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RSS2010 Vol. 22, No. 01
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2010,
22.
Abstract:
To calculate nonlinear transport of pulsed beams in the six-dimensional phase space of solenoid lens accurately, a beam dynamics program has been designed using Visual Fortran 6.5 to calculate the beam optical system consisting of drift spaces and solenoid lenses. For non-intense beams, particle trajectory can be obtained by multiplying linear transport matrices. For nonlinear transport of intense beams, the influence of space-charge effect on beam transport needs to be taken into account, and self-consistent solution should be derived because of the interaction between charged particle distribution and space charge field. In the program, components and currents are divided into equal intervals, respectively, and each interval is treated as a uniform solenoid field. Then beam current itera
To calculate nonlinear transport of pulsed beams in the six-dimensional phase space of solenoid lens accurately, a beam dynamics program has been designed using Visual Fortran 6.5 to calculate the beam optical system consisting of drift spaces and solenoid lenses. For non-intense beams, particle trajectory can be obtained by multiplying linear transport matrices. For nonlinear transport of intense beams, the influence of space-charge effect on beam transport needs to be taken into account, and self-consistent solution should be derived because of the interaction between charged particle distribution and space charge field. In the program, components and currents are divided into equal intervals, respectively, and each interval is treated as a uniform solenoid field. Then beam current itera
2010,
22.
Abstract:
Lanthanum hexaboride (LaB6) is a low work function material. When coated on conventional field emission tips, it can significantly enlarge the field emission current of the tips. To determine its work function, LaB6 films were deposited through e-beam deposition. It is found that the films with low oxygen content were (100) preferentially oriented. The work function was measured by thermal emission and field emission independently, yielding a value of 2.67 eV and 2.91 eV, respectively, suggesting that e-beam deposited LaB6 films preserve the low work function of bulk LaB6.
Lanthanum hexaboride (LaB6) is a low work function material. When coated on conventional field emission tips, it can significantly enlarge the field emission current of the tips. To determine its work function, LaB6 films were deposited through e-beam deposition. It is found that the films with low oxygen content were (100) preferentially oriented. The work function was measured by thermal emission and field emission independently, yielding a value of 2.67 eV and 2.91 eV, respectively, suggesting that e-beam deposited LaB6 films preserve the low work function of bulk LaB6.
2010,
22.
Abstract:
Basic properties of nuclear isomers are introduced with several possible isomer-triggering mechanisms, such as direct photon excitation, nuclear excitation by electronic transition, and nuclear excitation by electron capture. The study of triggering isomer decay is currently a very hot topic worldwide, especially via nuclear excitation by electron capture. Possibilities for carrying out this research in China are discussed.
Basic properties of nuclear isomers are introduced with several possible isomer-triggering mechanisms, such as direct photon excitation, nuclear excitation by electronic transition, and nuclear excitation by electron capture. The study of triggering isomer decay is currently a very hot topic worldwide, especially via nuclear excitation by electron capture. Possibilities for carrying out this research in China are discussed.
2010,
22.
Abstract:
For it is difficult to deal with automatic segmentation of noisy weak edge radiography image with traditional Chan-Vese(C-V) algorithm, a new image segmentation algorithm for radiography based on the level set model has been explored. This algorithm uses the segmentation of C-V algorithm as the initial contours, and then constructs a speed function with both local information of active contour and global information of C-V method. It is proved that this model is robust to initial contours’ positions and can segment noisy weak edge radiography image automatically. Besides, the testing for segmentation of the image with slender topological structure and tiny inner hole shows its significant effect.
For it is difficult to deal with automatic segmentation of noisy weak edge radiography image with traditional Chan-Vese(C-V) algorithm, a new image segmentation algorithm for radiography based on the level set model has been explored. This algorithm uses the segmentation of C-V algorithm as the initial contours, and then constructs a speed function with both local information of active contour and global information of C-V method. It is proved that this model is robust to initial contours’ positions and can segment noisy weak edge radiography image automatically. Besides, the testing for segmentation of the image with slender topological structure and tiny inner hole shows its significant effect.
2010,
22.
Abstract:
The mechanism is studied by Monte Carlo method while 1.8 MeV and 4.3 MeV alpha particles irradiating the pn junction 6H-SiC diode. In the first the process and parameters of the diode detector are introduced, and then a simulation model is established according to the structure of the detector. The research results reflect the whole transport process of alpha particles in the detector directly. The main effect of alpha particles is ionization, which produces electron-hole pairs with certain distribution. The energy loss distribution of ionization and the charge collection efficiency equation of the diode detector are provided in the end.
The mechanism is studied by Monte Carlo method while 1.8 MeV and 4.3 MeV alpha particles irradiating the pn junction 6H-SiC diode. In the first the process and parameters of the diode detector are introduced, and then a simulation model is established according to the structure of the detector. The research results reflect the whole transport process of alpha particles in the detector directly. The main effect of alpha particles is ionization, which produces electron-hole pairs with certain distribution. The energy loss distribution of ionization and the charge collection efficiency equation of the diode detector are provided in the end.
2010,
22.
Abstract:
Dose distribution in reactor for flue gas desulfurization and denitrification by 0.8 MeV electron beam irradiation has been simulated using EGSnrcMP Monte-Carlo program. The simulated results are carefully analyzed by utilizing MATLAB. To validate the reliability of the results, simulations with 0.5 MeV electron beam have been conducted, and the results are compared with experiment data from literatures, which shows a good agreement.
Dose distribution in reactor for flue gas desulfurization and denitrification by 0.8 MeV electron beam irradiation has been simulated using EGSnrcMP Monte-Carlo program. The simulated results are carefully analyzed by utilizing MATLAB. To validate the reliability of the results, simulations with 0.5 MeV electron beam have been conducted, and the results are compared with experiment data from literatures, which shows a good agreement.
2010,
22.
Abstract:
Influences of various micro/nano processing induced surface defects of KDP crystals on laser damage threshold are analyzed by finite element method, which include residual internal stress, micro-crack and micro-pore. It is found that the defects in machined KDP crystal surfaces may affect the distribution of temperature field and thermal stress field of the machined crystal surfaces, which makes the injected laser beams centralize on a small area around the defects, thus leading to partial melting of KDP crystal and laser damage threshold reduction. The laser damage threshold test experiment of the micro-crack is done, and the experiment result shows that the micro-crack will reduce the laser damage threshold of KDP crystal (reducing about 3 J/cm2) and the result fits the simulation result
Influences of various micro/nano processing induced surface defects of KDP crystals on laser damage threshold are analyzed by finite element method, which include residual internal stress, micro-crack and micro-pore. It is found that the defects in machined KDP crystal surfaces may affect the distribution of temperature field and thermal stress field of the machined crystal surfaces, which makes the injected laser beams centralize on a small area around the defects, thus leading to partial melting of KDP crystal and laser damage threshold reduction. The laser damage threshold test experiment of the micro-crack is done, and the experiment result shows that the micro-crack will reduce the laser damage threshold of KDP crystal (reducing about 3 J/cm2) and the result fits the simulation result
2010,
22.
Abstract:
Method of chaos control by coupling-feedback phase-shift and its physical model are presented for dual-ring single-mode erbium-doped fiber lasers. The coupler feeds the output back with phase-shift controller controlling the phase of feedback, and selecting apt feedback coefficient, laser chaos can be controlled into stable state or periodic state in real-time, dynamically and effectively. The evolution of system’s output state is analyzed when the control coefficient is changed, and the output of the system can produce rich laser dynamics phenomena with certain regularity. Relationship between vibration period of the system and control variables is discussed when chaos is controlled into single periodic state.
Method of chaos control by coupling-feedback phase-shift and its physical model are presented for dual-ring single-mode erbium-doped fiber lasers. The coupler feeds the output back with phase-shift controller controlling the phase of feedback, and selecting apt feedback coefficient, laser chaos can be controlled into stable state or periodic state in real-time, dynamically and effectively. The evolution of system’s output state is analyzed when the control coefficient is changed, and the output of the system can produce rich laser dynamics phenomena with certain regularity. Relationship between vibration period of the system and control variables is discussed when chaos is controlled into single periodic state.
2010,
22.
Abstract:
High density LaB6 polycrystalline bulks were fabricated by spark plasma sintering(SPS) LaB6 powders prepared by boron carbide reduction method. The effects of sintering temperature and pressure on the phase formation, microstructure and properties of the sintered LaB6 bulks were studied systematically. The optimal technological parameters are sintering temperature of 1 650 ℃, sintering pressure of 50 MPa and holding time of 10 mins. It is shown that, the mechanical and emissive properties of the sintered LaB6 bulks are much better than that prepared by other methods. The relative density of the LaB6 sintered by SPS is up to 96.2%, and its vickers hardness reaches 1 720 kg/mm2. The highest bend strength is 203.2 MPa. The electron emitting density of the polycrystalline LaB6 sintered by SPS
High density LaB6 polycrystalline bulks were fabricated by spark plasma sintering(SPS) LaB6 powders prepared by boron carbide reduction method. The effects of sintering temperature and pressure on the phase formation, microstructure and properties of the sintered LaB6 bulks were studied systematically. The optimal technological parameters are sintering temperature of 1 650 ℃, sintering pressure of 50 MPa and holding time of 10 mins. It is shown that, the mechanical and emissive properties of the sintered LaB6 bulks are much better than that prepared by other methods. The relative density of the LaB6 sintered by SPS is up to 96.2%, and its vickers hardness reaches 1 720 kg/mm2. The highest bend strength is 203.2 MPa. The electron emitting density of the polycrystalline LaB6 sintered by SPS
2010,
22.
Abstract:
A type of glow discharge triggered pseudospark switch is designed, and experimental investigation of the switch filled with He is presented. The relationship between hold-off voltage and gas pressure is measured, which shows that as gas pressure increases, hold-off voltage declines. The hold-off voltage of the pseudospark switch with 3 mm borehole diameter and 4 mm electrode distance is about 85% of that of the switch with the borehole diameter and electrode distance of 3 mm. When the borehole diameter and electrode distance are 3 mm, the influences of parameters on the time delay and jitter of the pseudospark switch is researched, such as glow discharge current, gas pressure and trigger voltage. When glow discharge current is more than 0.45 mA, gas pressure ranges in 7~30 Pa and trigger v
A type of glow discharge triggered pseudospark switch is designed, and experimental investigation of the switch filled with He is presented. The relationship between hold-off voltage and gas pressure is measured, which shows that as gas pressure increases, hold-off voltage declines. The hold-off voltage of the pseudospark switch with 3 mm borehole diameter and 4 mm electrode distance is about 85% of that of the switch with the borehole diameter and electrode distance of 3 mm. When the borehole diameter and electrode distance are 3 mm, the influences of parameters on the time delay and jitter of the pseudospark switch is researched, such as glow discharge current, gas pressure and trigger voltage. When glow discharge current is more than 0.45 mA, gas pressure ranges in 7~30 Pa and trigger v
2010,
22.
Abstract:
In order to analyze the discharge performance and improve the design of the power system, a set of measurement and diagnosis system for the 1.2 MV repetitive pulsed power source, which supplies the drive power for a high power microwave source, has been designed by studying the high-voltage, high-current testing technology, data acquisition, signal processing, fault diagnosis, virtual instruments and electromagnetic compatibility technology, etc. A resistive-capacitive divider and a Rogowski coil are adopted in measurement; ADLINK corporation’s PXI chips are used in data acquisition; data transmission system, condition monitoring and data analysis are developed by LabVIEW. This system can realize on-line monitoring and data analysis for the repetitive pulsed power source.
In order to analyze the discharge performance and improve the design of the power system, a set of measurement and diagnosis system for the 1.2 MV repetitive pulsed power source, which supplies the drive power for a high power microwave source, has been designed by studying the high-voltage, high-current testing technology, data acquisition, signal processing, fault diagnosis, virtual instruments and electromagnetic compatibility technology, etc. A resistive-capacitive divider and a Rogowski coil are adopted in measurement; ADLINK corporation’s PXI chips are used in data acquisition; data transmission system, condition monitoring and data analysis are developed by LabVIEW. This system can realize on-line monitoring and data analysis for the repetitive pulsed power source.
2010,
22.
Abstract:
Output charactrisitics of air-cored pulse transformer composed of tapered spiral winding are theoretically analysed. Parameters in the equivalent circuit are calculated to optimize output voltages. A compact spiral air-cored pulse transformer with high transformation ratio is built, which can be used on ultra-wideband system.The transformer can be charged by commercial power instead of high voltage source. The experimental result indicates that the output voltage on PFL reaches 350 kV when input voltage of charging capacitor is 800 V, with a tranformation ratio of 1∶700 and a coupling coefficient of 0.52. The result agrees with that of calculation．
Output charactrisitics of air-cored pulse transformer composed of tapered spiral winding are theoretically analysed. Parameters in the equivalent circuit are calculated to optimize output voltages. A compact spiral air-cored pulse transformer with high transformation ratio is built, which can be used on ultra-wideband system.The transformer can be charged by commercial power instead of high voltage source. The experimental result indicates that the output voltage on PFL reaches 350 kV when input voltage of charging capacitor is 800 V, with a tranformation ratio of 1∶700 and a coupling coefficient of 0.52. The result agrees with that of calculation．
2010,
22.
Abstract:
A pulsed power system is now under development. The water dielectric pulse forming line(PFL) was adopted as the wave forming part and charged by a storage capacitor via pulse transformer. The influence of leakage resistance on charging efficiency of the water dielectric PFL was analyzed. Leakage resistance of the PFL was calculated to be between 8.2 kΩ and 3 kΩ. Energy efficiency and voltage efficiency during the charging process were estimated for different module numbers, and the result shows that the energy loss rate is about 5%～12% and increases when the module number grows.
A pulsed power system is now under development. The water dielectric pulse forming line(PFL) was adopted as the wave forming part and charged by a storage capacitor via pulse transformer. The influence of leakage resistance on charging efficiency of the water dielectric PFL was analyzed. Leakage resistance of the PFL was calculated to be between 8.2 kΩ and 3 kΩ. Energy efficiency and voltage efficiency during the charging process were estimated for different module numbers, and the result shows that the energy loss rate is about 5%～12% and increases when the module number grows.
2010,
22.
Abstract:
A 65 T pulsed magnet has been manufactured and tested. The magnet coil consists of 14 layers of pure copper. Each layer of copper wire is reinforced with a layer of Zylon fiber composite. The thickness of the Zylon layer in the inner section is optimized so that the stress is even. In order to balance energy distribution and avoid overheating, two different cross-section copper wires are used in the inner and outer sections, respectively. The coil is 120 mm long with a bore of 12 mm diameter. Its power is supplied via a 1 MJ/32 mF/25 kV high density capacitor bank. At 20.6 kV voltage, 65 T field with a pulse duration of 20 ms was obtained.
A 65 T pulsed magnet has been manufactured and tested. The magnet coil consists of 14 layers of pure copper. Each layer of copper wire is reinforced with a layer of Zylon fiber composite. The thickness of the Zylon layer in the inner section is optimized so that the stress is even. In order to balance energy distribution and avoid overheating, two different cross-section copper wires are used in the inner and outer sections, respectively. The coil is 120 mm long with a bore of 12 mm diameter. Its power is supplied via a 1 MJ/32 mF/25 kV high density capacitor bank. At 20.6 kV voltage, 65 T field with a pulse duration of 20 ms was obtained.
2010,
22.
Abstract:
Magnetic core, an important part of linear transformer driver(LTD), can transfer energy from the primary side to the secondary and add induction voltage on it. So energy transfer efficiency of the core can affect efficiency, volume and weight of LTD system obviously. Factors impacting the energy transfer efficiency are primarily analyzed, and magnetic curve and energy loss are simulated by the non-linear magnetic core model of PSpice. Relative experiments are conducted, which demonstrates that the energy transfer efficiency is above 60% on 2.8 Ω load when the core working under the pulse of 20 kV, 220 ns.
Magnetic core, an important part of linear transformer driver(LTD), can transfer energy from the primary side to the secondary and add induction voltage on it. So energy transfer efficiency of the core can affect efficiency, volume and weight of LTD system obviously. Factors impacting the energy transfer efficiency are primarily analyzed, and magnetic curve and energy loss are simulated by the non-linear magnetic core model of PSpice. Relative experiments are conducted, which demonstrates that the energy transfer efficiency is above 60% on 2.8 Ω load when the core working under the pulse of 20 kV, 220 ns.
2010,
22.
Abstract:
The traditional homomorphic filtering frequently used in cloud-removing has effect on the clouds in low-frequency region, but is not effective for those in high-frequency region, because of the limitation of high-pass filters it used. Based on the study of the traditional homomorphic algorithm, the most effective high-pass filter in frequency domain is adopted. And then, in order to remove the cloud in high-frequency region, a popular nonlinear spatial filter, 3×3 median filter, is introduced, which replaces the value of the central pixel by the median of the gray levels in the 3×3 neighborhood of that pixel. At last, analysis of the experiment results in vision and statistics is carried out, which shows that the improved method is effective in removing the cloud in high-frequency region
The traditional homomorphic filtering frequently used in cloud-removing has effect on the clouds in low-frequency region, but is not effective for those in high-frequency region, because of the limitation of high-pass filters it used. Based on the study of the traditional homomorphic algorithm, the most effective high-pass filter in frequency domain is adopted. And then, in order to remove the cloud in high-frequency region, a popular nonlinear spatial filter, 3×3 median filter, is introduced, which replaces the value of the central pixel by the median of the gray levels in the 3×3 neighborhood of that pixel. At last, analysis of the experiment results in vision and statistics is carried out, which shows that the improved method is effective in removing the cloud in high-frequency region
2010,
22.
Abstract:
Nonuniform laser medium will cause the variations of phase and intensity distributions of laser modes. It is difficult to solve the wave equations associated with nonuniform laser medium. In this paper, the potential function of nonuniform laser medium was approximately expressed by the primary three items of its Taylor series expansion, and then coupled into the special function in Helmholtz equations describing the laser modes in a resonator. According to the boundary conditions of a typical resonator, we derived the expression for the eigen-solutions of laser modes, the expression for the output laser power, and the expressions for the relations between nonuniform laser medium and phase/intensity distributions of laser modes. Applying the derived expressions in the nonlinear curve-fitti
Nonuniform laser medium will cause the variations of phase and intensity distributions of laser modes. It is difficult to solve the wave equations associated with nonuniform laser medium. In this paper, the potential function of nonuniform laser medium was approximately expressed by the primary three items of its Taylor series expansion, and then coupled into the special function in Helmholtz equations describing the laser modes in a resonator. According to the boundary conditions of a typical resonator, we derived the expression for the eigen-solutions of laser modes, the expression for the output laser power, and the expressions for the relations between nonuniform laser medium and phase/intensity distributions of laser modes. Applying the derived expressions in the nonlinear curve-fitti
2010,
22.
Abstract:
In order to decrease the measuring error of signal processing in laser Doppler velocimeter(LDV), frequency spectrum correction methods for laser Doppler signal were proposed. Basic principles of energy centrobaric correction, ratio correction and phase difference correction were expounded. The three methods processing ideal sinusoidal signals was simulated with different signal frequencies, and so was the ratio method processing sinusoidal signals with different noises and signal-to-noise ratios. The results show that, all the three methods can effectively correct the frequency, the energy centrobaric correction has the lowest precision, and the ratio correction is the fastest and its precision is almost not affected by the change of signal-to-noise ratio. The ratio correction was applied
In order to decrease the measuring error of signal processing in laser Doppler velocimeter(LDV), frequency spectrum correction methods for laser Doppler signal were proposed. Basic principles of energy centrobaric correction, ratio correction and phase difference correction were expounded. The three methods processing ideal sinusoidal signals was simulated with different signal frequencies, and so was the ratio method processing sinusoidal signals with different noises and signal-to-noise ratios. The results show that, all the three methods can effectively correct the frequency, the energy centrobaric correction has the lowest precision, and the ratio correction is the fastest and its precision is almost not affected by the change of signal-to-noise ratio. The ratio correction was applied
2010,
22.
Abstract:
A wide-tunable, low-threshold, extra-cavity singly resonant optical parametric oscillator(OPO) has been reported, which is based on periodically poled MgO:LiNbO3 (PPMgLN). The OPO system, compact and simple, adopts a passively Q-switched Nd:YVO4 laser as the pump source and realizes quasi-phase-matched optical parametric oscillation at room temperature. The threshold value of the OPO system is only 0.27 W (single pulse energy of 4.5 μJ, pulse duration of 35 ns) at 1 064 nm. When the pump power is 1.35 W (pulse energy of 8.2 μJ, pulse duration of 35 ns), an idler output power of 161.9 mW at 3.202 μm, and a signal output power of 98.5 mW at 1.594 μm have been achieved, and this corresponds to a whole (idler+signal) optic-optic conversion efficiency of 19.3%. By shifting the PPMgLN crysta
A wide-tunable, low-threshold, extra-cavity singly resonant optical parametric oscillator(OPO) has been reported, which is based on periodically poled MgO:LiNbO3 (PPMgLN). The OPO system, compact and simple, adopts a passively Q-switched Nd:YVO4 laser as the pump source and realizes quasi-phase-matched optical parametric oscillation at room temperature. The threshold value of the OPO system is only 0.27 W (single pulse energy of 4.5 μJ, pulse duration of 35 ns) at 1 064 nm. When the pump power is 1.35 W (pulse energy of 8.2 μJ, pulse duration of 35 ns), an idler output power of 161.9 mW at 3.202 μm, and a signal output power of 98.5 mW at 1.594 μm have been achieved, and this corresponds to a whole (idler+signal) optic-optic conversion efficiency of 19.3%. By shifting the PPMgLN crysta
2010,
22.
Abstract:
To study the starting characteristic of directly drained CW DF/HF chemical laser (DDCL), a double-nozzle small-scale model of DDCL gas channel was set up, and a series of experiments without secondary flow was conducted with nitrogen and helium as primary flow respectively. The data of experiment, which is conducted with nitrogen and primary nozzles of large area ratio, are far away from the theoretical result. It is believed that, a part of nitrogen has phase transition while it is expanding in the experiment, and then the one-dimension treatment is out of place. In addition, the states of cavity fuels and secondary diluent helium will not change in a CW DF/HF chemical laser, but the area ratio of secondary diluent nozzle must not be very large if the secondary diluent is nitrogen.
To study the starting characteristic of directly drained CW DF/HF chemical laser (DDCL), a double-nozzle small-scale model of DDCL gas channel was set up, and a series of experiments without secondary flow was conducted with nitrogen and helium as primary flow respectively. The data of experiment, which is conducted with nitrogen and primary nozzles of large area ratio, are far away from the theoretical result. It is believed that, a part of nitrogen has phase transition while it is expanding in the experiment, and then the one-dimension treatment is out of place. In addition, the states of cavity fuels and secondary diluent helium will not change in a CW DF/HF chemical laser, but the area ratio of secondary diluent nozzle must not be very large if the secondary diluent is nitrogen.
2010,
22.
Abstract:
The radiation forces of focused partially coherent Bessel vortex beams on a dielectric sphere in the Rayleigh scattering regime are theoretically investigated. Numerical results demonstrate that the magnitude of the radiation forces on a dielectric sphere near the focus point decreases as the topological charge, the coherence length or the parameter α increases. When the topological charge n=0,1, the stable three-dimensional trap can be obtained, and can be used to manipulate the particle with a refractive index lower than that of the ambient media.
The radiation forces of focused partially coherent Bessel vortex beams on a dielectric sphere in the Rayleigh scattering regime are theoretically investigated. Numerical results demonstrate that the magnitude of the radiation forces on a dielectric sphere near the focus point decreases as the topological charge, the coherence length or the parameter α increases. When the topological charge n=0,1, the stable three-dimensional trap can be obtained, and can be used to manipulate the particle with a refractive index lower than that of the ambient media.
2010,
22.
Abstract:
The discharge-pumped KrF excimer was used to amplify ultraviolet ultrashort pulse laser with wavelength of 248.4 nm.The laser energy was amplified from 0.7 mJ to 15 mJ,and the pulse duration was broadened from 550 fs to 1 200 fs, with the beam diameter of 10 mm unchanged. To compress the output pulse duration, the effects of group velocity dispersion and self phase modulation were analyzed,and experimental schemes with four different prism pair were used to introduce negative frequency chirp into the pulse laser in order to compensate the positive frequency chirp introduced by group velocity dispersion and self phase modulation in the CaF2 windows of the amplifer.The results show that if the prism pair is put before the amplifier, the pulse duration can be compressed to 370 fs when the le
The discharge-pumped KrF excimer was used to amplify ultraviolet ultrashort pulse laser with wavelength of 248.4 nm.The laser energy was amplified from 0.7 mJ to 15 mJ,and the pulse duration was broadened from 550 fs to 1 200 fs, with the beam diameter of 10 mm unchanged. To compress the output pulse duration, the effects of group velocity dispersion and self phase modulation were analyzed,and experimental schemes with four different prism pair were used to introduce negative frequency chirp into the pulse laser in order to compensate the positive frequency chirp introduced by group velocity dispersion and self phase modulation in the CaF2 windows of the amplifer.The results show that if the prism pair is put before the amplifier, the pulse duration can be compressed to 370 fs when the le
2010,
22.
Abstract:
At cryogenic temperature, Yb:YAG medium has both good thermal property and high laser performance. Considering that, a 12 kW laser dioder pumped V-shaped cryogenic Yb:YAG laser design has been demonstrated in order to get rep-rated high energy output. Based on the ray tracing method and finite element analysis, the coupling system and cooling scheme were investigated, respectively. In addition, wedge-shaped vacuum window and cryogenic heat pipe schemes have been proposed. The simulation results show that the thermal effect of laser medium is much lower compared with room temperature operated laser, and the design can realize rep-rated high energy output.
At cryogenic temperature, Yb:YAG medium has both good thermal property and high laser performance. Considering that, a 12 kW laser dioder pumped V-shaped cryogenic Yb:YAG laser design has been demonstrated in order to get rep-rated high energy output. Based on the ray tracing method and finite element analysis, the coupling system and cooling scheme were investigated, respectively. In addition, wedge-shaped vacuum window and cryogenic heat pipe schemes have been proposed. The simulation results show that the thermal effect of laser medium is much lower compared with room temperature operated laser, and the design can realize rep-rated high energy output.
2010,
22.
Abstract:
For studying the relationship between breakdown thresholds and laser parameters, numerical simulation for ellipsoidal time and space model of femtosecond laser-induced optical breakdown in water was done at different pulse duration (40 fs to 540 fs), wavelength (400 nm to 1 200 nm) and spot size (0 to 200 μm) with a Runge-Kutta method. The figures of threshold intensity as a function of pulse duration, wavelength or spot size were given via variable-controlled method. Some conclusions were presented about the relationship between threshold intensity and laser parameters. At last, the figures of threshold power, energy, radiant exposure or electric field strength as a function of pulse duration, wavelength or spot size were presented, which gives a further theoretical support for the study
For studying the relationship between breakdown thresholds and laser parameters, numerical simulation for ellipsoidal time and space model of femtosecond laser-induced optical breakdown in water was done at different pulse duration (40 fs to 540 fs), wavelength (400 nm to 1 200 nm) and spot size (0 to 200 μm) with a Runge-Kutta method. The figures of threshold intensity as a function of pulse duration, wavelength or spot size were given via variable-controlled method. Some conclusions were presented about the relationship between threshold intensity and laser parameters. At last, the figures of threshold power, energy, radiant exposure or electric field strength as a function of pulse duration, wavelength or spot size were presented, which gives a further theoretical support for the study
2010,
22.
Abstract:
A novel microelectromechanical systems (MEMS) deformable mirror actuator based on electrostatic repulsive force is presented. The design is based on the principle that asymmetric electric field can generate repulsive force. The actuator can eliminate the pull-in effect which limits the reliability of the conventional electrostatic MEMS deformable mirrors. The actuator consists of five pairs of electrodes, the largest of which is composed of a central mass and a bottom electrode right below it, and the other four of which are positioned on each side of the actuator. The central mass is supported by four L-shaped springs which respectively connecting four anchors on the corners. The resonant frequency and transient response time are simulated by finite element analysis, and they are 4 kHz an
A novel microelectromechanical systems (MEMS) deformable mirror actuator based on electrostatic repulsive force is presented. The design is based on the principle that asymmetric electric field can generate repulsive force. The actuator can eliminate the pull-in effect which limits the reliability of the conventional electrostatic MEMS deformable mirrors. The actuator consists of five pairs of electrodes, the largest of which is composed of a central mass and a bottom electrode right below it, and the other four of which are positioned on each side of the actuator. The central mass is supported by four L-shaped springs which respectively connecting four anchors on the corners. The resonant frequency and transient response time are simulated by finite element analysis, and they are 4 kHz an
2010,
22.
Abstract:
An improved matched filter design method based on the maximum average correlation height(MACH) principle is proposed to recognize the targets in cloud backgrounds. In the process of MACH filter design, a theoretical model of power spectrum density(PSD) is established by curve fitting after statistically analyzing the real cloud backgrounds’ PSD distribution to replace the traditional white noise model. Various features of flight targets are extracted and processed by threshold to get the training set images. Correlation results of targets in various cloud backgrounds show that the average peak to correlation energy ratio is 0.71%, and the peak to clutter ratio is 0.92 of improved matched filter, the cloud backgrounds are well restrained, and the filter is also distortion-invariant to feat
An improved matched filter design method based on the maximum average correlation height(MACH) principle is proposed to recognize the targets in cloud backgrounds. In the process of MACH filter design, a theoretical model of power spectrum density(PSD) is established by curve fitting after statistically analyzing the real cloud backgrounds’ PSD distribution to replace the traditional white noise model. Various features of flight targets are extracted and processed by threshold to get the training set images. Correlation results of targets in various cloud backgrounds show that the average peak to correlation energy ratio is 0.71%, and the peak to clutter ratio is 0.92 of improved matched filter, the cloud backgrounds are well restrained, and the filter is also distortion-invariant to feat
2010,
22.
Abstract:
The calculation method is studied for coupling impedance of coaxial sinusoidal slow wave structure (SWS), which considers the influence of synchronous point on the amplitudes of harmonic waves of quasi-TEM mode. Based on the theory of coupling impedance, the efficiency of a compact 1.6 GHz coaxial relativistic backward wave oscillator (RBWO) is investigated varying the structure parameters of SWS. Numerical results of coupling impedance and results of PIC simulation with KARAT code match well in the linear region, and their differences are analyzed using surface wave theory.
The calculation method is studied for coupling impedance of coaxial sinusoidal slow wave structure (SWS), which considers the influence of synchronous point on the amplitudes of harmonic waves of quasi-TEM mode. Based on the theory of coupling impedance, the efficiency of a compact 1.6 GHz coaxial relativistic backward wave oscillator (RBWO) is investigated varying the structure parameters of SWS. Numerical results of coupling impedance and results of PIC simulation with KARAT code match well in the linear region, and their differences are analyzed using surface wave theory.
2010,
22.
Abstract:
A jiggle particle swarm optimization(JPSO) algorithm has been presented for the multi-parameter optimization of 2D magnetostatic problem. Given a target curve of axial magnetic flux density along the axis of symmetry, it can find rotating axisymmetric magnetic structures whose distribution curve of magnetic flux dnesity is close to the target one. This algorithm is divided into two phases. In the first phase, up-and-down test method (jiggle) is adopted with continuous reference to the best particle’s information. In the second phase, basic particle swarm optimization algorithm is adopted. The JPSO algorithm shows multi-core computer’s potential in engineering design multi-parameter optimization of 2D magnetostatic problems. Even if there is only a few particles, its successive results ca
A jiggle particle swarm optimization(JPSO) algorithm has been presented for the multi-parameter optimization of 2D magnetostatic problem. Given a target curve of axial magnetic flux density along the axis of symmetry, it can find rotating axisymmetric magnetic structures whose distribution curve of magnetic flux dnesity is close to the target one. This algorithm is divided into two phases. In the first phase, up-and-down test method (jiggle) is adopted with continuous reference to the best particle’s information. In the second phase, basic particle swarm optimization algorithm is adopted. The JPSO algorithm shows multi-core computer’s potential in engineering design multi-parameter optimization of 2D magnetostatic problems. Even if there is only a few particles, its successive results ca
2010,
22.
Abstract:
Based on the hollow cathode effect and low-pressure glow discharge empirical formulas，the preliminary design of a miniature hollow cathode plasma electron gun is presented. This kind of gun has a major advantage in that it has no material cathode, can drive current densities larger than thermionic counterparts, can have long lifetime and can operate reliable at fore vacuum gas pressure ranges such as achieved by mechanical pumps. The relationships of beam current, discharge voltage and gas pressure have been experimentally investigated. A electron beam of current 600 mA, pulse width 2 μs is obtained under pressure 2 Pa, discharge voltage 10 kV.
Based on the hollow cathode effect and low-pressure glow discharge empirical formulas，the preliminary design of a miniature hollow cathode plasma electron gun is presented. This kind of gun has a major advantage in that it has no material cathode, can drive current densities larger than thermionic counterparts, can have long lifetime and can operate reliable at fore vacuum gas pressure ranges such as achieved by mechanical pumps. The relationships of beam current, discharge voltage and gas pressure have been experimentally investigated. A electron beam of current 600 mA, pulse width 2 μs is obtained under pressure 2 Pa, discharge voltage 10 kV.
2010,
22.
Abstract:
A solenoid using the double winding technique has been designed to drive a coaxial relativistic backward wave oscillator(RBWO). First, the solenoid parameters were chosen by the particle simulation and practical applications. In addition, the magnetic field distribution was validated by numerical calculations with the Mathcad code and the particle-in-cell(PIC) Karat code. Then the profile of the axial magnetic field distribution was measured by a Tesla-meter based on the Hall effect, and the guiding effect of the field was examined by electrons bombarding a nylon target. Based on the above discussion, the primary experiment with the solenoid was carried out. The measured microwave frequency is 1.61 GHz, with a peak power level of above 864 MW, when the diode voltage is 655 kV and the curre
A solenoid using the double winding technique has been designed to drive a coaxial relativistic backward wave oscillator(RBWO). First, the solenoid parameters were chosen by the particle simulation and practical applications. In addition, the magnetic field distribution was validated by numerical calculations with the Mathcad code and the particle-in-cell(PIC) Karat code. Then the profile of the axial magnetic field distribution was measured by a Tesla-meter based on the Hall effect, and the guiding effect of the field was examined by electrons bombarding a nylon target. Based on the above discussion, the primary experiment with the solenoid was carried out. The measured microwave frequency is 1.61 GHz, with a peak power level of above 864 MW, when the diode voltage is 655 kV and the curre
2010,
22.
Abstract:
A 2-D simulation model of electron movement on the dielectric window surface under HPM in vacuum is established, and the influences of microwave electromagnetic field and dielectric surface electrostatic field are considered. The influences of different emergence angles of electron and microwave electromagnetic parameters are investigated, such as the amplitude and frequency of electric field, and the phase of electric field when electrons are emitted from the surface. Movement trajectories of electrons under complex field and state parameters when electrons return to the dielectric surface are obtained by simulation, such as impact energy and return time. Variation laws of electron movement with emergence angle and microwave electromagnetic parameters are also derived. The emergence angle
A 2-D simulation model of electron movement on the dielectric window surface under HPM in vacuum is established, and the influences of microwave electromagnetic field and dielectric surface electrostatic field are considered. The influences of different emergence angles of electron and microwave electromagnetic parameters are investigated, such as the amplitude and frequency of electric field, and the phase of electric field when electrons are emitted from the surface. Movement trajectories of electrons under complex field and state parameters when electrons return to the dielectric surface are obtained by simulation, such as impact energy and return time. Variation laws of electron movement with emergence angle and microwave electromagnetic parameters are also derived. The emergence angle
2010,
22.
Abstract:
In this paper, a novel microstrip Wilkinson power divider based on artificial transmission lines is proposed. The design consists of recently proposed artificial transmission lines using L-C components instead of conventional microstrip transmission lines. Two interdigital capacitors and a chip resistor were applied to improve output port isolation. A power divider at 915 MHz was designed and fabricated. Compared with conventional Wilkinson power dividers, it features a size reduction of 75%. The bandwidth of the power divider is from 0.49 GHz to 1.2 GHz, the insertion loss is less than 3.2 dB, and the return loss is greater than 10.0 dB. Furthermore, the amplitude balance is within 0.2 dB and the phase balance is better than 1° in its operating band. Measured results show good consistent
In this paper, a novel microstrip Wilkinson power divider based on artificial transmission lines is proposed. The design consists of recently proposed artificial transmission lines using L-C components instead of conventional microstrip transmission lines. Two interdigital capacitors and a chip resistor were applied to improve output port isolation. A power divider at 915 MHz was designed and fabricated. Compared with conventional Wilkinson power dividers, it features a size reduction of 75%. The bandwidth of the power divider is from 0.49 GHz to 1.2 GHz, the insertion loss is less than 3.2 dB, and the return loss is greater than 10.0 dB. Furthermore, the amplitude balance is within 0.2 dB and the phase balance is better than 1° in its operating band. Measured results show good consistent
2010,
22.
Abstract:
An exact analytical expression for the space-charge-limited current of hollow relativistic electron beam in a coaxial waveguide is derived and compared with the existing formula for extremely thin hollow electron beam and that in cylindrical waveguide. Also, the numerical result from nonlinear partial differential equation of potential for the space-charge-limited current of hollow relativistic electron beam in a coaxial wave-guide is given and is much larger than that from the analytical expression. Hollow electron beam has higher space-charge limited current in coaxial waveguide than that in cylindrical waveguide and it higher when electron beam approaches the conductors of waveguide. This theoretical analysis can be used to guide the design of high power microwave coaxial waveguide.
An exact analytical expression for the space-charge-limited current of hollow relativistic electron beam in a coaxial waveguide is derived and compared with the existing formula for extremely thin hollow electron beam and that in cylindrical waveguide. Also, the numerical result from nonlinear partial differential equation of potential for the space-charge-limited current of hollow relativistic electron beam in a coaxial wave-guide is given and is much larger than that from the analytical expression. Hollow electron beam has higher space-charge limited current in coaxial waveguide than that in cylindrical waveguide and it higher when electron beam approaches the conductors of waveguide. This theoretical analysis can be used to guide the design of high power microwave coaxial waveguide.
2010,
22.
Abstract:
Calculation expressions of technical parameters are derived for the waveguide-stripling-coaxial line directional coupler. The impact of structure dimension of the coupler and input frequency on the parameters is studied using Matlab. Numerical results indicate that, included angle has the greatest impact on coupling coefficient and directivity; optimal directivity angle are most sensitive to coupling hole depth, and it varies sharply with input frequency in low frequency range (less tham 2.0 GHz) and becomes much smoother when the frequency goes higher. Thus in the design of this coupler, designed coupling coefficient and directivity could be achieved through adjusting stripline size and coupler position besides the conventional ways of changing aperture size and rotation direction.
Calculation expressions of technical parameters are derived for the waveguide-stripling-coaxial line directional coupler. The impact of structure dimension of the coupler and input frequency on the parameters is studied using Matlab. Numerical results indicate that, included angle has the greatest impact on coupling coefficient and directivity; optimal directivity angle are most sensitive to coupling hole depth, and it varies sharply with input frequency in low frequency range (less tham 2.0 GHz) and becomes much smoother when the frequency goes higher. Thus in the design of this coupler, designed coupling coefficient and directivity could be achieved through adjusting stripline size and coupler position besides the conventional ways of changing aperture size and rotation direction.
2010,
22.
Abstract:
The cross-chairs-shaped resonator(CCSR), a new structure of the planar waveguide periodically loaded with a novel resonant structure, is presented. Theoretical analysis, numerical calculation and simulation results show and verify the properties of 2D left-handed materials (2D LHM) in two frequency bands. Compared with the conventional 2D LHM consisting of orthogonal arrays of wires and split ring resonators, this 2D LHM has some novel properties: double-band-pass, no medium loss, higher power capacity and so on because of the cross-chairs-shaped resonator’s all-metallic structure and special resonant ways. Meanwhile, the CCSR unit cell loading planar waveguide is a new type of planar waveguide dual-bandpass filter with perfect bandpass characteristic and small size.
The cross-chairs-shaped resonator(CCSR), a new structure of the planar waveguide periodically loaded with a novel resonant structure, is presented. Theoretical analysis, numerical calculation and simulation results show and verify the properties of 2D left-handed materials (2D LHM) in two frequency bands. Compared with the conventional 2D LHM consisting of orthogonal arrays of wires and split ring resonators, this 2D LHM has some novel properties: double-band-pass, no medium loss, higher power capacity and so on because of the cross-chairs-shaped resonator’s all-metallic structure and special resonant ways. Meanwhile, the CCSR unit cell loading planar waveguide is a new type of planar waveguide dual-bandpass filter with perfect bandpass characteristic and small size.
2010,
22.
Abstract:
The electromagnetic wave transmission with plane wave incidence through the rough surface of stratified medium is studied through expanding transmission field by plane wave and carrying out Fourier Transform to coordinates. This study method adopts small perturbation method according to Rayleigh hypothesis, and can avoid cumbersome derivation and proof. An exponential distribution rough surface is presented for describing the natural rough surface of stratified medium, and the formula of the transmission coefficient is derived with considering power spectrum density. Numerical results show that, the transmission coefficient grows with increasing dielectric constant real part of intermediate medium, and height fluctuation (root mean square) and correlation length of rough surface, while red
The electromagnetic wave transmission with plane wave incidence through the rough surface of stratified medium is studied through expanding transmission field by plane wave and carrying out Fourier Transform to coordinates. This study method adopts small perturbation method according to Rayleigh hypothesis, and can avoid cumbersome derivation and proof. An exponential distribution rough surface is presented for describing the natural rough surface of stratified medium, and the formula of the transmission coefficient is derived with considering power spectrum density. Numerical results show that, the transmission coefficient grows with increasing dielectric constant real part of intermediate medium, and height fluctuation (root mean square) and correlation length of rough surface, while red
2010,
22.
Abstract:
Beam waveguide (BWG) feed system, composed of a series of flat reflectors, conicoid mirrors and lens can use conicoid mirror and flat mirror as rotating joint to implement mechanical scan of antenna in electromagnetic wave transmission.In this paper, the operating principle of the Cassegrain antenna fed by beam waveguide is analyzed, and the design method of the beam waveguide for the HPM radiating antenna is discussed. Emphasis is placed on a practical HPM radiating antenna fed by beam waveguide. In the antenna system, a dual-reflector antenna with two paraboloids is fed by the beam waveguide feeding system formed by three reflectors, realizing quick scanning of the beam. The antenna can operate at X-band with more than 1 GW power capacity, and its gain is greater than 50 dB.
Beam waveguide (BWG) feed system, composed of a series of flat reflectors, conicoid mirrors and lens can use conicoid mirror and flat mirror as rotating joint to implement mechanical scan of antenna in electromagnetic wave transmission.In this paper, the operating principle of the Cassegrain antenna fed by beam waveguide is analyzed, and the design method of the beam waveguide for the HPM radiating antenna is discussed. Emphasis is placed on a practical HPM radiating antenna fed by beam waveguide. In the antenna system, a dual-reflector antenna with two paraboloids is fed by the beam waveguide feeding system formed by three reflectors, realizing quick scanning of the beam. The antenna can operate at X-band with more than 1 GW power capacity, and its gain is greater than 50 dB.
2010,
22.
Abstract:
The transverse analog feedback system of Hefei light source has been redeveloped. The new improved designs including beam position signal processing unit, DC-component signal removing unit, vector signal computing unit, etc, are described and new system’s commissioning results are discussed. The transverse coupled bunch instability at 200 MeV injection status is experimentally studied. The results show that, the injection damping rate is improved from 1.22 ms to 0.16 ms and the remnant beta oscillation can be suppressed.
The transverse analog feedback system of Hefei light source has been redeveloped. The new improved designs including beam position signal processing unit, DC-component signal removing unit, vector signal computing unit, etc, are described and new system’s commissioning results are discussed. The transverse coupled bunch instability at 200 MeV injection status is experimentally studied. The results show that, the injection damping rate is improved from 1.22 ms to 0.16 ms and the remnant beta oscillation can be suppressed.
2010,
22.
Abstract:
The paper reports the preliminary experiment results of the electron gun based on photo-field emission of carbon nanotubes(CNTs). The quantum efficiency of the CNTs was 3.73×10-5 under the irradiation of the laser with wavelength of 532 nm; the peak pulse current of 3.364 A, corresponding pulse charge of 30 nC were achieved in the experiment. The relation between the photo emission current of the CNTs and the laser power under different high voltage is given.
The paper reports the preliminary experiment results of the electron gun based on photo-field emission of carbon nanotubes(CNTs). The quantum efficiency of the CNTs was 3.73×10-5 under the irradiation of the laser with wavelength of 532 nm; the peak pulse current of 3.364 A, corresponding pulse charge of 30 nC were achieved in the experiment. The relation between the photo emission current of the CNTs and the laser power under different high voltage is given.
2010,
22.
Abstract:
The axially symmetric magnetic lens in the Institute of Modern Physics of the Chinese Academy of Sciences is taken as an example in this paper, and two axially symmetric magnetic lenses are designed: one is the solenoid with iron yokes and the other is the Glaser magnet with tapered poles. The axially symmetric magnetic field produced by the solenoid with iron yokes is more even, and the axially symmetric magnetic field produced by the Glaser magnet with tapered poles is more concentrative. Two physical models are applied for approximate calculation of magnetic field, and the ANSYS finite element method is used to simulate the magnetic field at the same time. Comparison is made between the two different lenses in physics and engineering aspects, and the result is that the solenoid with iro
The axially symmetric magnetic lens in the Institute of Modern Physics of the Chinese Academy of Sciences is taken as an example in this paper, and two axially symmetric magnetic lenses are designed: one is the solenoid with iron yokes and the other is the Glaser magnet with tapered poles. The axially symmetric magnetic field produced by the solenoid with iron yokes is more even, and the axially symmetric magnetic field produced by the Glaser magnet with tapered poles is more concentrative. Two physical models are applied for approximate calculation of magnetic field, and the ANSYS finite element method is used to simulate the magnetic field at the same time. Comparison is made between the two different lenses in physics and engineering aspects, and the result is that the solenoid with iro
2010,
22.
Abstract:
There are always closed orbit distortions and closed orbit shifts produced by various error sources. They are detrimental to beam performance and must be corrected by closed orbit correction and orbit feedback system. Singular value decomposition(SVD) method is currently being used in the closed orbit correction and feedback system in Hefei light source. In this article, the mathematical algorithms for orbit correction and feedback are introduced, especially constrained linear least squares method(CLLS). Compared with SVD method, CLLS method pays more attention to sensitive position. Running results using this method are given, and they show that the orbit reproducibility and beam orbit stability of special sensitive beamline is improved significantly.
There are always closed orbit distortions and closed orbit shifts produced by various error sources. They are detrimental to beam performance and must be corrected by closed orbit correction and orbit feedback system. Singular value decomposition(SVD) method is currently being used in the closed orbit correction and feedback system in Hefei light source. In this article, the mathematical algorithms for orbit correction and feedback are introduced, especially constrained linear least squares method(CLLS). Compared with SVD method, CLLS method pays more attention to sensitive position. Running results using this method are given, and they show that the orbit reproducibility and beam orbit stability of special sensitive beamline is improved significantly.
2010,
22.
Abstract:
Electrochemistry plays a very important role in inertial confinement fusion(ICF) target preparation. This paper reports the preparation of metal foil with theoretical density by electrical chemical machining and metal nanowire array by electrodeposition on anodized aluminum oxide(AAO) template. Ti foils with surface roughness less than 30 nm and Au nanowire arrays with length about 10 μm, diameter about 300 nm were prepared. The choices of electrolyte composition and electrochemical parameters, and diameter and length control of nanowires were investigated.
Electrochemistry plays a very important role in inertial confinement fusion(ICF) target preparation. This paper reports the preparation of metal foil with theoretical density by electrical chemical machining and metal nanowire array by electrodeposition on anodized aluminum oxide(AAO) template. Ti foils with surface roughness less than 30 nm and Au nanowire arrays with length about 10 μm, diameter about 300 nm were prepared. The choices of electrolyte composition and electrochemical parameters, and diameter and length control of nanowires were investigated.
2010,
22.
Abstract:
HfO2 films were deposited by direct current reactive magnetron sputtering on n-type Si(100) substrates and fused silica substrates, respectively. The substrate temperature ranges from room temperature to 500 ℃. The influence of substrate temperature on structure and optical properties of the films was investigated by X-ray diffraction(XRD), spectroscopic ellipsometry(SE) and ultraviolet visible spectroscopy(UV-vis). XRD results show that all deposited films are polycrystalline with monoclinic structure. As the substrate temperature increases, the preferred orientation of (-111) becomes more obvious, and the grain size of HfO2 films increases. SE and UV-vis results demonstrate that, with the substrate temperature increasing, the refractive index increases and the optical band ga
HfO2 films were deposited by direct current reactive magnetron sputtering on n-type Si(100) substrates and fused silica substrates, respectively. The substrate temperature ranges from room temperature to 500 ℃. The influence of substrate temperature on structure and optical properties of the films was investigated by X-ray diffraction(XRD), spectroscopic ellipsometry(SE) and ultraviolet visible spectroscopy(UV-vis). XRD results show that all deposited films are polycrystalline with monoclinic structure. As the substrate temperature increases, the preferred orientation of (-111) becomes more obvious, and the grain size of HfO2 films increases. SE and UV-vis results demonstrate that, with the substrate temperature increasing, the refractive index increases and the optical band ga
2010,
22.
Abstract:
An improved Stoilov algorithm was proposed based on statistical approach, which can remove singularities and large errors to improve measure precision. The optical element defect detection model was constructed by fitting the surface of optical element as well as reconstructing the surface of defect element. The defect on an optical flat was detected with this method and model. The measured depth of scratch is 40 nm.
An improved Stoilov algorithm was proposed based on statistical approach, which can remove singularities and large errors to improve measure precision. The optical element defect detection model was constructed by fitting the surface of optical element as well as reconstructing the surface of defect element. The defect on an optical flat was detected with this method and model. The measured depth of scratch is 40 nm.
2010,
22.
Abstract:
In order to meet the requirement of low density micro-machinable CH foams in ICF, the fabrication of p-divinylbenzene foams by high internal phase emulsion(HIPE) have been introduced. The fabrication conditions were discussed, such as initiator, emulsifier, ratio of styrene and inorganic additive. Then the optimum formula was obtained. Characterization results of different density foams indicate that there are two different porous structures in foams: cells and wall holes. The cells have the diameter of 1~10 μm, and wall holes have the diameter of 0.2~2.0 μm. When the density of foams is 50 mg/cm3, the elastic module of foams is about 5 MPa. By the microfabrication, the foams with the density over 50 mg/cm3 could be machined to cylindrical and sliced targets used in ICF, whose minimum si
In order to meet the requirement of low density micro-machinable CH foams in ICF, the fabrication of p-divinylbenzene foams by high internal phase emulsion(HIPE) have been introduced. The fabrication conditions were discussed, such as initiator, emulsifier, ratio of styrene and inorganic additive. Then the optimum formula was obtained. Characterization results of different density foams indicate that there are two different porous structures in foams: cells and wall holes. The cells have the diameter of 1~10 μm, and wall holes have the diameter of 0.2~2.0 μm. When the density of foams is 50 mg/cm3, the elastic module of foams is about 5 MPa. By the microfabrication, the foams with the density over 50 mg/cm3 could be machined to cylindrical and sliced targets used in ICF, whose minimum si
2010,
22.
Abstract:
The use of visual inspection and image processing technology has implemented the automatic, continuous and non-destructive inspection of 5 μm tungsten wire-array assembly parameters, i.e., the straightness of single wire, the distance between two contiguous wires, and whether foreign body and rupture exist. Image collection and configuration method of this visual inspection system is studied, and a visual inspection experiment system has been built for inspecting Z-pinch wire-array assembly parameters. The results show that the system has the optimal inspection precision of 2 μm and can inspect foreign body and rupture on wires, which can meet the requirement of assembly parameter inspection for Z-pinch wire-arrays.
The use of visual inspection and image processing technology has implemented the automatic, continuous and non-destructive inspection of 5 μm tungsten wire-array assembly parameters, i.e., the straightness of single wire, the distance between two contiguous wires, and whether foreign body and rupture exist. Image collection and configuration method of this visual inspection system is studied, and a visual inspection experiment system has been built for inspecting Z-pinch wire-array assembly parameters. The results show that the system has the optimal inspection precision of 2 μm and can inspect foreign body and rupture on wires, which can meet the requirement of assembly parameter inspection for Z-pinch wire-arrays.
2010,
22.
Abstract:
The KBA microscope imaging is simulated by ray-tracing calculation which can determine the direction of optical axis and obtain geometrical modulation tranfer function(GMTF) of KBA microscope.According to the simulation results, a new method is proposed for the aiming and adjustment of KBA microscope at the laser prototype facility using visible light as the simulated optical axis of KBA microscope. The precision of grazing angle is about 0.25°. Experiment of KBA microscope at the laser prototype facility is implemented using Ni-grids whose period is 20 μm, and clear X-ray image of grids is obtained by CCD camera.
The KBA microscope imaging is simulated by ray-tracing calculation which can determine the direction of optical axis and obtain geometrical modulation tranfer function(GMTF) of KBA microscope.According to the simulation results, a new method is proposed for the aiming and adjustment of KBA microscope at the laser prototype facility using visible light as the simulated optical axis of KBA microscope. The precision of grazing angle is about 0.25°. Experiment of KBA microscope at the laser prototype facility is implemented using Ni-grids whose period is 20 μm, and clear X-ray image of grids is obtained by CCD camera.
2010,
22.
Abstract:
In order to find a powerful assistant computation tool for further analysis and design of multilayer optical coatings, an analytical model is mathematically established for accurate calculation of the first and second derivatives of the spectral coefficients of multilayer optical coatings with respect to layer parameters like thickness, real refractive index and extinction coefficient. It is based on the matrix theory of calculating the spectral coefficients of multilayer optical coatings and is achieved by perfectly using the trace operation of matrix. This partial derivative computation model characterizes the same applicable condition and universality in physics with the matrix theory mentioned above. Thus it can also be applied to any homogenous and isotropic layered multilayer system.
In order to find a powerful assistant computation tool for further analysis and design of multilayer optical coatings, an analytical model is mathematically established for accurate calculation of the first and second derivatives of the spectral coefficients of multilayer optical coatings with respect to layer parameters like thickness, real refractive index and extinction coefficient. It is based on the matrix theory of calculating the spectral coefficients of multilayer optical coatings and is achieved by perfectly using the trace operation of matrix. This partial derivative computation model characterizes the same applicable condition and universality in physics with the matrix theory mentioned above. Thus it can also be applied to any homogenous and isotropic layered multilayer system.
