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XP810 review Error field sensitivity of 2/1 NTM onset thresholds at high and low rotation

XP810 review Error field sensitivity of 2/1 NTM onset thresholds at high and low rotation (and later extension to counter rotation) R J Buttery 1 with R. J. La Haye 2 , S. Sabbagh 3 , E. J. Strait 2. 1 EURATOM/UKAEA Fusion Association, Culham Science Centre, UK.

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XP810 review Error field sensitivity of 2/1 NTM onset thresholds at high and low rotation

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  1. XP810 review Error field sensitivity of 2/1 NTM onset thresholds at high and low rotation (and later extension to counter rotation) R J Buttery1 with R. J. La Haye2, S. Sabbagh3, E. J. Strait2. 1EURATOM/UKAEA Fusion Association, Culham Science Centre, UK. 2General Atomics, USA 3Columbia University, NY Work conducted under the European Fusion Development Agreement and jointly funded by EURATOM, the UK EPSRC, and US DOE.

  2. 2/1 NTM co vs counter rotation dependence DIII-D bN (2/1 NTM onset) sawtoothing ELMy H modes counter co DIII-D: shows strong rotation dependence in 2/1 NTM bN limit • But what is physics? • Does counter rotation stabilise mode? • Is threshold dependent on rotation shear relative to magnetic shear (á la theory) • Need to test and explore this important result…

  3. 2/1 NTM co vs counter rotation dependence DIII-D, NSTX n=3 braking study Similar % fall in bN per % Mach bN (2/1 NTM onset) counter-co DIII-D: shows strong rotation dependence in 2/1 NTM bN limit • But what is physics? • Does counter rotation stabilise mode? • Is threshold dependent on rotation shear relative to magnetic shear (á la theory) • Need to test and explore this important result… • NSTX can shed more light on this story… ? EFs?

  4. Key issues NSXT can shed light on • NSTX can probe error field effects • To see if increased sensitivity at low rotation • NSTX can explore rotation profile effects • Distinguish between rotation and rotation shear models? • Assisted by varying mix of n=1 & n=3 braking • NSTX can readily address the counter rotation question • Does trend go up or down in counter direction? • Just reverse Bt and Ip… (later, but covered by this XP) Part A Part B Stefan Gerhardt analysis… : bN vs rotation bP vs rotation shear bP vs rotation bN vs rotation shear

  5. Part A:

  6. Part B (later): counter Bt and Ip scans DIII-D, NSTX n=3 braking study Similar % fall in bN per % Mach bN (2/1 NTM onset) counter-co Recall previous NSTX and DIII-D scans: • Simple technique is to reverse Ip and Bt to get strong counter data • Key test of underlying theory governing rotation dependence ? NSTX: about 0.5 shifts, counter BT and IP Apply ramps in b to trigger 2/1 NTM (ref shot 123876) May need co- comparison, and vary rotation with n=3…

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