A 100 kJ-level laser facility has been designed to study inertial confinement fusion physics in China.This facility incorporates various diagnostic techniques,including optical,x-ray imaging,x-ray spectrum,and fusion ...A 100 kJ-level laser facility has been designed to study inertial confinement fusion physics in China.This facility incorporates various diagnostic techniques,including optical,x-ray imaging,x-ray spectrum,and fusion product diagnostics,as well as general diagnostics assistance systems and central control and data acquisition systems.This paper describes recent developments in diagnostics at the facility.展开更多
Significant electromagnetic pulses （EMP） can be generated by the intensive laser irradiating solid targets in inertial confinement fusion （ICF）. To evaluate the EMP intensity and distribution in and outside the la...Significant electromagnetic pulses （EMP） can be generated by the intensive laser irradiating solid targets in inertial confinement fusion （ICF）. To evaluate the EMP intensity and distribution in and outside the laser chamber, we designed and fabricated a discone antenna with ultra-wide bands of over 10 GHz. The return loss （Sn parameter） of this antenna was below -10 dB and could even achieve under -30 dB at 3.1 GHz. The EMP intensity in this study at 80 cm and 40 cm away from the target chamber center （TCC） reached 400 kV/m and 2000 kV/m. The current results are expected to offer preliminary information to study physics regarding laser plasma interactions and will also lay experimental foundation for EMI shielding design to protect various diagnostics.展开更多
Ramp-wave compression experiment to balance the high compression pressure generation in aluminum and x-ray blanking effect in transparent window is demonstrated with an imaging velocity interferometer system for any r...Ramp-wave compression experiment to balance the high compression pressure generation in aluminum and x-ray blanking effect in transparent window is demonstrated with an imaging velocity interferometer system for any reflector （VISAR） on ShenGuang-Ⅲprototype laser facility. The highest pressure is about 500 GPa after using the multilayer target design Al/Au/Al/LiF and -10^13 W//cm2 laser pulse illuminated on the planar Al target, which generates the spatial uniformity to 〈1% over 500 μm on the ablation layer. A 2-μm-thick Au layer is used to prevent the x-ray from preheating the planar ablation Al layer and window material LiF. The imaging VISAR system can be used to record the abrupt loss of the probe beam （λ= 532 nm） caused by absorption and reflection of 20-μm, 30-μm and 40-μm-thick Al, i.e., the blanking effect. Although there are slight shocks in the target, the peak pressure 500 GPa, which is the highest data up to now, is obtained with ramp-wave compression.展开更多
Electromagnetic pulses(EMPs)with high intensity and frequency bandwidth can be generated during the intensive laser irradiating solid targets in inertial confinement fusion(ICF).To shield the EMPs radiation and hence ...Electromagnetic pulses(EMPs)with high intensity and frequency bandwidth can be generated during the intensive laser irradiating solid targets in inertial confinement fusion(ICF).To shield the EMPs radiation and hence protect various diagnostics in and outside the target chamber,we designed a multi-layer structure material to shield the EMFs and demonstrate experimentally and numerically shielding performance of the material structure.The thickness of the multi-layer structure material has a great influence on the EMPs shielding.It is shown that,with the increase of the material thickness,the better shielding performance is obtained,and the material structure with polytetrafluoroethyIene of 0.5 mm,copper of 0.4 mm and lead of 2.4 mm reduces 448 times compared the maximum value of EMPs voltage to that without shielded.The design of multilayer structure material for EMPs shielding provides a promising way to reduce EMPs radiation,which is extremely useful for the diagnostics protection and signal processing in ICF.展开更多
Shock-timing experiments are indispensable to inertial confinement fusion mainly because the timing of multiple shock waves is crucial to understanding the processes of laser irradiation of targets. Investigations int...Shock-timing experiments are indispensable to inertial confinement fusion mainly because the timing of multiple shock waves is crucial to understanding the processes of laser irradiation of targets. Investigations into shock waves driven by a two-step radiation pulse in polystyrene（CH） capsule targets are experimentally conducted at the Shen Guang Ⅱ laser facility. Differing from the traditional shock-timing implementation in which one shock wave could catch up with another one in solid CH, in this experiment, the second shock front in a rarefaction CH layer is observed through velocity interferometry. This second shock could also be made to converge with rarefaction waves within only a few micrometers of the CH capsule by designing the two-shock coalescence time. A shock-timing diagnostic technique to tune the multi-shock convergence in the CH capsule can thereby be achieved.The experimental results in the CH layer are quasi-quantitatively interpreted using streamlines simulated with the Multi-1 D program. The experimental results are expected to offer important information for target structure and laser pulse design, both of which are important for realizing inertial confinement fusion.展开更多
A novel laser facility, named SG-Ⅱ (Shenguang, or Divine Light), has recently passed the appraisal of a panel of experts from the Chinese Academy of Sciences (CAS), China Academy of Engineering Physics, and State... A novel laser facility, named SG-Ⅱ (Shenguang, or Divine Light), has recently passed the appraisal of a panel of experts from the Chinese Academy of Sciences (CAS), China Academy of Engineering Physics, and State High-tech Development Program (National 863 Program). ……展开更多
This paper proposes a novel method of multi-beam laser heterodyne measurement for metal linear expansion coefficient. Based on the Doppler effect and heterodyne technology, the information is loaded of length variatio...This paper proposes a novel method of multi-beam laser heterodyne measurement for metal linear expansion coefficient. Based on the Doppler effect and heterodyne technology, the information is loaded of length variation to the frequency difference of the multi-beam laser heterodyne signal by the frequency modulation of the oscillating mirror, this method can obtain many values of length variation caused by temperature variation after the multi-beam laser heterodyne signal demodulation simultaneously. Processing these values by weighted-average, it can obtain length variation accurately, and eventually obtain the value of linear expansion coefficient of metal by the calculation. This novel method is used to simulate measurement for linear expansion coefficient of metal rod under different temperatures by MATLAB, the obtained result shows that the relative measurement error of this method is just 0.4%.展开更多
Landslides are one of the most disastrous geological hazards in southwestern China.Once a landslide becomes unstable,it threatens the lives and safety of local residents.However,empirical studies on landslides have pr...Landslides are one of the most disastrous geological hazards in southwestern China.Once a landslide becomes unstable,it threatens the lives and safety of local residents.However,empirical studies on landslides have predominantly focused on landslides that occur on land.To this end,we aim to investigate ashore and underwater landslide data synchronously.This study proposes an optimized mosaicking method for ashore and underwater landslide data.This method fuses an airborne laser point cloud with multi-beam depth sounder images.Owing to their relatively high efficiency and large coverage area,airborne laser measurement systems are suitable for emergency investigations of landslides.Based on the airborne laser point cloud,the traversal of the point with the lowest elevation value in the point set can be used to perform rapid extraction of the crude channel boundaries.Further meticulous extraction of the channel boundaries is then implemented using the probability mean value optimization method.In addition,synthesis of the integrated ashore and underwater landslide data angle is realized using the spatial guide line between the channel boundaries and the underwater multibeam sonar images.A landslide located on the right bank of the middle reaches of the Yalong River is selected as a case study to demonstrate that the proposed method has higher precision thantraditional methods.The experimental results show that the mosaicking method in this study can meet the basic needs of landslide modeling and provide a basis for qualitative and quantitative analysis and stability prediction of landslides.展开更多
Due to laser-induced damage, the aperture of optics is one of the main factors limiting the output capability of highpower laser facilities. Because of the general difficulty in achieving large-aperture optics, an alt...Due to laser-induced damage, the aperture of optics is one of the main factors limiting the output capability of highpower laser facilities. Because of the general difficulty in achieving large-aperture optics, an alternative solution is to tile some small-aperture ones together. We propose an accurate, stable, and automatic method of array element tiling and verify it on a double-pass 1 × 2 tiled-grating compressor in the XG-III laser facility. The test results show the accuracy and stability of the method. This research provides an efficient way to obtain large-aperture optics for high-power laser facilities.展开更多
Frequency modulation(FM)-to-amplitude modulation(AM) conversion is an important factor that affects the time±power curve of inertial confinement fusion(ICF) high-power laser facilities. This conversion can impact...Frequency modulation(FM)-to-amplitude modulation(AM) conversion is an important factor that affects the time±power curve of inertial confinement fusion(ICF) high-power laser facilities. This conversion can impact uniform compression and increase the risk of damage to optics. However, the dispersive grating used in the smoothing by spectral dispersion technology will introduce a temporal delay and can spatially smooth the target. The combined effect of the dispersive grating and the focusing lens is equivalent to a Gaussian low-pass filter, which is equivalent to 8 GHz bandwidth and can reduce the intensity modulation on the target to below 5% with 0.3 nm @ 3 GHz + 20 GHz spectrum phase modulation. The results play an important role in the testing and evaluating of the FM-to-AM on the final optics and the target, which is beneficial for comprehensively evaluating the load capacity of the facility and isentropic compression experiment for ICF.展开更多
We have carried out the hohlraum experiments about radiation temperature scaling on the Shenguang-Ⅱ （SG- Ⅱ） laser facility with eight laser beams of 0.35#m, pulse duration of about 1.0ns and total energy of 2000J....We have carried out the hohlraum experiments about radiation temperature scaling on the Shenguang-Ⅱ （SG- Ⅱ） laser facility with eight laser beams of 0.35#m, pulse duration of about 1.0ns and total energy of 2000J. The reradiated x-ray flux through the laser entrance hole was measured using a soft x-ray spectrometer. The measured peak radiation temperature was 170eV for the standard hohlraum and 150 eV for the 1.5-scaled one. We have derived the radiation temperature scaling law, in which the laser hohlraum coupling efficiency is included. With an appropriate coupling efficiency, the coincidences between experimental and scaling hohlraum radiation temperatures are rather good.展开更多
Along with laser-indirect(X-ray)-drive and magnetic-drive target concepts,laser direct drive is a viable approach to achieving ignition and gain with inertial confinement fusion.In the United States,a national program...Along with laser-indirect(X-ray)-drive and magnetic-drive target concepts,laser direct drive is a viable approach to achieving ignition and gain with inertial confinement fusion.In the United States,a national program has been established to demonstrate and understand the physics of laser direct drive.The program utilizes the Omega Laser Facility to conduct implosion and coupling physics at the nominally 30-kJ scale and lasereplasma interaction and coupling physics at the MJ scale at the National Ignition Facility.This article will discuss the motivation and challenges for laser direct drive and the broad-based program presently underway in the United States.展开更多
Large aperture Nd:phosphate laser glass is a key optical element for an inertial confinement fusion(ICF) facility. N31,one type of neodymium doped phosphate glasses, was developed for high peak power laser facility ap...Large aperture Nd:phosphate laser glass is a key optical element for an inertial confinement fusion(ICF) facility. N31,one type of neodymium doped phosphate glasses, was developed for high peak power laser facility applications in China. The composition and main properties of N31 glass are given, together with those of LHG-8, LG-770, and KGSS-0180 Nd:phosphate laser glasses, from Hoya and Schott, and from Russia. The technologies of pot melting, continuous melting, and edge cladding of large size N31 phosphate laser glass are briefly described. The small signal gain profiles of N31 glass slabs from both pot melting and continuous melting at various values of the pumping energy of the xenon lamp are presented. N31 glass is characterized by a stimulated emission cross section of 3.8 × 10-20cm2 at 1053 nm,an absorption coefficient of 0.10–0.15% cm-1at laser wavelength, small residual stress around the interface between the cladding glass and the laser glass, optical homogeneity of ～2 × 10-6in a 400 mm aperture, and laser damage threshold larger than 42 J/cm2 for a 3 ns pulse width at 1064 nm wavelength.展开更多
In high power laser facility for inertial confinement fusion research, final optics assembly(FOA) plays a critical role in the frequency conversion, beam focusing, color separation, beam sampling and debris shielding....In high power laser facility for inertial confinement fusion research, final optics assembly(FOA) plays a critical role in the frequency conversion, beam focusing, color separation, beam sampling and debris shielding. The design and performance of FOA in SG-II Upgrade laser facility are mainly introduced here. Due to the limited space and short focal length, a coaxial aspheric wedged focus lens is designed and applied in the FOA configuration. Then the ghost image analysis,the focus characteristic analysis, the B integral control design and the optomechanical design are carried out in the FOA design phase. In order to ensure the FOA performance, two key technologies are developed including measurement and adjustment technique of the wedged focus lens and the stray light management technique based on ground glass.Experimental results show that the design specifications including laser fluence, frequency conversion efficiency and perforation efficiency of the focus spot have been achieved, which meet the requirements of physical experiments well.展开更多
基金This work was performed under the auspices of the National Key R&D Program of China,No.2017YFA0403300National Natural Science Foundation of China under Contract Nos.11805184,11805178,11805185+2 种基金Presidential Foundation of China Academy of Engineering Physics,No.YZJJLX2019011Science Challenging Project,No.TZ2016001Laser Fusion Research Center Funds for Young Talents,No.RCFPD4-2020-1.
文摘A 100 kJ-level laser facility has been designed to study inertial confinement fusion physics in China.This facility incorporates various diagnostic techniques,including optical,x-ray imaging,x-ray spectrum,and fusion product diagnostics,as well as general diagnostics assistance systems and central control and data acquisition systems.This paper describes recent developments in diagnostics at the facility.
基金supported by the Fundamental Research Funds for the Central Universities of China(No.ZYGX2015J108)National Natural Science Foundation of China(Nos.11575166 and 51581140)
文摘Significant electromagnetic pulses （EMP） can be generated by the intensive laser irradiating solid targets in inertial confinement fusion （ICF）. To evaluate the EMP intensity and distribution in and outside the laser chamber, we designed and fabricated a discone antenna with ultra-wide bands of over 10 GHz. The return loss （Sn parameter） of this antenna was below -10 dB and could even achieve under -30 dB at 3.1 GHz. The EMP intensity in this study at 80 cm and 40 cm away from the target chamber center （TCC） reached 400 kV/m and 2000 kV/m. The current results are expected to offer preliminary information to study physics regarding laser plasma interactions and will also lay experimental foundation for EMI shielding design to protect various diagnostics.
基金Supported by the National Natural Science Foundation of China under Grant No 11305160
文摘Ramp-wave compression experiment to balance the high compression pressure generation in aluminum and x-ray blanking effect in transparent window is demonstrated with an imaging velocity interferometer system for any reflector （VISAR） on ShenGuang-Ⅲprototype laser facility. The highest pressure is about 500 GPa after using the multilayer target design Al/Au/Al/LiF and -10^13 W//cm2 laser pulse illuminated on the planar Al target, which generates the spatial uniformity to 〈1% over 500 μm on the ablation layer. A 2-μm-thick Au layer is used to prevent the x-ray from preheating the planar ablation Al layer and window material LiF. The imaging VISAR system can be used to record the abrupt loss of the probe beam （λ= 532 nm） caused by absorption and reflection of 20-μm, 30-μm and 40-μm-thick Al, i.e., the blanking effect. Although there are slight shocks in the target, the peak pressure 500 GPa, which is the highest data up to now, is obtained with ramp-wave compression.
基金National Natural Science Foundation of China(No.61405167)the Fundamental Research Funds for the Central Universities(Nos.2682018GF10 and 2682019LK08)We would like to thank China Academy of Engineering Physics for their assistance in experiments.
文摘Electromagnetic pulses(EMPs)with high intensity and frequency bandwidth can be generated during the intensive laser irradiating solid targets in inertial confinement fusion(ICF).To shield the EMPs radiation and hence protect various diagnostics in and outside the target chamber,we designed a multi-layer structure material to shield the EMFs and demonstrate experimentally and numerically shielding performance of the material structure.The thickness of the multi-layer structure material has a great influence on the EMPs shielding.It is shown that,with the increase of the material thickness,the better shielding performance is obtained,and the material structure with polytetrafluoroethyIene of 0.5 mm,copper of 0.4 mm and lead of 2.4 mm reduces 448 times compared the maximum value of EMPs voltage to that without shielded.The design of multilayer structure material for EMPs shielding provides a promising way to reduce EMPs radiation,which is extremely useful for the diagnostics protection and signal processing in ICF.
基金Supported by the Science and Technology on Plasma Physics Laboratory under Grant No 9140C6801021001
文摘Shock-timing experiments are indispensable to inertial confinement fusion mainly because the timing of multiple shock waves is crucial to understanding the processes of laser irradiation of targets. Investigations into shock waves driven by a two-step radiation pulse in polystyrene（CH） capsule targets are experimentally conducted at the Shen Guang Ⅱ laser facility. Differing from the traditional shock-timing implementation in which one shock wave could catch up with another one in solid CH, in this experiment, the second shock front in a rarefaction CH layer is observed through velocity interferometry. This second shock could also be made to converge with rarefaction waves within only a few micrometers of the CH capsule by designing the two-shock coalescence time. A shock-timing diagnostic technique to tune the multi-shock convergence in the CH capsule can thereby be achieved.The experimental results in the CH layer are quasi-quantitatively interpreted using streamlines simulated with the Multi-1 D program. The experimental results are expected to offer important information for target structure and laser pulse design, both of which are important for realizing inertial confinement fusion.
文摘 A novel laser facility, named SG-Ⅱ (Shenguang, or Divine Light), has recently passed the appraisal of a panel of experts from the Chinese Academy of Sciences (CAS), China Academy of Engineering Physics, and State High-tech Development Program (National 863 Program). ……
基金Project supported by the National Natural Science Foundation of China(Grant No.60577032)
文摘This paper proposes a novel method of multi-beam laser heterodyne measurement for metal linear expansion coefficient. Based on the Doppler effect and heterodyne technology, the information is loaded of length variation to the frequency difference of the multi-beam laser heterodyne signal by the frequency modulation of the oscillating mirror, this method can obtain many values of length variation caused by temperature variation after the multi-beam laser heterodyne signal demodulation simultaneously. Processing these values by weighted-average, it can obtain length variation accurately, and eventually obtain the value of linear expansion coefficient of metal by the calculation. This novel method is used to simulate measurement for linear expansion coefficient of metal rod under different temperatures by MATLAB, the obtained result shows that the relative measurement error of this method is just 0.4%.
基金supported in part by the National Key R&D Program of China(Grant no.2016YFC0401908)。
文摘Landslides are one of the most disastrous geological hazards in southwestern China.Once a landslide becomes unstable,it threatens the lives and safety of local residents.However,empirical studies on landslides have predominantly focused on landslides that occur on land.To this end,we aim to investigate ashore and underwater landslide data synchronously.This study proposes an optimized mosaicking method for ashore and underwater landslide data.This method fuses an airborne laser point cloud with multi-beam depth sounder images.Owing to their relatively high efficiency and large coverage area,airborne laser measurement systems are suitable for emergency investigations of landslides.Based on the airborne laser point cloud,the traversal of the point with the lowest elevation value in the point set can be used to perform rapid extraction of the crude channel boundaries.Further meticulous extraction of the channel boundaries is then implemented using the probability mean value optimization method.In addition,synthesis of the integrated ashore and underwater landslide data angle is realized using the spatial guide line between the channel boundaries and the underwater multibeam sonar images.A landslide located on the right bank of the middle reaches of the Yalong River is selected as a case study to demonstrate that the proposed method has higher precision thantraditional methods.The experimental results show that the mosaicking method in this study can meet the basic needs of landslide modeling and provide a basis for qualitative and quantitative analysis and stability prediction of landslides.
基金Project supported by the National Natural Science Foundation of China(Grant No.61308040)the National High Technology Research and Development Program of China(Grant No.2013AA8043047)
文摘Due to laser-induced damage, the aperture of optics is one of the main factors limiting the output capability of highpower laser facilities. Because of the general difficulty in achieving large-aperture optics, an alternative solution is to tile some small-aperture ones together. We propose an accurate, stable, and automatic method of array element tiling and verify it on a double-pass 1 × 2 tiled-grating compressor in the XG-III laser facility. The test results show the accuracy and stability of the method. This research provides an efficient way to obtain large-aperture optics for high-power laser facilities.
基金supported by the Strategic Priority Research Program of the Chinese Academy of Sciences (No.XDA25020303)。
文摘Frequency modulation(FM)-to-amplitude modulation(AM) conversion is an important factor that affects the time±power curve of inertial confinement fusion(ICF) high-power laser facilities. This conversion can impact uniform compression and increase the risk of damage to optics. However, the dispersive grating used in the smoothing by spectral dispersion technology will introduce a temporal delay and can spatially smooth the target. The combined effect of the dispersive grating and the focusing lens is equivalent to a Gaussian low-pass filter, which is equivalent to 8 GHz bandwidth and can reduce the intensity modulation on the target to below 5% with 0.3 nm @ 3 GHz + 20 GHz spectrum phase modulation. The results play an important role in the testing and evaluating of the FM-to-AM on the final optics and the target, which is beneficial for comprehensively evaluating the load capacity of the facility and isentropic compression experiment for ICF.
文摘We have carried out the hohlraum experiments about radiation temperature scaling on the Shenguang-Ⅱ （SG- Ⅱ） laser facility with eight laser beams of 0.35#m, pulse duration of about 1.0ns and total energy of 2000J. The reradiated x-ray flux through the laser entrance hole was measured using a soft x-ray spectrometer. The measured peak radiation temperature was 170eV for the standard hohlraum and 150 eV for the 1.5-scaled one. We have derived the radiation temperature scaling law, in which the laser hohlraum coupling efficiency is included. With an appropriate coupling efficiency, the coincidences between experimental and scaling hohlraum radiation temperatures are rather good.
文摘Along with laser-indirect(X-ray)-drive and magnetic-drive target concepts,laser direct drive is a viable approach to achieving ignition and gain with inertial confinement fusion.In the United States,a national program has been established to demonstrate and understand the physics of laser direct drive.The program utilizes the Omega Laser Facility to conduct implosion and coupling physics at the nominally 30-kJ scale and lasereplasma interaction and coupling physics at the MJ scale at the National Ignition Facility.This article will discuss the motivation and challenges for laser direct drive and the broad-based program presently underway in the United States.
文摘Large aperture Nd:phosphate laser glass is a key optical element for an inertial confinement fusion(ICF) facility. N31,one type of neodymium doped phosphate glasses, was developed for high peak power laser facility applications in China. The composition and main properties of N31 glass are given, together with those of LHG-8, LG-770, and KGSS-0180 Nd:phosphate laser glasses, from Hoya and Schott, and from Russia. The technologies of pot melting, continuous melting, and edge cladding of large size N31 phosphate laser glass are briefly described. The small signal gain profiles of N31 glass slabs from both pot melting and continuous melting at various values of the pumping energy of the xenon lamp are presented. N31 glass is characterized by a stimulated emission cross section of 3.8 × 10-20cm2 at 1053 nm,an absorption coefficient of 0.10–0.15% cm-1at laser wavelength, small residual stress around the interface between the cladding glass and the laser glass, optical homogeneity of ～2 × 10-6in a 400 mm aperture, and laser damage threshold larger than 42 J/cm2 for a 3 ns pulse width at 1064 nm wavelength.
文摘In high power laser facility for inertial confinement fusion research, final optics assembly(FOA) plays a critical role in the frequency conversion, beam focusing, color separation, beam sampling and debris shielding. The design and performance of FOA in SG-II Upgrade laser facility are mainly introduced here. Due to the limited space and short focal length, a coaxial aspheric wedged focus lens is designed and applied in the FOA configuration. Then the ghost image analysis,the focus characteristic analysis, the B integral control design and the optomechanical design are carried out in the FOA design phase. In order to ensure the FOA performance, two key technologies are developed including measurement and adjustment technique of the wedged focus lens and the stray light management technique based on ground glass.Experimental results show that the design specifications including laser fluence, frequency conversion efficiency and perforation efficiency of the focus spot have been achieved, which meet the requirements of physical experiments well.
