first results on active elm control on jet
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TFM
6 Nov 2006H R Koslowski, Workshop on Active Control of MHD Stability, Princeton
ELM mitigation by external coils on JETELM mitigation by external coils on JET
W.FundamenskiW.Fundamenski
On behalf ofOn behalf of
R.Koslowski, Y.Liang, P.Thomas and EFDA-JET contributorsR.Koslowski, Y.Liang, P.Thomas and EFDA-JET contributors
TFM
6 Nov 2006H R Koslowski, Workshop on Active Control of MHD Stability, Princeton
n=1n=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
First results on active ELM control on JET
ICoil ≤ 3 kA x 16 turns
TFM
6 Nov 2006H R Koslowski, Workshop on Active Control of MHD Stability, Princeton
EFCC ELM mitigation experiment
#67954; Ip = 1.6 MA; Bt = 1.84 T; q95 ~ 4.0; ~ 0.3
t=18.0s
t=17.0s
IEFCC
WDia
D
q95
P
H98
N
14 1816 Time (s)
Wdia<10%
fELMs= 28 120 Hz
OH + 16.8 MW NBI
C_SFE_LT
TFM
6 Nov 2006H R Koslowski, Workshop on Active Control of MHD Stability, Princeton
Influence of RMP (n=1) on ne and Te
IEFCC
nel central
nel edge
Te central
Te edge
Teped = 500-700 eV 100-200eV
needge; ne
edge;
>20%
17 17.5 18 18.5Time (s)
Increased by ~17%
decreased by ~15%
TFM
6 Nov 2006H R Koslowski, Workshop on Active Control of MHD Stability, Princeton
Limiter heat loading
Without EFCC
With EFCC
16 17 18 19 20 21
Temperature
outer limiter
Temperature
outer limiter
IEFCC
Time (s)
NBI
EFCC off
EFCC on
(n=1, 90o)
TFM
6 Nov 2006H R Koslowski, Workshop on Active Control of MHD Stability, Princeton
Ergodisation?
Equilibrium: B0=1.84T; q95=3.95; =0.5;
For 1 kA*16 turns
[Calculated By: M. Bécoulet and E. Nardon]
TFM
6 Nov 2006H R Koslowski, Workshop on Active Control of MHD Stability, Princeton
q95 Scan
Neutron rate
IEFCC
D
#68212#68211#67954#67959
17 18Time (s)
17 18Time (s)
17 18Time (s)
17 18Time (s)
Ip=1.4MA
q95=4.8
Bt=1.84 T; Plasma configuration: C_SFE_LT(68207-68212)
Ip=1.6MA
q95=4.0
Ip=1.8MA
q95=3.5
Ip=2.0MA
q95=3.0
TFM
6 Nov 2006H R Koslowski, Workshop on Active Control of MHD Stability, Princeton
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
• D 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
TFM
6 Nov 2006H R Koslowski, Workshop on Active Control of MHD Stability, Princeton
Summary (II)
Only weak degradation (< 10%) of global plasma performance (Wdia, N)
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 the
n = 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
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