Runaway electron deconfinement in SPARC and DIII-D by a passive 3D coil
Journal article, 2022

The operation of a 3D coil-passively driven by the current quench (CQ) loop voltage-for the deconfinement of runaway electrons (REs) is modeled for disruption scenarios in the SPARC and DIII-D tokamaks. Nonlinear magnetohydrodynamic (MHD) modeling is carried out with the NIMROD code including time-dependent magnetic field boundary conditions to simulate the effect of the coil. Further modeling in some cases uses the ASCOT5 code to calculate advection and diffusion coefficients for REs based on the NIMROD-calculated fields, and the DREAM code to compute the runaway evolution in the presence of these transport coefficients. Compared with similar modeling in Tinguely et al (2021 Nucl. Fusion 61 124003), considerably more conservative assumptions are made with the ASCOT5 results, zeroing low levels of transport, particularly in regions in which closed flux surfaces have reformed. Of three coil geometries considered in SPARC, only the n = 1 coil is found to have sufficient resonant components to suppress the runaway current growth. Without the new conservative transport assumptions, full suppression of the RE current is maintained when the thermal quench MHD is included in the simulation or when the RE current is limited to 250kA, but when transport in closed flux regions is fully suppressed, these scenarios allow RE beams on the order of 1-2 MA to appear. Additional modeling is performed to consider the effects of the close ideal wall. In DIII-D, the CQ is modeled for both limited and diverted equilibrium shapes. In the limited shape, the onset of stochasticity is found to be insensitive to the coil current amplitude and governed largely by the evolution of the safety-factor profile. In both devices, prediction of the q-profile evolution is seen to be critical to predicting the later time effects of the coil.

MHD

runaway electrons

disruption

tokamak

Author

V. A. Izzo

Fiat Lux

Istvan Pusztai

Chalmers, Physics, Subatomic, High Energy and Plasma Physics

K. Saerkimaeki

Max Planck Society

Andréas Sundström

Chalmers, Physics, Subatomic, High Energy and Plasma Physics

D. T. Garnier

Massachusetts Institute of Technology (MIT)

D. Weisberg

General Atomics

R. A. Tinguely

Massachusetts Institute of Technology (MIT)

C. Paz-Soldan

Columbia University

R. S. Granetz

Massachusetts Institute of Technology (MIT)

R. Sweeney

Massachusetts Institute of Technology (MIT)

Nuclear Fusion

0029-5515 (ISSN) 1741-4326 (eISSN)

Vol. 62 9 096029

Runaway electrons in fusion plasmas

Swedish Research Council (VR) (2018-03911), 2018-12-01 -- 2021-12-31.

Subject Categories

Other Physics Topics

Fusion, Plasma and Space Physics

Other Electrical Engineering, Electronic Engineering, Information Engineering

DOI

10.1088/1741-4326/ac83d8

More information

Latest update

8/26/2022