ITER ICRF Scenario Demonstration in Hydrogen with 3He Minority Heating P U Lamalle, J A Snipes ITER Organization Acknowledgments: JET Task Force H

ITER main IC H&CD scenarios ITER IC system: arrays of 6 (pol) x 4 (tor) short straps, controlled toroidal phasing, frequency range 40 to 55MHz (compromise between performance and flexibility) Must use the most robust possible operating scenarios Key role of 3He at nominal BT=5.3T in H, 4He, D and D-T plasmas: minority heating scenario at 53MHz, concentration ~1% up to 4% . (In D-T, to be combined with w=2wcT to maximize ion heating.) Low activation phase of operations: H and 4He plasmas Reduced field (2.65T) operation is also important for the early phases of the ITER program: - in He (and D) plasmas: plan using H minority heating, e.g. 4He(H) at 40MHz - in H plasmas, at present no clear ‘battlehorse’ scenario [discuss] / Could the present proposal cover ‘DT-mimic’ w=2wc3He at high 3He concentration? 2

The (3He)H scenario Explored on JET at magnetic fields ~3.6T at PIC up to 5MW: minority heating to mode conversion regimes (Lamalle et al. NF 46 391-400; Mayoral et al. NF 46 S550-63, more experiments planned in 2009) Deserves specific investigation as non-standard minority heating scheme with (Z/A)min < (Z/A)maj Demonstration on C-MOD at ITER-like field (5.3T) and plasma shape would confirm viability of this scenario for ITER. This is very important for the ITER Research Plan Goals: 1) Explore range of 3He concentrations covering minority heating and transition to mode conversion. 2) Develop strategy for concentration control (possibilities of feedback?) 3) Determine concentration maximizing bulk ion heating 4) Optimize IC performance 5) H-Mode access? Development of the scenario is also preparation for companion proposal.

ITER ICRF Scenario Demonstration: H (3He) Motivation: To demonstrate that this scenario can be relied upon for the low activation phase of ITER operations. (Also preparation for companion proposal) Goal: Develop and optimize this scenario on ITER-like hydrogen plasma / 5.3T, q.95~3 (Ip~1.2MA). Plan of execution:  Using H(3He) plasmas (high density to optimize IC coupling) and ICRF at f=fc3He53MHz, scan 3He concentration from 0 to ~4%. Monitor 3He tail and Ti, Te profiles. Assess power deposition profiles with IC power modulation. Determine best concentration for bulk ion heating. Conclude by performing reference shots at maximum performance.  Requires 2-3 days of operation. The H plasmas could be planned during the last week before next machine opening to avoid difficulties returning to D(H) ICRF operation.  Pending discussion, could briefly assess f=2fc3He 53MHz at BT=2.65T (or f80MHz at BT=4T), at high 3He concentrations.