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Joint Experiment IOS-4.1

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:

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Joint Experiment IOS-4.1

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  1. 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 bN close to 3 • Document experimentally in each device the effect of q profile on confinement and stability before current profile relaxes.

  2. DIII-D / JET Experiment • Reminder of previous work: • List of physics parameters for the documentation discussed and circulated • 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? • bN>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. • bNmax.<H> could offer an alternative between these 2 conditions

  3. 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. bNmax.<H> Li (target at 95% of Ip ramp) q95- qo (target) 3.5<q95<4.5 4.5<q95<5.5 <H> time averaged over the duration when bN>1.5

  4. Ip overshoot seem to produce the best performance bNmax.H Li (target at 95% of Ip ramp)

  5. 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 b values from 2.5 to 4 and on short duration (<tR/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 (<tR/2)when bN (power) is increased. • The proposalis to: • Overlay the DIII-D and JET database data and possibly AUG data. • Write the design of an experiment for an identity q profile experimentusing the Ipovershoot for both q95=4 and 5.

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