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Summary of XP-710

Summary of XP-710. D. A. Gates NSTX Results review 7/24/07. Status of NHTX-like discharge development. Strong shaping achieved Achieved non-inductive fraction of 55% nearly equivalent to that in 116318 (NSTX record pulse length) H-mode achieved during current ramp at 5.5kGauss

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Summary of XP-710

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  1. Summary of XP-710 D. A. Gates NSTX Results review 7/24/07

  2. Status of NHTX-like discharge development • Strong shaping achieved • Achieved non-inductive fraction of 55% nearly equivalent to that in 116318 (NSTX record pulse length) • H-mode achieved during current ramp at 5.5kGauss • Lower N limits non-inductive fraction

  3. Last years equilibrium • Equilibrium parameters: • Target Achieved •  2.7 2.65 • A 1.75 1.6 • li 0.4 0.45 • N >5.5 ~4

  4. Plasma nearly matches 116318 Red 116318, Black 124058

  5. Beam absorption is poor at low current and low li • For 5.4MW applied only 3.2MW of heating • Plasma repeatedly hits beta limit

  6. High non-inductive fraction achieved Shot 124058, TRANSP A02 • Achieved 55% non-inductive current fraction (TRANSP) • Ramped linearly up to the end of the shot • Based on EFIT02 (no MSE) - MSE based reconstructions • Reconstructions with MSE had proved problematic (current hole), but are available

  7. Plasma limited by low frequency MHD mode • Large n=1 mode detected on external locked mode detector • No USXR to confirm mode structure • Thomson shows global plasma deformation • RWM

  8. Use long pulse shot from 2008 as new starting point • Very similar to previous longest shot on NSTX • Feedback on, kappa and current both higher, li lower

  9. Run plan • Goal: Improve the operating limits for this scenario • focus on varying Bt and Ip but also investigate the effect of lithium and error field suppression • 1. Use Liter at 40mg/min, (use no glow scenario if this is effective). Start with shot 129121 (long pulse post-lithium from Jon’s error field XP-). (1 shot) • 2. Increase plasma elongation in increments of 0.1 (3 -5 shots) • 3. Using elongation with optimum non-inductive current, increase toroidal field in 0.25kGauss increments up to 5.5 kGauss. Adjust pulse to avoid trips. (12 shots) • 4. Do current scan at select toroidal fields. Use optimum toroidal field, .25kGauss higher and .25 kGauss lower. Current scan from 700-900kA in 50kA steps. (12 shots) • 5. Repeat 3 and 4 with lithium recently applied, but with evaporator off. (20 shots)

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