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First results on active ELM control on JET

ELM mitigation by external coils on JET W.Fundamenski On behalf of R.Koslowski, Y.Liang, P.Thomas and EFDA-JET contributors. First results on active ELM control on JET. n=1. n=2. Aim: Control type-I ELMs Tool: Error Field Correction Coils (EFCC), proposed by Y Liang n =1

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First results on active ELM control on JET

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  1. ELM mitigation by external coils on JETW.FundamenskiOn behalf ofR.Koslowski, Y.Liang, P.Thomas and EFDA-JET contributors H R Koslowski, Workshop on Active Control of MHD Stability, Princeton

  2. First results on active ELM control on JET n=1 n=2 • Aim: Control type-I ELMs • Tool: Error Field Correction Coils (EFCC), proposed by Y Liang • n=1 • Weak edgeergodisation • Plasma braking • Seeding oflocked modes • n=2 • Good edge ergodisation • Small influence on core plasma ICoil ≤ 3 kA x 16 turns H R Koslowski, Workshop on Active Control of MHD Stability, Princeton

  3. EFCC ELM mitigation experiment t=17.0s q95 t=18.0s IEFCC WDia DWdia<10% P OH + 16.8 MW NBI H98 bN Da fELMs= 28  120 Hz 14 16 Time (s) 18 #67954; Ip = 1.6 MA; Bt = 1.84 T; q95 ~ 4.0; d ~ 0.3 C_SFE_LT H R Koslowski, Workshop on Active Control of MHD Stability, Princeton

  4. Influence of RMP (n=1) on ne and Te IEFCC nel central >20% Increased by ~17% needge; Dneedge; nel edge Te central DTeped = 500-700 eV 100-200eV Te edge decreased by ~15% 17.5 18 18.5 17 Time (s) H R Koslowski, Workshop on Active Control of MHD Stability, Princeton

  5. Limiter heat loading NBI IEFCC Temperature outer limiter Temperature outer limiter 21 16 18 19 20 17 Time (s) EFCC off Without EFCC EFCC on (n=1, 90o) With EFCC H R Koslowski, Workshop on Active Control of MHD Stability, Princeton

  6. Ergodisation? Equilibrium: B0=1.84T; q95=3.95; d=0.5; For 1 kA*16 turns [Calculated By: M. Bécoulet and E. Nardon] H R Koslowski, Workshop on Active Control of MHD Stability, Princeton

  7. q95 Scan #67959 #68212 #68211 #67954 IEFCC Da Neutron rate 17 18 17 18 17 18 17 18 Time (s) Time (s) Time (s) Time (s) Bt=1.84 T; Plasma configuration: C_SFE_LT(68207-68212) Ip=2.0MA q95=3.0 Ip=1.4MA q95=4.8 Ip=1.6MA q95=4.0 Ip=1.8MA q95=3.5 H R Koslowski, Workshop on Active Control of MHD Stability, Princeton

  8. Summary (I) • First experimental results from JET show that type-I ELMs can be mitigated by the application of an n = 1 external perturbation field • Static n = 1 perturbation induced by the EFCCs • ELM frequency increased from ~30 Hz to ~120 Hz • Da intensity dropped by a factor of ~10 • The drop in edge temperature during the ELM was reduced from 500 – 700 eV to 100 – 200 eV • The electron density in the centre and at the edge was reduced up to ~15% • The central electron temperature increased by ~15%, while the change of the edge temperature is less than a few percent H R Koslowski, Workshop on Active Control of MHD Stability, Princeton

  9. Summary (II) • Only weak degradation (< 10%) of global plasma performance (Wdia, bN) is observed during the ELM mitigation phase • ELM mitigation does not depend on the phase of n = 1 external field, however, there are good phases and bad phases with respect to the position and boundary control on JET • The temperature of the outer limiter dropped during the EFCC phase • Breaking of the central rotation has been observed when the EFCCs were applied • The sawtooth frequency during the EFCC phase increases • There is a wide range in q95 (4.8 – 3.0) in which ELM mitigation with then = 1 external perturbation field has been observed • The effect on ELMs (lower bound) and the excitation of a locked mode (upper bound) form an operational window for EFCC usage for ELM mitigation H R Koslowski, Workshop on Active Control of MHD Stability, Princeton

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