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RSS2014 Vol. 26, No. 03
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2014,
26: 030201.
doi: 10.3788/HPLPB201426.030201
Abstract:
This review article summarizes the applications of repetitive pulsed power in many fields, such as material development, environment protection, bio- and medical-science, light sources, and high-energy accelerators. The plasma immersion ion implantation and pulsed electron-beam surface treatment have been used in industrial production. Flue-gas and wastewater treatment by pulsed atmospheric discharge are being developed toward practical application. Sterilization and cancer-cell treatment using pulsed electric field have attracted great attention from academic and industrial communities. Plasma generated extreme ultraviolet(EUV) radiation is hopefully going to be used in photo-lithography for mass production in the near future. The thyratrons used on high-energy accelerators will eventually be replaced by power semiconductor devices.
This review article summarizes the applications of repetitive pulsed power in many fields, such as material development, environment protection, bio- and medical-science, light sources, and high-energy accelerators. The plasma immersion ion implantation and pulsed electron-beam surface treatment have been used in industrial production. Flue-gas and wastewater treatment by pulsed atmospheric discharge are being developed toward practical application. Sterilization and cancer-cell treatment using pulsed electric field have attracted great attention from academic and industrial communities. Plasma generated extreme ultraviolet(EUV) radiation is hopefully going to be used in photo-lithography for mass production in the near future. The thyratrons used on high-energy accelerators will eventually be replaced by power semiconductor devices.
2014,
26: 031001.
doi: 10.3788/HPLPB201426.031001
Abstract:
In order to reduce the impact of ejector system exhausts on the optical transmission, design method of emitting exhaust gas to the outside of optical transmission area is proposed. Fluid characteristics for exhaust pipe in ejector system and the influence area of exhausted gas are studied using numerical simulation methods. Based on the comparison results of flow field characteristics of straight pipe and elbow bend pipe, design manners of exhaust pipe which satisfies the engineering requirement are proposed. Under the condition of having no natural wind or having the side toward natural wind, the influence districts of exhausted gas are confirmed by the multiple species transport models with the fixed exhaust velocity of ejector system, and according to the influence area of exhausted gas, the pipe length and arrangement style are discussed.
In order to reduce the impact of ejector system exhausts on the optical transmission, design method of emitting exhaust gas to the outside of optical transmission area is proposed. Fluid characteristics for exhaust pipe in ejector system and the influence area of exhausted gas are studied using numerical simulation methods. Based on the comparison results of flow field characteristics of straight pipe and elbow bend pipe, design manners of exhaust pipe which satisfies the engineering requirement are proposed. Under the condition of having no natural wind or having the side toward natural wind, the influence districts of exhausted gas are confirmed by the multiple species transport models with the fixed exhaust velocity of ejector system, and according to the influence area of exhausted gas, the pipe length and arrangement style are discussed.
2014,
26: 031002.
doi: 10.3788/HPLPB201426.031002
Abstract:
Using the IR imaging system to observe the target, especially Strong thermal radiation target, dynamic range is not enough. In this paper, a dynamic range adjust technology based on self-adaptive to scene characteristic is proposed. This paper describes a method of imaging super-resolution by adjusting the ranges of imaging signals on infrared focal plane array in details. This method includes three steps. The first step is to extract the gray characteristic of the scene needed observing, analyze the gray characteristic of the target, and get the adjust witness for dynamic range adjusting. The second step is to combine with the adaptive filtering algorithm based on LMS, and give the adjusting parameters after filtering on adjust witness. The third step is to complete the dynamic range adaptive adjust on imaging of infrared focal plane array imaging system by using electrical level value to adjust bias voltage. The total scheme is validated in many experiments using the infrared focal plane array imaging system developed by ourselves. The feasibility of this method is proved during experimentsand the quality of imaging is improved evidently.
Using the IR imaging system to observe the target, especially Strong thermal radiation target, dynamic range is not enough. In this paper, a dynamic range adjust technology based on self-adaptive to scene characteristic is proposed. This paper describes a method of imaging super-resolution by adjusting the ranges of imaging signals on infrared focal plane array in details. This method includes three steps. The first step is to extract the gray characteristic of the scene needed observing, analyze the gray characteristic of the target, and get the adjust witness for dynamic range adjusting. The second step is to combine with the adaptive filtering algorithm based on LMS, and give the adjusting parameters after filtering on adjust witness. The third step is to complete the dynamic range adaptive adjust on imaging of infrared focal plane array imaging system by using electrical level value to adjust bias voltage. The total scheme is validated in many experiments using the infrared focal plane array imaging system developed by ourselves. The feasibility of this method is proved during experimentsand the quality of imaging is improved evidently.
2014,
26: 031003.
doi: 10.3788/HPLPB201426.031003
Abstract:
A general approach based on the energetic fragmentation criterion inspired by Grady is considered. Starting from size distribution of fracture advised in our early research, mass distribution law is derived for dynamic failure process in liquid metals. This approach is also discussed and compared with experimental observation of dynamic fragmentation in melted state of laser shocked-loaded tin, and the theoretical curves can give a good comparability with experimental distribution. Further, the major causes of discrepancy between theoretic predictions and experimental observations are discussed, and further work is needed to better understand the evolution of this microspall process.
A general approach based on the energetic fragmentation criterion inspired by Grady is considered. Starting from size distribution of fracture advised in our early research, mass distribution law is derived for dynamic failure process in liquid metals. This approach is also discussed and compared with experimental observation of dynamic fragmentation in melted state of laser shocked-loaded tin, and the theoretical curves can give a good comparability with experimental distribution. Further, the major causes of discrepancy between theoretic predictions and experimental observations are discussed, and further work is needed to better understand the evolution of this microspall process.
2014,
26: 031004.
doi: 10.3788/HPLPB201426.031004
Abstract:
Smile effect is a key problem that reduces the application of laser diode arrays. This paper presents the research on the relation between smile effect and the package technology. It is found that two main parameters affect the smile effect: the uneven pressure on laser chip in soldering and the mismatch of thermal expansion coefficient. Theoretically, the uneven of the pressure can be reduced by using low thermal expansion coefficient contact bar, and the shrinkage difference between laser diode chip and heat sink can be reduced by increasing the cooling rate of the solidification process. Both theoretical and experimental results show that these methods can significantly and fundamentally reduce the smile effect.
Smile effect is a key problem that reduces the application of laser diode arrays. This paper presents the research on the relation between smile effect and the package technology. It is found that two main parameters affect the smile effect: the uneven pressure on laser chip in soldering and the mismatch of thermal expansion coefficient. Theoretically, the uneven of the pressure can be reduced by using low thermal expansion coefficient contact bar, and the shrinkage difference between laser diode chip and heat sink can be reduced by increasing the cooling rate of the solidification process. Both theoretical and experimental results show that these methods can significantly and fundamentally reduce the smile effect.
2014,
26: 031005.
doi: 10.3788/HPLPB201426.031005
Abstract:
An infrared and color visible image fusion method based on Snake model region detection and non-subsampled contourlet transform(NSCT) is presented. In this method, first of all, the luminance component is extracted by using IHS(intensity, hue, saturation) color space conversion for color visible images and the target region of infrared images is detected by adopting Snake model. Then NSCT decomposition is utilized for the luminance component and target replaced infrared image. Image fusion is done by using the largest pixels absolute value sum for the high frequency coefficient and the weighted fusion rules based on brightness mapping technology for the low frequency coefficient. NSCT inverse transform is adopted to obtain the brightness of the image fusion for the fusion coefficients. Finally, the color space inverse transformation is used to acquire fusion images. Experimental results show that the proposed fusion method can not only maintain a high resolution and natural colors of the visible image, but also accurately retain the target information detected in the infrared image. Compared with other methods, fusion images with a better visual effect and comprehensive indicator can be achieved.
An infrared and color visible image fusion method based on Snake model region detection and non-subsampled contourlet transform(NSCT) is presented. In this method, first of all, the luminance component is extracted by using IHS(intensity, hue, saturation) color space conversion for color visible images and the target region of infrared images is detected by adopting Snake model. Then NSCT decomposition is utilized for the luminance component and target replaced infrared image. Image fusion is done by using the largest pixels absolute value sum for the high frequency coefficient and the weighted fusion rules based on brightness mapping technology for the low frequency coefficient. NSCT inverse transform is adopted to obtain the brightness of the image fusion for the fusion coefficients. Finally, the color space inverse transformation is used to acquire fusion images. Experimental results show that the proposed fusion method can not only maintain a high resolution and natural colors of the visible image, but also accurately retain the target information detected in the infrared image. Compared with other methods, fusion images with a better visual effect and comprehensive indicator can be achieved.
2014,
26: 031006.
doi: 10.3788/HPLPB201426.031006
Abstract:
The laser injecting efficiency from free space to small-mode-area single mode fiber is a crucial issue during the operation of supercontinuum generation. Compared with the difficult adjustment and fragile fiber end face using single lens method, an improved laser injecting method is presented. A large-mode-area single mode fiber is employed to couple the free space laser and spliced to the small-mode-area single mode fiber. The experimental results show that the optical efficiency of supercontinuum generation is greatly increased using the improved laser injecting system, whose coupling efficiency is more than 60% due to the easy operation.
The laser injecting efficiency from free space to small-mode-area single mode fiber is a crucial issue during the operation of supercontinuum generation. Compared with the difficult adjustment and fragile fiber end face using single lens method, an improved laser injecting method is presented. A large-mode-area single mode fiber is employed to couple the free space laser and spliced to the small-mode-area single mode fiber. The experimental results show that the optical efficiency of supercontinuum generation is greatly increased using the improved laser injecting system, whose coupling efficiency is more than 60% due to the easy operation.
2014,
26: 031007.
doi: 10.3788/HPLPB201426.031007
Abstract:
Photonic crystal devices in high density integrated optical communication have been widely used. In order to solve space control of the photonic crystal waveguide emitting light beaming, using the method of finite-difference time-domain, the defect waveguide propagation characteristics of photonic crystal waveguide structure are analyzed. Based on optimization of waveguide structure with point defects, through both sides with point defects in the waveguide, the emitting light direction is significantly improved, and the beaming of three-point light interference system is realized. The simulation results show that when the defect state is close to the central band structure, the coupling efficiency of the resonant cavity is higher, when the defect state is close to edge position of the band structure, the coupling efficiency of the resonant cavity is lower, therefore, the selection of point defect in the band 1/4 region can effectively realize the waveguide beaming.
Photonic crystal devices in high density integrated optical communication have been widely used. In order to solve space control of the photonic crystal waveguide emitting light beaming, using the method of finite-difference time-domain, the defect waveguide propagation characteristics of photonic crystal waveguide structure are analyzed. Based on optimization of waveguide structure with point defects, through both sides with point defects in the waveguide, the emitting light direction is significantly improved, and the beaming of three-point light interference system is realized. The simulation results show that when the defect state is close to the central band structure, the coupling efficiency of the resonant cavity is higher, when the defect state is close to edge position of the band structure, the coupling efficiency of the resonant cavity is lower, therefore, the selection of point defect in the band 1/4 region can effectively realize the waveguide beaming.
2014,
26: 031008.
doi: 10.3788/HPLPB201426.031008
Abstract:
A new non-uniformity correction method used in contact image sensor (CIS) scanner is presented, and it could rapidly and efficiently accomplish non-uniformity correction of CIS scanners color image and eliminate the color difference of CIS. To obtain uniform color images, the multi-point segmented one-step method is adopted in calibration process and FPGA is used for correcting. For the resolution of CIS scanner up to 1200 dpi, pattern paper is only captured once to complete the calibration of all color space and correction is accomplished during the acquiring image process, and it takes only 0.125 microsecond. The practical application results show that the output images uniformity is about ten times promotion than that before correction and about three times than that with traditional two-point method.
A new non-uniformity correction method used in contact image sensor (CIS) scanner is presented, and it could rapidly and efficiently accomplish non-uniformity correction of CIS scanners color image and eliminate the color difference of CIS. To obtain uniform color images, the multi-point segmented one-step method is adopted in calibration process and FPGA is used for correcting. For the resolution of CIS scanner up to 1200 dpi, pattern paper is only captured once to complete the calibration of all color space and correction is accomplished during the acquiring image process, and it takes only 0.125 microsecond. The practical application results show that the output images uniformity is about ten times promotion than that before correction and about three times than that with traditional two-point method.
2014,
26: 031009.
doi: 10.3788/HPLPB201426.031009
Abstract:
The fast steering mirror manufactured by adopting piezoelectric ceramics and corresponding control and feedback systems were introduced in this paper. The performance of each fast steering mirror was tested, including the key parameters of response speed, dynamical range and closed loop resolution. Then the experiment with optical control in coherent beam combining system was done when the power of light extraction of four lasers reached 100 W. The results show that the optical axis jitters of four lasers are all less than 1.5 rad (RMS) with closed-loop stability control, which decreases by 80% compared to open-loop results, and the average peak-valley value in far-field increases by 3.8 times.
The fast steering mirror manufactured by adopting piezoelectric ceramics and corresponding control and feedback systems were introduced in this paper. The performance of each fast steering mirror was tested, including the key parameters of response speed, dynamical range and closed loop resolution. Then the experiment with optical control in coherent beam combining system was done when the power of light extraction of four lasers reached 100 W. The results show that the optical axis jitters of four lasers are all less than 1.5 rad (RMS) with closed-loop stability control, which decreases by 80% compared to open-loop results, and the average peak-valley value in far-field increases by 3.8 times.
2014,
26: 031010.
doi: 10.3788/HPLPB201426.031010
Abstract:
Based on the non-Kolmogorov spectrum, using the extended Huygens-Fresnel principle and the definition of second-order moments of the Wigner distribution function (WDF), the analytical expressions for the propagation factors of partially coherent Hermite-Ganssian (H-G) beams propagating through non-Kolmogorov atmospheric turbulence are derived, and used to study the influence of non-Kolmogorov atmospheric turbulence on the propagation factors of partially coherent H-G beams. It is shown that the smaller the propagation distances, the outer scale, the general structure constant, the spatial coherence length, and the larger the inner scale, the beam orders, the less the propagation of partially coherent H-G beams is affected by non-Kolmogorov atmospheric turbulence, the better the beam quality. When the general exponent is 3.11, the beam quality of partially coherent H-G beams is the poorest through atmospheric turbulence.
Based on the non-Kolmogorov spectrum, using the extended Huygens-Fresnel principle and the definition of second-order moments of the Wigner distribution function (WDF), the analytical expressions for the propagation factors of partially coherent Hermite-Ganssian (H-G) beams propagating through non-Kolmogorov atmospheric turbulence are derived, and used to study the influence of non-Kolmogorov atmospheric turbulence on the propagation factors of partially coherent H-G beams. It is shown that the smaller the propagation distances, the outer scale, the general structure constant, the spatial coherence length, and the larger the inner scale, the beam orders, the less the propagation of partially coherent H-G beams is affected by non-Kolmogorov atmospheric turbulence, the better the beam quality. When the general exponent is 3.11, the beam quality of partially coherent H-G beams is the poorest through atmospheric turbulence.
2014,
26: 031011.
doi: 10.3788/HPLPB201426.031011
Abstract:
In order to enable the liquid crystal atmosphere turbulence simulator with the ability to simulate the atmospheric turbulence in real time, this paper puts forward a new method of liquid crystal atmosphere turbulence simulator wavefront generation based on Compute Unified Device Architecture. The calculation method of wavefront generation is introduced according to the characteristics of liquid crystal atmosphere turbulence simulator, which has high resolution and high precision. The Compute Unified Device Architecture is discussed. Then, a wavefront generation model is built with parallel optimization and share memory optimization. Finally, contrast experimental results by using CPU and GPU to generate the distortion wavefront are given. The results show that it takes only 2 ms for GPU to generate a wavefront with a resolution of 256256 and 192 Zernike polynomials, which is two orders of magnitude less than that using CPU, and satisfies the real-time wavefront generate requirements.
In order to enable the liquid crystal atmosphere turbulence simulator with the ability to simulate the atmospheric turbulence in real time, this paper puts forward a new method of liquid crystal atmosphere turbulence simulator wavefront generation based on Compute Unified Device Architecture. The calculation method of wavefront generation is introduced according to the characteristics of liquid crystal atmosphere turbulence simulator, which has high resolution and high precision. The Compute Unified Device Architecture is discussed. Then, a wavefront generation model is built with parallel optimization and share memory optimization. Finally, contrast experimental results by using CPU and GPU to generate the distortion wavefront are given. The results show that it takes only 2 ms for GPU to generate a wavefront with a resolution of 256256 and 192 Zernike polynomials, which is two orders of magnitude less than that using CPU, and satisfies the real-time wavefront generate requirements.
2014,
26: 031012.
doi: 10.3788/HPLPB201426.031012
Abstract:
Based on the working principle and measurement peculiarity of laser velocimeter and the working peculiarity of inertial navigation system(INS), an integrated navigation method was proposed which could be used to realize autonomous high-accuracy positioning and orientation of land vehicles. The error model of the three-beam laser velocimeter used in vehicle positioning and orientation was deduced which was combined with error model of strapdown inertial navigation system(SINS). Kalman filter states of integrated navigation were chosen, and measurement model was deduced. At last, simulation of the SINS/laser velocimeter integrated positioning and orientation method was carried out, and the correlated results were presented, by which the method proposed in this paper was validated.
Based on the working principle and measurement peculiarity of laser velocimeter and the working peculiarity of inertial navigation system(INS), an integrated navigation method was proposed which could be used to realize autonomous high-accuracy positioning and orientation of land vehicles. The error model of the three-beam laser velocimeter used in vehicle positioning and orientation was deduced which was combined with error model of strapdown inertial navigation system(SINS). Kalman filter states of integrated navigation were chosen, and measurement model was deduced. At last, simulation of the SINS/laser velocimeter integrated positioning and orientation method was carried out, and the correlated results were presented, by which the method proposed in this paper was validated.
2014,
26: 031013.
doi: 10.3788/HPLPB201426.031013
Abstract:
Using ZEMAX optical design software to simulate a multi-chip laser diode fiber coupling module, 12 single-chip laser diodes with wavelength of 808 nm being coupled into the core diameter of output fiber which is set as 105 microns with a numerical aperture of 0.22, each single-chip laser diode has an output power of 10 W, the fiber end face will have an output power of 116.84 W with a coupling efficiency of 97.36% and a brightness of 8.88 MW/(cm2sr). Finally, optical fiber and single-chip semiconductor laser installation error on the influence of the fiber coupling efficiency is analyzed using ZEMAX and ORIGIN software. It is concluded that the severity of the error influence on the optical coupling efficiency from heavy to light: the vertical axis error, the axial error, the angle error.
Using ZEMAX optical design software to simulate a multi-chip laser diode fiber coupling module, 12 single-chip laser diodes with wavelength of 808 nm being coupled into the core diameter of output fiber which is set as 105 microns with a numerical aperture of 0.22, each single-chip laser diode has an output power of 10 W, the fiber end face will have an output power of 116.84 W with a coupling efficiency of 97.36% and a brightness of 8.88 MW/(cm2sr). Finally, optical fiber and single-chip semiconductor laser installation error on the influence of the fiber coupling efficiency is analyzed using ZEMAX and ORIGIN software. It is concluded that the severity of the error influence on the optical coupling efficiency from heavy to light: the vertical axis error, the axial error, the angle error.
2014,
26: 031014.
doi: 10.3788/HPLPB201426.031014
Abstract:
Scramjet inlet flow disturbance was studied for the case when energy impulse was added on the wall of scramjet inlet. The flow is governed by the the 3-D Reynolds averaged Navier-Stokes equations. To split the viscosity flux and the convective flux of the N-S equations, the second order central scheme and the ROE scheme were adopted respectively. With the implicit Gauss-Seidel scheme, the code was advanced in time. The k- turbulence model was used for turbulence simulations. The characteristics of hypersonic flat with energy addition were tested in a hypersonic tunnel by applying a high speed schlieren system. The results show that the numerical pressure contour agrees well with the experimental schlieren photograph. Energy addition could induce strong shock wave interaction which might change the mass flow rate of scramjet inlet sharply. In other words, energy addition can decrease the performance of scramjet inlet flow and inlet unstart might take place at this rate.
Scramjet inlet flow disturbance was studied for the case when energy impulse was added on the wall of scramjet inlet. The flow is governed by the the 3-D Reynolds averaged Navier-Stokes equations. To split the viscosity flux and the convective flux of the N-S equations, the second order central scheme and the ROE scheme were adopted respectively. With the implicit Gauss-Seidel scheme, the code was advanced in time. The k- turbulence model was used for turbulence simulations. The characteristics of hypersonic flat with energy addition were tested in a hypersonic tunnel by applying a high speed schlieren system. The results show that the numerical pressure contour agrees well with the experimental schlieren photograph. Energy addition could induce strong shock wave interaction which might change the mass flow rate of scramjet inlet sharply. In other words, energy addition can decrease the performance of scramjet inlet flow and inlet unstart might take place at this rate.
2014,
26: 031015.
doi: 10.3788/HPLPB201426.031015
Abstract:
The effect of different amounts of Cr in cladding powders on corrosion and wear resistances of cladding layers was investigated by means of X-ray diffractometry (XRD), scanning electron microscopy (SEM), energy dispersive spectrometer (EDS), potentiodynamic polarization and abrasive wear test. The results showed that phases of cladding layers were -Fe, TiC, VC and TiVC2. Retained austenite and Cr3C2 would appear with Cr content increasing, and Cr3C2 was long strip and distributed alone or together. The corrosion and wear resistances of cladding layers increased firstly and then decreased with the increasing of Cr addition. Moderate amount of Cr could improve hardness and corrosion resistance of cladding layers significantly. The hardness of the cladding layer with 3.0 % Cr reached 1090HV0.2. The weight loss of cladding layer was only about 1/26 of Q235 steel under the same abrasive wear condition. When the addition of Cr was 9.0 %, the cladding layer showed the best corrosion resistance and its corrosion resistance was about 3.26 times than that of the cladding layer without Cr.
The effect of different amounts of Cr in cladding powders on corrosion and wear resistances of cladding layers was investigated by means of X-ray diffractometry (XRD), scanning electron microscopy (SEM), energy dispersive spectrometer (EDS), potentiodynamic polarization and abrasive wear test. The results showed that phases of cladding layers were -Fe, TiC, VC and TiVC2. Retained austenite and Cr3C2 would appear with Cr content increasing, and Cr3C2 was long strip and distributed alone or together. The corrosion and wear resistances of cladding layers increased firstly and then decreased with the increasing of Cr addition. Moderate amount of Cr could improve hardness and corrosion resistance of cladding layers significantly. The hardness of the cladding layer with 3.0 % Cr reached 1090HV0.2. The weight loss of cladding layer was only about 1/26 of Q235 steel under the same abrasive wear condition. When the addition of Cr was 9.0 %, the cladding layer showed the best corrosion resistance and its corrosion resistance was about 3.26 times than that of the cladding layer without Cr.
2014,
26: 031016.
doi: 10.3788/HPLPB201426.031016
Abstract:
Ni-Fe-B-Si-Nb amorphous composite coating was fabricated using laser cladding plus laser remelting process using high powder diode laser on mild steel surface. The phase and microstructure of the coating were studied using X-ray diffraction (XRD), scanning electron microscope (SEM) and transmission electron microscope (TEM). The mechanical properties of the coating were studied by nano-indentation tests. The results showed that Ni40.8Fe27.2B18Si10Nb4 amorphous composite coating was obtained when the laser cladding power was 0.8 kW, the scanning speed was 0.36 m/min, the powder feed rate was 12g/min, the laser remelting power was 3.5 kW and the scanning speed was 8 m/min. It was found that the laser remelting coatings exhibited dense amorphous structure matrix embedded by some crystal phases((Fe,Ni) and NbC). Nano-indentation test results indicated that the microhardness and elastic modulus of the remelting coating were far higher than that of the laser cladded coating, and they were also higher than that of BMGs with the same nominal compositions. The average microhardness and elastic modulus of the laser remelting coating were 1 227.9 HV and 277.4 GPa, respectively.
Ni-Fe-B-Si-Nb amorphous composite coating was fabricated using laser cladding plus laser remelting process using high powder diode laser on mild steel surface. The phase and microstructure of the coating were studied using X-ray diffraction (XRD), scanning electron microscope (SEM) and transmission electron microscope (TEM). The mechanical properties of the coating were studied by nano-indentation tests. The results showed that Ni40.8Fe27.2B18Si10Nb4 amorphous composite coating was obtained when the laser cladding power was 0.8 kW, the scanning speed was 0.36 m/min, the powder feed rate was 12g/min, the laser remelting power was 3.5 kW and the scanning speed was 8 m/min. It was found that the laser remelting coatings exhibited dense amorphous structure matrix embedded by some crystal phases((Fe,Ni) and NbC). Nano-indentation test results indicated that the microhardness and elastic modulus of the remelting coating were far higher than that of the laser cladded coating, and they were also higher than that of BMGs with the same nominal compositions. The average microhardness and elastic modulus of the laser remelting coating were 1 227.9 HV and 277.4 GPa, respectively.
2014,
26: 031017.
doi: 10.3788/HPLPB201426.031017
Abstract:
To compensate atmospheric turbulent aberration adopting adaptive optics (AO) system, the effect of anisoplanatic error is unavoidable. With the spacial spectral filtering method, the single anisoplanatism and multiplex anisoplanatism are systemically studied, and series of general formulae are obtained. Based on these theories, the ratio of different Zernike mode component in angle or focal anisoplanatic error is analysed. Aiming at special AO system, the components of anisoplanatic error coming from different altitudinal atmosphere are studied. In practical application, the beacon and AO system run mode should be optimized according to practical intention.
To compensate atmospheric turbulent aberration adopting adaptive optics (AO) system, the effect of anisoplanatic error is unavoidable. With the spacial spectral filtering method, the single anisoplanatism and multiplex anisoplanatism are systemically studied, and series of general formulae are obtained. Based on these theories, the ratio of different Zernike mode component in angle or focal anisoplanatic error is analysed. Aiming at special AO system, the components of anisoplanatic error coming from different altitudinal atmosphere are studied. In practical application, the beacon and AO system run mode should be optimized according to practical intention.
2014,
26: 032001.
doi: 10.3788/HPLPB201426.032001
Abstract:
The backscattered light diagnostic system is an important measurement tool for the ICF experiments. The basic configuration and the optical path of the backscattered light diagnostic system implemented on Shenguang Ⅲ prototype facility are summarized in the paper. Aiming at improving veracity and simplifying the calibration process, a novel full aperture light beam calibration method of transmission and spectrum response is described in the paper. High power laser and white Xe lamp are chosen as calibration resource and a peculiar optical path is erected for modulating the light beam into a full aperture distribution so that the distributing of the backscattered light on the diagnostic system are simulated. Using the method, the transmission and spectrum response are calibrated and several data are shown in the paper. The calibration results show that the SRS branch has a limited wavelength of 400 nm while the path has a poor transmittance at 527 nm.
The backscattered light diagnostic system is an important measurement tool for the ICF experiments. The basic configuration and the optical path of the backscattered light diagnostic system implemented on Shenguang Ⅲ prototype facility are summarized in the paper. Aiming at improving veracity and simplifying the calibration process, a novel full aperture light beam calibration method of transmission and spectrum response is described in the paper. High power laser and white Xe lamp are chosen as calibration resource and a peculiar optical path is erected for modulating the light beam into a full aperture distribution so that the distributing of the backscattered light on the diagnostic system are simulated. Using the method, the transmission and spectrum response are calibrated and several data are shown in the paper. The calibration results show that the SRS branch has a limited wavelength of 400 nm while the path has a poor transmittance at 527 nm.
2014,
26: 032002.
doi: 10.3788/HPLPB201426.032002
Abstract:
The surface of quartz components was decorated by inductively coupled plasma (ICP) sculpture technology with CF4/Ar/O2 mixture gas. The effects of gas flow rate on etching rate, surface roughness and morphology were analyzed in detail. The results show that the surface properties were influenced by the etching effect of CF4 as well as the bombardment of Ar. A reasonable flow ratio of them was determined to improve the surface roughness. Furthermore, by optical microscopy analysis, some important parameters were determined so that the etching process was optimized. This research provides a reference for the study of surface modification of fused quartz components to improve their optical performances.
The surface of quartz components was decorated by inductively coupled plasma (ICP) sculpture technology with CF4/Ar/O2 mixture gas. The effects of gas flow rate on etching rate, surface roughness and morphology were analyzed in detail. The results show that the surface properties were influenced by the etching effect of CF4 as well as the bombardment of Ar. A reasonable flow ratio of them was determined to improve the surface roughness. Furthermore, by optical microscopy analysis, some important parameters were determined so that the etching process was optimized. This research provides a reference for the study of surface modification of fused quartz components to improve their optical performances.
2014,
26: 032003.
doi: 10.3788/HPLPB201426.032003
Abstract:
The mid-spatial frequency error of high precision optical surface is crucial to the performance of high-energy laser system. To assure the performance and stability of the system, the low frequency error and high frequency error of the optical lens surface must be strictly controlled, the mid-spatial frequency error must also be strictly limited. In this paper, the relationship between empirical mode decomposition-Wigner-Ville distribution (EMD-WVD) method and power spectrum density is analyzed, and EMD-WVD diagnosis method is applied to identifying and locating the mid-spatial frequency error of the precision optical surface. The experimental results show that, with EMD-WVD method, the mid-spatial frequency error distribution of optical surface can be located in 15-27 mm and the spatial frequency is 0.1 mm-1, the interference of cross-term caused by multi-component signal whose spatial frequency is about 1.0-1.5 mm-1 can also be reduced, which enhances the identification accuracy of mid-spatial frequency error.
The mid-spatial frequency error of high precision optical surface is crucial to the performance of high-energy laser system. To assure the performance and stability of the system, the low frequency error and high frequency error of the optical lens surface must be strictly controlled, the mid-spatial frequency error must also be strictly limited. In this paper, the relationship between empirical mode decomposition-Wigner-Ville distribution (EMD-WVD) method and power spectrum density is analyzed, and EMD-WVD diagnosis method is applied to identifying and locating the mid-spatial frequency error of the precision optical surface. The experimental results show that, with EMD-WVD method, the mid-spatial frequency error distribution of optical surface can be located in 15-27 mm and the spatial frequency is 0.1 mm-1, the interference of cross-term caused by multi-component signal whose spatial frequency is about 1.0-1.5 mm-1 can also be reduced, which enhances the identification accuracy of mid-spatial frequency error.
2014,
26: 032004.
doi: 10.3788/HPLPB201426.032004
Abstract:
The measurement principle of DD neutron yield diagnosis by indium activation is introduced, and the uncertainty sources of neutron yield diagnosis are analyzed. The measurement uncertainty of DD neutron yield consists of the sensitivity calibrating uncertainty, the net-count uncertainty of radioactive rays, the measurement uncertainty of the solid angle and the random error of the activation system. The calibrating uncertainties of activation sensitivity are determined by such causes including the neutron energy variety in the accelerator neutron source and the measurement error of background neutron of accelerator room. The influence of cosmic rays on the net-count measurement of radioactive rays is analyzed. The main uncertainty source of neutron yield diagnosis in different magnitude range is given, and the improved method of the calibrated activation sensitivity is introduced. The uncertainty of neutron yield diagnosis is calculated based on the experimental data. The result shows that the relative standard uncertainty of the activation system which is calibrated on the accelerator using the associated particle method is 4.3%. When the neutron yield is below 1010, the measurement uncertainty is higher than 7%, and it is mainly caused by the net-count error of radioactive rays. The measurement uncertainty is lower than 7% when the neutron yield is higher than 1010, and it is mainly caused by the uncertainty of calibrated sensitivity.
The measurement principle of DD neutron yield diagnosis by indium activation is introduced, and the uncertainty sources of neutron yield diagnosis are analyzed. The measurement uncertainty of DD neutron yield consists of the sensitivity calibrating uncertainty, the net-count uncertainty of radioactive rays, the measurement uncertainty of the solid angle and the random error of the activation system. The calibrating uncertainties of activation sensitivity are determined by such causes including the neutron energy variety in the accelerator neutron source and the measurement error of background neutron of accelerator room. The influence of cosmic rays on the net-count measurement of radioactive rays is analyzed. The main uncertainty source of neutron yield diagnosis in different magnitude range is given, and the improved method of the calibrated activation sensitivity is introduced. The uncertainty of neutron yield diagnosis is calculated based on the experimental data. The result shows that the relative standard uncertainty of the activation system which is calibrated on the accelerator using the associated particle method is 4.3%. When the neutron yield is below 1010, the measurement uncertainty is higher than 7%, and it is mainly caused by the net-count error of radioactive rays. The measurement uncertainty is lower than 7% when the neutron yield is higher than 1010, and it is mainly caused by the uncertainty of calibrated sensitivity.
2014,
26: 032005.
doi: 10.3788/HPLPB201426.032005
Abstract:
In order to observe the amplified emission of rare earth complexes, three Nd(Ⅲ) complexes were successfully synthesized using three carboxylic acids (H3BTC, H6MTA and H6CCA) as ligands and characterized by elemental analysis, ICP and FTIR. Thermostability was studied by TGA spectra. Fluorescence properties were investigated by fluorescence spectra. The fluorescence spectra of the three complexes were composed of typical Nd(Ⅲ) ions in near infrared emissions, assigned to transitions of 4F3/24I9/2, 4F3/24I11/2 and 4F3/24I13/2. The results indicated that prepared Nd(Ⅲ) complexes showed considerable thermostability and well fluorescence properties, which would make them promising materials for laser active medium.
In order to observe the amplified emission of rare earth complexes, three Nd(Ⅲ) complexes were successfully synthesized using three carboxylic acids (H3BTC, H6MTA and H6CCA) as ligands and characterized by elemental analysis, ICP and FTIR. Thermostability was studied by TGA spectra. Fluorescence properties were investigated by fluorescence spectra. The fluorescence spectra of the three complexes were composed of typical Nd(Ⅲ) ions in near infrared emissions, assigned to transitions of 4F3/24I9/2, 4F3/24I11/2 and 4F3/24I13/2. The results indicated that prepared Nd(Ⅲ) complexes showed considerable thermostability and well fluorescence properties, which would make them promising materials for laser active medium.
2014,
26: 032006.
doi: 10.3788/HPLPB201426.032006
Abstract:
To study the stimulated Brillouin scattering (SBS) and stimulated Raman scattering(SRS) light produced during the inertial confinement fusion (ICF) studies on SG-Ⅲ prototype laser facility, the spectra of scattered light from vacuum hohlraum and gas filled hohlraum are measured using a new backscatter light diagnostic system. Experimental results show that the gas filled hohlraums produce more SRS light than the vacuum hohlraums under the same experimental parameters. Meanwhile, the scattered light will be reduced with the application of smoothing into optical module. The temporal evolution of the intensity and spectra of the scattered light can be recorded by this new backscatter light diagnostic system, which is valuable for the studies of ICF.
To study the stimulated Brillouin scattering (SBS) and stimulated Raman scattering(SRS) light produced during the inertial confinement fusion (ICF) studies on SG-Ⅲ prototype laser facility, the spectra of scattered light from vacuum hohlraum and gas filled hohlraum are measured using a new backscatter light diagnostic system. Experimental results show that the gas filled hohlraums produce more SRS light than the vacuum hohlraums under the same experimental parameters. Meanwhile, the scattered light will be reduced with the application of smoothing into optical module. The temporal evolution of the intensity and spectra of the scattered light can be recorded by this new backscatter light diagnostic system, which is valuable for the studies of ICF.
2014,
26: 032007.
doi: 10.3788/HPLPB201426.032007
Abstract:
In order to investigate the distribution of copper particles in poly-4-methyl-1-pentene (PMP) low density foams, the high resolution X-ray computer tomography was used to scan PMP/Cu samples and the CCD camera to record the images. After image processing and 3D reconstruction, 3D spatial distribution of the copper particles in PMP/Cu foams was obtained. 3D visualization shows that copper particles are aggregated in the PMP foams, copper particle aggregates with different sizes have distinctly different morphologies, that is, small aggregates tend to be spherical while big aggregates are relatively longer and like a short stick, which agrees well with the results obtained by high resolution electron microscopy. The research results show that the high resolution X-ray computer tomography can be used to observe the high Z metal particles doped in low density porous materials without destructing the samples.
In order to investigate the distribution of copper particles in poly-4-methyl-1-pentene (PMP) low density foams, the high resolution X-ray computer tomography was used to scan PMP/Cu samples and the CCD camera to record the images. After image processing and 3D reconstruction, 3D spatial distribution of the copper particles in PMP/Cu foams was obtained. 3D visualization shows that copper particles are aggregated in the PMP foams, copper particle aggregates with different sizes have distinctly different morphologies, that is, small aggregates tend to be spherical while big aggregates are relatively longer and like a short stick, which agrees well with the results obtained by high resolution electron microscopy. The research results show that the high resolution X-ray computer tomography can be used to observe the high Z metal particles doped in low density porous materials without destructing the samples.
2014,
26: 032008.
doi: 10.3788/HPLPB201426.032008
Abstract:
For the control of the polarization property and intensity uniformity of optical field near the entrance of the target chamber in indirect drive Inertial Confinement Fusion (ICF), two-dimensional spectral angular dispersion (2-D SSD), random phase plate (RPP), combined with orthogonal polarization control plate (OPCP) have been employed. Influence on the polarization property and intensity uniformity in and near the focal plane by using OPCP has been numerically simulated and theoretically analyzed, and the choice of the number of elements of OPCP has been discussed. The results show that OPCP with different number of elements exhibits different extent of influence on the polarization property and intensity uniformity of optical field in and near the focal plane, and that the polarization property of optical field is not sensitive to defocus. In addition, defocus will degrade the intensity uniformity more or less, but the effect would be reduced by appropriately increasing the number of elements of OPCP.
For the control of the polarization property and intensity uniformity of optical field near the entrance of the target chamber in indirect drive Inertial Confinement Fusion (ICF), two-dimensional spectral angular dispersion (2-D SSD), random phase plate (RPP), combined with orthogonal polarization control plate (OPCP) have been employed. Influence on the polarization property and intensity uniformity in and near the focal plane by using OPCP has been numerically simulated and theoretically analyzed, and the choice of the number of elements of OPCP has been discussed. The results show that OPCP with different number of elements exhibits different extent of influence on the polarization property and intensity uniformity of optical field in and near the focal plane, and that the polarization property of optical field is not sensitive to defocus. In addition, defocus will degrade the intensity uniformity more or less, but the effect would be reduced by appropriately increasing the number of elements of OPCP.
2014,
26: 032009.
doi: 10.3788/HPLPB201426.032009
Abstract:
In order to improve the theory on plane swinging polishing, the removal model of plane swinging polishing is founded based on Preston equation, and the relationship between the removal appearance and the machining parameters is acquired through removal simulation of every point in the case of different machining parameters in Matlab. A validity test on a fused silicon with an aperture of 430 mm430 mm was performed in different parameters, the results through contrasting the removal appearance after simulating and the surface appearance after processing show that this removal model can correctly forecast the removal quantity in different machining parameters, this proves that the model can accurately and effectively control the swinging polishing process.
In order to improve the theory on plane swinging polishing, the removal model of plane swinging polishing is founded based on Preston equation, and the relationship between the removal appearance and the machining parameters is acquired through removal simulation of every point in the case of different machining parameters in Matlab. A validity test on a fused silicon with an aperture of 430 mm430 mm was performed in different parameters, the results through contrasting the removal appearance after simulating and the surface appearance after processing show that this removal model can correctly forecast the removal quantity in different machining parameters, this proves that the model can accurately and effectively control the swinging polishing process.
2014,
26: 032010.
doi: 10.3788/HPLPB201426.032010
Abstract:
The debris mitigation is a major challenge for all high-peak-power lasers system. Costly, long lead time focusing parabolas need to be protected from target debris. In order to solve the problem, we employed some preliminary research. In this work, the optical properties of three kinds of thin films (fluorinated ethylene propylene (FEP), perfluoroalkoxy copolymer (PFA) and ethane-tetrafluoroethylene copolymer (ETFE)) were investigated with respect to their application as laser debris shields. The results indicate the transmittance of FEP film at 355 nm is the highest in that of the three films reaching about 93%, though the three thin films all present good transmittance. Thus, the transmittance wavefront and the laser induced damage of FEP film were further investigated. The result indicates that the wavefront error of FEP film is about 1.06 . The damage test was performed with a 355 nm neodymium: Yttrium aluminum garnet (Nd:YAG) laser with a 9.3 ns pulse duration, and it is found that the highest non-damage fluence for FEP film is 10.35 J/cm2 and the 100% damage fluence is 11.48 J/cm2.
The debris mitigation is a major challenge for all high-peak-power lasers system. Costly, long lead time focusing parabolas need to be protected from target debris. In order to solve the problem, we employed some preliminary research. In this work, the optical properties of three kinds of thin films (fluorinated ethylene propylene (FEP), perfluoroalkoxy copolymer (PFA) and ethane-tetrafluoroethylene copolymer (ETFE)) were investigated with respect to their application as laser debris shields. The results indicate the transmittance of FEP film at 355 nm is the highest in that of the three films reaching about 93%, though the three thin films all present good transmittance. Thus, the transmittance wavefront and the laser induced damage of FEP film were further investigated. The result indicates that the wavefront error of FEP film is about 1.06 . The damage test was performed with a 355 nm neodymium: Yttrium aluminum garnet (Nd:YAG) laser with a 9.3 ns pulse duration, and it is found that the highest non-damage fluence for FEP film is 10.35 J/cm2 and the 100% damage fluence is 11.48 J/cm2.
2014,
26: 033001.
doi: 10.3788/HPLPB201426.033001
Abstract:
The mechanism of high order mode excitation in high gain relativistic klystron amplifier is explored in the 2D and 3D PIC simulations. The impact of the asymmetric mode excitation is excluded as the 2D simulation result is in accord with the 3D simulation. The formula for startup current of high order mode excitation is developed based on theoretical model. And RF lossy material is introduced to suppress high order mode self-oscillation. Mode control is realized in the simulation with the RF output power of 1.95 GW, and the corresponding gain is 62.8 dB.
The mechanism of high order mode excitation in high gain relativistic klystron amplifier is explored in the 2D and 3D PIC simulations. The impact of the asymmetric mode excitation is excluded as the 2D simulation result is in accord with the 3D simulation. The formula for startup current of high order mode excitation is developed based on theoretical model. And RF lossy material is introduced to suppress high order mode self-oscillation. Mode control is realized in the simulation with the RF output power of 1.95 GW, and the corresponding gain is 62.8 dB.
2014,
26: 033002.
doi: 10.3788/HPLPB201426.033002
Abstract:
Properties of traveling wave-beam interaction in a thick helix slow-wave structure (SWS) are investigated for a round electron beam. The hot dispersion equation is obtained using the self-consistent field theory, and the small signal analysis is carried out including the effects of the electron beam parameters and the helixs thickness. The numerical results show that the bandwidth and the small-signal gain of the thick helix traveling wave tube (TWT) increase with the increasing beam current and beam radius; while the beam voltage does not obviously influence the small signal gain. And the small-signal gain increases as the thickness of the helix SWS structure increases, however, the bandwidth broadens a little. The presented analysis will be useful for the design of the high power TWT with thick helix circuit.
Properties of traveling wave-beam interaction in a thick helix slow-wave structure (SWS) are investigated for a round electron beam. The hot dispersion equation is obtained using the self-consistent field theory, and the small signal analysis is carried out including the effects of the electron beam parameters and the helixs thickness. The numerical results show that the bandwidth and the small-signal gain of the thick helix traveling wave tube (TWT) increase with the increasing beam current and beam radius; while the beam voltage does not obviously influence the small signal gain. And the small-signal gain increases as the thickness of the helix SWS structure increases, however, the bandwidth broadens a little. The presented analysis will be useful for the design of the high power TWT with thick helix circuit.
2014,
26: 033003.
doi: 10.3788/HPLPB201426.033003
Abstract:
An Chebyshev tapered transmission line TEM horn antenna is designed, and the working principle, impedance characteristics, transmission characteristics and radiation characteristics are studied based on numerical simulation. Compared to conventional linear TEM horn antenna, the Chebyshev tapered transmission line TEM horn antenna has lower reflection, wider band and higher radiation efficiency. The wider the input pulse is, the better performance the antenna has. The effect of maximal reflection coefficient on radiation performance of antenna is analysed. The results show that if the input pulse is narrow, we should select the larger reflection coefficient antenna.
An Chebyshev tapered transmission line TEM horn antenna is designed, and the working principle, impedance characteristics, transmission characteristics and radiation characteristics are studied based on numerical simulation. Compared to conventional linear TEM horn antenna, the Chebyshev tapered transmission line TEM horn antenna has lower reflection, wider band and higher radiation efficiency. The wider the input pulse is, the better performance the antenna has. The effect of maximal reflection coefficient on radiation performance of antenna is analysed. The results show that if the input pulse is narrow, we should select the larger reflection coefficient antenna.
2014,
26: 033004.
doi: 10.3788/HPLPB201426.033004
Abstract:
For the first time, the coaxial interlaced ridge-disk-loaded waveguide as slow-wave structure is presented, the software HFSS is introduced to simulate and calculate dispersion relation and coupling impedance. It is found that the change of structure parameter affects the high frequency characteristics. The results indicate that the coaxial interlaced ridge disk loaded waveguide could get a very weak dispersion and its bandwidth is better than non coaxial disk loaded waveguide. Meanwhile the coaxial interlaced ridge-disk-loaded waveguide has lower phase velocity than other coaxial structure. When it is used as the slow-wave structure of the traveling wave tube, the operating voltage decreases. Because the coaxial interlaced ridge-disk-loaded waveguide is a new all-metal structure with the advantage of high power capability and lower losses, it has a large potential application in millimeter and sub-millimeter wave traveling-wave tubes.
For the first time, the coaxial interlaced ridge-disk-loaded waveguide as slow-wave structure is presented, the software HFSS is introduced to simulate and calculate dispersion relation and coupling impedance. It is found that the change of structure parameter affects the high frequency characteristics. The results indicate that the coaxial interlaced ridge disk loaded waveguide could get a very weak dispersion and its bandwidth is better than non coaxial disk loaded waveguide. Meanwhile the coaxial interlaced ridge-disk-loaded waveguide has lower phase velocity than other coaxial structure. When it is used as the slow-wave structure of the traveling wave tube, the operating voltage decreases. Because the coaxial interlaced ridge-disk-loaded waveguide is a new all-metal structure with the advantage of high power capability and lower losses, it has a large potential application in millimeter and sub-millimeter wave traveling-wave tubes.
2014,
26: 033005.
doi: 10.3788/HPLPB201426.033005
Abstract:
Periodically distributed metallic rods were introduced into the inner and outer conductors of the coaxial transmission line to form a two dimensional metallic photonic crystal structure. The circuit model of the metallic photonic crystal loaded transmission line was built up and the frequency characteristic of the model was studied. It is found that, the structure has two characteristic frequencies; the first band gap starts from the zero frequency and ends at the first characteristic frequency, and the first pass-band starts from the first characteristic frequency and ends at the second. A finite metallic rod array structure was simulated by the commercial software CST Microwave Studio. Because of the finite dimension of photonic crystals in the propagation direction, there exists a pass-band characterized by multi-peaked variations. The electromagnetic property of each propagation peak was analyzed, and its dispersion characteristics were studied.
Periodically distributed metallic rods were introduced into the inner and outer conductors of the coaxial transmission line to form a two dimensional metallic photonic crystal structure. The circuit model of the metallic photonic crystal loaded transmission line was built up and the frequency characteristic of the model was studied. It is found that, the structure has two characteristic frequencies; the first band gap starts from the zero frequency and ends at the first characteristic frequency, and the first pass-band starts from the first characteristic frequency and ends at the second. A finite metallic rod array structure was simulated by the commercial software CST Microwave Studio. Because of the finite dimension of photonic crystals in the propagation direction, there exists a pass-band characterized by multi-peaked variations. The electromagnetic property of each propagation peak was analyzed, and its dispersion characteristics were studied.
2014,
26: 033006.
doi: 10.3788/HPLPB201426.033006
Abstract:
As the frequency spectrum of ultra-wideband(UWB) short electromagnetic pulses can cover the GPS frequency band, it can make threat to GPS receiver. The relationships between interference effects and parameters of UWB short electromagnetic pulses of high pulse repetition frequency(PRF) are studied from the aspects of theoretical analysis, numerical simulation and experimentation. The results show that if an integer multiple of PRF can fall into the GPS frequency band, the UWB short electromagnetic pulses will make strong interference effects on GPS receivers, and the pulse amplitude required to achieve the same interference effects is reducing in proportion to the PRF increasing, namely the product of pulse amplitude and PRF is constant；otherwise the interference effects will be unconspicuous.
As the frequency spectrum of ultra-wideband(UWB) short electromagnetic pulses can cover the GPS frequency band, it can make threat to GPS receiver. The relationships between interference effects and parameters of UWB short electromagnetic pulses of high pulse repetition frequency(PRF) are studied from the aspects of theoretical analysis, numerical simulation and experimentation. The results show that if an integer multiple of PRF can fall into the GPS frequency band, the UWB short electromagnetic pulses will make strong interference effects on GPS receivers, and the pulse amplitude required to achieve the same interference effects is reducing in proportion to the PRF increasing, namely the product of pulse amplitude and PRF is constant；otherwise the interference effects will be unconspicuous.
2014,
26: 033101.
doi: 10.3788/HPLPB201426.033101
Abstract:
The terahertz time-domain spectroscopy (THz-TDS) was applied to investigate the characteristics of terahertz absorption spectra and refractivities of multi-walled carbon nanotubes (MWCNTs). Five types of MWCNTs with different tube diameters and lengths were studied. The experiment results show that, in the frequency range of 0.2 to 2.0 THz, no characteristic absorption of MWCNTs is found but the absorption strengths increase with the frequency, which can be fitted into lines with different slopes. Furthermore, the terahertz absorption strengths of MWCNTs are proportional to the tube diameters and lengths. However, the refractivities decrease exponentially with the increase of frequency. The tube diameter is an important factor affecting the refractivities, while the influence of tube length can be neglected.
The terahertz time-domain spectroscopy (THz-TDS) was applied to investigate the characteristics of terahertz absorption spectra and refractivities of multi-walled carbon nanotubes (MWCNTs). Five types of MWCNTs with different tube diameters and lengths were studied. The experiment results show that, in the frequency range of 0.2 to 2.0 THz, no characteristic absorption of MWCNTs is found but the absorption strengths increase with the frequency, which can be fitted into lines with different slopes. Furthermore, the terahertz absorption strengths of MWCNTs are proportional to the tube diameters and lengths. However, the refractivities decrease exponentially with the increase of frequency. The tube diameter is an important factor affecting the refractivities, while the influence of tube length can be neglected.
2014,
26: 033102.
doi: 10.3788/HPLPB201426.035105
Abstract:
Ghost pulses in free electron laser THz (FEL-THz) facility in CAEP are studied. The generation reasons and the impact of ghost pulses on the facility are analyzed. With electron dynamic simulation, thermal simulation, Monte Carlo simulation and prototype experiment discussion, the impact of ghost pulses is proved to include three aspects: the damage to interceptive measurement equipment, the thermal effects on the beam-line caused by beam wall loss, and higher radiation protection requirements. The results indicate that the ghost pulse is an important reason to limit the FEL-THz operation and should be eliminated. The method of eliminating ghost pulses is also discussed briefly.
Ghost pulses in free electron laser THz (FEL-THz) facility in CAEP are studied. The generation reasons and the impact of ghost pulses on the facility are analyzed. With electron dynamic simulation, thermal simulation, Monte Carlo simulation and prototype experiment discussion, the impact of ghost pulses is proved to include three aspects: the damage to interceptive measurement equipment, the thermal effects on the beam-line caused by beam wall loss, and higher radiation protection requirements. The results indicate that the ghost pulse is an important reason to limit the FEL-THz operation and should be eliminated. The method of eliminating ghost pulses is also discussed briefly.
2014,
26: 033201.
doi: 10.3788/HPLPB201426.033201
Abstract:
In order to detect corona discharge radiation signal in complex electromagnetic environment, a simulation platform was built to analysis the time domain and frequency domain features of corona discharge radiation signal. Combined with the noise frequency distribution measured in natural environment, the arrow-band detection technology was used. By designing a specific band directional antenna, designing a high bandwidth low-noise amplifier, and the application of digital processing terminals, etc., a high-sensitivity detection system for weak signals was built. And the corona discharge radiation signal was successfully detected by the system at the distance of 600 meters. The feasibility of detecting corona discharge radiation signal in remote detection was proved by the experimental results. And an important detection technique for targets was provided.
In order to detect corona discharge radiation signal in complex electromagnetic environment, a simulation platform was built to analysis the time domain and frequency domain features of corona discharge radiation signal. Combined with the noise frequency distribution measured in natural environment, the arrow-band detection technology was used. By designing a specific band directional antenna, designing a high bandwidth low-noise amplifier, and the application of digital processing terminals, etc., a high-sensitivity detection system for weak signals was built. And the corona discharge radiation signal was successfully detected by the system at the distance of 600 meters. The feasibility of detecting corona discharge radiation signal in remote detection was proved by the experimental results. And an important detection technique for targets was provided.
2014,
26: 033202.
doi: 10.3788/HPLPB201426.033202
Abstract:
The borehole radar is a kind of geophysical exploration tool based on high-frequency pulse electromagnetic (EM) wave transmission for detecting subsurface information. In this work, the transmission characteristics of transient EM wave were studied for designing borehole radar system and interpreting subsurface information. Propagation speed and attenuation coefficient were theoretically studied to find out the distance between the target and the borehole, as well as the maximum detection range of the borehole radar. Based on the theoretical study, we designed a borehole radar system. In order to verify the system, field experiments were carried out in a limestone stratum. The experimental results demonstrate that the system can effectively detect a metal target 8 m away from the borehole.
The borehole radar is a kind of geophysical exploration tool based on high-frequency pulse electromagnetic (EM) wave transmission for detecting subsurface information. In this work, the transmission characteristics of transient EM wave were studied for designing borehole radar system and interpreting subsurface information. Propagation speed and attenuation coefficient were theoretically studied to find out the distance between the target and the borehole, as well as the maximum detection range of the borehole radar. Based on the theoretical study, we designed a borehole radar system. In order to verify the system, field experiments were carried out in a limestone stratum. The experimental results demonstrate that the system can effectively detect a metal target 8 m away from the borehole.
2014,
26: 033203.
doi: 10.3788/HPLPB201426.033203
Abstract:
The random coupling model(RCM) not only inherits the advantage of traditional electromagnetic deterministic prediction methods, but also overcomes the problem that deterministic methods would cause a poor prediction of an electrical large chaotic cavity. Focusing on the state-of-the-art statistical electromagnetics and prediction in complex cavities, we studied the key technologies and notions of non-ergodic short ray coupling, random shape aperture coupling and statistical energy analysis in multi-cavity interconnection situation in both theory and testing, which provides references for research in RCM statistical electromagnetic testing.
The random coupling model(RCM) not only inherits the advantage of traditional electromagnetic deterministic prediction methods, but also overcomes the problem that deterministic methods would cause a poor prediction of an electrical large chaotic cavity. Focusing on the state-of-the-art statistical electromagnetics and prediction in complex cavities, we studied the key technologies and notions of non-ergodic short ray coupling, random shape aperture coupling and statistical energy analysis in multi-cavity interconnection situation in both theory and testing, which provides references for research in RCM statistical electromagnetic testing.
2014,
26: 034001.
doi: 10.3788/HPLPB201426.034001
Abstract:
Cadmium zinc telluride (CZT) is one of the preferred materials for the fabrication of X-ray and gamma-ray detector. The purpose of this work was to evaluate limitations of pixellated CdZnTe detectors thickness used under different photon energy and find the best possible compromise for different detector thicknesses. Simulations and experimental investigations of the energy spectrum, energy resolution and photopeak efficiency measured by pixellated CdZnTe detectors have been performed using 241Am and 137Cs irradiation sources. It is concluded that thick CdZnTe provides high energy resolution and photopeak efficiency for high energy of 662 keV, but it suffers from increased tailing and charge loss for low energy of 59.5 keV; while thin devices can provide better performance.
Cadmium zinc telluride (CZT) is one of the preferred materials for the fabrication of X-ray and gamma-ray detector. The purpose of this work was to evaluate limitations of pixellated CdZnTe detectors thickness used under different photon energy and find the best possible compromise for different detector thicknesses. Simulations and experimental investigations of the energy spectrum, energy resolution and photopeak efficiency measured by pixellated CdZnTe detectors have been performed using 241Am and 137Cs irradiation sources. It is concluded that thick CdZnTe provides high energy resolution and photopeak efficiency for high energy of 662 keV, but it suffers from increased tailing and charge loss for low energy of 59.5 keV; while thin devices can provide better performance.
2014,
26: 034002.
doi: 10.3788/HPLPB201426.034002
Abstract:
Gelatin-ring experiment is a technique of studying Rayleigh-Taylor instability growth in a cylindrically convergent geometry. The customary measurement is the high-speed photography which is difficult to distinguish the turbulent mixing zone (TMZ). Therefore, the low and middle energy X-ray radiography system was conducted using the commercial flash X-ray tube and home-made camera. The evolutions of the gelatin-rings inner and outer surfaces were clearly observed by X-ray radiography in different time and gelatins concentration，including rebound of inner surface and turbulent mixing. The experimental results show that the process of the gelatin-rings TMZ can be distinguished by X-ray radiography. Therefore, X-ray radiography is an effective diagnostic in the gelatin-ring implosion experiment.
Gelatin-ring experiment is a technique of studying Rayleigh-Taylor instability growth in a cylindrically convergent geometry. The customary measurement is the high-speed photography which is difficult to distinguish the turbulent mixing zone (TMZ). Therefore, the low and middle energy X-ray radiography system was conducted using the commercial flash X-ray tube and home-made camera. The evolutions of the gelatin-rings inner and outer surfaces were clearly observed by X-ray radiography in different time and gelatins concentration，including rebound of inner surface and turbulent mixing. The experimental results show that the process of the gelatin-rings TMZ can be distinguished by X-ray radiography. Therefore, X-ray radiography is an effective diagnostic in the gelatin-ring implosion experiment.
2014,
26: 034003.
doi: 10.3788/HPLPB201426.034003
Abstract:
Four types of bipolar integrated circuits were irradiated at different elevated temperature with two different dose rates, after that, the corresponding sensitive parameters were extracted and analyzed. The results prove that elevated temperature irradiation could provide a conservative estimation for the radiation damage at low dose rate when the optimum irradiation temperature is selected. The optimum irradiation temperature increases with the dose rate but decreases with the total dose. With the same total dose and dose rate, the optimum irradiation temperatures of bipolar integrated circuits with NPN input stage are lower than those with PNP input stage.
Four types of bipolar integrated circuits were irradiated at different elevated temperature with two different dose rates, after that, the corresponding sensitive parameters were extracted and analyzed. The results prove that elevated temperature irradiation could provide a conservative estimation for the radiation damage at low dose rate when the optimum irradiation temperature is selected. The optimum irradiation temperature increases with the dose rate but decreases with the total dose. With the same total dose and dose rate, the optimum irradiation temperatures of bipolar integrated circuits with NPN input stage are lower than those with PNP input stage.
2014,
26: 034004.
doi: 10.3788/HPLPB201426.034004
Abstract:
The mechanism of transient noise of CCD cameras induced by neutrons was analyzed. On the neutron beams of 14 MeV and 2.5 MeV, the transient noise of two different CCD cameras was measured at different fluences and different incidence angles. The preliminary results were drawn from the experiment. Transient noise induced by neutron usually appears as sharp spikes or impulses affecting one or a small cluster of pixels. The results are consistent with theoretical estimates. We also obtained the variation characteristics of transient noise induced by neutrons of different fluences, or different energies, or different incidence angles. In addition, we investigated the transient noise as a function of the size of CCD pixel.
The mechanism of transient noise of CCD cameras induced by neutrons was analyzed. On the neutron beams of 14 MeV and 2.5 MeV, the transient noise of two different CCD cameras was measured at different fluences and different incidence angles. The preliminary results were drawn from the experiment. Transient noise induced by neutron usually appears as sharp spikes or impulses affecting one or a small cluster of pixels. The results are consistent with theoretical estimates. We also obtained the variation characteristics of transient noise induced by neutrons of different fluences, or different energies, or different incidence angles. In addition, we investigated the transient noise as a function of the size of CCD pixel.
2014,
26: 034005.
doi: 10.3788/HPLPB201426.034005
Abstract:
A 265 mm long magnetic focusing femtosecond streak tube with a prepositive traveling wave deflector was theoretically designed. The initial parameters of the electrons emitted both from an ideal point and a slit on the surface of the photoelectric cathode were sampled with Monte Carlo method. The trajectory of the electrons were followed in the CST particle studio, after which the distribution of the electrons on the best image plane and the transit time of the electrons were statistically analyzed. To evaluate the characteristics of the streak tube, this paper also calculated the modulation transform function. The results show that the diameter of the effective area on the photoelectric cathode reaches up to 6 mm, while the amplification rate turns to be 2.4~2.5. By conservative estimates, the time resolution is expected to reach 245 fs.
A 265 mm long magnetic focusing femtosecond streak tube with a prepositive traveling wave deflector was theoretically designed. The initial parameters of the electrons emitted both from an ideal point and a slit on the surface of the photoelectric cathode were sampled with Monte Carlo method. The trajectory of the electrons were followed in the CST particle studio, after which the distribution of the electrons on the best image plane and the transit time of the electrons were statistically analyzed. To evaluate the characteristics of the streak tube, this paper also calculated the modulation transform function. The results show that the diameter of the effective area on the photoelectric cathode reaches up to 6 mm, while the amplification rate turns to be 2.4~2.5. By conservative estimates, the time resolution is expected to reach 245 fs.
2014,
26: 034006.
doi: 10.3788/HPLPB201426.034006
Abstract:
This paper describes all-process direct simulation of active neutron multiplicity counting on New Pile LaboratoryNeutron Multiplicity Counter (NPL-NMC). Twenty-eight hemispheroidal shell uranium components with an inner radius of 1.2 cm were simulated by MCNPX code, which had different mass but the same enrichment and density. The relation curve between coupling and multiplication was obtained. The mass deviation of simulation measurement was within 1.5% for the hemispheroid and hemispheroidal-shell (inner radius 1.2 cm) uranium components, while the mass deviation was lower 5%-10% for the hemispheroidal-shell (inner radius 3.2 cm) and cylinder(inner radius 6, 8 cm) uranium components.
This paper describes all-process direct simulation of active neutron multiplicity counting on New Pile LaboratoryNeutron Multiplicity Counter (NPL-NMC). Twenty-eight hemispheroidal shell uranium components with an inner radius of 1.2 cm were simulated by MCNPX code, which had different mass but the same enrichment and density. The relation curve between coupling and multiplication was obtained. The mass deviation of simulation measurement was within 1.5% for the hemispheroid and hemispheroidal-shell (inner radius 1.2 cm) uranium components, while the mass deviation was lower 5%-10% for the hemispheroidal-shell (inner radius 3.2 cm) and cylinder(inner radius 6, 8 cm) uranium components.
2014,
26: 034007.
doi: 10.3788/HPLPB201426.034007
Abstract:
Aiming at the urgent needs for modulation technique of electronic packet width, we propose a compact symmetric type electron packet width modulation technique. The core of which is the introduction of the carefully chosen alternating electric field, which imposes differential energy modulation on electrons of different part in the electron packet, achieving the purpose of modulating the width of the electron packet. The details are given, including the choosing of the alternating electric field, pulse modulation amplitude relationship and the transverse confinement of the axial magnetic field. The requirements for both compression and broadening modulation in different types of modulating electric field are obtained. The example demonstrates its validity.
Aiming at the urgent needs for modulation technique of electronic packet width, we propose a compact symmetric type electron packet width modulation technique. The core of which is the introduction of the carefully chosen alternating electric field, which imposes differential energy modulation on electrons of different part in the electron packet, achieving the purpose of modulating the width of the electron packet. The details are given, including the choosing of the alternating electric field, pulse modulation amplitude relationship and the transverse confinement of the axial magnetic field. The requirements for both compression and broadening modulation in different types of modulating electric field are obtained. The example demonstrates its validity.
2014,
26: 034008.
doi: 10.3788/HPLPB201426.034008
Abstract:
A calculation method of core porosity based on core target data is proposed as a strategy to solve the problems caused by the current method based on industrial CT images which usually uses local region in images. The key of this method lies in the accurate extraction of the core target from industrial CT images. On the basis of a research of the structure and position relations of the core target and ambient noises in CT images, an effective method is proposed to accurately extract core target from industrial CT images. According to this method, the core porosity of a single CT image can be obtained by calculating the ratio of pore pixels to target pixels, with core target in industrial CT images used as data source. As for the core porosity based on a sequence of CT images, it can appeal to the calculation of the mean value of core porosity of each image in this sequence. Finally, this paper illustrates the accuracy and effectiveness of the method proposed in this research with an example of core porosity calculation based on a sequence of industrial CT images of a core sample.
A calculation method of core porosity based on core target data is proposed as a strategy to solve the problems caused by the current method based on industrial CT images which usually uses local region in images. The key of this method lies in the accurate extraction of the core target from industrial CT images. On the basis of a research of the structure and position relations of the core target and ambient noises in CT images, an effective method is proposed to accurately extract core target from industrial CT images. According to this method, the core porosity of a single CT image can be obtained by calculating the ratio of pore pixels to target pixels, with core target in industrial CT images used as data source. As for the core porosity based on a sequence of CT images, it can appeal to the calculation of the mean value of core porosity of each image in this sequence. Finally, this paper illustrates the accuracy and effectiveness of the method proposed in this research with an example of core porosity calculation based on a sequence of industrial CT images of a core sample.
2014,
26: 035001.
doi: 10.3788/HPLPB201426.035001
Abstract:
A parallelized finite-difference time-domain(FDTD) method for simulating the near-fields of bounded wave electromagnetic pulse (EMP) simulator with distributed terminator and parallel plate is presented. The effects of some model-parameters of simulator on the fields of the points at the half-height in the working volume are simulated and analyzed. The results show that, the rise-time of electric field at some points decreases as the distance along x-axis between the point and the source decreases; if the ratio of the transitional lines maximum width to the maximum height is 2, the rise-time of electric field at testing points is small while the FWHM is large as the width of the below PEC plate is equal to the transitional lines maximum width; as the projection length of transitional line increases, the peak value of electric field at the points with the same distance from the source along x-axis increase while the rise-time of eclectic field decreases, but the decreasement of rise-time tends stable. In addition, the rise-time of electric field at the same points as the simulator fed through the coaxial transmission line is smaller than that of the simulator fed by electric fields on the source plane, and the FWHM is larger, but the waveforms of electric are similar.
A parallelized finite-difference time-domain(FDTD) method for simulating the near-fields of bounded wave electromagnetic pulse (EMP) simulator with distributed terminator and parallel plate is presented. The effects of some model-parameters of simulator on the fields of the points at the half-height in the working volume are simulated and analyzed. The results show that, the rise-time of electric field at some points decreases as the distance along x-axis between the point and the source decreases; if the ratio of the transitional lines maximum width to the maximum height is 2, the rise-time of electric field at testing points is small while the FWHM is large as the width of the below PEC plate is equal to the transitional lines maximum width; as the projection length of transitional line increases, the peak value of electric field at the points with the same distance from the source along x-axis increase while the rise-time of eclectic field decreases, but the decreasement of rise-time tends stable. In addition, the rise-time of electric field at the same points as the simulator fed through the coaxial transmission line is smaller than that of the simulator fed by electric fields on the source plane, and the FWHM is larger, but the waveforms of electric are similar.
2014,
26: 035002.
doi: 10.3788/HPLPB201426.035002
Abstract:
Based on the single particle theory and integral arithmetic, the ALFA code is exploited to analyze the energy deposition of non-thermal alpha particles in cylindrical and spherical magnetized targets. It is found that, the energy deposition of alpha particles in the cylindrical magnetized target is larger than that in the spherical one under the same background magnetic field, D-T plasma density and plasma temperature; there is a work region of magnetic field for average energy deposition of alpha particles. If the magnetic field exceeds the work region, the average energy deposition stays at a constant nearly. As for the different geometry scale, the work region of the magnetic field affecting the energy deposition of alpha particles appears different. The alpha particle energy deposition increases with the D-T plasma density.
Based on the single particle theory and integral arithmetic, the ALFA code is exploited to analyze the energy deposition of non-thermal alpha particles in cylindrical and spherical magnetized targets. It is found that, the energy deposition of alpha particles in the cylindrical magnetized target is larger than that in the spherical one under the same background magnetic field, D-T plasma density and plasma temperature; there is a work region of magnetic field for average energy deposition of alpha particles. If the magnetic field exceeds the work region, the average energy deposition stays at a constant nearly. As for the different geometry scale, the work region of the magnetic field affecting the energy deposition of alpha particles appears different. The alpha particle energy deposition increases with the D-T plasma density.
2014,
26: 035003.
doi: 10.3788/HPLPB201426.035003
Abstract:
Based on the simulation model of the space location relationship between electromagnetic pulse (EMP) bomb and phased-array radar antenna, the coverage ratio of the antenna and other parameters were discussed. The influence of trajectory deviation on the coverage area of the antenna was analyzed, and simulation was also carried out. The simulation results show that some relevant parameters including initiating height and fall point accuracy can influence the coverage area to the phased-array radar antenna. In order to reach the best damage to the target, the accuracy of initiating height, trajectory tilt angle, roll angle and other parameters, and the power density of the target should be considered synthetically.
Based on the simulation model of the space location relationship between electromagnetic pulse (EMP) bomb and phased-array radar antenna, the coverage ratio of the antenna and other parameters were discussed. The influence of trajectory deviation on the coverage area of the antenna was analyzed, and simulation was also carried out. The simulation results show that some relevant parameters including initiating height and fall point accuracy can influence the coverage area to the phased-array radar antenna. In order to reach the best damage to the target, the accuracy of initiating height, trajectory tilt angle, roll angle and other parameters, and the power density of the target should be considered synthetically.
2014,
26: 035004.
doi: 10.3788/HPLPB201426.035004
Abstract:
In order to achieve a low-density powder explosives line synchronization initiation, an exploding wire line initiation system was developed. Three low-inductance parallel capacitors were used in the energy storage device with a total capacity of 12 F. A 1.5 kV pulse was employed to the primary of the trigger pulse transformer. The pulse transformer generated a 40 kV pulse to trigger the high-voltage switch. A 50 kV/100 kA high-voltage field distortion switch was developed. The system achieved a 73 kA pulse into the exploding wire. High-speed framing camera was used to obtain the image of the exploding wire explosion. The experimental results showed that the synchronization during the expanding process of the exploding wire was preferable. The line initiation system was successfully applied to explosion expanding ring experiment.
In order to achieve a low-density powder explosives line synchronization initiation, an exploding wire line initiation system was developed. Three low-inductance parallel capacitors were used in the energy storage device with a total capacity of 12 F. A 1.5 kV pulse was employed to the primary of the trigger pulse transformer. The pulse transformer generated a 40 kV pulse to trigger the high-voltage switch. A 50 kV/100 kA high-voltage field distortion switch was developed. The system achieved a 73 kA pulse into the exploding wire. High-speed framing camera was used to obtain the image of the exploding wire explosion. The experimental results showed that the synchronization during the expanding process of the exploding wire was preferable. The line initiation system was successfully applied to explosion expanding ring experiment.
2014,
26: 035005.
doi: 10.3788/HPLPB201426.035005
Abstract:
Electron energy distribution was calculated according to current and voltage waveforms. The characteristics of X-ray spectrum in series diode and four-channel parallel diode were calculated using Monte Carlo simulation model. The numerical results indicate that the total energies of X-ray fluence of two diodes are 76.50, 3.74 mJ/cm2 respectively; average photon energies are 81.13, 60.77 keV respectively. The dose distribution of series diode in a surface is saddle shape, and the dose uniformity of two diodes in 452 and 2700 cm2 areas is 1.70∶1, less than 6.30∶1 respectively. Bremsstrahlung conversion efficiency of electron beams in the two diodes is 0.29%, 0.32% respectively.
Electron energy distribution was calculated according to current and voltage waveforms. The characteristics of X-ray spectrum in series diode and four-channel parallel diode were calculated using Monte Carlo simulation model. The numerical results indicate that the total energies of X-ray fluence of two diodes are 76.50, 3.74 mJ/cm2 respectively; average photon energies are 81.13, 60.77 keV respectively. The dose distribution of series diode in a surface is saddle shape, and the dose uniformity of two diodes in 452 and 2700 cm2 areas is 1.70∶1, less than 6.30∶1 respectively. Bremsstrahlung conversion efficiency of electron beams in the two diodes is 0.29%, 0.32% respectively.
2014,
26: 035101.
doi: 10.3788/HPLPB201426.035101
Abstract:
Julien Barr proposed a new approach of the statistical theory to the analysis of high-gain free-electron laser at saturation in 2004. This new approach was developed and generalized in this paper to the case of different initial phase space distribution of the electron beam, and a Gaussian momentum distribution which was more practical was calculated. The calculating difficulties from this more practical momentum initial distribution were resolved by multiple integral techniques. For comparison and verification, a direct numerical simulation code was developed. In the cases of two kinds of initial electron beam energy distribution, analysis was conducted respectively of the radiation intensity, bunching parameters and electron distribution in phase space at saturation of free-electron-laser. It is shown that the results by this new statistical method are in good coincident with the corresponding numerical simulation. It is also shown that under the conditions we investigated the difference between the result of the initial distribution of Gaussian and that of water bag is not significant.
Julien Barr proposed a new approach of the statistical theory to the analysis of high-gain free-electron laser at saturation in 2004. This new approach was developed and generalized in this paper to the case of different initial phase space distribution of the electron beam, and a Gaussian momentum distribution which was more practical was calculated. The calculating difficulties from this more practical momentum initial distribution were resolved by multiple integral techniques. For comparison and verification, a direct numerical simulation code was developed. In the cases of two kinds of initial electron beam energy distribution, analysis was conducted respectively of the radiation intensity, bunching parameters and electron distribution in phase space at saturation of free-electron-laser. It is shown that the results by this new statistical method are in good coincident with the corresponding numerical simulation. It is also shown that under the conditions we investigated the difference between the result of the initial distribution of Gaussian and that of water bag is not significant.
2014,
26: 035102.
doi: 10.3788/HPLPB201426.035102
Abstract:
Based on the principle of energy balance and SRIM statistical method, the parameters of heavy ion beams and strong electron beams generating warm dense matter (WDM) are presented. According to the electron radiant energy loss and beam utilization, better homogenization and higher availability were shown in the WDM generated by electron beams with the kinetic energy of 1-10 MeV, and the WDM with wider range was generated by heavy ion beams.
Based on the principle of energy balance and SRIM statistical method, the parameters of heavy ion beams and strong electron beams generating warm dense matter (WDM) are presented. According to the electron radiant energy loss and beam utilization, better homogenization and higher availability were shown in the WDM generated by electron beams with the kinetic energy of 1-10 MeV, and the WDM with wider range was generated by heavy ion beams.
2014,
26: 035103.
doi: 10.3788/HPLPB201426.035103
Abstract:
In beam diagnostics of the particle accelerator, the acquired bunch-by-bunch beam position data have to be filtered by a noise-reduction process in order to get higher resolution results for future investigation, therefore the model independent analysis (MIA) was extended to the analysis of beam position data during the injection by Beam Diagnostics Group at SSRF. Compared to previous MIA approach, the bunch-by-bunch position data array instead of multi-turn array acquired by multiple probes, was processed by SVD method, and principal motion modes were extracted. Experiments showed that MIA is capable of separating the physical signals from the random noise and highlighting the beam motions which are really cared by the particle accelerator physicists.
In beam diagnostics of the particle accelerator, the acquired bunch-by-bunch beam position data have to be filtered by a noise-reduction process in order to get higher resolution results for future investigation, therefore the model independent analysis (MIA) was extended to the analysis of beam position data during the injection by Beam Diagnostics Group at SSRF. Compared to previous MIA approach, the bunch-by-bunch position data array instead of multi-turn array acquired by multiple probes, was processed by SVD method, and principal motion modes were extracted. Experiments showed that MIA is capable of separating the physical signals from the random noise and highlighting the beam motions which are really cared by the particle accelerator physicists.
2014,
26: 035104.
doi: 10.3788/HPLPB201426.035104
Abstract:
The coaxial beam test stand was used to calibrate the beam position monitors and the beam current monitors. The electric and magnetic field in the beam test stand with displaced inner conductor was analyzed in theory. The results show that, when the impedance of the test stand is not very small, the electromagnetic (EM) field in the test stand is significantly different to the EM field in the beam-pipe generated by the beam. The difference of the EM field can lead to non-negligible calibration errors of beam monitors such as B-dot monitors and resistive wall monitors. The influence on the B-dot beam position monitors predicted by the theory calculation agrees well with experimental results.
The coaxial beam test stand was used to calibrate the beam position monitors and the beam current monitors. The electric and magnetic field in the beam test stand with displaced inner conductor was analyzed in theory. The results show that, when the impedance of the test stand is not very small, the electromagnetic (EM) field in the test stand is significantly different to the EM field in the beam-pipe generated by the beam. The difference of the EM field can lead to non-negligible calibration errors of beam monitors such as B-dot monitors and resistive wall monitors. The influence on the B-dot beam position monitors predicted by the theory calculation agrees well with experimental results.
2014,
26: 039001.
doi: 10.3788/HPLPB201426.039001
Abstract:
Computational fluid dynamics (CFD) with proper boundary conditions was used to compare the performance of different states for capacity of entropy production control, or decrease of the pressure loss. Numerical results show that the flow field in supersonic rotor-vane is complex, phenomenon of interference between oblique shocks is obvious. The expansion shock of rotor tail induces the secondary flow and enhances the mixing of two fluids of different energy at short distance. Comparing mixing by gas-shock with shear between two fluids, the effect of turbulence is weak, even ignorable. The position and shape of the vane, such as the tail part, leading edge, the height of leading part, has an important effect on the flow regimes and efficiency of ejector. The compression-ratio and entrainment-ratio of the ejector is in proportion to rev of rotor. The rotor and vane could be free rotary with proper setting angle of vane. Furthermore, investigation on flow mechanism and efficiency of ejector is given.
Computational fluid dynamics (CFD) with proper boundary conditions was used to compare the performance of different states for capacity of entropy production control, or decrease of the pressure loss. Numerical results show that the flow field in supersonic rotor-vane is complex, phenomenon of interference between oblique shocks is obvious. The expansion shock of rotor tail induces the secondary flow and enhances the mixing of two fluids of different energy at short distance. Comparing mixing by gas-shock with shear between two fluids, the effect of turbulence is weak, even ignorable. The position and shape of the vane, such as the tail part, leading edge, the height of leading part, has an important effect on the flow regimes and efficiency of ejector. The compression-ratio and entrainment-ratio of the ejector is in proportion to rev of rotor. The rotor and vane could be free rotary with proper setting angle of vane. Furthermore, investigation on flow mechanism and efficiency of ejector is given.
2014,
26: 039002.
doi: 10.3788/HPLPB201426.039002
Abstract:
To fully demonstrate the view that polarization modulation can effectively suppress the influence of atmospheric turbulence，this paper analyzes polarization shift keying and several kinds of intensity modulation which are widely used in atmospheric laser communication systems. The comparative study of various modulation modes contains of power utilization, bandwidth requirement, transmission capacity and error performance. The results show that PolSK is more superior to any other kinds of intensity modulation mode when we consider all aspects of the performance. It has the maximum transmission capacity, the smallest bandwidth and receiving bit error rate. Thus, the polarization modulation is more suitable to be used in atmospheric laser communication.
To fully demonstrate the view that polarization modulation can effectively suppress the influence of atmospheric turbulence，this paper analyzes polarization shift keying and several kinds of intensity modulation which are widely used in atmospheric laser communication systems. The comparative study of various modulation modes contains of power utilization, bandwidth requirement, transmission capacity and error performance. The results show that PolSK is more superior to any other kinds of intensity modulation mode when we consider all aspects of the performance. It has the maximum transmission capacity, the smallest bandwidth and receiving bit error rate. Thus, the polarization modulation is more suitable to be used in atmospheric laser communication.
2014,
26: 039003.
doi: 10.3788/HPLPB201426.039003
Abstract:
An IPG YLS-6000 fiber laser and a Fronius MagicWave3000job digital welding machine are used in fiber laser-tungsten inert gas (TIG) hybrid welding. The experiment is carried out on the aluminum alloy 5083H116 with a thickness of 4 mm. The effects of characteristic of power source, arc current and distance between heat sources on weld shape of hybrid welding are studied. The welding defect, microhardness and mechanical properties of welded joints are analyzed. The results show that, weld formation is improved while using fiber laser-TIG hybrid welding, especially with variable polarity TIG arc. A good weld can be obtained when the distance between heat sources is less than 4 mm, the arc current is 150 A, and the welding mode is laser leading (LL) arc style. The weld has few pores and no cracks, and the surface is bright and uniform only with a little sag. The tensile strength of hybrid-welded joint is up to 318 MPa, about 93% of base metal, and the joint elongation is 7.6%; both are higher than those in fiber laser welding. The tensile fracture is ductile.
An IPG YLS-6000 fiber laser and a Fronius MagicWave3000job digital welding machine are used in fiber laser-tungsten inert gas (TIG) hybrid welding. The experiment is carried out on the aluminum alloy 5083H116 with a thickness of 4 mm. The effects of characteristic of power source, arc current and distance between heat sources on weld shape of hybrid welding are studied. The welding defect, microhardness and mechanical properties of welded joints are analyzed. The results show that, weld formation is improved while using fiber laser-TIG hybrid welding, especially with variable polarity TIG arc. A good weld can be obtained when the distance between heat sources is less than 4 mm, the arc current is 150 A, and the welding mode is laser leading (LL) arc style. The weld has few pores and no cracks, and the surface is bright and uniform only with a little sag. The tensile strength of hybrid-welded joint is up to 318 MPa, about 93% of base metal, and the joint elongation is 7.6%; both are higher than those in fiber laser welding. The tensile fracture is ductile.
