Plasma startup in the National Spherical Torus Experiment using transient coaxial helicity injection
- University of Washington, Seattle, Washington 98195 (United States)
- Princeton Plasma Physics Laboratory, Princeton, New Jersey 08543 (United States)
- Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831 (United States)
- Nova Photonics, Princeton, New Jersey 08543 (United States)
A method of plasma current generation known as coaxial helicity injection (CHI) has been successfully applied in the National Spherical Torus Experiment [M. Ono, S. M. Kaye, Y.-K. M. Peng et al., Nucl. Fusion 40, 3Y 557 (2000)] to form closed, nested magnetic surfaces carrying a plasma current up to 160 kA. In some discharges the generated current persists for surprisingly long, {approx}400 ms. While the CHI method has previously been studied in smaller experiments, such as the Helicity Injected Tokamak (HIT-II) [R. Raman, T. R. Jarboe, B. A. Nelson et al., Phys Rev. Lett. 90, 075005 (2003)] at the University of Washington, the significance of these results are (a) demonstration of the process in a vessel volume thirty times larger than HIT-II on a size scale more comparable to a reactor (b) a remarkable multiplication factor of 60 between the injected current and the achieved toroidal current, compared to six in previous experiments, and (c) for the first time, fast time scale visible imaging of the entire process that shows discharge formation, disconnection from the injector, and luminous structures consistent with the reconnection of magnetic field lines and closed flux surfaces. These significant results indicate favorable scaling with machine size.
- OSTI ID:
- 20975045
- Journal Information:
- Physics of Plasmas, Vol. 14, Issue 5; Other Information: DOI: 10.1063/1.2515159; (c) 2007 American Institute of Physics; Country of input: International Atomic Energy Agency (IAEA); ISSN 1070-664X
- Country of Publication:
- United States
- Language:
- English
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