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Title: Swarthmore Spheromak Experiment


This is the final report for SSX.

 [1];  [1]
  1. Swarthmore College
Publication Date:
Research Org.:
Swarthmore College
Sponsoring Org.:
OSTI Identifier:
Report Number(s):
S00000760, S00000378
DOE Contract Number:
Resource Type:
Technical Report
Resource Relation:
Related Information: M. R. Brown, "Experimental Studies of Magnetic Reconnection", Phys. Plasmas 6, 1717 (1999).
Country of Publication:
United States

Citation Formats

Brown, Michael, and Brown, Michael. Swarthmore Spheromak Experiment. United States: N. p., 2018. Web. doi:10.2172/1423311.
Brown, Michael, & Brown, Michael. Swarthmore Spheromak Experiment. United States. doi:10.2172/1423311.
Brown, Michael, and Brown, Michael. 2018. "Swarthmore Spheromak Experiment". United States. doi:10.2172/1423311.
title = {Swarthmore Spheromak Experiment},
author = {Brown, Michael and Brown, Michael},
abstractNote = {This is the final report for SSX.},
doi = {10.2172/1423311},
journal = {},
number = ,
volume = ,
place = {United States},
year = 2018,
month = 3

Technical Report:

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  • The general goal of the Magnetofluids Laboratory at Swarthmore College is to understand how magnetofluid kinetic energy can be converted to magnetic energy as it is in the core of the earth and sun (the dynamo problem) and to understand how magnetic energy can be rapidly converted back to kinetic energy and heat as it is in solar flares (the magnetic reconnection problem). Magnetic reconnection has been studied using the Swarthmore Spheromak Experiment (SSX) which was designed and built under this Junior Faculty Grant. In SSX we generate and merge two rings of magnetized plasma called spheromaks and study theirmore » interaction. The spheromaks have many properties similar to solar flares so this work is directly relevant to basic solar physics. In addition, since the spheromak is a magnetic confinement fusion configuration, issues of formation and stability have direct impact on the fusion program.« less
  • Recent counter-helicity spheromak merging experiments in the Swarthmore Spheromak Experiment (SSX) have produced a novel compact torus (CT) with unusual features. These include a persistent antisymmetric toroidal magnetic field profile and a slow, nonlinear emergence of the n = 1 tilt mode. Experimental measurements are inconclusive as to whether this unique CT is a fully merged field-reversed configuration (FRC) with strong toroidal field or a partially merged ''doublet CT'' configuration with both spheromak- and FRC-like characteristics. In this paper, the SSX merging process is studied in detail using three-dimensional resistive MHD simulations from the Hybrid Magnetohydrodynamics (HYM) code. These simulationsmore » show that merging plasmas in the SSX parameter regime only partially reconnect, leaving behind a doublet CT rather than an FRC. Through direct comparisons, we show that the magnetic structure in the simulations is highly consistent with the SSX experimental observations. We also find that the n = 1 tilt mode begins as a fast growing linear mode that evolves into a slower-growing nonlinear mode before being detected experimentally. A simulation parameter scan over resistivity, viscosity, and line-tying shows that these parameters can strongly affect the behavior of both the merging process and the tilt mode. In fact, merging in certain parameter regimes is found to produce a toroidal-field-free FRC rather than a doublet CT.« less
  • Several new experimental results are reported from spheromak merging studies at the Swarthmore Spheromak Experiment [M. R. Brown, Phys. Plasmas 6, 1717 (1999)] with relevance to three-dimensional (3D) reconnection in laboratory and space plasmas. First, recent velocity measurements of impurity ions using ion Doppler spectroscopy are reported. Bidirectional outflow at nearly the Alfven speed is clearly observed. Second, experimental measurements of the out-of-plane magnetic field in a reconnection volume showing a quadrupolar structure at the ion inertial scale are discussed. Third, a measurement of in-plane Hall electric field and nonideal terms of the generalized Ohm's law in a reconnection volumemore » of a weakly collisional laboratory plasma is presented. Time resolved vector magnetic field measurements on a 3D lattice [B(r,t)] enables evaluation of the various terms. Results show that the Hall electric field dominates everywhere (JxB/ne) and also exhibits a quadrupolar structure at the ion inertial scale; resistive and electron inertia terms are small. Each of these is related to and compared with similar measurements in a solar or space context.« less