Abstract
The National Spherical Torus Experiment Upgrade (NSTX-U) will operate at an axial toroidal field of up to 1 T, about twice the field available on NSTX. A 28 GHz electron cylotron resonance heating (ECRH) system is currently being planned for NSTX-U. A 1 MW 28 GHz gyrotron will be employed. Intially the system will use short, 10-50 ms, 1 MW pulses for ECRH-assisted discharge start-up. Later the pulse length will be extended to 1-5 s to study electron Bernstein wave heating (EBWH) during the plasma current flat top. A mirror launcher will be used to couple microwave power to the plasma via O-mode to the slow X-mode to EBW (O-X-B) double mode conversion. This paper presents a pre-conceptual design for the ECRH/EBWH system proposed for NSTX-U and includes ray tracing and Fokker-Planck modeling results for 28 GHz ECRH during plasma start-up and EBW heating and current drive during the plasma current flattop of a NSTX-U advanced H-mode plasma scenario.
Highlights
The National Spherical Torus Experiment (NSTX) [1] is being upgraded to National Spherical Torus Experiment Upgrade (NSTX-U), a device that will have double the toroidal field, plasma current and neutral beam injection (NBI) power, and a pulse length of 5-8 s, five times the pulse length of NSTX [2]
Later the pulse length will be extended to 1-5 s to study electron Bernstein wave heating (EBWH) during the plasma current flat top
This paper presents a pre-conceptual design for the electron cylotron resonance heating (ECRH)/EBWH system proposed for NSTX-U and includes ray tracing and Fokker-Planck modeling results for 28 GHz ECRH during plasma start-up and EBW heating and current drive during the plasma current flattop of a NSTX-U advanced H-mode plasma scenario
Summary
The National Spherical Torus Experiment (NSTX) [1] is being upgraded to NSTX-U, a device that will have double the toroidal field, plasma current and neutral beam injection (NBI) power, and a pulse length of 5-8 s, five times the pulse length of NSTX [2]. Non-inductive plasma start-up will be accomplished through a combination of coaxial helicity injection (CHI) [3], outer poloidal field start-up [4], plasma guns [5], and up to 1 MW of 28 GHz electron cyclotron resonance heating (ECRH). EPJ Web of Conferences results are presented for EBW heating and current drive during the plasma current flat top of an advanced scenario NSTX-U H-mode plasma
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