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This content will become publicly available on April 20, 2019

Title: Dynamic neutral beam current and voltage control to improve beam efficacy in tokamaks

Here, an engineering upgrade to the neutral beam system at the DIII-D tokamak enables time-dependent programming of the beam voltage and current. Initial application of this capability involves pre-programmed beam voltage and current injected into plasmas that are known to be susceptible to instabilities that are driven by energetic (E ≥ 40 keV) beam ions. These instabilities, here all Alfvén eigenmodes (AEs), increase the transport of the beam ions beyond a classical expectation based on particle drifts and collisions. Injecting neutral beam power, P beam ≥ 2MW, at reduced voltage with increased current reduces the drive for Alfvénic instabilities and results in improved ion confinement. In lower-confinement plasmas, this technique is applied to eliminate the presence of AEs across the mid-radius of the plasmas. Simulations of those plasmas indicate that the mode drive is decreased and the radial extent of the remaining modes is reduced compared to a higher beam voltage case. In higher-confinement plasmas, this technique reduces AE activity in the far edge and results in an interesting scenario of beam current drive improving as the beam voltage reduces from 80 kV to 65 kV.
Authors:
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  1. Univ. of Texas, Austin, TX (United States)
  2. Oak Ridge Associated Univ., Oak Ridge, TN (United States)
  3. General Atomics, San Diego, CA (United States)
  4. Massachusetts Inst. of Technology (MIT), Cambridge, MA (United States)
  5. Univ. of California Irvine, Irvine, CA (United States)
  6. Princeton Plasma Physics Lab. (PPPL), Princeton, NJ (United States)
  7. Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)
  8. Univ. of Wisconsin-Madison, Madison, WI (United States)
  9. Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
Publication Date:
Grant/Contract Number:
FC02-04ER54698; AC02-09CH11466; AC52-07NA27344; FG02-08ER54999; FG02-94ER54235; FG03-97ER54415
Type:
Accepted Manuscript
Journal Name:
Physics of Plasmas
Additional Journal Information:
Journal Volume: 25; Journal Issue: 5; Journal ID: ISSN 1070-664X
Publisher:
American Institute of Physics (AIP)
Research Org:
General Atomics, San Diego, CA (United States)
Sponsoring Org:
USDOE Office of Science (SC), Fusion Energy Sciences (FES) (SC-24)
Country of Publication:
United States
Language:
English
Subject:
70 PLASMA PHYSICS AND FUSION TECHNOLOGY
OSTI Identifier:
1435647
Alternate Identifier(s):
OSTI ID: 1434191