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RSS2011 Vol. 23, No. 12
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2011,
23: 1-2.
Abstract:
The principle of multi-beam laser interference lithography patterns was studied according to the electromagnetic theory. The factors affecting the patterns were analyzed by comparing numerical simulations with experimental results. It is found that multi-beam laser interference patterns can be considered as superpositions of multiple parallel stripes which are cosine distributed. The?beams’ polarization direction, incident direction and phase difference are important factors influencing the patterns, which affect the parallel stripes’ amplitude, location, period and orientation severely.
The principle of multi-beam laser interference lithography patterns was studied according to the electromagnetic theory. The factors affecting the patterns were analyzed by comparing numerical simulations with experimental results. It is found that multi-beam laser interference patterns can be considered as superpositions of multiple parallel stripes which are cosine distributed. The?beams’ polarization direction, incident direction and phase difference are important factors influencing the patterns, which affect the parallel stripes’ amplitude, location, period and orientation severely.
2011,
23: 2-3.
Abstract:
The phase of sample point should be calculated to design the computer generated hologram(CGH) for testing off-axis aspheric surface. The normal of the geometric center of off-axis aspheric surface was seen as the detection optical axis through shift and rotation. Then the phase distribution on off-axis aspheric surface was studied by ray tracing, and a calculation method of discrete phase was deduced, as well as the formulas for phase computation in three-dimensional coordinate system. The validity of this method is proven by calculating and comparing the phase distribution of a rotational symmetry aspheric surface. The results show that this method is correct, and the calculation accuracy can meet the requirement of CGH for off-axis aspheric surface test.
The phase of sample point should be calculated to design the computer generated hologram(CGH) for testing off-axis aspheric surface. The normal of the geometric center of off-axis aspheric surface was seen as the detection optical axis through shift and rotation. Then the phase distribution on off-axis aspheric surface was studied by ray tracing, and a calculation method of discrete phase was deduced, as well as the formulas for phase computation in three-dimensional coordinate system. The validity of this method is proven by calculating and comparing the phase distribution of a rotational symmetry aspheric surface. The results show that this method is correct, and the calculation accuracy can meet the requirement of CGH for off-axis aspheric surface test.
2011,
23: 3-8.
Abstract:
The dispersion relation, instable condition, and the dimensionless critical perturbation frequency and gain spectra of modulation instability(MI) are deduced in metamaterials by directly starting from the extended nonlinear propagation equation including saturable nonlinearity, self-steepening and the second-order nonlinear effects and by adopting the linear stability analysis. Variations of the dimensionless gain spectra with the normalized angular frequencies and incident power densities are calculated in the positive refractive-index region of metamaterials. The results show that, in the positive refractive-index region of metamaterials, depending on different normalized angular frequencies and incident power densities, the gain spectra will take on three kinds of forms. Namely, the per
The dispersion relation, instable condition, and the dimensionless critical perturbation frequency and gain spectra of modulation instability(MI) are deduced in metamaterials by directly starting from the extended nonlinear propagation equation including saturable nonlinearity, self-steepening and the second-order nonlinear effects and by adopting the linear stability analysis. Variations of the dimensionless gain spectra with the normalized angular frequencies and incident power densities are calculated in the positive refractive-index region of metamaterials. The results show that, in the positive refractive-index region of metamaterials, depending on different normalized angular frequencies and incident power densities, the gain spectra will take on three kinds of forms. Namely, the per
2011,
23: 4-5.
Abstract:
The fixed range fuse needs to complete a rapid height determination in the flight descent segment of the projectile, and then control the projectiles action precisely. Comparing different height determination methods, this article puts forward a compound height measurement method using pulsed laser and gravity acceleration sensor, and calculates the measurement precision by deep analysis in measurement error. The prototype test on inclined platform shows that the maximum angle error is less than 0.3 under static condition; 0~500 m height determination experiments show that the maximum error between the average measured value and the actual value is 2.5 m, which has no correlation with the target distance.
The fixed range fuse needs to complete a rapid height determination in the flight descent segment of the projectile, and then control the projectiles action precisely. Comparing different height determination methods, this article puts forward a compound height measurement method using pulsed laser and gravity acceleration sensor, and calculates the measurement precision by deep analysis in measurement error. The prototype test on inclined platform shows that the maximum angle error is less than 0.3 under static condition; 0~500 m height determination experiments show that the maximum error between the average measured value and the actual value is 2.5 m, which has no correlation with the target distance.
2011,
23: 5-6.
Abstract:
High energy efficiency and well-distributed output on the surface of the chirped pulse grating are required in the laser pulse compressor with mosaic gratings as the dispersion element. Fresnel-Kirchhoffs diffraction theory is utilized to study the light distribution on the grating surface and the far-field diffraction pattern. The variations of the light intensity on the grating surface and the maximum value of the far-field light intensity influenced by the mosaic grating gap are calculated. It is found that the light distribution is related to the width of the gap for light incidence near the Littrow angle, and the width of the gap should be limited within 0.5 mm. When the diffraction efficiency of the gap increases, the light distribution will be more uniform and the output ener
High energy efficiency and well-distributed output on the surface of the chirped pulse grating are required in the laser pulse compressor with mosaic gratings as the dispersion element. Fresnel-Kirchhoffs diffraction theory is utilized to study the light distribution on the grating surface and the far-field diffraction pattern. The variations of the light intensity on the grating surface and the maximum value of the far-field light intensity influenced by the mosaic grating gap are calculated. It is found that the light distribution is related to the width of the gap for light incidence near the Littrow angle, and the width of the gap should be limited within 0.5 mm. When the diffraction efficiency of the gap increases, the light distribution will be more uniform and the output ener
2011,
23: 6-7.
Abstract:
A method of calibrating CCD camera based on 1-D linear diffraction gratings is presented. With the beam splitting character of the diffraction grating, a series of diffraction sub-spots are formed in the focal plane, different sets of measurement data of the sub-spot peak intensity are syncretized and the calibration of infrared CCD cameras opto-electronic characteristic is completed by fitting the measurement data and the theoretical data. According to the parameters of the laser source and the focal optical system available in the laboratory, a series of 1-D linear diffraction gratings are designed and an infrared CCD camera with an unknown character is calibrated. The presented method has higher light available ratio, and the syncretization of multiple sets of measurement data ex
A method of calibrating CCD camera based on 1-D linear diffraction gratings is presented. With the beam splitting character of the diffraction grating, a series of diffraction sub-spots are formed in the focal plane, different sets of measurement data of the sub-spot peak intensity are syncretized and the calibration of infrared CCD cameras opto-electronic characteristic is completed by fitting the measurement data and the theoretical data. According to the parameters of the laser source and the focal optical system available in the laboratory, a series of 1-D linear diffraction gratings are designed and an infrared CCD camera with an unknown character is calibrated. The presented method has higher light available ratio, and the syncretization of multiple sets of measurement data ex
2011,
23.
Abstract:
A high accuracy algorithm based on one dimensional search which is used for calculating the BFS (best fitting sphere) of high-order optical aspheric surface is proposed, according to the geometric property between the aspheric surface and its BFS. This method can be used to calculate the radius and the center location of the BFS and the asphericity for conicoid and high-order aspheric surface (including concave and convex surfaces). The analysis of calculation examples shows that, this method can reduce the maximum asphericity from 500.8 m to 30 m for high-order aspheric surface, and it can get the same asphericity for conicoid compared to other methods. In addition, it can get better BFS than other methods when used for high-order aspheric surface, and its fast speed and hig
A high accuracy algorithm based on one dimensional search which is used for calculating the BFS (best fitting sphere) of high-order optical aspheric surface is proposed, according to the geometric property between the aspheric surface and its BFS. This method can be used to calculate the radius and the center location of the BFS and the asphericity for conicoid and high-order aspheric surface (including concave and convex surfaces). The analysis of calculation examples shows that, this method can reduce the maximum asphericity from 500.8 m to 30 m for high-order aspheric surface, and it can get the same asphericity for conicoid compared to other methods. In addition, it can get better BFS than other methods when used for high-order aspheric surface, and its fast speed and hig
2011,
23: 8-9.
Abstract:
Due to the low efficiency of testing large-aperture mirrors in the polishing process by sub-aperture stitching technology, the sparse sub-aperture sampling technology was put forward and analyzed. Full aperture maps gained by different sparse sub-aperture sampling and the actual full aperture map were compared. The sparse sub-aperture sampling with a reasonable distribution may achieve the same accuracy as the full aperture test does. Thus the sparse sub-aperture sampling technology could be used in the polishing process to improve test efficiency.
Due to the low efficiency of testing large-aperture mirrors in the polishing process by sub-aperture stitching technology, the sparse sub-aperture sampling technology was put forward and analyzed. Full aperture maps gained by different sparse sub-aperture sampling and the actual full aperture map were compared. The sparse sub-aperture sampling with a reasonable distribution may achieve the same accuracy as the full aperture test does. Thus the sparse sub-aperture sampling technology could be used in the polishing process to improve test efficiency.
2011,
23: 9-10.
Abstract:
According to aimed warheads request of space matching and time matching for fuze, and the relative motion environment of missile target encounter, this paper establishes a optimum detonating delay time model and a optimum detonating azimuth model of pulsed laser position detection fuze system in three mutually perpendicular two-dimensional planes of inertial coordinate system. Quantified and numerical simulation of corresponding space matching and time matching is also performed. The study of time and space matching characteristics for pulsed laser azimuth detection fuze, lays a theoretical foundation for parameter design of appropriate security and detonation control system. The results show that the model has the relationship with projectile target crossing angle, the initia
According to aimed warheads request of space matching and time matching for fuze, and the relative motion environment of missile target encounter, this paper establishes a optimum detonating delay time model and a optimum detonating azimuth model of pulsed laser position detection fuze system in three mutually perpendicular two-dimensional planes of inertial coordinate system. Quantified and numerical simulation of corresponding space matching and time matching is also performed. The study of time and space matching characteristics for pulsed laser azimuth detection fuze, lays a theoretical foundation for parameter design of appropriate security and detonation control system. The results show that the model has the relationship with projectile target crossing angle, the initia
2011,
23: 10-11.
Abstract:
Long-period fiber gratings(LPFGs) with the periods of 100, 200, 300 and 400 m were fabricated in standard telecommunication fibers in air using laser direct writing method. Spectra of the LPFGs from 1 280 nm to 1 680 nm were obtained under different experimental conditions, in which the resonant wavelengths, the maximum transmission losses and the insertion losses were observed. By optimizing the experimental parameters, LPFGs were fabricated with the resonant wavelengths of 1 407, 1 311, 1 669, and 1 551 nm, respectively. The maximum transmission losses were about 24.0 ， 22.3 ， 27.8 , and 23.4 dB, and the insertion losses were about 2.5 ， 1.7 ， 3.2 ， and 2.0 dB, respectively.
Long-period fiber gratings(LPFGs) with the periods of 100, 200, 300 and 400 m were fabricated in standard telecommunication fibers in air using laser direct writing method. Spectra of the LPFGs from 1 280 nm to 1 680 nm were obtained under different experimental conditions, in which the resonant wavelengths, the maximum transmission losses and the insertion losses were observed. By optimizing the experimental parameters, LPFGs were fabricated with the resonant wavelengths of 1 407, 1 311, 1 669, and 1 551 nm, respectively. The maximum transmission losses were about 24.0 ， 22.3 ， 27.8 , and 23.4 dB, and the insertion losses were about 2.5 ， 1.7 ， 3.2 ， and 2.0 dB, respectively.
2011,
23: 11-12.
Abstract:
This paper uses a non-negative least-squares method based on sparse matrix, to solve the dwell time in computer controlled optical surfacing (CCOS) of optical elements with large diameter and microstructure, and the regularization of the method is researched. The simulation results reveal that the large-scale non-negative least-squares method based on sparse matrix has higher accuracy and efficiency, in contrast with the traditional non-negative least-squares method. The RMS of surface residual error converges to 0.067 wavelength, when the method is used to simulate the manufacturing of an optical workpiece with large diameter, microstructures and average surface amplitude of 1.177 6 wavelengths.
This paper uses a non-negative least-squares method based on sparse matrix, to solve the dwell time in computer controlled optical surfacing (CCOS) of optical elements with large diameter and microstructure, and the regularization of the method is researched. The simulation results reveal that the large-scale non-negative least-squares method based on sparse matrix has higher accuracy and efficiency, in contrast with the traditional non-negative least-squares method. The RMS of surface residual error converges to 0.067 wavelength, when the method is used to simulate the manufacturing of an optical workpiece with large diameter, microstructures and average surface amplitude of 1.177 6 wavelengths.
2011,
23: 12-13.
Abstract:
The theory of fiber-based vector-sum microwave photonic phase shifter is investigated. A new structure of the phase shifter is designed and its model is studied. Adjustable optical divider and polarization-maintaining fiber are used in the structure, which can reduce the structural complexity and the coherent interference, and can enhance the controllability of the phase shifter. The effects on the phase and amplitude of the signals of the division factor and the frequency are analyzed. The phase shift above 140 is achieved and the attenuation of the amplitude of the signals can be compensated by power amplifier.
The theory of fiber-based vector-sum microwave photonic phase shifter is investigated. A new structure of the phase shifter is designed and its model is studied. Adjustable optical divider and polarization-maintaining fiber are used in the structure, which can reduce the structural complexity and the coherent interference, and can enhance the controllability of the phase shifter. The effects on the phase and amplitude of the signals of the division factor and the frequency are analyzed. The phase shift above 140 is achieved and the attenuation of the amplitude of the signals can be compensated by power amplifier.
2011,
23: 13-14.
Abstract:
The paper introduces the principle of measurement of super-smooth surface by grazing incidence X-ray scattering (GXRS) method and the experimental facility based on an improved X-ray diffraction device. The scattering diagrams measured from three wafers with different roughness are treated by the first-order vector perturbation theory (FOPT) and the generalized Harvey-Shack theory, respectively. The results indicate that the calculated power spectrum density (PSD) functions are in a good agreement with the results obtained from atomic force microscope. The effects of the slit width of detector and the divergence of incident X-ray on the measurement are also analyzed. It is concluded that the measurement error decreases exponentially with reducing the slit width and the incident divergence,
The paper introduces the principle of measurement of super-smooth surface by grazing incidence X-ray scattering (GXRS) method and the experimental facility based on an improved X-ray diffraction device. The scattering diagrams measured from three wafers with different roughness are treated by the first-order vector perturbation theory (FOPT) and the generalized Harvey-Shack theory, respectively. The results indicate that the calculated power spectrum density (PSD) functions are in a good agreement with the results obtained from atomic force microscope. The effects of the slit width of detector and the divergence of incident X-ray on the measurement are also analyzed. It is concluded that the measurement error decreases exponentially with reducing the slit width and the incident divergence,
2011,
23: 14-15.
Abstract:
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2011,
23: 15-16.
Abstract:
The absolute testing of spherical surfaces with the shift-rotation method is an effective way to test spherical surfaces with high accuracy. In the testing, the spherical surface under test is rotated to N equally spaced positions about the optical axis and the results of testing are averaged, to obtain the rotational asymmetric component. The spherical surface is also shifted to a confocal position with a shift, to derive the rotational symmetric component. Then full surface shape information can be obtained by synthesizing the above rotational asymmetric and rotational symmetric components. The formulas of shift-rotation method are derived and a simulation of the testing is presented. The results of simulation show that the root-mean-square(RMS) of residual figure error is 5.300 0
The absolute testing of spherical surfaces with the shift-rotation method is an effective way to test spherical surfaces with high accuracy. In the testing, the spherical surface under test is rotated to N equally spaced positions about the optical axis and the results of testing are averaged, to obtain the rotational asymmetric component. The spherical surface is also shifted to a confocal position with a shift, to derive the rotational symmetric component. Then full surface shape information can be obtained by synthesizing the above rotational asymmetric and rotational symmetric components. The formulas of shift-rotation method are derived and a simulation of the testing is presented. The results of simulation show that the root-mean-square(RMS) of residual figure error is 5.300 0
2011,
23: 16-17.
Abstract:
Least square method is used to fit power and astigmatism of rectangular pupil wavefront data, which avoids data interpolation of the blank area in circular domain. In the experiments, the maximal difference of power and astigmatism of circular domain data between commercial software and our method is less than 0.005 wavelength, which proves the proposed methods feasibility. For rectangular pupil wavefront data, the differences of astigmatism increase as the rectangle elements length-width ratio increases. Therefore the proposed method is more applicable for rectangular pupil wavefront calculation.
Least square method is used to fit power and astigmatism of rectangular pupil wavefront data, which avoids data interpolation of the blank area in circular domain. In the experiments, the maximal difference of power and astigmatism of circular domain data between commercial software and our method is less than 0.005 wavelength, which proves the proposed methods feasibility. For rectangular pupil wavefront data, the differences of astigmatism increase as the rectangle elements length-width ratio increases. Therefore the proposed method is more applicable for rectangular pupil wavefront calculation.
2011,
23: 17-18.
Abstract:
A mathematical model of the dwell time algorithm based on the optimization theory and matrix equation was established, which aims to minimize the 2-norm or -norm of the residual surface error. In the theory, the dwell time solution meets almost all the requirements of precise computer numerical control (CNC) without any need for extra data processing. Several practical methods were discussed on how to solve the optimization model and obtain an optimal solution. Also analyses of the two algorithms were performed in this paper. The simulations show that both of the two algorithms have high precision. The computation efficiency is crucial for least squares algorithms because it is lower for large computation models. The least squares algorithm is numerically robust, whi
A mathematical model of the dwell time algorithm based on the optimization theory and matrix equation was established, which aims to minimize the 2-norm or -norm of the residual surface error. In the theory, the dwell time solution meets almost all the requirements of precise computer numerical control (CNC) without any need for extra data processing. Several practical methods were discussed on how to solve the optimization model and obtain an optimal solution. Also analyses of the two algorithms were performed in this paper. The simulations show that both of the two algorithms have high precision. The computation efficiency is crucial for least squares algorithms because it is lower for large computation models. The least squares algorithm is numerically robust, whi
2011,
23: 18-19.
Abstract:
A new method of generating ring source by binary grating is described, and the radius and thickness of the source ring can be changed dynamically in either continuous or stepwise fashion. The reason for which the ring source can reduce the coherent noise is given. The relation of the ring sources radius and cavity length with interferogram contrast is deduced. Comparative experiments with the traditional point source show that, the ring source can suppress coherent noises effectively and preserve the fringe contrast. The system intrinsic noise in ring source pattern is less than that in point source one and there is no Newton ring in the phase map in evidence. The improvement of measurement accuracy and repeatability can be achieved with ring source.
A new method of generating ring source by binary grating is described, and the radius and thickness of the source ring can be changed dynamically in either continuous or stepwise fashion. The reason for which the ring source can reduce the coherent noise is given. The relation of the ring sources radius and cavity length with interferogram contrast is deduced. Comparative experiments with the traditional point source show that, the ring source can suppress coherent noises effectively and preserve the fringe contrast. The system intrinsic noise in ring source pattern is less than that in point source one and there is no Newton ring in the phase map in evidence. The improvement of measurement accuracy and repeatability can be achieved with ring source.
2011,
23: 19-20.
Abstract:
This paper analyzes the influence of beams spatial deviation on multibeam interference pattern. The pattern obtained by three beams is shown to be more stable on the whole surface compared with that obtained by four beams. In experiments, the He- Cd laser beam was divided to three beams which were rotationally symmetric and then the three beams were used to expose the photo- resist. The honeycomb lattice with a period of 600 nm and a height of 350 nm was fabricated. The measured data demonstrate that the energy distribution is more uniform and stable by using three- beam interference, which can reduce the accuracy demand of the optical light path for laser interference lithography.
This paper analyzes the influence of beams spatial deviation on multibeam interference pattern. The pattern obtained by three beams is shown to be more stable on the whole surface compared with that obtained by four beams. In experiments, the He- Cd laser beam was divided to three beams which were rotationally symmetric and then the three beams were used to expose the photo- resist. The honeycomb lattice with a period of 600 nm and a height of 350 nm was fabricated. The measured data demonstrate that the energy distribution is more uniform and stable by using three- beam interference, which can reduce the accuracy demand of the optical light path for laser interference lithography.
2011,
23: 20-21.
Abstract:
Taking the flatted Gaussian beam as an example, several definitions of beam paraxiality, i.e. paraxiality estimator, degree of paraxiality, and revised degree of paraxiality, are studied analytically and illustrated numerically. It is shown that there exists a remarkable discrepancy among the three definitions when the waist width- to- wavelength ratio is small, and the paraxiality estimator will lead to a non- physical result. Whereas, the degree of paraxiality and the revised degree of paraxiality provide similar results for intermediate values of waist width- to- wavelength ratio, which are of interest in practice. Thus they both can be used for the description of beam paraxiality.
Taking the flatted Gaussian beam as an example, several definitions of beam paraxiality, i.e. paraxiality estimator, degree of paraxiality, and revised degree of paraxiality, are studied analytically and illustrated numerically. It is shown that there exists a remarkable discrepancy among the three definitions when the waist width- to- wavelength ratio is small, and the paraxiality estimator will lead to a non- physical result. Whereas, the degree of paraxiality and the revised degree of paraxiality provide similar results for intermediate values of waist width- to- wavelength ratio, which are of interest in practice. Thus they both can be used for the description of beam paraxiality.
2011,
23: 21-22.
Abstract:
The terrain matching guidance system equipped with radar altimeter has low detection precision and is susceptible to electromagnetic interference. Moreover, it can not work over the sea. In order to resolve these problems, a scheme of laser altimeter is designed to take the place of the radar altimeter. The technology of diode-pumped solid-state laser is adopted to design laser transmitter, outputting infrared/blue-green dual-wavelength laser. The altimeter with dual-wavelength output can detect both the land terrain and the seabed terrain. To promote the performance of the laser altimeter, the detectors are selected carefully, and the optics system, the scanning system and the signal processing system are designed optimally. The designed laser altimeter features small size, light weight,
The terrain matching guidance system equipped with radar altimeter has low detection precision and is susceptible to electromagnetic interference. Moreover, it can not work over the sea. In order to resolve these problems, a scheme of laser altimeter is designed to take the place of the radar altimeter. The technology of diode-pumped solid-state laser is adopted to design laser transmitter, outputting infrared/blue-green dual-wavelength laser. The altimeter with dual-wavelength output can detect both the land terrain and the seabed terrain. To promote the performance of the laser altimeter, the detectors are selected carefully, and the optics system, the scanning system and the signal processing system are designed optimally. The designed laser altimeter features small size, light weight,
2011,
23: 22-23.
Abstract:
The change in strain of T300/AG80 carbon fiber composite laminated plates were tested under laser irradiation. The strain in three directions of 0,45 and 90 of the samples under laser beams with various radii were recorded by the dynamic strain testing apparatus. With the effects of temperature eliminated, the presented data show that, the strain decreases with the increase of the distance to the center of laser spot. After the laminates are irradiated for 5 seconds, the maximum strain is found in the direction of 90 and is at least 1.5 times larger than the minimum strain in the direction of 0. The thermal stress at every point decreases as the distance to the spot center increases. The experiment process was simulated with finite element analysis softwa
The change in strain of T300/AG80 carbon fiber composite laminated plates were tested under laser irradiation. The strain in three directions of 0,45 and 90 of the samples under laser beams with various radii were recorded by the dynamic strain testing apparatus. With the effects of temperature eliminated, the presented data show that, the strain decreases with the increase of the distance to the center of laser spot. After the laminates are irradiated for 5 seconds, the maximum strain is found in the direction of 90 and is at least 1.5 times larger than the minimum strain in the direction of 0. The thermal stress at every point decreases as the distance to the spot center increases. The experiment process was simulated with finite element analysis softwa
2011,
23: 23-24.
Abstract:
To estimate debond defects of glass fiber composite materials applied in the SRM(Solid Rocket Motor), an active infrared thermography nondestructive testing system was set up. The specimen with known debond defects was stimulated by a pulsed heating source and the surface temperature of the specimen was monitored by the infrared camera. According to the difference of the surface temperature, the defects inside the specimen could be detected. The experiment results were compared with the ultrasonic C-scan ones. The results show that the infrared thermography is a fast and effective inspection method for detecting debond defects with the diameter over 10 mm and depth within 5 mm.
To estimate debond defects of glass fiber composite materials applied in the SRM(Solid Rocket Motor), an active infrared thermography nondestructive testing system was set up. The specimen with known debond defects was stimulated by a pulsed heating source and the surface temperature of the specimen was monitored by the infrared camera. According to the difference of the surface temperature, the defects inside the specimen could be detected. The experiment results were compared with the ultrasonic C-scan ones. The results show that the infrared thermography is a fast and effective inspection method for detecting debond defects with the diameter over 10 mm and depth within 5 mm.
2011,
23: 24-25.
Abstract:
Under large-angle oblique incidence, the optical thin films exhibit strong polarization effects. The reflectance and transmittance for both S- and P-components will exhibit some polarization deviations. The reflection-and transmission-induced phase retardances will exhibit the same behavior. After the analysis of the physical essence within the polarization effects, a near-infrared nonpolarizing beam splitter with a reflectance of 50% in 1 500-1 600 nm spectral range was designed. It adopted a thin film stack with approximately equal equivalent admittances for both S- and P-components with the aid of simplex optimization algorithm. According to the results, in the working range of spectrum with the incident angle of 45, the splitter maintains a very low polarization ratio, and both the reflectance( transmittance) curve deviation and the reflection (transmission)-induced phase change are small.
Under large-angle oblique incidence, the optical thin films exhibit strong polarization effects. The reflectance and transmittance for both S- and P-components will exhibit some polarization deviations. The reflection-and transmission-induced phase retardances will exhibit the same behavior. After the analysis of the physical essence within the polarization effects, a near-infrared nonpolarizing beam splitter with a reflectance of 50% in 1 500-1 600 nm spectral range was designed. It adopted a thin film stack with approximately equal equivalent admittances for both S- and P-components with the aid of simplex optimization algorithm. According to the results, in the working range of spectrum with the incident angle of 45, the splitter maintains a very low polarization ratio, and both the reflectance( transmittance) curve deviation and the reflection (transmission)-induced phase change are small.
2011,
23: 25-26.
Abstract:
The DF and CO2 laser mediums matching for a mid- and far-infrared dual-band laser was studied. Theoretical analysis of the gain distribution of the two mediums shows that, compared with the CO2 laser medium, the peak gain position of DF laser medium is more ahead, and the gain zone length is much shorter. Then a dual-band laser was designed and manufactured, with the position of theCO2 injection orifices adjustable, and the match between the peak gain positions of DF andCO2 laser mediums can be achieved by the position difference of the D2 and CO2 injection orifices. The experiment shows that the design is effective, and the optimum position of the common optical axis of this dual-band laser is 3 mm downstream of D2
The DF and CO2 laser mediums matching for a mid- and far-infrared dual-band laser was studied. Theoretical analysis of the gain distribution of the two mediums shows that, compared with the CO2 laser medium, the peak gain position of DF laser medium is more ahead, and the gain zone length is much shorter. Then a dual-band laser was designed and manufactured, with the position of theCO2 injection orifices adjustable, and the match between the peak gain positions of DF andCO2 laser mediums can be achieved by the position difference of the D2 and CO2 injection orifices. The experiment shows that the design is effective, and the optimum position of the common optical axis of this dual-band laser is 3 mm downstream of D2
2011,
23: 26-27.
Abstract:
A computer-generated hologram about spiral phase light beam with four topological charges is realized, which is then inputted into spatial light modulators(SLMs). When a plane wave transits through the SLMs, a series of high-order optical vortices occur. In order to improve the diffraction efficiency, a spiral phase plate(SPP) with four topological charges is created by direct laser writing lithography. The theoretical depth of SPP is 1.073 m and the measured depth is 1.082 m, showing a manufacture error of no more than 0.83%.The efficiency and beam profile of Fraunhofer diffraction of the SPP are measured with a power meter and a CCD camera. The diffraction efficiency reaches 86% and the energy distribution is in a good agreement with theory.
A computer-generated hologram about spiral phase light beam with four topological charges is realized, which is then inputted into spatial light modulators(SLMs). When a plane wave transits through the SLMs, a series of high-order optical vortices occur. In order to improve the diffraction efficiency, a spiral phase plate(SPP) with four topological charges is created by direct laser writing lithography. The theoretical depth of SPP is 1.073 m and the measured depth is 1.082 m, showing a manufacture error of no more than 0.83%.The efficiency and beam profile of Fraunhofer diffraction of the SPP are measured with a power meter and a CCD camera. The diffraction efficiency reaches 86% and the energy distribution is in a good agreement with theory.
2011,
23: 27-28.
Abstract:
In order to improve measurement accuracy, a double-band pyrometric method based on emissivity compensation has been proposed for steel under laser irradiation. With exponential models as emissivity model, the measurement errors are below 4%. Meanwhile the comparison between the traditional double-band method and this method has been conducted, and the precision of this method is obviously higher. The quantitative analysis of data processed by this method shows that, the calculation errors are between 13 ℃ and 25 ℃.
In order to improve measurement accuracy, a double-band pyrometric method based on emissivity compensation has been proposed for steel under laser irradiation. With exponential models as emissivity model, the measurement errors are below 4%. Meanwhile the comparison between the traditional double-band method and this method has been conducted, and the precision of this method is obviously higher. The quantitative analysis of data processed by this method shows that, the calculation errors are between 13 ℃ and 25 ℃.
Multimodal image registration algorithm based on Shape Context and scale-invariant feature transform
2011,
23: 28-29.
Abstract:
An image registration method for multimodal images is proposed. This method is a combination of modified scale-invariant feature transform(SIFT) feature extraction algorithm and Shape Context feature descriptor. Feature points of multimodal images are extracted by modified SIFT feature extraction algorithm. Then each feature point is described by modified shape context descriptor, which forms a feature vector from the orientation histograms of sub-region around each feature point. After feature points matching with Euclidean distance as measure, the RANSAC algorithm is used to eliminate wrong corresponding pairs. At last, multimodal images registration is achieved by affine transformation and bilinear interpolation. Experimental results for registration of infrared images and vis
An image registration method for multimodal images is proposed. This method is a combination of modified scale-invariant feature transform(SIFT) feature extraction algorithm and Shape Context feature descriptor. Feature points of multimodal images are extracted by modified SIFT feature extraction algorithm. Then each feature point is described by modified shape context descriptor, which forms a feature vector from the orientation histograms of sub-region around each feature point. After feature points matching with Euclidean distance as measure, the RANSAC algorithm is used to eliminate wrong corresponding pairs. At last, multimodal images registration is achieved by affine transformation and bilinear interpolation. Experimental results for registration of infrared images and vis
2011,
23: 29-30.
Abstract:
Both electrical discharge waveforms and pictures recorded by multi-frame camera at different times are used to study the SF6 discharge characteristics in HF laser. The experimental results indicate that the discharge process can be divided into three stages as main discharge, residual voltage maintenance and arc discharge. In the main discharge stage, uniform volume discharge occurs and the energy stored in the capacitors deposits mainly in the discharge plasma. In the residual voltage maintenance stage, no evident discharge is observed. In the arc discharge stage, the residual energy is dissipated through arc. The dependency of energy deposition efficiency and residual voltage on charge voltage is obtained by analyzing the discharge waveforms. With charging voltage increasing, t
Both electrical discharge waveforms and pictures recorded by multi-frame camera at different times are used to study the SF6 discharge characteristics in HF laser. The experimental results indicate that the discharge process can be divided into three stages as main discharge, residual voltage maintenance and arc discharge. In the main discharge stage, uniform volume discharge occurs and the energy stored in the capacitors deposits mainly in the discharge plasma. In the residual voltage maintenance stage, no evident discharge is observed. In the arc discharge stage, the residual energy is dissipated through arc. The dependency of energy deposition efficiency and residual voltage on charge voltage is obtained by analyzing the discharge waveforms. With charging voltage increasing, t
2011,
23: 30-31.
Abstract:
Considering the influences of temperature on refractive index and grating period, the paper studies the relations between quasi-phase-matched second harmonic generation (SHG) conversion efficiency and temperature, and analyzes the influences of laser thermal effect on quasi-phase-matched SHG. The temperature distribution and SHG conversion efficiency under the influences of laser thermal effect inside periodically poled lithium niobate (PPLN) crystal are calculated by finite element method. The results show that, for fundamental wave of different power, the temperature distributions and the refractive index distributions on crystal sections along the direction of light are different, and so are the SHG conversion efficiency distributions on the exit facet of crystal. With the pow
Considering the influences of temperature on refractive index and grating period, the paper studies the relations between quasi-phase-matched second harmonic generation (SHG) conversion efficiency and temperature, and analyzes the influences of laser thermal effect on quasi-phase-matched SHG. The temperature distribution and SHG conversion efficiency under the influences of laser thermal effect inside periodically poled lithium niobate (PPLN) crystal are calculated by finite element method. The results show that, for fundamental wave of different power, the temperature distributions and the refractive index distributions on crystal sections along the direction of light are different, and so are the SHG conversion efficiency distributions on the exit facet of crystal. With the pow
2011,
23: 31-32.
Abstract:
The output characteristics of misaligned resonator for large-aperture thin disk laser have been studied experimentally and theoretically. A plane output coupler S1, a concave mirror S2 and an aperture stop are arranged to define the V-shape resonator. The misalignment sensitivities of the output power are given by means of matrix optics and the misalignment diffraction integral equation. The misalignment effects of the resonator having a variable aperture stop diameter on output power and beam quality have been measured by tilt -angle measurement technique at 200 Hz pump frequency, as well as the output power relationship with the misalignments of mirror S1 and mirror S2 at 300 Hz pump frequency. The experimental results show that the output power is a quadratic function of
The output characteristics of misaligned resonator for large-aperture thin disk laser have been studied experimentally and theoretically. A plane output coupler S1, a concave mirror S2 and an aperture stop are arranged to define the V-shape resonator. The misalignment sensitivities of the output power are given by means of matrix optics and the misalignment diffraction integral equation. The misalignment effects of the resonator having a variable aperture stop diameter on output power and beam quality have been measured by tilt -angle measurement technique at 200 Hz pump frequency, as well as the output power relationship with the misalignments of mirror S1 and mirror S2 at 300 Hz pump frequency. The experimental results show that the output power is a quadratic function of
2011,
23: 32-33.
Abstract:
For detecting the moving dim-small targets in infrared image sequences, the paper studies the motion characteristics, the probability distribution characteristics, and the energy distribution characteristics between targets and noises. Firstly, it uses high-order cumulant based on M continuous images to enhance the energy of moving dim targets. Then the hypothesis test is used to separate the targets and background. Finally, the multi-frame correlation detection is made through searching the moving energy center of image sequences. The simulation results show that the proposed algorithm is effective for infrared dim-small targets detection.
For detecting the moving dim-small targets in infrared image sequences, the paper studies the motion characteristics, the probability distribution characteristics, and the energy distribution characteristics between targets and noises. Firstly, it uses high-order cumulant based on M continuous images to enhance the energy of moving dim targets. Then the hypothesis test is used to separate the targets and background. Finally, the multi-frame correlation detection is made through searching the moving energy center of image sequences. The simulation results show that the proposed algorithm is effective for infrared dim-small targets detection.
2011,
23: 33-34.
Abstract:
An all-fiber master oscillator power amplifier(MOPA) structured single-frequency fiber laser is demonstrated. The seed laser is a self-designed ring cavity structure which outputs a single-frequency laser beam. The 10 MHz linewidth, 1 079.88 nm MOPA laser has a output power of 10.02 W, when pumped by a diode laser at 976 nm. The signal-to-noise is about 30 dB, the slope efficiency is 65.3% and the optical-optical conversion efficiency is 58.9%.
An all-fiber master oscillator power amplifier(MOPA) structured single-frequency fiber laser is demonstrated. The seed laser is a self-designed ring cavity structure which outputs a single-frequency laser beam. The 10 MHz linewidth, 1 079.88 nm MOPA laser has a output power of 10.02 W, when pumped by a diode laser at 976 nm. The signal-to-noise is about 30 dB, the slope efficiency is 65.3% and the optical-optical conversion efficiency is 58.9%.
2011,
23: 34-35.
Abstract:
The paper establishes a fault tree model for chemical oxygen iodine laser(COIL) considering power abnormity as its peak affair of fault, and then makes down-way qualitative analysis and quantitative analysis with the minimum cut-set theory. It is indicated that the reliability of iodine supply subsystem is minimum, followed by the chlorine supply subsystem, in the seven subsystems of COIL. The probability at which the power of COIL is abnormal is 3.99%, that is, the reliability of laser is 96.01%.
The paper establishes a fault tree model for chemical oxygen iodine laser(COIL) considering power abnormity as its peak affair of fault, and then makes down-way qualitative analysis and quantitative analysis with the minimum cut-set theory. It is indicated that the reliability of iodine supply subsystem is minimum, followed by the chlorine supply subsystem, in the seven subsystems of COIL. The probability at which the power of COIL is abnormal is 3.99%, that is, the reliability of laser is 96.01%.
2011,
23: 35-36.
Abstract:
According to the strict requirement for wavefront distortion of large aperture mirror in high power solid-state laser facility, the mirror mount structure was designed by selecting appropriate structure, materials, and location of connections and support. Then its optimization calculation, analysis and confirmatory tests were carried out. Surface accuracy test results show that the peak-valley value of additional wavefront distortion introduced by clamping is about 150 nm, less than /3 (=632 nm). The structure can meet the design requirement.
According to the strict requirement for wavefront distortion of large aperture mirror in high power solid-state laser facility, the mirror mount structure was designed by selecting appropriate structure, materials, and location of connections and support. Then its optimization calculation, analysis and confirmatory tests were carried out. Surface accuracy test results show that the peak-valley value of additional wavefront distortion introduced by clamping is about 150 nm, less than /3 (=632 nm). The structure can meet the design requirement.
2011,
23: 36-37.
Abstract:
Surface characteristics of mirrors made from polycrystalline Mo, bulk metallic glasses(BMGs) Zr65Al7.5Ni10Cu17.5 and Co61.2B26.2Si7.8Ta4.8 were studied. The mirrors were exposed to H plasma in an unbalanced magnetron sputtering chamber. The results show that with increasing the H plasma sputtering time, surface roughnesses of the mirrors made from polycrystalline Mo and BMG Zr65Al7.5Ni10Cu17.5 increase and their specular reflectivities decrease; whereas the surface roughness reduces and the reflectivity increases for the mirror made from BMG Co61.2B26.2Si7.8Ta4.8. During H plasma sputtering, the surface sta
Surface characteristics of mirrors made from polycrystalline Mo, bulk metallic glasses(BMGs) Zr65Al7.5Ni10Cu17.5 and Co61.2B26.2Si7.8Ta4.8 were studied. The mirrors were exposed to H plasma in an unbalanced magnetron sputtering chamber. The results show that with increasing the H plasma sputtering time, surface roughnesses of the mirrors made from polycrystalline Mo and BMG Zr65Al7.5Ni10Cu17.5 increase and their specular reflectivities decrease; whereas the surface roughness reduces and the reflectivity increases for the mirror made from BMG Co61.2B26.2Si7.8Ta4.8. During H plasma sputtering, the surface sta
2011,
23: 37-38.
Abstract:
Eight beams of 351 nm laser entered the gold hohlraum through the laser entrance holes at Shenguang Ⅱ laser facility, and created X-rays to drive the DD capsule centered in the hohlraum to implode. The 9th beam of laser at 526.5 nm irradiated Pd backlighter foil, and generated a large area Pd L-shell X-ray backlighter to radiograph the implosion capsule. The radiographic image of the implosion capsule was recorded using an X-ray streak camera with a 20 ps time resolution. The X-ray backlighting radiography technique for the implosion capsule was established, and the imploding capsule was observed distinctly in the experiment. Experimental results of the trajectory and the implosion velocity of the capsule were presented, which can provide important information for the optimizati
Eight beams of 351 nm laser entered the gold hohlraum through the laser entrance holes at Shenguang Ⅱ laser facility, and created X-rays to drive the DD capsule centered in the hohlraum to implode. The 9th beam of laser at 526.5 nm irradiated Pd backlighter foil, and generated a large area Pd L-shell X-ray backlighter to radiograph the implosion capsule. The radiographic image of the implosion capsule was recorded using an X-ray streak camera with a 20 ps time resolution. The X-ray backlighting radiography technique for the implosion capsule was established, and the imploding capsule was observed distinctly in the experiment. Experimental results of the trajectory and the implosion velocity of the capsule were presented, which can provide important information for the optimizati
2011,
23: 38-39.
Abstract:
In this study PLASIMO program developed by Eindhoven University of Technology was used to investigate the effects of argon flow velocity on argon plasma in the cascaded arc. The simulation results are in good agreement with available experimental data that along the symmetry axis, the pressure decreases but the electron temperature increases from the inlet to the outlet. The effects of flow velocity of argon on plasma properties were investigated. The simulation results show that for argon arc discharges, with increasing the flow velocity, the electron density and the heavy particle temperature increases, while the electron temperature decreases. Along the symmetry axis, the electron temperatures are all above 1 eV and the heavy particle temperatures are all about 1 eV at differe
In this study PLASIMO program developed by Eindhoven University of Technology was used to investigate the effects of argon flow velocity on argon plasma in the cascaded arc. The simulation results are in good agreement with available experimental data that along the symmetry axis, the pressure decreases but the electron temperature increases from the inlet to the outlet. The effects of flow velocity of argon on plasma properties were investigated. The simulation results show that for argon arc discharges, with increasing the flow velocity, the electron density and the heavy particle temperature increases, while the electron temperature decreases. Along the symmetry axis, the electron temperatures are all above 1 eV and the heavy particle temperatures are all about 1 eV at differe
2011,
23: 39-40.
Abstract:
In laser fusion experiments, fuel capsules with high sphericity and high wall-thickness uniformity are often fabricated by density matched emulsion method. The paper investigates the influences of the interfacial tension, viscosity of oil phase, size and thickness of shell in the fabrication process by T.Norimatsus model. The results indicate that bigger interfacial tension and smaller size of shell lead to better uniformity. The viscosity of oil phase may have different effects on uniformity, when the outer oil surface moves in different forms.
In laser fusion experiments, fuel capsules with high sphericity and high wall-thickness uniformity are often fabricated by density matched emulsion method. The paper investigates the influences of the interfacial tension, viscosity of oil phase, size and thickness of shell in the fabrication process by T.Norimatsus model. The results indicate that bigger interfacial tension and smaller size of shell lead to better uniformity. The viscosity of oil phase may have different effects on uniformity, when the outer oil surface moves in different forms.
2011,
23: 40-41.
Abstract:
With copper powders as dopant, Copper-doped poly-4-methyl-1-pentene(PMP) foams were prepared by thermal-induced phase inversion. Their skeleton, composition and element small area distribution were characterized by high resolution electron microscopy. The results show that the distribution of copper powders in the doped PMP foams is condensed, not uniform. Compared with PMP foams without doping, the size of pores and skeleton of the doped PMP foams is bigger. Copper particles in the doped foams are firmly enwrapped by carbon network, and there is oxygen besides copper and carbon, which is not anticipated during the foams synthesis.
With copper powders as dopant, Copper-doped poly-4-methyl-1-pentene(PMP) foams were prepared by thermal-induced phase inversion. Their skeleton, composition and element small area distribution were characterized by high resolution electron microscopy. The results show that the distribution of copper powders in the doped PMP foams is condensed, not uniform. Compared with PMP foams without doping, the size of pores and skeleton of the doped PMP foams is bigger. Copper particles in the doped foams are firmly enwrapped by carbon network, and there is oxygen besides copper and carbon, which is not anticipated during the foams synthesis.
2011,
23: 41-42.
Abstract:
The paper uses the single-factor method for the study of spherical titanium powder preparation process. Titanium powders with excellent sphericity can be prepared through controlling and regulating the radio frequency plasma anode working current and voltage, central gas flow rate, sheath gas flow rate, powder-carrying gas flow rate, negative ventilation pressure and powder feed rate, etc. Spheroidization of titanium powders with a size of (17.02.0) m is performed by radio frequency plasma technology. With the increase of negative ventilation pressure, the spheroidization rate of titanium powders increases firstly and then decreases rapidly at the turning point around 1 800 Pa. With the rate of powder feed increasing, the spheroidization rate of titanium powders incre
The paper uses the single-factor method for the study of spherical titanium powder preparation process. Titanium powders with excellent sphericity can be prepared through controlling and regulating the radio frequency plasma anode working current and voltage, central gas flow rate, sheath gas flow rate, powder-carrying gas flow rate, negative ventilation pressure and powder feed rate, etc. Spheroidization of titanium powders with a size of (17.02.0) m is performed by radio frequency plasma technology. With the increase of negative ventilation pressure, the spheroidization rate of titanium powders increases firstly and then decreases rapidly at the turning point around 1 800 Pa. With the rate of powder feed increasing, the spheroidization rate of titanium powders incre
2011,
23: 42-43.
Abstract:
This paper studies the ultra-wideband(UWB) irradiation effects on communication equipment. Studies have shown that, the malfunction of communication equipment appears when the communication equipment is put in an irradiation field with E-field intensity larger than 50 kV/m, UWB pulse rising edge under 1 ns and duration under 2 ns. The coupling channel here is the display panel of communication equipment. The effects of display panel malfunction, machine halt and restart, and sound stoppage appear when the communication equipment is put in an irradiation field with E-field intensity larger than 150 kV/m. No cumulative effect shows up for the irradiation effects are only related to the E-field intensity, and the coupling channels are the display panel of communication equipme
This paper studies the ultra-wideband(UWB) irradiation effects on communication equipment. Studies have shown that, the malfunction of communication equipment appears when the communication equipment is put in an irradiation field with E-field intensity larger than 50 kV/m, UWB pulse rising edge under 1 ns and duration under 2 ns. The coupling channel here is the display panel of communication equipment. The effects of display panel malfunction, machine halt and restart, and sound stoppage appear when the communication equipment is put in an irradiation field with E-field intensity larger than 150 kV/m. No cumulative effect shows up for the irradiation effects are only related to the E-field intensity, and the coupling channels are the display panel of communication equipme
2011,
23: 43-44.
Abstract:
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2011,
23: 44-45.
Abstract:
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2011,
23: 45-46.
Abstract:
A beam energy spread monitor(BESM) with eight stripline electrodes in four-axis symmetry is designed for high-brightness injector in Hefei Light Source, to achieve the non-intercept measurement of beam energy spread. The formula to get the beam transverse size from BESMs electrode signals is figured out. With the sensitivity of the BESM, impedance matching, the time domain and frequence domain response of the stripline electrodes, etc., being considered, the physical structure of this eight-stripline BESM, such as the electrodes open-angle, radius, length, is got. The eight-stripline BESM is calibrated with a calibration system by antenna method, and the offset between the electrical center and the mechanical center, the position sensitivity and the quadrupole compo
A beam energy spread monitor(BESM) with eight stripline electrodes in four-axis symmetry is designed for high-brightness injector in Hefei Light Source, to achieve the non-intercept measurement of beam energy spread. The formula to get the beam transverse size from BESMs electrode signals is figured out. With the sensitivity of the BESM, impedance matching, the time domain and frequence domain response of the stripline electrodes, etc., being considered, the physical structure of this eight-stripline BESM, such as the electrodes open-angle, radius, length, is got. The eight-stripline BESM is calibrated with a calibration system by antenna method, and the offset between the electrical center and the mechanical center, the position sensitivity and the quadrupole compo
2011,
23: 46-47.
Abstract:
The paper introduces the RF system overall solutions and design process for the petal- shaped irradiation accelerator NB100, such as the magnetic coupling design of the input components, the mode connected by coaxial transmission line between RF power source and accelerating cavity, the choice of flat window as the isolation window. Final design data and graphics for coupling loop are also included. With the RF system being put into use, the initial test shows that, the continuous input power is 100 kW and the pulse power is 250 kW when the standing wave ratio is less than 1.1. The rationality of the RF system design scheme is confirmed.
The paper introduces the RF system overall solutions and design process for the petal- shaped irradiation accelerator NB100, such as the magnetic coupling design of the input components, the mode connected by coaxial transmission line between RF power source and accelerating cavity, the choice of flat window as the isolation window. Final design data and graphics for coupling loop are also included. With the RF system being put into use, the initial test shows that, the continuous input power is 100 kW and the pulse power is 250 kW when the standing wave ratio is less than 1.1. The rationality of the RF system design scheme is confirmed.
2011,
23: 47-48.
Abstract:
Emittance growth induced by space charge effect is very important, especially for CW DC-gun photoinjector. In this work, the linear space charge force and its effect on electron beam transverse emittance are studied, and the principle and properties of emittance compensation by solenoid are analyzed. The CAEP DC-gun photoinjector with a solenoid is also simulated by code Parmela. Simulated results indicate that the normalized transverse emittance of an 80 pC bunch at the 350 keV DC-gun exit is 5.14 mmmrad. And after compensated by a solenoid, it becomes 1.27 mmmrad. The emittance of beam is well compensated.
Emittance growth induced by space charge effect is very important, especially for CW DC-gun photoinjector. In this work, the linear space charge force and its effect on electron beam transverse emittance are studied, and the principle and properties of emittance compensation by solenoid are analyzed. The CAEP DC-gun photoinjector with a solenoid is also simulated by code Parmela. Simulated results indicate that the normalized transverse emittance of an 80 pC bunch at the 350 keV DC-gun exit is 5.14 mmmrad. And after compensated by a solenoid, it becomes 1.27 mmmrad. The emittance of beam is well compensated.
2011,
23: 48-49.
Abstract:
An approach for the measurement of the number of high-energy pulsed fission neutrons is investigated. The radiation absorber in the beam and the thickness of CH2 proton radiator are optimized. The background from scattering neutrons and gamma rays is measured in situ using the back-to-back structure designed and then subtracted directly. The signal-to-background ratio of the detection system for measuring high-energy fission neutrons is up to 10.
An approach for the measurement of the number of high-energy pulsed fission neutrons is investigated. The radiation absorber in the beam and the thickness of CH2 proton radiator are optimized. The background from scattering neutrons and gamma rays is measured in situ using the back-to-back structure designed and then subtracted directly. The signal-to-background ratio of the detection system for measuring high-energy fission neutrons is up to 10.
2011,
23: 49-50.
Abstract:
A pulsed radio frequency hollow cathode plasma source was used to excite working gas containing methyl bromide and the plasma emission spectra were measured by HR4000 high-resolution spectrometer. Two characteristic peaks of bromine atom respectively at 635.07 nm and 700.52 nm were observed. The influence of gas pressure and concentration of methyl bromide on the intensity of the two characteristic peaks was investigated. The results show that the intensity the two characteristic peaks decreases with the increasing of gas pressure at the same concentration of methyl bromide, and increases with the increasing of the concentration under the same gas pressure. The accuracy of methyl bromide concentration measurement can be better than 1 g/m3.
A pulsed radio frequency hollow cathode plasma source was used to excite working gas containing methyl bromide and the plasma emission spectra were measured by HR4000 high-resolution spectrometer. Two characteristic peaks of bromine atom respectively at 635.07 nm and 700.52 nm were observed. The influence of gas pressure and concentration of methyl bromide on the intensity of the two characteristic peaks was investigated. The results show that the intensity the two characteristic peaks decreases with the increasing of gas pressure at the same concentration of methyl bromide, and increases with the increasing of the concentration under the same gas pressure. The accuracy of methyl bromide concentration measurement can be better than 1 g/m3.
2011,
23: 50-51.
Abstract:
A systematic design method has been proposed for studying the dynamic design of rotating mirror for ultra-high speed camera. With the finite element software, the numerical analyses of static, modal, harmonic responses and natural frequency sensitivity for the preliminary-designed rotating mirror were done based on the static and dynamic theories. Some experiments were done to verify the results. The physical dimensions of the rotating mirror were modified repeatedly according to the results for designing a new rotating mirror. Then simulation and experiments of fatigue life for the new rotating mirror under alternating force were done. The results show that the maximum static stress is less than the yield stress of the rotating mirror material, which proves the new rotating mirr
A systematic design method has been proposed for studying the dynamic design of rotating mirror for ultra-high speed camera. With the finite element software, the numerical analyses of static, modal, harmonic responses and natural frequency sensitivity for the preliminary-designed rotating mirror were done based on the static and dynamic theories. Some experiments were done to verify the results. The physical dimensions of the rotating mirror were modified repeatedly according to the results for designing a new rotating mirror. Then simulation and experiments of fatigue life for the new rotating mirror under alternating force were done. The results show that the maximum static stress is less than the yield stress of the rotating mirror material, which proves the new rotating mirr
2011,
23: 51-52.
Abstract:
The paper proposes and numerically demonstrates a simple and efficient broadband frequency-tripling scheme for Nd:glass laser system based on mixing narrowband and broadband laser pulses in the sum-frequency generation (SFG) process. The group-velocity mismatching effect in the of SFG process is substantially alleviated with the assist of a narrowband laser, which is the dominant obstacle to efficient broadband third-harmonic generation. Moreover, by adding a second tripler in the SFG process, the proposed scheme will support efficient frequency tripling over a bandwidth of 5 nm (theoretical efficiency more than 80%).
The paper proposes and numerically demonstrates a simple and efficient broadband frequency-tripling scheme for Nd:glass laser system based on mixing narrowband and broadband laser pulses in the sum-frequency generation (SFG) process. The group-velocity mismatching effect in the of SFG process is substantially alleviated with the assist of a narrowband laser, which is the dominant obstacle to efficient broadband third-harmonic generation. Moreover, by adding a second tripler in the SFG process, the proposed scheme will support efficient frequency tripling over a bandwidth of 5 nm (theoretical efficiency more than 80%).
2011,
23: 52-53.
Abstract:
A flexible induced charge model of CdZnTe pixellated detector is presented. This model takes into account the charge trapping effect in the detection process. The distribution of the trapped carriers in CdZnTe crystal is derived based on the continuity equations. In consequence, an evaluation model based on the presampling modulation transfer function (presampling MTF) is obtained. As shown through the numerical simulation, the detector imaging quality decreases obviously with the increase in incident photon energy. When the electron- and hole-mobility lifetime products are 0.510-3 to 5.010-3 cm2/V and 2.010-5 to 7.510-5 cm2/V, respectively, the model signal is almost due to the electron
A flexible induced charge model of CdZnTe pixellated detector is presented. This model takes into account the charge trapping effect in the detection process. The distribution of the trapped carriers in CdZnTe crystal is derived based on the continuity equations. In consequence, an evaluation model based on the presampling modulation transfer function (presampling MTF) is obtained. As shown through the numerical simulation, the detector imaging quality decreases obviously with the increase in incident photon energy. When the electron- and hole-mobility lifetime products are 0.510-3 to 5.010-3 cm2/V and 2.010-5 to 7.510-5 cm2/V, respectively, the model signal is almost due to the electron
2011,
23: 53-54.
Abstract:
In order to investigate the characteristics of light flash intensity produced by hypervelocity impact, experiments on hypervelocity impact of 2024-T4 aluminum target were conducted under two kinds of experimental conditions by using an optical pyrometer measurement system established and a two-stage light-gas gun loading system. Two sets of optical fiber probes were used in every experiment: one directed to the impact point, and the other laterally directed to the impact point. Under the given experimental conditions and optical fiber probe schemes, the analysis of acquired original data show that the peak value impact light flash intensity increases with the wavelength increasing in the range from 405 to 633 nm during the hypervelocity impact of 2024-T4 aluminum target, and it d
In order to investigate the characteristics of light flash intensity produced by hypervelocity impact, experiments on hypervelocity impact of 2024-T4 aluminum target were conducted under two kinds of experimental conditions by using an optical pyrometer measurement system established and a two-stage light-gas gun loading system. Two sets of optical fiber probes were used in every experiment: one directed to the impact point, and the other laterally directed to the impact point. Under the given experimental conditions and optical fiber probe schemes, the analysis of acquired original data show that the peak value impact light flash intensity increases with the wavelength increasing in the range from 405 to 633 nm during the hypervelocity impact of 2024-T4 aluminum target, and it d
2011,
23: 54-55.
Abstract:
The paper proposes a performance improving scheme for the conventional time-correlated single photon counting spectrometer and develops a high speed data acquisition card based on PCI bus and FPGA technologies. The card is used to replace the multi-channel analyzer to improve the capability and decrease the volume of the spectrometer. The process of operation is introduced along with the integration of the spectrometer system. Many standard samples are measured. The experimental results show that the sensitivity of the spectrometer is single photon counting, and the time resolution of fluorescence lifetime measurement can be picosecond level. The instrument could measure the time-resolved spectroscopy.
The paper proposes a performance improving scheme for the conventional time-correlated single photon counting spectrometer and develops a high speed data acquisition card based on PCI bus and FPGA technologies. The card is used to replace the multi-channel analyzer to improve the capability and decrease the volume of the spectrometer. The process of operation is introduced along with the integration of the spectrometer system. Many standard samples are measured. The experimental results show that the sensitivity of the spectrometer is single photon counting, and the time resolution of fluorescence lifetime measurement can be picosecond level. The instrument could measure the time-resolved spectroscopy.
2011,
23: 55-56.
Abstract:
Steady-state and transient thermal analysis of electron gun for a Ka-band traveling wave tube are theoretically performed with a newly-developed 2 mm cathode model by ANSYS software. The heat flux vector chart and temperature distribution chart as well as warm-up time are also derived. The discrepancy of 2% between simulation results and test results, proves that the finite element method is feasible. The ultimate temperature reached by cathode, at given heater power, remarkably depends on the thermal conduction mechanism through cathode module. Based on the heat flux vector chart, the structure of cathode support sleeve with the highest heat flux is optimized. After optimization, the temperature of cathode increases 28 ℃, the highest temperature of electron gun increases 27 ℃
Steady-state and transient thermal analysis of electron gun for a Ka-band traveling wave tube are theoretically performed with a newly-developed 2 mm cathode model by ANSYS software. The heat flux vector chart and temperature distribution chart as well as warm-up time are also derived. The discrepancy of 2% between simulation results and test results, proves that the finite element method is feasible. The ultimate temperature reached by cathode, at given heater power, remarkably depends on the thermal conduction mechanism through cathode module. Based on the heat flux vector chart, the structure of cathode support sleeve with the highest heat flux is optimized. After optimization, the temperature of cathode increases 28 ℃, the highest temperature of electron gun increases 27 ℃
2011,
23: 56-57.
Abstract:
This paper summarizes the design and test results of twelve-brick fast linear transformer driver(FLTD) stage. The configuration and critical components of the stage are introduced. The self-breakdown voltage and triggering feature testing of all the switches is operated. When the charge voltage of the stage is 150 kV, the short-circuit output current is 235 kA, and the current rise time is 88.2 ns(10% to 90%). For a 0.58 load, the output current is 114.5 kA, and the current rise time is 88.9 ns(10% to 90%). Discharge synchronization of all the twelve switches with charge voltage of 120 kV is studied with differential loop. The experimental results indicate that the probability curve for discharge synchronization is consistent with the Gaussian curve approximately for 100
This paper summarizes the design and test results of twelve-brick fast linear transformer driver(FLTD) stage. The configuration and critical components of the stage are introduced. The self-breakdown voltage and triggering feature testing of all the switches is operated. When the charge voltage of the stage is 150 kV, the short-circuit output current is 235 kA, and the current rise time is 88.2 ns(10% to 90%). For a 0.58 load, the output current is 114.5 kA, and the current rise time is 88.9 ns(10% to 90%). Discharge synchronization of all the twelve switches with charge voltage of 120 kV is studied with differential loop. The experimental results indicate that the probability curve for discharge synchronization is consistent with the Gaussian curve approximately for 100
2011,
23: 57-58.
Abstract:
A method of Hammerstein model direct identification under step-like signal excitation is proposed to build a nonlinear model of the pulse voltage measurement system in continuous domain. With the dynamic calibration data in time-domain, the systems Hammerstein model with a four-order polynomial nonlinear element and a three-order linear element in continuous domain is established. The measured results verify the validity of the model. Then a compensation element to improve the sensors dynamic performance is designed, which includes a dynamic linear compensator and a static nonlinear corrector. After compensation, the lower cut-off frequency of the system widens from dozens of kHz to DC, and the response time of the system shortens form s level to ns level. The feasibility of the compensation design is also verified by the reconstruction result of measured pulse.
A method of Hammerstein model direct identification under step-like signal excitation is proposed to build a nonlinear model of the pulse voltage measurement system in continuous domain. With the dynamic calibration data in time-domain, the systems Hammerstein model with a four-order polynomial nonlinear element and a three-order linear element in continuous domain is established. The measured results verify the validity of the model. Then a compensation element to improve the sensors dynamic performance is designed, which includes a dynamic linear compensator and a static nonlinear corrector. After compensation, the lower cut-off frequency of the system widens from dozens of kHz to DC, and the response time of the system shortens form s level to ns level. The feasibility of the compensation design is also verified by the reconstruction result of measured pulse.
2011,
23: 58-59.
Abstract:
The paper introduces the original waveform measurement principles for pulsed E-field and the composition of a self-developed E-field sensor, and analyzes the effects of the E-field whose direction of polarization is perpendicular to the direction of monopole on the result of measurement in complicated E-field environments. A simple model of the E-field sensor to analyze the effects of monopoles and shielding boxes different of dimensions.The results of calculation accord with the theoretical analysis. The effect of the E-field whose direction of polarization is perpendicular to the direction of monopole can be ignored, for the response to the interference has an intensity two or more orders of magnitude lower than that to the field to be measured, whose intensity is the sam
The paper introduces the original waveform measurement principles for pulsed E-field and the composition of a self-developed E-field sensor, and analyzes the effects of the E-field whose direction of polarization is perpendicular to the direction of monopole on the result of measurement in complicated E-field environments. A simple model of the E-field sensor to analyze the effects of monopoles and shielding boxes different of dimensions.The results of calculation accord with the theoretical analysis. The effect of the E-field whose direction of polarization is perpendicular to the direction of monopole can be ignored, for the response to the interference has an intensity two or more orders of magnitude lower than that to the field to be measured, whose intensity is the sam
