Physics Design of a 28 GHz Electron Heating System for the National Spherical Torus Experiment Upgrade
Authors: Gary Taylor, et. al.
Abstract:
A megawatt-level, 28 GHz electron heating system is being designed to support non-inductive
(NI) plasma current (Ip) start-up and local heating and current drive (CD) in H-mode discharges in the
National Spherical Torus Experiment Upgrade (NSTX-U). The development of fully NI Ip start-up and
ramp-up is an important goal of the NSTX-U research program. 28 GHz electron cyclotron (EC) heating is
predicted to rapidly increase the central electron temperature (Te(0)) of low density NI plasmas generated
by Coaxial Helicity Injection (CHI). 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. Also 28 GHz electron
Bernstein wave (EBW) heating and CD can be used during the Ip flat top in NSTX-U discharges when the
plasma is overdense. Ray tracing and Fokker-Planck numerical simulation codes have been used to model
EC and EBW heating and CD in NSTX-U. This paper presents a pre-conceptual design for the
28 GHz heating system and some of the results from the numerical simulations.
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Submitted to: 20th Topical Conference on Radio Frequency Power in Plasmas, Sorrento, Italy, June 25-28, 2013)
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Download PPPL-4928 (pdf 266 KB 4 pp)
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