1. T Loarer – TFE meeting – 20 February 2004 1 TORE SUPRA Association Euratom-Cea Gas Balance - fuel retention in JET T Loarer, J Bucalossi, D Brennan*, G Matthews*, V Philipps°, P Morgan*, M Stamp*, E Tsitrone and JET-EFDA Collaborators Association EURATOM-CEA, DSM-DRFC, CEA Cadarache, 13108 St Paul lez Durance, France *Euratom-UKAEA Association, Fusion Culham Science Centre, Abingdon,OX14 3EA, UK. TORE SUPRA Association Euratom-Cea

2. T Loarer – TFE meeting – 20 February 2004 2 TORE SUPRA Association Euratom-Cea Assessment of fuel retention in JET Aim: perform a gas balance with the maximum accuracy Divertor Cryopump regeneration just before and just after the session (+ gas analysis) no NBI (no LHCD) to avoid NBI Box (LHCD) pumping no disruption high D 2 fuelling rate and maximum pulse rate Reference pulse # 61751: 2MA/2.43T, 5-6MW ICRH, high density Gas ~6 Bar.l, with QMB… dry run with gas puff (to check divertor pumping speed) 40 pulses at 6 Bar.l/pulse  ~ 240 bar.l (reasonable for PCD and GB)

3. T Loarer – TFE meeting – 20 February 2004 3 TORE SUPRA Association Euratom-Cea 6 th February 39 consecutive and repetitive discharges # 62887 to 62926 DOC-L and L-mode I p =2MA B T =2.4T ICRH =3MW =3.8 10 19 m -3 Gas rate~1.5 10 22 Ds -1 ~4.3 Bar.l per discharge Steady state ~ 11s.

4. T Loarer – TFE meeting – 20 February 2004 4 TORE SUPRA Association Euratom-Cea Overall gas balance Total injected : 159.6 Barl (from PPF data) – 170 Barl from (AGHS) Total recovered : 171.9 Barl (from AGHS – regeneration N°PD-493) Balance : Excess of 12 Barl. Equilibrium assumed in a first approximation. The outgasing between pulses is calculated - Neutral pressure in the vessel (DPF when available): PRES/PEN3 - Resulting pumping speed of the cryopump in the vessel: S cryo_vessel =125m 3 s -1 Balance during the dry run : Pressure and time constant : very good agreement For these pulses : outgasing between discharges ~ 15% of the injected flux Exhausted flux during the pulse adjusted during the pulse : retention of 15% of the injected flux

5. T Loarer – TFE meeting – 20 February 2004 5 TORE SUPRA Association Euratom-Cea Particle fluxes : Gas injection only by - GIM 7 : ~2/3 - GIM 8 : ~1/3 (top of the machine) Retention : (  puff  exh ) /  puff ~ 15% Particle balance for one typical discharge of the series # 62925

6. T Loarer – TFE meeting – 20 February 2004 6 TORE SUPRA Association Euratom-Cea Balance - Injected : 4.48 Bar.l - Pumped :3.81 Bar.l - Wall : 0.67 Bar.l Outgasing after the pulse : 0.67 Bar.l Integral particle balance # 62925 If we assume that the pumped flux is consistent for this series What are the consequences for the “old” data ?

7. T Loarer – TFE meeting – 20 February 2004 7 TORE SUPRA Association Euratom-Cea Comp. with the ref. pulse 61751 (Nov 2003) P sub_div 61751 < P sub_div 62925 S cryo 61751= S cryo 62925 Since Inj 61751 >Inj 62925 Ret # 61751 (35%)> # 62925 (15%) Difference from plasma geometry ? 5.95 Barl 4.5 Barl

8. T Loarer – TFE meeting – 20 February 2004 8 TORE SUPRA Association Euratom-Cea Particle balance for the reference pulse # 61751 -Particle fluxes : Gas injection by - GIM 8 : ~1/2 (top) GIM 10 : ~1/2 (Div Out Ring) Retention : 30% @ t~58 sec 50% @ t~60 sec

9. T Loarer – TFE meeting – 20 February 2004 9 TORE SUPRA Association Euratom-Cea Balance - Injected : 5.95 Bar.l - Pumped :4.14 Bar.l - Wall : 1.78 Bar.l Retention at the end of the pulse : 30% Integral particle balance reference pulse # 61751 Outgasing after the end of the pulse…

10. T Loarer – TFE meeting – 20 February 2004 10 TORE SUPRA Association Euratom-Cea Recovery after the reference pulse… Ref pulseSeries P vessel 61751 < P vessel 62925 Less particles recovered…after the pulse with the highest retention!

11. T Loarer – TFE meeting – 20 February 2004 11 TORE SUPRA Association Euratom-Cea Figure to be revisited… but not a « simple » drop of the values !

12. T Loarer – TFE meeting – 20 February 2004 12 TORE SUPRA Association Euratom-Cea Conclusions In the light of these results - Speak to the experts on gas injection (going on) - Geometry of the plasma to be considered (DOC-L, U…) - Revisit the previous results on the retention - cryopump regeneration and pressure gauge calibrations - Consistency with the 40% of tritium retention during the first phase of the DTE1 ? - S cryo to be adjusted with regards to the plasma geometry in the divertor ? -Repeat (?) under different conditions - Long discharges in JET : increase plasma duration = increasing of the outgasing flux between pulses ? (~ No effect in Tore Supra) - Geometry on the particle retention - Strong fueling (7-8 10 22 s -1 ) H-mode...