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Spectroscopic measurements of temperature and plasma impurity concentration during magnetic reconnection at the Swarthmore Spheromak Experiment

Chaplin, V. H. and Brown, M. R. and Cohen, D. H. and Gray, T. (2009) Spectroscopic measurements of temperature and plasma impurity concentration during magnetic reconnection at the Swarthmore Spheromak Experiment. Physics of Plasmas, 16 (4). 042505. ISSN 1070-664X.

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Electron temperature measurements during counterhelicity spheromak merging studies at the Swarthmore Spheromak Experiment (SSX) [M. R. Brown, Phys. Plasmas 6, 1717 (1999)] are presented. VUV monochromator measurements of impurity emission lines are compared with model spectra produced by the non-LTE excitation kinematics code PRISMSPECT [J. J. MacFarlane et al., in Proceedings of the Third Conference on Inertial Fusion Science and Applications (2004)] to yield the electron temperature in the plasma with 1 µs time resolution. Average T_e is seen to increase from 12 to 19 eV during spheromak merging. Average C III ion temperature, measured with a new ion Doppler spectrometer (IDS) [C. D. Cothran et al., Rev. Sci. Instrum. 77, 063504 (2006)], likewise rises during spheromak merging, peaking at ~22 eV, but a similar increase in T_i is seen during single spheromak discharges with no merging. The VUV emission line measurements are also used to constrain the concentrations of various impurities in the SSX plasma, which are dominated by carbon, but include some oxygen and nitrogen. A burst of soft x-ray emission is seen during reconnection with a new four-channel detector (SXR). There is evidence for spectral changes in the soft x-ray emission as reconnection progresses, although our single-temperature equilibrium spectral models are not able to provide adequate fits to all the SXR data.

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Additional Information:© 2009 American Institute of Physics. Received 4 November 2008; accepted 25 February 2009; published 7 April 2009. The authors gratefully acknowledge the technical assistance of S. Palmer and J. Haldeman at Swarthmore, and J. MacFarlane at Prism Computational Sciences, as well as some preliminary modeling done by V. Swisher at Swarthmore. This work was supported by the DOE under Grant No. ER54604, by the NSF Center for Magnetic Self- Organization (Award No. PHY-0821899), and by a Eugene M. Lang summer research fellowship from the Provost’s Office at Swarthmore College.
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Department of EnergyER54604
Swarthmore CollegeUNSPECIFIED
Issue or Number:4
Record Number:CaltechAUTHORS:20090721-121856034
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Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:14630
Deposited By: Jason Perez
Deposited On:08 Aug 2009 20:10
Last Modified:03 Oct 2019 00:51

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