Bulletin of the American Physical Society
60th Annual Meeting of the APS Division of Plasma Physics
Volume 63, Number 11
Monday–Friday, November 5–9, 2018; Portland, Oregon
Session BM9: Mini-Conference on Magneto-inertial Fusion Science and Technology I |
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Chair: Kyle Peterson, Sandia National Laboratories Room: OCC C123 |
Monday, November 5, 2018 9:30AM - 9:50AM |
BM9.00001: Spherically Imploding Plasma Liners as a Standoff Magneto-Inertial-Fusion Driver S. Hsu, S. Langendorf, J. Dunn, K. Yates, M. Gilmore, Y. C. Thio, F. Witherspoon, E. Cruz, S. Brockington, A. Case, M. Luna, A. Williams, J. Cassibry, K. Schillo, R. Samulyak, W. Shih, P. Stoltz Spherically imploding plasma liners formed by merging hypersonic plasma jets are a proposed compression driver for magneto-inertial fusion (MIF). Under the ARPA-E ALPHA program, the Plasma Liner Experiment--ALPHA (PLX-$\alpha$) plans to culminate in forming spherically imploding sub-fusion-scale plasma liners [1] via 36 merging hypersonic plasma jets (with initial $n_i \sim 2\times 10^{16}$~cm$^{-3}$, $v_{\rm jet} \approx$ 50~km/s, mass $\sim 1$~mg, and various gas species). We summarize experimental results on the formation of a conical section of spherically imploding plasma liners by merging six [2] and seven plasma jets. Data from fast-framing-cameras, visible spectrometers, and a multi-chord interferometer have been analyzed to assess (i) ion heating (and associated liner-Mach-number degradation) due to collisional shock formation between merging jets [3], and (ii) liner uniformity upon jet merging. These data are benchmarking code calculations, which will set requirements on fusion-scale plasma liners. [1] S. C. Hsu and Y. C. F. Thio, J. Fusion Energ.~{\bf 37}, 103 (2018); [2] S. C. Hsu et al., {\em IEEE Trans.\ Plasma Sci.}~{\bf 46}, 1951 (2018); [3] S. J. Langendorf et al., submitted (2018); https://arxiv.org/abs/1805.09933. |
Monday, November 5, 2018 9:50AM - 10:10AM |
BM9.00002: Coaxial Plasma Gun Development for Plasma-Jet-Driven Magneto-Inertial Fusion (PJMIF) Y.C.F. Thio, F. Witherspoon, E. Cruz, S. Brockington, Andrew Case, Ajoke Williams, M. Luna PJMIF requires high-Z (e.g. Xe) plasma jets with velocity above 50 km/s, particle density > 1017 per cc, Mach number > 15, jet length < 5 cm, jet- to-jet variations in mass of less than 5% and launch time of less than 200 ns, with high degree of density and velocity uniformity within the jet. The deflagration and snow-plow acceleration of plasma tend to produce long jets. The plasma may be accelerated in the slab mode, with suitably contoured electrodes to avoid the blow-by instability. The plasma gun has undergone two generations of development. Development of a third generation of the gun (HJ1) is underway to meet the needs of PLX-a, an experiment to form a spherical plasma liner. The major components of the gun are the capacitor module, the PFN, the gun electrodes, the gas valve, the switch, and the pre-ionizer. Highlights of the development and the test data for these various components and the integrated system will be presented and discussed. |
Monday, November 5, 2018 10:10AM - 10:30AM |
BM9.00003: Observation and analysis of thermonuclear neutron production in a sheared-flow-stabilized Z-pinch Elliot L Claveau, Uri Shumlak, Eleanor G Forbes, Raymond Golingo, Brian A Nelson, Anton Stepanov, Tobin R Weber, Yue Zhang, Harry Scott McLean, Drew P Higginson, James M Mitrani Sustained neutron production has been demonstrated on the Fusion Z-pinch Experiment (FuZE), a sheared-flow-stabilized Z-pinch device. Measurements indicate that neutron production is primarily the result of thermonuclear processes. FuZE produces 0.3 cm radius by 50 cm long Z-pinches using D2/H2 or D2/He fill gas mixtures, with up to 20% D2. The plasma columns are magnetically compressed by a 200 kA plasma current, resulting in 1 - 2 keV ion temperatures and >1017 cm-3 densities, during a 20 μs quiescent period when magnetic fluctuations are diminished. The Z-pinch plasmas are stabilized by an embedded radially-sheared axial flow, a method proposed in Shumlak and Hartman PRL 1995 and demonstrated experimentally in other sheared flow stabilized Z-pinch devices, ZaP and ZaP-HD. Within the quiescent period, sustained neutron production is observed for a duration of approximately 5 μs, hundreds of times longer than the 20 ns instability growth time for a static Z-pinch at FuZE plasma parameters. The measured neutron yield is >105 neutrons/pulse, agreeing with predictions from D-D fusion reaction rates. The number of observed counts scales with the square of the deuterium concentration, suggesting a thermonuclear fusion process. |
Monday, November 5, 2018 10:30AM - 10:50AM |
BM9.00004: Sheared-flow Stabilized Z-Pinch Reactor Embodiment Brian Nelson, Z T Draper, H S McLean, U Shumlak, E L Claveau, E G Forbes, R P Golingo, D P Higginson, J M Mitrani, A D Stepanov, K K Tummel, T R Weber, Y Zhang The sheared-flow stabilized (SFS) Z-pinch has demonstrated long-length and long-lived Z-pinches with T_i ~ 1-2 keV, n_e > 10^23 m^-3, for 100s of MHD instability growth times. The fusion Z-pinch experiment, FuZE, has shown neutron production over periods of 5-8 us when operated with a 20% D/80% H or He mixture. Yield calculations are >10^5 neutrons per pulse, agreeing with cross-section estimates and scaling as the square of the D concentration. Reactor embodiment for the SFS Z-pinch reactor consists of a vertically-oriented pinch in a cavity formed by Li-Pb flowing over a weir wall. Li-Pb serves as the Z-pinch outer electrode, heat transfer material, tritium breeding blanket, and biological shield. MCNP is used to calculate neutron transport, including the tritium breeding ratio (TBR). Configurations have been found reaching the goal of TBR > 1.1 with the 17% Li/83% Pb eutectic and natural Li-6 enrichment of 7.5%. A model is under development to calculate the time required to build up tritium inventory when starting with D-D operation. Bred tritium is introduced into the deuterium fuel stock, increasing the net TBR, bootstrapping the reactor to 50% D / 50% T. SFS Z-pinch background, results, and reactor embodiment studies will be presented. |
Monday, November 5, 2018 10:50AM - 11:10AM |
BM9.00005: Overview of Staged Magnetic Compression of FRC targets David Kirtley, Richard Milroy, George Votroubek, John Slough, Erik McKee, Aki Shimazu, Andrew Hine, Daniel Barnes Helion Energy is building several fusion systems, based on Staged Magnetic Compression of Field Reverse Configurations (FRC). The FRC is a high-Beta compact toroid that may lead to fusion power plants with linear topologies, high power density, and direct energy recovery that minimize the reactor engineering and environmental concerns of fusion energy. Presented is an overview of Helion’s approach and an update on the ARPA-E research program, Staged Magnetic Compression of FRC Targets to Fusion Conditions. In this approach, a high-poloidal flux FRC target is formed and translated into a cylindrical, high-field compression region. The FRC target is then compressed to multi-keV temperatures and relevant fusion densities. An overview to the approach and historical background will be provided along with key recent technical progress. An overview of FRC macro-stability criteria and limitations and transport scaling will be detailed. In addition, power-plant analyses for a range of magnetically compressed FRC approaches will be summarized, including key scaling relationships and primary cost drivers. |
Monday, November 5, 2018 11:10AM - 11:30AM |
BM9.00006: Staged Z-pinch for Fusion, Experiment and Simulation Hafiz ur Rahman, Emil Ruskov, Paul Ney, David Reisman, Jeff Narkis, Fabio Conti, Julio Valenzuela, Nicholas Aybar, Farhat N Beg, Eric Dutra, Aaron Covington The Staged Z-pinch is a magneto-inertial fusion concept in which a high-Z liner implodes onto a D or DT target. Initial target heating is provided by a shock launched from the interface due to ram & magnetic pressures. The contribution of magnetic pressure has been shown in numerical studies to increase with higher-Z. Axial magnetic flux frozen into plasma does not behave self-similarly and this relaxes the required initial field strength to sufficiently mitigate MRT growth. This is supported by both experimental data on the 1-MA Zebra and MHD simulations of MACH2 and HYDRA, which shows good agreement with experiment in terms of implosion dynamics, convergence, and neutron yield. From simulation, the average stagnation ion density and temperature is 5.0x1020 cm-3 and 6KeV, respectively. We observed consistent neutron yield of ~ 1.0x1010 , convergence ratio of 8-12 and peak implosion velocity exceeds 400 km/s. We expect to achieve comparable target stagnation conditions on LTD-III, a linear transformer driver that stores much less energy than Zebra, but couples comparable energy to the load. We will also present a scaling study of LTD-III for higher current(7-10MA) and discuss a conceptual design of a modular LTD machine. |
Monday, November 5, 2018 11:30AM - 11:50AM |
BM9.00007: Development of multi-beam ion accelerators for plasma heating Thomas Schenkel, Arun Persaud, Peter Anthony Seidl, Qing Ji, Amit Lal, Vinaya Kumar, Di Ni, William L Waldron Reducing the size, power needs and cost of accelerators opens new opportunities in mass spectrometry, ion implantation and ultimately plasma heating for fusion. We have demonstrated a compact multi-beam RF accelerator [1] with ion acceleration in an array of 3x3 beams. Our technology is based on wafer-based components (silicon or circuit boards) where beam transport is in the direction of the surface normal to the wafer. This allows stacking of wafers to increase beam energy while limiting the peak voltage to several kilovolts. The wafer-based implementation allows us to operate multiple ions beams on a single wafer in parallel for much increased current densities per wafer in a multi-beamlet arrangement compared to a single beam with one large aperture. We report on the integration of all accelerator components (matching section, focusing elements and acceleration stages) and will discuss paths for scaling to high beam power for applications in manufacturing, materials analysis and fusion plasma heating. |
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