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RSS2014 Vol. 26, No. 09
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2014,
26: 090201.
doi: 10.11884/HPLPB201426.090201
Abstract:
The Z-pinch driven fusion-fission hybrid reactor (Z-FFR) concept, proposed by CAEP, utilizes high-energy neutrons produced by Z-pinch driven inertial confinement fusion (ICF) to drive the sub-critical fission reactor for energy release. The Z-FFR innovative concepts such as local-holistic-ignition fusion target and advanced sub-critical power reactor, and it has advantages in security, economy and environment, and might promisingly be a millennial energy source which could effectively solve the climate problem and deal with the energy crisis. This paper introduces the current status of the conceptual research on Z-FFR in CAEP. The principle, structure and operation characteristics of the energy system are expounded in three aspects, the fusion-target design, the low-repetitive Z-pinch driver and the sub-critical fission reactor. The costs of the system are estimated, and the future developmental roadmap is put forward.
The Z-pinch driven fusion-fission hybrid reactor (Z-FFR) concept, proposed by CAEP, utilizes high-energy neutrons produced by Z-pinch driven inertial confinement fusion (ICF) to drive the sub-critical fission reactor for energy release. The Z-FFR innovative concepts such as local-holistic-ignition fusion target and advanced sub-critical power reactor, and it has advantages in security, economy and environment, and might promisingly be a millennial energy source which could effectively solve the climate problem and deal with the energy crisis. This paper introduces the current status of the conceptual research on Z-FFR in CAEP. The principle, structure and operation characteristics of the energy system are expounded in three aspects, the fusion-target design, the low-repetitive Z-pinch driver and the sub-critical fission reactor. The costs of the system are estimated, and the future developmental roadmap is put forward.
2014,
26: 091001.
doi: 10.11884/HPLPB201426.091001
Abstract:
A miniature diode pumped passively Q-switched Er3+ and Yb3+ co-doped phosphate glass laser is reported. The center wavelength of pump source is 940 nm. A Co2+: MgAl2O4 crystal is used as a saturable absorber. When the pump energy is 14 mJ, stable Q-switched pulses are obtained at repetition frequency of 10 Hz and pump pulse width of 5 ms. The output pulse energy of laser is 480 J and pulse width is 5 ns . The wavelength of laser is 1535 nm. The peak power is higher than 20 kW and beam quality is 1.2.
A miniature diode pumped passively Q-switched Er3+ and Yb3+ co-doped phosphate glass laser is reported. The center wavelength of pump source is 940 nm. A Co2+: MgAl2O4 crystal is used as a saturable absorber. When the pump energy is 14 mJ, stable Q-switched pulses are obtained at repetition frequency of 10 Hz and pump pulse width of 5 ms. The output pulse energy of laser is 480 J and pulse width is 5 ns . The wavelength of laser is 1535 nm. The peak power is higher than 20 kW and beam quality is 1.2.
2014,
26: 091002.
doi: 10.11884/HPLPB201426.091002
Abstract:
Time division multiplexing technique was employed and a high repetition frequency of 160 MHz was obtained based on a mode-locked fiber laser with a repetition frequency of 80 MHz. Meanwhile, a high repetition frequency short pulse fiber laser system with an output average power of 105 W, a pulse duration of 12.4 ps and a repetition frequency of 160 MHz was presented experimentally and theoretically employed by large mode area fiber amplifier technique.
Time division multiplexing technique was employed and a high repetition frequency of 160 MHz was obtained based on a mode-locked fiber laser with a repetition frequency of 80 MHz. Meanwhile, a high repetition frequency short pulse fiber laser system with an output average power of 105 W, a pulse duration of 12.4 ps and a repetition frequency of 160 MHz was presented experimentally and theoretically employed by large mode area fiber amplifier technique.
2014,
26: 091003.
doi: 10.11884/HPLPB201426.091003
Abstract:
Measurement methods about beam of laser near field intension distributing is carried out. The measurement methods include direct measurement by CCD and indirect measurement by diffuse reflection screen. As a result, different diffuse reflection screens bring on different measurement results. The great influence on measurement results is because of speckles while measured by indirect measurement. The results of direct measurement are close to real result. The speckles affect measurement result.
Measurement methods about beam of laser near field intension distributing is carried out. The measurement methods include direct measurement by CCD and indirect measurement by diffuse reflection screen. As a result, different diffuse reflection screens bring on different measurement results. The great influence on measurement results is because of speckles while measured by indirect measurement. The results of direct measurement are close to real result. The speckles affect measurement result.
2014,
26: 091004.
doi: 10.11884/HPLPB201426.091004
Abstract:
Aiming at solving detection problem of moving objects in complex scenes that have the features of low contrast and low Signal-to-noise ratio, a polarization imaging detection method based on stable principal component pursuit was proposed. Firstly, a matrix was composed by pre-processed polarization image sequences. Based on correlation of image sequences, stable principal component pursuit mathematical model was build. The matrix could be decomposed to a low-rank matrix, a noise matrix, and a sparse matrix containing object information. Secondly, sparse matrix was achieved using augmented Lagrange multiplier method when the value of object function was sum of nuclear norm of the low-rank matrix and 1 norm of the sparse matrix was the smallest. Finally, Markov random field was used to remove noise in sparse matrix. The experimental results show that the adaptability to complex scenes and the accuracy rate of this method is better than other detection methods.
Aiming at solving detection problem of moving objects in complex scenes that have the features of low contrast and low Signal-to-noise ratio, a polarization imaging detection method based on stable principal component pursuit was proposed. Firstly, a matrix was composed by pre-processed polarization image sequences. Based on correlation of image sequences, stable principal component pursuit mathematical model was build. The matrix could be decomposed to a low-rank matrix, a noise matrix, and a sparse matrix containing object information. Secondly, sparse matrix was achieved using augmented Lagrange multiplier method when the value of object function was sum of nuclear norm of the low-rank matrix and 1 norm of the sparse matrix was the smallest. Finally, Markov random field was used to remove noise in sparse matrix. The experimental results show that the adaptability to complex scenes and the accuracy rate of this method is better than other detection methods.
2014,
26: 091005.
doi: 10.11884/HPLPB201426.091005
Abstract:
The hole defect is one kind of the most common defects for engineering materials. The non-contacting photothermal nondestructive testing is widely used to ensure the safety and reliability of the materials. Based on non-Fourier heat conduction law and employing the methods of wave function expansion, the thermal waves scattering and temperature distribution at the surface of semi-infinite metal material with double subsurface spherical holes were investigated in the paper. The analytical solution and the numerical calculation result of the problem were presented. The effects of geometrical parameters of the defects and the physical parameters on surface temperature distribution of the semi-infinite material were analyzed. The computed results show that the relative thermal diffusion length, the incident wave number and the buried depth have great influences on the surface temperature and the maximum surface temperature. And the thermal wave scattering between the two holes can be ignored when the hole pitch is big enough.
The hole defect is one kind of the most common defects for engineering materials. The non-contacting photothermal nondestructive testing is widely used to ensure the safety and reliability of the materials. Based on non-Fourier heat conduction law and employing the methods of wave function expansion, the thermal waves scattering and temperature distribution at the surface of semi-infinite metal material with double subsurface spherical holes were investigated in the paper. The analytical solution and the numerical calculation result of the problem were presented. The effects of geometrical parameters of the defects and the physical parameters on surface temperature distribution of the semi-infinite material were analyzed. The computed results show that the relative thermal diffusion length, the incident wave number and the buried depth have great influences on the surface temperature and the maximum surface temperature. And the thermal wave scattering between the two holes can be ignored when the hole pitch is big enough.
2014,
26: 091006.
doi: 10.11884/HPLPB201426.091006
Abstract:
EasyLaser is component-based laser system simulation software, which can be used for laser systems with multi-optical paths, multi-wavelength beams and multi-controllers. Beam control system simulation is a main part of EasyLaser. A component framework for beam control simulation is designed, in which optical union transmission of geometry optics and wave optics is the basic part. And kinematic coupling between the rack of system beam director and the inner optical apparatus is also an important part of the simulation framework. A new numerical method is proposed, in which undershoot data and sensor images are updated automatically, and kinematic driver or controller signals are separated automatically. Using the method, the orientation data conversions of rack and many optical mirrors, are executed automatically at every iterative time of the virtual dynamic tracking process. And further optical imaging process and beam controlling process are realized automatically. Therefore the design target for generality, flexibility, and usability of beam control component-based simulation is reached. The tracking and beam controlling can be designed without consideration of the system kinematic composition. In addition, a union beam control example for atmosphere transmission correction is given. It includes tracking tilt mirror and adaptive optics system. Simulation result shows that the low-frequency fluctuation is restrained effectively and the high-frequency fluctuation is corrected obviously.
EasyLaser is component-based laser system simulation software, which can be used for laser systems with multi-optical paths, multi-wavelength beams and multi-controllers. Beam control system simulation is a main part of EasyLaser. A component framework for beam control simulation is designed, in which optical union transmission of geometry optics and wave optics is the basic part. And kinematic coupling between the rack of system beam director and the inner optical apparatus is also an important part of the simulation framework. A new numerical method is proposed, in which undershoot data and sensor images are updated automatically, and kinematic driver or controller signals are separated automatically. Using the method, the orientation data conversions of rack and many optical mirrors, are executed automatically at every iterative time of the virtual dynamic tracking process. And further optical imaging process and beam controlling process are realized automatically. Therefore the design target for generality, flexibility, and usability of beam control component-based simulation is reached. The tracking and beam controlling can be designed without consideration of the system kinematic composition. In addition, a union beam control example for atmosphere transmission correction is given. It includes tracking tilt mirror and adaptive optics system. Simulation result shows that the low-frequency fluctuation is restrained effectively and the high-frequency fluctuation is corrected obviously.
2014,
26: 091007.
doi: 10.11884/HPLPB201426.091007
Abstract:
In order to study the phenomenon and the mechanism of the hard damaged regional expansion of complementary metal oxide semiconductor(CMOS), a 1080 nm continuous wave(CW) laser and a 1064 nm single-pulse ns laser are used to irradiated the front illuminated CMOS, which has a three-stage of hard damage: point damage, half black line damage and black lines cross damage. When irradiated by CW laser, the thermal effects lead to damage. When the duration time is shorter than the thermal balance time, longer duration time leads to lower threshold and the threshold would be a constant when the duration time is longer than the thermal balance time. Observing the micro-structure of damaged CMOS detector and combining the electric structure and working principle of CMOS, we conclude that the half black line damage and black lines cross damage of CMOS irradiated by CW laser are signal short leading by fused metal lines of different layer. But the mechanism of single-pulse laser is different which is mainly induced by thermal effects and plasma impulse wave.
In order to study the phenomenon and the mechanism of the hard damaged regional expansion of complementary metal oxide semiconductor(CMOS), a 1080 nm continuous wave(CW) laser and a 1064 nm single-pulse ns laser are used to irradiated the front illuminated CMOS, which has a three-stage of hard damage: point damage, half black line damage and black lines cross damage. When irradiated by CW laser, the thermal effects lead to damage. When the duration time is shorter than the thermal balance time, longer duration time leads to lower threshold and the threshold would be a constant when the duration time is longer than the thermal balance time. Observing the micro-structure of damaged CMOS detector and combining the electric structure and working principle of CMOS, we conclude that the half black line damage and black lines cross damage of CMOS irradiated by CW laser are signal short leading by fused metal lines of different layer. But the mechanism of single-pulse laser is different which is mainly induced by thermal effects and plasma impulse wave.
2014,
26: 091008.
doi: 10.11884/HPLPB201426.091008
Abstract:
In order to reduce the influence of laser Doppler autonomous velocimeters antenna installation error on velocity measurement accuracy, based on Doppler frequency shift principle, the relationship between installation error and velocity error is derived by the rotation matrix transformation. Influences of the three installation error angles on three-dimensional velocity measurement accuracy are analyzed respectively. After the rotation matrix is linearized by the Bursa model, optimal estimation of installation error angles are proposed by the total least-squares criterion, thus the velocity error compensation could be realized. The simulations show that velocity measurement error increases in proportional with the increment of the speed, the main factor influencing the longitudinal and lateral velocity precision is yaw angle, and the factor of vertical velocity precision is pitch angle, three-dimensional velocity error is significantly reduced after compensation.
In order to reduce the influence of laser Doppler autonomous velocimeters antenna installation error on velocity measurement accuracy, based on Doppler frequency shift principle, the relationship between installation error and velocity error is derived by the rotation matrix transformation. Influences of the three installation error angles on three-dimensional velocity measurement accuracy are analyzed respectively. After the rotation matrix is linearized by the Bursa model, optimal estimation of installation error angles are proposed by the total least-squares criterion, thus the velocity error compensation could be realized. The simulations show that velocity measurement error increases in proportional with the increment of the speed, the main factor influencing the longitudinal and lateral velocity precision is yaw angle, and the factor of vertical velocity precision is pitch angle, three-dimensional velocity error is significantly reduced after compensation.
2014,
26: 091009.
doi: 10.11884/HPLPB201426.091009
Abstract:
The axis of precise optical systems is sensitive to the mount platforms structural deformation and vibration, and the puny structural deformation and vibration are able to directly affect the optical system stability and light-beam alignment precision. This paper analyzes the vibration and noise reduction design defect of traditional rigid connection and spherical joint connecting structure of optical mount platform. By adjusting the mount platforms support and sealing connection, the design of flexible sealed connection between the amount platform and resonator was brought forward. The modal analysis of the double-layer platform frame was carried out with ANSYS finite element method, the beam spot jitter experiment was completed. The modal analysis showed that the first order modal frequencies of the two platforms were increased to 126.5 Hz and 172.3 Hz after optimization with a large folded-cavity. The design adopted the large folded-cavity was tested with a He-Ne laser, the results show that the near-field beam spots typical position and profile changed punily during the resonator box evacuation, and the far-field beam spot jitter angle approached 3.73 (RMS) during the continuous laser operation.
The axis of precise optical systems is sensitive to the mount platforms structural deformation and vibration, and the puny structural deformation and vibration are able to directly affect the optical system stability and light-beam alignment precision. This paper analyzes the vibration and noise reduction design defect of traditional rigid connection and spherical joint connecting structure of optical mount platform. By adjusting the mount platforms support and sealing connection, the design of flexible sealed connection between the amount platform and resonator was brought forward. The modal analysis of the double-layer platform frame was carried out with ANSYS finite element method, the beam spot jitter experiment was completed. The modal analysis showed that the first order modal frequencies of the two platforms were increased to 126.5 Hz and 172.3 Hz after optimization with a large folded-cavity. The design adopted the large folded-cavity was tested with a He-Ne laser, the results show that the near-field beam spots typical position and profile changed punily during the resonator box evacuation, and the far-field beam spot jitter angle approached 3.73 (RMS) during the continuous laser operation.
2014,
26: 091010.
doi: 10.11884/HPLPB201426.091010
Abstract:
Interaction between structures and laser irradiation is a complex multi-physics process with heat-fluid-solid coupling effects. Laser irradiation on a plate in supersonic flow is simulated. Computational fluid dynamics (CFD) and Finite Element Method (FEM) software are adopted, while MPCCI is used to exchange the data between fluid and solid solvers. Moreover, Mach number and attack angle are derived as control parameters using theoretical analysis. Numerical results indicate that the cooling effect is dominant when the Mach number is less than 6, while aerodynamic heating effect is more important when the Mach number is greater than 6. The cooling effect becomes more remarkable as the attack angle increases. Finally, the mechanism of heating and cooling of aerodynamic flow field are analyzed comprehensively.
Interaction between structures and laser irradiation is a complex multi-physics process with heat-fluid-solid coupling effects. Laser irradiation on a plate in supersonic flow is simulated. Computational fluid dynamics (CFD) and Finite Element Method (FEM) software are adopted, while MPCCI is used to exchange the data between fluid and solid solvers. Moreover, Mach number and attack angle are derived as control parameters using theoretical analysis. Numerical results indicate that the cooling effect is dominant when the Mach number is less than 6, while aerodynamic heating effect is more important when the Mach number is greater than 6. The cooling effect becomes more remarkable as the attack angle increases. Finally, the mechanism of heating and cooling of aerodynamic flow field are analyzed comprehensively.
2014,
26: 091011.
doi: 10.11884/HPLPB201426.091011
Abstract:
In order to improve the efficiency of the pressure recovery system (PRS) of high energy chemical laser, a high-fin heat exchanger was designed and manufactured. Instead of the common non-integral finned tubes, copper tubes with integral screwed high fins were adopted. The copper tubes were in staggered arrangement and were forced water-cooled. The heat exchanger was integrated in a chemical laser system and was then tested. Comparative analysis was performed to the efficiency of PRS with and without heat exchanger. The flow resistance of heat exchanger is found to decrease when background pressure increases from 4.03 kPa to 9.366 kPa. When background pressure is 9.366 kPa, flow resistance is 0.133 kPa, which only accounts for 1.4% of the pressure at heat exchanger entrance. Compared with that of PRS without heat exchanger, the pressure at the mixing chamber entrance of PRS with heat exchanger decreases 12.95%, which suggests that the efficiency of PRS is improved with the help of heat exchanger.
In order to improve the efficiency of the pressure recovery system (PRS) of high energy chemical laser, a high-fin heat exchanger was designed and manufactured. Instead of the common non-integral finned tubes, copper tubes with integral screwed high fins were adopted. The copper tubes were in staggered arrangement and were forced water-cooled. The heat exchanger was integrated in a chemical laser system and was then tested. Comparative analysis was performed to the efficiency of PRS with and without heat exchanger. The flow resistance of heat exchanger is found to decrease when background pressure increases from 4.03 kPa to 9.366 kPa. When background pressure is 9.366 kPa, flow resistance is 0.133 kPa, which only accounts for 1.4% of the pressure at heat exchanger entrance. Compared with that of PRS without heat exchanger, the pressure at the mixing chamber entrance of PRS with heat exchanger decreases 12.95%, which suggests that the efficiency of PRS is improved with the help of heat exchanger.
2014,
26: 091012.
doi: 10.11884/HPLPB201426.091012
Abstract:
The scintillation index of partially coherent beam on propagation in atmospheric turbulence is experimentally measured. It is found that the scintillation index of completely coherent beams increases with the increasing of propagation distance in atmospheric turbulence. However, the scintillation index of partially coherent beams may decrease with the increasing of propagation distance. As the correlation length of incident beams becomes shorter, the scintillation index of beams increases more slowly, and even decreases with the increasing of the radial distance.
The scintillation index of partially coherent beam on propagation in atmospheric turbulence is experimentally measured. It is found that the scintillation index of completely coherent beams increases with the increasing of propagation distance in atmospheric turbulence. However, the scintillation index of partially coherent beams may decrease with the increasing of propagation distance. As the correlation length of incident beams becomes shorter, the scintillation index of beams increases more slowly, and even decreases with the increasing of the radial distance.
2014,
26: 091013.
doi: 10.11884/HPLPB201426.091013
Abstract:
Based on the density functional theory and projector augmented wave (PAW) method, a comparative study on the electronic structure and absorption spectra of Cr2+: ZnS and Fe2+: ZnS were carried out. Perdew, Burke, and Ernzerhof (PBE) function was employed for band structure calculation and geometry optimization of divalent ions in crystal. Absorption spectra of Cr2+: ZnS and Fe2+: ZnS show that the characteristic absorption is caused by local excitation from d to p-d hybrid orbitals and the central transition energy in Fe2+: ZnS is lower than in the Cr2+: ZnS, with a value of 0.34 eV. Cr2+: ZnS and Fe2+: ZnS were prepared and the absorption spectra were measured. It is proved that a red shift of 0.34 eV exists in characteristic absorption peaks of Fe2+: ZnS compared to Cr2+: ZnS.
Based on the density functional theory and projector augmented wave (PAW) method, a comparative study on the electronic structure and absorption spectra of Cr2+: ZnS and Fe2+: ZnS were carried out. Perdew, Burke, and Ernzerhof (PBE) function was employed for band structure calculation and geometry optimization of divalent ions in crystal. Absorption spectra of Cr2+: ZnS and Fe2+: ZnS show that the characteristic absorption is caused by local excitation from d to p-d hybrid orbitals and the central transition energy in Fe2+: ZnS is lower than in the Cr2+: ZnS, with a value of 0.34 eV. Cr2+: ZnS and Fe2+: ZnS were prepared and the absorption spectra were measured. It is proved that a red shift of 0.34 eV exists in characteristic absorption peaks of Fe2+: ZnS compared to Cr2+: ZnS.
2014,
26: 091014.
doi: 10.11884/HPLPB201426.091014
Abstract:
All-fiber polarized passively mode-locked thulium-doped fiber laser system operating at 2 m region is presented. Inserting a semiconductor saturable absorber mirror (SESAM) in a Fabry-Perot (F-P) cavity, using master oscillator power amplifier (MOPA) configuration, the laser generated 15.24 ps pulses at repetition rate of 10.24 MHz, with high average power of 1.08 W. The spectrum bandwidth of the 2 m linearly polarized laser output was measured as 0.3 nm, and extinction ratio of the polarized pulses was 24.17 dB.
All-fiber polarized passively mode-locked thulium-doped fiber laser system operating at 2 m region is presented. Inserting a semiconductor saturable absorber mirror (SESAM) in a Fabry-Perot (F-P) cavity, using master oscillator power amplifier (MOPA) configuration, the laser generated 15.24 ps pulses at repetition rate of 10.24 MHz, with high average power of 1.08 W. The spectrum bandwidth of the 2 m linearly polarized laser output was measured as 0.3 nm, and extinction ratio of the polarized pulses was 24.17 dB.
2014,
26: 091015.
doi: 10.11884/HPLPB201426.091015
Abstract:
The passive mode-locked fiber laser based on the nonlinear polarization rotation principle is applied as the master oscillator. The repetition rate and pulse width of the pulse are 30 MHz and 265 fs, respectively. After stretching the pulse width to 100 ps via the chirped fiber Bragg grating, the signal is amplified by one stage of 10 m-core-diameter fiber pre-amplifier and one stage of 50 m-core-diameter fiber power amplifier. The output average power is 10 W with a slope efficiency of 41.5%. And the pulse is compressed to 594 fs via a bulk grating compressor.
The passive mode-locked fiber laser based on the nonlinear polarization rotation principle is applied as the master oscillator. The repetition rate and pulse width of the pulse are 30 MHz and 265 fs, respectively. After stretching the pulse width to 100 ps via the chirped fiber Bragg grating, the signal is amplified by one stage of 10 m-core-diameter fiber pre-amplifier and one stage of 50 m-core-diameter fiber power amplifier. The output average power is 10 W with a slope efficiency of 41.5%. And the pulse is compressed to 594 fs via a bulk grating compressor.
2014,
26: 091016.
doi: 10.11884/HPLPB201426.091016
Abstract:
Motivated by high efficiency, tiny volume and application of new pressure recovery technique of chemical oxygen iodine laser(COIL), cryosorption of oxygen is considered. From the point of view of mass conservation, a linear relation between gaseous pressure gradient and gaseous speed at which gases flow through the zeolite porous bed is obtained, and an adsorption balance equation, describing the relation of the gaseous concentrations, is established with adsorption dynamics equation. Henry relation is employed as an isothermal equation. A set of cryosorption model equations are solved numerically and the relations of oxygen concentration changing with time, and long time character of these concentrations are described. It is found that the adsorption of oxygen in porous bed of COIL develops layer by layer, and at each fixed unit of bed layer, the concentration of absorbed oxygen will rise to the balance value that matches the concentration of oxygen contained in hybrid gases after a long time.
Motivated by high efficiency, tiny volume and application of new pressure recovery technique of chemical oxygen iodine laser(COIL), cryosorption of oxygen is considered. From the point of view of mass conservation, a linear relation between gaseous pressure gradient and gaseous speed at which gases flow through the zeolite porous bed is obtained, and an adsorption balance equation, describing the relation of the gaseous concentrations, is established with adsorption dynamics equation. Henry relation is employed as an isothermal equation. A set of cryosorption model equations are solved numerically and the relations of oxygen concentration changing with time, and long time character of these concentrations are described. It is found that the adsorption of oxygen in porous bed of COIL develops layer by layer, and at each fixed unit of bed layer, the concentration of absorbed oxygen will rise to the balance value that matches the concentration of oxygen contained in hybrid gases after a long time.
2014,
26: 091017.
doi: 10.11884/HPLPB201426.091017
Abstract:
The thermal behaviors of gold film under femtosecond single pulse irradiation and double pulse laser irradiation are calculated by the two-temperature equations. The temporal-spatial distributions of electron temperature and lattice temperature are obtained. At the same laser fluence, than that by the single pulse, the calculated results indicated more laser energy will penetrate into the internal target by the double pulse. The ablation depth will be enhanced. It will help us to improve the efficiency of femtosecond laser ablation of target. The evolution of first melted front is different of single pulse and double pulse ablation with different laser fluence. Near the damage threshold, the ablation depth of single pulse is greater than that of the double pulse. With increasing the laser energy density, the ablation depth of the double pulse is greater than that of the single pulse.
The thermal behaviors of gold film under femtosecond single pulse irradiation and double pulse laser irradiation are calculated by the two-temperature equations. The temporal-spatial distributions of electron temperature and lattice temperature are obtained. At the same laser fluence, than that by the single pulse, the calculated results indicated more laser energy will penetrate into the internal target by the double pulse. The ablation depth will be enhanced. It will help us to improve the efficiency of femtosecond laser ablation of target. The evolution of first melted front is different of single pulse and double pulse ablation with different laser fluence. Near the damage threshold, the ablation depth of single pulse is greater than that of the double pulse. With increasing the laser energy density, the ablation depth of the double pulse is greater than that of the single pulse.
2014,
26: 091018.
doi: 10.11884/HPLPB201426.091018
Abstract:
Nd3+:NaGdF4 nanocrystals dispersed in dimethyl sulfoxide is taken as the green liquid laser medium. Constructing side-pump configuration and transverse liquid flow system, the stable thermal flow field distributions are analyzed by ANSYS software. The results show that when the shape of the flow channel, the flow regime, and the wall surface remain unchanged, the thermal flow field distributions of the liquid are basically the same, and the frequency of pump light has a little effect on streamline distribution; the velocity of the input liquid will affect the distribution of the streamlines, the higher the velocity of input liquid is, the greater the streamline density is. Following the flow direction, the temperature of the medium in the pump area gradually increases, and in the area with constant flow direction of liquid, the temperature distribution is relatively uniform.
Nd3+:NaGdF4 nanocrystals dispersed in dimethyl sulfoxide is taken as the green liquid laser medium. Constructing side-pump configuration and transverse liquid flow system, the stable thermal flow field distributions are analyzed by ANSYS software. The results show that when the shape of the flow channel, the flow regime, and the wall surface remain unchanged, the thermal flow field distributions of the liquid are basically the same, and the frequency of pump light has a little effect on streamline distribution; the velocity of the input liquid will affect the distribution of the streamlines, the higher the velocity of input liquid is, the greater the streamline density is. Following the flow direction, the temperature of the medium in the pump area gradually increases, and in the area with constant flow direction of liquid, the temperature distribution is relatively uniform.
2014,
26: 091019.
doi: 10.11884/HPLPB201426.091019
Abstract:
The amplitude unstability of the 22 optical sampling time division multiplexing systems is investigated. The unstability comes from two aspects: insertion loss differences and various polarization states. Amplitude jitter results from the uneven insertion loss of each level and accumulates step by step. The system requires high insertion loss consistency. Various polarization states are caused by the path diversity. The sampling system can not function properly due to the polarization sensitivity of the electrooptical modulator. To solve the above problems, attenuators and polarization controller are applied to regulating and controlling the amplitude and polarization state of the pulse precisely. The performance is tested through analog signal sampling. The experimental result indicates that the effective number of bits is 2.35 bits.
The amplitude unstability of the 22 optical sampling time division multiplexing systems is investigated. The unstability comes from two aspects: insertion loss differences and various polarization states. Amplitude jitter results from the uneven insertion loss of each level and accumulates step by step. The system requires high insertion loss consistency. Various polarization states are caused by the path diversity. The sampling system can not function properly due to the polarization sensitivity of the electrooptical modulator. To solve the above problems, attenuators and polarization controller are applied to regulating and controlling the amplitude and polarization state of the pulse precisely. The performance is tested through analog signal sampling. The experimental result indicates that the effective number of bits is 2.35 bits.
2014,
26: 091020.
doi: 10.11884/HPLPB201426.091020
Abstract:
We propose a novel method of second harmonic multi-beam laser heterodyne measurement for micro impulse based on oscillating mirror sinusoidal modulation. The measurement of the micro impulse, which is converted into the measurement of the small tuning angle of the torsion pendulum, is realized by measuring the interaction between pulse laser and working medium. Based on Doppler effect and heterodyne technology, loading the information of small tuning angle to the frequency difference of the multi-beam laser heterodyne signal by the frequency modulation of the oscillating mirror, this method can obtain value of small tuning angle after the multi-beam laser heterodyne signal demodulation. Processing the weighted-average of multiple measurements improves the accuracy of small tuning angle values and eventually the precise value of micro impulse is calculated. Using Polyvinylchlorid+2%C as a working medium, this novel method is used to simulate the micro impulse generated by the interaction between the pulse laser and the working medium by MATLAB, the result shows that the relative error of this method is just 0.8%.
We propose a novel method of second harmonic multi-beam laser heterodyne measurement for micro impulse based on oscillating mirror sinusoidal modulation. The measurement of the micro impulse, which is converted into the measurement of the small tuning angle of the torsion pendulum, is realized by measuring the interaction between pulse laser and working medium. Based on Doppler effect and heterodyne technology, loading the information of small tuning angle to the frequency difference of the multi-beam laser heterodyne signal by the frequency modulation of the oscillating mirror, this method can obtain value of small tuning angle after the multi-beam laser heterodyne signal demodulation. Processing the weighted-average of multiple measurements improves the accuracy of small tuning angle values and eventually the precise value of micro impulse is calculated. Using Polyvinylchlorid+2%C as a working medium, this novel method is used to simulate the micro impulse generated by the interaction between the pulse laser and the working medium by MATLAB, the result shows that the relative error of this method is just 0.8%.
2014,
26: 091021.
doi: 10.11884/HPLPB201426.091021
Abstract:
It order to solve the problem of scattering modulation of subsurface damage in optical elements, the transmission process of light beam in the subsurface damage medium is simulated using the finite element method. The effect of different factors on the light scattering characteristics of focused light beam in media with subsurface defects is studied. The information of subsurface damage can be obtained and evaluated through optical field distribution and variation curves of intensity that contain information of subsurface damage. These research results provide an important theoretical guidance for the exploration of high feasibility, practical, quantitative, nondestructive detection technology of the subsurface damage.
It order to solve the problem of scattering modulation of subsurface damage in optical elements, the transmission process of light beam in the subsurface damage medium is simulated using the finite element method. The effect of different factors on the light scattering characteristics of focused light beam in media with subsurface defects is studied. The information of subsurface damage can be obtained and evaluated through optical field distribution and variation curves of intensity that contain information of subsurface damage. These research results provide an important theoretical guidance for the exploration of high feasibility, practical, quantitative, nondestructive detection technology of the subsurface damage.
2014,
26: 091022.
doi: 10.11884/HPLPB201426.091022
Abstract:
Based on spectral beam combining technology, with diffraction grating and external cavity feedback, each element of an array of diode laser is locked at different wavelengths in a narrow linewidth by inserting a beam shaping system. And the output beam is an approximately parallel light along the direction of combination. Beam quality improvement and linewidth narrowing of an array of diode laser are achieved. The standard diode laser array used in our experiment has 19 elements, with a width of 100 m and a period of 500 m for each element. Experiment is conducted on different spectral beam combing setups, including spectral beam combing after collimation in both fast and slow axes, spectral beam combing after beam shaping and beam combing in an external cavity with narrow-line width. The combining output beam has the same beam quality as that of a single emitter and the linewidth of such a beam is narrow. The experiment results are analyzed.
Based on spectral beam combining technology, with diffraction grating and external cavity feedback, each element of an array of diode laser is locked at different wavelengths in a narrow linewidth by inserting a beam shaping system. And the output beam is an approximately parallel light along the direction of combination. Beam quality improvement and linewidth narrowing of an array of diode laser are achieved. The standard diode laser array used in our experiment has 19 elements, with a width of 100 m and a period of 500 m for each element. Experiment is conducted on different spectral beam combing setups, including spectral beam combing after collimation in both fast and slow axes, spectral beam combing after beam shaping and beam combing in an external cavity with narrow-line width. The combining output beam has the same beam quality as that of a single emitter and the linewidth of such a beam is narrow. The experiment results are analyzed.
2014,
26: 091023.
doi: 10.11884/HPLPB201426.091023
Abstract:
The beam quality enhancement in a side-pumped master oscillator power amplifier is experimentally realized by a novel method of spherical aberration compensation. Numerical calculations show that the positive spherical aberration is reversed to a negative one after the beam focus; in addition, the negative spherical aberration can be compensated by another amplifier. A two-stage side-pumped Nd:YAG master oscillator power amplifier has been developed. Seed beam from the oscillator with 42 W CW output power and a beam quality of 1.48 has been boosted up to 74 W after the first amplifier, with a degraded beam quality of 1.80. As expected, the output beam quality has been enhanced to 1.40 after the second amplifier. The experimental results verify the validity of the method to improve the beam quality in the process of laser amplification.
The beam quality enhancement in a side-pumped master oscillator power amplifier is experimentally realized by a novel method of spherical aberration compensation. Numerical calculations show that the positive spherical aberration is reversed to a negative one after the beam focus; in addition, the negative spherical aberration can be compensated by another amplifier. A two-stage side-pumped Nd:YAG master oscillator power amplifier has been developed. Seed beam from the oscillator with 42 W CW output power and a beam quality of 1.48 has been boosted up to 74 W after the first amplifier, with a degraded beam quality of 1.80. As expected, the output beam quality has been enhanced to 1.40 after the second amplifier. The experimental results verify the validity of the method to improve the beam quality in the process of laser amplification.
2014,
26: 091024.
doi: 10.11884/HPLPB201426.091024
Abstract:
The investigation into the laser irradiation effects of composites is important to the development of laser application. An axisymmetric model was proposed to predict the thermal responses of carbon fiber resin composite(CFRC) to laser irradiation in time and space domain. The finite element method was used to solve the governing equation. In this model, the boundary conditions were considered, including laser heat flow, heat convection and heat radiation. The progressive change in thermo-physical properties including decomposition degree, mass transfer, specific heat capacity, and thermal conductivity was determined. A code was developed to predict the transient temperature and thermal decomposing area of composites matrix under laser irradiation, and the results were compared to experimental data. The computed temperatures of composites consist with the experimental measurements well. It was found that when laser intensity was low, the thermal response pattern of CFRC composite was matrix decomposing.
The investigation into the laser irradiation effects of composites is important to the development of laser application. An axisymmetric model was proposed to predict the thermal responses of carbon fiber resin composite(CFRC) to laser irradiation in time and space domain. The finite element method was used to solve the governing equation. In this model, the boundary conditions were considered, including laser heat flow, heat convection and heat radiation. The progressive change in thermo-physical properties including decomposition degree, mass transfer, specific heat capacity, and thermal conductivity was determined. A code was developed to predict the transient temperature and thermal decomposing area of composites matrix under laser irradiation, and the results were compared to experimental data. The computed temperatures of composites consist with the experimental measurements well. It was found that when laser intensity was low, the thermal response pattern of CFRC composite was matrix decomposing.
2014,
26: 091025.
doi: 10.11884/HPLPB201426.091025
Abstract:
The mechanism of femtosecond(fs) laser ablating B2 NiTi alloy have been investigated by the molecular dynamic simulations combined with the two-temperature model. A series of simulations have been conducted, in which ,the laser used is 800 nm in central wavelength, 100 fs in pulse duration, and from 25 mJ/cm2 to 50 mJ/cm2 at fluence. The target is 90 nm in depth. The fluence threshold for 100 fs pulsed laser ablating NiTi shape memory alloy is determined, and it is found that the target irradiated by threshold fluence is ablated wholly due to the tensile and the heat induced phase change area is the smallest. When the fluence is improved, the phase change area expanded.
The mechanism of femtosecond(fs) laser ablating B2 NiTi alloy have been investigated by the molecular dynamic simulations combined with the two-temperature model. A series of simulations have been conducted, in which ,the laser used is 800 nm in central wavelength, 100 fs in pulse duration, and from 25 mJ/cm2 to 50 mJ/cm2 at fluence. The target is 90 nm in depth. The fluence threshold for 100 fs pulsed laser ablating NiTi shape memory alloy is determined, and it is found that the target irradiated by threshold fluence is ablated wholly due to the tensile and the heat induced phase change area is the smallest. When the fluence is improved, the phase change area expanded.
2014,
26: 092001.
doi: 10.11884/HPLPB201426.092001
Abstract:
A radiation simulator utilizing plasma radiation sources will generate large amount of undesirable debris which can potentially damage the frangible diagnosing detectors and the objects under test. An electromagnetically driven fast shutter for purpose of debris mitigation is developed, which erects a physical barrier to slow down the moving debris after allowing the passage of X-ray photons. The shutter system consists of a pair of thin metallic foils twisting the parallel axes, which is imploded by an outer magnetic field generated by a fast capacitor discharging into a single turn loop. Typical capacitor bank charging voltage is 20 kV, with a corresponding current of 80 kA and a discharging current period of 18 microseconds. A closure time as fast as 180 microseconds is observed with the effective cross-sectional area of 40 mm50 mm. The design and operation of the shutter system are described along with the measured results of closure times.
A radiation simulator utilizing plasma radiation sources will generate large amount of undesirable debris which can potentially damage the frangible diagnosing detectors and the objects under test. An electromagnetically driven fast shutter for purpose of debris mitigation is developed, which erects a physical barrier to slow down the moving debris after allowing the passage of X-ray photons. The shutter system consists of a pair of thin metallic foils twisting the parallel axes, which is imploded by an outer magnetic field generated by a fast capacitor discharging into a single turn loop. Typical capacitor bank charging voltage is 20 kV, with a corresponding current of 80 kA and a discharging current period of 18 microseconds. A closure time as fast as 180 microseconds is observed with the effective cross-sectional area of 40 mm50 mm. The design and operation of the shutter system are described along with the measured results of closure times.
2014,
26: 092002.
doi: 10.11884/HPLPB201426.092002
Abstract:
In order to study the influence of guiding cone on radiation symmetry of compressed core, X-ray emission measurements in fast ignition pre-compression were tested on Shenguang Ⅲ prototype facility. Emission images of different targets in hohlraums with the same length and that of the same target in hohlraums with different lengths were recorded. Least-square ellipse fitting was applied to 50% peak intensity contour, thus the ellipse characters could be used to numerically analyze the core compression symmetry at peak emission time. The results validate that the compression symmetry is reduced, as the emission region is stretched in equatorial direction, if the target is attached to a gold cone. The compression symmetry can be adjusted by hohlraum length, as the shape deformations of cone-guide target in hohlraum with 1600 m length is less than that in hohlraums with 1500 m and 1700 m length.
In order to study the influence of guiding cone on radiation symmetry of compressed core, X-ray emission measurements in fast ignition pre-compression were tested on Shenguang Ⅲ prototype facility. Emission images of different targets in hohlraums with the same length and that of the same target in hohlraums with different lengths were recorded. Least-square ellipse fitting was applied to 50% peak intensity contour, thus the ellipse characters could be used to numerically analyze the core compression symmetry at peak emission time. The results validate that the compression symmetry is reduced, as the emission region is stretched in equatorial direction, if the target is attached to a gold cone. The compression symmetry can be adjusted by hohlraum length, as the shape deformations of cone-guide target in hohlraum with 1600 m length is less than that in hohlraums with 1500 m and 1700 m length.
2014,
26: 092003.
doi: 10.11884/HPLPB201426.092003
Abstract:
When we detect the velocity of free surface using imaging velocity interferometer system for any reflector (VISAR) in the shock wave propagation, speckles severely disturb the interference fringe so that it is hard to get the velocity accurately. In this paper, we theoretically analyze two possible factors in terms of optical path that may introduce speckles: roughness of the plat of target and multimode fiber. Then we design three illumination ways to verify these two factors separately in experiment. The result of offline experiment shows that multimode fiber is the main reason for the emergence of speckles and this has instructive value for depressing speckles.
When we detect the velocity of free surface using imaging velocity interferometer system for any reflector (VISAR) in the shock wave propagation, speckles severely disturb the interference fringe so that it is hard to get the velocity accurately. In this paper, we theoretically analyze two possible factors in terms of optical path that may introduce speckles: roughness of the plat of target and multimode fiber. Then we design three illumination ways to verify these two factors separately in experiment. The result of offline experiment shows that multimode fiber is the main reason for the emergence of speckles and this has instructive value for depressing speckles.
2014,
26: 092004.
doi: 10.11884/HPLPB201426.092004
Abstract:
As radiation sources for pumping solid state lasers, xenon flashlamp is a most important optical device in inertial confinement fusion. Experimental study on cutting current tail was carried out. The influences on discharge channel, temperature rise of the flashlamp outside surface, vibration caused by shock wave, fluorescence of neodymium glass were measured. Without the current tail, the effect of plasma on xenon flashlamp inner surface was weakened and the temperature rise of flashlamp outside surface reduced. Meanwhile, cutting more current tail had no effect on shock wave and would lower the output of neodymium fluorescence.
As radiation sources for pumping solid state lasers, xenon flashlamp is a most important optical device in inertial confinement fusion. Experimental study on cutting current tail was carried out. The influences on discharge channel, temperature rise of the flashlamp outside surface, vibration caused by shock wave, fluorescence of neodymium glass were measured. Without the current tail, the effect of plasma on xenon flashlamp inner surface was weakened and the temperature rise of flashlamp outside surface reduced. Meanwhile, cutting more current tail had no effect on shock wave and would lower the output of neodymium fluorescence.
2014,
26: 092005.
doi: 10.11884/HPLPB201426.092005
Abstract:
Aiming at providing new experimental results on the characteristics of the nitrogen laminar plasma jet, experiments were carried out with the laminar plasma jet generated by a self-developed direct-current (DC) non-transfer plasma generator. The experimental results show that the plasma jet, generated by the plasma generator using nitrogen as the working gas, presents a characteristics of high voltage and low current. Such characteristics are helpful for improving the electrodes lifespan of the plasma generator. As the arc current and gas flow rate increase, the length of the plasma jet varies from short to long, and then from long to short. As the length of plasma jet decreases, the morphology of plasma jet changes from relatively concentrated, axisymmetric and stable state to a scattered, non-axisymmetric and unstable state. In other words, the plasma jet changes from laminar to turbulent state. In addition, the noise from the plasma jet gradually increases during this process
Aiming at providing new experimental results on the characteristics of the nitrogen laminar plasma jet, experiments were carried out with the laminar plasma jet generated by a self-developed direct-current (DC) non-transfer plasma generator. The experimental results show that the plasma jet, generated by the plasma generator using nitrogen as the working gas, presents a characteristics of high voltage and low current. Such characteristics are helpful for improving the electrodes lifespan of the plasma generator. As the arc current and gas flow rate increase, the length of the plasma jet varies from short to long, and then from long to short. As the length of plasma jet decreases, the morphology of plasma jet changes from relatively concentrated, axisymmetric and stable state to a scattered, non-axisymmetric and unstable state. In other words, the plasma jet changes from laminar to turbulent state. In addition, the noise from the plasma jet gradually increases during this process
2014,
26: 092006.
doi: 10.11884/HPLPB201426.092006
Abstract:
Magnetic reconnection in Z-pinch plasma have been measured using ultra high speed laser schlieren technology. Through measurement of plasma distribution of two wires on the XP-1, it is demonstrated that study of magnetic reconnection in Z-pinch plasma is feasible through ultra high speed optic electronic framing camera and schlieren technology. The results of two tungsten wire experiment indicate that the wires start expanding 10 ns after current loading at approximately 8 km/s, and in inner and outer sides of the wires, there are highly possible electrothermal instability vertical to magnetic field. The results of two tungsten wire experiment indicate that the early instability wavelength is 0.4 mm and becomes 1.5 mm at later stage, there is still plenty of plasma in the initial position after current peak. These phenomena reveal a principal characteristic of instability: as it develops, the long wave mode will be dominant and the short wave mode will be restrained.
Magnetic reconnection in Z-pinch plasma have been measured using ultra high speed laser schlieren technology. Through measurement of plasma distribution of two wires on the XP-1, it is demonstrated that study of magnetic reconnection in Z-pinch plasma is feasible through ultra high speed optic electronic framing camera and schlieren technology. The results of two tungsten wire experiment indicate that the wires start expanding 10 ns after current loading at approximately 8 km/s, and in inner and outer sides of the wires, there are highly possible electrothermal instability vertical to magnetic field. The results of two tungsten wire experiment indicate that the early instability wavelength is 0.4 mm and becomes 1.5 mm at later stage, there is still plenty of plasma in the initial position after current peak. These phenomena reveal a principal characteristic of instability: as it develops, the long wave mode will be dominant and the short wave mode will be restrained.
2014,
26: 092007.
doi: 10.11884/HPLPB201426.092007
Abstract:
The spatio temporal evolution of current density, electric field and self-generated magnetic field in ultraintense laser-plasma interactions are studied by electromagnetic relativistic particle-in-cell program. The main characteristics of nonlocal electron transport are briefly described for laser-produced plasmas, which include the effects of preheating in overdense region, flux inhabitation near critical surface and anti-diffusion in coronal region. The temporal evolution electron thermal conduction with the self-generated magnetic field description of classical Spitzer-Harm theory is obtained. The numerical simulation result shows that electromagnetic instability is excited in the plasma because of the random thermal motion of electrons under irradiation of the linear polarized femtosecond laser. It is the strong magnetic field excited by instability which makes the electron beam deposit energy within very short distance. Meanwhile, it restrains the electron thermo current when the laser ponderomotive force bursts through the electrons.
The spatio temporal evolution of current density, electric field and self-generated magnetic field in ultraintense laser-plasma interactions are studied by electromagnetic relativistic particle-in-cell program. The main characteristics of nonlocal electron transport are briefly described for laser-produced plasmas, which include the effects of preheating in overdense region, flux inhabitation near critical surface and anti-diffusion in coronal region. The temporal evolution electron thermal conduction with the self-generated magnetic field description of classical Spitzer-Harm theory is obtained. The numerical simulation result shows that electromagnetic instability is excited in the plasma because of the random thermal motion of electrons under irradiation of the linear polarized femtosecond laser. It is the strong magnetic field excited by instability which makes the electron beam deposit energy within very short distance. Meanwhile, it restrains the electron thermo current when the laser ponderomotive force bursts through the electrons.
2014,
26: 092008.
doi: 10.11884/HPLPB201426.092008
Abstract:
In this paper the spontaneous Raman spectrum and stimulated Raman spectrum of potassium dihychogen phosphate (KDP) crystals were compared in detail. In the stimulated Raman spectrum three Stokes lines of the strongest vibration mode, which are 559.43 nm, 589.74 nm, 623.5 nm respectively, were observed. The Stokes lines for other vibration modes didnt appear due to the smaller stimulated Raman scattering (SRS) gain coefficient. In addition, we also compared the gain coefficients of KDP crystal grown by traditional growth method (including annealing and annealing samples) and rapid growth method (including the pyramidal and prismatic sectors samples). The results indicate that the growth method and annealing have no obvious impact on the SRS gain coefficient.
In this paper the spontaneous Raman spectrum and stimulated Raman spectrum of potassium dihychogen phosphate (KDP) crystals were compared in detail. In the stimulated Raman spectrum three Stokes lines of the strongest vibration mode, which are 559.43 nm, 589.74 nm, 623.5 nm respectively, were observed. The Stokes lines for other vibration modes didnt appear due to the smaller stimulated Raman scattering (SRS) gain coefficient. In addition, we also compared the gain coefficients of KDP crystal grown by traditional growth method (including annealing and annealing samples) and rapid growth method (including the pyramidal and prismatic sectors samples). The results indicate that the growth method and annealing have no obvious impact on the SRS gain coefficient.
2014,
26: 092009.
doi: 10.11884/HPLPB201426.092009
Abstract:
In the SG-Ⅲ prototype laser facility, if the lasers narrow bandwidth is adjusted to broadband while maintaining the main configuration, the energy output will decrease. This article evaluates the kilojoule energy output capability of tens-nm broadband laser, using numerical simulation softwares SG99 and CPAP respectively for narrowband and broadband laser propagation and amplification, and the program of one-dimension reverse propagation and amplification. The result shows the growing of gain-narrowing effect under broadband condition. The compensation of gain-narrowing is studied. With compensation, while losing 40% of the input energy, the output energy can reach 2 000~3000 J under 3 J injection. Hence there should be at least 5 J energy output after the preamplifier. This research will conduct the implementation plans for tens-nm broadband 2 laser system.
In the SG-Ⅲ prototype laser facility, if the lasers narrow bandwidth is adjusted to broadband while maintaining the main configuration, the energy output will decrease. This article evaluates the kilojoule energy output capability of tens-nm broadband laser, using numerical simulation softwares SG99 and CPAP respectively for narrowband and broadband laser propagation and amplification, and the program of one-dimension reverse propagation and amplification. The result shows the growing of gain-narrowing effect under broadband condition. The compensation of gain-narrowing is studied. With compensation, while losing 40% of the input energy, the output energy can reach 2 000~3000 J under 3 J injection. Hence there should be at least 5 J energy output after the preamplifier. This research will conduct the implementation plans for tens-nm broadband 2 laser system.
2014,
26: 092010.
doi: 10.11884/HPLPB201426.092010
Abstract:
The subsurface damage of ground K9 specimens and the damage mechanism are studied in this paper. Subsurface damage prediction method and step-by-step etching method are used to measure subsurface damage depth. In addition, cutting depth, feed rate and wheel speed are discussed about the influences on subsurface damage depth. Studies show that, step-by-step etching method is intuitive and effective. For the K9 specimens ground by ourselves, under the experimental conditions in this paper, subsurface damage depth will increase with cutting depth getting deeper or when the feed rate increases. However, wheel speed has no specific influence on subsurface damage depth.
The subsurface damage of ground K9 specimens and the damage mechanism are studied in this paper. Subsurface damage prediction method and step-by-step etching method are used to measure subsurface damage depth. In addition, cutting depth, feed rate and wheel speed are discussed about the influences on subsurface damage depth. Studies show that, step-by-step etching method is intuitive and effective. For the K9 specimens ground by ourselves, under the experimental conditions in this paper, subsurface damage depth will increase with cutting depth getting deeper or when the feed rate increases. However, wheel speed has no specific influence on subsurface damage depth.
2014,
26: 092011.
doi: 10.11884/HPLPB201426.092011
Abstract:
In order to research the influence of scratch defects on the quality of beam field in the high power laser system, the non-linear paraxial wave equation is calculated with the split-step-Fourier-transform method. With different parameters of scratch defects, the intensity distribution of the beam field is obtained by using numerical simulation. The simulation results show that the maximum and the contrast of the beam field intensity inside or behind optics increase with the increase of the length, width or depth of the scratch defect. The contrast of the intensity distribution of beam near-field also increases. For the intensity distribution of beam far-field, the spectrum energy corresponding to the width direction of the scratch is enhanced. The study can provide some quantitative analysis bases for the setting of the scratch detection criterion.
In order to research the influence of scratch defects on the quality of beam field in the high power laser system, the non-linear paraxial wave equation is calculated with the split-step-Fourier-transform method. With different parameters of scratch defects, the intensity distribution of the beam field is obtained by using numerical simulation. The simulation results show that the maximum and the contrast of the beam field intensity inside or behind optics increase with the increase of the length, width or depth of the scratch defect. The contrast of the intensity distribution of beam near-field also increases. For the intensity distribution of beam far-field, the spectrum energy corresponding to the width direction of the scratch is enhanced. The study can provide some quantitative analysis bases for the setting of the scratch detection criterion.
2014,
26: 092012.
doi: 10.11884/HPLPB201426.092012
Abstract:
This paper analyzes characteristics of wavefront and light intensity of large-aperture continuous phase plates(CPPs) fabricated by magnetorheological finishing(MRF). Three groups of CPPs fabricated by different processing parameters such as scanning intervals and scanning offsets are compared, and the influence of mid-frequency error introduced by MRF on CPPs wavefront and light intensity are analyzed as well. Total analysis indicates that the performance of CPP is poor when scanning interval is 2 mm and scanning offsets are 0.1-0.3 mm; The iteration fabrication efficiency is higher when scanning interval is 2 mm and scanning offsets are 0.4-0.5 mm compared with that when scanning interval is 1 mm and scanning offsets are 0.1-0.3 mm, and the mid-frequency error is improved as well. Further analysis indicates that mid-frequency error introduced by MRF has a greater impact on CPPs wavefront gradient, near-field and side lobe.
This paper analyzes characteristics of wavefront and light intensity of large-aperture continuous phase plates(CPPs) fabricated by magnetorheological finishing(MRF). Three groups of CPPs fabricated by different processing parameters such as scanning intervals and scanning offsets are compared, and the influence of mid-frequency error introduced by MRF on CPPs wavefront and light intensity are analyzed as well. Total analysis indicates that the performance of CPP is poor when scanning interval is 2 mm and scanning offsets are 0.1-0.3 mm; The iteration fabrication efficiency is higher when scanning interval is 2 mm and scanning offsets are 0.4-0.5 mm compared with that when scanning interval is 1 mm and scanning offsets are 0.1-0.3 mm, and the mid-frequency error is improved as well. Further analysis indicates that mid-frequency error introduced by MRF has a greater impact on CPPs wavefront gradient, near-field and side lobe.
2014,
26: 092013.
doi: 10.11884/HPLPB201426.092013
Abstract:
New polyphosphazene organic photorefractive materials with carbazole groups were synthesized by diazo-coupling reaction. They were characterized by 1H Nuclear magnetic resonance，infrared spectrum，Ultra-violet-visible，thermogravimetry and differential scanning calorimetry. The result showed that polymers had good heating stability. They started to decompose at 230 ℃ and decomposed completely at 450 ℃. UV-Vis indicated that the broad absorption peak ranging from 360 to 570 nm was derived from the increase in the conjugation length. Hence we can adjust the ratio of diazonium salt in the coupling reaction to control the access content of azo chromophore functional component. The photorefractive effects were investigated without electric field and polarization by two-beam coupling (2BC) and degenerated four-wave mixing(DFWM).The coupling coefficients of polymers P-2 and P-3 are measured to be about 38 cm-1 and 53.6 cm-1 respectively and the diffraction efficiencies of polymers P-2 and P-3 are measured to be about 2.7% and 8.1% respectively.
New polyphosphazene organic photorefractive materials with carbazole groups were synthesized by diazo-coupling reaction. They were characterized by 1H Nuclear magnetic resonance，infrared spectrum，Ultra-violet-visible，thermogravimetry and differential scanning calorimetry. The result showed that polymers had good heating stability. They started to decompose at 230 ℃ and decomposed completely at 450 ℃. UV-Vis indicated that the broad absorption peak ranging from 360 to 570 nm was derived from the increase in the conjugation length. Hence we can adjust the ratio of diazonium salt in the coupling reaction to control the access content of azo chromophore functional component. The photorefractive effects were investigated without electric field and polarization by two-beam coupling (2BC) and degenerated four-wave mixing(DFWM).The coupling coefficients of polymers P-2 and P-3 are measured to be about 38 cm-1 and 53.6 cm-1 respectively and the diffraction efficiencies of polymers P-2 and P-3 are measured to be about 2.7% and 8.1% respectively.
2014,
26: 093001.
doi: 10.11884/HPLPB201426.093001
Abstract:
Based on the mode matching method, the reflection and transmission problems of high order modes are analyzed in the high power over-mode circular waveguide to two-way rectangular waveguide power divider during transmission process. The requirement on the over-mode circular waveguide to realize high transmission efficiency is obtained. The power divider is designed at a center frequency 2.88 GHz. The result shows that at the center frequency, the reflection coefficient is about 0.05, the corresponding conversion efficiency of circular waveguide TM01 mode to rectangular waveguide TE10 mode is over 99%, and the power-handling capacity can reach 2.83 GW in vacuum state. In the frequency range of 2.82-2.94 GHz, the reflection coefficient is less than 0.1, and the corresponding transmission efficiency is more than 98%.
Based on the mode matching method, the reflection and transmission problems of high order modes are analyzed in the high power over-mode circular waveguide to two-way rectangular waveguide power divider during transmission process. The requirement on the over-mode circular waveguide to realize high transmission efficiency is obtained. The power divider is designed at a center frequency 2.88 GHz. The result shows that at the center frequency, the reflection coefficient is about 0.05, the corresponding conversion efficiency of circular waveguide TM01 mode to rectangular waveguide TE10 mode is over 99%, and the power-handling capacity can reach 2.83 GW in vacuum state. In the frequency range of 2.82-2.94 GHz, the reflection coefficient is less than 0.1, and the corresponding transmission efficiency is more than 98%.
2014,
26: 093002.
doi: 10.11884/HPLPB201426.093002
Abstract:
In this paper, a highly sensitive waveguide-type high power microwave (HPM) detector using a vacuum diode is designed, manufactured and experimented, aiming at directly measuring the HPM pulses at X-band. It consists of a WR-90 waveguide, a 6D16D vacuum diode, a low-pass filter andthree tuning screws. Our experiments at 9.3 GHz show that the detector can detect about 40 dB greater pulsed microwave power up to 10 kW compared with crystal diodes, its response time is less than 2 ns, the large output signal from the detector is available (up to 7 V/kW), and it can reliably operate free from electromagnetic interference at free space power density more than 2 kW/cm2.
In this paper, a highly sensitive waveguide-type high power microwave (HPM) detector using a vacuum diode is designed, manufactured and experimented, aiming at directly measuring the HPM pulses at X-band. It consists of a WR-90 waveguide, a 6D16D vacuum diode, a low-pass filter andthree tuning screws. Our experiments at 9.3 GHz show that the detector can detect about 40 dB greater pulsed microwave power up to 10 kW compared with crystal diodes, its response time is less than 2 ns, the large output signal from the detector is available (up to 7 V/kW), and it can reliably operate free from electromagnetic interference at free space power density more than 2 kW/cm2.
2014,
26: 093201.
doi: 10.11884/HPLPB201426.093201
Abstract:
Based on the given temporal and energy spectrum of photoelectrons, the generation of an SGEMP (system generated electromagnetic pulse） induced by photoelectrons emitted from the bounded metal plate to free space is analyzed. The spatial motion characteristics and the distribution of photoelectrons, as well as the composition and the characteristics of the electromagnetic field are simulated by using a 2.5D PIC (particle-in-cell) code. It is shown that the simulated SGEMP field is composed of two parts: one is the quasi-DC background field and the other is a radiation field. The quasi-DC field is a radial field, attenuating quite rapidly with the distance from the emitted source. While the radiation field is also composed of two parts: one is the super-radiation field produced during electron emission from the metal plate and the other is the normal radiation field produced in the process of photoelectron motion in space. The characteristics of the two kinds of radiation field are investigated.
Based on the given temporal and energy spectrum of photoelectrons, the generation of an SGEMP (system generated electromagnetic pulse） induced by photoelectrons emitted from the bounded metal plate to free space is analyzed. The spatial motion characteristics and the distribution of photoelectrons, as well as the composition and the characteristics of the electromagnetic field are simulated by using a 2.5D PIC (particle-in-cell) code. It is shown that the simulated SGEMP field is composed of two parts: one is the quasi-DC background field and the other is a radiation field. The quasi-DC field is a radial field, attenuating quite rapidly with the distance from the emitted source. While the radiation field is also composed of two parts: one is the super-radiation field produced during electron emission from the metal plate and the other is the normal radiation field produced in the process of photoelectron motion in space. The characteristics of the two kinds of radiation field are investigated.
2014,
26: 094001.
doi: 10.11884/HPLPB201426.094001
Abstract:
The thermo-mechanical response of materials is an important basis for evaluating the resistance ability of materials to nuclear explosion X rays resistance. Electron beam irradiation is used to study the thermo-mechanical response of materials in laboratory and to evaluate resistance ability of materials to nuclear explosion X rays. Neglecting the difference between electron beam and X rays, this method will cause biases. MCNP and the least square method are used to optimize electron spectra for simulating the energy deposition profiles caused by 1 keV and 3 keV X rays in aluminum, copper and tantalum. The results show that it can get the same energy deposition profiles as X rays do, which can be used to evaluate resistance ability of materials to nuclear explosion X-rays, but in these processes, X rays spectrum and materials should be taken into account.
The thermo-mechanical response of materials is an important basis for evaluating the resistance ability of materials to nuclear explosion X rays resistance. Electron beam irradiation is used to study the thermo-mechanical response of materials in laboratory and to evaluate resistance ability of materials to nuclear explosion X rays. Neglecting the difference between electron beam and X rays, this method will cause biases. MCNP and the least square method are used to optimize electron spectra for simulating the energy deposition profiles caused by 1 keV and 3 keV X rays in aluminum, copper and tantalum. The results show that it can get the same energy deposition profiles as X rays do, which can be used to evaluate resistance ability of materials to nuclear explosion X-rays, but in these processes, X rays spectrum and materials should be taken into account.
2014,
26: 094002.
doi: 10.11884/HPLPB201426.094002
Abstract:
To decrease the significant assay mass bias of spherical shell plutonium samples in nuclear disarmament verification and increase the confidence of verification results, the failure of assumptions in point model equations was studied. Doubles factorial and triples factorial correction factors for spontaneous fission neutrons and oxide generated neutrons were then introduced into the point model equations. The relationships between the correction factors and the sample mass and multiplication were derived with Monte Carlo calculation, and the corrected equations were solved by an iteration process. The calculation results show that: compared with the point model assay, the corrected point model assay decreases the average assay mass bias from -4.70% to -0.70%, and average assay alpha bias from 11.45% to 2.31%.
To decrease the significant assay mass bias of spherical shell plutonium samples in nuclear disarmament verification and increase the confidence of verification results, the failure of assumptions in point model equations was studied. Doubles factorial and triples factorial correction factors for spontaneous fission neutrons and oxide generated neutrons were then introduced into the point model equations. The relationships between the correction factors and the sample mass and multiplication were derived with Monte Carlo calculation, and the corrected equations were solved by an iteration process. The calculation results show that: compared with the point model assay, the corrected point model assay decreases the average assay mass bias from -4.70% to -0.70%, and average assay alpha bias from 11.45% to 2.31%.
2014,
26: 094003.
doi: 10.11884/HPLPB201426.094003
Abstract:
In order to reduce Am-Li neutron background that had affected active neutron multiplicity assay for highly enriched uranium, optimization shielding of Am-Li was simulated for New Pile Laboratory-Neutron Multiplicity Counter (NPL-NMC). A cylindrical high density polyethylene was chosen as neutron shield with the radius of 15 cm. By comparing simulation results with the shielding to experimental results without the shielding, the Am-Li neutron background detection efficiency was significantly reduced, from 15.77% to 1.94%, reducing by about 87.7%. But shielding effect on fission neutron count was relatively small, only about 2.4% lower than the original. Reducing of the background neutron counts significantly improved the mass measurement sensitivity of uranium components. Mass measurement limit of uranium components dropped to 2.6 kg from the original about 6.4 kg with 3000 s counting time. Meanwhile, the measurement accuracy of uranium components was significantly improved in NPL-NMC, which could be increased by 50% under the same measurement conditions.
In order to reduce Am-Li neutron background that had affected active neutron multiplicity assay for highly enriched uranium, optimization shielding of Am-Li was simulated for New Pile Laboratory-Neutron Multiplicity Counter (NPL-NMC). A cylindrical high density polyethylene was chosen as neutron shield with the radius of 15 cm. By comparing simulation results with the shielding to experimental results without the shielding, the Am-Li neutron background detection efficiency was significantly reduced, from 15.77% to 1.94%, reducing by about 87.7%. But shielding effect on fission neutron count was relatively small, only about 2.4% lower than the original. Reducing of the background neutron counts significantly improved the mass measurement sensitivity of uranium components. Mass measurement limit of uranium components dropped to 2.6 kg from the original about 6.4 kg with 3000 s counting time. Meanwhile, the measurement accuracy of uranium components was significantly improved in NPL-NMC, which could be increased by 50% under the same measurement conditions.
2014,
26: 094004.
doi: 10.11884/HPLPB201426.094004
Abstract:
Accurate measurements of an intense high energy proton beam are generally disturbed by high energy proton induced secondary electron emission. In the present work, a compensation coaxial Faraday cup has been designed according to the compensation mechanism for secondary electron emission. The reason of the uncertainty for measuring proton beam intensity has been investigated. It is that the difference between the forward electron emission field and backward electron emission yield from compensation plate. The experiment is carried out at EN 26 accelerator in Peking University to measure the forward and backward electron emission yields from cupper foils penetrated by high energy proton in the energy ranging from 5 MeV to 10 MeV. The ratio of the forward electron emission yield to the backward electron emission yield is 1.3 as high energy proton penetrates a 10 m thick cupper foil. The results are in excellent agreement with the simulation results.
Accurate measurements of an intense high energy proton beam are generally disturbed by high energy proton induced secondary electron emission. In the present work, a compensation coaxial Faraday cup has been designed according to the compensation mechanism for secondary electron emission. The reason of the uncertainty for measuring proton beam intensity has been investigated. It is that the difference between the forward electron emission field and backward electron emission yield from compensation plate. The experiment is carried out at EN 26 accelerator in Peking University to measure the forward and backward electron emission yields from cupper foils penetrated by high energy proton in the energy ranging from 5 MeV to 10 MeV. The ratio of the forward electron emission yield to the backward electron emission yield is 1.3 as high energy proton penetrates a 10 m thick cupper foil. The results are in excellent agreement with the simulation results.
2014,
26: 094005.
doi: 10.11884/HPLPB201426.094005
Abstract:
An efficiency transfer code based on disk source is established to calibrate efficiency of 133Xe gas sample. 133Ba disk sources were used to simulate the detection efficiency of 133Xe cylindrical volume source. Relationships were established based on peak efficiency ratio between 137Cs and 133Ba. Cascade summing effects in close geometry gamma-ray spectrum of 133Ba was solved based on the ratios calculated by LabSOCS simulation and the experiment data of long and short distances. Finally, the efficiency transfer code is used to calibrate 133Xe gas samples efficiency. The detection efficiencies using the efficiency transfer code are consistent with the results of disk source simulation with discrepancy about 1％.
An efficiency transfer code based on disk source is established to calibrate efficiency of 133Xe gas sample. 133Ba disk sources were used to simulate the detection efficiency of 133Xe cylindrical volume source. Relationships were established based on peak efficiency ratio between 137Cs and 133Ba. Cascade summing effects in close geometry gamma-ray spectrum of 133Ba was solved based on the ratios calculated by LabSOCS simulation and the experiment data of long and short distances. Finally, the efficiency transfer code is used to calibrate 133Xe gas samples efficiency. The detection efficiencies using the efficiency transfer code are consistent with the results of disk source simulation with discrepancy about 1％.
2014,
26: 094006.
doi: 10.11884/HPLPB201426.094006
Abstract:
The energy responses of gamma rays from 50 keV to 10 MeV of a spherical counter filled with 1 MPa hydrogen and with a 30 mm diameter have been obtained by experimental measurement and Monte Carlo simulation. It shows that the energy deposited in the counter is focused near 100 keV and below. An experiment with Am-Be source and 137Cs source indicates that intense gamma rays of the 137Cs source have made great influence on the measurement of the neutrons spectra below 100 keV from Am-Be source. It can be concluded that the measurement of neutron spectra below 100 keV from fissionable materials would be affected by the intense gamma rays. According to the collective features of recoil protons and electrons ionization in the counter, it is feasible to discriminate the gamma rays from the neutrons by rise-time method.
The energy responses of gamma rays from 50 keV to 10 MeV of a spherical counter filled with 1 MPa hydrogen and with a 30 mm diameter have been obtained by experimental measurement and Monte Carlo simulation. It shows that the energy deposited in the counter is focused near 100 keV and below. An experiment with Am-Be source and 137Cs source indicates that intense gamma rays of the 137Cs source have made great influence on the measurement of the neutrons spectra below 100 keV from Am-Be source. It can be concluded that the measurement of neutron spectra below 100 keV from fissionable materials would be affected by the intense gamma rays. According to the collective features of recoil protons and electrons ionization in the counter, it is feasible to discriminate the gamma rays from the neutrons by rise-time method.
2014,
26: 095001.
doi: 10.11884/HPLPB201426.095001
Abstract:
Design theory and method was discussed about the low jitter fast fall time and repetitive high voltage pulsed trigger. The trigger met the following design specifications: pulse voltage up to 20 kV, fall time less than 10 ns, width more than 500 ns and jitter less than 1 ns. Using program control and manual control, repetitive model and single model were got respectively. The finally high voltage pulse was received through IGBT and VE4141 thyratron. The experimental results testified the feasibility of the design theory and method.
Design theory and method was discussed about the low jitter fast fall time and repetitive high voltage pulsed trigger. The trigger met the following design specifications: pulse voltage up to 20 kV, fall time less than 10 ns, width more than 500 ns and jitter less than 1 ns. Using program control and manual control, repetitive model and single model were got respectively. The finally high voltage pulse was received through IGBT and VE4141 thyratron. The experimental results testified the feasibility of the design theory and method.
2014,
26: 095002.
doi: 10.11884/HPLPB201426.095002
Abstract:
Differential-output capacitive divider(D-dot probes) and current loops (B-dot probes) were designed and calibrated to derive vacuum insulator stack voltage and current in the PTS facility. Frequency response experiments indicated that the D-dots upper limiting frequency was 270 MHz and B-dots was 100 MHz. All the monitors were calibrated in-situ. The water outside the insulator stack was present to keep the distribution of D-dot probes electric field. The experimental results showed that the voltage and current of insulator stack were reasonable according to theoretical predictions. And the results of measurement and magnetically insulated transmission line(MITL) current were self-consistent. But large variations in the monitor signals which were contributed from asymmetric current distribution azimuthally compromised the accuracy of azimuthal averages calculated from the signals.
Differential-output capacitive divider(D-dot probes) and current loops (B-dot probes) were designed and calibrated to derive vacuum insulator stack voltage and current in the PTS facility. Frequency response experiments indicated that the D-dots upper limiting frequency was 270 MHz and B-dots was 100 MHz. All the monitors were calibrated in-situ. The water outside the insulator stack was present to keep the distribution of D-dot probes electric field. The experimental results showed that the voltage and current of insulator stack were reasonable according to theoretical predictions. And the results of measurement and magnetically insulated transmission line(MITL) current were self-consistent. But large variations in the monitor signals which were contributed from asymmetric current distribution azimuthally compromised the accuracy of azimuthal averages calculated from the signals.
2014,
26: 095003.
doi: 10.11884/HPLPB201426.095003
Abstract:
Based on the one-dimensional elastic-plastic reactive hydrodynamic code SSS, the one-dimensional magneto-hydrodynamic code SSS/MHD is successfully developed. And calculation is done for cylindrical magneto cumulative generators (MC-1 device). The magnetic field diffusion into liner and sample tuber is analyzed, and the result shows that the maximum value of magnetic induction intension to cavity 0.2 mm in liner is only sixteen Tesla, while the one in sample tuber is several hundred Tesla, which is caused by balance of electromagnetism force and imploding one for the different velocity of liner and sample tuber. The curves of magnetic induction intension on axes of cavity and the velocity history on the wall of sample tuber are calculated according to the experiment results. The works in this paper accounting for that code SSS/MHD can be applied to experiment configures of detonation, shock and electromagnetism load and improvement of parameters. The experiment data can be estimated, analyzed and checked, and the physics course of correlative device can be understood deeply, according to SSS/MHD.
Based on the one-dimensional elastic-plastic reactive hydrodynamic code SSS, the one-dimensional magneto-hydrodynamic code SSS/MHD is successfully developed. And calculation is done for cylindrical magneto cumulative generators (MC-1 device). The magnetic field diffusion into liner and sample tuber is analyzed, and the result shows that the maximum value of magnetic induction intension to cavity 0.2 mm in liner is only sixteen Tesla, while the one in sample tuber is several hundred Tesla, which is caused by balance of electromagnetism force and imploding one for the different velocity of liner and sample tuber. The curves of magnetic induction intension on axes of cavity and the velocity history on the wall of sample tuber are calculated according to the experiment results. The works in this paper accounting for that code SSS/MHD can be applied to experiment configures of detonation, shock and electromagnetism load and improvement of parameters. The experiment data can be estimated, analyzed and checked, and the physics course of correlative device can be understood deeply, according to SSS/MHD.
2014,
26: 095004.
doi: 10.11884/HPLPB201426.095004
Abstract:
In order to get a high-power, heat resistant, high strength rail-type electromagnetic launcher, the working performance of a pulsed current electromagnetic rail launcher was analyzed to determine the inductance gradient and flow capacity. The electromagnetic force, armature, and screw pre-tightening force under combined action of mechanical characteristics of the electromagnetic rail-launcher were analyzed, from which appropriate conclusions were drawn to gather further insight on how a rail-type electromagnetic-launcher works to lay the foundations of the mechanism.
In order to get a high-power, heat resistant, high strength rail-type electromagnetic launcher, the working performance of a pulsed current electromagnetic rail launcher was analyzed to determine the inductance gradient and flow capacity. The electromagnetic force, armature, and screw pre-tightening force under combined action of mechanical characteristics of the electromagnetic rail-launcher were analyzed, from which appropriate conclusions were drawn to gather further insight on how a rail-type electromagnetic-launcher works to lay the foundations of the mechanism.
2014,
26: 095006.
doi: 10.11884/HPLPB201426.095006
Abstract:
This paper presents a high power no matching transmission line based on chopping-peaking switch,and studies its operating principles. The effects of the switch break-over time, the switch break-over time-delay and the length of the no matching transmission line on the result of output wide-spectrum pulse are analyzed. A high power no matching transmission line is designed accordingly and high voltage experiments are conducted on the 500 kV Marx generation. The no matching transmission line can output wide-spectrum pulse with a peak power of 3.3 GW, a center frequency of 169 MHz, a band width of 22.9% when the chopping switch space is 4 mm with 1.15 MPa SF6 and the peaking switch space is 2.5 mm with 1.0 MPa SF6.
This paper presents a high power no matching transmission line based on chopping-peaking switch,and studies its operating principles. The effects of the switch break-over time, the switch break-over time-delay and the length of the no matching transmission line on the result of output wide-spectrum pulse are analyzed. A high power no matching transmission line is designed accordingly and high voltage experiments are conducted on the 500 kV Marx generation. The no matching transmission line can output wide-spectrum pulse with a peak power of 3.3 GW, a center frequency of 169 MHz, a band width of 22.9% when the chopping switch space is 4 mm with 1.15 MPa SF6 and the peaking switch space is 2.5 mm with 1.0 MPa SF6.
2014,
26: 095007.
doi: 10.11884/HPLPB201426.095007
Abstract:
The design of the linear transformer driver(LTD) stage prototype for Z-pinch driver is introduced. The stage consists of 32 identical bricks connected in parallel. Each brick contains two 100 kV/100 nF capacitors, a 200 kV multi-gap switch, and the output connector that transfer the energy to the resistive load. 32 switches are triggered by 4 high voltage trigger cables (8 switches for each cable). The outer diameter of the stage is about 2.9 m, at a length of 27 cm according to the design. The simulation results show that the output current can be up to 1.0 MA in 118.6 ns rise time at the charge voltage of 90 kV. As a result, the stage can deliver 995 kA current pulse with the rise time of 120.8 ns and FWHM of 335.2 ns into a 90 m resistive load in the preliminary experiment.
The design of the linear transformer driver(LTD) stage prototype for Z-pinch driver is introduced. The stage consists of 32 identical bricks connected in parallel. Each brick contains two 100 kV/100 nF capacitors, a 200 kV multi-gap switch, and the output connector that transfer the energy to the resistive load. 32 switches are triggered by 4 high voltage trigger cables (8 switches for each cable). The outer diameter of the stage is about 2.9 m, at a length of 27 cm according to the design. The simulation results show that the output current can be up to 1.0 MA in 118.6 ns rise time at the charge voltage of 90 kV. As a result, the stage can deliver 995 kA current pulse with the rise time of 120.8 ns and FWHM of 335.2 ns into a 90 m resistive load in the preliminary experiment.
2014,
26: 095101.
doi: 10.11884/HPLPB201426.095101
Abstract:
For accelerator driven sub-critical system (ADS) injector Ⅱ, we studied its fast protection system and timing system, and designed a PXIe controller which could be used to construct fast protection system and timing system. The PXIe controller could achieve optical fiber communication, PXIe bus communication, delay trigger signal output function, etc. Among them, the optical fiber communication function is used to achieve data transmission between each PXIe controller; PXIe bus communication function is primarily used to achieve data exchange between the controller and IPC; delayed trigger signal output function can give precise timing trigger signals, which can ensure all subsystems and equipments work in accordance with certain timing.
For accelerator driven sub-critical system (ADS) injector Ⅱ, we studied its fast protection system and timing system, and designed a PXIe controller which could be used to construct fast protection system and timing system. The PXIe controller could achieve optical fiber communication, PXIe bus communication, delay trigger signal output function, etc. Among them, the optical fiber communication function is used to achieve data transmission between each PXIe controller; PXIe bus communication function is primarily used to achieve data exchange between the controller and IPC; delayed trigger signal output function can give precise timing trigger signals, which can ensure all subsystems and equipments work in accordance with certain timing.
2014,
26: 099001.
doi: 10.11884/HPLPB201426.099001
Abstract:
In this paper, we demonstrate the exclusive display of the patterns fabricated by femtosecond laser with a central wavelength of 800 nm on the 316L stainless steel surface. The uniform ripple structures with a period of 540 nm can be produced under the laser scanning speed of 15 mm/s, line space of 20 m and laser energy density of 1.1 J/cm2. The strong dependence of the ripple orientation on the polarization of laser light offers us the opportunity of fabricating different patterns with different types of ripples. By rotating the sample, the patterns can be exclusively observed under the irradiation of the white light from different angles. In addition, the coordinate areas and the spectral ranges for the exclusive display of the patterns are studied. Finally, the potential applications of this technology are illustrated.
In this paper, we demonstrate the exclusive display of the patterns fabricated by femtosecond laser with a central wavelength of 800 nm on the 316L stainless steel surface. The uniform ripple structures with a period of 540 nm can be produced under the laser scanning speed of 15 mm/s, line space of 20 m and laser energy density of 1.1 J/cm2. The strong dependence of the ripple orientation on the polarization of laser light offers us the opportunity of fabricating different patterns with different types of ripples. By rotating the sample, the patterns can be exclusively observed under the irradiation of the white light from different angles. In addition, the coordinate areas and the spectral ranges for the exclusive display of the patterns are studied. Finally, the potential applications of this technology are illustrated.
2014,
26: 095005.
doi: 10.11884/HPLPB201426.095005
Abstract:
Based on the lumped circuit model, the influences of parasitic elements of pulse transformer, turns ratio and impedance of load on the rise time and overshoot of output waveforms are discussed. The relationship of the parasitic elements between the standard pulse transformer and matrix transformer is analyzed. Matrix transformer with smaller leakage inductance and larger parasitic capacitances is compared to the standard pulse transformer. The standard pulse transformers and matrix transformer are designed and built. The matrix transformer with smaller characteristic coefficient is compared to the standard pulse transformer. The relationship of parasitic elements between pulse transformer and matrix transformer is the same to the theoretical result.
Based on the lumped circuit model, the influences of parasitic elements of pulse transformer, turns ratio and impedance of load on the rise time and overshoot of output waveforms are discussed. The relationship of the parasitic elements between the standard pulse transformer and matrix transformer is analyzed. Matrix transformer with smaller leakage inductance and larger parasitic capacitances is compared to the standard pulse transformer. The standard pulse transformers and matrix transformer are designed and built. The matrix transformer with smaller characteristic coefficient is compared to the standard pulse transformer. The relationship of parasitic elements between pulse transformer and matrix transformer is the same to the theoretical result.
