1. TC-2 – Power ratio April 2011, San Diego
Yves Martin
Centre de Recherches en Physique des Plasmas
Association Euratom - Confédération Suisse
Ecole Polytechnique Fédérale de Lausanne (EPFL)
CH Lausanne, Switzerland

2. Outline Introduction Status Next step(s)
Results from devices
Synthesis
Next step(s)
Discussion on TC-2 contribution to H-mode WS
T&C ITPA Meeting, San Diego, April 2011

3. Introduction TC-2 Goals of TC-2
Characterise existing data with PL/Pthresh~1 and H~1
Identify stationary phases in each device
Characterise the plasma conditions
Compare findings
Test a discharge scenario to reach a H~1 regime at high density (0.8 nGr) with minimum additional power
L-H transition at low density (0.4 nGr) with P~Pthresh
Characterise confinement (H factor, ELMs, …)
Move to the target density of 0.8 nGr (naturally + ev. gas puff) without increasing power
Characterise confinement (H factor, ELMs, ...)
Increase power either before L-H transition or during density ramp to reach H~1
T&C ITPA Meeting, San Diego, April 2011

4. Status Input from ASDEX Upgrade Alcator C-mod DIII-D JET NSTX TCV
T&C ITPA Meeting, San Diego, April 2011

5. ASDEX Upgrade Identification Hysteresis
F.Ryter et al. JPCS (2008)
PLTH/PThr<1.6; 3<q95<6; large density range
H~1 with PLTH~PThr. Type I ELMs – higher pedestal pressure
bN~2 with PLTH/PThr~1.2
Some data with PLTH/PThr<1; type III ELMs with reduced confinement
Density saturation at n/nG~0.7 in type I ELMs
At higher triangularity. With slow ELMs (large ELMS?!(YM))
Hysteresis
Back transition, H-L, known to occur at lower power
Dedicated experiments recently done
T&C ITPA Meeting, San Diego, April 2011

6. Alcator C-mod Identification Hysteresis J.W.Hughes et al. IAEA 2010
Little data at PLTH/PThr~1. More around 1.5.
PNET, including core radiated power, better aligns EDA and ELMy H-modes in H98y2 vs PLTH/PThr plan
Hysteresis
Clear hysteresis (x2) in PLTH ramp-down
T&C ITPA Meeting, San Diego, April 2011

7. DIII-D Identification E.J.Doyle: APS DPP, 2010
Reference cases for ITER, both H98y2~1
High density, PLTH/PThr~1, large ELMS
Low density, PLTH/PThr>>1, ITER collisionality
T&C ITPA Meeting, San Diego, April 2011

8. JET Identification PL~1.6 x Pscal @ ne/nG ~ 0.4
For H~1, PL ~ 2 x PScal.
Type I ELMs
E.de la Luna, M.Beurskens, PEP29, ITPA PEP 2011
Vertical kicks
T&C ITPA Meeting, San Diego, April 2011

9. NSTX
Identification
H-L transition at PL<PTh (less dependent of density)
H~1 with PL~PTh. Done with RF/NB in He/D, ELM free, but not crystal clear (shaping?)
T&C ITPA Meeting, San Diego, April 2011

10. TCV Identification Hysteresis
Ohmic H-mode, PLTH/PThr~1, H98y2<<1
ECH H-mode, PLTH/PThr>>1, H98y2~1
Hysteresis
Experiments planned
T&C ITPA Meeting, San Diego, April 2011

11. Synthesis - Main trends
Starting point
Most machines usually operate at PLTH/PThr>>1 to obtain H98y2<<1
Identification of discharges at PLTH/PThr~1: done
Large, low frequency ELMs
Same cases with more tolerable ELMs, but in specific conditions
More and more awareness in talks, papers, …
Hysteresis Joint Experiment
Hysteresis observed in many devices in P ramp downs
TC-2 scenario not performed
T&C ITPA Meeting, San Diego, April 2011

12. Joint experiment Goal Relies on
Operate a device in high density, good confinement, H- mode with an available power close to the H-mode threshold power
Obtain H-mode at low density, low power
Increase density without increasing power
Relies on
Hysteresis (PLTH/PThr<1)
Good confinement close to threshold
Fueling H-mode plasma in large devices
… L-H transition in current ramp …
T&C ITPA Meeting, San Diego, April 2011

13. Joint experiment
Goal
Map discharge evolution in H98y2 vs PLTH/PThr plan
With existing data
With data from the dedicated experiment
Important for ITER scenario preparation
T&C ITPA Meeting, San Diego, April 2011

14. Scope of the H-mode WS Contribution
Introduction
ITER requirements (ITER, threshold power, H-D-DT phases, scenarios, …)
Summary of the experiments
Device by device
Synthesis – Discussion
Main trends
Compatibility with ITER
Joint experiment
Existing trajectories
Our plans / intentions
Conclusion
Path to the success ?
Warning ?
T&C ITPA Meeting, San Diego, April 2011

15. Organisation - Agenda Analysis Abstract Paper Requirements 2 months
Paper
Not required, decide later ?
Requirements
Commitment from all representatives
Most recent dedicated publications, all relevant
Data of discharge evolution
T&C ITPA Meeting, San Diego, April 2011