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RSS2014 Vol. 26, No. 02
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2014,
26: 020101.
doi: 10.3788/HPLPB201426.020101
Abstract:
We demonstrate a monolithic single-frequency Tm-doped fiber master oscillator power amplifier (MOPA) with output power of 102 W. A single-frequency fiber laser with linewidth of less than 100 kHz and central wavelength of 1.97 m was used as the seed laser of the MOPA. The main amplifiers slope efficiency was about 50%. Neither stimulated Brillouin scattering (SBS) nor other nonlinear effects were observed by monitoring the backward spectrum and power of the MOPA. The single-frequency output power could be further improved if more pump power can be launched into the MOPA.
We demonstrate a monolithic single-frequency Tm-doped fiber master oscillator power amplifier (MOPA) with output power of 102 W. A single-frequency fiber laser with linewidth of less than 100 kHz and central wavelength of 1.97 m was used as the seed laser of the MOPA. The main amplifiers slope efficiency was about 50%. Neither stimulated Brillouin scattering (SBS) nor other nonlinear effects were observed by monitoring the backward spectrum and power of the MOPA. The single-frequency output power could be further improved if more pump power can be launched into the MOPA.
2014,
26: 021001.
doi: 10.3788/HPLPB201426.021001
Abstract:
The cleaving and fusion splicing technology of the large-mode-area photonic crystal fiber was explored to achieve all-fiber structure. The amplification of the pulse with 1-10 kHz repetition rate, 10 ns duration and 0.3 nm line-width was experimentally researched. The suppression effect of the amplified spontaneous emission employing forward and backward pumping method was compared. Fundamental mode, 0.6 mJ pulse was obtained at 1 kHz which demonstrated the technical feasibility of achieving high energy and high quality pulse output from this kind of amplifier.
The cleaving and fusion splicing technology of the large-mode-area photonic crystal fiber was explored to achieve all-fiber structure. The amplification of the pulse with 1-10 kHz repetition rate, 10 ns duration and 0.3 nm line-width was experimentally researched. The suppression effect of the amplified spontaneous emission employing forward and backward pumping method was compared. Fundamental mode, 0.6 mJ pulse was obtained at 1 kHz which demonstrated the technical feasibility of achieving high energy and high quality pulse output from this kind of amplifier.
2014,
26: 021002.
doi: 10.3788/HPLPB201426.021002
Abstract:
Based on the coupled complex nonlinear Schrodinger equations, the evolvement of the multi-pulse trains is numerically investigated in erbium-doped fiber ring mode-locked laser using the nonlinear polarization rotation technique. The results show that the transmittance function of the mode-locked fiber ring laser can affect the output of multi-pulsing with the small signal gain increasing. The formation of the multiple-soliton is the result of the peak-power-clamping effects, such as the dispersive waves and pulse-splitting and the soliton energy quantization. It is the dynamic balance between the gain competition and the loss caused by the nonlinear polarization evolvement.
Based on the coupled complex nonlinear Schrodinger equations, the evolvement of the multi-pulse trains is numerically investigated in erbium-doped fiber ring mode-locked laser using the nonlinear polarization rotation technique. The results show that the transmittance function of the mode-locked fiber ring laser can affect the output of multi-pulsing with the small signal gain increasing. The formation of the multiple-soliton is the result of the peak-power-clamping effects, such as the dispersive waves and pulse-splitting and the soliton energy quantization. It is the dynamic balance between the gain competition and the loss caused by the nonlinear polarization evolvement.
2014,
26: 021003.
doi: 10.3788/HPLPB201426.021003
Abstract:
We utilize the extended Huygens-Fresnel principle to make an analysis of the scattering of a Gaussian Schell-model beam from a diffuse target in a turbulent atmosphere. It is assumed that the wave structure function is dominated by the phase structure function. Using the cross-spectral density function of the GSM beam, the analytical expressions are developed for the mutual coherence function (MCF) of the speckle field at the receiver, and then time-delayed variance of the scattering intensity in strong turbulence is derived. From the normalized MCF, estimates are given for the speckle size at receiver. We also analyze the influences of the coherence length of the source, wavelength, and turbulence strength on the mutual coherence function. For a diffuse target, the speckle size is only determined by the waist width, the coherence length of the source and the turbulence strength. With the turbulence strength increasing, the speckle radius will decrease at the receiver. In weak turbulence, speckle radius is dominated by the value of source coherence.
We utilize the extended Huygens-Fresnel principle to make an analysis of the scattering of a Gaussian Schell-model beam from a diffuse target in a turbulent atmosphere. It is assumed that the wave structure function is dominated by the phase structure function. Using the cross-spectral density function of the GSM beam, the analytical expressions are developed for the mutual coherence function (MCF) of the speckle field at the receiver, and then time-delayed variance of the scattering intensity in strong turbulence is derived. From the normalized MCF, estimates are given for the speckle size at receiver. We also analyze the influences of the coherence length of the source, wavelength, and turbulence strength on the mutual coherence function. For a diffuse target, the speckle size is only determined by the waist width, the coherence length of the source and the turbulence strength. With the turbulence strength increasing, the speckle radius will decrease at the receiver. In weak turbulence, speckle radius is dominated by the value of source coherence.
2014,
26: 021004.
doi: 10.3788/HPLPB201426.021004
Abstract:
The threshold characteristics of lasers are of great importance to the output of lasers. In this paper, we use a theoretical model, which is based on rate equations, to investigate the threshold characteristics of an end-pumped single-pass rubidium vapor laser using iteration method. The results show that, the influences of temperature and gain medium length on the threshold pump intensity are equivalent, and there exists an optimum combination of temperature and gain medium length which can minimize threshold pump intensity. The influence of pump linewidth on threshold pump intensity is linear, and the influence of central wavelength shift on pump intensity will be smaller if the pump linewidth is broader. Also there exists an optimum Rb atomic absorption linewidth, which can minimize threshold pump intensity. In order to reduce threshold pump intensity, the cell window should be anti-reflectively coated, and the output coupling-efficiency should be less than 80%.
The threshold characteristics of lasers are of great importance to the output of lasers. In this paper, we use a theoretical model, which is based on rate equations, to investigate the threshold characteristics of an end-pumped single-pass rubidium vapor laser using iteration method. The results show that, the influences of temperature and gain medium length on the threshold pump intensity are equivalent, and there exists an optimum combination of temperature and gain medium length which can minimize threshold pump intensity. The influence of pump linewidth on threshold pump intensity is linear, and the influence of central wavelength shift on pump intensity will be smaller if the pump linewidth is broader. Also there exists an optimum Rb atomic absorption linewidth, which can minimize threshold pump intensity. In order to reduce threshold pump intensity, the cell window should be anti-reflectively coated, and the output coupling-efficiency should be less than 80%.
2014,
26: 021005.
doi: 10.3788/HPLPB201426.021005
Abstract:
The reliability of high power diode-pumped solid-state laser (DPL) system was analyzed. The failure rate and mean failure-free operation time of the system were demonstrated, according to the GO graph of DPL system and GO methodology calculating formula, and the conclusion was coincident with experiential value. Furthermore, the importance of failure rates of components was analyzed, and the measures to improve the reliability of the system were also discussed, which were meaningful to the usage and maintenance of the high power DPL system. In the meantime, this method can also be applied widely to analysis of the reliability and security of industrial sectors.
The reliability of high power diode-pumped solid-state laser (DPL) system was analyzed. The failure rate and mean failure-free operation time of the system were demonstrated, according to the GO graph of DPL system and GO methodology calculating formula, and the conclusion was coincident with experiential value. Furthermore, the importance of failure rates of components was analyzed, and the measures to improve the reliability of the system were also discussed, which were meaningful to the usage and maintenance of the high power DPL system. In the meantime, this method can also be applied widely to analysis of the reliability and security of industrial sectors.
2014,
26: 021006.
doi: 10.3788/HPLPB201426.021006
Abstract:
In order to investigate the influences on ablation quality of quartz glass by the linearly and circularly polarized femtosecond lasers, the line ablation experiments of different scanning velocity and the surface ablation experiments of different line overlap rate were conducted. The influences of linearly and circularly polarized lasers on ablation line width were researched. In addition, the ablation line and surface morphology were observed using ESEM and optical microscope, respectively. Besides, the surface roughness was analyzed using the 3D surface profiler. The results show that the line width of linearly polarized laser is greater than that of circularly polarized laser, and the greater the laser power, the line width difference becomes more remarkable. Whats more, when the line overlap rate is in the range of 65%-90%, the surface roughness of linearly polarized laser increases with the increasing of overlap rate, and it reaches 1.33 m when the overlap is 65%. But the arithmetical mean deviation of line contour decreases firstly and then increases with the increasing of overlap rate, and it reaches to a minimum of 1.05 m when overlap rate is 80%. When the overlap rate is not more than 80%, the arithmetical mean deviation of line ablation surface by the linearly polarized laser is lower than that of circularly polarized laser, and when the overlap rate is 90%, it is higher than that of circularly polarized laser.
In order to investigate the influences on ablation quality of quartz glass by the linearly and circularly polarized femtosecond lasers, the line ablation experiments of different scanning velocity and the surface ablation experiments of different line overlap rate were conducted. The influences of linearly and circularly polarized lasers on ablation line width were researched. In addition, the ablation line and surface morphology were observed using ESEM and optical microscope, respectively. Besides, the surface roughness was analyzed using the 3D surface profiler. The results show that the line width of linearly polarized laser is greater than that of circularly polarized laser, and the greater the laser power, the line width difference becomes more remarkable. Whats more, when the line overlap rate is in the range of 65%-90%, the surface roughness of linearly polarized laser increases with the increasing of overlap rate, and it reaches 1.33 m when the overlap is 65%. But the arithmetical mean deviation of line contour decreases firstly and then increases with the increasing of overlap rate, and it reaches to a minimum of 1.05 m when overlap rate is 80%. When the overlap rate is not more than 80%, the arithmetical mean deviation of line ablation surface by the linearly polarized laser is lower than that of circularly polarized laser, and when the overlap rate is 90%, it is higher than that of circularly polarized laser.
2014,
26: 021007.
doi: 10.3788/HPLPB201426.021007
Abstract:
An improved finite-difference time-domain (FDTD) method with the semi-analytical recursive convolution (SARC) algorithm in digital signal processing (DSP) techniques for analysis of optical characteristics of the dispersive metals is presented. In this method, the absolute stability, high accuracy and low storage of the original SARC FDTD in dealing with general dispersive media is retained, while a concise update formula with increasing computational efficiency is presented by introducing the trapezoidal approximation. The proposed SARC FDTD approach can therefore be applied to the analysis of optical characteristics of metals provided the pole and corresponding coefficients in the metal dispersion model of interest are given. Three typical kinds of dispersive model for the metals, i.e. multi-poles Lorentz, Drude-Lorentz and Drude-CP are tested to demonstrate the feasibility of the present scheme.
An improved finite-difference time-domain (FDTD) method with the semi-analytical recursive convolution (SARC) algorithm in digital signal processing (DSP) techniques for analysis of optical characteristics of the dispersive metals is presented. In this method, the absolute stability, high accuracy and low storage of the original SARC FDTD in dealing with general dispersive media is retained, while a concise update formula with increasing computational efficiency is presented by introducing the trapezoidal approximation. The proposed SARC FDTD approach can therefore be applied to the analysis of optical characteristics of metals provided the pole and corresponding coefficients in the metal dispersion model of interest are given. Three typical kinds of dispersive model for the metals, i.e. multi-poles Lorentz, Drude-Lorentz and Drude-CP are tested to demonstrate the feasibility of the present scheme.
2014,
26: 021008.
doi: 10.3788/HPLPB201426.021008
Abstract:
The injection of laser energy will change the wave structure and effectively reduce the pressure load on the blunt body surface. A high resolution numerical method based on finite volume method and domain decomposition of structural grid is used to compute the influence of laser single pulse energy and laser continuous energy injected into type Ⅳ shock interaction at Mach number 3.45.The result shows that the pressure on the blunt body surface increases slightly when the injection laser energy with a single pulse is in a relatively short period(50 s to 60 s ),then it declines quickly, and it restores to the original state at last. The peak of the pressure on the blunt body surface increases slightly after the injection of a little laser energy with continuous deposition, and then decreases quickly with the increase of the laser energy deposition. It is remarkable that the peak of the pressure decreases slowly and tends to be a constant value even the laser energy deposition increases again.
The injection of laser energy will change the wave structure and effectively reduce the pressure load on the blunt body surface. A high resolution numerical method based on finite volume method and domain decomposition of structural grid is used to compute the influence of laser single pulse energy and laser continuous energy injected into type Ⅳ shock interaction at Mach number 3.45.The result shows that the pressure on the blunt body surface increases slightly when the injection laser energy with a single pulse is in a relatively short period(50 s to 60 s ),then it declines quickly, and it restores to the original state at last. The peak of the pressure on the blunt body surface increases slightly after the injection of a little laser energy with continuous deposition, and then decreases quickly with the increase of the laser energy deposition. It is remarkable that the peak of the pressure decreases slowly and tends to be a constant value even the laser energy deposition increases again.
2014,
26: 021009.
doi: 10.3788/HPLPB201426.021009
Abstract:
According to the certain coupling between some Zernike modes in the concentric aperture circle within the unit circle, as well as the counterbalance between each other of the corresponding Zernike modes aberration in certain concentric pupil region, the combined models of Zernike modes are created. According to the decreasing amplitude ratio parameter of aberration RMS in the concentric pupil region, the linear conjugated models of Zernike modes aberration at 4 mm concentric pupil diameter are presented. Each model shares the characteristics of 2 radial orders apart, the same azimuth frequency, the same coefficient sign and the prescribed amount. Through the analysis on the influence of conjugated models on optical quality, it is found that the optical quality is improved significantly after combination. It indicates that the influence of conjugated models combination on optical quality doesnt have superposition, but presents as compensation. Making use of the conjugated models in adaptive optics, the spatial compensation ability of the deformable mirror can be improved, which can undoubtedly inaugurate the new ideas for the correction theory of human eye aberration.
According to the certain coupling between some Zernike modes in the concentric aperture circle within the unit circle, as well as the counterbalance between each other of the corresponding Zernike modes aberration in certain concentric pupil region, the combined models of Zernike modes are created. According to the decreasing amplitude ratio parameter of aberration RMS in the concentric pupil region, the linear conjugated models of Zernike modes aberration at 4 mm concentric pupil diameter are presented. Each model shares the characteristics of 2 radial orders apart, the same azimuth frequency, the same coefficient sign and the prescribed amount. Through the analysis on the influence of conjugated models on optical quality, it is found that the optical quality is improved significantly after combination. It indicates that the influence of conjugated models combination on optical quality doesnt have superposition, but presents as compensation. Making use of the conjugated models in adaptive optics, the spatial compensation ability of the deformable mirror can be improved, which can undoubtedly inaugurate the new ideas for the correction theory of human eye aberration.
2014,
26: 021010.
doi: 10.3788/HPLPB201426.021010
Abstract:
Atmospheric optical turbulence is fractal. In this article, a high quality fiber optical turbulence sensing system is proposed to obtain time series of air refractive index fluctuations in optical turbulence under three conditions, i.e. , 0.48 meter above water, 1.8 meters and 23 meters above grassland on the Science Island in Hefei. With the time series data the Hurst exponent and fractal dimension of optical turbulence can be estimated using the method of R/S analysis. Diurnal variations and probability distributions of the two parameters are provided and analyzed. The results show that the fractal dimension under the three conditions varies with time in a day and becomes stable at noon. The dynamic range of fractal dimension is from 1.3 to 1.4, and its most probable value is about 1.35. Comparatively, the average value of fractal dimensions at the 1.8 meters above the grassland is the largest, and the value at the 23 meters above the grassland is the smallest. At last, the dependences of fractal dimension and intermittency exponent on the development of boundary layer atmospheric optical turbulence are briefly discussed.
Atmospheric optical turbulence is fractal. In this article, a high quality fiber optical turbulence sensing system is proposed to obtain time series of air refractive index fluctuations in optical turbulence under three conditions, i.e. , 0.48 meter above water, 1.8 meters and 23 meters above grassland on the Science Island in Hefei. With the time series data the Hurst exponent and fractal dimension of optical turbulence can be estimated using the method of R/S analysis. Diurnal variations and probability distributions of the two parameters are provided and analyzed. The results show that the fractal dimension under the three conditions varies with time in a day and becomes stable at noon. The dynamic range of fractal dimension is from 1.3 to 1.4, and its most probable value is about 1.35. Comparatively, the average value of fractal dimensions at the 1.8 meters above the grassland is the largest, and the value at the 23 meters above the grassland is the smallest. At last, the dependences of fractal dimension and intermittency exponent on the development of boundary layer atmospheric optical turbulence are briefly discussed.
2014,
26: 022001.
doi: 10.3788/HPLPB201426.022001
Abstract:
X-ray pinhole imaging is an important diagnostic tool in inertial confinement fusion (ICF). The point spread function (PSF) of the X-ray pinhole imaging can be used to restore the initial image and estimate the spatial resolution. This paper analyzes relations among X-ray wavelength, size of pinhole aperture, magnification and also simplified Fresnel diffraction formula. The PSF of the X-ray pinhole imaging was derived numerically using Fresnel diffraction integral. Fresnel diffraction simulated the optimal pinhole aperture, X-ray wavelength and magnification with optimal spatial resolutions and an excellent signal-to-noise ratio. The calibration of the sample was used to gain the modulation transfer function (MTF) of the whole framing camera imaging system, and Fresnel diffraction simulated the PSF of the pinhole imaging, so the PSF of the framing camera was deduced. We also obtained the PSF of the framing camera by measuring its edge function, the two results were unanimous and showed the method to stimulate X-ray pinhole imaging by using Fresnel diffraction is feasible.
X-ray pinhole imaging is an important diagnostic tool in inertial confinement fusion (ICF). The point spread function (PSF) of the X-ray pinhole imaging can be used to restore the initial image and estimate the spatial resolution. This paper analyzes relations among X-ray wavelength, size of pinhole aperture, magnification and also simplified Fresnel diffraction formula. The PSF of the X-ray pinhole imaging was derived numerically using Fresnel diffraction integral. Fresnel diffraction simulated the optimal pinhole aperture, X-ray wavelength and magnification with optimal spatial resolutions and an excellent signal-to-noise ratio. The calibration of the sample was used to gain the modulation transfer function (MTF) of the whole framing camera imaging system, and Fresnel diffraction simulated the PSF of the pinhole imaging, so the PSF of the framing camera was deduced. We also obtained the PSF of the framing camera by measuring its edge function, the two results were unanimous and showed the method to stimulate X-ray pinhole imaging by using Fresnel diffraction is feasible.
2014,
26: 022002.
doi: 10.3788/HPLPB201426.022002
Abstract:
Based on the analysis of production process of the photoelectron of the streak camera photocathode during the photoemission, the formula of photocathode energy spectral response was obtained in the region of 0.1-10 keV. The effects of photocathode parameters on spectral response were discussed. Based on the model, energy spectral response curves of Au photocathode and CsI photocathode were obtained and analyzed. And the reliability of the formula was validated by the calibrated data. The results indicate that the best thicknesses of CsI and Au photocathodes are 60 nm and 10 nm. The energy spectral response of CsI is 1 to 2 orders higher than that of Au.
Based on the analysis of production process of the photoelectron of the streak camera photocathode during the photoemission, the formula of photocathode energy spectral response was obtained in the region of 0.1-10 keV. The effects of photocathode parameters on spectral response were discussed. Based on the model, energy spectral response curves of Au photocathode and CsI photocathode were obtained and analyzed. And the reliability of the formula was validated by the calibrated data. The results indicate that the best thicknesses of CsI and Au photocathodes are 60 nm and 10 nm. The energy spectral response of CsI is 1 to 2 orders higher than that of Au.
2014,
26: 022003.
doi: 10.3788/HPLPB201426.022003
Abstract:
Direct X-ray imaging using a Fresnel zone plate (FZP) in the applications of laser plasma or inertial confinement fusion diagnostics has the potential for realizing high spatial resolution in the range of micrometers to sub-micrometers. For such an FZP imaging, the influences of the object size and the spectral bandwidth of the illuminating light have to be considered. In the simulations, numerical calculations such as the Fresnel-Kirchhhoff diffraction integral and convolutions have to be done, which will take a large amount of computer memories and cost a lot of computing time. In this paper we report improved algorithms for these numerical calculations by adopting the Monte-Carlo integration and a new algorithm of convolution. By simulating the two-dimensional imaging of an extended polychromatic X-ray source, it shows that the new algorithm has significant advantages in reducing the computing time over the past algorithms, and thus such simulations can be done by a desktop computer. The imaging indicates that with the increase of the object size and/or the spectral bandwidth, the image background is enhanced which causes the decrease of the contrast and also the image quality.
Direct X-ray imaging using a Fresnel zone plate (FZP) in the applications of laser plasma or inertial confinement fusion diagnostics has the potential for realizing high spatial resolution in the range of micrometers to sub-micrometers. For such an FZP imaging, the influences of the object size and the spectral bandwidth of the illuminating light have to be considered. In the simulations, numerical calculations such as the Fresnel-Kirchhhoff diffraction integral and convolutions have to be done, which will take a large amount of computer memories and cost a lot of computing time. In this paper we report improved algorithms for these numerical calculations by adopting the Monte-Carlo integration and a new algorithm of convolution. By simulating the two-dimensional imaging of an extended polychromatic X-ray source, it shows that the new algorithm has significant advantages in reducing the computing time over the past algorithms, and thus such simulations can be done by a desktop computer. The imaging indicates that with the increase of the object size and/or the spectral bandwidth, the image background is enhanced which causes the decrease of the contrast and also the image quality.
2014,
26: 022004.
doi: 10.3788/HPLPB201426.022004
Abstract:
In inertial confinement fusion (ICF) experiments, the surface (interface) roughness and defect of target capsule can lead to hydrodynamic instability when the target capsule is irradiated by high-intensity laser facility. Controlling and understanding the growth of hydrodynamic instability can strongly increase the feasibility of ignition experiment and is of the main importance for achieving ignition and high gain. A new cylindrical shock wave tube was designed and fabricated after consulting relevant references and the parameters of Shenguang Ⅱ laser facility. The cylindrical shock wave tube consisted of rippled polystyrene (CH) film, cylindrical carbonized-resorcinol-formaldehyde (CRF) aerogel and cylindrical CH tube. The cylindrical shock wave tube was obtained by assembling the rippled CH film and cylindrical CRF aerogel into the cylindrical CH tube. The target design and fabrication processes were described while the target parameters were measured. The results indicate that the length, diameter and density of cylindrical CRF aerogel are 1000 m, 730 m and 250 mgcm-3, respectively, the diameter and thickness of the rippled CH film are 15 m and 730 m, while the perturbation period and amplitude on its surface are 100 m and 4.3 m, the maximum axial assembly deviation of the cylindrical shock wave tube is 2 m, while its maximum diameter assembly deviation is 3 m.
In inertial confinement fusion (ICF) experiments, the surface (interface) roughness and defect of target capsule can lead to hydrodynamic instability when the target capsule is irradiated by high-intensity laser facility. Controlling and understanding the growth of hydrodynamic instability can strongly increase the feasibility of ignition experiment and is of the main importance for achieving ignition and high gain. A new cylindrical shock wave tube was designed and fabricated after consulting relevant references and the parameters of Shenguang Ⅱ laser facility. The cylindrical shock wave tube consisted of rippled polystyrene (CH) film, cylindrical carbonized-resorcinol-formaldehyde (CRF) aerogel and cylindrical CH tube. The cylindrical shock wave tube was obtained by assembling the rippled CH film and cylindrical CRF aerogel into the cylindrical CH tube. The target design and fabrication processes were described while the target parameters were measured. The results indicate that the length, diameter and density of cylindrical CRF aerogel are 1000 m, 730 m and 250 mgcm-3, respectively, the diameter and thickness of the rippled CH film are 15 m and 730 m, while the perturbation period and amplitude on its surface are 100 m and 4.3 m, the maximum axial assembly deviation of the cylindrical shock wave tube is 2 m, while its maximum diameter assembly deviation is 3 m.
2014,
26: 022005.
doi: 10.3788/HPLPB201426.022005
Abstract:
Aligned carbon nanotube arrays (ACNTs) were prepared by chemical vapor deposition (CVD). The graphitization degree of ACNTs was systematically investigated. The morphology and structure of the products were characterized by scanning electron microscopy (SEM) and Raman spectroscopy. The mechanism how the different experiment conditions affect the graphitization degree of ACNTs was discussed. The results indicated that the graphitization degree of ACNTs would be bad when the concentration of catalyst was too low within a certain range of catalyst concentration. And only if the flowing rate of reactant is appropriate, the graphitization degree of ACNTs will be nice. Moreover, in order to obtain a good graphitization degree of ACNTs, the growth temperature is need to control accurately.
Aligned carbon nanotube arrays (ACNTs) were prepared by chemical vapor deposition (CVD). The graphitization degree of ACNTs was systematically investigated. The morphology and structure of the products were characterized by scanning electron microscopy (SEM) and Raman spectroscopy. The mechanism how the different experiment conditions affect the graphitization degree of ACNTs was discussed. The results indicated that the graphitization degree of ACNTs would be bad when the concentration of catalyst was too low within a certain range of catalyst concentration. And only if the flowing rate of reactant is appropriate, the graphitization degree of ACNTs will be nice. Moreover, in order to obtain a good graphitization degree of ACNTs, the growth temperature is need to control accurately.
2014,
26: 022006.
doi: 10.3788/HPLPB201426.022006
Abstract:
The time dependence of irradiation drive symmetry and intensity on the capsule in different shaped hohlraums and laser arrangement is investigated by a 3D view-factor code called IRAD3D. The simulation results show that the loss of energy by the wall of hohlraum is reduced for a much smaller hohlraum area in the ellipsoidal-shaped hohlraum, resulting in an increase in the fraction of energy absorbed by the capsule. The time-integrated Legendre mode P2 of asymmetry can be controlled in a low level in a validated length of hohlraum. The hohlraum can be shorter in ellipsoidal-hohlraum with two-cones irradiation. A smaller Legendre mode P4 is attained in a four-cones irradiation system but a worse mode M4 of azimuthal asymmetry appears. All of the asymmetry modes are in a good level in the ellipsoidal-hohlraum with two-cones irradiation, meanwhile there is a 25%-27% increase in the irradiation drive flux onto the capsule compared with the cylindrical hohlraums.
The time dependence of irradiation drive symmetry and intensity on the capsule in different shaped hohlraums and laser arrangement is investigated by a 3D view-factor code called IRAD3D. The simulation results show that the loss of energy by the wall of hohlraum is reduced for a much smaller hohlraum area in the ellipsoidal-shaped hohlraum, resulting in an increase in the fraction of energy absorbed by the capsule. The time-integrated Legendre mode P2 of asymmetry can be controlled in a low level in a validated length of hohlraum. The hohlraum can be shorter in ellipsoidal-hohlraum with two-cones irradiation. A smaller Legendre mode P4 is attained in a four-cones irradiation system but a worse mode M4 of azimuthal asymmetry appears. All of the asymmetry modes are in a good level in the ellipsoidal-hohlraum with two-cones irradiation, meanwhile there is a 25%-27% increase in the irradiation drive flux onto the capsule compared with the cylindrical hohlraums.
2014,
26: 022007.
doi: 10.3788/HPLPB201426.022007
Abstract:
In order to provide spot positioning detection method of adhesive glue for precision assembly of pneumatic pellet, this paper studies the compatibility and fluorescence of epoxy adhesive with coumarin and fluorescent dye. The adding process is introduced, the impacts of coumarin concentration as well as the curing agent on the fluorescence intensity are studied, and anhydrous ethanol is used to reduce the surface tension. The results show that the incident wavelength of coumarin and fluorescent dye is 274 nm and 435 nm, the excitation wavelength is 519 nm and 365 nm, respectively. Coumarin can be dissolved in the curing agent 176 well and blue fluorescence light is observed. The fluorescent dye is uniformly dispersed in the adhesive system, which can be used for detecting and locating.
In order to provide spot positioning detection method of adhesive glue for precision assembly of pneumatic pellet, this paper studies the compatibility and fluorescence of epoxy adhesive with coumarin and fluorescent dye. The adding process is introduced, the impacts of coumarin concentration as well as the curing agent on the fluorescence intensity are studied, and anhydrous ethanol is used to reduce the surface tension. The results show that the incident wavelength of coumarin and fluorescent dye is 274 nm and 435 nm, the excitation wavelength is 519 nm and 365 nm, respectively. Coumarin can be dissolved in the curing agent 176 well and blue fluorescence light is observed. The fluorescent dye is uniformly dispersed in the adhesive system, which can be used for detecting and locating.
2014,
26: 022008.
doi: 10.3788/HPLPB201426.022008
Abstract:
The preparation process of ultrafine ultra-thin Ni80Cr20 alloy wire was studied by cold drawing. The property of NiCr alloy wire was characterized by SEM, XRD and tensile tester. The results show that the optimal electrolyte concentration and time were 0.05 mol/L and 3 s in the process of electrolytic corrosion, respectively. NiCr alloy wire with a smooth surface, precise dimensions and the diameter range of 24.54 m was obtained. After drawing, the grain size decreased, and the grain size grew up after annealing. Due to work harding appearing in the drawing process, the elongation decreased from 16% to 1.88%. The fracture strength decreases and the elongation and plasticity increases after annealing. The fracture strength of wire annealed in N2 is greater than in vacuum. On the contrary, the elongation of wire annealed in N2 is less than in vacuum.
The preparation process of ultrafine ultra-thin Ni80Cr20 alloy wire was studied by cold drawing. The property of NiCr alloy wire was characterized by SEM, XRD and tensile tester. The results show that the optimal electrolyte concentration and time were 0.05 mol/L and 3 s in the process of electrolytic corrosion, respectively. NiCr alloy wire with a smooth surface, precise dimensions and the diameter range of 24.54 m was obtained. After drawing, the grain size decreased, and the grain size grew up after annealing. Due to work harding appearing in the drawing process, the elongation decreased from 16% to 1.88%. The fracture strength decreases and the elongation and plasticity increases after annealing. The fracture strength of wire annealed in N2 is greater than in vacuum. On the contrary, the elongation of wire annealed in N2 is less than in vacuum.
2014,
26: 022009.
doi: 10.3788/HPLPB201426.022009
Abstract:
The fabrication of metal film steps used in equation of state experiment targets was investigated. The metal film step of hundreds of microns width was cut by picosecond laser processing technology. The factors of generating heat effect in the processing were analyzed. The processing parameters were as follows: power 0.5 W, pulse width 10 ps, wavelength 355 nm, and scanning speed 100 mm/s. Two metal films of 400 and 120 microns width were obtained in the experiment. The measurement results show that the width of metal film can be precisely controlled and the quality of metal film surface before and after cutting was the same.
The fabrication of metal film steps used in equation of state experiment targets was investigated. The metal film step of hundreds of microns width was cut by picosecond laser processing technology. The factors of generating heat effect in the processing were analyzed. The processing parameters were as follows: power 0.5 W, pulse width 10 ps, wavelength 355 nm, and scanning speed 100 mm/s. Two metal films of 400 and 120 microns width were obtained in the experiment. The measurement results show that the width of metal film can be precisely controlled and the quality of metal film surface before and after cutting was the same.
2014,
26: 022010.
doi: 10.3788/HPLPB201426.022010
Abstract:
In order to realize adaptive compensation for positioning error of precision measurement platform, a new method has been proposed based on monitoring measurement environment and support vector regression for ensuring the high-precision of measurement platform used for optical element in different measurement environment. Firstly, a prediction model was established with the theory of support vector regression (SVR), using several group data of temperature, humidity, atmospheric pressure in different environment for predicting the maximum positioning error value. Then SVR was used iteratively to predict the positioning error value of any position, using both maximum positioning error value and environmental factors. Finally, the positioning error was input to the controller for compensation. Instruments including Renishaw laser interferometer along with temperature and humidity sensors were applied to experiments with the precision measurement platform. Experimental results indicate that, comparing the prediction data with the measured data, the average of the absolute difference is 0.88 m, and the Pearsons square of correlation coefficient is 0.99. After adaptive compensation, the average of positioning error decreases to 1.4 m from 43 m. It concludes that this method is feasible and accurate.
In order to realize adaptive compensation for positioning error of precision measurement platform, a new method has been proposed based on monitoring measurement environment and support vector regression for ensuring the high-precision of measurement platform used for optical element in different measurement environment. Firstly, a prediction model was established with the theory of support vector regression (SVR), using several group data of temperature, humidity, atmospheric pressure in different environment for predicting the maximum positioning error value. Then SVR was used iteratively to predict the positioning error value of any position, using both maximum positioning error value and environmental factors. Finally, the positioning error was input to the controller for compensation. Instruments including Renishaw laser interferometer along with temperature and humidity sensors were applied to experiments with the precision measurement platform. Experimental results indicate that, comparing the prediction data with the measured data, the average of the absolute difference is 0.88 m, and the Pearsons square of correlation coefficient is 0.99. After adaptive compensation, the average of positioning error decreases to 1.4 m from 43 m. It concludes that this method is feasible and accurate.
2014,
26: 022011.
doi: 10.3788/HPLPB201426.022011
Abstract:
The fundamental harmonic of a pulsed Nd:YAG laser (1064 nm) was used for the ablation of copper and brass samples in air at atmospheric pressure and the laser-induced plasma characteristics were examined comparatively. The electron densities Ne of 3.61017 cm-3 in copper plasma and 3.31017 cm-3 in brass plasma were inferred from the Stark broadened profile of Cu I 324.75 nm averaged with 15 single spectra. In order to minimize relative errors in calculation of the electron temperature Te, an improved iterative Boltzmann plot method was used. Experimental results showed that the electron temperature in copper plasma was 6316 K larger than the value (6051 K) in brass plasma because the ionization potential of Zn (9.39 eV) is higher than that of Cu (7.72 eV). The plasma was verified to be in local thermodynamic equilibrium (LTE) and optical thin state based on the experimental results.
The fundamental harmonic of a pulsed Nd:YAG laser (1064 nm) was used for the ablation of copper and brass samples in air at atmospheric pressure and the laser-induced plasma characteristics were examined comparatively. The electron densities Ne of 3.61017 cm-3 in copper plasma and 3.31017 cm-3 in brass plasma were inferred from the Stark broadened profile of Cu I 324.75 nm averaged with 15 single spectra. In order to minimize relative errors in calculation of the electron temperature Te, an improved iterative Boltzmann plot method was used. Experimental results showed that the electron temperature in copper plasma was 6316 K larger than the value (6051 K) in brass plasma because the ionization potential of Zn (9.39 eV) is higher than that of Cu (7.72 eV). The plasma was verified to be in local thermodynamic equilibrium (LTE) and optical thin state based on the experimental results.
2014,
26: 022012.
doi: 10.3788/HPLPB201426.022012
Abstract:
We adopted the anion surface active agents SDS, SDBS and mixed surface active agent polyoxyethylene alkyl vinyl double ammonium (PAVDA) to treat polystyrene (PS) monolayer microspheres and improve the distribution of ozonized PS-PVA double emulsion in the oil. The influences of various surface active agents on the contact angle and different absorption rates of PVA on PS film were tested and analyzed. Moreover, the effects of electrostatic repulsion and special resistance on the distribution of monolayer microspheres were also studied. Experimental results show that all of above-mentioned surface active agents can improve the distribution of PS monolayer microspheres to some extent. As for double emulsion treated by SDS and SDBS, because of the flocculation which happened in the oil phase during curing, it was difficult to form large-size microspheres. Specially, we gained about a half surviving rate of PS-PVA double-layer hollow microspheres (700-900 m in diameter), when treating them with PAVDA solution. The results also indicate that space hindrance is more effective than electrostatic repulsion to modify the distribution of PS microspheres.
We adopted the anion surface active agents SDS, SDBS and mixed surface active agent polyoxyethylene alkyl vinyl double ammonium (PAVDA) to treat polystyrene (PS) monolayer microspheres and improve the distribution of ozonized PS-PVA double emulsion in the oil. The influences of various surface active agents on the contact angle and different absorption rates of PVA on PS film were tested and analyzed. Moreover, the effects of electrostatic repulsion and special resistance on the distribution of monolayer microspheres were also studied. Experimental results show that all of above-mentioned surface active agents can improve the distribution of PS monolayer microspheres to some extent. As for double emulsion treated by SDS and SDBS, because of the flocculation which happened in the oil phase during curing, it was difficult to form large-size microspheres. Specially, we gained about a half surviving rate of PS-PVA double-layer hollow microspheres (700-900 m in diameter), when treating them with PAVDA solution. The results also indicate that space hindrance is more effective than electrostatic repulsion to modify the distribution of PS microspheres.
2014,
26: 022013.
doi: 10.3788/HPLPB201426.022013
Abstract:
Cu-doped MF aerogels were successfully synthesized by -ray irradiation induced reduction method with different total irradiation doses, which has been confirmed by XRD, ICP-AES and SEM-EDS. The SEM graphs indicate that the reduction of Cu particles in the MF aerogels is small, and they do not reunite in 100 kGy and 200 kGy total irradiation doses. While in higher total irradiation dose (larger than 200 kGy), the reduced Cu will form the metal reunion area in the MF aerogels. The nitrogen adsorption data analysis shows that the specific surface area and the absorption capacity of MF aerogels decrease after Cu doping, which means that Cu particles fill part of the mesopore and micropore of MF aerogels. The content of Cu in the MF aerogels after irradiation is increasing with a increasing total irradiation dose. Besides, at the same irradiation dose rate, different total irradiation doses will affect the contents and morphology of Cu in MF aerogels.
Cu-doped MF aerogels were successfully synthesized by -ray irradiation induced reduction method with different total irradiation doses, which has been confirmed by XRD, ICP-AES and SEM-EDS. The SEM graphs indicate that the reduction of Cu particles in the MF aerogels is small, and they do not reunite in 100 kGy and 200 kGy total irradiation doses. While in higher total irradiation dose (larger than 200 kGy), the reduced Cu will form the metal reunion area in the MF aerogels. The nitrogen adsorption data analysis shows that the specific surface area and the absorption capacity of MF aerogels decrease after Cu doping, which means that Cu particles fill part of the mesopore and micropore of MF aerogels. The content of Cu in the MF aerogels after irradiation is increasing with a increasing total irradiation dose. Besides, at the same irradiation dose rate, different total irradiation doses will affect the contents and morphology of Cu in MF aerogels.
2014,
26: 022014.
Abstract:
The Raman vibration modes of potassium dihydrogen phosphate (KDP) crystal were analyzed by the group theory in detail, and the Raman vibration modes were well assigned. The Raman spectra of type Z annealed KDP crystal in X(ZZ)X, Z(XY)X and Y(XY)X scattering geometries and type Z unannealed KDP crystal in Z(XY)Z scattering geometry were also measured by Raman spectrophotometer system. According to the selection rules we found that the Raman peaks in X(ZZ)X, Z(XY)X and Y(XY)X scattering geometries correspond to A1, B2(LO) and B2(TO) modes respectively. However, in the Z(XY)Z scattering geometry, A1 modes appear besides B2 modes, and in Y(XY)X scattering geometry there exist B2 modes only. What is more, the Raman spectra of annealed and unannealed KDP crystal in Z(XY)Z scattering geometry show no obvious difference. The results indicate that the symmetry of KDP crystal is lower and A1 modes possess angular dependence in Raman back-scattering geometry, which is determined by crystal structure and independent of lattice internal stress.
The Raman vibration modes of potassium dihydrogen phosphate (KDP) crystal were analyzed by the group theory in detail, and the Raman vibration modes were well assigned. The Raman spectra of type Z annealed KDP crystal in X(ZZ)X, Z(XY)X and Y(XY)X scattering geometries and type Z unannealed KDP crystal in Z(XY)Z scattering geometry were also measured by Raman spectrophotometer system. According to the selection rules we found that the Raman peaks in X(ZZ)X, Z(XY)X and Y(XY)X scattering geometries correspond to A1, B2(LO) and B2(TO) modes respectively. However, in the Z(XY)Z scattering geometry, A1 modes appear besides B2 modes, and in Y(XY)X scattering geometry there exist B2 modes only. What is more, the Raman spectra of annealed and unannealed KDP crystal in Z(XY)Z scattering geometry show no obvious difference. The results indicate that the symmetry of KDP crystal is lower and A1 modes possess angular dependence in Raman back-scattering geometry, which is determined by crystal structure and independent of lattice internal stress.
2014,
26: 022015.
doi: 10.3788/HPLPB201426.022015
Abstract:
Turning procedure is one of the key production procedures in golden hohlraum. There are four key parameters of golden hohlraum including the diameter, the length, the rear and front laser entrances in the turning procedure whose stability and production quality determine the final quality of the golden hohlraum. It is necessary to strictly control the process of the turning procedure. In this paper, A Bayesian method for constructing production quality control model was discussed at the condition of small batch and sample. A production quality control model for turning procedure was established with large batch of history production data and small batch of current production data. The model was validated by one batch of production data. The results showed that the turning procedure was a stability production process. There was no quality alarm generated from the quality control model. It is believed that the quality control model is correct and able to supervise the actual golden hohlraum fabricating process.
Turning procedure is one of the key production procedures in golden hohlraum. There are four key parameters of golden hohlraum including the diameter, the length, the rear and front laser entrances in the turning procedure whose stability and production quality determine the final quality of the golden hohlraum. It is necessary to strictly control the process of the turning procedure. In this paper, A Bayesian method for constructing production quality control model was discussed at the condition of small batch and sample. A production quality control model for turning procedure was established with large batch of history production data and small batch of current production data. The model was validated by one batch of production data. The results showed that the turning procedure was a stability production process. There was no quality alarm generated from the quality control model. It is believed that the quality control model is correct and able to supervise the actual golden hohlraum fabricating process.
2014,
26: 022016.
doi: 10.3788/HPLPB201426.022016
Abstract:
The physical structure of N-doped carbon aerogel(N-CA) is modified with CO2 technology. The effect of activation temperature on the porous texture and the electrochemical performance of activated N-doped carbon aerogel(N-ACA) as electrode material of supercapacitors are investigated. The porous structure and elemental composition of the N-doped aerogels are tested by nitrogen adsorption at 77 K, X-ray photoelectron spectroscopy (XPS) and elemental analysis. With further increasing of the activation time,the surface area of N-ACA increases, and the concentration of nitrogen decreases continually but not the pyrrolic. The electrochemical performance of N-doped carbon aerogels is confirmed using cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). The results showed that the appropriate porous texture and the concentration of pyrrolic have crucial effect on the electrochemical performance of the electric double-layer capacitors. The specific capacitance of the 950-N-ACA electrode obtained from cyclic voltammetry measurement in 6 molL-1 KOH aqueous solution at a scan rate of 5 mVs-1 is up to 267.4 Fg-1 and loses about 1.5% after 1000 charge-discharge cycles.
The physical structure of N-doped carbon aerogel(N-CA) is modified with CO2 technology. The effect of activation temperature on the porous texture and the electrochemical performance of activated N-doped carbon aerogel(N-ACA) as electrode material of supercapacitors are investigated. The porous structure and elemental composition of the N-doped aerogels are tested by nitrogen adsorption at 77 K, X-ray photoelectron spectroscopy (XPS) and elemental analysis. With further increasing of the activation time,the surface area of N-ACA increases, and the concentration of nitrogen decreases continually but not the pyrrolic. The electrochemical performance of N-doped carbon aerogels is confirmed using cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). The results showed that the appropriate porous texture and the concentration of pyrrolic have crucial effect on the electrochemical performance of the electric double-layer capacitors. The specific capacitance of the 950-N-ACA electrode obtained from cyclic voltammetry measurement in 6 molL-1 KOH aqueous solution at a scan rate of 5 mVs-1 is up to 267.4 Fg-1 and loses about 1.5% after 1000 charge-discharge cycles.
2014,
26: 022017.
doi: 10.3788/HPLPB201426.022017
Abstract:
To characterize the sphericity and the wall thickness uniformity, thick-walled polystyrene (PS) hollow microspheres with inner diameter of 850 m and wall thickness of 25 m were measured by the VMR microscope system, and the effects of sampling methods on the sphericity and the wall thickness uniformity were investigated. For the characterization of a batch of hollow microspheres, the experimental results showed very slight difference when the sample number was no less than 30. For a single hollow microsphere, the average results became stable when the times of the projection torus were at least 3. Therefore, the sample number should be no less than 30 to characterize a batch of hollow microspheres. Moreover, for hollow microspheres with poor wall thickness uniformity or poor sphericity, taking advantage of more than one projection torus benefits improving the reliability of the results.
To characterize the sphericity and the wall thickness uniformity, thick-walled polystyrene (PS) hollow microspheres with inner diameter of 850 m and wall thickness of 25 m were measured by the VMR microscope system, and the effects of sampling methods on the sphericity and the wall thickness uniformity were investigated. For the characterization of a batch of hollow microspheres, the experimental results showed very slight difference when the sample number was no less than 30. For a single hollow microsphere, the average results became stable when the times of the projection torus were at least 3. Therefore, the sample number should be no less than 30 to characterize a batch of hollow microspheres. Moreover, for hollow microspheres with poor wall thickness uniformity or poor sphericity, taking advantage of more than one projection torus benefits improving the reliability of the results.
2014,
26: 022018.
doi: 10.3788/HPLPB201426.022018
Abstract:
According to the assembly accuracy of NIF REV4.0 for fusion ignition targets, the assembly process and precision robotic system for hohlraum assembly were analyzed. The tolerance range of the hohlraum inserted into the TMP (thermal mechanical package) was determined. The precision robotic system was designed. There were 12 motorized stages, one laser sensor and one 6-axis force/torque sensor in the system. The repeatabilities of the motorized stages were 0.3 m and 0.01. The level attitude and the force status of the targets could be detected by the laser sensor and the 6-axis force/torque sensor. Hohlraum and LEH insert were assembled by the system. The axis distance and angle of hohlraum and TMP were less than 8 m and 0.5. The experiment results of the hohlraum assembly by the system verified the feasibility of the assembly process and the system functions.
According to the assembly accuracy of NIF REV4.0 for fusion ignition targets, the assembly process and precision robotic system for hohlraum assembly were analyzed. The tolerance range of the hohlraum inserted into the TMP (thermal mechanical package) was determined. The precision robotic system was designed. There were 12 motorized stages, one laser sensor and one 6-axis force/torque sensor in the system. The repeatabilities of the motorized stages were 0.3 m and 0.01. The level attitude and the force status of the targets could be detected by the laser sensor and the 6-axis force/torque sensor. Hohlraum and LEH insert were assembled by the system. The axis distance and angle of hohlraum and TMP were less than 8 m and 0.5. The experiment results of the hohlraum assembly by the system verified the feasibility of the assembly process and the system functions.
2014,
26: 022019.
doi: 10.3788/HPLPB201426.022019
Abstract:
Ta2O5/SiO2 gradient-index optical thin films for 1064 nm have been prepared with Ta2O5 and SiO2 by ion beam sputtering (IBS). The optical property and laser-induced damage threshold (LIDT) of the coatings were investigated, respectively. Sidelobe ripples beside the stopband are suppressed by the gradient-index design, meanwhile the design achieves above 99.8% reflectivity at 1064 nm. The multi-shot LIDT decreases as the number of shots increases, but after 20 pulses, it remains almost unchanged all the way to 100 pulses. Typical damage micrographs demonstrate a significant dependence of the initiated damage on the diameter of nodular defect. Scanning electron microscope (SEM) and focused ion beam microscope (FIB) pictures of the nodular defects show that, ablation pits caused by the initiated nodular defect expanded to farther nodular defects under multi-shot pulses. Damage accumulation effects may be attributed to the ejection of farther nodular defects.
Ta2O5/SiO2 gradient-index optical thin films for 1064 nm have been prepared with Ta2O5 and SiO2 by ion beam sputtering (IBS). The optical property and laser-induced damage threshold (LIDT) of the coatings were investigated, respectively. Sidelobe ripples beside the stopband are suppressed by the gradient-index design, meanwhile the design achieves above 99.8% reflectivity at 1064 nm. The multi-shot LIDT decreases as the number of shots increases, but after 20 pulses, it remains almost unchanged all the way to 100 pulses. Typical damage micrographs demonstrate a significant dependence of the initiated damage on the diameter of nodular defect. Scanning electron microscope (SEM) and focused ion beam microscope (FIB) pictures of the nodular defects show that, ablation pits caused by the initiated nodular defect expanded to farther nodular defects under multi-shot pulses. Damage accumulation effects may be attributed to the ejection of farther nodular defects.
2014,
26: 022020.
doi: 10.3788/HPLPB201426.022020
Abstract:
SiO2 colloids were dispersed in hot poly-4-methyl-1-pentene (PMP) solution, and then the solution was coated on glass microscope slices by convective assembly method. PMP foam films compounded with SiO2 colloids template were formed through thermally induced phase separation (TIPS) and then they were eroded by hydrofluoric acid (HF) solution to obtain regular porous PMP foam films. The microstructures of PMP foam films compounded with SiO2 colloids template and regular porous PMP foam films were analyzed by scanning electron microscopy (SEM). The results show that SiO2 colloids were arranged uniformly and regularly, and the PMP foam films eroded by HF solution had formed uniform and regular porous microstructure which replicated the microstructure of SiO2 colloids.
SiO2 colloids were dispersed in hot poly-4-methyl-1-pentene (PMP) solution, and then the solution was coated on glass microscope slices by convective assembly method. PMP foam films compounded with SiO2 colloids template were formed through thermally induced phase separation (TIPS) and then they were eroded by hydrofluoric acid (HF) solution to obtain regular porous PMP foam films. The microstructures of PMP foam films compounded with SiO2 colloids template and regular porous PMP foam films were analyzed by scanning electron microscopy (SEM). The results show that SiO2 colloids were arranged uniformly and regularly, and the PMP foam films eroded by HF solution had formed uniform and regular porous microstructure which replicated the microstructure of SiO2 colloids.
2014,
26: 023001.
doi: 10.3788/HPLPB201426.023001
Abstract:
An ultrawide band paraboloidal reflector antenna for ultra-high repetition pulse has been developed. For improving radiant efficiency, the antenna adopted a new coplanar TEM feed structure, and the impedance and radiation characteristics were analyzed. Results show that the rEpmax value is about 18.3 kV and rEpp value is about 35.7 kV when the antenna is excited by a pulse of 180 ps risetime and 3 kV peak voltage. Compared with those antennas with TEM horns, this kind of antenna has the best radiating property.
An ultrawide band paraboloidal reflector antenna for ultra-high repetition pulse has been developed. For improving radiant efficiency, the antenna adopted a new coplanar TEM feed structure, and the impedance and radiation characteristics were analyzed. Results show that the rEpmax value is about 18.3 kV and rEpp value is about 35.7 kV when the antenna is excited by a pulse of 180 ps risetime and 3 kV peak voltage. Compared with those antennas with TEM horns, this kind of antenna has the best radiating property.
2014,
26: 023002.
doi: 10.3788/HPLPB201426.023002
Abstract:
Through analysing the coupling coefficient of the generalised telegraphists equations, an optimized 94 GHz gyrotron with gradually tapered cavity is designed. An output power of about 120 kW,corresponding to 41% efficiency, and an oscillation frequency of 94.099 GHz are achieved with a 50 kV, 6 A helical electron beam with a pitch angle of 1.4 at a guiding magnetic field of 3.548 5 T. Compared with the line-joint cavity, the purity of the operating mode is enhanced above 27 dB and the efficiency increases about 7% in the gyrotron with gradually tapered cavity. The efficiency of the beam-wave interaction calculated by the code based on the self-consistent nonlinear theory is in well accord with that simulated by PIC.
Through analysing the coupling coefficient of the generalised telegraphists equations, an optimized 94 GHz gyrotron with gradually tapered cavity is designed. An output power of about 120 kW,corresponding to 41% efficiency, and an oscillation frequency of 94.099 GHz are achieved with a 50 kV, 6 A helical electron beam with a pitch angle of 1.4 at a guiding magnetic field of 3.548 5 T. Compared with the line-joint cavity, the purity of the operating mode is enhanced above 27 dB and the efficiency increases about 7% in the gyrotron with gradually tapered cavity. The efficiency of the beam-wave interaction calculated by the code based on the self-consistent nonlinear theory is in well accord with that simulated by PIC.
2014,
26: 023003.
doi: 10.3788/HPLPB201426.023003
Abstract:
A circular TE11-HE11 mode converter with slots in its inner wall is designed for a 30.5 GHz klystron using the mode matching method. Calculations show the mode converter has a conversion of higher than 98.8% inside a 2.6% bandwidth. Experiments indicate it works well. The mode matching method has advantages of minimum memory consumption, high accuracy and rapid analysis speed over the other methods.
A circular TE11-HE11 mode converter with slots in its inner wall is designed for a 30.5 GHz klystron using the mode matching method. Calculations show the mode converter has a conversion of higher than 98.8% inside a 2.6% bandwidth. Experiments indicate it works well. The mode matching method has advantages of minimum memory consumption, high accuracy and rapid analysis speed over the other methods.
2014,
26: 023004.
doi: 10.3788/HPLPB201426.023004
Abstract:
Emission spectrum measurement and simulation are conducted to derive the vibration, rotation and electronic excitation temperature of nitrogen plasmas generated in microwave discharge with different pulse width and pressure. At the pressure of 266~400 Pa, the vibration temperature of plasmas is (2700100) K, electronic excitation temperature is (0.320.015) eV. Rotation temperature rises with the rising of pulse width, the maximum rotation temperature measured in this experiment is 370 K. Vibration temperature and electronic excitation temperature trend to decrease at the same time at the pressure away from 266～400 Pa, but rotation temperature trends to increase. This means electronic excitation temperature and vibration temperature have a strong relationship.
Emission spectrum measurement and simulation are conducted to derive the vibration, rotation and electronic excitation temperature of nitrogen plasmas generated in microwave discharge with different pulse width and pressure. At the pressure of 266~400 Pa, the vibration temperature of plasmas is (2700100) K, electronic excitation temperature is (0.320.015) eV. Rotation temperature rises with the rising of pulse width, the maximum rotation temperature measured in this experiment is 370 K. Vibration temperature and electronic excitation temperature trend to decrease at the same time at the pressure away from 266～400 Pa, but rotation temperature trends to increase. This means electronic excitation temperature and vibration temperature have a strong relationship.
2014,
26: 023005.
doi: 10.3788/HPLPB201426.023005
Abstract:
This paper introduced the particular advantages of electrostatic focusing style in millimeter traveling wave tube and analyzed the methods to establish periodic electrostatic field. Based on a Ka band traveling wave tube, first we designed an intense current density electron gun and selected a comb-like shape as slow wave circuit. Then a numerical simulation on the electron optical system made up of an electron gun and a slow wave circuit was carried out. Finally we summarized tolerance for key sizes of the slow wave circuit. The results showed that one hundred-percent beam passed slow wave structure smoothly. The good static beam pass was a foundation stone for subsequent sufficient beam-wave interaction and it was proven that a large current density beam in millimeter traveling wave tube could be focused commendably by electrostatic field. Simultaneously, the summary for the tolerance could provide a reference for the design of the electron optical system of millimeter electrostatically focused traveling wave tube.
This paper introduced the particular advantages of electrostatic focusing style in millimeter traveling wave tube and analyzed the methods to establish periodic electrostatic field. Based on a Ka band traveling wave tube, first we designed an intense current density electron gun and selected a comb-like shape as slow wave circuit. Then a numerical simulation on the electron optical system made up of an electron gun and a slow wave circuit was carried out. Finally we summarized tolerance for key sizes of the slow wave circuit. The results showed that one hundred-percent beam passed slow wave structure smoothly. The good static beam pass was a foundation stone for subsequent sufficient beam-wave interaction and it was proven that a large current density beam in millimeter traveling wave tube could be focused commendably by electrostatic field. Simultaneously, the summary for the tolerance could provide a reference for the design of the electron optical system of millimeter electrostatically focused traveling wave tube.
2014,
26: 023006.
doi: 10.3788/HPLPB201426.023006
Abstract:
An X-band high power relativistic klystron amplifier is studied using a 2.5 dimensional PIC code MAGIC in this paper. The presented klystron is composed of five nose-cone removed pillbox cavities, including an input cavity, three middle cavities, and an output cavity. The absorption of the injected microwave is studied, and the gaps of idler cavities are optimized according to the fundamental harmonic modulated current when an electron beam propagates through every cavity. Finally, after optimization of the guiding magnetic field, the output microwave is obtained with an average power of 105 MW when the diode voltage is 520 kV, beam current 460 A, the guiding magnetic field 0.4 T and the seeding power 1 kW. The efficiency reaches 43.5% with a gain of 50 dB, when the fundamental current modulation depth reaches 162%.
An X-band high power relativistic klystron amplifier is studied using a 2.5 dimensional PIC code MAGIC in this paper. The presented klystron is composed of five nose-cone removed pillbox cavities, including an input cavity, three middle cavities, and an output cavity. The absorption of the injected microwave is studied, and the gaps of idler cavities are optimized according to the fundamental harmonic modulated current when an electron beam propagates through every cavity. Finally, after optimization of the guiding magnetic field, the output microwave is obtained with an average power of 105 MW when the diode voltage is 520 kV, beam current 460 A, the guiding magnetic field 0.4 T and the seeding power 1 kW. The efficiency reaches 43.5% with a gain of 50 dB, when the fundamental current modulation depth reaches 162%.
2014,
26: 023007.
doi: 10.3788/HPLPB201426.023007
Abstract:
Considering the demand for dual-polarized wideband antenna in communication systems and radar systems, a wideband dual polarized bowtie antenna excited by non-coplanar strip line is proposed in this paper. Dual polarization is realized by two sets of orthogonal bowtie dipoles. The orthogonal bowtie dipoles are fed by a novel balun (a transition from microstrip line into strip line). The tapered microstrip line fed by a coaxial connector is converted into a non-coplanar strip line. Then, the non-coplanar strip line providing symmetrical electric field distribution is a balanced structure which satisfies the balanced feed requirements of bowtie dipoles. Experimental investigations indicate that the impedance bandwidth of 69.23% is available, and the voltage standing wave ratio (VSWR) is below 2 over the frequency range from 8 GHz to 12 GHz. In order to improve the antenna radiation and gain, the dual-polarized antenna is placed in a back cavity. The measure results show that the VSWR is approximately below 3 from 6.8 GHz to 18 GHz, the antenna gain is higher than 0.11 dB from 8 GHz to 12 GHz and the front to back ratio of the coplanar polarization is above 15 dB. The antenna designed can be used in wideband communication systems.
Considering the demand for dual-polarized wideband antenna in communication systems and radar systems, a wideband dual polarized bowtie antenna excited by non-coplanar strip line is proposed in this paper. Dual polarization is realized by two sets of orthogonal bowtie dipoles. The orthogonal bowtie dipoles are fed by a novel balun (a transition from microstrip line into strip line). The tapered microstrip line fed by a coaxial connector is converted into a non-coplanar strip line. Then, the non-coplanar strip line providing symmetrical electric field distribution is a balanced structure which satisfies the balanced feed requirements of bowtie dipoles. Experimental investigations indicate that the impedance bandwidth of 69.23% is available, and the voltage standing wave ratio (VSWR) is below 2 over the frequency range from 8 GHz to 12 GHz. In order to improve the antenna radiation and gain, the dual-polarized antenna is placed in a back cavity. The measure results show that the VSWR is approximately below 3 from 6.8 GHz to 18 GHz, the antenna gain is higher than 0.11 dB from 8 GHz to 12 GHz and the front to back ratio of the coplanar polarization is above 15 dB. The antenna designed can be used in wideband communication systems.
2014,
26: 023101.
doi: 10.3788/HPLPB201426.023101
Abstract:
A calculation method based on rectangular waveguide cavity theory for the open resonance structure with double-row grating and double-groove was proposed. The corrected formula of TE04-mode in the quasi optical cavity structure was proposed for the design optimization, and the electronic efficiency was improved effectively by enhancing the electric field intensity in electron beam tunnel. The cold dispersion character of double-row grating slow-wave structure and the impacts of different parameters on the high frequency characteristic were calculated and analyzed. The results show that the widths of the double-row grating and the electron beam tunnel have great impact on the dispersion character.
A calculation method based on rectangular waveguide cavity theory for the open resonance structure with double-row grating and double-groove was proposed. The corrected formula of TE04-mode in the quasi optical cavity structure was proposed for the design optimization, and the electronic efficiency was improved effectively by enhancing the electric field intensity in electron beam tunnel. The cold dispersion character of double-row grating slow-wave structure and the impacts of different parameters on the high frequency characteristic were calculated and analyzed. The results show that the widths of the double-row grating and the electron beam tunnel have great impact on the dispersion character.
2014,
26: 023201.
doi: 10.3788/HPLPB201426.023201
Abstract:
The analysis of electromagnetic coupling of complex cable bundle system is becoming more difficult with the increasing complexity of the electromagnetic environment. The development of high power electromagnetic radiation technology brings serious electromagnetic threat to those which have complex cable bundle systems and electronic equipment systems. Related to the electromagnetic attacks and electromagnetic protection, there is an urgent need in the aspect of analysis of electromagnetic coupling of complex cable bundle system. Due to the complex geometrical space boundary conditions of complex cable bundle system, it is hard to solve this problem using methods such as the finite difference time domain method(FDTD) and the finite difference frequency domain method(FDFD). Based on the transmission line theory, we use the decomposition skill according to the topology structure to build up a topological model of electromagnetic coupling of complex cable bundle system, and we obtain a method to calculate the terminal voltage and current of the system. We present some simulation examples to verify the availability of electromagnetic topology method in dealing with the electromagnetic coupling effect of cable network.
The analysis of electromagnetic coupling of complex cable bundle system is becoming more difficult with the increasing complexity of the electromagnetic environment. The development of high power electromagnetic radiation technology brings serious electromagnetic threat to those which have complex cable bundle systems and electronic equipment systems. Related to the electromagnetic attacks and electromagnetic protection, there is an urgent need in the aspect of analysis of electromagnetic coupling of complex cable bundle system. Due to the complex geometrical space boundary conditions of complex cable bundle system, it is hard to solve this problem using methods such as the finite difference time domain method(FDTD) and the finite difference frequency domain method(FDFD). Based on the transmission line theory, we use the decomposition skill according to the topology structure to build up a topological model of electromagnetic coupling of complex cable bundle system, and we obtain a method to calculate the terminal voltage and current of the system. We present some simulation examples to verify the availability of electromagnetic topology method in dealing with the electromagnetic coupling effect of cable network.
Statistical characteristics of field distribution in nested frequency stirred reverberation chambers
2014,
26: 023202.
doi: 10.3788/HPLPB201426.023202
Abstract:
In order to figure out the field distributions inside nested frequency stirred reverberation chamber (RC), the field distributions in and out of the nested small RC are analyzed on the basis of the electromagnetic statistical theory. The size of the aperture connecting the two reverberation chambers is thought to be a key factor for the field distribution in the nested small RC. When the aperture is big enough for the electromagnetic wavelength, the field distributions should obey Rayleigh distribution; however, when it is very small, the situation will be similar with the vehicle-to-vehicle(V2V) communication, thus the field distribution in the small RC may follow double Rayleigh distribution. In order to examine the hypothesis of the distribution model, the scattering parameters S21 between the transmitting and receiving antenna are measured by a vector network analyzer in a nested RC, and the sample data are examined by the goodness of fit tests (KS tests). The test results prove the hypothesises, and this is helpful in understanding the test principle, and useful to improve the accuracy of the relevant test and expand the potential applications of frequency stirring nested reverberation chambers.
In order to figure out the field distributions inside nested frequency stirred reverberation chamber (RC), the field distributions in and out of the nested small RC are analyzed on the basis of the electromagnetic statistical theory. The size of the aperture connecting the two reverberation chambers is thought to be a key factor for the field distribution in the nested small RC. When the aperture is big enough for the electromagnetic wavelength, the field distributions should obey Rayleigh distribution; however, when it is very small, the situation will be similar with the vehicle-to-vehicle(V2V) communication, thus the field distribution in the small RC may follow double Rayleigh distribution. In order to examine the hypothesis of the distribution model, the scattering parameters S21 between the transmitting and receiving antenna are measured by a vector network analyzer in a nested RC, and the sample data are examined by the goodness of fit tests (KS tests). The test results prove the hypothesises, and this is helpful in understanding the test principle, and useful to improve the accuracy of the relevant test and expand the potential applications of frequency stirring nested reverberation chambers.
2014,
26: 023203.
doi: 10.3788/HPLPB201426.023203
Abstract:
The power cord of much electronic equipment is twisted-wire pair. Being a special structure, to calculate its load response by radiation is very cumbersome. In many cases, one of the twisted-wire pair is connected with ground, and the height from the ground to twisted-wire pair is more than the spacing between twisted-wire pair. For this model, based on the Taylor model, this paper proposed a simplified model which was calculated the load response of twisted-wire pair by radiation. The twisted-wire pair model was simplified as a single-wire model, its electric current was doubled. By solving the BLT equation, the load response of twisted-wire pair was calculated. The model was proved by comparing with the CST simulation results.
The power cord of much electronic equipment is twisted-wire pair. Being a special structure, to calculate its load response by radiation is very cumbersome. In many cases, one of the twisted-wire pair is connected with ground, and the height from the ground to twisted-wire pair is more than the spacing between twisted-wire pair. For this model, based on the Taylor model, this paper proposed a simplified model which was calculated the load response of twisted-wire pair by radiation. The twisted-wire pair model was simplified as a single-wire model, its electric current was doubled. By solving the BLT equation, the load response of twisted-wire pair was calculated. The model was proved by comparing with the CST simulation results.
2014,
26: 023204.
doi: 10.3788/HPLPB201426.023204
Abstract:
This paper presents an electromagnetic topology model for shielding effectiveness estimation, considering oblique incidence and polarization, based on Robinson equivalent circuit theory. In this model, the apertures are represented by a two-port network, which connects the free space (represented by a transmission line with characteristic impedance Z0) and the enclosure (represented by a short circuited length of rectangular waveguide). The aperture scattering matrix is deduced by equivalent circuit model, based on which a new generalized BLT equation for aperture coupling is proposed. Four test models are designed for the comparison of the EMT algorithm, Robinson algorithm and CST. The simulation result shows that, the EMT algorithm is more accurate than the Robinson algorithm, especially in the high frequency domain; while it is as concise as the Robinson algorithm, and establishes the relationship between shielding effectiveness and parameters of enclosure and apertures, which makes it more practical than CST.
This paper presents an electromagnetic topology model for shielding effectiveness estimation, considering oblique incidence and polarization, based on Robinson equivalent circuit theory. In this model, the apertures are represented by a two-port network, which connects the free space (represented by a transmission line with characteristic impedance Z0) and the enclosure (represented by a short circuited length of rectangular waveguide). The aperture scattering matrix is deduced by equivalent circuit model, based on which a new generalized BLT equation for aperture coupling is proposed. Four test models are designed for the comparison of the EMT algorithm, Robinson algorithm and CST. The simulation result shows that, the EMT algorithm is more accurate than the Robinson algorithm, especially in the high frequency domain; while it is as concise as the Robinson algorithm, and establishes the relationship between shielding effectiveness and parameters of enclosure and apertures, which makes it more practical than CST.
2014,
26: 024001.
doi: 10.3788/HPLPB201426.024001
Abstract:
The electron beam generated by the Dragon-Ⅰlinear induction accelerator struck the target, and an instantaneous optic pyrometer with six working wavelengths was used to measure the temperature process of beam-target interaction region. The thicknesses of targets were 0.1-0.25 mm. Temperature processes of tantalum, aluminum and copper target stricken by strong electron beam were acquired. The highest temperature was up to approximately 9000 K, it reached the region of warm dense matter. The experiment results show that the observable warm dense matter can be acquired by means of the electron beam generated by the Dragon-Ⅰlinear induction accelerator striking specifical targets, and the instantaneous optic pyrometer with multi-working wavelengths is an effective instrument for measuring temperature of the warm dense matter.
The electron beam generated by the Dragon-Ⅰlinear induction accelerator struck the target, and an instantaneous optic pyrometer with six working wavelengths was used to measure the temperature process of beam-target interaction region. The thicknesses of targets were 0.1-0.25 mm. Temperature processes of tantalum, aluminum and copper target stricken by strong electron beam were acquired. The highest temperature was up to approximately 9000 K, it reached the region of warm dense matter. The experiment results show that the observable warm dense matter can be acquired by means of the electron beam generated by the Dragon-Ⅰlinear induction accelerator striking specifical targets, and the instantaneous optic pyrometer with multi-working wavelengths is an effective instrument for measuring temperature of the warm dense matter.
2014,
26: 024002.
doi: 10.3788/HPLPB201426.024002
Abstract:
In order to overcome the adverse factors which were brought in by the extraction of positive ions from PIG ion source for neutron tube currently. PIG negative hydride ion source was used as an ion source for neutron tube. Authors investigated the generation mechanism of hydride ions by PIG ion source，which was expected to be applied to neutron tube. The structure of a PIG ion source was given. According to the mode and conditions of hydride ions generation, and to combine with the CST-based simulation experiments, the existence of dense hydride ions placed around opposite cathode and extraction hole was confirmed. In the experiments, the presence and regularity of distribution of hydride ions were proven by the negative ion source generation system, the yield of the 50 mm neutron tube with negative ion source and drive-in target was more than one order of magnitude of that of the conventional neutron tube with positive ion source.
In order to overcome the adverse factors which were brought in by the extraction of positive ions from PIG ion source for neutron tube currently. PIG negative hydride ion source was used as an ion source for neutron tube. Authors investigated the generation mechanism of hydride ions by PIG ion source，which was expected to be applied to neutron tube. The structure of a PIG ion source was given. According to the mode and conditions of hydride ions generation, and to combine with the CST-based simulation experiments, the existence of dense hydride ions placed around opposite cathode and extraction hole was confirmed. In the experiments, the presence and regularity of distribution of hydride ions were proven by the negative ion source generation system, the yield of the 50 mm neutron tube with negative ion source and drive-in target was more than one order of magnitude of that of the conventional neutron tube with positive ion source.
2014,
26: 024003.
doi: 10.3788/HPLPB201426.024003
Abstract:
The Compton scattering tomography (CST) reconstruction is a nonlinear inverse problem due to the attenuation. One of the solutions is to combine the attenuation coefficients achieved by transmission CT data. However, the CST reconstruction is ill-posed, and its solution would be sensitive to the noise and the projection matrix errors brought by the attenuation coefficients. In order to solve the problem, this paper proposes a novel reconstruction algorithm for CST based on the compressive sensing theory. The novel method comes down the CST reconstruction to a problem for minimizing the images total variation (TV), and then solves it using the Split-Bregman method based on the alternating direction method. Numerical experiments show that the reconstruction quality and the anti-noise performance of the proposed method are improved compared to the algebraic reconstruction technique (ART).
The Compton scattering tomography (CST) reconstruction is a nonlinear inverse problem due to the attenuation. One of the solutions is to combine the attenuation coefficients achieved by transmission CT data. However, the CST reconstruction is ill-posed, and its solution would be sensitive to the noise and the projection matrix errors brought by the attenuation coefficients. In order to solve the problem, this paper proposes a novel reconstruction algorithm for CST based on the compressive sensing theory. The novel method comes down the CST reconstruction to a problem for minimizing the images total variation (TV), and then solves it using the Split-Bregman method based on the alternating direction method. Numerical experiments show that the reconstruction quality and the anti-noise performance of the proposed method are improved compared to the algebraic reconstruction technique (ART).
2014,
26: 024004.
doi: 10.3788/HPLPB201426.024004
Abstract:
Transient X-ray diffraction was used to diagnose the elastic deformation of the LiF single crystal which was shocked along the ［100］ direction. The experiment was implemented in Shenguang Ⅱ. High-intensity lasers irradiated a thin Cu foil to generate helium-like rays as X-ray source, another laser beam irradiated LiF single crystal which was 7 mm7 mm in size, 300 m in thickness as the shocked source. Image plate recorded the shocked diffraction signal of the lattice plane (200) as well as the unshocked signal. The experimental results show that the crystal lattice is compressed, lattice spacing in (200) decreases to result in shifting upwards. The positions of the diffraction lines associated with the (200) lattice plane indicate the compression along ［100］ direction by 11%. Whats more, the results show that it is useful for diagnosing the microscopic dynamic response of the material by transient X-ray diffraction.
Transient X-ray diffraction was used to diagnose the elastic deformation of the LiF single crystal which was shocked along the ［100］ direction. The experiment was implemented in Shenguang Ⅱ. High-intensity lasers irradiated a thin Cu foil to generate helium-like rays as X-ray source, another laser beam irradiated LiF single crystal which was 7 mm7 mm in size, 300 m in thickness as the shocked source. Image plate recorded the shocked diffraction signal of the lattice plane (200) as well as the unshocked signal. The experimental results show that the crystal lattice is compressed, lattice spacing in (200) decreases to result in shifting upwards. The positions of the diffraction lines associated with the (200) lattice plane indicate the compression along ［100］ direction by 11%. Whats more, the results show that it is useful for diagnosing the microscopic dynamic response of the material by transient X-ray diffraction.
2014,
26: 025001.
doi: 10.3788/HPLPB201426.025001
Abstract:
According to the self-healing failure mechanisms of metallized film pulse capacitors in the inertial confinement fusion (ICF) laser device, a more appropriate reliability evaluation method based on shock model was proposed. In existing accelerated degradation test, failure threshold is often constant which is determined in advance, but this is unreasonable in considering individual differences of reliability products and different environmental impact. To solve this problem, the degradation modeling method based on the shock model with random threshold was proposed. Then we used Markov chain Monte Carlo (MCMC) method to estimate parameters. Finally, the random threshold of assessment was compared with fixed threshold, and the reasonability of the proposed model and method was confirmed by simulation of metallized film capacitors. Further analysis shows that different threshold distribution mean values and variances have different influence on the reliability of products.
According to the self-healing failure mechanisms of metallized film pulse capacitors in the inertial confinement fusion (ICF) laser device, a more appropriate reliability evaluation method based on shock model was proposed. In existing accelerated degradation test, failure threshold is often constant which is determined in advance, but this is unreasonable in considering individual differences of reliability products and different environmental impact. To solve this problem, the degradation modeling method based on the shock model with random threshold was proposed. Then we used Markov chain Monte Carlo (MCMC) method to estimate parameters. Finally, the random threshold of assessment was compared with fixed threshold, and the reasonability of the proposed model and method was confirmed by simulation of metallized film capacitors. Further analysis shows that different threshold distribution mean values and variances have different influence on the reliability of products.
Second discharge characteristics of aluminum wire electrical explosion under various argon pressures
2014,
26: 025002.
doi: 10.3788/HPLPB201426.025002
Abstract:
The second discharge characteristics of aluminum wire electrical explosion under various argon pressures were studied in a RLC discharge circuit. The results show that the curve of second discharge voltages by exploding aluminum wire presents a U-shape as the pressure changes. The spectrometer and high speed framing camera were used to study the radiation spectrum and spatial distribution of the electrical explosion plasma to clarify the roles of aluminum vapor and argon in the process of second discharge. It is found that argon participates in discharge process with the discharge channel along the surface of aluminum vapor at lower pressure, while the second discharge happens in aluminum vapor with the discharge channel inside aluminum vapor under higher pressure.
The second discharge characteristics of aluminum wire electrical explosion under various argon pressures were studied in a RLC discharge circuit. The results show that the curve of second discharge voltages by exploding aluminum wire presents a U-shape as the pressure changes. The spectrometer and high speed framing camera were used to study the radiation spectrum and spatial distribution of the electrical explosion plasma to clarify the roles of aluminum vapor and argon in the process of second discharge. It is found that argon participates in discharge process with the discharge channel along the surface of aluminum vapor at lower pressure, while the second discharge happens in aluminum vapor with the discharge channel inside aluminum vapor under higher pressure.
2014,
26: 025003.
doi: 10.3788/HPLPB201426.025003
Abstract:
The circuit and load parameter ranges, in which gaseous aluminum other than core-corona structures could be obtained from the single aluminum wire Z pinch, were analyzed by thermodynamical model. Firstly, the energy deposition criterion and the voltage breakdown criterion were proposed. Secondly, thermodynamical models were established. The circuit parameters were determined by ensuring a rapid decrease of the load current when the wire turns to gas in order to avoid electrical voltage breakdown. Finally, the load current voltage, resistance, and the deposited energy were calculated, and their dependences on the circuit inductance, charging voltage, and wire diameter were analyzed. The calculation results indicated that with a storage capacitance of 150 nF, a charging voltage of 65 kV, and a loop inductance of 300 nH, an aluminum wire of a length of 2 cm and a diameter of 20 m could be heated to gas state. A faster rising current, a smaller wire diameter or little length would enhance the energy deposition in the wire, and are easier to produce gaseous aluminums.
The circuit and load parameter ranges, in which gaseous aluminum other than core-corona structures could be obtained from the single aluminum wire Z pinch, were analyzed by thermodynamical model. Firstly, the energy deposition criterion and the voltage breakdown criterion were proposed. Secondly, thermodynamical models were established. The circuit parameters were determined by ensuring a rapid decrease of the load current when the wire turns to gas in order to avoid electrical voltage breakdown. Finally, the load current voltage, resistance, and the deposited energy were calculated, and their dependences on the circuit inductance, charging voltage, and wire diameter were analyzed. The calculation results indicated that with a storage capacitance of 150 nF, a charging voltage of 65 kV, and a loop inductance of 300 nH, an aluminum wire of a length of 2 cm and a diameter of 20 m could be heated to gas state. A faster rising current, a smaller wire diameter or little length would enhance the energy deposition in the wire, and are easier to produce gaseous aluminums.
2014,
26: 025101.
doi: 10.3788/HPLPB201426.025101
Abstract:
Selection of basis material is a key process for dual high energy X-ray computer tomography basis material decomposition method (BMDM). In order to make clear the influence of different basis materials on material discrimination accuracy and put forward a reasonable principle for the selection of basis material, this article compared the atomic number and electron density of materials being discriminated which were calculated with BMDM based on different basis materials. It further summed up a basis material selection principle named neighboring principle, i.e., choosing a basis material with the atomic number close to that of the material under discrimination could improve the discrimination accuracy, and four energy basis material decomposition methods are put forward based on the principle. Finally, with the Monte-Carlo technique, the validity of the four energy basis material decomposition methods was verified.
Selection of basis material is a key process for dual high energy X-ray computer tomography basis material decomposition method (BMDM). In order to make clear the influence of different basis materials on material discrimination accuracy and put forward a reasonable principle for the selection of basis material, this article compared the atomic number and electron density of materials being discriminated which were calculated with BMDM based on different basis materials. It further summed up a basis material selection principle named neighboring principle, i.e., choosing a basis material with the atomic number close to that of the material under discrimination could improve the discrimination accuracy, and four energy basis material decomposition methods are put forward based on the principle. Finally, with the Monte-Carlo technique, the validity of the four energy basis material decomposition methods was verified.
2014,
26: 025102.
doi: 10.3788/HPLPB201426.025102
Abstract:
A laser wire system is being developed in the electron beam transport line of BEPCⅡ. In this paper, the simulation based on GEANT4 is presented. Firstly, the electromagnetic shower distribution in detector material was simulated to choose an initial detector dimension for Cerenkov process simulation. Then detector responses for different dimensions, Compton signal positions and beam energy were obtained, and the most important result is that the detector dimension is determined at which an optimal signal output can be achieved. The results for different Compton signal positions show that the effect of the beam pipe is significant, which is expected to be important for the beam profile measurement. Furthermore, the simulation results of the detector response and electromagnetic shower energy leakage at different electron beam energy are presented.
A laser wire system is being developed in the electron beam transport line of BEPCⅡ. In this paper, the simulation based on GEANT4 is presented. Firstly, the electromagnetic shower distribution in detector material was simulated to choose an initial detector dimension for Cerenkov process simulation. Then detector responses for different dimensions, Compton signal positions and beam energy were obtained, and the most important result is that the detector dimension is determined at which an optimal signal output can be achieved. The results for different Compton signal positions show that the effect of the beam pipe is significant, which is expected to be important for the beam profile measurement. Furthermore, the simulation results of the detector response and electromagnetic shower energy leakage at different electron beam energy are presented.
2014,
26: 025103.
doi: 10.3788/HPLPB201426.025103
Abstract:
Considering the transverse emittance of electron beam and electron beta oscillation, the statistical physics approach of the analysis to the single pass high-gain free electron laser at saturation is improved and extended to the three-dimensional case. Firstly, a three-dimensional, normalized and simplified model is conducted, then the Vlasov equation of one-dimensional light field including the transverse movement of electrons is derived. In the helical undulator case a three-dimensional statistical physics approach is developed by introducing the conserved quantities of transverse movement, and the relevant code is written for calculation of the saturation intensity, bunching factor and other parameters. For comparison and verification, a direct numerical simulation code of free electron laser which includes N particles is written. The results of numerical simulation and statistical theory are in well accordance with the original one-dimensional simulation and statistical physics approach, and the three-dimensional theory reveals the effect of saturation point parameters introduced by transverse emittance of electron beam and electron beta oscillation.
Considering the transverse emittance of electron beam and electron beta oscillation, the statistical physics approach of the analysis to the single pass high-gain free electron laser at saturation is improved and extended to the three-dimensional case. Firstly, a three-dimensional, normalized and simplified model is conducted, then the Vlasov equation of one-dimensional light field including the transverse movement of electrons is derived. In the helical undulator case a three-dimensional statistical physics approach is developed by introducing the conserved quantities of transverse movement, and the relevant code is written for calculation of the saturation intensity, bunching factor and other parameters. For comparison and verification, a direct numerical simulation code of free electron laser which includes N particles is written. The results of numerical simulation and statistical theory are in well accordance with the original one-dimensional simulation and statistical physics approach, and the three-dimensional theory reveals the effect of saturation point parameters introduced by transverse emittance of electron beam and electron beta oscillation.
2014,
26: 025104.
doi: 10.3788/HPLPB201426.025104
Abstract:
Maintaining and preserving a high density of particles in phase-space is an important requirement for the high brightness beams. In this paper, a photo-injector is optimized based on Dalian Coherent Light Source (DCLS) linac by using genetic algorithm (GA). Compared with traditional optimization methods, the great advantage of GA is its high efficiency with greater accuracy. In the GA optimization, it is convenient to transform the multi-objective problem into a single-objective optimization by using the weight factor. Because of the beam stability requirements for photo-injector, it is of interest to control the arrival time jitter within 150 fs by adopting GA optimization.
Maintaining and preserving a high density of particles in phase-space is an important requirement for the high brightness beams. In this paper, a photo-injector is optimized based on Dalian Coherent Light Source (DCLS) linac by using genetic algorithm (GA). Compared with traditional optimization methods, the great advantage of GA is its high efficiency with greater accuracy. In the GA optimization, it is convenient to transform the multi-objective problem into a single-objective optimization by using the weight factor. Because of the beam stability requirements for photo-injector, it is of interest to control the arrival time jitter within 150 fs by adopting GA optimization.
2014,
26: 029001.
doi: 10.3788/HPLPB201426.029001
Abstract:
Researches on the laser deposition repair of BT20 alloy forgings having hole damage were carried out, and the microstructure characteristic of laser deposition repair component was analyzed. There was a dense metallurgical bond between the repaired zone and the substrate. The Al, Zr, Mo, V elements were uniformly distributed without fluctuation and segregation from the matrix to the laser repaired zone. The repaired component experienced a continuous microstructural transition from duplex microstructure with equiaxed and lamellar / in the repaired substrate to the epitaxial coarser columnar with basket weave / through heat-affected zone. In the heat affected zone, the microstructure changed from bimodal structure to the basket weave structure gradually, and the repaired zone was characterized by a fine / lamellar microstructure with various random orientations, and the was about 0.4-0.5 m, which should be related to the rapid solidification and phase transformation during the process. It is found that unsuitable laser process parameters and large hole sloped angle can cause defects such as gas porosities and ill bonding. The results of repaired sample tensile test at room temperature show that the tensile strength approaches to the wrought BT20 alloy, while its toughness is a little higher.
Researches on the laser deposition repair of BT20 alloy forgings having hole damage were carried out, and the microstructure characteristic of laser deposition repair component was analyzed. There was a dense metallurgical bond between the repaired zone and the substrate. The Al, Zr, Mo, V elements were uniformly distributed without fluctuation and segregation from the matrix to the laser repaired zone. The repaired component experienced a continuous microstructural transition from duplex microstructure with equiaxed and lamellar / in the repaired substrate to the epitaxial coarser columnar with basket weave / through heat-affected zone. In the heat affected zone, the microstructure changed from bimodal structure to the basket weave structure gradually, and the repaired zone was characterized by a fine / lamellar microstructure with various random orientations, and the was about 0.4-0.5 m, which should be related to the rapid solidification and phase transformation during the process. It is found that unsuitable laser process parameters and large hole sloped angle can cause defects such as gas porosities and ill bonding. The results of repaired sample tensile test at room temperature show that the tensile strength approaches to the wrought BT20 alloy, while its toughness is a little higher.
2014,
26: 029002.
doi: 10.3788/HPLPB201426.029002
Abstract:
In order to study the influence of laser micro texture carbide surface on its surface wettability, this paper uses the optical fiber laser power(3,5,7,9,10 W) and machining number (1,2,3,4,5) to get different micro-pores and then uses cultra-depth three-dimensional microscopy and optical microscopy to analyze their microscopy. Optical contact angle meter is used to discuss the relationships between micro-textured surface (diameter, depth and density of micro-pores) and its wettability. The results show that with the increase of the laser power, the micro indentation depth increases while the diameter variation is not obvious, the hydrophilicity of the surface decreases with the increase of micro indentation depth, increases with the increase of the micro-pore diameter and reaches the extremum with the increase of the density of the micro-textured surface.
In order to study the influence of laser micro texture carbide surface on its surface wettability, this paper uses the optical fiber laser power(3,5,7,9,10 W) and machining number (1,2,3,4,5) to get different micro-pores and then uses cultra-depth three-dimensional microscopy and optical microscopy to analyze their microscopy. Optical contact angle meter is used to discuss the relationships between micro-textured surface (diameter, depth and density of micro-pores) and its wettability. The results show that with the increase of the laser power, the micro indentation depth increases while the diameter variation is not obvious, the hydrophilicity of the surface decreases with the increase of micro indentation depth, increases with the increase of the micro-pore diameter and reaches the extremum with the increase of the density of the micro-textured surface.
2014,
26: 029003.
doi: 10.3788/HPLPB201426.029003
Abstract:
This paper concentrates on the measurement and analysis of laser ablation effect of particularly prepared aerospace material, polycarbosilane (PCS). Laser ablation experiment setup is designed and built, based on a continuous-wave high-power solid-state laser (CWHPSSL). Metal-shell samples with composite PCS are prepared. Then a group of laser ablation experiments are performed on those samples. They are processed by laser beam with thousands of W/cm2. The results, including the ablation morphology and temperature data, are shown and discussed. Temperature data give a good demonstration of the protection effect of composite coating, and in the meanwhile the minor-morphologies in the ablated region hint the principle of PCS laser-proof effect. After that, a theoretical investigation is carried out. Fourier equation of heat conduction is applied to modeling the temperature field during ablation process. The simulation provides a good explanation on the principle of laser-proof effect of PCS composite coating. The results demonstrate that, with the protection of PCS composite coating, kilowatt-level laser only results in hundreds of Celcius temperature increment of steel substrate.
This paper concentrates on the measurement and analysis of laser ablation effect of particularly prepared aerospace material, polycarbosilane (PCS). Laser ablation experiment setup is designed and built, based on a continuous-wave high-power solid-state laser (CWHPSSL). Metal-shell samples with composite PCS are prepared. Then a group of laser ablation experiments are performed on those samples. They are processed by laser beam with thousands of W/cm2. The results, including the ablation morphology and temperature data, are shown and discussed. Temperature data give a good demonstration of the protection effect of composite coating, and in the meanwhile the minor-morphologies in the ablated region hint the principle of PCS laser-proof effect. After that, a theoretical investigation is carried out. Fourier equation of heat conduction is applied to modeling the temperature field during ablation process. The simulation provides a good explanation on the principle of laser-proof effect of PCS composite coating. The results demonstrate that, with the protection of PCS composite coating, kilowatt-level laser only results in hundreds of Celcius temperature increment of steel substrate.
