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Compact ultrafast neutron sources via bulk acceleration of deuteron ions in an optical trap

Matter and Radiation at Extremes 2024年第5期9卷 22-31页

作者： Zhiyu Lei Hanghang Ma Xiaobo Zhang Lin Yu Yihang Zhang Yutong Li suming weng Min Chen Jie Zhang Zhengming Sheng Key Laboratory for Laser Plasmas and School of Physics and Astronomy Shanghai Jiao Tong UniversityShanghai 200240China Collaborative Innovation Centre of IFSA Shanghai Jiao Tong UniversityShanghai 200240China Tsung-Dao Lee Institute Shanghai Jiao Tong UniversityShanghai 201210China College of Physics and Electronics Engineering Northwest Normal UniversityLanzhou 730070China Beijing National Laboratory for Condensed Matter Physics Institute of PhysicsChinese Academy of SciencesBeijing 100190China

A scheme for a quasi-monoenergetic high-flux neutron source with femtosecond duration and highly anisotropic angular distribution is *** scheme is based on bulk acceleration of deuteron ions in an optical trap or density grating formed by two counter-propagating laser pulses at an intensity of-10^(16)W~cm^(2)in a near-critical-density *** deuterons are first pre-accelerated to an energy of tens of keV in the ambipolar fields formed in the optical *** energy is boosted to the MeV level by another one or two laser pulses at an intensity of-10^(20)W~cm^(2),enabling fusion reactions to be triggered with high *** contrast to previously proposed pitcher–catcher configurations,our scheme can provide spatially periodic acceleration structures and effective collisions between deuterons inside the whole target ***,neutrons are generated directly inside the optical *** simulations show that neutron pulses with energy 2–8 MeV,yield 10^(18)–10^(19)n/s,and total number 106–107 in a duration-400 fs can be obtained with a 25μm ***,the neutron pulses exhibit unique angularly dependent energy spectra and flux distributions,predominantly along the axis of the energy-boosting *** microsize femtosecond neutron pulses may find many applications,such as high-resolution fast neutron imaging and nuclear physics research.

关键词： acceleration scheme angular

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Nonlocal thermal transport in magnetized plasma along different directions

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Matter and Radiation at Extremes 2022年第4期7卷 30-39页

作者： Hanzhi Zhao Zhengming Sheng suming weng Key Laboratory for Laser Plasmas(MoE) School of Physics and AstronomyShanghai Jiao Tong UniversityShanghai 200240China Collaborative Innovation Center of IFSA Shanghai Jiao Tong UniversityShanghai 200240China Tsung-Dao Lee Institute Shanghai Jiao Tong UniversityShanghai 200240China

Nonlocal thermal transport in magnetized plasmas is studied theoretically and numerically with the Vlasov–Fokker–Planck(VFP)model,in which the magnetic field has nonzero components both perpendicular to and along the temperature *** heat transport is found in both the longitudinal and transverse directions,provided the temperature gradients are sufficiently *** magnetic field tends to reduce the nonlocality of the thermal transport in the direction perpendicular to the magnetic field,i.e.,the difference between the heat fluxes predicted by the Braginskii theory and the VFP simulation decreases with increasing magnetic field *** the initial temperature gradient is steep,the nonlocal heat flux depends not only on the present temperature profile,but also on its time ***,the contribution of high-order terms in the spherical harmonic expansion of the electron distribution function becomes important for a magnetized plasma,in particular for thermal transport in the direction perpendicular to the temperature gradient.

关键词： VFP directions thermal

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Absolute instability modes due to rescattering of stimulated Raman scattering in a large nonuniform plasma

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High Power Laser Science and Engineering 2019年第1期7卷 144-153页

作者： Yao Zhao Zhengming Sheng suming weng Shengzhe Ji Jianqiang Zhu Key Laboratory of High Power Laser and Physics Shanghai Institute of Optics and Fine Mechanics Chinese Academy of Sciences Key Laboratory for Laser Plasmas (MoE) School of Physics and Astronomy Shanghai Jiao Tong University Collaborative Innovation Center of IFSA (CICIFSA) Shanghai Jiao Tong University SUPA Department of Physics University of Strathclyde Tsung-Dao Lee Institute Shanghai Jiao Tong University University of Chinese Academy of Sciences

Absolute instability modes due to secondary scattering of stimulated Raman scattering (SRS) in a large nonuniform plasma are studied theoretically and numerically. The backscattered light of convective SRS can be considered as a pump light with a finite bandwidth. The different frequency components of the backscattered light can be coupled to develop absolute SRS instability near their quarter-critical densities via rescattering process. The absolute SRS mode develops a Langmuir wave with a high phase velocity of about c/■ with c the light speed in vacuum. Given that most electrons are at low velocities in the linear stage, the absolute SRS mode grows with very weak Landau damping. When the interaction evolves into the nonlinear regime, the Langmuir wave can heat abundant electrons up to a few hundred ke V via the SRS rescattering. Our theoretical model is validated by particle-in-cell simulations. The absolute instabilities may play a considerable role in the experiments of inertial confinement fusion.

关键词： laser plasma interactions stimulated Raman scattering two plasmon decay instability hot electron

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Stimulated Raman scattering excited by incoherent light in plasma

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Matter and Radiation at Extremes 2017年第4期2卷 190-196页

作者： Yao Zhao suming weng Min Chen Jun Zheng Hongbin Zhuo Zhengming Sheng Key Laboratory for Laser Plasmas(MoE) School of Physics and AstronomyShanghai Jiao Tong UniversityShanghai 200240China Collaborative Innovation Center of IFSA(CICIFSA) Shanghai Jiao Tong UniversityShanghai 200240China College of Science National University of Defense TechnologyChangsha 410073China SUPA Department of PhysicsUniversity of StrathclydeGlasgow G40NGUK

Stimulated Raman scattering(SRS)excited by incoherent light is studied via particle-in-cell *** is shown that a large bandwidth of incoherent light can reduce the growth of SRS and electron heating considerably in the linear ***,different components of the incoherent light can be coupled by the Langmuir waves,so that stimulated Raman backward scattering can *** the bandwidth of incoherent light is larger than the Langmuir wave frequency,forward SRS can be seeded between different components of the incoherent *** incoherent light can only increase the time duration for nonlinear saturation but cannot diminish the saturation level obviously.

关键词： Stimulated Raman scattering Instability suppression Incoherent light Inertial confinement fusion

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Magnetic field annihilation and reconnection driven by femtosecond lasers in inhomogeneous plasma

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Science China(Physics,Mechanics & Astronomy) 2017年第11期60卷 68-75页

作者： YouYuan Wang FeiYu Li Min Chen suming weng QuanMing Lu QuanLi Dong ZhengMing Sheng Jie Zhang Key Laboratory for Laser Plasmas (Ministry of Education) and School of Physics and Astronomy Shanghai Jiao Tong University Collaborative Innovation Center of IFSA (CICIFSA) Shanghai Jiao Tong University Scottish Universities Physics Alliance (SUPA) Department of PhysicsUniversity of Strathclyde Key Lab of Geospace Environment Chinese Academy of Sciences Department of Geophysics and Planetary Science University of Science and Technology of China School of Physics and Optoelectronic Engineering Ludong University

The process of fast magnetic reconnection driven by intense ultra-short laser pulses in underdense plasma is investigated by particle-in-cell simulations. In the wakefield of such laser pulses, quasi-static magnetic fields at a few mega-Gauss are generated due to nonvanishing cross product ▽(n/) × p. Excited in an inhomogeneous plasma of decreasing density, the quasi-static magnetic field structure is shown to drift quickly both in lateral and longitudinal directions. When two parallel-propagating laser pulses with close focal spot separation are used, such field drifts can develop into magnetic reconnection(annihilation) in their overlapping region, resulting in the conversion of magnetic energy to kinetic energy of particles. The reconnection rate is found to be much higher than the value obtained in the Hall magnetic reconnection model. Our work proposes a potential way to study magnetic reconnection-related physics with short-pulse lasers of terawatt peak power only.

关键词： magnetic reconnection laser wakefield magnetic field generation

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Effects of second-order dispersion of ultrashort laser pulse on stimulated Raman scattering

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High Power Laser Science and Engineering 2022年第6期10卷 41-48页

作者： Yanqing Deng Dongning Yue Mufei Luo Xu Zhao Yaojun Li Xulei Ge Feng Liu suming weng Min Chen Xiaohui Yuan Jie Zhang Key Laboratory for Laser Plasmas(Ministry of Education) School of Physics and AstronomyShanghai Jiao Tong UniversityShanghaiChina Collaborative Innovation Center of IFSA Shanghai Jiao Tong UniversityShanghaiChina

The influence of second-order dispersion(SOD)on stimulated Raman scattering(SRS)in the interaction of an ultrashort intense laser with plasma was *** significant backward SRS was observed with the increase of the absolute value of SOD(|ψ2|).The integrated intensity of the scattered light is positively correlated to the driver laser pulse *** by the side SRS,filaments with different angles along the laser propagation direction were observed in the transverse shadowgraph.A model incorporating Landau damping and above-threshold ionization was developed to explain the SOD-dependent angular distribution of the filaments.

关键词： second-order dispersion stimulated Raman scattering ultrashort intense laser

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Stimulated Raman scattering in a non-eigenmode regime

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High Power Laser Science and Engineering 2020年第2期8卷 80-87页

作者： Yao Zhao suming weng Zhengming Sheng Jianqiang Zhu Key Laboratory of High Power Laser and Physics Shanghai Institute of Optics and Fine MechanicsChinese Academy of SciencesShanghai 201800China Key Laboratory for Laser Plasmas(MoE) School of Physics and AstronomyShanghai Jiao Tong UniversityShanghai 200240China Collaborative Innovation Center of IFSA(CICIFSA) Shanghai Jiao Tong UniversityShanghai 200240China SUPA Department of PhysicsUniversity of StrathclydeGlasgow G40NGUK

Stimulated Raman scattering(SRS)in plasma in a non-eigenmode regime is studied theoretically and *** from normal SRS with the eigen electrostatic mode excited,the non-eigenmode SRS is developed at plasma density ne>0.25nc when the laser amplitude is larger than a certain *** satisfy the phase-matching conditions of frequency and wavenumber,the excited electrostatic mode has a constant frequency around half of the incident light frequency ω0/2,which is no longer the eigenmode of electron plasma wave ω*** the scattered light and the electrostatic wave are trapped in plasma with their group velocities being ***-hot electrons are produced by the non-eigen electrostatic *** theoretical model is validated by particle-in-cell *** SRS driven in this non-eigenmode regime is an important laser energy loss mechanism in the laser plasma interactions as long as the laser intensity is higher than 10^15 W/cm^2.

关键词： hot electrons laser plasma interactions stimulated Raman scattering

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等离子体中Fokker-Planck方程的有限元模拟

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计算物理 2007年第2期24卷 134-140页

作者：翁苏明盛政明中国科学院物理研究所光物理实验室北京100080

利用有限元方法设计了一套相对简单明了的求解Fokker-Planck方程的方案.这个方案不必严格限制计算格点的步长和时间步长,就可以确保分布函数的非负性和粒子数的守恒.通过一维程序模拟,进一步证实了这个方案的可靠性.对于多维问题的分析... 详细信息

利用有限元方法设计了一套相对简单明了的求解Fokker-Planck方程的方案.这个方案不必严格限制计算格点的步长和时间步长,就可以确保分布函数的非负性和粒子数的守恒.通过一维程序模拟,进一步证实了这个方案的可靠性.对于多维问题的分析和一维问题完全一样,所以非常容易将其推广到多维问题.

关键词： Fokker-Planck方程有限元方法等离子体 Legendre展开式

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激光等离子体尾波加速器的发展和展望

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强激光与粒子束 2020年第9期32卷 3-13页

作者：陈民刘峰李博原翁苏明陈黎明盛政明张杰上海交通大学物理与天文学院激光等离子体教育部重点实验室上海200240 上海交通大学IFSA协同创新中心上海200240

超强激光在气体等离子体中传输时可以激发出大振幅的电子等离子体尾波。激光等离子体尾波加速器是利用该尾波对带电粒子(特别是电子和正电子)进行加速的一种新型装置。由于其加速梯度相较于现有的常规加速器可以提升1000倍,为建造超紧... 详细信息

超强激光在气体等离子体中传输时可以激发出大振幅的电子等离子体尾波。激光等离子体尾波加速器是利用该尾波对带电粒子(特别是电子和正电子)进行加速的一种新型装置。由于其加速梯度相较于现有的常规加速器可以提升1000倍,为建造超紧凑型的加速器和辐射源奠定了基础,也为将来建造基于等离子体的超高能正负电子对撞机和自由电子激光装置提供了可能。对该新型加速器的原理、特点、发展历程,尤其是近十年来的主要进展和未来发展趋势及面临的主要挑战进行简要梳理和介绍。

关键词：激光等离子体激光加速激光等离子体尾波超紧凑型加速器新型辐射源

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激光等离子体不稳定性及其抑制方案研究

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强激光与粒子束 2021年第1期33卷 108-124页

作者：余诗瀚李晓锋翁苏明赵耀马行行陈民盛政明上海交通大学物理与天文学院激光等离子体实验室上海200240 上海交通大学IFSA协同创新中心上海200240 中国科学院上海光学精密机械研究所高功率激光物理联合实验室上海201800

受激拉曼散射、受激布里渊散射等激光等离子体不稳定性(LPI)是激光等离子体物理领域最重要的研究课题之一。特别是在激光驱动的惯性约束聚变中,LPI会造成相当份额的激光能量损失,破坏辐射对称性,产生的超热电子还会预热靶丸,进而影响压... 详细信息

受激拉曼散射、受激布里渊散射等激光等离子体不稳定性(LPI)是激光等离子体物理领域最重要的研究课题之一。特别是在激光驱动的惯性约束聚变中,LPI会造成相当份额的激光能量损失,破坏辐射对称性,产生的超热电子还会预热靶丸,进而影响压缩效率和聚变能量增益。近期,在美国国家点火装置上开展的实验表明对LPI物理过程的充分理解和有效控制对成功实现ICF点火至关重要。我们对近期LPI方面的一系列研究进展进行了简单介绍与讨论。首先,回顾了描述LPI过程的三波耦合理论,由此得出了LPI在线性阶段的增长率。接着讨论了一些复杂情景下的LPI物理过程,譬如LPI的非线性发展阶段、级联LPI、多光束LPI以及LPI间的非线性耦合。最后,着重介绍了一系列抑制LPI的技术方案,包括束匀滑技术、光束时域整形、宽带激光、偏振旋转激光以及外加磁场等。

关键词：激光等离子体不稳定性惯性约束聚变受激拉曼散射受激布里渊散射宽带激光

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