Laser Direct Driven Quasi-isentropic Compression Loading on “Heaven-Ⅰ” Laser Facility

正Quasi-isentropic compression is a continuous and slow loading process,with the characteristics of low temperature rise and low entropy increase.It has been widely used in ICF,EOS,earth and     

Experimental System Foundation of Laser Cluster Interaction

太平洋富钴结壳是一种产于大洋海底的金属矿产。它由于富含Mn，Co，Ni，Cu，Au和Pt等多种有用金属元素，储量大，产出水深相对较浅，较易开采，而具有极大的经济开发价值，是当前各国争相研究的新矿产。富钴结壳的厚度和Mn，Co等有用金属含量（即它的开发价值）与结壳的生长速率和年龄有密切关系。因此，精确测定富钴结壳的年龄和生长速率，对于调查和圈定海底富钴结壳矿产资源是十分必要的。     

Experimental System Foundation of Laser Cluster Interaction

In order to invest absorption mechanism of laser-clusters interaction, system of cluster generation, system of laser cluster synchronization and a set of TOF spectrometer were developed. The system of cluster generation is made up of solenoid valve and po…     

50 mJ Subpicosecond Ultrafast KrF Laser Syste

Recently,anintensivetabletopultrashortpulsevioletlasersystemisestablishedinlaserlaboratoryofexcimerinCIAE,whichbringspositivelyattractionandpotentialtopromotetheresearchesinthefieldofultrafastlaser,suchaslaserplasmainteractionandICFfastignition.Thefront-e…     

Bifurcation and Chaos Control for Nonlinear Laser Systems

In recent years, complexity science, including various bifurcations ,chaos and turbulence, has become a great challenge in various interdisciplinary fields. It promises to have a major impact on many aspects of nature science and engineering, even social and economic science. Candidates of complex system include coupled laser systems, accelerator-driven clean nuclear power system, neural networks, cellular automata, living organism, human brain, chemical reactions and economic systems. This new and challenging research and development area has in effect become a scientific inter-discipline itself, involving systems and control engineers, theoretical and experimental     

Amplification of Short Pulse High Power UV Laser

At recent year, with the development of CPA and other amplification technology, laser intensity achieves great increase and laser power can be high to PW(105) now, this ultrashort pulse lasers offer scientists a route to investigate laser-matter interaction in an absolute new regime.So far the researches on ultrashort pulse laser-matter interaction concentrated on infrared regime, yet ultraviolet laser has the advantage in intense field physics and ICF researches for its short wavelength and less nonlinear effects. KrF excimer is the best medium in UV ultrashort pulse amplification for its small saturation energy and high contrast ratio accessible.     

Synchronize of RF Signal to Femtosecond Laser Pulse Train

Synchrotron radiation lighting source, as the revolutionary lighting source after the electronic lighting source, X-ray lighting source and laser lighting source, has been widely used in advanced research work such as material, circumstance and biology technology. Compare to the third generation     

Application of CHEL3300 Excimer Laser in Heaven-I System

The discharge pumping laser of CHEL3300(China Highpower Excimer Lab 3×300 mJ) was developed by the Department of Experimental Physics of University of Szeged(DEP) and the High Power Excimer Laser Laboratory (HPELL) of China Institute of Atomic Energy. It…     

The Electron Trajectory in a Relativistic Femtosecond Laser Pulse

In this report, we start from Lagrange equation and analyze theoretically the electron dynamics in electromagnetic field. By solving the relativistic government equations of electron, the trajectories of an electron in plane laser pulse, focused laser pulse have been given for different initial conditions. The electron trajectory is determined by its initial momentum, the amplitude, spot size and polarization of the laser pulse. The optimum initial momentum of the electron for LSS （laser synchrotron source） is obtained. Linear polarized laser is more advantaged than circular polarized laser for generating harmonic radiation.     

Synchronize of RF Signal to Femtosecond Laser Pulse Train

作为裂变产物和中子活化产物的^93Zr是一种长寿命纯β放射性核素，它的测量对提供核数据有重要意义。但由于^93Zr放射性衰变计数率低，且^93Nb对^93Zr的测量造成很强的本底干扰，大大影响了^93Zr的超高灵敏测量。AMS是实现^93Zr的超高灵敏测量的方法之一。     

地铁高频电磁辐射的安全评估

为有效评估B型地铁乘客信息系统天线(Passenger information system,PIS)对司机室高频电磁辐射的安全性,设计PIS系统所用的5.8 GHz八木天线和司机人体模型,利用三维电磁仿真软件构建在PIS系统天线辐射下的地铁司机室高频电磁环境模型,数值模拟天线在不同输入功率条件下对地铁司机人体模型的高频电磁辐射影响。仿真结果表明,当天线的输入功率达到最大值50 W时,人体模型的比吸收率最大值0.63 W/kg,低于国际非电离辐射委员会(International Commission on Non-Ionizing Radiation Protection,ICNIRP)制定的职业电磁暴露基本限值10 W/kg;电场强度最大值为72.37 V/m,低于ICNIRP职业电磁暴露参考限值137 V/m;磁场强度最大值为0.74 A/m,高于ICNIRP职业电磁暴露参考限值0.36 A/m。当天线的输入功率降为10 W时,磁场强度最大值降为0.33 A/m,低于参考限值。因此,为了避免此高频电磁辐射对司机造成健康危害,地铁实际运行时,需要保证天线的输入功率低于10 W,使司机处于安全辐射范围内。     

超短超强激光与固体靶相互作用所致X射线剂量实验研究

超短超强激光与固体靶相互作用可产生显著的X射线剂量,其辐射防护问题是辐射防护和激光等离子体物理的学科交叉问题,对超短超强激光装置安全运行至关重要。为验证清华大学所提出的剂量评估公式,对超短超强激光与固体靶作用所产生的X射线剂量开展了实验研究。设计了用于屏蔽靶室内超热电子和散射光子的屏蔽结构,仅测量超热电子和固体靶作用所产生的X射线剂量,并开展蒙特卡罗模拟评估其屏蔽效果。基于星光 Ⅲ激光装置对不同激光功率密度（7×1018~4×1019 W/cm2）下不同角度上的X射线剂量开展了实验测量,并与不同的剂量评估公式结果进行了比较分析,实验中还对不同剂量测量探测器的响应进行了比较。计算结果表明,所设计的屏蔽结构能很好地屏蔽超热电子和散射光子。实验结果表明,清华大学所提出的剂量评估公式较文献公式能更好地与实验结果吻合。随激光功率密度的增加,前向的X射线剂量较侧向增加得更快。     

Two-colored Laser Circulation System for Monochromatic Tunable Hard X-ray Source

A two-colored laser pulse circulation system for a monochromatic tunable hard X-ray source via laser electron Compton scattering is investigated. The demonstration system of the X-ray source is under construction at the University of Tokyo. It consists of the X-band (11.424 GHz) electron linear accelerator and two Nd: YAG laser systems. The main advantage of this system is a monochromatic tunable hard X-ray. It is calculated that the X-ray intensity will be about 10⁸ photons/s. In order to enhance the X-ray intensity for medical applications such as dual energy X-ray CT, a two-colored laser pulse circulation system has been designed. The laser pulse circulation experiment without an electron beam has been carried out by using a Nd: YAG laser fundamental wave (50 mJ) and a second harmonics wave (25 mJ). The result shows that the X-ray intensity can be enhanced by a factor of 10 times higher (i.e., up to 10⁹ photons/s). This work is a part of the JST (Japan Science and Technology Agency) project. The entire X-ray source system is a part of a larger national project on the development of an advanced compact medical accelerator sponsored by the NIRS (National Institute for Radiological Science). The University of Tokyo and KEK are responsible for the X-ray source.     

Development of the HCN heterodyne collective scattering system on J-TEXT

A heterodyne collective scattering system has been designed and developed to investigate the turbulent transport of core plasma on J-TEXT. A dual-HCN laser which consists of two separately pumped HCN gas lasers at 337 μm has been developed as the laser source of the scattering system. The intermediate frequency (IF) is ∼1 MHz when there is a 4 μm cavity length difference and capable to maintain stability more than 5 h without manual operation. Detection channels at three different angles (2 ≤ k⊥ ≤ 12 cm−1) have been installed with Schottky barrier diode mixers of 893 GHz. The sampling frequency of the acquisition system is 6 MHz to observe low-frequency density fluctuations. Initial experimental results have been detected and more results can be expected in future experiments.     

Spatial and temporal evolution of electromagnetic pulses generated at Shenguang-Ⅱ series laser facilities

The distribution and sources of EMPs produced at Shenguang-Ⅱ(SG-Ⅱ)series laser facilities are systematically investigated.The results indicate that the EMP amplitudes in the SG-Ⅱ ps PW laser are very strong,one order higher than those from the SG-Ⅱ laser facility.EMPs outside the target chamber decrease exponentially with the distance from the measuring points to the target chamber center at the two laser facilities.Moreover,EMPs can be remarkably reduced when the picosecond laser together with the nanosecond laser is incident to targets compared to the SG-Ⅱps PW laser alone.The resulting conclusions are expected to offer experimental supports for further effective EMPs shielding design and achievement in high-power laser facilities.     

放射性表面污染金属废物激光去污工艺研究

为实现激光去污技术在放射性表面污染金属废物清洁解控或循环再利用方面的应用,以350 W的纳秒脉冲光纤激光器为基础搭建了激光去污实验装置,针对激光功率、脉宽、频率、线间距、扫描速度等关键参数开展了一系列激光剥离去污工艺实验,根据实验结果分析得出激光去污工艺规律和不同去污深度的最佳工艺参数,并以某核电厂控制棒水池贮存搁架底板为对象开展验证试验。验证试验结果显示,采用激光去污技术,去污深度达到10 μm后,样品的β射线放射性表面污染水平已低于0.8 Bq/cm2,可达到清洁解控的表面污染水平要求。      

不锈钢放射性模拟样片在空气中的激光去污技术

采用APEX放电型准分子激光器作为激光光源,用低放废液制备不锈钢放射性模拟样片,在激光去污装置上开展激光去污工艺参数的研究。通过考察不同的辐照强度、脉冲频率、辐照角度及扫描速率参数对不锈钢放射性模拟样片表面去污因子DF的影响,获得了激光去污工艺参数。在此参数下对模拟样片表面的去污因子大于200,剥离厚度小于20μm。     

Ionization Induced Scattering of Femtosecond Intense Laser Pulses in Cluster Plasmas

The 45° scattering of a femtosecond (60 fs) intense laser pulse with a 20 nm FWHM (the full width at half maximum) spectrum centered at 790 nm has been studied experimentally while focused in argon clusters at intensity ～ 1016 W/cra2. Scattering spectra under different backing pressures and laser-plasma interaction lengths were obtained, which showed spectral blueshifting, beam refraction and complex modulation. These ionization-induced effects reveal the modulation of laser pulses propagating in plasmas and the existing obstacle in laser cluster interaction at high laser intensity and high electron density.     

Simulation of electromagnetic pulses generated by escaped electrons in a high- power laser chamber

Intensive electromagnetic pulses (EMPs) can be generated when a high-power laser strikes a target. The transient electromagnetic field can have an intensity of up to several hundred kV m ^-1 with a broad frequency of up to several gigahertz, which may affect diagnostics and interfere with, or even damage, electronic equipment. In this paper, the process in which hot electrons produced by the laser-target interaction radiate EMPs is studied and simulated. The physical process is divided into three stages which are: the production of hot electrons; the escape of hot electrons; and the generation of EMPs. Instead of using a general finite difference time domain (FDTD) method to solve the Maxwell equations, a particle-in-cell method together with a time- biased FDTD method is applied in EMP simulation to restrain high-frequency noise. The results show that EMPs are stronger with higher laser intensity and larger target size.     

Fusion Generated Fast Particles by Laser Impact on Ultra-Dense Deuterium: Rapid Variation with Laser Intensity

Nuclear fusion D+D processes are studied by nanosecond pulsed laser interaction with ultra-dense deuterium. This material has a density of 10²⁹ cm^?3 as shown in several previous publications. Laser power is <2 W (0.2 J pulses) and laser intensity is <10¹⁴ W cm^?2 in the 5–10 μm wide beam waist. Particle detection by time-of-flight energy analysis with plastic scintillators is used. Metal foils in the particle flux to the detector remove slow ions, and make it possible to convert and count particles with energy well above 1 MeV. The variation of the signal of MeV particles from D+D fusion is measured as a function of laser power. At relatively weak laser-emitter interaction, the particle signal from the laser focus varies as the square of the laser power. This indicates collisions in the ultra-dense deuterium of two fast deuterons released by Coulomb explosions. During experiments with stronger laser-emitter interaction, the signal varies approximately as the sixth power of the laser power, indicating a plasma process. At least 2 × 10⁶ particles are created by each laser pulse at the maximum intensity used. Our results indicate break-even in fusion at a laser pulse energy of 1 J with the same focusing, in approximate agreement with theoretical results for ignition conditions in ultra-dense deuterium. Radiation loss at high temperature will however require higher laser energy at break-even.