G. N. Hall
A5018975378- Laser-Plasma Interactions and Diagnostics
- Laser-induced spectroscopy and plasma
- Magnetic confinement fusion research
- Gamma-ray bursts and supernovae
- High-pressure geophysics and materials
- Atomic and Molecular Physics
- Laser-Matter Interactions and Applications
- Solar and Space Plasma Dynamics
- Ionosphere and magnetosphere dynamics
- Pulsed Power Technology Applications
- Astrophysics and Star Formation Studies
- Plasma Diagnostics and Applications
- Astrophysics and Cosmic Phenomena
- Fluid Dynamics and Turbulent Flows
- Nuclear Physics and Applications
- Electromagnetic Launch and Propulsion Technology
- Combustion and Detonation Processes
- Plasma and Flow Control in Aerodynamics
- Particle Dynamics in Fluid Flows
- Energetic Materials and Combustion
- Astrophysical Phenomena and Observations
- Ion-surface interactions and analysis
- Gas Dynamics and Kinetic Theory
- Dust and Plasma Wave Phenomena
- Semiconductor Lasers and Optical Devices
Lawrence Livermore National Laboratory
2016-2025
General Atomics (United States)
2021
Imperial College London
2007-2016
University of Manchester
2002-2016
University of Warwick
2013
CEA Gramat
2009
University of California, San Diego
2009
Cornell University
2009
Sandia National Laboratories
2009
Observatoire de Paris
2009
Abstract Obtaining a burning plasma is critical step towards self-sustaining fusion energy 1 . A one in which the reactions themselves are primary source of heating plasma, necessary to sustain and propagate burn, enabling high gain. After decades research, here we achieve burning-plasma state laboratory. These experiments were conducted at US National Ignition Facility, laser facility delivering up 1.9 megajoules pulses with peak powers 500 terawatts. We use lasers generate X-rays radiation...
Abstract In a burning plasma state 1–7 , alpha particles from deuterium–tritium fusion reactions redeposit their energy and are the dominant source of heating. This has recently been achieved at US National Ignition Facility 8 using indirect-drive inertial-confinement fusion. Our experiments use laser-generated radiation-filled cavity (a hohlraum) to spherically implode capsules containing deuterium tritium fuel in central hot spot where occur. We have developed more efficient hohlraums...
Since the start of 'nuclear age' graphite has been employed as a moderator in around 100 nuclear reactors, and today there are still some 30 graphite-moderated reactors operating plans for new Generation IV high-temperature reactors. Many now producing power beyond their original design life. Therefore cases, to aid reactor operators designers, existing irradiation databases need be extended either higher temperature or neutron fluence. Furthermore, data needed different grades that...
Abstract Indirect Drive Inertial Confinement Fusion Experiments on the National Ignition Facility (NIF) have achieved a burning plasma state with neutron yields exceeding 170 kJ, roughly 3 times prior record and necessary stage for igniting plasmas. The results are despite multiple sources of degradations that lead to high variability in performance. Results shown here, first time, include an empirical correction factor mode-2 asymmetry regime addition previously determined corrections...
We present the first results of high energy density laboratory astrophysics experiments which explore evolution collimated outflows and jets driven by a toroidal magnetic field. The are scalable to astrophysical flows in that critical dimensionless numbers such as Mach number, plasma β Reynolds number all astrophysically appropriate ranges. Our use MAGPIE pulsed power machine allow us role pressure creating collimating outflow well showing creation central jet within broader cavity. show...
The evolution of laboratory produced magnetic jets is followed numerically through three-dimensional, nonideal magnetohydrodynamic simulations. experiments are designed to study the interaction a purely toroidal field with an extended plasma background medium. system observed evolve into structure consisting approximately cylindrical cavity embedded magnetically confined jet on its axis. supersonic expansion produces shell swept-up shocked that surrounds and partially confines tower....
This paper reviews scientific results from the pursuit of indirect drive ignition on National Ignition Facility (NIF) and describes program's forward looking research directions. In NIF, laser beams heat an x-ray enclosure called a hohlraum that surrounds spherical pellet. X-ray radiation ablates surface pellet, imploding thin shell deuterium/tritium (DT) must accelerate to high velocity (v > 350 km s−1) compress by factor several thousand. Since 2009, substantial progress has been made in...
Indirect drive inertial confinement fusion experiments were conducted at the National Ignition Facility to investigate performance of hohlraum as a function gas fill density by imploding high-density-carbon capsules using 2-shock laser pulse. Measurements characterized backscatter behavior, production hot electrons, motion and brightness spots on wall, efficiency x-ray ρgf between 0.03 mg/cc (“near vacuum”) 1.6 mg/cc. For hohlraums with up 0.85 mg/cc, very little stimulated Raman (SRS) was...
The interface between the capsule ablator and fuel ice layer is susceptible to hydrodynamic instabilities. subsequent mixing of hot material into reduces compression at stagnation a candidate for reduced performance. ability diagnose ice–ablator mix critical understanding improving stability this interface. Combining crystal backlighter imager with single line sight camera on National Ignition Facility (NIF) allows direct measurement by providing multiple quasi-monochromatic radiographs...
A review of recent experiments on the MAGPIE generator (1 MA, 250 ns) aimed at studying implosion dynamics wire array Z-pinches is presented. The first phase dominated by gradual ablation stationary cores and redistribution mass precursor plasma flow. It found that rate depends magnitude global (collective) magnetic field array, increases with field. existence modulation along wires leads to presence a 'trailing' left behind imploding current sheath. trailing provides an alternative path for...
A series of experiments has been conducted in order to investigate the azimuthal structures formed by interactions cylindrically converging plasma flows during ablation phase aluminium wire array Z pinch implosions. These were carried out using 1.4 MA, 240 ns MAGPIE generator at Imperial College London. The main diagnostic used this study was a two-colour, end-on, Mach-Zehnder imaging interferometer, sensitive axially integrated electron density plasma. data collected these reveal strongly...
A suite of laser based diagnostics is used to study interactions magnetised, supersonic, radiatively cooled plasma flows produced using the Magpie pulse power generator (1.4 MA, 240 ns rise time). Collective optical Thomson scattering measures time-resolved local flow velocity and temperature across 7–14 spatial positions. The spectrum recorded from multiple directions, allowing more accurate reconstruction vectors. areal electron density measured 2D interferometry; optimisation analysis are...
Hydrodynamic instabilities are a major factor in degradation of inertial confinement fusion (ICF) implosions. In the highest performing implosions on National Ignition Facility, yield amplification (YA) due to alpha particle heating approached ∼3, while YA ∼15–30 is needed for ignition. Understanding and mitigation critical achieving This article reviews several experimental platforms that have been developed directly measure these all phases ICF Measurements ripple-shock propagation at...
High-resolution, high-energy X-ray backlighters are very active area of research for radiography experiments at the National Ignition Facility (NIF) [Miller et al., Nucl. Fusion 44, S228 (2004)], in particular those aiming obtaining Compton-scattering produced radiographs from cold, dense fuel surrounding hot spot. We report on to generate and characterize point-projection-geometry using short pulses advanced radiographic capability (ARC) [Crane J. Phys. 244, 032003 (2010); Di Nicola Proc....
The implosion efficiency in inertial confinement fusion depends on the degree of stagnated fuel compression, density uniformity, sphericity, and minimum residual kinetic energy achieved. Compton scattering-mediated 50--200 keV x-ray radiographs indirect-drive cryogenic implosions at National Ignition Facility capture dynamic evolution as it goes through peak revealing low-mode 3D nonuniformities thicker with lower than simulated. By differencing two taken different times during same...
In inertial confinement fusion (ICF) implosions, the interface between cryogenic DT fuel and ablator is unstable to shock acceleration (the Richtmyer-Meshkov instability, RM) constant (Rayleigh-Taylor RT). Instability growth at this can reduce final compression, limiting burnup. If in direction of lighter material (negative Atwood number), RT instability produces oscillatory motion that stabilize against RM growth. Theory simulations suggest scenario occurred early times some ICF experiments...
Collimated outflows (jets) are ubiquitous in the universe, appearing around sources as diverse protostars and extragalactic supermassive black holes. Jets thought to be magnetically collimated, launched from a magnetized accretion disk surrounding compact gravitating object. We have developed first laboratory experiments address time-dependent, episodic phenomena relevant poorly understood jet acceleration collimation region. The experimental results show periodic ejections of magnetic...
The Crystal Backlighter Imager (CBI) is a quasi-monochromatic, near-normal incidence, spherically bent crystal imager developed for the National Ignition Facility (NIF), which will allow inertial confinement fusion capsule implosions to be radiographed close stagnation. This not possible using standard pinhole-based area-backlighter configuration, as self-emission from hotspot overwhelms backlighter signal in final stages of implosion. CBI mitigates broadband hot spot by extremely narrow...
We present measurements of ice-ablator mix at stagnation inertially confined, cryogenically layered capsule implosions. An ice layer thickness scan with layers significantly thinner than used in ignition experiments enables us to investigate near the inner ablator interface. Our reveal for first time that majority atomically mixed material is ``dark'' mix. It seeded by interface instability and located relatively cooler, denser region fuel assembly surrounding fusion hot spot. The amount...
While nuclear fusion ignition has been achieved at the National Ignition Facility in inertial confinement (ICF) experiments, obtaining higher gain and more efficient burn is still desired. In that regard, increasing compression of fuel an important factor. recent indirect-drive capsule implosions, SQ-n campaign testing hypothesis reducing hydrodynamic growth perturbations key to achieving high-density carbon based-ablators for ICF. uses a design lower adiabat with ramped foot laser pulse...
We present results of high energy density laboratory experiments on the production supersonic radiatively cooled plasma jets with dimensionless parameters (Mach number ∼30, cooling parameter ∼1 and contrast ρj/ρa ∼ 10) similar to those in young stellar objects jets. The are produced using two modifications wire array Z-pinch driven by 1 MA, 250 ns current pulse MAGPIE facility at Imperial College, London. In first set purely hydrodynamic used study deflection cross-wind, including structure...
This paper summarizes the present understanding of processes leading to precursor column formation in cylindrical wire arrays on 1 MA MAGPIE generator at Imperial College London. Direct experimental measurements diameter variation during collapse and phase are presented, along with soft x-ray emission, quantitative radiography. In addition, data from twisted presented which give additional information behavior coronal plasma generated array z pinches. Three stages identifiable data: broad...
An inverse (exploding) wire array configuration, in which the wires form a cylinder around current carrying electrode on axis, was used to study ablation phase of wires. This configuration allows parameters plasma from individual be measured as ablated streams propagate outward radial direction. The density distribution and evolution natural mode modulation flow with interferometry soft x-ray imaging. Measurements voltage across array, this is determined by private magnetic flux wires, allow...
We present experimental results of the formation magnetically driven plasma jets, showing for first time a way producing episodic jet/ouflows in laboratory. The jets are produced using 6.5 μm thick aluminum disk (a radial foil), which is subjected to 1 MA, 250 ns current pulse from MAGPIE generator [I. H. Mitchell et al., Rev. Sci. Instrum. 67, 1533 (1996)]. early motion foil characterized by bulk mass due magnetic pressure, together with surface following direction J×B force. A low density...
A new wire array configuration has been used to create thin shell-like implosions in a cylindrical array. The setup introduces $\ensuremath{\sim}5\text{ }\text{ }\mathrm{kA}$, $\ensuremath{\sim}25\text{ }\mathrm{ns}$ current prepulse followed by $\ensuremath{\sim}140\text{ current-free interval before the application of main ($\ensuremath{\sim}1\text{ }\mathrm{MA}$) pulse. volumetrically heats wires which expand $\ensuremath{\sim}1\text{ }\mathrm{mm}$ diameter leaving no dense core and...