Overview of 2006 – 2007 L-H transition studies on JET
Sponsored Links
This presentation is the property of its rightful owner.
1 / 19

Overview of 2006 – 2007 L-H transition studies on JET PowerPoint PPT Presentation


  • 67 Views
  • Uploaded on
  • Presentation posted in: General

Overview of 2006 – 2007 L-H transition studies on JET. Y Andrew CDBM ITPA Meeting, Lausanne, Switzerland 7 – 10 th May 2007.

Download Presentation

Overview of 2006 – 2007 L-H transition studies on JET

An Image/Link below is provided (as is) to download presentation

Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author.While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server.


- - - - - - - - - - - - - - - - - - - - - - - - - - E N D - - - - - - - - - - - - - - - - - - - - - - - - - -

Presentation Transcript


Overview of 2006 – 2007 L-H transition studies on JET

Y Andrew

CDBM ITPA Meeting, Lausanne, Switzerland

7 – 10th May 2007


Y Andrew1*, NC Hawkes1, Y Martin2, R Sartori3, V Parail1, TM Biewer4, K Crombe5, C Giroud1, A Korotkov1, E de la Luna6, V Naulin7, I Nunes8, G Saibene3, P de Vries1 and JET-EFDA contributors#

  • Euratom/UKAEA Fusion Association, Culham Science Centre, Abingdon, OX14 3DB, UK

  • EPFL/CRPP Association Euratom, Lausanne, Switzerland

  • 3. EFDA Close Support Unit, Garching, 2 Boltzmannstrasse, Garching (DE) Germany

  • 4. Oak Ridge National Laboratory, Oak Rdige, TN 37831, USA

  • 5. Department of Applied Physics, Ghent University, Belgium

  • 6. Associacion Euratom/CIEMAT para Fusion, Madrid, Spain

  • 7. Risoe National Laboratory Technical University of Denmark, OPL-128, 4000 Roskilde, Denmark

  • 8. Centro de Fusão Nuclear, Associacão EURATOM-IST, Lisboa, Portugal

    * yasmin.andrew@jet.uk

  • # See appendix of M Watkins et al., Fusion Energy 2006 (Proc. 21st Int. Conf. Chengdu, 2006) IAEA Vienna (2006)


Outline

  • Background

  • Effect of new JET Divertor of H-mode Access

  • H-mode Access with ‘ITER-like’ magnetic configuration

  • Influence of X-point location

  • Ip scan

  • Bt scan

  • Effect of TF Ripple on H-mode access

  • Type-III to Type-I ELM access


Experimental Method

L-mode

H-mode

  • H-mode threshold measurements performed on JET by ramping the input power by typically 1 MW/s to follow the L-H and H-L transitions

  • Power threshold is defined as:

  • Pth = Pin+POH-dWdia/dt

  • at the transition to H-mode

  • L-mode density is held constant using feedback control

Da

Power

Wdia

Edge ne

Edge Ti

Edge Vtor

Edge Vpol


New Divertor

MkII LBSRP

MkII SRP

HT3

2003

HT3

2006


New Divertor has no effect on Pth

  • Density scan repeated for HT3 configuration with new divertor


Increasing dlower

Proximity of X-point to divertor wall increasing

V/SFE/LT

2003

HT3

2003/2006

ITER-like

2006


ITER-like configuration

  • ITER-like configuration Pth demonstrates weaker density dependence


X-point height scan

ITER-like configuration with X-point

(a) closer to inner wall and (b) reduced in height

(b)

(a)


Reduction in Pth

#68299

ITER-like optimised

#68300

ITER-like innermost X-point

#68301

ITER-like lowest X-point

Total Input Power

Edge Density

dlower


Ip scan

  • Some variation in density with increasing Ip, so observed trend most likely to be the result of density dependence

  • Need to account for ne dependence of Pth


Bt scan at fixed q95

  • Some variation in density with increasing Ip/Bt

  • Need to account for ne dependence of Pth


TF Ripple – low density

Ip/Bt = 2 MA/2.2 T, q95 = 3.7, d ~ 0.2

0.08 % - No Ripple

# 69638

1 % Ripple

# 69639

No significant difference between L-H transition for ‘No Ripple’ and 1 % Ripple shots at low density

4.3 MW

4.1 MW

Total Input Power

Edge ne

1.3x1019 m-3

3.70 m

3.83 m

Edge Ti


Edge CXRS Lines of Sight

# 69638 @ 60s

3.70 m

3.66 m

3.83 m

Ti (eV)

Mid-plane Radius (m)


TF Ripple – low density

Ip/Bt = 2 MA/2.2 T, q95 = 3.7, d ~ 0.2

0.08 % - No Ripple

# 69638

1 % Ripple

# 69639

Edge ne

  • ELM Da characteristics different for no-ripple and ripple shots

  • No significant difference in edge ne during evolution of H-mode between no-ripple and ripple case

  • Large differences in edge vtor are observed during the H-mode phase

  • Differences in vtor disappear following the transition back to L-mode

vtor

3.66 m

9 km s-1

3.70 m

-62 km s-1

vtor

3.83 m

vtor


TF Ripple – higher density

4.7 MW

#69641

0.08 % ripple

#69640

4.6 MW

1 % ripple

4.2 MW

#69646

1.3 % ripple

Total Input Power

Ti

ne

edge ne


Type-III Type I ELM Threshold

ITER-like configuration 2.5 MA/2.7 T

#68221

6.5 MW

#68221

#68218

7.2 MW

#68218

7.9 MW

#68220

8.8 MW

#68219

#68220

#68216

14.2 MW

#68216


Type-III  ELM-free Type III ELMs

ELM-free phases

#68221 ITER-like

Outer Divertor Da

  • The plasma does not drop out of H-mode

  • It has ELM-free H-mode phases:

  • Da signals remains low

  • ne increases due to lack of ELMs

  • Wdia increases

Edge ne

Wdia


Conclusions

  • Replacement of SRP has no influence on Pth

  • Pth of ITER-like configuration demonstrates much weaker density dependence

  • Lowering of X-point height shows more dramatic effect of Pth than inner wall proximity

  • Three point Ip scan carried out

  • Four point Bt scan carried out

  • Valuable set of data has been obtained on H-mode transitions on JET with different levels of Toroidal Field ripple at two different densities

  • Type-III to Type-I ELM transition studies started


  • Login