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RSS2014 Vol. 26, No. 10
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2014,
26: 100201.
doi: 10.11884/HPLPB201426.100201
Abstract:
According to the demands of Z-pinch driven fusion-fission reactor(Z-FFR), several possible technical schemes are analyzed and evaluated. A novel technical scheme named mixed-mode LTD is proposed. A conceptual design of Z-FFR driver is presented based on mixed-mode LTD scheme. The main directions for key technologies development are pointed out. A road-map is proposed for the super-power Z-pinch driver development.
According to the demands of Z-pinch driven fusion-fission reactor(Z-FFR), several possible technical schemes are analyzed and evaluated. A novel technical scheme named mixed-mode LTD is proposed. A conceptual design of Z-FFR driver is presented based on mixed-mode LTD scheme. The main directions for key technologies development are pointed out. A road-map is proposed for the super-power Z-pinch driver development.
2014,
26: 101001.
doi: 10.11884/HPLPB201426.101001
Abstract:
Based on the ray tracing method the laser intensity distribution of single DL bar collimated with micro spherical cylindrical lens was analyzed in detail. We found that the intensity distribution of output laser have a better flat shape when the divergence angle is about 5. A beam reshape system was designed for a 25-bar DL stack. The system includes microlens of fast axis collimating, coupling lens of fast axis and coupling lens of slow axis. The laser medium to be pumped was designed at the focus plane of fast axis coupling lens and close to the imaging plane of slow axis coupling lens. A 7 mm8 mm pump beam was obtained with intensity uniformity of 90%. The coupling efficiency of the beam reshaping system reached 85%.
Based on the ray tracing method the laser intensity distribution of single DL bar collimated with micro spherical cylindrical lens was analyzed in detail. We found that the intensity distribution of output laser have a better flat shape when the divergence angle is about 5. A beam reshape system was designed for a 25-bar DL stack. The system includes microlens of fast axis collimating, coupling lens of fast axis and coupling lens of slow axis. The laser medium to be pumped was designed at the focus plane of fast axis coupling lens and close to the imaging plane of slow axis coupling lens. A 7 mm8 mm pump beam was obtained with intensity uniformity of 90%. The coupling efficiency of the beam reshaping system reached 85%.
2014,
26: 100202.
doi: 10.11884/HPLPB201426.100202
Abstract:
The Z-pinch driven fusion-fission hybrid power reactor(Z-FFR) has remarkable advantages in nuclear security, economy, permanence and environment-friendliness, it can promisingly be millennial energy source dealing effectively with future energy crisis and climate problem. This article introduces the status quo of the conceptual research on Z-FFR from aspects of fusion-target physics, low-repetitive Z-pinch driver development, sub-critical fission reactor design and fuel cycle analysis.
The Z-pinch driven fusion-fission hybrid power reactor(Z-FFR) has remarkable advantages in nuclear security, economy, permanence and environment-friendliness, it can promisingly be millennial energy source dealing effectively with future energy crisis and climate problem. This article introduces the status quo of the conceptual research on Z-FFR from aspects of fusion-target physics, low-repetitive Z-pinch driver development, sub-critical fission reactor design and fuel cycle analysis.
2014,
26: 100203.
doi: 10.11884/HPLPB201426.100203
Abstract:
In this paper, we propose a preliminary design for a fusion-fission hybrid energy reactor (FFHER), based on current fusion science and technology and well-developed fission technology. Design rules are listed and a primary concept blanket with uranium alloy as fuel and water as coolant is put forward. The uranium fuel can be natural uranium, LWR spent fuel, or depleted uranium. The FFHER design can increase the utilization rate of uranium in a comparatively simple way to sustain the development of nuclear energy. The interaction between the fusion neutron and the uranium fuel with the aim of achieving greater energy multiplication and tritium sustainability is studied. Other concept hybrid reactor designs are also reviewed. Integral neutron experiments were carried out to verify the credibility of our proposed physical design. The combination of the physical design with the related thermal hydraulic design, alloy fuel manufacture, and nuclear fuel cycle programs provides the science and technology basis for future development of the FFHER concept in China.
In this paper, we propose a preliminary design for a fusion-fission hybrid energy reactor (FFHER), based on current fusion science and technology and well-developed fission technology. Design rules are listed and a primary concept blanket with uranium alloy as fuel and water as coolant is put forward. The uranium fuel can be natural uranium, LWR spent fuel, or depleted uranium. The FFHER design can increase the utilization rate of uranium in a comparatively simple way to sustain the development of nuclear energy. The interaction between the fusion neutron and the uranium fuel with the aim of achieving greater energy multiplication and tritium sustainability is studied. Other concept hybrid reactor designs are also reviewed. Integral neutron experiments were carried out to verify the credibility of our proposed physical design. The combination of the physical design with the related thermal hydraulic design, alloy fuel manufacture, and nuclear fuel cycle programs provides the science and technology basis for future development of the FFHER concept in China.
2014,
26: 101002.
doi: 10.11884/HPLPB201426.101002
Abstract:
By constructing a turbulence phase screen with the method of power spectrum inversion and translating the phase screen, the temporal variations of turbulence caused by atmospheric wind speed were simulated. The propagation characteristics of laser beams in atmospheric turbulence including temporal evolution were simulated and analyzed, and the variations of phase characteristics of laser beams in atmospheric turbulence caused by atmospheric wind speed were quantitatively analyzed from the view of wavefront power spectral density. And the correction effect of deformable mirror for the distorted wavefront was simulated by using influence function. The adaptive correction effect for the distorted wavefront of laser beams propagating in atmospheric turbulence was estimated, and the influence of atmospheric wind speed on the correction effect was analyzed. The results show that, the influence of atmospheric wind speed on the phase characteristics of laser beams in boundary layer turbulence is very small, whereas for the laser beams in free layer turbulence, the higher the atmospheric wind speed, the severer the wavefront phase distortion and the larger the proportion of high frequency in distorted wavefront. The influence of atmospheric wind speed on the correction effect of annular beams is smaller than that on the correction of flat-topped beams, and the influence on the correction effect decreases gradually with increasing the beam order of annular beams. To a certain extent of distorted phase, the severer the phase distortion of annular beams, the weaker the influence of atmospheric wind speed on the correction effect.
By constructing a turbulence phase screen with the method of power spectrum inversion and translating the phase screen, the temporal variations of turbulence caused by atmospheric wind speed were simulated. The propagation characteristics of laser beams in atmospheric turbulence including temporal evolution were simulated and analyzed, and the variations of phase characteristics of laser beams in atmospheric turbulence caused by atmospheric wind speed were quantitatively analyzed from the view of wavefront power spectral density. And the correction effect of deformable mirror for the distorted wavefront was simulated by using influence function. The adaptive correction effect for the distorted wavefront of laser beams propagating in atmospheric turbulence was estimated, and the influence of atmospheric wind speed on the correction effect was analyzed. The results show that, the influence of atmospheric wind speed on the phase characteristics of laser beams in boundary layer turbulence is very small, whereas for the laser beams in free layer turbulence, the higher the atmospheric wind speed, the severer the wavefront phase distortion and the larger the proportion of high frequency in distorted wavefront. The influence of atmospheric wind speed on the correction effect of annular beams is smaller than that on the correction of flat-topped beams, and the influence on the correction effect decreases gradually with increasing the beam order of annular beams. To a certain extent of distorted phase, the severer the phase distortion of annular beams, the weaker the influence of atmospheric wind speed on the correction effect.
2014,
26: 101003.
doi: 10.11884/HPLPB201426.101003
Abstract:
An adaptive dual-tree complex wavelet algorithm was proposed to solve the classical image restoration problem. This method is more suited to the situation that a priori information of remote-sensing image is hard to obtain. The algorithm estimates regularization parameter from both the blurred level and the noise level, and estimates the noise using an empirical formula. In practical applications, the algorithm can effectively overcome the drawback of the two-step iterative shrinkage algorithm due to the use of a fixed parameter, and better imagery restoration quality could be obtained. Experimental results show that the image peak SNR improves 0.64-12.23 dB and the convergence speed improves 1.4-16 times. The algorithm has apparent advantages with respect of producing better restoration results, noise disturbance suppression and the reduction of computation time.
An adaptive dual-tree complex wavelet algorithm was proposed to solve the classical image restoration problem. This method is more suited to the situation that a priori information of remote-sensing image is hard to obtain. The algorithm estimates regularization parameter from both the blurred level and the noise level, and estimates the noise using an empirical formula. In practical applications, the algorithm can effectively overcome the drawback of the two-step iterative shrinkage algorithm due to the use of a fixed parameter, and better imagery restoration quality could be obtained. Experimental results show that the image peak SNR improves 0.64-12.23 dB and the convergence speed improves 1.4-16 times. The algorithm has apparent advantages with respect of producing better restoration results, noise disturbance suppression and the reduction of computation time.
2014,
26: 101005.
doi: 10.11884/HPLPB201426.101005
Abstract:
In order to obtain high power all-fiber mid-IR supercontinuum source, the fluoride fiber is pumped by homemade erbium-doped mode-locked fiber laser after two amplifiers to 1.67 W. The supercontinuum from 1 000 nm to 2 400 nm is obtained. The spectrum of the supercontinuum is gradually broadening with the increase of the pump laser power. The output power and the conversion efficiency are 1.21 W and 72% respectively. Experimental results show that supercontinuum has a strong spectrum modulation, and the power spectrum density decreases to 0 mW/nm at certain spectrum points which does not depend on pump power.
In order to obtain high power all-fiber mid-IR supercontinuum source, the fluoride fiber is pumped by homemade erbium-doped mode-locked fiber laser after two amplifiers to 1.67 W. The supercontinuum from 1 000 nm to 2 400 nm is obtained. The spectrum of the supercontinuum is gradually broadening with the increase of the pump laser power. The output power and the conversion efficiency are 1.21 W and 72% respectively. Experimental results show that supercontinuum has a strong spectrum modulation, and the power spectrum density decreases to 0 mW/nm at certain spectrum points which does not depend on pump power.
2014,
26: 101006.
doi: 10.11884/HPLPB201426.101006
Abstract:
In optical-feedback cavity ring-down spectroscopy (OF-CRDS), the data processing of the measured spectrum is often a troubling problem for a special spectral phenomenon called spectral ripple. With an OF-CRDS example of H2O molecule in the spectral range of 6 590.8-6 591.6 cm-1, a data processing method based on the characteristics analyses of spectral ripple is demonstrated. The linewidth of the H2O molecule at 6 590.871 cm-1 is determined as about 0.100 3 cm-1 with this method and its difference compared to the calculated result from Hitran database is 0.002 cm-1, which verifies the effectiveness of this method.
In optical-feedback cavity ring-down spectroscopy (OF-CRDS), the data processing of the measured spectrum is often a troubling problem for a special spectral phenomenon called spectral ripple. With an OF-CRDS example of H2O molecule in the spectral range of 6 590.8-6 591.6 cm-1, a data processing method based on the characteristics analyses of spectral ripple is demonstrated. The linewidth of the H2O molecule at 6 590.871 cm-1 is determined as about 0.100 3 cm-1 with this method and its difference compared to the calculated result from Hitran database is 0.002 cm-1, which verifies the effectiveness of this method.
2014,
26: 101007.
doi: 10.11884/HPLPB201426.101007
Abstract:
The test facility of 2-D supersonic-supersonic ejector was constructed. Varieties of tests were carried out to investigate the starting and load characteristics of a second throat ejector. The schlieren photographs of the mixing chamber flow field were got by schlieren apparatus synchronously. The experimental results show that there are shocks brought by background pressure in mixing chamber fore part while the ejector starts critically.It is possible that the main shocks originate from the mixing chamber rearward while the ejector starts completely. Secondary flow has booster action for ejector starting which can make shocks to move backward in evidence. As the secondary flow is injected, the mixing layer between primary and secondary flow will occur obviously. If the pressures of primary and secondary flow are not matched, a strong oblique shock wave will be formed at nozzle exit inwall, which will be reflected between the wall and mixing layer, then the capability of primary flow will be reduced.
The test facility of 2-D supersonic-supersonic ejector was constructed. Varieties of tests were carried out to investigate the starting and load characteristics of a second throat ejector. The schlieren photographs of the mixing chamber flow field were got by schlieren apparatus synchronously. The experimental results show that there are shocks brought by background pressure in mixing chamber fore part while the ejector starts critically.It is possible that the main shocks originate from the mixing chamber rearward while the ejector starts completely. Secondary flow has booster action for ejector starting which can make shocks to move backward in evidence. As the secondary flow is injected, the mixing layer between primary and secondary flow will occur obviously. If the pressures of primary and secondary flow are not matched, a strong oblique shock wave will be formed at nozzle exit inwall, which will be reflected between the wall and mixing layer, then the capability of primary flow will be reduced.
2014,
26: 101008.
doi: 10.11884/HPLPB201426.101008
Abstract:
The relative spectral power is used for evaluating the spectral distribution of ultrashort laser pulse. The relative spectral power measurement for ultrashort laser pulse is studied based on the standard illuminant of bromine-tungsten lamp, and analytical expressions of the relative spectral power are clearly given. Experimental results for the relative spectral power measurement on SILEX-I laser facility using SP2760 spectrometer show that the spectral distribution evaluated by the relative spectral power is significantly different comparing with the original spectral response. The uncertainty-analysis of experimental results is also given, and the extended relative uncertainty is 1.7%.
The relative spectral power is used for evaluating the spectral distribution of ultrashort laser pulse. The relative spectral power measurement for ultrashort laser pulse is studied based on the standard illuminant of bromine-tungsten lamp, and analytical expressions of the relative spectral power are clearly given. Experimental results for the relative spectral power measurement on SILEX-I laser facility using SP2760 spectrometer show that the spectral distribution evaluated by the relative spectral power is significantly different comparing with the original spectral response. The uncertainty-analysis of experimental results is also given, and the extended relative uncertainty is 1.7%.
2014,
26: 101009.
doi: 10.11884/HPLPB201426.101009
Abstract:
The nonlinear effect and material damage existing in high power fiber lasers restrict their output power. A large mode area fiber, which could reduce the power density and improve the nonlinear threshold, is one of the solutions to the problem. A photonic crystal fiber with air holes at wavelength scales was designed based on the effective index model and finite element analysis. The single-mode properties as well as the influence of structural parameters on the mode area and dispersion were investigated. Considering practical applications, we designed a large mode area photonic crystal fiber, operating in the range of 0.40~1.55 m, mode area between 112.74~258.87 m2, centering at 1.27 m with dispersion compensation ability. Our investigations may provide new references to the optimization and fabrication of large mode area fiber for high power fiber lasers.
The nonlinear effect and material damage existing in high power fiber lasers restrict their output power. A large mode area fiber, which could reduce the power density and improve the nonlinear threshold, is one of the solutions to the problem. A photonic crystal fiber with air holes at wavelength scales was designed based on the effective index model and finite element analysis. The single-mode properties as well as the influence of structural parameters on the mode area and dispersion were investigated. Considering practical applications, we designed a large mode area photonic crystal fiber, operating in the range of 0.40~1.55 m, mode area between 112.74~258.87 m2, centering at 1.27 m with dispersion compensation ability. Our investigations may provide new references to the optimization and fabrication of large mode area fiber for high power fiber lasers.
2014,
26: 101010.
doi: 10.11884/HPLPB201426.101010
Abstract:
A fast and accurate ray-target face incident angle measurement algorithm is proposed to meet the requirement of practical ray-target face incident angle measurement mission. Since the geometry distribution relationship among the advanced-set feature points changes along with the pose transformation, ray-target face incident angle could be measured in a non-contact way. On the basis of drawing target face identification points, ray-target face incident angles are calculated using optical sensor internal parameters. Both simulations and experiments are conducted to prove the effectiveness and practicability of the proposed algorithm. The results confirm the high stability and reliability of the proposed method.
A fast and accurate ray-target face incident angle measurement algorithm is proposed to meet the requirement of practical ray-target face incident angle measurement mission. Since the geometry distribution relationship among the advanced-set feature points changes along with the pose transformation, ray-target face incident angle could be measured in a non-contact way. On the basis of drawing target face identification points, ray-target face incident angles are calculated using optical sensor internal parameters. Both simulations and experiments are conducted to prove the effectiveness and practicability of the proposed algorithm. The results confirm the high stability and reliability of the proposed method.
2014,
26: 101011.
doi: 10.11884/HPLPB201426.101011
Abstract:
The images reconstructed by traditional regularization super-resolution often have over smoothing or different artifacts residue. The cause of artifacts is analyzed by super-resolution reconstruction model. To improve the disadvantage of traditional methods, this paper proposes an adaptive regularization algorithm based on image region information, the original image is divided into smooth and non-smooth regions by the information, each type of region use different type of prior model as constraints. Considering the characteristics of human vision, regional information is used to achieve adaptive regularization parameter selection. Experiment results indicate that the proposed algorithm can improve the quality of reconstructed image with better artifacts smoothing and details preserving than traditional method and regularization with single prior model, which provides a theoretical reference to enhance infrared and visible light image super-resolution reconstruction quality.
The images reconstructed by traditional regularization super-resolution often have over smoothing or different artifacts residue. The cause of artifacts is analyzed by super-resolution reconstruction model. To improve the disadvantage of traditional methods, this paper proposes an adaptive regularization algorithm based on image region information, the original image is divided into smooth and non-smooth regions by the information, each type of region use different type of prior model as constraints. Considering the characteristics of human vision, regional information is used to achieve adaptive regularization parameter selection. Experiment results indicate that the proposed algorithm can improve the quality of reconstructed image with better artifacts smoothing and details preserving than traditional method and regularization with single prior model, which provides a theoretical reference to enhance infrared and visible light image super-resolution reconstruction quality.
2014,
26: 101012.
doi: 10.11884/HPLPB201426.101012
Abstract:
Using a special spectral filtering method, the anisoplanatism of expanded beacon in two typical scenes is modelled. And the formulae that describe the total expanded anisoplanatic error and different Zernike model components are obtained. Using two typical turbulent outlines, the characteristics of the expanded anisoplanatic error are studied, and the results indicate that: when the dimension of beacon equals to that of the receiver aperture, the expanded and focal coupling anisoplanatic error is minimal, while the high-order components that the piston, tilt and focus components are removed are not minimal. When the high-order components are minimal, the dimension of beacon should be less than that of the receiver aperture. When the beacon expanded angle equals to beacon departure angle, the expanded anisoplanatic error is about 2.2% of the angle anisoplanatic error. Relative to the angle or focal anisoplanatic error, the anisoplanatic error induced by the dimension of beacon is very little. And in many scenes, it can be ignored.
Using a special spectral filtering method, the anisoplanatism of expanded beacon in two typical scenes is modelled. And the formulae that describe the total expanded anisoplanatic error and different Zernike model components are obtained. Using two typical turbulent outlines, the characteristics of the expanded anisoplanatic error are studied, and the results indicate that: when the dimension of beacon equals to that of the receiver aperture, the expanded and focal coupling anisoplanatic error is minimal, while the high-order components that the piston, tilt and focus components are removed are not minimal. When the high-order components are minimal, the dimension of beacon should be less than that of the receiver aperture. When the beacon expanded angle equals to beacon departure angle, the expanded anisoplanatic error is about 2.2% of the angle anisoplanatic error. Relative to the angle or focal anisoplanatic error, the anisoplanatic error induced by the dimension of beacon is very little. And in many scenes, it can be ignored.
2014,
26: 101013.
doi: 10.11884/HPLPB201426.101013
Abstract:
A self-starting 2 m a fiber passively mode-locked Tm3+-doped fiber laser based on nonlinear loop mirror (NOLM) was demonstrated. The laser operated at a continuous wave or unstable pulses regime after reaching the launched pump power of 3 W. Self-starting mode-locked pulses centered at 2 061.5 nm with an FWHM of 18.1 nm and an average output power of 8.8 mW were achieved when the launched pump power increased to 4.69 W. Continuously increasing to the maximum launched pump power of 7.56 W, stable mode-locked pulses centered at 2 062.2 nm with a FWHM of 17.1 nm were produced at a slope efficiency of 6.2%. The pulses operated at the repetition rate of 4.26 MHz with a single pulse energy up to 65.6 nJ and a pulse width of 424 fs. To the best of our knowledge, this was the first demonstration on mode-locked fiber laser based on NOLM at 2 m region with the highest single pulse energy.
A self-starting 2 m a fiber passively mode-locked Tm3+-doped fiber laser based on nonlinear loop mirror (NOLM) was demonstrated. The laser operated at a continuous wave or unstable pulses regime after reaching the launched pump power of 3 W. Self-starting mode-locked pulses centered at 2 061.5 nm with an FWHM of 18.1 nm and an average output power of 8.8 mW were achieved when the launched pump power increased to 4.69 W. Continuously increasing to the maximum launched pump power of 7.56 W, stable mode-locked pulses centered at 2 062.2 nm with a FWHM of 17.1 nm were produced at a slope efficiency of 6.2%. The pulses operated at the repetition rate of 4.26 MHz with a single pulse energy up to 65.6 nJ and a pulse width of 424 fs. To the best of our knowledge, this was the first demonstration on mode-locked fiber laser based on NOLM at 2 m region with the highest single pulse energy.
2014,
26: 101014.
doi: 10.11884/HPLPB201426.101014
Abstract:
It is difficult to find out fault chemical oxygen iodine laser (COIL) because of its complex structure and interactions between the subsystems. To solve the COIL fault diagnostic problems, along with the development of integrate and practical COILs, it is required for keeping the device performance and reducing the maintenance cost and human resource input. Fault analysis of COILs has been done based on the fault tree analysis method. The fault tree of a COIL was established combining with on-line monitoring parameters: iodine cavity pressure, iodine venturi pressure, p-t curve, main helium pressure, chlorine pressure, single oxygen generator pressure, upstream pressure, optical cavity pressure. According to the 3 rule, the accuracy of fault diagnosis for the COIL is 94.5%. Furthermore, improvement put suggestions has been forward.
It is difficult to find out fault chemical oxygen iodine laser (COIL) because of its complex structure and interactions between the subsystems. To solve the COIL fault diagnostic problems, along with the development of integrate and practical COILs, it is required for keeping the device performance and reducing the maintenance cost and human resource input. Fault analysis of COILs has been done based on the fault tree analysis method. The fault tree of a COIL was established combining with on-line monitoring parameters: iodine cavity pressure, iodine venturi pressure, p-t curve, main helium pressure, chlorine pressure, single oxygen generator pressure, upstream pressure, optical cavity pressure. According to the 3 rule, the accuracy of fault diagnosis for the COIL is 94.5%. Furthermore, improvement put suggestions has been forward.
2014,
26: 101015.
doi: 10.11884/HPLPB201426.101015
Abstract:
In order to raise the output power and lower the far field divergence angles of 980 nm diode laser, a high refractive index inner waveguide is introduced in the n-type waveguide structure, which is based on the asymmetric waveguide structure. The research is conducted by SimLastip. Meanwhile, the semiconductor laser is fabricated with the epitaxial layer grown by a solid source molecular beam epitaxy (MBE) system. The fabricated 980 nm laser diode with 100 m strip width and 1000 m cavity length has a threshold current of 97 mA and a slope efficiency of 1.01 W/A. When the injection current is 500 mA, the far field divergence angles are 29(vertical) by 8 (horizontal), which is consistent with the simulated result. The theoretical and experimental results indicate that the inner waveguide structure can achieve high power output, effectively reduce the far field divergence angle and improve the beam quality of the device.
In order to raise the output power and lower the far field divergence angles of 980 nm diode laser, a high refractive index inner waveguide is introduced in the n-type waveguide structure, which is based on the asymmetric waveguide structure. The research is conducted by SimLastip. Meanwhile, the semiconductor laser is fabricated with the epitaxial layer grown by a solid source molecular beam epitaxy (MBE) system. The fabricated 980 nm laser diode with 100 m strip width and 1000 m cavity length has a threshold current of 97 mA and a slope efficiency of 1.01 W/A. When the injection current is 500 mA, the far field divergence angles are 29(vertical) by 8 (horizontal), which is consistent with the simulated result. The theoretical and experimental results indicate that the inner waveguide structure can achieve high power output, effectively reduce the far field divergence angle and improve the beam quality of the device.
2014,
26: 101016.
doi: 10.11884/HPLPB201426.101016
Abstract:
Synthesizing wideband optical frequency-stepped chirp signal (FSCS) with independent lasers for high resolution ranging is suggested. Based on the theory of FSCS signal ranging, both the influence of laser parameters on synthesizing FSCS signal and their error tolerances are investigated. Numerical results show that among the three laser parameters, jitters in starting frequency and starting time are the main factors causing range resolution deterioration. Meanwhile, a high resolution ranging experiment with optical FSCS signal is demonstrated, where the FSCS signal is simulated by optical chopping a linear wavelength sweeping laser at the center wavelength of 1550 nm and line width of 150 kHz. Both the theoretical analysis and the experimental results show that it is workable to form synthetic FSCS signal with several linear-chirped lasers for high resolution ranging.
Synthesizing wideband optical frequency-stepped chirp signal (FSCS) with independent lasers for high resolution ranging is suggested. Based on the theory of FSCS signal ranging, both the influence of laser parameters on synthesizing FSCS signal and their error tolerances are investigated. Numerical results show that among the three laser parameters, jitters in starting frequency and starting time are the main factors causing range resolution deterioration. Meanwhile, a high resolution ranging experiment with optical FSCS signal is demonstrated, where the FSCS signal is simulated by optical chopping a linear wavelength sweeping laser at the center wavelength of 1550 nm and line width of 150 kHz. Both the theoretical analysis and the experimental results show that it is workable to form synthetic FSCS signal with several linear-chirped lasers for high resolution ranging.
2014,
26: 101017.
doi: 10.11884/HPLPB201426.101017
Abstract:
In order to realize uniform coating of photoresist on large area substrates, a small meniscus coating applicator is designed and assembled, and it is used to coat a substrate of 200 mm200 mm. Then a thickness measurement system based on white light interference spectrometer is installed to measure the thickness distribution of the coated photoresist, the result shows that the peak value of the deviation is less than 5%. Thickness uniformity is analyzed for further optimizing the coating system and coating parameters. Finally the accuracy of the thickness measurement system is tested by comparing the measuring results with that of a surface profiler which has very high resolution and has been calibrated, and the deviation is less than 0.8%.
In order to realize uniform coating of photoresist on large area substrates, a small meniscus coating applicator is designed and assembled, and it is used to coat a substrate of 200 mm200 mm. Then a thickness measurement system based on white light interference spectrometer is installed to measure the thickness distribution of the coated photoresist, the result shows that the peak value of the deviation is less than 5%. Thickness uniformity is analyzed for further optimizing the coating system and coating parameters. Finally the accuracy of the thickness measurement system is tested by comparing the measuring results with that of a surface profiler which has very high resolution and has been calibrated, and the deviation is less than 0.8%.
2014,
26: 101018.
doi: 10.11884/HPLPB201426.101018
Abstract:
In this paper, wavelet methods are used to reconstruct diverse aberration in inter-satellite communication system where two reconstruction indicators are considered: reconstruction accuracy and complexity. A selection method of optimal wavelet basis is given based on the synthesized analysis of these two indicators. Simulation results show that for the reconstruction of wavefront aberration, wavelet selected by the proposed method has higher accuracy and lower complexity than the traditional method by Zernike polynomials.
In this paper, wavelet methods are used to reconstruct diverse aberration in inter-satellite communication system where two reconstruction indicators are considered: reconstruction accuracy and complexity. A selection method of optimal wavelet basis is given based on the synthesized analysis of these two indicators. Simulation results show that for the reconstruction of wavefront aberration, wavelet selected by the proposed method has higher accuracy and lower complexity than the traditional method by Zernike polynomials.
2014,
26: 101019.
doi: 10.11884/HPLPB201426.101019
Abstract:
As a key part of the infrared thermal waving non-destructive testing technique, the thermal wave image segmentation plays an important role in the efficient detection and accurate evaluation of the structural defect. In order to minimize the influence caused by the noisy background and low contrast, the support vector machine was applied to the thermal wave image segmentation. Combining with the Wiener filter, the proposed procedure pre-processed the thermal wave image at first to enhance the contrast. Consequently, several pixel values of the background and target regions were respectively chosen to compose the characteristic vectors and input to the support vector machine, whose kernel function was set to being radial based function. Finally, the classifier obtained by the training step was applied to the thermal wave image and a binary image was obtained, which had been carried out the thermal wave image segmentation. Experimental results show that the proposed method can efficiently enhance the contrast between the background and target regions with a powerful noise retraining capability. Compared with the image segmentation method based on the hard threshold, the proposed procedure is of more benefit to the identification and evaluation of the defects and is valuable for the engineering application.
As a key part of the infrared thermal waving non-destructive testing technique, the thermal wave image segmentation plays an important role in the efficient detection and accurate evaluation of the structural defect. In order to minimize the influence caused by the noisy background and low contrast, the support vector machine was applied to the thermal wave image segmentation. Combining with the Wiener filter, the proposed procedure pre-processed the thermal wave image at first to enhance the contrast. Consequently, several pixel values of the background and target regions were respectively chosen to compose the characteristic vectors and input to the support vector machine, whose kernel function was set to being radial based function. Finally, the classifier obtained by the training step was applied to the thermal wave image and a binary image was obtained, which had been carried out the thermal wave image segmentation. Experimental results show that the proposed method can efficiently enhance the contrast between the background and target regions with a powerful noise retraining capability. Compared with the image segmentation method based on the hard threshold, the proposed procedure is of more benefit to the identification and evaluation of the defects and is valuable for the engineering application.
2014,
26: 101020.
doi: 10.11884/HPLPB201426.101020
Abstract:
The liquid splashing phenomenon occurs when the liquid is irradiated by laser, which consumes a large amount of liquid. The influence of splashing behavior on mechanical effects is researched in this paper. Aiming at the analyzing of mechanical effects in glycerol splashing, the flow field visualization and thrust measurement device are designed. The glycerol is ablated using the YAG laser. The splash part contained in the thrust curve can be obtained, and its proportion of contribution to the total impulse can be calculated by integrating the thrust curve over time. The experiment results show that large amounts of splash produce few impulses. Besides, the splashing behavior is the main reason for the low specific impulse of liquid as it wastes large amount of liquid. Finally, a new method for reducing splashing by ablating carbon-doped liquid is proposed. The experiment is to demonstrate the validity and capability of the proposed method. Key words: liquid ablation; laser propulsion; liquid; carbon-doped
The liquid splashing phenomenon occurs when the liquid is irradiated by laser, which consumes a large amount of liquid. The influence of splashing behavior on mechanical effects is researched in this paper. Aiming at the analyzing of mechanical effects in glycerol splashing, the flow field visualization and thrust measurement device are designed. The glycerol is ablated using the YAG laser. The splash part contained in the thrust curve can be obtained, and its proportion of contribution to the total impulse can be calculated by integrating the thrust curve over time. The experiment results show that large amounts of splash produce few impulses. Besides, the splashing behavior is the main reason for the low specific impulse of liquid as it wastes large amount of liquid. Finally, a new method for reducing splashing by ablating carbon-doped liquid is proposed. The experiment is to demonstrate the validity and capability of the proposed method. Key words: liquid ablation; laser propulsion; liquid; carbon-doped
2014,
26: 101021.
doi: 10.11884/HPLPB201426.101021
Abstract:
Advanced laser systems with high power, good beam quality and strong stability are always the research objectives. Volume Bragg diffractive elements recorded in photo-thermo-refractive glass have become one of the keys to the advanced laser technology development owing to their excellent optical property and diffractive ability. A detailed introduction to the applications and principles in the advanced laser technology with volume Bragg elements of different structures, including near-field filtering, spectral combining, semiconductor external-cavity spectral stabilization and chirped pulse broadening and compression, is presented. Key words:
Advanced laser systems with high power, good beam quality and strong stability are always the research objectives. Volume Bragg diffractive elements recorded in photo-thermo-refractive glass have become one of the keys to the advanced laser technology development owing to their excellent optical property and diffractive ability. A detailed introduction to the applications and principles in the advanced laser technology with volume Bragg elements of different structures, including near-field filtering, spectral combining, semiconductor external-cavity spectral stabilization and chirped pulse broadening and compression, is presented. Key words:
2014,
26: 101022.
doi: 10.11884/HPLPB201426.101022
Abstract:
A tracking mode is presented which reflects regional pixel spatial relationship combining with the core of the original algorithm based on the analysis of the principle of algorithm. Meanwhile the adaptability and the similarity measurement formula with two level decision strategy are adopted，and it extracted region characteristic to normalize values by the different right. If it does not meet the characteristics of observed value condition, the coarse-fine search to update the target model should be adopted. Experimental results show that the fluctuations characteristic observations meet the actual situation of the target area in the target tracking process, and the target in the case of abnormal fluctuations can be repositioned, thereby the tracking stability can be improved.
A tracking mode is presented which reflects regional pixel spatial relationship combining with the core of the original algorithm based on the analysis of the principle of algorithm. Meanwhile the adaptability and the similarity measurement formula with two level decision strategy are adopted，and it extracted region characteristic to normalize values by the different right. If it does not meet the characteristics of observed value condition, the coarse-fine search to update the target model should be adopted. Experimental results show that the fluctuations characteristic observations meet the actual situation of the target area in the target tracking process, and the target in the case of abnormal fluctuations can be repositioned, thereby the tracking stability can be improved.
2014,
26: 101023.
doi: 10.11884/HPLPB201426.101023
Abstract:
In the tiled-aperture coherent beam combining, the low filling factor will reduce the beam combining efficiency. To solve this problem, we proposed a filled-aperture coherent beam combining scheme based on the semi-transparent mirror. We studied the influences of the light intensity difference and wave-front phase error on the efficiency of the beam combination. The results show that it is not difficult to meet the tolerance requirement of light intensity difference and the wave-front phase error requirement in the filled-aperture coherent beam combining. When considering the single factor, if the single beam's intensity is three times larger than the others', the efficiency of the combining can reach 90%. And if the phase error is less than /5, the efficiency of the combining can reach 90.5%. We designed an experimental instrument to verify the feasibility of the filled-aperture coherent beam combining scheme. Experimental results show that, in the phase locked loop system, the output light intensity is very stable, and the efficiency of the combining can be more than 95%.
In the tiled-aperture coherent beam combining, the low filling factor will reduce the beam combining efficiency. To solve this problem, we proposed a filled-aperture coherent beam combining scheme based on the semi-transparent mirror. We studied the influences of the light intensity difference and wave-front phase error on the efficiency of the beam combination. The results show that it is not difficult to meet the tolerance requirement of light intensity difference and the wave-front phase error requirement in the filled-aperture coherent beam combining. When considering the single factor, if the single beam's intensity is three times larger than the others', the efficiency of the combining can reach 90%. And if the phase error is less than /5, the efficiency of the combining can reach 90.5%. We designed an experimental instrument to verify the feasibility of the filled-aperture coherent beam combining scheme. Experimental results show that, in the phase locked loop system, the output light intensity is very stable, and the efficiency of the combining can be more than 95%.
2014,
26: 101024.
doi: 10.11884/HPLPB201426.101024
Abstract:
The photoluminescence (PL) from microstructured silicon fabricated by femtosecond laser pulses in air was studied. In photoluminescence spectra measurements, the orange PL peak (603 nm) and the red PL band (near 680 nm) were observed even without annealing. The scanning electron microscope images (SEM) revealed that lots of nanoclusters and nanoparticles were deposited on the silicon surface. Fourier transform infrared spectroscopy (FT-IR) and energy dispersive spectroscopy (EDS) indicated that the oxygen element played an important role in the photoluminescence. The results confirmed that the red PL band and the orange PL peaks derived from the recombination of the quantum confinement effect and the suboxides (SiOx), respectively. Meanwhile, The oxygen content determined the orange PL intensity, and the size of nanoparticles decided the quantum confinement effect.
The photoluminescence (PL) from microstructured silicon fabricated by femtosecond laser pulses in air was studied. In photoluminescence spectra measurements, the orange PL peak (603 nm) and the red PL band (near 680 nm) were observed even without annealing. The scanning electron microscope images (SEM) revealed that lots of nanoclusters and nanoparticles were deposited on the silicon surface. Fourier transform infrared spectroscopy (FT-IR) and energy dispersive spectroscopy (EDS) indicated that the oxygen element played an important role in the photoluminescence. The results confirmed that the red PL band and the orange PL peaks derived from the recombination of the quantum confinement effect and the suboxides (SiOx), respectively. Meanwhile, The oxygen content determined the orange PL intensity, and the size of nanoparticles decided the quantum confinement effect.
Optimization design of stable and high quality optical parametric chriped pulse amplification system
2014,
26: 101025.
doi: 10.11884/HPLPB201426.101025
Abstract:
This paper proposes that in order to realize high-quality and stable output from an optical parametric chirped pulse amplification(OPCPA) system, the two nonlinear courses included in an OPCPA system must be optimized at the same time. These two nonlinear courses are the optical parametric amplifying (OPA) course and the second harmonic generation(SHG) course of the pump. In order to optimize the parametric amplifier, several kinds of physical models are set up and they will be used to solve different kinds of problems. The analyzing method is set up to get symmetrical output signal in x and y from an optical parametric amplifier. The method of making certain the length of the nonlinear crystal is also set up to get the most stable OPA output. In the study of the second harmonic generation course, mismatched SHG is put forward to get stable second harmonic pump. The study shows that mismatched SHG can not only improve the stability of the pump, but also decrease the modulation in near field and pulse waveform, thus improve the beam quality of the pump.
This paper proposes that in order to realize high-quality and stable output from an optical parametric chirped pulse amplification(OPCPA) system, the two nonlinear courses included in an OPCPA system must be optimized at the same time. These two nonlinear courses are the optical parametric amplifying (OPA) course and the second harmonic generation(SHG) course of the pump. In order to optimize the parametric amplifier, several kinds of physical models are set up and they will be used to solve different kinds of problems. The analyzing method is set up to get symmetrical output signal in x and y from an optical parametric amplifier. The method of making certain the length of the nonlinear crystal is also set up to get the most stable OPA output. In the study of the second harmonic generation course, mismatched SHG is put forward to get stable second harmonic pump. The study shows that mismatched SHG can not only improve the stability of the pump, but also decrease the modulation in near field and pulse waveform, thus improve the beam quality of the pump.
2014,
26: 102001.
doi: 10.11884/HPLPB201426.102001
Abstract:
According to the operation mode and target chamber structure of SG-Ⅲ laser facility, a single frame X-ray framing camera system with double channels is successfully designed. The imaging system mainly consists of a pin-hole camera, a gated MCP framing camera and a scientific grade visible light CCD. The pin-hole diameter is 10 m, the and magnification is 5. The single frame format of the system is 13 mm36 mm, and exposure time is adjustable from 0.5 ns to 10 ns. Performance evaluation is conducted on SG-Ⅲ laser facility, and the results show that the system completely meets the requirement of SG-Ⅲ laser facility. Compared to the traditional X ray imaging system, which mainly consists of pin-hole camera and X-ray CCD, the signal-to-noise ratio and spatial resolution are better.
According to the operation mode and target chamber structure of SG-Ⅲ laser facility, a single frame X-ray framing camera system with double channels is successfully designed. The imaging system mainly consists of a pin-hole camera, a gated MCP framing camera and a scientific grade visible light CCD. The pin-hole diameter is 10 m, the and magnification is 5. The single frame format of the system is 13 mm36 mm, and exposure time is adjustable from 0.5 ns to 10 ns. Performance evaluation is conducted on SG-Ⅲ laser facility, and the results show that the system completely meets the requirement of SG-Ⅲ laser facility. Compared to the traditional X ray imaging system, which mainly consists of pin-hole camera and X-ray CCD, the signal-to-noise ratio and spatial resolution are better.
2014,
26: 102002.
doi: 10.11884/HPLPB201426.102002
Abstract:
Based on the structural and material characteristics and requirements of the accuracy of quasi-spherical load in the process of assembly, the study on the assembly process of microspheres and wire array was carried out. And according to the assembly process of wire array, we finished the assembly of wire array with 8 mm diameter, and tungsten wire with 10 m diameter; the assembly of a micro ball with 3 mm diameter and glass fiber with 200 m diameter was performed on a foam microsphere micro-assembly system. Quasi-spherical load was successfully applied in physical tests of quasi-spherical load, and satisfactory results were achieved. It is expected to play a greater role in inertial confinement fusion (ICF) and physical tests of the quasi-spherical load in the future.
Based on the structural and material characteristics and requirements of the accuracy of quasi-spherical load in the process of assembly, the study on the assembly process of microspheres and wire array was carried out. And according to the assembly process of wire array, we finished the assembly of wire array with 8 mm diameter, and tungsten wire with 10 m diameter; the assembly of a micro ball with 3 mm diameter and glass fiber with 200 m diameter was performed on a foam microsphere micro-assembly system. Quasi-spherical load was successfully applied in physical tests of quasi-spherical load, and satisfactory results were achieved. It is expected to play a greater role in inertial confinement fusion (ICF) and physical tests of the quasi-spherical load in the future.
2014,
26: 102003.
doi: 10.11884/HPLPB201426.102003
Abstract:
The ICF system has strict requirements on the focal spot size and intensity distribution uniformity during the design process of continuous phase plate(CPP). The relationship between CPPs surface and the light intensity uniformity of far field focal spot is studied, and the influences of CPPs surface modulation depth on the size of focal spot are analyzed and calculated theoretically. Results show that the growth of the radius of focal spot is in direct proportion to the increase of the surface modulation depth of CPP. For the sake of random behavior of CPP, the difference of far field characteristics between CPPs is compared, and the influences of modulation depth on the peak-valley and root mean square value of light intensity are studied, which shows that the differently designed CPP has different behavior in far field. When the modulation depth is around 5 to 15, the focal spot could have a relatively low peak-valley and low root mean square value, which means that the CPP is in good smoothing performance.
The ICF system has strict requirements on the focal spot size and intensity distribution uniformity during the design process of continuous phase plate(CPP). The relationship between CPPs surface and the light intensity uniformity of far field focal spot is studied, and the influences of CPPs surface modulation depth on the size of focal spot are analyzed and calculated theoretically. Results show that the growth of the radius of focal spot is in direct proportion to the increase of the surface modulation depth of CPP. For the sake of random behavior of CPP, the difference of far field characteristics between CPPs is compared, and the influences of modulation depth on the peak-valley and root mean square value of light intensity are studied, which shows that the differently designed CPP has different behavior in far field. When the modulation depth is around 5 to 15, the focal spot could have a relatively low peak-valley and low root mean square value, which means that the CPP is in good smoothing performance.
2014,
26: 102004.
doi: 10.11884/HPLPB201426.102004
Abstract:
The glow discharge polymer (GDP) films with the thickness of about 7 m were deposited. Under the protection of argon, the GDP films were heated to 300 ℃ for 6 h, 10 h, 24 h. The influence of holding time on the structure of GDP films was characterized by FT-IR. The surface roughness of GDP films after different holding time was investigated by white light interferometer. The hardness and modulus of GDP films were measured by nanoindentation. It is found that while the holding time increases, the relative content of CH3 decreases, the cross-linking degree of carbon network increases, and the surface roughness of GDP films reduces. The hardness and modulus decreases firstly and then increases with the increasing holding time.
The glow discharge polymer (GDP) films with the thickness of about 7 m were deposited. Under the protection of argon, the GDP films were heated to 300 ℃ for 6 h, 10 h, 24 h. The influence of holding time on the structure of GDP films was characterized by FT-IR. The surface roughness of GDP films after different holding time was investigated by white light interferometer. The hardness and modulus of GDP films were measured by nanoindentation. It is found that while the holding time increases, the relative content of CH3 decreases, the cross-linking degree of carbon network increases, and the surface roughness of GDP films reduces. The hardness and modulus decreases firstly and then increases with the increasing holding time.
2014,
26: 102005.
doi: 10.11884/HPLPB201426.102005
Abstract:
With the help of radiation hydrodynamic code Flash, we simulated the ablation process of a small focal-spot nanosecond laser irradiation on an aluminum planar target. The irradiating laser has a focal spot radius of 25 m and maximum intensity of about 1013 W/cm2 with wavelength of 532 nm. In our simulations, it is observed that electron density in the laser channel is relatively lower than the ambient one in some coronal region. This phenomenon is found to be sensitive to the electron heat conduction model. By comparing simulation results with our experimental electron density profiles, flux limit factor of 0.08 is then determined in our simulation. The annular jet also occurs in our simulations and experiments. The mechanism of annular jet formation is analyzed and discussed, which is mainly related to the radiative cooling.
With the help of radiation hydrodynamic code Flash, we simulated the ablation process of a small focal-spot nanosecond laser irradiation on an aluminum planar target. The irradiating laser has a focal spot radius of 25 m and maximum intensity of about 1013 W/cm2 with wavelength of 532 nm. In our simulations, it is observed that electron density in the laser channel is relatively lower than the ambient one in some coronal region. This phenomenon is found to be sensitive to the electron heat conduction model. By comparing simulation results with our experimental electron density profiles, flux limit factor of 0.08 is then determined in our simulation. The annular jet also occurs in our simulations and experiments. The mechanism of annular jet formation is analyzed and discussed, which is mainly related to the radiative cooling.
2014,
26: 102006.
doi: 10.11884/HPLPB201426.102006
Abstract:
Theoretical calculation of X-ray three-dimensional diffraction optical path was presented for hard X-ray transmission curved crystal spectrometer. One application of this theory was to study the energy calibration, which was achieved traditionally by fitting the K absorption edges of filters or the characteristic peaks of experimental spectra. Obvious error was found in the low energy region of the calibrated spectrum, by taking into account the misalignment of spectrometer or the assembled error of detector. In order to avoid the calibration error and calibrate the spectrometer only by one filter, a new method for energy calibration was presented and verified by experimental measurement of an Ag anode X-ray source.
Theoretical calculation of X-ray three-dimensional diffraction optical path was presented for hard X-ray transmission curved crystal spectrometer. One application of this theory was to study the energy calibration, which was achieved traditionally by fitting the K absorption edges of filters or the characteristic peaks of experimental spectra. Obvious error was found in the low energy region of the calibrated spectrum, by taking into account the misalignment of spectrometer or the assembled error of detector. In order to avoid the calibration error and calibrate the spectrometer only by one filter, a new method for energy calibration was presented and verified by experimental measurement of an Ag anode X-ray source.
2014,
26: 102007.
doi: 10.11884/HPLPB201426.102007
Abstract:
Based on the analytical solution of the dependence of phase matching angle on the crystal temperature, we illustrate the thermo-optic physical mechanism of temperature influence on the frequency conversion. The thermal sensitivity of the doubler and tripler crystals are numerically simulated respectively. Due to such sensitivity discrepancy among various crystals, the phase matching angle curve regarding the crystal temperature variation in our laser facility is obtained in experiment. The influence of PM angular detune on frequency conversion is theoretically analyzed under different input intensities, which is demonstrated by the conversion efficiency decline induced by temperature variation. According to the thermal sensitivity parameter obtained in experiments, we compensate the conversion efficiency with the crystal angle following, resulting in stable output of third harmonic energy.
Based on the analytical solution of the dependence of phase matching angle on the crystal temperature, we illustrate the thermo-optic physical mechanism of temperature influence on the frequency conversion. The thermal sensitivity of the doubler and tripler crystals are numerically simulated respectively. Due to such sensitivity discrepancy among various crystals, the phase matching angle curve regarding the crystal temperature variation in our laser facility is obtained in experiment. The influence of PM angular detune on frequency conversion is theoretically analyzed under different input intensities, which is demonstrated by the conversion efficiency decline induced by temperature variation. According to the thermal sensitivity parameter obtained in experiments, we compensate the conversion efficiency with the crystal angle following, resulting in stable output of third harmonic energy.
2014,
26: 102008.
doi: 10.11884/HPLPB201426.102008
Abstract:
The beam transport system which is an important composition of laser facility target area provides guidance and collimation for laser beams. In this paper, the structural design of the beam transport system of SG-Ⅲ target area is introduced. The main performance of the beam transport system consists the stability, accuracy and cleanliness. In order to meet the stringent stability requirement, the dynamic stability of structure was improved and a new stability analytical method was proposed. The requirement of exact adjusting and fast online replacement was assured by the design of the Line Replaceable Units, the kinematic mounts structure, and the low-stress holding of the mirror mounts. Simultaneously, the clean conception was established in design, fabrication, and operation. The testing results of the installed part of the beam transport system indicate that the structural design satisfies the performance requirements of facility.
The beam transport system which is an important composition of laser facility target area provides guidance and collimation for laser beams. In this paper, the structural design of the beam transport system of SG-Ⅲ target area is introduced. The main performance of the beam transport system consists the stability, accuracy and cleanliness. In order to meet the stringent stability requirement, the dynamic stability of structure was improved and a new stability analytical method was proposed. The requirement of exact adjusting and fast online replacement was assured by the design of the Line Replaceable Units, the kinematic mounts structure, and the low-stress holding of the mirror mounts. Simultaneously, the clean conception was established in design, fabrication, and operation. The testing results of the installed part of the beam transport system indicate that the structural design satisfies the performance requirements of facility.
2014,
26: 103001.
doi: 10.11884/HPLPB201426.103001
Abstract:
Electric field response of silicon detecting chip within circular waveguide to several usual electromagnetic wave modes in X-band is studied numerically and theoretically. Based on the hot carrier effect under high electric field, a silicon detecting structure is proposed to measure the high power microwave (HPM) pulse within circular waveguide in real time. Then cross-sectional electric field distributions are simulated and analyzed when HPMs with TE11 mode (with two orthogonal polarization directions), TM01 mode and TE01 mode are applied respectively by using the three dimensional parallel finite-difference time-domain (FDTD) method. Results of different modes show that the transverse electric fields are all dominated by radial components, and the amplitude ratios between radial and angular components are probably 10. The standing wave ratio of transverse electric field is no more than 1.3. At last, the sensitivities of the detecting structure for different modes in circular waveguide are derived. Theoretical analysis indicates that the maximum enduring power of the detecting structure, which can reach as high as 422 MW, is dependent upon modes, and its response time is in the picosecond-level. It attests the feasibility of on-line measurements of X-band HPM pulses employing the designed detecting structure
Electric field response of silicon detecting chip within circular waveguide to several usual electromagnetic wave modes in X-band is studied numerically and theoretically. Based on the hot carrier effect under high electric field, a silicon detecting structure is proposed to measure the high power microwave (HPM) pulse within circular waveguide in real time. Then cross-sectional electric field distributions are simulated and analyzed when HPMs with TE11 mode (with two orthogonal polarization directions), TM01 mode and TE01 mode are applied respectively by using the three dimensional parallel finite-difference time-domain (FDTD) method. Results of different modes show that the transverse electric fields are all dominated by radial components, and the amplitude ratios between radial and angular components are probably 10. The standing wave ratio of transverse electric field is no more than 1.3. At last, the sensitivities of the detecting structure for different modes in circular waveguide are derived. Theoretical analysis indicates that the maximum enduring power of the detecting structure, which can reach as high as 422 MW, is dependent upon modes, and its response time is in the picosecond-level. It attests the feasibility of on-line measurements of X-band HPM pulses employing the designed detecting structure
2014,
26: 103002.
doi: 10.11884/HPLPB201426.103002
Abstract:
As the efficiencies of the traditional high power solid state Si microwave source and GaAs microwave source are low and their performances are poor at high temperature, we have developed a 1.2 kW C-band all solid state high efficiency GaN microwave source by using the low loss coaxial waveguide spatial power combining technique which utilizes GaN units power amplifier module integration. The experimental result shows that the efficiency of the GaN microwave source is high and it can safely and reliably operate at high temperature. A single C-band GaN power amplifier module unit integrates a 6-bit phase shifter with a phase shift precision of 5.6, a gain of 35 dB, and an output power greater than 31 W. The continuous output power of the microwave source is 1.2 kW, the total efficiency is 30%, the harmonic suppression is -54.8 dBc, the stray is -63.69 dBc and the phase noise is -94.03 dBc/Hz@1kHz.
As the efficiencies of the traditional high power solid state Si microwave source and GaAs microwave source are low and their performances are poor at high temperature, we have developed a 1.2 kW C-band all solid state high efficiency GaN microwave source by using the low loss coaxial waveguide spatial power combining technique which utilizes GaN units power amplifier module integration. The experimental result shows that the efficiency of the GaN microwave source is high and it can safely and reliably operate at high temperature. A single C-band GaN power amplifier module unit integrates a 6-bit phase shifter with a phase shift precision of 5.6, a gain of 35 dB, and an output power greater than 31 W. The continuous output power of the microwave source is 1.2 kW, the total efficiency is 30%, the harmonic suppression is -54.8 dBc, the stray is -63.69 dBc and the phase noise is -94.03 dBc/Hz@1kHz.
2014,
26: 103003.
doi: 10.11884/HPLPB201426.103003
Abstract:
The distortionless transmission of the signal through the transmission line is the prerequisite to ascertain the waveform and value of the electromagnetic field under test accurately. In consideration of the bandwidth, power capacity, loss, shielding efficiency and size, the coaxial cable is often used in the UWB measurement system. It is indicated in this paper that the single coaxial cable can produce interference to the transmission signal and the reason of the interference is explained. The result of the computation by a numerical method testifies that the interference does exist and can cause aberration of the signal when one coaxial cable is used as the transmission line. It is put forward that the interference can be eliminated effectively by differential transmission using two coaxial grounded cables. The prominent suppressing effect of the transmission method is certified contrastively by simulation. A dipole with the two coaxial feeder is fabricated and tested. The experiment shows that the single coaxial cable caused obvious interference and the interference was eliminated by the differential operation of the output voltages from the two coaxial cables.
The distortionless transmission of the signal through the transmission line is the prerequisite to ascertain the waveform and value of the electromagnetic field under test accurately. In consideration of the bandwidth, power capacity, loss, shielding efficiency and size, the coaxial cable is often used in the UWB measurement system. It is indicated in this paper that the single coaxial cable can produce interference to the transmission signal and the reason of the interference is explained. The result of the computation by a numerical method testifies that the interference does exist and can cause aberration of the signal when one coaxial cable is used as the transmission line. It is put forward that the interference can be eliminated effectively by differential transmission using two coaxial grounded cables. The prominent suppressing effect of the transmission method is certified contrastively by simulation. A dipole with the two coaxial feeder is fabricated and tested. The experiment shows that the single coaxial cable caused obvious interference and the interference was eliminated by the differential operation of the output voltages from the two coaxial cables.
2014,
26: 104001.
doi: 10.11884/HPLPB201426.104001
Abstract:
Compared to X-ray radiography, the proton radiography is more suitable for hydro-test experiment because of higher penetration of high-energy proton, and it is easier to gain better result with less uncertainty. The progresses of the proton radiography to form the shadow information inside the object are more complicated. In order to conveniently investigate the proton radiography processes and their characteristics, an empiric formula for high-energy proton radiography is inferred based on the protons transportation during the radiographic process. The formula contains the terms of elastic scatter and quasi-elastic scatter with multiple scatter process. The validity of the formula is verified by comparing the analytic result from the formula to the result of MC simulation. The results show that the same results are obtained by formula calculation and MC simulation with the Gaussian scatter type approximation, it is about 3%-5% below the more precise result gained by the MC simulation with black-disk model. The research result implies that the formula can take the place of MC simulation to discover the law of the proton radiography and to design the system in some extent.
Compared to X-ray radiography, the proton radiography is more suitable for hydro-test experiment because of higher penetration of high-energy proton, and it is easier to gain better result with less uncertainty. The progresses of the proton radiography to form the shadow information inside the object are more complicated. In order to conveniently investigate the proton radiography processes and their characteristics, an empiric formula for high-energy proton radiography is inferred based on the protons transportation during the radiographic process. The formula contains the terms of elastic scatter and quasi-elastic scatter with multiple scatter process. The validity of the formula is verified by comparing the analytic result from the formula to the result of MC simulation. The results show that the same results are obtained by formula calculation and MC simulation with the Gaussian scatter type approximation, it is about 3%-5% below the more precise result gained by the MC simulation with black-disk model. The research result implies that the formula can take the place of MC simulation to discover the law of the proton radiography and to design the system in some extent.
2014,
26: 104002.
doi: 10.11884/HPLPB201426.104002
Abstract:
To solve the problem of achieving the large diameter amorphous metallic film first mirrors, based on the research of Co61.2B26.2Si7.8Ta4.8 metallic glass, splicing the amorphous glass bulks together as the target and using bulk amorphous glass as the sputtering material, by unbalanced magnetron sputtering coating method, the Co61.2B26.2Si7.8Ta4.8 amorphous metallic film first mirrors was realized. The research results show that with designing the composition and synthesis target-material, amorphous film first mirrors having the same optical properties with BMGs can be achieved; with coating Cr on the amorphous film, the spectral reflectivity of amorphous metallic film first mirrors in visible spectrum can be further increased.
To solve the problem of achieving the large diameter amorphous metallic film first mirrors, based on the research of Co61.2B26.2Si7.8Ta4.8 metallic glass, splicing the amorphous glass bulks together as the target and using bulk amorphous glass as the sputtering material, by unbalanced magnetron sputtering coating method, the Co61.2B26.2Si7.8Ta4.8 amorphous metallic film first mirrors was realized. The research results show that with designing the composition and synthesis target-material, amorphous film first mirrors having the same optical properties with BMGs can be achieved; with coating Cr on the amorphous film, the spectral reflectivity of amorphous metallic film first mirrors in visible spectrum can be further increased.
2014,
26: 104003.
doi: 10.11884/HPLPB201426.104003
Abstract:
Neutral beam injection (NBI) is an important method of plasma heating and plasma current driving for magnetic confinement fusion device. A distributed control system is designed in this paper according to experimental operation characteristics of NBI on Experimental Advanced Superconducting Tokamak (EAST). The NBI control system based on network technology, classified according to control level, consists of remote monitoring layer, server control layer and field control layer. The three-layer control systematic architecture is easy for extending system functions and upgrading devices. Both ion sources of one NBI beam line are designed to operate independently, which lays a foundation for developing control system of the second beam line on EAST. Experimental results demonstrate that the visualization and automation of NBI experimental operations are successfully implemented by remote monitoring, interlock protection, and data processing.
Neutral beam injection (NBI) is an important method of plasma heating and plasma current driving for magnetic confinement fusion device. A distributed control system is designed in this paper according to experimental operation characteristics of NBI on Experimental Advanced Superconducting Tokamak (EAST). The NBI control system based on network technology, classified according to control level, consists of remote monitoring layer, server control layer and field control layer. The three-layer control systematic architecture is easy for extending system functions and upgrading devices. Both ion sources of one NBI beam line are designed to operate independently, which lays a foundation for developing control system of the second beam line on EAST. Experimental results demonstrate that the visualization and automation of NBI experimental operations are successfully implemented by remote monitoring, interlock protection, and data processing.
2014,
26: 104004.
doi: 10.11884/HPLPB201426.104004
Abstract:
The typical conventional CT system employs the digital integrating sensor, for which it is difficult to identify attenuation characteristics of different energy X-ray. This paper focuses on X-ray spectral imaging technology based on MARS X-ray spectral CT system. We scanned some singular element materials and a multi-material phantom with different energy X-ray bins, obtained some material K-edge characteristic curves, and reconstructed CT images of multi-material phantom. By means of CT images based on material K-edge characteristics, we can discriminate different materials or recognize more attenuation information of different materials. Compared to conventional X-ray CT technology, X-ray spectral CT can provide much richer attenuation information.
The typical conventional CT system employs the digital integrating sensor, for which it is difficult to identify attenuation characteristics of different energy X-ray. This paper focuses on X-ray spectral imaging technology based on MARS X-ray spectral CT system. We scanned some singular element materials and a multi-material phantom with different energy X-ray bins, obtained some material K-edge characteristic curves, and reconstructed CT images of multi-material phantom. By means of CT images based on material K-edge characteristics, we can discriminate different materials or recognize more attenuation information of different materials. Compared to conventional X-ray CT technology, X-ray spectral CT can provide much richer attenuation information.
2014,
26: 105001.
doi: 10.11884/HPLPB201426.105001
Abstract:
This paper builds up a circuit model of the switch synchronously discharge in the FLTD stage and a circuit simulation model of the FLTD stage. The switch in FLTD simulation model integrates the switch controlled by voltage and self-break switch. The FLTD stage simulation model can simulate stage output influence by switch discharge jitter and bricks discharge each other. The simulation model has been validated by the experiment result of a 14-brick FLTD stage. The influence of the 20-brick FLTD stage output current peak and rise-time with switches discharge synchronously have been simulated by the circuit simulation model of the FLTD. The simulation results indicate that the stage output influence is insignificant when the jitter of switch is less than 5 ns.
This paper builds up a circuit model of the switch synchronously discharge in the FLTD stage and a circuit simulation model of the FLTD stage. The switch in FLTD simulation model integrates the switch controlled by voltage and self-break switch. The FLTD stage simulation model can simulate stage output influence by switch discharge jitter and bricks discharge each other. The simulation model has been validated by the experiment result of a 14-brick FLTD stage. The influence of the 20-brick FLTD stage output current peak and rise-time with switches discharge synchronously have been simulated by the circuit simulation model of the FLTD. The simulation results indicate that the stage output influence is insignificant when the jitter of switch is less than 5 ns.
2014,
26: 105002.
doi: 10.11884/HPLPB201426.105002
Abstract:
In this paper, a plasma-jet triggered gas switch was designed to form multichannel discharge. Multiple micro-incentive chambers were embedded in the trigger electrode to form multichannel plasma jet. The influences of trigger circuit, energy and polarity on the multichannel plasma jet were studied. The relationship between discharge channel numbers of every spark gap and working coefficient was also investigated at two working modes. Experimental results show that the multichannel discharge characteristics of trigger electrode are better when the upper plate of the trigger electrode is directly grounded. High trigger energy, negative polarity and low gas pressure are conducive to the formation of multichannel plasma jet. The plasma jet triggering can effectively induce multichannel discharge of gas switch. The discharge channel number increases with the increase of working coefficient.
In this paper, a plasma-jet triggered gas switch was designed to form multichannel discharge. Multiple micro-incentive chambers were embedded in the trigger electrode to form multichannel plasma jet. The influences of trigger circuit, energy and polarity on the multichannel plasma jet were studied. The relationship between discharge channel numbers of every spark gap and working coefficient was also investigated at two working modes. Experimental results show that the multichannel discharge characteristics of trigger electrode are better when the upper plate of the trigger electrode is directly grounded. High trigger energy, negative polarity and low gas pressure are conducive to the formation of multichannel plasma jet. The plasma jet triggering can effectively induce multichannel discharge of gas switch. The discharge channel number increases with the increase of working coefficient.
2014,
26: 105003.
doi: 10.11884/HPLPB201426.105003
Abstract:
A coilgun design code is programmed according to the formulas describing the inductive coupling between the thrust coils and the armature, the dynamic response of the armature, and the ohmic heating in the thrust coils and armature. The algorithms determining the operation status of the driven pulse forming network are presented. The convergence of the code is analyzed. The maximum time-step and mesh size of the armature are dependent on the rise time of the driven pulse current. The code is validated by comparing the simulated results with the experimental ones. The calculated coil current wave is in agreement with the experimental results. However, the calculated velocity is higher than the measured one about 6.5%. The convergence and validation of the code indicate that it can be used for the primary design for a coilgun system.
A coilgun design code is programmed according to the formulas describing the inductive coupling between the thrust coils and the armature, the dynamic response of the armature, and the ohmic heating in the thrust coils and armature. The algorithms determining the operation status of the driven pulse forming network are presented. The convergence of the code is analyzed. The maximum time-step and mesh size of the armature are dependent on the rise time of the driven pulse current. The code is validated by comparing the simulated results with the experimental ones. The calculated coil current wave is in agreement with the experimental results. However, the calculated velocity is higher than the measured one about 6.5%. The convergence and validation of the code indicate that it can be used for the primary design for a coilgun system.
2014,
26: 105004.
doi: 10.11884/HPLPB201426.105004
Abstract:
High-voltage hold-off insulator stack is the most crucial component in pulsed power system while applying pulse forming line and pulse compress technology to generating several MV voltage output. The voltage potential distribution mechanism of several radial insulator stacks was studied. An optimized insulator stack configuration was acquired based on static electric field analysis program, and designing method of radial resistor is proposed. Results showed that much uniform electric field distribution of insulator stack was obtained by using grading rings together with the electrical contact of grading rings and radial resistor, the radial resistor becomes the key to the performance of insulator stack. With an applied voltage of 4.5 MV and a duration of 100 ns, the electric field of triple point and Martin were about 25 kV/cm and 120 kV/cm respectively, lower than the theoretical flashover value.
High-voltage hold-off insulator stack is the most crucial component in pulsed power system while applying pulse forming line and pulse compress technology to generating several MV voltage output. The voltage potential distribution mechanism of several radial insulator stacks was studied. An optimized insulator stack configuration was acquired based on static electric field analysis program, and designing method of radial resistor is proposed. Results showed that much uniform electric field distribution of insulator stack was obtained by using grading rings together with the electrical contact of grading rings and radial resistor, the radial resistor becomes the key to the performance of insulator stack. With an applied voltage of 4.5 MV and a duration of 100 ns, the electric field of triple point and Martin were about 25 kV/cm and 120 kV/cm respectively, lower than the theoretical flashover value.
2014,
26: 105005.
doi: 10.11884/HPLPB201426.105005
Abstract:
Gas switch is one of the key components widely used in pulsed power devices. Research and design of high power, high performance gas switch have important significance. Speed up the pulse front is an important part of switch technology research. This paper analyzes the distribution law of gas switch breakdown channel. The gas switch fully sophisticated, switch breakdown and the breakdown channel will be relatively stable. When the breakdown field is low, reducing the switch gap will be beneficial for pulse sharpening. When the breakdown field is large (greater than 180 kV/cm), switch gap (inductor) has little influence on front edge of output pulse. Breakdown of gas switch is the key factor to influence the forefront of the output pulse. Research results show that increasing the breakdown field strength is an effective way to sharpening the pulse edge up.
Gas switch is one of the key components widely used in pulsed power devices. Research and design of high power, high performance gas switch have important significance. Speed up the pulse front is an important part of switch technology research. This paper analyzes the distribution law of gas switch breakdown channel. The gas switch fully sophisticated, switch breakdown and the breakdown channel will be relatively stable. When the breakdown field is low, reducing the switch gap will be beneficial for pulse sharpening. When the breakdown field is large (greater than 180 kV/cm), switch gap (inductor) has little influence on front edge of output pulse. Breakdown of gas switch is the key factor to influence the forefront of the output pulse. Research results show that increasing the breakdown field strength is an effective way to sharpening the pulse edge up.
2014,
26: 105101.
doi: 10.11884/HPLPB201426.105101
Abstract:
A new prototype system for bunch-by-bunch beam position measurement has been designed and built to monitor and analyse the beam loss in the Beijing Electron-Positron ColliderⅡ(BEPCⅡ) storage ring. The fast ADC is used to sample the analog signals from the beam position monitor, then the digital signal is processed further using programmable gate array (FPGA). The beam information can be obtained by means of bunch-by-bunch, such as bunch position, bunch current and bunch tune. Based on system monitoring and data analysis for long terms, as well as the dedicated machine experiments, its relatively clear for operators to understand some trip events, especially the beam loss caused by the high-frequency cavity trip, tune drift and multiple bunch instability. The study proves that the system is very useful for the operation of accelerator.
A new prototype system for bunch-by-bunch beam position measurement has been designed and built to monitor and analyse the beam loss in the Beijing Electron-Positron ColliderⅡ(BEPCⅡ) storage ring. The fast ADC is used to sample the analog signals from the beam position monitor, then the digital signal is processed further using programmable gate array (FPGA). The beam information can be obtained by means of bunch-by-bunch, such as bunch position, bunch current and bunch tune. Based on system monitoring and data analysis for long terms, as well as the dedicated machine experiments, its relatively clear for operators to understand some trip events, especially the beam loss caused by the high-frequency cavity trip, tune drift and multiple bunch instability. The study proves that the system is very useful for the operation of accelerator.
2014,
26: 105102.
doi: 10.11884/HPLPB201426.105102
Abstract:
The solid-state pulse forming lines (PFL) of CaO-TiO2-Al2O3 composite ceramic are designed and manufactured for the dielectric wall accelerator. The PFLs geometric parameters are 300 mm long, 15 mm wide, 1mm thick of ceramic dielectric and 280 mm long, 2 mm wide of silver electrode. The electrical parameters are 23.5 relative dielectric constant, about 26 characteristic impedance, 4.5 ns characteristic time, 20 kV/mm and 25 kV/mm breakdown field strength for DC and pulsed high voltage. The solid-state PFLs design gives consideration to operating requirement of photoconductive semiconductor switches (PCSS), design parameters of high gradient insulator, charged particle beams transport and accelerators structural design. Combined with the PCSS, the experimental research of solid-state Blumlein PFL is performed. The solid-state Blumlein PFL could output about 23 kV pulsed voltage on the load under about 25 kV pulsed voltage.
The solid-state pulse forming lines (PFL) of CaO-TiO2-Al2O3 composite ceramic are designed and manufactured for the dielectric wall accelerator. The PFLs geometric parameters are 300 mm long, 15 mm wide, 1mm thick of ceramic dielectric and 280 mm long, 2 mm wide of silver electrode. The electrical parameters are 23.5 relative dielectric constant, about 26 characteristic impedance, 4.5 ns characteristic time, 20 kV/mm and 25 kV/mm breakdown field strength for DC and pulsed high voltage. The solid-state PFLs design gives consideration to operating requirement of photoconductive semiconductor switches (PCSS), design parameters of high gradient insulator, charged particle beams transport and accelerators structural design. Combined with the PCSS, the experimental research of solid-state Blumlein PFL is performed. The solid-state Blumlein PFL could output about 23 kV pulsed voltage on the load under about 25 kV pulsed voltage.
2014,
26: 105103.
doi: 10.11884/HPLPB201426.105103
Abstract:
In order to extend the life span of the proton beam target for the accelerator driven sub-critical system (ADS), a design scheme based on the step field magnets (SFMs) was used to expand the proton beams both along horizontal and vertical directions. 3D finite element method was used to simulate one single SFM and the two adjacent SFMs to get the expected step field. With the aid of the 3D field data, the effects on proton beams were investigated with beam tracking. Furthermore, a kind of compact SFM providing more obvious step field was illustrated.
In order to extend the life span of the proton beam target for the accelerator driven sub-critical system (ADS), a design scheme based on the step field magnets (SFMs) was used to expand the proton beams both along horizontal and vertical directions. 3D finite element method was used to simulate one single SFM and the two adjacent SFMs to get the expected step field. With the aid of the 3D field data, the effects on proton beams were investigated with beam tracking. Furthermore, a kind of compact SFM providing more obvious step field was illustrated.
2014,
26: 105104.
doi: 10.11884/HPLPB201426.105104
Abstract:
According to the physical requirements and the actual situation of Positron Emission Tomography (PET) cyclotrons at Institute of Modern Physics, Chinese Academy of Sciences (IMP, CAS), a new compact RF cavity with a quarter wave resonator structure and a profiled cover was designed with high accelerated e-field gradient. Additionally, a special dual tuning structure with a short-plate and a movable capacitor plate was designed to meet the requirements of complicated tuning operation mode. The simulated results from Microwave Studio (CST) showed that the design obtained a high quality factor and reached a rated accelerated voltage. The electro-magnetic analysis was carried out, and the power loss tolerance and the thermal distribution were calculated. A prototype cavity was fabricated and measured in January, 2013, and the tested results indicated that the accelerated voltage was higher than 50 kV and the frequency stability was 10-6/d, both of them reached the original design specification. This proves that the measured results agree well with the simulated ones. All detailed simulations and measurements were analyzed and discussed.
According to the physical requirements and the actual situation of Positron Emission Tomography (PET) cyclotrons at Institute of Modern Physics, Chinese Academy of Sciences (IMP, CAS), a new compact RF cavity with a quarter wave resonator structure and a profiled cover was designed with high accelerated e-field gradient. Additionally, a special dual tuning structure with a short-plate and a movable capacitor plate was designed to meet the requirements of complicated tuning operation mode. The simulated results from Microwave Studio (CST) showed that the design obtained a high quality factor and reached a rated accelerated voltage. The electro-magnetic analysis was carried out, and the power loss tolerance and the thermal distribution were calculated. A prototype cavity was fabricated and measured in January, 2013, and the tested results indicated that the accelerated voltage was higher than 50 kV and the frequency stability was 10-6/d, both of them reached the original design specification. This proves that the measured results agree well with the simulated ones. All detailed simulations and measurements were analyzed and discussed.
2014,
26: 109001.
doi: 10.11884/HPLPB201426.109001
Abstract:
The high-energy Nd: YAG laser YLSS-M60U was adopted for laser shock processing on K403/K3 cast superalloy test specimen from pressure-turbine blade materials of a certain type of engine. The processing parameters are: laser energy 3 J, spot diameter 2.6 mm, laser pulse 20 ns, laser wave length 1064 nm. An aluminium foil was used as the protection coating, along with water as the restraint layer, the overlap rate reached 50% after 3 times of shocking. The high-cycle fatigue (HCF) test was conducted under the room temperature at stress level of 420 MPa as well as the SEM observation and XRD (x-Ray diffraction) analysis after laser shock processing. The study shows that the leading reasons for improving the fatigue property of metal involve that the fatigue life of the test specimen was 2.4 times longer than the original after laser shock processing, the strong shock waves plastically deform the metal with high-strain rate and generate much larger and deeper residual compressive stress.
The high-energy Nd: YAG laser YLSS-M60U was adopted for laser shock processing on K403/K3 cast superalloy test specimen from pressure-turbine blade materials of a certain type of engine. The processing parameters are: laser energy 3 J, spot diameter 2.6 mm, laser pulse 20 ns, laser wave length 1064 nm. An aluminium foil was used as the protection coating, along with water as the restraint layer, the overlap rate reached 50% after 3 times of shocking. The high-cycle fatigue (HCF) test was conducted under the room temperature at stress level of 420 MPa as well as the SEM observation and XRD (x-Ray diffraction) analysis after laser shock processing. The study shows that the leading reasons for improving the fatigue property of metal involve that the fatigue life of the test specimen was 2.4 times longer than the original after laser shock processing, the strong shock waves plastically deform the metal with high-strain rate and generate much larger and deeper residual compressive stress.
2014,
26: 109002.
doi: 10.11884/HPLPB201426.109002
Abstract:
To analyze the dynamic response of the back of AZ31B magnesium alloy sheet to laser shock wave, the laser induced shockwave was measured by PVDF patch sensors and a digital oscilloscope and then piezoelectric waveforms were got. The propagation law of elastic and plastic wave structure was studied combined with shock wave propagation characteristics. The results indicate that the laser induced dynamic response of the material is transient. The time of elastic precursors wave and plastic load wave propagate to the back of the sheet is reflected by the piezoelectric waveforms. Which corresponds to the time of the theory. The waveform amplitude triggered by elastic precursor wave is small while the following plastic load wave causes larger amplitude fluctuations because of its larger energy. The loading process and unloading process of the waves have led to the amplitude increase of the piezoelectric signal.
To analyze the dynamic response of the back of AZ31B magnesium alloy sheet to laser shock wave, the laser induced shockwave was measured by PVDF patch sensors and a digital oscilloscope and then piezoelectric waveforms were got. The propagation law of elastic and plastic wave structure was studied combined with shock wave propagation characteristics. The results indicate that the laser induced dynamic response of the material is transient. The time of elastic precursors wave and plastic load wave propagate to the back of the sheet is reflected by the piezoelectric waveforms. Which corresponds to the time of the theory. The waveform amplitude triggered by elastic precursor wave is small while the following plastic load wave causes larger amplitude fluctuations because of its larger energy. The loading process and unloading process of the waves have led to the amplitude increase of the piezoelectric signal.
2014,
26: 109003.
doi: 10.11884/HPLPB201426.109003
Abstract:
Macro-physical characteristics of cirrus above Shouxian were studied using data from micro-pulse lidar (MPL ) and millimeter wave cloud radar (MWCR) on mobile facilities of atmospheric radiation measurement (ARM). Enlarged profile and comprehensive information of cirrus were retrieved when combined data of these two facilities were used, which indicated the necessity of joint observation. On this basis, statistical analysis was performed using cirrus cases occurred above Shouxian during observation period. The results showed that the averaged height of cloud base ranged from 5 to 10 km, and cirrus with a base height of 6-11 km had higher occurrence frequency. The averaged thickness of cloud ranged from 0.25 to 5 km, among which cirrus with a thickness of 0.5-2.5 km accounted for 90.8%. The statistical results also showed the occurrence frequency of cirrus process reduced with the increase of duration, the maximum and mean duration were 35.5 h and 3.6 h respectively, and cirrus with duration less than 5 h accounted for 82.5%.
Macro-physical characteristics of cirrus above Shouxian were studied using data from micro-pulse lidar (MPL ) and millimeter wave cloud radar (MWCR) on mobile facilities of atmospheric radiation measurement (ARM). Enlarged profile and comprehensive information of cirrus were retrieved when combined data of these two facilities were used, which indicated the necessity of joint observation. On this basis, statistical analysis was performed using cirrus cases occurred above Shouxian during observation period. The results showed that the averaged height of cloud base ranged from 5 to 10 km, and cirrus with a base height of 6-11 km had higher occurrence frequency. The averaged thickness of cloud ranged from 0.25 to 5 km, among which cirrus with a thickness of 0.5-2.5 km accounted for 90.8%. The statistical results also showed the occurrence frequency of cirrus process reduced with the increase of duration, the maximum and mean duration were 35.5 h and 3.6 h respectively, and cirrus with duration less than 5 h accounted for 82.5%.
2014,
26: 101004.
doi: 10.11884/HPLPB201426.101004
Abstract:
This paper reports an intra-cavity rubidium titanyl phosphate(RTP) optical parametric oscillator producing the eye-safe light driven by LD end-pumping Nd:YAG laser. A non-critical phase matching RTP crystal with 4 mm4 mm20 mm in size was adopted for nonlinear optics crystal. The signal light output characteristics with different pulse repetition frequencies of Q-switcher were compared. With a diode pump power of 10.5 W and a pulse repetition frequency of 15 kHz, a maximum output power of 900 mW eye-safe laser at 1.62 m were achieved, with a diode to signal conversion efficiency up to 8.6%. The pulse widths for the 1.62 m signal light and 1.06 m fundamental light were about 4.6 and 8.2 ns, respectively. The center wavelength of signal light was about 1618 nm with a line-width less than 0.5 nm.
This paper reports an intra-cavity rubidium titanyl phosphate(RTP) optical parametric oscillator producing the eye-safe light driven by LD end-pumping Nd:YAG laser. A non-critical phase matching RTP crystal with 4 mm4 mm20 mm in size was adopted for nonlinear optics crystal. The signal light output characteristics with different pulse repetition frequencies of Q-switcher were compared. With a diode pump power of 10.5 W and a pulse repetition frequency of 15 kHz, a maximum output power of 900 mW eye-safe laser at 1.62 m were achieved, with a diode to signal conversion efficiency up to 8.6%. The pulse widths for the 1.62 m signal light and 1.06 m fundamental light were about 4.6 and 8.2 ns, respectively. The center wavelength of signal light was about 1618 nm with a line-width less than 0.5 nm.
2014,
26: 104005.
doi: 10.11884/HPLPB201426.104005
Abstract:
An in-situ temperature loading system was designed. It can control the samples temperature from 25 ℃ to 800 ℃, and the temperature controller applied improved Dahlin algorithm to inhibit temperature overshoot. The system was tested with neutron beam on the residual stress neutron diffractometer. The result shows that the structure suits for neutron diffraction experiment, and the temperature keeps not higher than the target during the ascending period, and the precision is 1 ℃ during the stable period, which meets temperature loading requirements for shape memory materials.
An in-situ temperature loading system was designed. It can control the samples temperature from 25 ℃ to 800 ℃, and the temperature controller applied improved Dahlin algorithm to inhibit temperature overshoot. The system was tested with neutron beam on the residual stress neutron diffractometer. The result shows that the structure suits for neutron diffraction experiment, and the temperature keeps not higher than the target during the ascending period, and the precision is 1 ℃ during the stable period, which meets temperature loading requirements for shape memory materials.
