E. Joffrin 1 (2) ITPA-IOS meeting (Oct 2011)

Joint Experiment IOS-4.1

• Access conditions for advanced inductive (hybrid) scenario with ITER-relevant restriction

• Key persons: – E. Joffrin (JET)– P Politzer + G. Jackson (DIII-D)– J. Hobirk (AUG)– A. Hubbard (C-MOD)– T. Suzuki (JT60U)– Gerhardt (NSTX)

• Aims:– Document plasma conditions to obtain a selected number of q

profiles for the hybrid scenario at N close to 3 – Document experimentally in each device the effect of q profile on

confinement and stability before current profile relaxes.

E. Joffrin 2 (2) ITPA-IOS meeting (Oct 2011)

DIII-D / JET Experiment

Reminder of previous work:

1) List of physics parameters for the documentation discussed and circulated

2) Database produced in JET and DIII-D separately (presented at the Culham meeting).

JET database now in the hands of GA, since last week.

Discussion have started with J. Hobirk.

DIII-D database extended to hybrid scenario (action from previous meeting)

JET database analysed in terms of q95.

Key issues:1- What is the best criteria for defining success?

N>2.3 is incomplete since it could be achieved at high power with poor confinement (with MHD for example). The confinement alone does not tell you about the maximum pressure.

Nmax.<H> could offer an alternative between these 2 conditions

E. Joffrin 3 (2) ITPA-IOS meeting (Oct 2011)

Nmax.<H>

Li (target at 95% of Ip ramp)

3.5<q95<4.5 4.5<q95<5.5

q95- qo (target)

Performance as function of q95:- The initial li may impact on steady state (in red) performance. High initial li seems favorable.- a large variety of initial target has been explored for the steady state. Low initial q looks more favorable. Hybrids and steady state are achieving similar performance in the same domain.

<H> time averaged over the duration when N>1.5

E. Joffrin 4 (2) ITPA-IOS meeting (Oct 2011)

Nmax.H

Ip overshoot seem to produce the best performance

Li (target at 95% of Ip ramp)

E. Joffrin 5 (2) ITPA-IOS meeting (Oct 2011)

E. Joffrin 6 (2) ITPA-IOS meeting (Oct 2011)

E. Joffrin 7 (2) ITPA-IOS meeting (Oct 2011)

What experiment can we draw from the data base analysis?

This point is not directly obvious from the database analysis from one single machine and combining results may shed some light on the q profile access since operating conditions are usually different

A possible but academic way forward could be to merge the experimental objectives of 3.2 and 4.1 and develop an JE that focuses on reproducing 3 classes of identical target q profiles in the different machines: (qo~1, q95=4) ; (qo~1, q95=5) (qo>2, q95=5) at different values from 2.5 to 4 and on short duration (<R/2). This would have the objective to document the physics continuum in the (q,P) space independently from a particular scenario.

Evidence are suggesting that “broad” profiles is favourable (DIII-D, JET, AUG). So another option could be to focus on identical “broad” q profile target with qo>~1 + q95~4 and q>2+q95~5 (using for example the current overshoot) which has been tried in different way on JET and AUG already to explore its impact on stability / transport on short duration (<R/2) when N (power) is increased.

The proposal is to:The proposal is to:

- Overlay the DIII-D and JET database data and possibly AUG data.

- Write the design of an experiment for an identity q profile experiment using the Ip overshoot for both q95=4 and 5.