The National Ignition Facility (NIF) currently under construction at the University of California Lawrence Livermore National Laboratory (LLNL) is a 192-beam, 1.8-megajoule, 500-terawatt, 351-nm laser for inertial confinement fusion (ICF) and high-energy-density experimental studies. NIF is being built by the Department of Energy and the National Nuclear Security Agency (NNSA) to provide an experimental test bed for the U.S. Stockpile Stewardship Program to ensure the country's nuclear deterrent without underground nuclear testing. The experimental program will encompass a wide range of physical phenomena from fusion energy production to materials science. Of the roughly 700 shots available per year, about 10% will be dedicated to basic science research. Laser hardware is modularized into line replaceable units (LRUs) such as deformable mirrors, amplifiers, and multi-function sensor packages that are operated by a distributed computer control system of nearly 60,000 control points. The supervisory control room presents facility-wide status and orchestrates experiments using operating parameters predicted by physics models. A network of several hundred front-end processors (FEPs) implements device control. The object-oriented software system is implemented in the Ada and Java languages and emphasizes CORBA distribution of reusable software objects. NIF is currently scheduled to provide first light in 2004 and will be completed in 2008.
The National Ignition Facility(NIF) megajoule laser at the Lawrence Livermore National Laboratory(LLNL)\cite{moses} has produced a significant amount of useful physics results related to inertial confinement fusion since it began operating in 2010. However, achievement of its primary goal of generating ignition in a thermonuclear plasma has proven elusive, and measured yields were far below those expected from an ignited, and burning, plasma. The reason for the limited yields has not been explained in detail. This work proposes, and shows support for, the possibility that the low yields may be…
Comparison of the Recently proposed Super Marx Generator Approach to Thermonuclear Ignition with the DT Laser Fusion-Fission Hybrid Concept by the Lawrence Livermore National Laboratory
Fast magnetic reconnection was observed between magnetized laser-produced plasmas at the National Ignition Facility. Two highly-elongated plasma plumes were produced by tiling two rows of lasers, with magnetic fields generated in each plume by the Biermann battery effect. Detailed magnetic field observations, obtained from proton radiography using a D$^3$He capsule implosion, reveal reconnection occurring in an extended, quasi-1D current sheet with large aspect ratio $\sim 100$. The 1-D geometry allowed a rigorous and unique reconstruction of the magnetic field, which showed a reconnection cur…
The Rayleigh-Taylor (RT) instability affects a vast range of High Energy Density (HED) length scales, spanning from supernova explosions (10$^{13}$ m) to inertial confinement fusion (10$^{-6}$ m). In inertial confinement fusion, the RT instability is known to induce mixing or turbulent transition, which in turn cools the hot spot and hinders ignition. The fine-scale features of the RT instability, which are difficult to image in HED physics, may help determine if the system is mixing or is transitioning to turbulence. Earlier diagnostics lacked the spatial and temporal resolution necessary to …
Hot Spot Evolution Measured by High-Resolution X-Ray Spectroscopy at the National Ignition Facility
Princeton Plasma Physics Laboratory, Princeton University（普林斯顿等离子体物理实验室，普林斯顿大学）；Lawrence Livermore National Laboratory（劳伦斯利弗莫尔国家实验室）；Laboratory for Laser Energetics, University of Rochester（罗切斯特大学激光能源实验室）
Absolute Calibration of a Time-Resolved High Resolution X-ray Spectrometer for the National Ignition Facility (invited)
Princeton Plasma Physics Laboratory, Princeton University（普林斯顿等离子体物理实验室，普林斯顿大学）；Lawrence Livermore National Laboratory（劳伦斯利弗莫尔国家实验室）；Laboratory for Laser Energetics, University of Rochester（罗切斯特大学激光能源实验室）
Electron-positron pairs, produced in intense laser-solid interactions, are diagnosed using magnetic spectrometers with image plates, such as the National Ignition Facility (NIF) Electron Positron Proton Spectrometers (EPPS). Although modeling can help infer the quantitative value, the accuracy of the models needs to be verified to ensure measurement quality. The dispersion of low-energy electrons and positrons may be affected by fringe magnetic fields near the entrance of the EPPS. We have calibrated the EPPS with six electron beams from a Siemens Oncor linear accelerator (linac) ranging in en…
Modulated deuteron spectra observed with the Magnetic Recoil neutron Spectrometer at the National Ignition Facility
Imperial College London（帝国理工学院）；Massachusetts Institute of Technology（麻省理工学院）；Lawrence Livermore National Laboratory（劳伦斯利弗莫尔国家实验室）；General Atomics（通用原子能公司）；Los Alamos National Laboratory（洛斯阿拉莫斯国家实验室）；Laboratory for Laser Energetics（激光能源实验室）
Magnetic fields spontaneously grow at unstable interfaces around hot-spot asymmetries during inertial confinement fusion implosions. Although difficult to measure, theoretical considerations and numerical simulations predict field strengths exceeding 5kT in current national ignition facility experiments. Magnetic confinement of electrons then reduces the hot-spot heat loss by >5%. We demonstrate this via magnetic post-processing of two-dimensional xRAGE hydrodynamic simulation data at bang time. We then derive a model for the self-magnetization, finding that it varies with the square of the st…
We report the first measurement of the $^{10}{\rm B}(α,n)^{13}{\rm N}$ reaction in a polar-direct-drive exploding pusher (PDXP) at the National Ignition Facility (NIF). This work is motivated by the need to develop alternative mix diagnostics, radiochemistry being the focus here. The target is composed of a $65/35\,\rm at.\,\%$ deuterium-tritium (DT) fill surrounded by a roughly $30\,μ\rm m$ thick beryllium ablator. The inner portion of the beryllium ablator is doped with $10\,\rm at.\,\%$ of $^{10}{\rm B}$. Radiation-hydrodynamics calculations were performed in 1D to optimize both the remaini…
As an alternative inertial confinement fusion scheme with predicted high energy gain and more robust designs, shock ignition requires a strong converging shock driven by a shaped pulse with a high-intensity spike at the end to ignite a pre-compressed fusion capsule. Understanding nonlinear laser-plasma instabilities in shock ignition conditions is crucial to assess and improve the laser-shock energy coupling. Recent experiments conducted on the OMEGA-EP laser facility have for the first time demonstrated that such instabilities can $\sim$100\% deplete the first 0.5 ns of the high-intensity las…
We report results and modelling of an experiment performed at the TAW Vulcan laser facility, aimed at investigating laser-plasma interaction in conditions which are of interest for the Shock Ignition scheme to Inertial Confinement Fusion, i.e. laser intensity higher than 10^16 W/cm2 impinging on a hot (T > 1 keV), inhomogeneous and long scalelength preformed plasma. Measurements show a significant SRS backscattering (4 - 20% of laser energy) driven at low plasma densities and no signatures of TPD/SRS driven at the quarter critical density region. Results are satisfactorily reproduced by an ana…
Ray-based calculations of backscatter in laser fusion targets
本文提出了一个非均匀等离子体布里渊散射和拉曼散射的一维稳态模型。子等离子体波被处理在强阻尼限制，并具有由（线性）动力学响应的有质动力驱动的振幅。包括泵浦损耗，逆韧致辐射阻尼，韧致辐射发射，汤姆逊散射密度波动，和整个光束聚焦。描述了实现该模型的数字代码DEPPENDIX。该模型与传统的线性增益计算，以及“平面波”模拟与近轴传播代码PF3D。与OMEGA激光装置上布里渊散射实验的比较[T. R. Boehly等人，光学通信133，p.495（1997）]表明，激光散斑大大增强了反射率，超过了DEPTOND结果。由相位共轭激发的这种增强的近似上限，给出了通过加倍的DEPtrons耦合系数。国家点火装置（NIF）点火设计的分析与设计[J. A. Paisner，E. M. Campbell和W. J.Hogan，Fusion Technol.26，p.755（1994）]，峰值辐射温度为285 eV，显示出极低的反射率。拉曼光的再吸收在该设计中被认为是显著的。
Recent experiments on the National Ignition Facility [D.E. Hinkel et al., Phys. Rev. Lett. 117, 225002 (2016)] demonstrates that utilizing a long, large case-to-capsule ratio (=3) conventional cylindrical hohlraum at moderate gas-fill density (=0.6 mg/cm3 4He) improves the drive symmetry controaums has a little chance to achieve ignition at an acceptable energy level due to its small margin for the laser cone propagation. In this letter, a noncylindrical hohlraum, called as peanut hohlraum, using a larger case-to-capsule (=3.46) at lower gas-fill density (=0.3 mg/cm3 4He) is proposed to ignite…
We present simulations of ignition and burn based on the Highfoot and High-Density Carbon indirect drive designs of the National Ignition Facility for three regimes of alpha-heating - self-heating, robust ignition and propagating burn - exploring hotspot power balance, perturbations and hydrodynamic scaling. A Monte-Carlo Particle-in-Cell charged particle transport package for the radiation-magnetohydrodynamics code Chimera was developed for this work. Hotspot power balance between alpha-heating, electron thermal conduction and radiation was studied in 1D for each regime, and the impact of per…
Driver at 10 MJ and 1 shot/30min for inertial confinement fusion at high gain: efficient, compact, low-cost, low laser-plasma instabilities, beam-color selectable from 2 omega/3 omega/4 omega, applicable to multiple laser fusion schemes
With the advent of high power lasers, new opportunities have opened up for simulating astrophysical processes in the laboratory. We show that 2nd-order Fermi acceleration can be directly investigated at the National Ignition Facility, Livermore. This requires measuring the momentum-space diffusion of 3 MeV protons produced within a turbulent plasma generated by a laser. Treating Fermi acceleration as a biased diffusion process, we show analytically that a measurable broadening of the initial proton distribution is then expected for particles exiting the plasma.
The results of numerical and theoretical studies of the gain of direct-drive inertial confinement fusion (ICF) target, which includes a kinetic description of energy transfer by laser-accelerated fast electrons, are presented. The range of initial temperature of fast electrons and fraction of laser energy contained in these particles were chosen based on the results of recent experiments at the National Ignition Facility (NIF).The effect of 'wandering' of fast electrons is taken into account. It is due to a remoteness of the region of fast electron generation from the ablation surface of implo…
The study of parametric instabilities has played a crucial role in understanding energy transfer to plasma and, with that, the development of key applications such as inertial confinement fusion. When the densities are between $0.108n_c\lesssim n_e\lesssim 0.138n_c$ and the electron temperature is $T_e=$2.5 keV, anomalous hot electrons with kinetic energies above 100 keV are generated. Here, a new electron acceleration mechanism - the anti-Stokes Langmuir decay instability cascade of forward stimulated Raman scattering - is investigated. This mechanism not only explains anomalous energetic ele…
For the successful generation of ion-beam-driven high energy density matter and heavy ion fusion energy, intense ion beams must be transported and focused onto a target with small spot size. One of the successful approaches to achieve this goal is to accelerate and transport intense ion charge bunches in an accelerator and then focus the charge bunches ballistically in a section of the accelerator that contains a neutralizing background plasma. This requires the ability to control space-charge effects during un-neutralized (non-neutral) beam transport in the accelerator and transport sections,…
