.
Abstract:
A high power modulator was built to drive the 100 MW klystron. The line-type topology with deuterium thyratron was adopted to increase its operating reliability. Specifications and structure of the pulse transformer and pulse forming network are presented. Some valuable auxiliary circuits are applied to improve the system stability. The design of the charging circuit is also introduced. Local monitoring and control of the modulator is based on programmable logic controller (PLC), and the control data networking is realized through communication between MPI and PLC. Saber model of the modulator circuit is built, and the simulation results are consistent with experimental ones：1.1 μs rise time, 1.7 μs fall time and 2.5 μs flat top. The modulator produces 450 kV, 600 A pulses, which meet
A high power modulator was built to drive the 100 MW klystron. The line-type topology with deuterium thyratron was adopted to increase its operating reliability. Specifications and structure of the pulse transformer and pulse forming network are presented. Some valuable auxiliary circuits are applied to improve the system stability. The design of the charging circuit is also introduced. Local monitoring and control of the modulator is based on programmable logic controller (PLC), and the control data networking is realized through communication between MPI and PLC. Saber model of the modulator circuit is built, and the simulation results are consistent with experimental ones：1.1 μs rise time, 1.7 μs fall time and 2.5 μs flat top. The modulator produces 450 kV, 600 A pulses, which meet
2010,
22.
Abstract:
To develop a high power pulsed source with high-repetition-rate operation and compact size, a trigger control system design of high voltage generator with inductive isolators is presented. The key techniques to build a control system of pulsed power source using solid-state switches(silicon controlled rectifier) are studied with optic components, driving circuit, and pulse transformer with high dielectric strength as high voltage isolator and optical data link. These techniques are trigger signal high voltage isolation, optical splitter, and pulse transformer parallel link or series link. Design and test results of the control system on single module are presented. Experiments show 32 kV output voltage with 4 kV input charge voltage of 5 stages LC generator, the generators conversion of
To develop a high power pulsed source with high-repetition-rate operation and compact size, a trigger control system design of high voltage generator with inductive isolators is presented. The key techniques to build a control system of pulsed power source using solid-state switches(silicon controlled rectifier) are studied with optic components, driving circuit, and pulse transformer with high dielectric strength as high voltage isolator and optical data link. These techniques are trigger signal high voltage isolation, optical splitter, and pulse transformer parallel link or series link. Design and test results of the control system on single module are presented. Experiments show 32 kV output voltage with 4 kV input charge voltage of 5 stages LC generator, the generators conversion of
2010,
22.
Abstract:
A 4 MV coax-to-triplate multi-channel water dielectric self-breaking switch designed for oil and water section of PTS，the high power pulse device and primary test stand，is investigated on the prototype module of PTS. The switch contains three linear array self-breaking gaps and supporting hardware. The equivalent electric circuits of the prototype module of PTS and the switch are modeled based on the configurations of compositive parts. The results of experiments and simulations are compared at 2.9 MV and 3.3 MV break voltage of the switch. It is indicated that the simulative results agree with that of experiments well. It is important that the parameters of the equivalent electric circuits of the prototype module of PTS and the switch are selected reasonably. The Parameters approach to
A 4 MV coax-to-triplate multi-channel water dielectric self-breaking switch designed for oil and water section of PTS，the high power pulse device and primary test stand，is investigated on the prototype module of PTS. The switch contains three linear array self-breaking gaps and supporting hardware. The equivalent electric circuits of the prototype module of PTS and the switch are modeled based on the configurations of compositive parts. The results of experiments and simulations are compared at 2.9 MV and 3.3 MV break voltage of the switch. It is indicated that the simulative results agree with that of experiments well. It is important that the parameters of the equivalent electric circuits of the prototype module of PTS and the switch are selected reasonably. The Parameters approach to
2010,
22.
Abstract:
The initial state of pinch load in vacuum was monitored successfully in experiments about wire array loads. New and old load configurations were used to carry out contrast studies, and the nanosecond-frame camera was used to record images about different plasma implosion phases. Influences on electrode configuration and the initial state of pinch load were discussed by analysing experimental results. The experimental results show that fixing time was shortened and coaxality was controlled easily by using the new load electrode configuration. They also show that the dispersibility of experimental data decreased by using new load electrode configuration and monitoring the initial state of pinch load in vacuum. The study provides technical support for optimization design of load parameters.
The initial state of pinch load in vacuum was monitored successfully in experiments about wire array loads. New and old load configurations were used to carry out contrast studies, and the nanosecond-frame camera was used to record images about different plasma implosion phases. Influences on electrode configuration and the initial state of pinch load were discussed by analysing experimental results. The experimental results show that fixing time was shortened and coaxality was controlled easily by using the new load electrode configuration. They also show that the dispersibility of experimental data decreased by using new load electrode configuration and monitoring the initial state of pinch load in vacuum. The study provides technical support for optimization design of load parameters.
