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Title: An upgrade of the magnetic diagnostic system of the DIII-D tokamak for non-axisymmetric measurements

Here, the DIII-D tokamak magnetic diagnostic system has been upgraded to significantly expand the measurement of the plasma response to intrinsic and applied non-axisymmetric “3D” fields. The placement and design of 101 additional sensors allow resolution of toroidal mode numbers 1 ≤ n ≤ 3, and poloidal wavelengths smaller than MARS-F, IPEC, and VMEC magnetohydrodynamic (MHD) model predictions. Small 3D perturbations, relative to the equilibrium field (10–5 <δB/B0 <10–4), require sub-millimeter fabrication and installation tolerances. This high precision is achieved using electrical discharge machined components, and alignment techniques employing rotary laser levels and a coordinate measurement machine. A 16-bit data acquisition system is used in conjunction with analog signal-processing to recover non-axisymmetric perturbations. Co-located radial and poloidal field measurements allow up to 14.2 cm spatial resolution of poloidal structures (plasma poloidal circumference is ~ 500 cm). The function of the new system is verified by comparing the rotating tearing mode structure, measured by 31 BP fluctuation sensors, with that measured by the upgraded BR saddle loop sensors after the mode locks to the vessel wall. The result is a nearly identical 2/1 helical eigenstructure in both cases.
Authors:
 [1] ;  [2] ;  [2] ;  [2] ;  [2] ;  [3] ;  [4] ;  [1] ;  [2] ;  [3] ;  [2] ;  [2] ;  [2] ;  [4] ;  [5] ;  [6] ;  [7]
  1. Oak Ridge Institute for Science and Education, Oak Ridge, TN (United States)
  2. General Atomics, San Diego, CA (United States)
  3. Columbia Univ., New York, NY (United States)
  4. Princeton Plasma Physics Lab. (PPPL), Princeton, NJ (United States)
  5. Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
  6. The Australia National Univ., Canberra, ACT (Australia)
  7. National Fusion Research Center, Daejeon (South Korea)
Publication Date:
Grant/Contract Number:
FC02-04ER54698
Type:
Accepted Manuscript
Journal Name:
Review of Scientific Instruments
Additional Journal Information:
Journal Volume: 85; Journal Issue: 8; Journal ID: ISSN 0034-6748
Publisher:
American Institute of Physics (AIP)
Research Org:
General Atomics, La Jolla, CA (United States)
Sponsoring Org:
USDOE
Country of Publication:
United States
Language:
English
Subject:
46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND TECHNOLOGY; 70 PLASMA PHYSICS AND FUSION TECHNOLOGY
OSTI Identifier:
1351085