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ITER STEADY-STATE OPERATIONAL SCENARIOS

ITER STEADY-STATE OPERATIONAL SCENARIOS. A.R. Polevoi for ITER IT and HT contributors. ITER-SS 1. OUTLINE:. (1) Definitions (2) Basis for choice of operational parameters (3) Transport simulations for ITER (4) Types of SS scenarios proposed for ITER SS Type-I: NB + LH CD

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ITER STEADY-STATE OPERATIONAL SCENARIOS

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  1. ITER STEADY-STATE OPERATIONAL SCENARIOS A.R. Polevoi for ITER IT and HT contributors ITER-SS 1

  2. OUTLINE: (1) Definitions (2) Basis for choice of operational parameters (3) Transport simulations for ITER (4) Types of SS scenarios proposed for ITER SS Type-I: NB + LH CD SS Type-II: NB + EC CD (5) Discussion on physics needs Projection of experimental scenarios toITER Experimental demonstration of feasibility

  3. DEFINITIONS Steady State scenario = scenario with full noninductive current drive ITER Hybrid reference scenario = scenario with partial noninductivecurrent drive with Q > 5 and duration of the current flat top t > 1000 s ITER Steady State reference scenario = scenario with full noninductivecurrent drive with Q > 5 and duration of the current flat top t > 3000 s

  4. BASIS FOR CHOICE OF OPERATIONAL PARAMETERS (2.1) CD systems for ITER are defined PCD,ITER : NB 33 MW 2 NBIs with 1 MeV D EC 20 MW 170 GHz LH 40 MW (20 + 20) 5 GHz (2.2) For ITER divertor configuration and pumping system power flux to SOL should be limited Psep < Pmax,ITER ( ~ 100 MW) (for more accurate parametric dependence see ITER PDD)

  5. BASIS FOR CHOICE OF OPERATIONAL PARAMETERS (2.3) Plasma contamination by He can be relatively small */e < 2 [1] for ITER reference inductive scenario (2.4) Codes for CD simulation are benchmarked vs some experiments and can be used for CD predictions (2.5) Transport model for SS and hybrid operation in present day experiments is not identified yet • [1] Kukushkin et al NF 43 (2003) 716

  6. TRANSPORT SIMULATIONS FOR ITER • (3.1) To find therequirements for transportHHy,2 = ? which provide • SS operation100% Noninductive CD with theITER CD toolsand • Pfus/PCD = Q > 5; PCD < PCD,ITER • (3.2) To study whether such operation can be stable against NTMs, ballooning, MHD modes, RWMs: • N < ITER-wall • (3.3) To use He pumping and recycling consistent with SOL/divertor simulations with B2/Eirene • (3.4) To study whether such operation is compatible with ITER divertor loads: • Psep < Pmax,ITER ~ 100 MW • (3.5) Taking account of density limit

  7. SS TYPE-I GOAL: qmin > 2 RS to avoid NTMs TOOLS: NB CD + edge LH CD ~50% Ibs / ~ 50% ICD (+): Moderate requirements for confinement HHy,2 = 1.3-1.4 (-): Low li3 ~ 0.6 => Nclose to ITER-wall => narrow operational space with pressure peaking p(0)/<p> SS TYPE-II GOAL: qmin > 1 WS to avoid ST high li3 to increase stability TOOLS: NB CD + EC CD ~50% Ibs / ~ 50% ICD (+): High li3 ~ 0.9 => stable n = 1 (-): Higher HHy,2 = 1.5-1.6 is required -NTM stability ? -n = 2, 3 stability ? TYPES OF SS SCENARIOS PROPOSED FOR ITER

  8. SS TYPE-I: qmin > 2 RS , NB+LH CDSuggested transport: Ion neoclassical at the edge pedestal and RS areas, D = e = i

  9. FIG.4 Stabilising wall position aw/a vs.  for q=const scan of SS operational points 4.1.1, 2, 3 from Table I at a = 1.85 m. No-wall ideal MHD stability limits are shown by vertical dashed lines. aw,ITER/a  1.375. Lines 1,2,3 correspond to 4.1.1, 4.1.2, 4.1. 3 from the Table I with different pressure peakednss: p(0)/<p> = 2.7, 2.9,3.1 FEASIBILITY OF TYPE-I SCENARIO(-) low inductance li3 ~ 0.6 => low no wall limit N < 2.5 STABLE OPERATIONAL SPACE SHRINKS WITH PRESSURE PEAKING

  10. SS TYPE-II: qmin > 1 WS , NB+ECCDSuggested transport: D = e = 0.5 i ~1+ 3x2 and ion neoclassical at the edge pedestal D = e = i = i,neo

  11. (1) N IN ALL SCENARIOS IDEAL n=1 KINKS ARE STABLE • (2) SCENARIOS CAN REQUIRE CONSIDERATION OF THE NTM STABILIZATION • TABLE II: ITER PLASMA PARAMETERS FOR THE SS Type-II SCENARIOS

  12. DISCUSSION ON PHYSICS NEEDS • Projection of experimental scenarios to ITER • (5.1) Pressure and q profiles, N are similar to those required for ITER SS operation. • Thus, at least the ideal stability features and active RWM control do not require extrapolation • (5.2) In ITER heating of electrons dominates • Pe > Pi , Ti/Te ~ 1 is expected • In experiments with N and HH similar to ITER • Pe < Pi, Ti/Te > 1. • Thus, projection to ITER with Ti/Te ~ 1(rather than with Ti/Te > 1)with the same N and HH is required to avoid overestimation of Pfus ~ Ti2 (and Q) and underestimation of ICD~ Te

  13. DISCUSSION ON PHYSICS NEEDS Constraints from SOL/DIV simulations (B2/EIRENE) For ITER divertor configuration and pumping system power flux to SOL should be compatible with divertor constraints (Pmax,ITER ~ 100 MW ) (for more accurate parametric dependence see ref. [1,2] ) Plasma contamination by He can be relatively small */e < 2 [1] Core fuelling saturates with increase of the separatrix density. Thus, ITER operation requires dominant core fuelling [1]. Pellet injection is suggested as a major source of the core fuelling. Thus, the experimental scenario can be considered as ITER relevant if results of projection to ITER fulfil: (5.3) Psep < Pmax,ITER (5.4) with moderate contamination by He. (5.5) scenario should be compatible with pellet fuelling [1] Kukushkin et al NF 43 (2003) 716 [2] ITER PDD

  14. DISCUSSION ON PHYSICS NEEDS • Experimental demonstration of ITER SS feasibility • For experimental support of the ITER SS scenarios feasibility the following directions are suggested: • I. Data supply for validation of transport which fulfil the SS requirements • II. Data supply for validation of predictive capabilities of CD codes • III. Demonstration of active control of instabilities • IV. Demonstration of compatibility with pellet fuelling • V. ITER relevant discharges should be selected taking account of limitations and rules (5.1 - 5.5) discussed in a previous section

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