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RSS2015 Vol. 27, No. 11
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2015,
27: 111001.
doi: 10.11884/HPLPB201527.111001
Abstract:
The time jitter should be detected and controlled accurately for multi-beam laser facility. In this paper, a spectral interferometry method is used to measure the time jitter between beams of the typical large laser facility SG-Ⅲ prototype in the running state. The basic principle to measure the time jitter using spectral interferometry is investigated theoretically. Several key parameters for measurement accuracy are analyzed. Experimental results prove that the spectral interferometry method applied to beam time jitter measurement is effective.
The time jitter should be detected and controlled accurately for multi-beam laser facility. In this paper, a spectral interferometry method is used to measure the time jitter between beams of the typical large laser facility SG-Ⅲ prototype in the running state. The basic principle to measure the time jitter using spectral interferometry is investigated theoretically. Several key parameters for measurement accuracy are analyzed. Experimental results prove that the spectral interferometry method applied to beam time jitter measurement is effective.
2015,
27: 111002.
doi: 10.11884/HPLPB201527.111002
Abstract:
The propagation of axis-symmetric ultra-short high-intensity laser pulse in air can be described by the 2D+1 non-linear Schrodinger equation, which is often solved by the FCN method (split-step Fourier method with Crank-Nicholson scheme in the transverse direction). However, since the FCN method is very time-consuming, the series FCN code can only deal with the simulations of the propagation of laser pulse up to hundreds meters. We develop a parallel algorithm for the FCN method basing on OpenMP. Numerical simulations demonstrate the correctness and high parallel-efficiency of the parallel FCN code. The speed-up ratio is about 12 for 15 threads. The parallel FCN code can be used to simulate the long-distance propagation of the ultra-short high-intensity laser pulses.
The propagation of axis-symmetric ultra-short high-intensity laser pulse in air can be described by the 2D+1 non-linear Schrodinger equation, which is often solved by the FCN method (split-step Fourier method with Crank-Nicholson scheme in the transverse direction). However, since the FCN method is very time-consuming, the series FCN code can only deal with the simulations of the propagation of laser pulse up to hundreds meters. We develop a parallel algorithm for the FCN method basing on OpenMP. Numerical simulations demonstrate the correctness and high parallel-efficiency of the parallel FCN code. The speed-up ratio is about 12 for 15 threads. The parallel FCN code can be used to simulate the long-distance propagation of the ultra-short high-intensity laser pulses.
2015,
27: 111003.
doi: 10.11884/HPLPB201527.111003
Abstract:
To achieve the high efficiency and accuracy of multi-parameter processing tolerance of fast axis collimation cylindrical lens used by semiconductor laser, we have established the corresponding theoretical model for multi-parameter theoretical model processing tolerances by geometrical optics method based on the theory of collimating the fast axis beam. Using the limit deviation of all the structural parameters as the initial value of tolerance, processing precision as the boundary conditions and optimizing the tolerance according to the requirement of design, the tolerances of all the parameters are set quickly and logically. Having designed the fast axis collimation cylindrical lens for a semiconductor laser with 36divergence in fast axis of TO-MOUNT model, we developed quickly the tolerance of the fast axis collimation cylindrical lens by the model in the paper. The simulation result in ZEMAX by importing the tolerance meets the design requirement.
To achieve the high efficiency and accuracy of multi-parameter processing tolerance of fast axis collimation cylindrical lens used by semiconductor laser, we have established the corresponding theoretical model for multi-parameter theoretical model processing tolerances by geometrical optics method based on the theory of collimating the fast axis beam. Using the limit deviation of all the structural parameters as the initial value of tolerance, processing precision as the boundary conditions and optimizing the tolerance according to the requirement of design, the tolerances of all the parameters are set quickly and logically. Having designed the fast axis collimation cylindrical lens for a semiconductor laser with 36divergence in fast axis of TO-MOUNT model, we developed quickly the tolerance of the fast axis collimation cylindrical lens by the model in the paper. The simulation result in ZEMAX by importing the tolerance meets the design requirement.
2015,
27: 111004.
doi: 10.11884/HPLPB201527.111004
Abstract:
The performance of algorithm is seriously affected by background dictionary in sparse representation based hyperspectral detection. In this paper, a new dictionary learning (DL) sparse representation (SR) based algorithm for anomaly detection in hyperspectral imagery (HSI) was proposed. Principal component analysis (PCA) was used to extract main character of hyperspectral data. Thus, principal component space was established and the feasibility of DLSR in principal component space was proved. Then, the K-SVD algorithm based background dictionary was locally generated using dual window centered at the pixel of interest. Orthogonal matching pursuit (OMP) algorithm and PCA inverse transform were used to reconstruct the original spectrum based on trained dictionary. Thus, regions containing targets were detected by using spectral reconstruction error. Experimental results indicate that the proposed algorithm is effective.
The performance of algorithm is seriously affected by background dictionary in sparse representation based hyperspectral detection. In this paper, a new dictionary learning (DL) sparse representation (SR) based algorithm for anomaly detection in hyperspectral imagery (HSI) was proposed. Principal component analysis (PCA) was used to extract main character of hyperspectral data. Thus, principal component space was established and the feasibility of DLSR in principal component space was proved. Then, the K-SVD algorithm based background dictionary was locally generated using dual window centered at the pixel of interest. Orthogonal matching pursuit (OMP) algorithm and PCA inverse transform were used to reconstruct the original spectrum based on trained dictionary. Thus, regions containing targets were detected by using spectral reconstruction error. Experimental results indicate that the proposed algorithm is effective.
2015,
27: 111005.
doi: 10.11884/HPLPB201527.111005
Abstract:
A small-scale direct current(DC)-discharge excited continuous-wave(CW) DF chemical laser is studied through experiments. The output power of the laser reached 188.4 W and 205.8 W, at about 10 mm and 15 mm downstream of the nozzle exit plane respectively, at the wavelength of 3.6~4.1 m. The electrical-to-laser power conversion efficiency was about 2.3% and 2.5% respectively. The experiments show good PV stability of about 1.04% and RMA stability of about 0.49% for long time(100 s) running, and good repeatability. This small-scale DC-discharge excited CW DF chemical laser performs well and operates simply, is an applicable infrared laser source for absorption measurement of the optical films under high power density.
A small-scale direct current(DC)-discharge excited continuous-wave(CW) DF chemical laser is studied through experiments. The output power of the laser reached 188.4 W and 205.8 W, at about 10 mm and 15 mm downstream of the nozzle exit plane respectively, at the wavelength of 3.6~4.1 m. The electrical-to-laser power conversion efficiency was about 2.3% and 2.5% respectively. The experiments show good PV stability of about 1.04% and RMA stability of about 0.49% for long time(100 s) running, and good repeatability. This small-scale DC-discharge excited CW DF chemical laser performs well and operates simply, is an applicable infrared laser source for absorption measurement of the optical films under high power density.
2015,
27: 111006.
doi: 10.11884/HPLPB201527.111006
Abstract:
There are many extinction characterization methods for soot, but they always cost much when used to appraise the extinction characteristics of soot with unsteady distribution. This paper introduces a simple extinction characterization method. It appraises the extinction characteristics of the soot with its mean mass extinction coefficient weighted with the mass concentration. According to the theory derivation, the extinction coefficient of the soot is the product of the mean mass extinction coefficient and the total mass concentration. Fortunately, every term in the expression of mean mass extinction coefficient can be obtained by theoretical and experimental methods. A theoretical analysis of variance tendency of mean mass extinction coefficient is carried out associated with the variance of diameters and aggregate sizes of the soot. It predicts that the mean mass extinction coefficient decreases significantly at first with the decrease of the diameters and aggregate sizes of the soot, and then slightly since it enters into the glacis.
There are many extinction characterization methods for soot, but they always cost much when used to appraise the extinction characteristics of soot with unsteady distribution. This paper introduces a simple extinction characterization method. It appraises the extinction characteristics of the soot with its mean mass extinction coefficient weighted with the mass concentration. According to the theory derivation, the extinction coefficient of the soot is the product of the mean mass extinction coefficient and the total mass concentration. Fortunately, every term in the expression of mean mass extinction coefficient can be obtained by theoretical and experimental methods. A theoretical analysis of variance tendency of mean mass extinction coefficient is carried out associated with the variance of diameters and aggregate sizes of the soot. It predicts that the mean mass extinction coefficient decreases significantly at first with the decrease of the diameters and aggregate sizes of the soot, and then slightly since it enters into the glacis.
2015,
27: 111007.
doi: 10.11884/HPLPB201527.111007
Abstract:
A passively Q-switched mode-locked Nd:YVO4 laser based upon V:YAG saturable absorber at 1.34 m is reported. In the case of LD end-pumped, 1.34 m Q-switch mode-locked pulse operation with a repetition rate up to 2.6 GHz is realized by using linear cavity structure at output mirror with 10% transmittance. The Nd3+ concentration of the Nd:YVO4 crystal is 0.2%, and the initial transmittance of V:YAG is 83%. When the incident pump power is 11 W, the maximum average output power of the 1.34 m Q-switched mode-locked laser is 308 mW with a light-light conversion efficiency of 2.8%.
A passively Q-switched mode-locked Nd:YVO4 laser based upon V:YAG saturable absorber at 1.34 m is reported. In the case of LD end-pumped, 1.34 m Q-switch mode-locked pulse operation with a repetition rate up to 2.6 GHz is realized by using linear cavity structure at output mirror with 10% transmittance. The Nd3+ concentration of the Nd:YVO4 crystal is 0.2%, and the initial transmittance of V:YAG is 83%. When the incident pump power is 11 W, the maximum average output power of the 1.34 m Q-switched mode-locked laser is 308 mW with a light-light conversion efficiency of 2.8%.
2015,
27: 111008.
doi: 10.11884/HPLPB201527.111008
Abstract:
Signal processing solution of laser Doppler velocimetry in the high dynamic environment based on FPGA (field programmable gate array) was proposed. The whole signal processing was finished by FPGA. The signal spectrum was acquired by the FFT (Fast Fourier Transform) algorithm and was adjusted by the energy centrobaric correction method. Adaptive algorithm of sampling frequency was proposed to balance the measurement accuracy with measurement range; finally, the result through a universal serial bus (USB) was uploaded to a personal computer (PC).Pipelined architecture was used to improve the speed of signal processing. Experimental results showed that the data updating rate reached 2.4 - 24 kHz, the data delay reached 123 - 1230 s, the accuracy was better than 810-4 and the stability was better than 2.510-7.
Signal processing solution of laser Doppler velocimetry in the high dynamic environment based on FPGA (field programmable gate array) was proposed. The whole signal processing was finished by FPGA. The signal spectrum was acquired by the FFT (Fast Fourier Transform) algorithm and was adjusted by the energy centrobaric correction method. Adaptive algorithm of sampling frequency was proposed to balance the measurement accuracy with measurement range; finally, the result through a universal serial bus (USB) was uploaded to a personal computer (PC).Pipelined architecture was used to improve the speed of signal processing. Experimental results showed that the data updating rate reached 2.4 - 24 kHz, the data delay reached 123 - 1230 s, the accuracy was better than 810-4 and the stability was better than 2.510-7.
2015,
27: 111009.
doi: 10.11884/HPLPB201527.111009
Abstract:
Within a typical chemical oxygen-iodine laser(COIL), the residual heat could cause heat blocking in the pressure recovery system due to the chemical reaction in the laser cavity and the diffuser, which contributes to the failures of the diffuser start-up and the uniformity deteriorations of the supersonic flow in the cavity. For the pressure recovery performance, the total pressure losses due to the reaction could be up to 15%. By numerical simulations of the reaction flow in COIL cavities and supersonic diffusers, we investigated different configurations of the COIL supersonic diffuser, focusing on insert section length, number and shape of wedges, and diffuser length. The results show that under the adverse effect of residual reaction, the performance of the pressure recovery system can be improved by optimizing the insert section, adjusting the wedge length, and removing the semi-wedges in the diffuser side wall. The optimal diffuser geometry proposed in this paper proves to be heat-blocking-free, where the supersonic flow in cavity is not affected by the oblique shock waves due to separation. There is no separation in the choke of the diffuser. The separation area in the diffuser side wall decreases, and a more uniform outflow is achieved. For the pressure recovery system and COIL configuration in the paper, the optimal geometry achieves a total pressure recovery ratio of 0.426 and a static pressure ratio of 3.75, which are 25% better than the original design.
Within a typical chemical oxygen-iodine laser(COIL), the residual heat could cause heat blocking in the pressure recovery system due to the chemical reaction in the laser cavity and the diffuser, which contributes to the failures of the diffuser start-up and the uniformity deteriorations of the supersonic flow in the cavity. For the pressure recovery performance, the total pressure losses due to the reaction could be up to 15%. By numerical simulations of the reaction flow in COIL cavities and supersonic diffusers, we investigated different configurations of the COIL supersonic diffuser, focusing on insert section length, number and shape of wedges, and diffuser length. The results show that under the adverse effect of residual reaction, the performance of the pressure recovery system can be improved by optimizing the insert section, adjusting the wedge length, and removing the semi-wedges in the diffuser side wall. The optimal diffuser geometry proposed in this paper proves to be heat-blocking-free, where the supersonic flow in cavity is not affected by the oblique shock waves due to separation. There is no separation in the choke of the diffuser. The separation area in the diffuser side wall decreases, and a more uniform outflow is achieved. For the pressure recovery system and COIL configuration in the paper, the optimal geometry achieves a total pressure recovery ratio of 0.426 and a static pressure ratio of 3.75, which are 25% better than the original design.
2015,
27: 111010.
doi: 10.11884/HPLPB201527.111010
Abstract:
By using the Kramers-Henneberger (KH) transformation, the time-dependent Dirac equation in high-frequency (HF) intense laser fields can be changed to a time-independent equation with an effective Coulomb potential, which plays an important role in studying the adiabatic atomic stability problem in high-frequency laser fields. With numerical method, we have investigated in detail the characteristics of the obtained effective Coulomb potential. It has been found that when the laser intensity is high enough, the relativistic effect is so important that it modifies the effective potential drastically. Moreover, the dipole approximation, which is often used in literature when solving Schrodinger equation, is not proper for high-frequency laser fields.
By using the Kramers-Henneberger (KH) transformation, the time-dependent Dirac equation in high-frequency (HF) intense laser fields can be changed to a time-independent equation with an effective Coulomb potential, which plays an important role in studying the adiabatic atomic stability problem in high-frequency laser fields. With numerical method, we have investigated in detail the characteristics of the obtained effective Coulomb potential. It has been found that when the laser intensity is high enough, the relativistic effect is so important that it modifies the effective potential drastically. Moreover, the dipole approximation, which is often used in literature when solving Schrodinger equation, is not proper for high-frequency laser fields.
2015,
27: 111011.
doi: 10.11884/HPLPB201527.111011
Abstract:
Ladar range image is getting more and more attentions in the field of target recognition. The ladar range image will be severely disrupted when the ladar is working in a poor condition, it is necessary to remove the abnormal points that can not reflect true information. The distribution characteristics of the normal points are derived based on the distribution of the noises in the ladar range image, and a judging criterion of the abnormal points in ladar range image is obtained. The criterion can be expressed as a function of sampling distribution in small area, and its value can be estimated by the median method of robust statistics. Hence the anomalies can be removed and the ladar range image after noise suppression can be obtained. Both the simulation analysis and the actual ladar range image processing are carried out based on the proposed arithmetic and compared with the median filter arithmetic. The results show the noise suppression arithmetic based on the statistical property of ladar range image can not only remove noises very effectively, but also protect the details well. The algorithm makes full use of the high ranging accuracy of laser imaging radar, has the ability to deal with the requirement of different scenarios, and it is proved to be strongly practicable.
Ladar range image is getting more and more attentions in the field of target recognition. The ladar range image will be severely disrupted when the ladar is working in a poor condition, it is necessary to remove the abnormal points that can not reflect true information. The distribution characteristics of the normal points are derived based on the distribution of the noises in the ladar range image, and a judging criterion of the abnormal points in ladar range image is obtained. The criterion can be expressed as a function of sampling distribution in small area, and its value can be estimated by the median method of robust statistics. Hence the anomalies can be removed and the ladar range image after noise suppression can be obtained. Both the simulation analysis and the actual ladar range image processing are carried out based on the proposed arithmetic and compared with the median filter arithmetic. The results show the noise suppression arithmetic based on the statistical property of ladar range image can not only remove noises very effectively, but also protect the details well. The algorithm makes full use of the high ranging accuracy of laser imaging radar, has the ability to deal with the requirement of different scenarios, and it is proved to be strongly practicable.
2015,
27: 111012.
doi: 10.11884/HPLPB201527.111012
Abstract:
To improve acquisition rate of laser proximity fuze in ATT(anti-torpedo torpedo) in detecting the torpedo target, the changing rules of target echo power with laser beam incident angle and position were analyzed according to torpedo targets laser reflection characteristics. The rendezvous model of ATT and attacking torpedo was described by using spatial analytic geometry method. And the target echo power calculation method at any intersection distance and attitude was given. The Monte Carlo simulation model of acquisition rate in underwater single beam scanning laser fuze was established based on system minimum detecting power, and the system acquisition rate changing with laser pulse frequency was calculated. The maximum acquisition rate and corresponding laser scanning frequency and pulse frequency were obtained when the target was at different distance. The results showed that the system can reliably acquire the target at a distance of 9 m, when the laser scanning frequency is 15 Hz, and the pulse frequency is 4 kHz. Thus, this work can provide a theoretical basis for designing the single beam scanning laser fuze of ATT.
To improve acquisition rate of laser proximity fuze in ATT(anti-torpedo torpedo) in detecting the torpedo target, the changing rules of target echo power with laser beam incident angle and position were analyzed according to torpedo targets laser reflection characteristics. The rendezvous model of ATT and attacking torpedo was described by using spatial analytic geometry method. And the target echo power calculation method at any intersection distance and attitude was given. The Monte Carlo simulation model of acquisition rate in underwater single beam scanning laser fuze was established based on system minimum detecting power, and the system acquisition rate changing with laser pulse frequency was calculated. The maximum acquisition rate and corresponding laser scanning frequency and pulse frequency were obtained when the target was at different distance. The results showed that the system can reliably acquire the target at a distance of 9 m, when the laser scanning frequency is 15 Hz, and the pulse frequency is 4 kHz. Thus, this work can provide a theoretical basis for designing the single beam scanning laser fuze of ATT.
2015,
27: 111013.
doi: 10.11884/HPLPB201527.111013
Abstract:
We briefly present design parameters and fabrication procedures of polarization independent gratings made on multilayer dielectric thin film substrates for spectral beam combining applications. In the wavelength range of 1.044 m to 1.084 m the -1st Littrow order average diffraction efficiencies of TE polarization and TM polarization are 89.7% and 93.8% respectively.
We briefly present design parameters and fabrication procedures of polarization independent gratings made on multilayer dielectric thin film substrates for spectral beam combining applications. In the wavelength range of 1.044 m to 1.084 m the -1st Littrow order average diffraction efficiencies of TE polarization and TM polarization are 89.7% and 93.8% respectively.
2015,
27: 112001.
doi: 10.11884/HPLPB201527.112001
Abstract:
As the fast development of ultra-short ultra-intense laser technology and mechanism research of laser ion acceleration, laser-driven ion accelerators have drawn a lot of attention for the past decades. Thomson spectrometer is one of the critical diagnostics for laser-driven ion acceleration, because of its ability to measure ions energy spectrum, charge, and charge-to-mass radio parameters simultaneously. This paper presents a compact real-time single-shot Thomson spectrometer, which uses electromagnetic field to disperse ions and scintillator coupled with high performance EMCCD as a record medium. The spectrometer has a pair of inclined electric plates with the advantage of avoiding electromagnetic noise caused by low energy ions collision with electric plates, improving signal-to-noise ratio accordingly. Experiments were carried out on two conventional accelerators in Peking University to test the spectrometer and measure detection efficiency of ions at the same time. It turns out that the spectrometer can be used for detection of ions driven by 100 TW class femtosecond laser system, and will contribute to our understanding of laser-based high energy density physics.
As the fast development of ultra-short ultra-intense laser technology and mechanism research of laser ion acceleration, laser-driven ion accelerators have drawn a lot of attention for the past decades. Thomson spectrometer is one of the critical diagnostics for laser-driven ion acceleration, because of its ability to measure ions energy spectrum, charge, and charge-to-mass radio parameters simultaneously. This paper presents a compact real-time single-shot Thomson spectrometer, which uses electromagnetic field to disperse ions and scintillator coupled with high performance EMCCD as a record medium. The spectrometer has a pair of inclined electric plates with the advantage of avoiding electromagnetic noise caused by low energy ions collision with electric plates, improving signal-to-noise ratio accordingly. Experiments were carried out on two conventional accelerators in Peking University to test the spectrometer and measure detection efficiency of ions at the same time. It turns out that the spectrometer can be used for detection of ions driven by 100 TW class femtosecond laser system, and will contribute to our understanding of laser-based high energy density physics.
2015,
27: 112002.
doi: 10.11884/HPLPB201527.112002
Abstract:
In order to research the instability of stimulated Brillouin scattering(SBS) in the interaction of laser and plasma(LPI), three-wave mathematic models of SBS are established. According to the characteristic of equations, the operator splitting method, the coordinate transform, the parallel FFT and the reduce density algorithms are proposed. The numerical results demonstrate the validity of the algorithm. Scalability is demonstrated with a parallel efficiency above 81.6% with almost three hundred million meshes in 4096 cores.
In order to research the instability of stimulated Brillouin scattering(SBS) in the interaction of laser and plasma(LPI), three-wave mathematic models of SBS are established. According to the characteristic of equations, the operator splitting method, the coordinate transform, the parallel FFT and the reduce density algorithms are proposed. The numerical results demonstrate the validity of the algorithm. Scalability is demonstrated with a parallel efficiency above 81.6% with almost three hundred million meshes in 4096 cores.
2015,
27: 112003.
doi: 10.11884/HPLPB201527.112003
Abstract:
In the stability design of a high-power laser facility, the simulation results are important references, and the reliability of the simulation results is important. In order to evaluate the reliability of the stability analysis results, the maximum displacement response of Shenguang-Ⅲ chamber is predicted based on uncertainty quantification and propagation methods, and the model form error and the prediction methods in the modern model verification and validation (VV). The quadratic polynomial response surface model is regarded as the metal model to improve the efficiency on the parameter propagating and sensitivity analyzing. The sensitivity analysis result shows that the modal damping ratios are more important than the mechanical parameters of the concrete. The stability prediction result of quantity of interest shows that the stability design margin of Shenguang-Ⅲ chamber is more than 7 times, which validates that the stability design of Shenguang-Ⅲ chamber is reliable enough.
In the stability design of a high-power laser facility, the simulation results are important references, and the reliability of the simulation results is important. In order to evaluate the reliability of the stability analysis results, the maximum displacement response of Shenguang-Ⅲ chamber is predicted based on uncertainty quantification and propagation methods, and the model form error and the prediction methods in the modern model verification and validation (VV). The quadratic polynomial response surface model is regarded as the metal model to improve the efficiency on the parameter propagating and sensitivity analyzing. The sensitivity analysis result shows that the modal damping ratios are more important than the mechanical parameters of the concrete. The stability prediction result of quantity of interest shows that the stability design margin of Shenguang-Ⅲ chamber is more than 7 times, which validates that the stability design of Shenguang-Ⅲ chamber is reliable enough.
2015,
27: 112004.
doi: 10.11884/HPLPB201527.112004
Abstract:
According to the requirements of Z-pinch experiments on primary test stand(PTS) facility, we develop a three-channel, time-integrated X-ray imaging system with different spectral responses. This imaging system consists of a pinhole array, a pipe through which the X-ray propagates and imaging plates. The spectral ranges of the three channels are 277 eV, 700 eV and 800 eV, corresponding to pinholes with diameter of 100 m，100 m and 50 m respectively. This system has a magnification of 2, and a spatial resolution of 0.2 mm. This system is tested on PTS and the results show that it meets the diagnostic requirements of Z-pinch experiments on PTS very well, AND can improve the spectral coverage and the image resolution of the low photon energy channel at the same time.
According to the requirements of Z-pinch experiments on primary test stand(PTS) facility, we develop a three-channel, time-integrated X-ray imaging system with different spectral responses. This imaging system consists of a pinhole array, a pipe through which the X-ray propagates and imaging plates. The spectral ranges of the three channels are 277 eV, 700 eV and 800 eV, corresponding to pinholes with diameter of 100 m，100 m and 50 m respectively. This system has a magnification of 2, and a spatial resolution of 0.2 mm. This system is tested on PTS and the results show that it meets the diagnostic requirements of Z-pinch experiments on PTS very well, AND can improve the spectral coverage and the image resolution of the low photon energy channel at the same time.
2015,
27: 112005.
doi: 10.11884/HPLPB201527.112005
Abstract:
This paper presents the principle of DT neutron yields diagnostic by copper activation and analyses the contributions of two kinds of nuclei 62Cu and 64Cu in the coincidence measurement. Two calibration methods of the diagnostic system are introduced for different ranges of neutron yields, which are the relative method and the 64Cu nuclei method. The scattered neutron of the accelerator room is measured by placing a polypropylene shield in front of a copper sample. The effect of the reaction 63Cu(n, )64Cu on the copper activation measurement is calculated and evaluated. This system is used to measure neutron yields from directly-driven implosions on Shenguang-Ⅲ laser facility. The experimental results show the relative method and the 64Cu nuclei method are fit in the range of DT neutron yield 109-1013 and 1012-1016, respectively. The effect of the scattered neutrons from the accelerator room on the calibrated sensitivity is about 0.4%, and the contribution of 63Cu capture reaction on the calibrated sensitivity using the 64Cu nuclei method is less than 1%. At present, DT neutron yields from directly-driven implosions on Shenguang-Ⅲ laser facility is about 81012.
This paper presents the principle of DT neutron yields diagnostic by copper activation and analyses the contributions of two kinds of nuclei 62Cu and 64Cu in the coincidence measurement. Two calibration methods of the diagnostic system are introduced for different ranges of neutron yields, which are the relative method and the 64Cu nuclei method. The scattered neutron of the accelerator room is measured by placing a polypropylene shield in front of a copper sample. The effect of the reaction 63Cu(n, )64Cu on the copper activation measurement is calculated and evaluated. This system is used to measure neutron yields from directly-driven implosions on Shenguang-Ⅲ laser facility. The experimental results show the relative method and the 64Cu nuclei method are fit in the range of DT neutron yield 109-1013 and 1012-1016, respectively. The effect of the scattered neutrons from the accelerator room on the calibrated sensitivity is about 0.4%, and the contribution of 63Cu capture reaction on the calibrated sensitivity using the 64Cu nuclei method is less than 1%. At present, DT neutron yields from directly-driven implosions on Shenguang-Ⅲ laser facility is about 81012.
2015,
27: 112006.
doi: 10.11884/HPLPB201527.112006
Abstract:
Positron production from ultra-intense laser-solid interactions is investigated using the Monte Carlo code Geant4. The dependence of the positron production on hot electron energy distribution, angular emission and target thickness is examined. The results show that there is at most a 3 times discrepancy in yield comparison if different distribution functions of the hot electrons are used. It is also found that there is no obvious changes in positron yield when different hot electron emission models are used, but the positron beam divergence increases obviously with the hot electron divergence when a Gaussian angular distribution is assumed. In addition, the results indicate that the positron divergence increases with target thickness below 2 mm, above which a saturated trend shows up. The influences of the hot electron divergence, the target thickness and the sheath field on the angular distribution of e+/e- (ratio of positron to electron) and e+/ (ratio of positron to gamma) are studied.
Positron production from ultra-intense laser-solid interactions is investigated using the Monte Carlo code Geant4. The dependence of the positron production on hot electron energy distribution, angular emission and target thickness is examined. The results show that there is at most a 3 times discrepancy in yield comparison if different distribution functions of the hot electrons are used. It is also found that there is no obvious changes in positron yield when different hot electron emission models are used, but the positron beam divergence increases obviously with the hot electron divergence when a Gaussian angular distribution is assumed. In addition, the results indicate that the positron divergence increases with target thickness below 2 mm, above which a saturated trend shows up. The influences of the hot electron divergence, the target thickness and the sheath field on the angular distribution of e+/e- (ratio of positron to electron) and e+/ (ratio of positron to gamma) are studied.
2015,
27: 112007.
doi: 10.11884/HPLPB201527.112007
Abstract:
A detailed model of Shenguang Ⅲ target bay was developed by JMCT, a 3D neutron and photon transport Monte Carlo code. Using this model, calculations were performed to obtain the spatial distribution, energy spectra and time of flight spectra of fusion neutron and gamma radiations from DD implosions. Characteristics of scattered neutron and gamma radiations were discussed based on the calculated results. In particular, the impacts of neutron noise on down-scattered neutron yield measurement and gamma noise on high energy X-ray radiography were analyzed quantitatively. The results showed that in order to obtain a signal-to-noise ratio better than 10, effective radiation shielding was required for both down scattered neutron yield measurement and high energy X-ray radiography.
A detailed model of Shenguang Ⅲ target bay was developed by JMCT, a 3D neutron and photon transport Monte Carlo code. Using this model, calculations were performed to obtain the spatial distribution, energy spectra and time of flight spectra of fusion neutron and gamma radiations from DD implosions. Characteristics of scattered neutron and gamma radiations were discussed based on the calculated results. In particular, the impacts of neutron noise on down-scattered neutron yield measurement and gamma noise on high energy X-ray radiography were analyzed quantitatively. The results showed that in order to obtain a signal-to-noise ratio better than 10, effective radiation shielding was required for both down scattered neutron yield measurement and high energy X-ray radiography.
2015,
27: 112008.
doi: 10.11884/HPLPB201527.112008
Abstract:
Atmosphere pressure plasma cleaning was utilized to clean grease contamination on the surface of sol-gel SiO2 coating on K9 glass. The optical property and laser-induced damage threshold of sol-gel coating were investigated by spectrophotometer, scanning electrical microscope and infrared spectrometer, respectively. After cleaning, the laser-induced damage threshold increased from 16.08 J/cm2 to 24.41 J/cm2 with irradiated by 1064 nm, approximate to the laser-induced damage threshold before pollution. The experimental results showed that the grease contamination on the sol-gel SiO2 coating could be well cleaned by atmosphere pressure plasma jet without the coating damaged and contamination residual by properly controlling the technological parameters.
Atmosphere pressure plasma cleaning was utilized to clean grease contamination on the surface of sol-gel SiO2 coating on K9 glass. The optical property and laser-induced damage threshold of sol-gel coating were investigated by spectrophotometer, scanning electrical microscope and infrared spectrometer, respectively. After cleaning, the laser-induced damage threshold increased from 16.08 J/cm2 to 24.41 J/cm2 with irradiated by 1064 nm, approximate to the laser-induced damage threshold before pollution. The experimental results showed that the grease contamination on the sol-gel SiO2 coating could be well cleaned by atmosphere pressure plasma jet without the coating damaged and contamination residual by properly controlling the technological parameters.
2015,
27: 112009.
doi: 10.11884/HPLPB201527.112009
Abstract:
Ni-doped MF(melamine-formaldehyde) aerogels are prepared through impregnation-reduction with the hydrazinium hydroxide(80%, AR) as the reducing agent after MF aerogels being activated by PdCl2. Both the Scanning Electron Microscope(SEM) and the Transmission Electron Microscope (TEM) images demonstrate that there are a great deal of Ni particles with a size of 100nm existing in the framework of MF aerogels. Meanwhile, a small part of clusters is observed in the SEM and TEM images. The nitrogen adsorption-desorption data show that the specific surface area, total pore volume and micropore volume of MF aerogels all decrease after Ni doping. Moreover, a small amount of macropore is produced by large size Ni particle clusters, further confirming that the nanochannels of MF aerogels are filled with Ni.
Ni-doped MF(melamine-formaldehyde) aerogels are prepared through impregnation-reduction with the hydrazinium hydroxide(80%, AR) as the reducing agent after MF aerogels being activated by PdCl2. Both the Scanning Electron Microscope(SEM) and the Transmission Electron Microscope (TEM) images demonstrate that there are a great deal of Ni particles with a size of 100nm existing in the framework of MF aerogels. Meanwhile, a small part of clusters is observed in the SEM and TEM images. The nitrogen adsorption-desorption data show that the specific surface area, total pore volume and micropore volume of MF aerogels all decrease after Ni doping. Moreover, a small amount of macropore is produced by large size Ni particle clusters, further confirming that the nanochannels of MF aerogels are filled with Ni.
2015,
27: 112010.
doi: 10.11884/HPLPB201527.112010
Abstract:
The traditional static etching method was improved, a new megasonic-assisted chemical etching method of optical components was proposed. The megasonic assisted chemical etching effects were compared with those of static etching. Considering the effects of the ratio of the etching solution, etching time, active agent types and megasonic power, the etching process parameters were optimized. The results showed that megasonics assisted chemical etching was better for all kinds of impurities removal than the manual scrubbing, and it had a higher etching rate than the traditional static etching, its etching liquid could enter into the micro-cracks, which was difficult for the traditional static etching, thus the etching effect was more obvious and laser damage threshold could be further improved.
The traditional static etching method was improved, a new megasonic-assisted chemical etching method of optical components was proposed. The megasonic assisted chemical etching effects were compared with those of static etching. Considering the effects of the ratio of the etching solution, etching time, active agent types and megasonic power, the etching process parameters were optimized. The results showed that megasonics assisted chemical etching was better for all kinds of impurities removal than the manual scrubbing, and it had a higher etching rate than the traditional static etching, its etching liquid could enter into the micro-cracks, which was difficult for the traditional static etching, thus the etching effect was more obvious and laser damage threshold could be further improved.
2015,
27: 112011.
doi: 10.11884/HPLPB201527.112011
Abstract:
La-based aerogels were synthesized by using LaCl37H2O as precursor, methanol and ethanol as solvents, via sol-gel process. The microstructure, components, specific surface area, pore diameter distribution and mechanical properties were characterized by scanning electron microscopy, Fourier transform infrared spectrometer, adsorption/desorption analysis and mechanical property tester, respectively. The results reveals that La-based aerogels derived from methanol and ethanol have a three-dimension network that consists of interconnected bead-like particles with diameters varying from several tens to hundreds nanometer. Comparing to the aerogel (specific surface area: 95 m2g-1, density: about 350 mgcm-3) derived from methanol, the aerogel (specific surface area: 220 m2g-1, density: about 160 mgcm-3) derived from ethanol possesses better pore morphology and worse mechanical property. The properties of the La-based aerogels can be attributed to the stronger polarity of methanol.
La-based aerogels were synthesized by using LaCl37H2O as precursor, methanol and ethanol as solvents, via sol-gel process. The microstructure, components, specific surface area, pore diameter distribution and mechanical properties were characterized by scanning electron microscopy, Fourier transform infrared spectrometer, adsorption/desorption analysis and mechanical property tester, respectively. The results reveals that La-based aerogels derived from methanol and ethanol have a three-dimension network that consists of interconnected bead-like particles with diameters varying from several tens to hundreds nanometer. Comparing to the aerogel (specific surface area: 95 m2g-1, density: about 350 mgcm-3) derived from methanol, the aerogel (specific surface area: 220 m2g-1, density: about 160 mgcm-3) derived from ethanol possesses better pore morphology and worse mechanical property. The properties of the La-based aerogels can be attributed to the stronger polarity of methanol.
2015,
27: 113001.
doi: 10.11884/HPLPB201527.113001
Abstract:
In order to meet the diagnosis requirements of asymmetric mode competition in an X-band triaxial klystron amplifier, a novel waveguide coupler with compact structure is designed, and its coupling characteristics for TE61 mode are analyzed with small-hole coupling principle and CST simulation software. A physical model is established by using PIC method to diagnose the spectrum characteristics in the TKA coaxial drift tube. Through simulation, the validity of the designed coupler to diagnose TKA asymmetric mode competition is verified.
In order to meet the diagnosis requirements of asymmetric mode competition in an X-band triaxial klystron amplifier, a novel waveguide coupler with compact structure is designed, and its coupling characteristics for TE61 mode are analyzed with small-hole coupling principle and CST simulation software. A physical model is established by using PIC method to diagnose the spectrum characteristics in the TKA coaxial drift tube. Through simulation, the validity of the designed coupler to diagnose TKA asymmetric mode competition is verified.
2015,
27: 113002.
doi: 10.11884/HPLPB201527.113002
Abstract:
This paper presents a high efficiency Denisov quasi-optical mode converter for 140 GHz, TE28,8 mode gyrotron. The mode converter includes a dimpled wall launcher and a mirror system. The mirror system consists of four mirrors, of which the first mirror is a quasi-parabolic one. A simulation code is developed based on the coupled mode theory and the vector diffraction theory. The simulation results show that the focal length of the parabolic mirror has a great effect on the vector Gaussian correlation coefficient. Therefore, it is important to select an appropriate focal length for the mirror system. The simulation results show that the scalar Gaussian correlation coefficient of the operating cavity mode to a fundamental Gaussian distribution on the window plane is about 98%, and the corresponding vector correlation coefficient is more than 90%.
This paper presents a high efficiency Denisov quasi-optical mode converter for 140 GHz, TE28,8 mode gyrotron. The mode converter includes a dimpled wall launcher and a mirror system. The mirror system consists of four mirrors, of which the first mirror is a quasi-parabolic one. A simulation code is developed based on the coupled mode theory and the vector diffraction theory. The simulation results show that the focal length of the parabolic mirror has a great effect on the vector Gaussian correlation coefficient. Therefore, it is important to select an appropriate focal length for the mirror system. The simulation results show that the scalar Gaussian correlation coefficient of the operating cavity mode to a fundamental Gaussian distribution on the window plane is about 98%, and the corresponding vector correlation coefficient is more than 90%.
2015,
27: 113003.
doi: 10.11884/HPLPB201527.113003
Abstract:
A multiband printed monopole antenna applied to WLAN/WiMAX applications is designed. The top of the antenna is composed of three strips and the bottom is a defected ground structure used to improve the impedance matching of the antenna. The antenna was simulated by using a three-dimensional electromagnetic simulation software (Ansoft HFSS13.0), and it was fabricated on a substrate with teflon material. The sample of the presented antenna was connected to a test equipment (Agilent Technologies N5230C 10 MHz-20 GHz) for testing via an SMA adaptor. The measured result is consistent with the simulated result, which verifies the correctness of the design.
A multiband printed monopole antenna applied to WLAN/WiMAX applications is designed. The top of the antenna is composed of three strips and the bottom is a defected ground structure used to improve the impedance matching of the antenna. The antenna was simulated by using a three-dimensional electromagnetic simulation software (Ansoft HFSS13.0), and it was fabricated on a substrate with teflon material. The sample of the presented antenna was connected to a test equipment (Agilent Technologies N5230C 10 MHz-20 GHz) for testing via an SMA adaptor. The measured result is consistent with the simulated result, which verifies the correctness of the design.
2015,
27: 113101.
doi: 10.11884/HPLPB201527.113101
Abstract:
A three-dimensional finite element analysis (FEA) model is constructed and the influences of some parameters such as the film thickness, post-exposure-bake (PEB) temperature, cooling rate on the stress are numerically investigated employing thermal-structural coupling analysis based on the model. The simulation results shows that cooling rate has much more influence on the stress than the film thickness and PEB temperature and the stress is inversely proportional to the cooling rate. And the stress drops slightly when the cooling rate is lower than 6 ℃/h. The optimization experiment is carried out according to the simulation results and the phenomenon concerning the stress disappears, which proves the validity of the simulation method and results.
A three-dimensional finite element analysis (FEA) model is constructed and the influences of some parameters such as the film thickness, post-exposure-bake (PEB) temperature, cooling rate on the stress are numerically investigated employing thermal-structural coupling analysis based on the model. The simulation results shows that cooling rate has much more influence on the stress than the film thickness and PEB temperature and the stress is inversely proportional to the cooling rate. And the stress drops slightly when the cooling rate is lower than 6 ℃/h. The optimization experiment is carried out according to the simulation results and the phenomenon concerning the stress disappears, which proves the validity of the simulation method and results.
2015,
27: 113102.
doi: 10.11884/HPLPB201527.113102
Abstract:
In order to develop a wideband 0.22 THz folded-waveguide travelling wave tube, a slow wave structure and RF window are carefully designed. By theoretic analysis and simulation, the tube will work at the point where the dispersion curve is flat and instantaneous bandwidth is more than 16 GHz. In more than 30 GHz, S11 of the RF window is better than -25 dB. The experimental result of the first prototype tube shows that the instantaneous bandwidth is only about 8 GHz. After optimization, the instantaneous bandwidth of the second prototype tube becomes more than 12 GHz with an output peak power more than 400 mW.
In order to develop a wideband 0.22 THz folded-waveguide travelling wave tube, a slow wave structure and RF window are carefully designed. By theoretic analysis and simulation, the tube will work at the point where the dispersion curve is flat and instantaneous bandwidth is more than 16 GHz. In more than 30 GHz, S11 of the RF window is better than -25 dB. The experimental result of the first prototype tube shows that the instantaneous bandwidth is only about 8 GHz. After optimization, the instantaneous bandwidth of the second prototype tube becomes more than 12 GHz with an output peak power more than 400 mW.
2015,
27: 113201.
doi: 10.11884/HPLPB201527.113201
Abstract:
In this paper, the BLT equation is extended to calculate the shielding effectiveness (SE) of arbitrary observation points located in a double layer rectangular enclosure with an aperture on the basis of waveguide theory. Firstly, the surface containing an aperture of enclosure is equivalent to a two-port network, and the enclosure is equivalent to a rectangular waveguide shorted at each end. The signal flow graph can be built according to the equivalent model above. The aperture impedance is employed to calculate the scatter parameters of the two-port network, and the general BLT equation for SE of observation point on center line can be established. Then, the SE of arbitrary observation point can be obtained by using the waveguide theory. Finally, the results from our method are compared with that from CST simulation. The SE from our method reaches a good agreement with CST, and all the resonance frequencies are correctly predicted under 2.5 GHz. Our method takes less time and computer resource compared to CST, and it is helpful for analysis of resonance phenomenon and can easily get the influence of enclosure parameters.
In this paper, the BLT equation is extended to calculate the shielding effectiveness (SE) of arbitrary observation points located in a double layer rectangular enclosure with an aperture on the basis of waveguide theory. Firstly, the surface containing an aperture of enclosure is equivalent to a two-port network, and the enclosure is equivalent to a rectangular waveguide shorted at each end. The signal flow graph can be built according to the equivalent model above. The aperture impedance is employed to calculate the scatter parameters of the two-port network, and the general BLT equation for SE of observation point on center line can be established. Then, the SE of arbitrary observation point can be obtained by using the waveguide theory. Finally, the results from our method are compared with that from CST simulation. The SE from our method reaches a good agreement with CST, and all the resonance frequencies are correctly predicted under 2.5 GHz. Our method takes less time and computer resource compared to CST, and it is helpful for analysis of resonance phenomenon and can easily get the influence of enclosure parameters.
2015,
27: 114001.
doi: 10.11884/HPLPB201527.114001
Abstract:
Beam hardening effect would be induced due to wide energy spectrum of X-ray. One efficient beam hardening correction method is building a mathematical law between poly energetic projection and intersection length, which can be calculated by forward projection in reconstructed images domain. However, for local scanning, the intersection length obtained by forward projection is no longer equal to the real distance at which X-ray passes through the object, and the data of mathematical fit are not valid. Hence, a cylindrical phantom is used. Utilizing the geometrical character of cylinder, the true distance X-ray passing through the object is calculated analytically. Experimental result shows that beam hardening artifacts are suppressed by our approach.
Beam hardening effect would be induced due to wide energy spectrum of X-ray. One efficient beam hardening correction method is building a mathematical law between poly energetic projection and intersection length, which can be calculated by forward projection in reconstructed images domain. However, for local scanning, the intersection length obtained by forward projection is no longer equal to the real distance at which X-ray passes through the object, and the data of mathematical fit are not valid. Hence, a cylindrical phantom is used. Utilizing the geometrical character of cylinder, the true distance X-ray passing through the object is calculated analytically. Experimental result shows that beam hardening artifacts are suppressed by our approach.
2015,
27: 114002.
doi: 10.11884/HPLPB201527.114002
Abstract:
A gate-controlled lateral PNP bipolar transistor has been manufactured by means of depositing a gate electrode on the oxide layer above the active base region of the conventional lateral PNP bipolar transistor, whose base surface potential can be adjusted by changing the bias condition of the gate. Neutron radiation effect experiments have been accomplished on the gate-controlled lateral PNP bipolar transistors whose bias voltage of the gate is zero, -10 V and 10 V respectively to investigate the influence of base surface potential on neutron displacement degradation rate. The experiments have been performed at Xian pulsed reactor and the neutron fluence is 21012, 41012, 61012, 81012, 11013 cm-2, respectively. The results indicate that the increased base surface potential makes the change of the reciprocal of the common emitter current gain degrade with neutron fluence more rapidly and the decreased base surface potential has no obvious influence on the degradation rate.
A gate-controlled lateral PNP bipolar transistor has been manufactured by means of depositing a gate electrode on the oxide layer above the active base region of the conventional lateral PNP bipolar transistor, whose base surface potential can be adjusted by changing the bias condition of the gate. Neutron radiation effect experiments have been accomplished on the gate-controlled lateral PNP bipolar transistors whose bias voltage of the gate is zero, -10 V and 10 V respectively to investigate the influence of base surface potential on neutron displacement degradation rate. The experiments have been performed at Xian pulsed reactor and the neutron fluence is 21012, 41012, 61012, 81012, 11013 cm-2, respectively. The results indicate that the increased base surface potential makes the change of the reciprocal of the common emitter current gain degrade with neutron fluence more rapidly and the decreased base surface potential has no obvious influence on the degradation rate.
2015,
27: 114003.
doi: 10.11884/HPLPB201527.114003
Abstract:
In some cases, a description in terms of bi-Maxwellian distributions is a better mathematical description of space plasma than that in terms of single Maxwellian distributions. To investigate the spacecraft surface charging effect of plasma in bi-Maxwellian distribution, this paper established equilibrium equations of spacecraft surface charging based on kinetic theory of plasma. Considering the plasma particle parameters of bi-Maxwellian distribution, the unit capacitor of spacecraft, the secondary electron emission and photoemission, the expression of spacecraft surface charging potential of plasma in bi-Maxwellian distribution was carried out, and the time evolutions of surface charging potential was got. The research results show that the surface charging potential of plasma in bi-Maxwellian distribution is lower than the surface charging potential of plasma in single Maxwellian distribution, and the assumption of plasma in single Maxwellian distribution will lead an overestimation of surface charging. In the second distribution function of bi-Maxwellian distribution, ion is the main factor which affects the final equilibrium charging potential. The higher the density or the higher the temperature of plasma in bi-Maxwellian distribution, the longer the time which is required for charging potential attaining equilibrium. The unit capacitor only affects the time required for charging potential achieving equilibrium, and it has no influence on the final equilibrium potential.
In some cases, a description in terms of bi-Maxwellian distributions is a better mathematical description of space plasma than that in terms of single Maxwellian distributions. To investigate the spacecraft surface charging effect of plasma in bi-Maxwellian distribution, this paper established equilibrium equations of spacecraft surface charging based on kinetic theory of plasma. Considering the plasma particle parameters of bi-Maxwellian distribution, the unit capacitor of spacecraft, the secondary electron emission and photoemission, the expression of spacecraft surface charging potential of plasma in bi-Maxwellian distribution was carried out, and the time evolutions of surface charging potential was got. The research results show that the surface charging potential of plasma in bi-Maxwellian distribution is lower than the surface charging potential of plasma in single Maxwellian distribution, and the assumption of plasma in single Maxwellian distribution will lead an overestimation of surface charging. In the second distribution function of bi-Maxwellian distribution, ion is the main factor which affects the final equilibrium charging potential. The higher the density or the higher the temperature of plasma in bi-Maxwellian distribution, the longer the time which is required for charging potential attaining equilibrium. The unit capacitor only affects the time required for charging potential achieving equilibrium, and it has no influence on the final equilibrium potential.
2015,
27: 114004.
doi: 10.11884/HPLPB201527.114004
Abstract:
An optical emission spectroscopy method had been applied to diagnose titanium hydride vacuum arc discharge plasmas. Based on the emission spectra theory of the local thermodynamic equilibrium plasma, a plasma emission spectral fitting model was developed to analyse the emission spectra of the vacuum arc discharge plasmas. Comparing the fitting spectral and the observed spectral in the region of 330-340 nm and 498-503 nm respectively, good agreement was found between the predicted and observed spectra. Since this model calculated the summation of Voigt profiles of all spectral lines in the concerned range, it overcame the extraction of intensity and broadening from the overlapped lines by conventional Boltzmann plot method. Furthermore, the emission spectra, density, and temperature of the vacuum arc discharge plasmas under different discharge conditions were studied. The results indicated that the temperature of the TiH vacuum arc discharge plasmas were about 1 eV, and the generated hydrogen atoms were more than the titanium atoms. At the same time, with the increasing feed-in power to vacuum arc ion source discharge, more hydrogen atoms were desorbed from the electrode than the electrode metal atoms erupted, which was benefit for the application of neutron generator.
An optical emission spectroscopy method had been applied to diagnose titanium hydride vacuum arc discharge plasmas. Based on the emission spectra theory of the local thermodynamic equilibrium plasma, a plasma emission spectral fitting model was developed to analyse the emission spectra of the vacuum arc discharge plasmas. Comparing the fitting spectral and the observed spectral in the region of 330-340 nm and 498-503 nm respectively, good agreement was found between the predicted and observed spectra. Since this model calculated the summation of Voigt profiles of all spectral lines in the concerned range, it overcame the extraction of intensity and broadening from the overlapped lines by conventional Boltzmann plot method. Furthermore, the emission spectra, density, and temperature of the vacuum arc discharge plasmas under different discharge conditions were studied. The results indicated that the temperature of the TiH vacuum arc discharge plasmas were about 1 eV, and the generated hydrogen atoms were more than the titanium atoms. At the same time, with the increasing feed-in power to vacuum arc ion source discharge, more hydrogen atoms were desorbed from the electrode than the electrode metal atoms erupted, which was benefit for the application of neutron generator.
2015,
27: 114005.
doi: 10.11884/HPLPB201527.114005
Abstract:
For acquiring multiple physical parameters in one experiment on the SINAP scanning proton microprobe(SPM), the new multifunction signal detection and data acquisition system was developed. The system consists of multiple detectors, multi-stations and multi-parameters data acquisition and beam scanning system, manipulator control and microscope system. Multiple detectors include two Si(Li) detectors for X-rays, a HPGe detector for gamma-rays, and Au(Si) surface barrier detectors for charged particles. The core data acquisition system, named 4LB-Ⅰis based on National Instruments PXI-7852R card and Labview FPGA module. It performs the functions of multi-channel data acquisition, display, beam scanning and two-dimensional images, which can obtain multiple physical parameters simultaneously in one measurement. Six axis vacuum manipulator is computer-controlled for sample positioning and video sample imaging. The initial experiment results show that the system is a powerful tool with good stability and reliability.
For acquiring multiple physical parameters in one experiment on the SINAP scanning proton microprobe(SPM), the new multifunction signal detection and data acquisition system was developed. The system consists of multiple detectors, multi-stations and multi-parameters data acquisition and beam scanning system, manipulator control and microscope system. Multiple detectors include two Si(Li) detectors for X-rays, a HPGe detector for gamma-rays, and Au(Si) surface barrier detectors for charged particles. The core data acquisition system, named 4LB-Ⅰis based on National Instruments PXI-7852R card and Labview FPGA module. It performs the functions of multi-channel data acquisition, display, beam scanning and two-dimensional images, which can obtain multiple physical parameters simultaneously in one measurement. Six axis vacuum manipulator is computer-controlled for sample positioning and video sample imaging. The initial experiment results show that the system is a powerful tool with good stability and reliability.
2015,
27: 114101.
doi: 10.11884/HPLPB201527.114101
Abstract:
Nanostructure deformation on 6H-SiC surface irradiated with highly-charged Xeq+(q=18, 26) ions to different fluences in two geometries of incidence by means of atomic force microscopy has been studied. The AFM measurement reveals that the irradiated surface is swelling. With increasing ion fluences, the step height between the irradiated and the unirradiated regions increases for Xe18+ irradiation. While for Xe26+ the step height firstly increases, and then decreases with increasing ion fluences. Moreover, the step height at normal incidence is higher than that at a tilted incident angle for the same ion and dose. These results can be attributed to the competition between the damage accumulation and the potential sputtering. A preliminary model including potential energy, incident angle, charge state and dose that accounts for the formation of observed nanostructures is proposed to discuss the underlying mechanism and to predict the step height. The paper concludes with suggestions for further research on the work and its potential applications.
Nanostructure deformation on 6H-SiC surface irradiated with highly-charged Xeq+(q=18, 26) ions to different fluences in two geometries of incidence by means of atomic force microscopy has been studied. The AFM measurement reveals that the irradiated surface is swelling. With increasing ion fluences, the step height between the irradiated and the unirradiated regions increases for Xe18+ irradiation. While for Xe26+ the step height firstly increases, and then decreases with increasing ion fluences. Moreover, the step height at normal incidence is higher than that at a tilted incident angle for the same ion and dose. These results can be attributed to the competition between the damage accumulation and the potential sputtering. A preliminary model including potential energy, incident angle, charge state and dose that accounts for the formation of observed nanostructures is proposed to discuss the underlying mechanism and to predict the step height. The paper concludes with suggestions for further research on the work and its potential applications.
2015,
27: 114102.
doi: 10.11884/HPLPB201527.114102
Abstract:
Due to lack of complete set of testing equipment and methods, and no unified evaluation parameters at present, the tool quality can not be comprehensively and systematically tested. The paper proposes a method that can test the roughness value, sharpness value and the range of micro-defect of diamond tool at the same time based on the atomic force microscope and ultra precision aerostatic bearings. In order to meet the measurement requirements for the surface profile of the diamond tools, the measurement system is constructed based on the atomic force microscope, the vibration isolation platform, the 2D mobile platform and the ultra precision aerostatic bearings. The surface morphology of the cutting edge of diamond tool is accurately measured. The roughness value, sharpness value and the range of micro-defect of diamond tool are accurately extracted by special measurement software. The measurement errors are analyzed and the control requirements are proposed. The test system based on above analysis can achieve comprehensive evaluation of multi-parameters, and laid the foundation for the quality evaluation of diamond tool in ultra-precision machining.
Due to lack of complete set of testing equipment and methods, and no unified evaluation parameters at present, the tool quality can not be comprehensively and systematically tested. The paper proposes a method that can test the roughness value, sharpness value and the range of micro-defect of diamond tool at the same time based on the atomic force microscope and ultra precision aerostatic bearings. In order to meet the measurement requirements for the surface profile of the diamond tools, the measurement system is constructed based on the atomic force microscope, the vibration isolation platform, the 2D mobile platform and the ultra precision aerostatic bearings. The surface morphology of the cutting edge of diamond tool is accurately measured. The roughness value, sharpness value and the range of micro-defect of diamond tool are accurately extracted by special measurement software. The measurement errors are analyzed and the control requirements are proposed. The test system based on above analysis can achieve comprehensive evaluation of multi-parameters, and laid the foundation for the quality evaluation of diamond tool in ultra-precision machining.
2015,
27: 115001.
doi: 10.11884/HPLPB201527.115001
Abstract:
In order to meet the requirement of pulsed power source on high voltage and large current switches，a series-connected thyristor switch with a rated voltage of 10 kV and a rated current of 500 A was developed the traditional voltage sharing method. According to the principle of thyristor trigger, a trigger system was developed for synchronous triggering multiple thyristors. As to generate low-voltage pulse with variable pulse widths, the trigger system used an IGBT switch to cut the DC voltage. In the trigger system, the voltage amplitude of the pulse was increased and the synchronous trigger signals were generated through some isolated pulse transformers. Finally, the thyristor trigger system and the series-connected thyristor switch were tested, Showing that the trigger system could produce multi-channel synchronous trigger signals with a voltage of 20 V, a current of 1 A, a pulse repetition rate of 100 Hz and pulse durations from 30 s to 60 s. Static voltage fluctuation and active voltage fluctuation of the series-connected thyristor switch were small, indicating it could reliably work under the condition of high voltage and large current.
In order to meet the requirement of pulsed power source on high voltage and large current switches，a series-connected thyristor switch with a rated voltage of 10 kV and a rated current of 500 A was developed the traditional voltage sharing method. According to the principle of thyristor trigger, a trigger system was developed for synchronous triggering multiple thyristors. As to generate low-voltage pulse with variable pulse widths, the trigger system used an IGBT switch to cut the DC voltage. In the trigger system, the voltage amplitude of the pulse was increased and the synchronous trigger signals were generated through some isolated pulse transformers. Finally, the thyristor trigger system and the series-connected thyristor switch were tested, Showing that the trigger system could produce multi-channel synchronous trigger signals with a voltage of 20 V, a current of 1 A, a pulse repetition rate of 100 Hz and pulse durations from 30 s to 60 s. Static voltage fluctuation and active voltage fluctuation of the series-connected thyristor switch were small, indicating it could reliably work under the condition of high voltage and large current.
2015,
27: 115002.
doi: 10.11884/HPLPB201527.115002
Abstract:
In this paper, we applied the utility of ultrahigh-speed simultaneous framing and streak photography technology in the experiment of magnetic flux compression by cylindrical implosion. For the first time, we obtained the spatio-temporal 1D and 2D images of compression process of magnetic field with high temporal and spatial resolutions using ultrahigh-speed simultaneous framing and streak photography techniques. We observed the whole compression and rebound process. Curves of diameter change with time and the compression speed were obtained. The experiment results shows that the compression process had interface instability and asymmetry phenomena, the whole compression time was 8-10 s, and the whole compression speed was 3.8-4.5 km/s.
In this paper, we applied the utility of ultrahigh-speed simultaneous framing and streak photography technology in the experiment of magnetic flux compression by cylindrical implosion. For the first time, we obtained the spatio-temporal 1D and 2D images of compression process of magnetic field with high temporal and spatial resolutions using ultrahigh-speed simultaneous framing and streak photography techniques. We observed the whole compression and rebound process. Curves of diameter change with time and the compression speed were obtained. The experiment results shows that the compression process had interface instability and asymmetry phenomena, the whole compression time was 8-10 s, and the whole compression speed was 3.8-4.5 km/s.
2015,
27: 115003.
doi: 10.11884/HPLPB201527.115003
Abstract:
According to the difference between electrode erosion rate and erosion mechanism of pulse discharge in water and that in air, a comparative study of tungsten copper electrode erosion characteristics was carried out under high pulse current. Under the uniform waveform of discharge current, using a high precision balance, the cathode erosion rate, anode erosion rate and total erosion rate of tungsten copper electrode were obtained, and the electrode surface was analyzed by ETD and SSD. The results show that the tungsten copper electrode erosion is more serious in water than in air under high pulse current, the erosion of the tungsten copper electrode is mainly caused by the evaporation of metal. Because the incompressibility of water is higher than air, pulse arc discharge in water is more focused, the current density is higher and the current duration time is longer in water than that in air of arc spot, the high temperature physical and electrochemistry reaction caused by pulse discharge in water, is the main cause which leads electrode erosion more serious in water than in air.
According to the difference between electrode erosion rate and erosion mechanism of pulse discharge in water and that in air, a comparative study of tungsten copper electrode erosion characteristics was carried out under high pulse current. Under the uniform waveform of discharge current, using a high precision balance, the cathode erosion rate, anode erosion rate and total erosion rate of tungsten copper electrode were obtained, and the electrode surface was analyzed by ETD and SSD. The results show that the tungsten copper electrode erosion is more serious in water than in air under high pulse current, the erosion of the tungsten copper electrode is mainly caused by the evaporation of metal. Because the incompressibility of water is higher than air, pulse arc discharge in water is more focused, the current density is higher and the current duration time is longer in water than that in air of arc spot, the high temperature physical and electrochemistry reaction caused by pulse discharge in water, is the main cause which leads electrode erosion more serious in water than in air.
2015,
27: 115004.
doi: 10.11884/HPLPB201527.115004
Abstract:
A new conical D-dot probe is designed to measure the electric field wave (rise time less than 2 ns, peak amplitude higher than 50 kV/m) of a high altitude nuclear electromagnetic pulse (HEMP) simulator. The D-dot probe element is introduced in this paper. The design of D-dot is recounted and analyzed. The condition for impedance matching between the D-dot and the transmission cable is analyzed. The configuration and size of probe are confirmed. A signal proportional to the time derivative of pulse electric field is given from the D-dot probe. The electric field is got by a passive RC integrator or a numerical integration. The experiment result proves that the two methods can reconstruct the pulse waveform. The numerical integration is superior to the passive RC integrator. Comparison with the experiment result of the initiative optic transmission measure system indicates that the conical D-dot probe is more suitable for measuring fast rising HEMP signals.
A new conical D-dot probe is designed to measure the electric field wave (rise time less than 2 ns, peak amplitude higher than 50 kV/m) of a high altitude nuclear electromagnetic pulse (HEMP) simulator. The D-dot probe element is introduced in this paper. The design of D-dot is recounted and analyzed. The condition for impedance matching between the D-dot and the transmission cable is analyzed. The configuration and size of probe are confirmed. A signal proportional to the time derivative of pulse electric field is given from the D-dot probe. The electric field is got by a passive RC integrator or a numerical integration. The experiment result proves that the two methods can reconstruct the pulse waveform. The numerical integration is superior to the passive RC integrator. Comparison with the experiment result of the initiative optic transmission measure system indicates that the conical D-dot probe is more suitable for measuring fast rising HEMP signals.
2015,
27: 115005.
doi: 10.11884/HPLPB201527.115005
Abstract:
A compact structure with transformer core and spiral line was discussed in this paper. The core consisted of involute silicon steel sheets. The characteristic parameters, such as slow wave coefficient and wave transmission impedance of spiral line with core, were calculated. The design of the output parameters of the spiral pulse forming line (PFL) with core was given, and the corresponding numerical simulation was carried out. The results showed that in course of slow wave transmission on spiral line with core, inner and outer cylinder currents flowed along the core base. The smaller the radical thickness of core in comparison with radical size is, the less the influence of core on pulse formation is.
A compact structure with transformer core and spiral line was discussed in this paper. The core consisted of involute silicon steel sheets. The characteristic parameters, such as slow wave coefficient and wave transmission impedance of spiral line with core, were calculated. The design of the output parameters of the spiral pulse forming line (PFL) with core was given, and the corresponding numerical simulation was carried out. The results showed that in course of slow wave transmission on spiral line with core, inner and outer cylinder currents flowed along the core base. The smaller the radical thickness of core in comparison with radical size is, the less the influence of core on pulse formation is.
2015,
27: 115101.
doi: 10.11884/HPLPB201527.115101
Abstract:
In linear induction accelerator (LIA), it is common for the intense electron beam time-resolved measurement system to be interfered by some short high-energy pulses. These transient pulses, which may affect both circuits and measurement system, are harmful to the electronic devices. The principle of time-resolved measurement system is introduced in this paper, while the formation causes and the suppression method of transient pulse interferences are analyzed. Arrangement of the beam parameter measurement system is also proposed. The effects on electron devices performance by transient pulse interferences and the preventive measures are discussed, too. By using optical fibers, which effectively reduced the delay jitter of narrow pulses, the reliability requirement of high-speed control signal propagation was fulfilled. To provide better protection for the electronic devices of beam parameter measurements, the anti-electromagnetic interference ability of the system was enhanced by compactly-embedded method. The reliability of the overall measurement system was significantly improved by adopting these measures.
In linear induction accelerator (LIA), it is common for the intense electron beam time-resolved measurement system to be interfered by some short high-energy pulses. These transient pulses, which may affect both circuits and measurement system, are harmful to the electronic devices. The principle of time-resolved measurement system is introduced in this paper, while the formation causes and the suppression method of transient pulse interferences are analyzed. Arrangement of the beam parameter measurement system is also proposed. The effects on electron devices performance by transient pulse interferences and the preventive measures are discussed, too. By using optical fibers, which effectively reduced the delay jitter of narrow pulses, the reliability requirement of high-speed control signal propagation was fulfilled. To provide better protection for the electronic devices of beam parameter measurements, the anti-electromagnetic interference ability of the system was enhanced by compactly-embedded method. The reliability of the overall measurement system was significantly improved by adopting these measures.
2015,
27: 115102.
doi: 10.11884/HPLPB201527.115102
Abstract:
The 10 MeV accelerator of C-ADS injectorⅡmust be run under the liquid helium temperature, hence a helium distribution system has been designed according to the requirement of 10 MeV accelerator operating conditions. The system also has the function ofregulating helium flow and providing liquid helium for vertical and horizontal testing of superconducting cavity and magnet test. The system has been applied to distribution and regulation of liquid helium for cryomodule of 5 MeV accelerator, as well as test of superconducting cavity, and it ran steadily. The paper focuses on the design of liquid helium distribution system, valve box structural design and debugging.
The 10 MeV accelerator of C-ADS injectorⅡmust be run under the liquid helium temperature, hence a helium distribution system has been designed according to the requirement of 10 MeV accelerator operating conditions. The system also has the function ofregulating helium flow and providing liquid helium for vertical and horizontal testing of superconducting cavity and magnet test. The system has been applied to distribution and regulation of liquid helium for cryomodule of 5 MeV accelerator, as well as test of superconducting cavity, and it ran steadily. The paper focuses on the design of liquid helium distribution system, valve box structural design and debugging.
2015,
27: 115103.
doi: 10.11884/HPLPB201527.115103
Abstract:
The influence of the source out of the focused grid on the image in high-energy X-ray radiography is studied by theoretic analysis and numerical simulation. Direct radiation loss fractions under the conditions, such as the lateral decentering, the inclination and the source out of the focused distance, are calculated by analysis. Direct radiation loss fraction under grid manufacture by the stack of foil sheets is obtained. The theoretical results are validated using Monte Carlo code. The results show that the conditions of the grid out of focus toward the source and grid manufacture by the stack of foil sheets are equivalent to devalue the hole diameter, meanwhile the transmission inside the hole is held the line.
The influence of the source out of the focused grid on the image in high-energy X-ray radiography is studied by theoretic analysis and numerical simulation. Direct radiation loss fractions under the conditions, such as the lateral decentering, the inclination and the source out of the focused distance, are calculated by analysis. Direct radiation loss fraction under grid manufacture by the stack of foil sheets is obtained. The theoretical results are validated using Monte Carlo code. The results show that the conditions of the grid out of focus toward the source and grid manufacture by the stack of foil sheets are equivalent to devalue the hole diameter, meanwhile the transmission inside the hole is held the line.
2015,
27: 115104.
doi: 10.11884/HPLPB201527.115104
Abstract:
A one-dimensional full particle PIC model of the double-layer plasma forming process in helicon plasma thruster is established. A kind of electron heating model and plasma expansion model are discussed. And the distribution of double-layer plasma in helicon plasma thruster under different conditions is calculated. The results show that the double-layer plasma can be produced with argon under the condition of RF current of 90 A/m2 and working pressure of 0.05-0.15 Pa. The density is 1.31015-2.81015 m-3 and the potential drop of double-layer plasma is 10-30 V, which can accelerate argon ion beam to 3-12 km/s. Consequently, the double-layer acceleration effect can affect the performance of the thruster.
A one-dimensional full particle PIC model of the double-layer plasma forming process in helicon plasma thruster is established. A kind of electron heating model and plasma expansion model are discussed. And the distribution of double-layer plasma in helicon plasma thruster under different conditions is calculated. The results show that the double-layer plasma can be produced with argon under the condition of RF current of 90 A/m2 and working pressure of 0.05-0.15 Pa. The density is 1.31015-2.81015 m-3 and the potential drop of double-layer plasma is 10-30 V, which can accelerate argon ion beam to 3-12 km/s. Consequently, the double-layer acceleration effect can affect the performance of the thruster.
2015,
27: 119001.
doi: 10.11884/HPLPB201527.119001
Abstract:
In order to improve the wear resistance and high-temperature oxidation resistance of materials surface, MoFeCrTiW high-entropy alloy coating, named MoFeCrTiW HEA coating, was fabricated on Q235 steel by laser cladding. The effect of silicon and aluminum on the microstructure, phase, wear resistance and high-temperature oxidation resistance were studied by X-ray diffraction (XRD), scanning electron microscopy (SEM) and wear tester. The results show that the microstructure of MoFeCrTiW HEA cladding coating is composed of equiaxed grains. After adding equimolar silicon or aluminum respectively, the microstructure of coating is eutectic or dendrites. The microstructure consists of fine equiaxed grains when adding equimolar silicon and aluminum simultaneously. The main phase of HEA coatings is BCC structure. With the addition of silicon and aluminum, the lattice constants of BCC are reduced. Adding equimolar aluminum can contribute to restrain the formation of intermetallic compound and decrease the wear resistance of coatings, whereas adding equimolar silicon can promote the formation of intermetallic compound and some unknown phases, then the wear resistance of coatings can be increased. MoFeCrTiW HEA cladding coating exhibits high oxidation resistance at 800 ℃, the high temperature oxidation of coatings can be further increased after adding silicon and aluminum.
In order to improve the wear resistance and high-temperature oxidation resistance of materials surface, MoFeCrTiW high-entropy alloy coating, named MoFeCrTiW HEA coating, was fabricated on Q235 steel by laser cladding. The effect of silicon and aluminum on the microstructure, phase, wear resistance and high-temperature oxidation resistance were studied by X-ray diffraction (XRD), scanning electron microscopy (SEM) and wear tester. The results show that the microstructure of MoFeCrTiW HEA cladding coating is composed of equiaxed grains. After adding equimolar silicon or aluminum respectively, the microstructure of coating is eutectic or dendrites. The microstructure consists of fine equiaxed grains when adding equimolar silicon and aluminum simultaneously. The main phase of HEA coatings is BCC structure. With the addition of silicon and aluminum, the lattice constants of BCC are reduced. Adding equimolar aluminum can contribute to restrain the formation of intermetallic compound and decrease the wear resistance of coatings, whereas adding equimolar silicon can promote the formation of intermetallic compound and some unknown phases, then the wear resistance of coatings can be increased. MoFeCrTiW HEA cladding coating exhibits high oxidation resistance at 800 ℃, the high temperature oxidation of coatings can be further increased after adding silicon and aluminum.
2015,
27: 119002.
doi: 10.11884/HPLPB201527.119002
Abstract:
The treatment of H2S gas by the atmospheric pressure microwave plasma jet(AMPJ) technology and the AMPJ system were studied. The design of this AMPJ system with special nozzle structure is presented in this paper. The microwave electric field intensity and distribution with different nozzle structures were simulated at the same time. Furthermore, the treatment of H2S gas was discussed. The results show that the new nozzle structure is more conductive to the plasma jet ignition the electric field strength at the position of tip nozzle is above 1.5106 V/m when the microwave power is 500 W, which is higher than the breakdown field strength of the working gases. The maximum conversion of H2S can be up to 91.32% when the ratio of H2S and Ar is 10∶90, and the total flow is 1000 mL/min, as well as the microwave power is 1000 W. The H2S gas can be effectively disposed with the AMPJ system.
The treatment of H2S gas by the atmospheric pressure microwave plasma jet(AMPJ) technology and the AMPJ system were studied. The design of this AMPJ system with special nozzle structure is presented in this paper. The microwave electric field intensity and distribution with different nozzle structures were simulated at the same time. Furthermore, the treatment of H2S gas was discussed. The results show that the new nozzle structure is more conductive to the plasma jet ignition the electric field strength at the position of tip nozzle is above 1.5106 V/m when the microwave power is 500 W, which is higher than the breakdown field strength of the working gases. The maximum conversion of H2S can be up to 91.32% when the ratio of H2S and Ar is 10∶90, and the total flow is 1000 mL/min, as well as the microwave power is 1000 W. The H2S gas can be effectively disposed with the AMPJ system.
2015,
27: 119003.
doi: 10.11884/HPLPB201527.119003
Abstract:
In this paper, based on non-Fouriers heat conduction equation, using the image method and the complex function method, the multiple scattering of the boundaries of the slab material is solved. The temperature field of the thermal wave scattering from two subsurface cylindrical defects in the semi-infinite slab materials is investigated, a general solution of the scattering field of thermal waves is obtained. The frontal surface temperature of the slab materials under different incident wave number, thermal diffusion length, buried depth and the thickness of the slab are analyzed and illustrated graphically. In addition, the thermal waves are excited at frontal surfaces of the slab materials by modulated ultra-short laser pulse with an adiabatic boundary condition for defects. The analytical methods and the numerical results are expected to provide references for the heat transfer analysis of engineering material, the thermal wave imaging, physical inverse problem and non-destructive evaluation of defects in materials.
In this paper, based on non-Fouriers heat conduction equation, using the image method and the complex function method, the multiple scattering of the boundaries of the slab material is solved. The temperature field of the thermal wave scattering from two subsurface cylindrical defects in the semi-infinite slab materials is investigated, a general solution of the scattering field of thermal waves is obtained. The frontal surface temperature of the slab materials under different incident wave number, thermal diffusion length, buried depth and the thickness of the slab are analyzed and illustrated graphically. In addition, the thermal waves are excited at frontal surfaces of the slab materials by modulated ultra-short laser pulse with an adiabatic boundary condition for defects. The analytical methods and the numerical results are expected to provide references for the heat transfer analysis of engineering material, the thermal wave imaging, physical inverse problem and non-destructive evaluation of defects in materials.
2015,
27: 110101.
doi: 10.11884/HPLPB201527.110101
Abstract:
Initial indirect cone-in-shell fast ignition integrated experiment was carried out on Shenguang Ⅱ-updated laser facility. The shaped laser pulses were injected into a hohlraum to compress a cone-in-shell target and achieve a higher density. Then a picosecond laser with hundreds joules energy was guided by a golden cone to irradiate the tip of the cone and generate hot electron flux to heat the compressed deuterium fuel. A maximum neutron yield of 2.2105 was observed at a suitable injection timing of the picosecond laser, which is 44 times larger than that with no picosecond laser injection. These experiment results confirm the heating effect of the picosecond igniting laser.
Initial indirect cone-in-shell fast ignition integrated experiment was carried out on Shenguang Ⅱ-updated laser facility. The shaped laser pulses were injected into a hohlraum to compress a cone-in-shell target and achieve a higher density. Then a picosecond laser with hundreds joules energy was guided by a golden cone to irradiate the tip of the cone and generate hot electron flux to heat the compressed deuterium fuel. A maximum neutron yield of 2.2105 was observed at a suitable injection timing of the picosecond laser, which is 44 times larger than that with no picosecond laser injection. These experiment results confirm the heating effect of the picosecond igniting laser.
2015,
27: 114006.
doi: 10.11884/HPLPB201527.114006
Abstract:
The low laser damage threshold of the diamond like carbon film seriously restricts its application in the infrared laser system. Un-balanced magnetron sputtering was used to deposit a diamond-like carbon (DLC) film on Si substrates. The DLC film was bombarded and processed by ion beam technique, and the main influencing effect factors of the ion beam were determined by the orthogonal experiment method. The DLC films were treated based on the parameters of the ion beam. The optical constants and Raman spectra of the DLC films were observed, and the laser induced damage threshold was performed. It can be seen that the transmittance increased from 60.65% to 65.98%, the extinction coefficient decreased obviously after 900 nm, and the laser damage threshold of the DLC film increased from 0.69 J/cm2 to 1.01 J/cm2.
The low laser damage threshold of the diamond like carbon film seriously restricts its application in the infrared laser system. Un-balanced magnetron sputtering was used to deposit a diamond-like carbon (DLC) film on Si substrates. The DLC film was bombarded and processed by ion beam technique, and the main influencing effect factors of the ion beam were determined by the orthogonal experiment method. The DLC films were treated based on the parameters of the ion beam. The optical constants and Raman spectra of the DLC films were observed, and the laser induced damage threshold was performed. It can be seen that the transmittance increased from 60.65% to 65.98%, the extinction coefficient decreased obviously after 900 nm, and the laser damage threshold of the DLC film increased from 0.69 J/cm2 to 1.01 J/cm2.
2015,
27: 110201.
doi: 10.11884/HPLPB201527.110201
Abstract:
A review of neutron induced single event effects (SEE) on semiconductor devices is presented, with emphasis on research progress with Xian Pulsed Reactor in Northwest Institute of Nuclear Technology. Comparison of steady and pulsed neutron induced SEE is presented. The physical mechanism of increasing susceptibility of SRAM-based integrated circuits with feature size scaling down is analyzed. For CMOS LSI with sub-micron feature size, neutron induced SEE has become the dominant radiation damage mechanism under neutron irradiation. Future work should pay more attention to neutron induced SEE besides displacement damage effects.
A review of neutron induced single event effects (SEE) on semiconductor devices is presented, with emphasis on research progress with Xian Pulsed Reactor in Northwest Institute of Nuclear Technology. Comparison of steady and pulsed neutron induced SEE is presented. The physical mechanism of increasing susceptibility of SRAM-based integrated circuits with feature size scaling down is analyzed. For CMOS LSI with sub-micron feature size, neutron induced SEE has become the dominant radiation damage mechanism under neutron irradiation. Future work should pay more attention to neutron induced SEE besides displacement damage effects.
