Bulletin of the American Physical Society
64th Annual Meeting of the APS Division of Plasma Physics
Volume 67, Number 15
Monday–Friday, October 17–21, 2022; Spokane, Washington
Session QI02: Pulsed Power Driven Fusion and HED DiagnosticsLive Streamed
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Chair: Eric Harding, Sandia National Lab Room: Ballroom 100 B |
Wednesday, October 19, 2022 3:00PM - 3:30PM |
QI02.00001: Magnetized Liner Inertial Fusion: Developing a data-driven understanding of magnetic flux compression from computation through experiment Invited Speaker: William E Lewis The Magnetized Liner Inertial Fusion (MagLIF) concept studied at Sandia National Laboratories Z facility achieves fusion relevant conditions by delivering current to magnetically compress a cylindrical beryllium liner containing a preheated and pre-magnetized fusion fuel. Improvements to magnetic field coils, laser preheat, and current coupling have led to increased performance. However, experimental measurements are non-linearly dependent on several physical parameters and are highly integrated in the spatial and/or temporal domains. Furthermore, regular application of high-fidelity simulations that capture such unresolved effects in analyzing this data is hampered by high computational costs. The application of modern data-driven techniques is critical to addressing these challenges and advancing our understanding. We demonstrate several data science tools that enable the extraction and interpretation of flux compression at stagnation and inform our understanding of current open questions. We present a Bayesian inference of magnetization of the stagnated fuel plasma for an ensemble of MagLIF experiments, achieved by the application of a deep-learned surrogate of a costly physics simulation. For a subset of the experiments, flux is consistent with scaling of the Nernst effect with preheat-specific-energy (PSE) from 2D simulations. We also observe significantly increased fuel magnetization at the same PSE in experiments using dielectric-coated liners with a higher liner aspect ratio. This may indicate the importance of 3D effects and/or effective compression of the fuel. We discuss a recently developed deep-learning-based image preprocessing tool, an experimental-data-driven image metric design, and surrogate modeling efforts relevant for understanding open questions around impact of 3D effects on flux compression from both simulation and experiment. |
Wednesday, October 19, 2022 3:30PM - 4:00PM |
QI02.00002: Developing solid cryogenic fuel configurations for magnetic direct drive inertial confinement fusion targets Invited Speaker: Thomas J Awe Solid deuterium and deuterium-tritium (DT) fuels are used in a range of thermonuclear fusion platforms. Within inertial confinement fusion (ICF) targets, solid DT surrounds gaseous fuel. Upon stagnation, thermonuclear reaction products from the central plasma initiate a radially propagating burn wave, increasing fusion yield. The ICF program and Sandia National Laboratories (SNL) studies magnetically imploded cylindrical liners on the 20-MA, 100-ns Z Facility (Z). For example, Magnetized Liner Inertial Fusion (MagLIF) implosions produce greater than 1013 DD neutrons [1]. Solid fuel layers can benefit MagLIF both on Z and on a future driver. On Z, a solid fuel layer placed on the inner surface of the liner can reduce mix-enhanced radiation losses by buffering the plasma from the metal wall. On a higher-current driver, millimeters-thick DT ice placed on the liner's inner wall provides layered fuel for high gain “ice burner” MagLIF target designs [2]. Controlled growth of thin and thick deuterium ice shells has been demonstrated using a desublimation process, where a slow flow of gas enters the target and freezes to the walls. Such layers may also be grown with uniformly distributed spectroscopic dopants (e.g., Kr), but the gas-fill tube must be held warm to avoid inadvertently cryopumping the dopant before reaching the target. Solid-fuel fibers are also of interest. For example, a current-carrying fiber can be used to generate the central plasma target to be compressed by a metallic liner in a magnetized target fusion system. A screw-driven deuterium-ice-rod extruder [3] has been commissioned on the Z Facility in two recent experiments, demonstrating the technology needed for such fuel configurations. |
Wednesday, October 19, 2022 4:00PM - 4:30PM |
QI02.00003: Single-shot 256-frame Radiography Measurements of Pulsed Power Driven Instability Growth in Converging and Diverging Geometries Invited Speaker: Jergus Strucka The dynamics of HED plasmas are dominated by instabilities - in astrophysics, these govern the structure of protostellar jets and nebulae; on Earth, the success of ICF experiments depends on the reduction of mixing of cold, dense, high Z plasma into fusion fuel. Measuring the evolution of hydrodynamic instabilities is vital to quantitative validation of theory and simulations, yet many experiments are limited to exploring a small region of parameter space, or provide only few measurements per experiment, requiring control of the initial conditions. |
Wednesday, October 19, 2022 4:30PM - 5:00PM |
QI02.00004: Advances in hybrid-CMOS X-ray framing cameras for High-Energy-Density science research Invited Speaker: John Porter High-speed X-ray cameras are powerful tools for visualizing complex plasma dynamics and measuring fundamental plasma properties. The microelectronics revolution has enabled the creation of solid-state x-ray framing cameras with speeds approaching a nanosecond, spatial resolution of 10’s of microns, and high quantum efficiency X-ray sensors for direct X-ray detection up to several 10’s of keV. By storing multiple images in each pixel this technology makes it possible to capture a high-resolution 2-dimensional image sequence along a single line-of-sight. A family of hybrid-CMOS digital framing cameras has been developed by a large team of scientists and engineers at SNL, LLNL, and private industry that is now in use at the large-scale ICF facilities. These cameras are being used to study hohlraum dynamics with the GLEH diagnostic on NIF and LMJ, measure the detailed opacity of iron plasmas on Z, measure dynamic material phase transitions with a new time-resolved X-ray diffraction diagnostic on NIF, evaluate laser preheating of MagLIF targets for experiments on Z, and enable operation of traditional X-ray streak cameras on neutron producing experiments using the hDISC diagnostic on Omega and NIF. These cameras are also a key component of pulse-dilation imaging tubes in use on Omega and NIF that have demonstrated temporal resolution as fast as 25 picoseconds. They also show great promise for being robust to operation in the high radiation environments produced by igniting plasmas. A description of the hybrid-CMOS camera technology will be given along with examples of HED plasma research that highlight the unique capabilities of this new scientific instrument. |
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