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Stability, Transport, and Conrol for the discussion Y. Miura IEA/LT Workshop (W59) combined with DOE/JAERI Technical Planning of Tokamak Experiments (FP1-2) 'Shape and Aspect Ratio Optimization for High Beta Steady-State Tokamak’ Feb at San Diego, GA

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Stability (1) by Ferron, –f bs p q N –fusion gain E N H 89 /q 95 2 (increase q min than q 95 ) –peaked pressure profile reduces achievable N –near ideal N limit tearing mode still have significant effects on confinement –highest N obtained in balanced DN high shape, but soften by Type I ELM squareness reduces ELM size (it reduces pedestal pressure?) by Rimini, –What are the changes when operating at high ? ITBs are not compatible with large ELMs –Gas (light impurity) -> to reduce ELM size

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Stability (2) by Kurita, –critical N values (n=1) for NCT are shown to be increased by increasing S (shape factor through and A) –Max N using sector coil set is estimated by Miura and Matsukawa, –The shape and aspect ratio are important to increase the critical limit for NCT By Menard, –For no wall limit ~3.2 nearly invariant ( extend to low A) /l i is not A invariant High d is required to take full advantage of high k at low A and q*= (1+ 2 ) / 0 I N are good measure for NSTX data –For ideal limit N limit increases from 6 to 9 as A->1 Are high , high and low A always good for high N ? Where is an optimum condition for these parameters?

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Transport by Petty, –Transport dependence on elongation and safety factor are weaker than IPB98(y,2) relation but close to EGB relation –For “optimum tokamak”, fusion gain is optimized between aspect ratio of 2.2 and 3.0 (depending upon which confinement scaling relation is used) –If stability limit and elongation are assumed independent of aspect ratio, then fusion gain optimizes at higher R/a by Field, –B E 0.73 [IPB y2 ] => 0.83 [IPB y2 -PBXM +MAST] –Pedestal scaling => HFS pedestal width scaling by Saibene, –High plasma shaping ( , , QDN) common element to all small ELM experiments in JET –At low p, mixed Type I-II ELMs are observed in SN and QDN – increasing q 95 closes off access to high n ped and no Type II ELMs –High p : “threshold” similar to JT-60U, but different collisionality Can we reduce ELMs at highly shaped plasma?

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Control (1) by Litaudon, –Increasing the H & CD at P~45MW(NB & IC upgrade) Access to bootstrap-dominated regimes at 2.5MA, N >2.5 Explore -scaling ~1/3 of P NB in counter to control V –Upgrade of LHCD launcher Reliable P LHCD ~3MW in H-mode by Miura, Kurita and Matsukawa, –Control of NTM by ECCD in NCT –Further optimization is necessary to improve response time of feedback field to the plasma –Shaping controllability

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Control (2) by Sabbagh, –In NSTX, N ~6.8. The RWM control in NSTX was discussed. by Hubbard, –Current profile control by LH was discussed. –In C-MOD, 3MW LH (4.6GHz) is ready for the experiment. by Moreau, –Real time current profile, shape, profile and flux control were discussed. –It is towards controlled advanced scenarios on JET There are some methods to control plasma in this workshop. High f bs plasma is a self-oganized plasma. We have to find the way to control a burning plasma with high f bs.

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