Physics design of a 28 GHz Electron Heating System for the National Spherical Torus Experiment Upgrade
Authors: G. Taylor, N. Bertelli, R.A. Ellis, S.P. Gerhardt, R.W. Harvey, J.C. Hosea, F. Poli, R. Raman, andA.P. Smirnov
Abstract: The National Spherical Torus Experiment Upgrade (NSTX-U) will operate at axial toroidal fields
of < 1 T and plasma currents, Ip < 2 MA. The development of non-inductive (NI) plasmas is a major long-term
research goal for NSTX-U. Time dependent numerical simulations of 28 GHz electron cyclotron (EC) heating
of low density NI start-up plasmas generated by Coaxial Helicity Injection (CHI) in NSTX-U predict a
significant and rapid increase of the central electron temperature (Te(0)) before the plasma becomes overdense.
The increased Te(0) will significantly reduce the Ip decay rate of CHI plasmas, allowing the coupling of fast
wave heating and neutral beam injection. A megawatt-level, 28 GHz electron heating system is planned for
heating NI start-up plasmas in NSTX-U. In addition to EC heating of CHI start-up discharges, this system will
be used for electron Bernstein wave (EBW) plasma start-up, and eventually for EBW heating and current drive
during the Ip flattop.
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Published in: Proceedings on the 18th Joint Workshop on Electron Cyclotron Emission and Electron Cyclotron Resonance Heating (April 2014)
AIP Conf. Proc. 1580 , 534 (2014) ; http://dx.doi.org/10.1063/1.4864606
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