Bulletin of the American Physical Society
63rd Annual Meeting of the APS Division of Plasma Physics
Volume 66, Number 13
Monday–Friday, November 8–12, 2021; Pittsburgh, PA
Session TI01: Awards (Weimer, Stix, and Rosenbluth) and Magnetized High-Energy-Density PhysicsInvited Live Prize/Award
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Chair: Ted Perry, Los Alamos National Laboratory Room: Ballroom B |
Thursday, November 11, 2021 9:30AM - 10:00AM |
TI01.00001: Katherine E. Weimer Award: Quantitative Modeling of Radiation Belt Dynamics: Recent Advances and Remaining Challenges Invited Speaker: Weichao Tu In 1958 Dr. Van Allen and colleagues discovered a "belt" of energetic particles in space that are trapped by the Earth's magnetic fields – what we now know as the Van Allen Radiation Belts. The Earth's radiation belts are characterized by large variations in electron fluxes, which are controlled by the competition between source, transport, and loss processes. Understanding, quantitatively modeling, and eventually predicting the dynamics of energetic electrons in the radiation belts have been the research targets that space physicists have long pursued. Recently, great advances have been made in the quantitative modeling of radiation belt dynamics, including both the fast development of modeling techniques and the significant improvement in model inputs. The better model inputs are only made possible by the extensive wave and particle measurements from multiple space and ground missions, especially the NASA Van Allen Probes Mission. In this talk I will briefly introduce the dynamics of radiation belt electrons, review some of our recent advances in quantitative modeling of radiation belt dynamics, and finish with discussing the remaining challenges and opportunities in radiation belt modeling. |
Thursday, November 11, 2021 10:00AM - 10:30AM |
TI01.00002: Thomas H. Stix Award for Outstanding Early Career Contributions to Plasma Physics Research: Pathways to Transient Control in Tokamak Plasmas Invited Speaker: Carlos A Paz-Soldan Though the tokamak concept for magnetic fusion energy production is technically rather mature, challenges remain in the control of transient events associated with high-performance operation. This presentation will highlight ongoing work at the DIII-D tokamak facility to advance alternate pathways to avoid or mitigate edge-localized mode (ELM) instabilities occurring during the stationary phase, as well as relativistic electron (RE) populations excited during fast shut-downs. For ELMs, the relatively unexplored pathway of negative triangularity shaping offers the promise of integrating a high-pressure core plasma with an ELM-stable edge. Appropriate shaping is found to inhibit the steep edge gradients that destabilize ELMs. Examination of DIII-D plasma performance without ELMs highlights the integration potential of this edge solution via its unique access to high power and high density, while also clarifying pathways to improve absolute fusion performance. For the REs, emerging work highlights the beneficial effects of large-scale non-axisymmetric fields – intrinsic or extrinsic – for control. Destabilization of intrinsic plasma instabilities yield prompt dispersal of the entire RE population over an area that is larger than otherwise found, and experimental recipes to access the instability are under development. While intrinsic properties require no special equipment, their robustness is yet to be proven – thus motivating the use of extrinsic fields delivered via purpose-built conducting structures to more reliably achieve the same effect. For both challenges, the DIII-D tokamak acts as a proof-of-principle test-bed for these alternate transient control approaches. Planned and potential upgrades to the facility promise to enable unique validation of the underlying control concepts and pave the way to more robust tokamak designs with reduced physics risk towards high fusion power operation. |
Thursday, November 11, 2021 10:30AM - 11:00AM |
TI01.00003: Marshall N. Rosenbluth Outstanding Doctoral Thesis Award: Adjoint methods for stellarator shape optimization and sensitivity analysis Invited Speaker: Elizabeth J Paul Modern stellarator design requires numerical optimization to navigate the high-dimensional spaces used to describe their geometry. Physical insight into the self-adjointness properties of the underlying equations enables advanced optimization methods through the efficient calculation of sensitivity information. The first applications of the adjoint method to stellarator design are reviewed. An adjoint drift-kinetic equation is derived based on the self-adjointness property of the Fokker-Planck collision operator [1]. This adjoint method allows one to understand the sensitivity of neoclassical quantities, such as the radial collisional transport and bootstrap current, to perturbations of the magnetic field strength. The well-known self-adjointness property of the MHD force operator is generalized to include perturbations of the rotational transform and the currents outside the confinement region [2-3]. This adjoint method enables evaluation of the sensitivity of equilibrium properties to perturbations of coil shapes or the plasma boundary. Adjoint methods have also been developed to reduce stellarator coil complexity [4], eliminate magnetic islands [5], and obtain quasisymmetric vacuum fields. Applications of these adjoint methods for sensitivity analysis and optimization are reviewed [6]. |
Thursday, November 11, 2021 11:00AM - 11:30AM |
TI01.00004: Effects of Kilotesla-Level Applied Magnetic Fields on Relativistic Laser-Plasma Interaction Invited Speaker: Kathleen Weichman Ongoing advances in experimental techniques for generating magnetic fields will enable access to previously unexplored regimes in magnetized high-energy-density physics. Strong static magnetic fields, for instance, fundamentally alter the interaction of a relativistically intense laser with a plasma. In this talk, I will present particle-in-cell simulations of a number of common laser-plasma configurations in which diverse and potentially beneficial changes to the plasma dynamics become evident at or below the kilotesla level. In this near-term experimentally realizable regime, the magnetic field acts primarily through the magnetization of hot electrons, which impacts processes such as ion acceleration, direct laser acceleration, and magnetic-field amplification. These findings suggest that applied magnetic fields could improve applications of relativistic laser–plasma interactions, delivering, for example, focusing, high-energy ion beams for isochoric heating, dramatic electron heating for x-ray generation, and astrophysically relevant, megatesla-level magnetic fields. |
Thursday, November 11, 2021 11:30AM - 12:00PM |
TI01.00005: Magnetic field measurements of laboratory-scale, detached, magnetized bow shocks Invited Speaker: Joseph M Levesque Results are presented from the first experiments to successfully measure the magnetic field of laboratory-scale magnetized bow shocks, performed at the OMEGA laser facility. Magnetized bow shocks occur when the magnetic pressure of an obstacle equals the ram pressure of an incoming supersonic plasma flow. These shocks are common in astrophysical systems, notably in the interaction of the Earth’s magnetic field with the solar wind, where the magnetosphere prevents harmful radiation from reaching the surface. In these experiments the magnetic field is generated by a thin, current-carrying wire, and the incoming plasma is produced by the collision and expansion of two counter-propagating laser-generated plasma plumes. |
Thursday, November 11, 2021 12:00PM - 12:30PM |
TI01.00006: Investigating magnetised, radiatively driven plasmas with a university scale pulsed-power generator Invited Speaker: Jack W Halliday We present first results from a novel experimental platform which is able to access physics relevant to topics including indirect-drive ICF, MAGLIF, and laboratory astrophysics (for example the penetration of B-fields into HED plasmas). |
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