Darren McDonald, ITPA meeting, 3rd October 2007 1/10

Beta dependence of confinement in JET ELMy H-modes

D C McDonald, C Giroud, L Laborde, M Brix, R Buttery, E de la Luna, A Fonseca, N Hawkes, J Hobirk, D Howell, S Jachmich, E Joffrin, R

Koslowski, H Leggate, I Nunes, C Perez Von Thun, I Voitsekhovitch, and JET EFDA contributors

Structure of talk:

• Introduction and background

• Beta scan results

• Modelling

• Conclusions

Darren McDonald, ITPA meeting, 3rd October 2007 2/10

Previous JET scans

BI

2BT

4Bn

Darren McDonald, ITPA meeting, 3rd October 2007 3/10

Previous scansMachine Experiments scaling

JET 1996 Independent

DIII-D 1996 Independent

DIII-D 2003 Independent

JET 2004 Independent

JT-60U 2005 Degradation

ASDEX-Upgrade 2006 Degradation

Darren McDonald, ITPA meeting, 3rd October 2007 4/10

JET scan: match

Time (s)P

NB

I (M

W)

ne/B2 (1019 m-3 T-2)

<Te>/B2 (keV T-2)

q9

5D

(

ph

sr-1

cm

-2 s

-1)

Darren McDonald, ITPA meeting, 3rd October 2007 5/10

JET scan: profile match68590, N=2.0

68595, N=1.7

68686, N=1.4

Darren McDonald, ITPA meeting, 3rd October 2007 6/10

JET scan: confinement

68590, N=2.0

68595, N=1.7

68686, N=1.4

Darren McDonald, ITPA meeting, 3rd October 2007 7/10

JET scan: core + edge

Darren McDonald, ITPA meeting, 3rd October 2007 8/10

Why different scalings?

s d e l t a d e l t a < 0 . 3 d e l t a > = 0 . 3

H IP

B98(

y,2)

0 . 5

1 . 0

1 . 5

b e t a n t h

0 . 6 0 . 8 1 . 0 1 . 2 1 . 4 1 . 6 1 . 8 2 . 0 2 . 2 2 .

Darren McDonald, ITPA meeting, 3rd October 2007 9/10

JET scan: modellingIn

terp

reta

tive

scan

s ar

ound

#68

595,

=

0.6

Interpretative scans around #68595, eff averaged over

0.3<<0.7

Darren McDonald, ITPA meeting, 3rd October 2007 10/10

Conclusions• A scan on JET has shown decreasing confinement with increasing . It was

performed in a scenario with a hybrid preheat.

Different from previous ELMy H-mode scans

Experiments and wider dataset suggests that decreasing confinement with increasing associated with high triangularity, >0.3, JET plasmas.

No sign that the q-profile differs from normal ELMy H-mode q-profile.

Modelling shows a stabilisation of ETG can quantitatively reproduce the results, but modelling of scans is found to be sensitive to parameter matches.

• Further experiments to clarify effect of plasma shape on transport and confinement at high .