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Effect of Rotation on L-H Threshold Approved 2008

Effect of Rotation on L-H Threshold Approved 2008. Effect of Rotation on L-H Threshold (NBI-based) Use n=3 braking to change rotation and study effect on L-H threshold power Mimics, to some extent, effect of ripple on threshold High priority ITER topic NHTX-, CTF-relevant

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Effect of Rotation on L-H Threshold Approved 2008

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  1. Effect of Rotation on L-H ThresholdApproved 2008 Effect of Rotation on L-H Threshold (NBI-based) Use n=3 braking to change rotation and study effect on L-H threshold power Mimics, to some extent, effect of ripple on threshold High priority ITER topic NHTX-, CTF-relevant Attempted last year, but found L-H in OH phase (want in auxiliary heated phase to test different beam torques) Establish baseline discharge (double-null) Establish power threshold with no braking (Ip=800 kA, BT=4.5 kG) Vary voltage of source A (add B or C if necessary) Apply n=3 braking (starting at 500 A and increase to level where rotation affected) Establish threshold at new value of rotation Repeat for ~3 levels of rotation Li not necessary, but important to establish reproducible front end

  2. Baseline Discharge (no Li)

  3. Establish Parametric Dependence of PL-H With No Braking • Ip scan • Establish threshold for three values of Ip • 700, 900, 1100 kA at 5.0 kG • BT scan • Establish threshold for three values of BT • 3.5, 4.5, 5.5 kG @ 1.0 MA • Use same baseline as for rotation scan (no applied fields, no OH H-mode) • Li not necessary

  4. Degradation of Confinement with BetaApproved 2008 • Idea is to hold collisionality fixed and perform beta (power) scan to assess degradation of confinement with beta • ITPA joint experiment TC-1 • XP approved and partially run • Little or no degradation observed in strongly shaped plasmas (kappa~2.1, delta~0.65), consistent with DIII-D, JET • This part was completed in plasmas having Type V ELMs • Second part is to redo in weakly shaped plasmas (kappa~1.8, delta~0.45) • Did this as well, but found large variation in ELMs from low to high powers • Observed very strong degradation, but could have been due to different ELMs • Want to redo scan in plasmas with ELMs suppressed by Lithium • Need to establish plasma that will allow > 4 MW power without hitting beta limit (an issue last year) for baseline • Can be conducted early in the run, as long as proper shot is identified • ½ day experiment

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