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Gas Balance - fuel retention in JET T Loarer, J Bucalossi, D Brennan*, G Matthews*,

Association Euratom-Cea. TORE SUPRA. 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

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Gas Balance - fuel retention in JET T Loarer, J Bucalossi, D Brennan*, G Matthews*,

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  1. AssociationEuratom-Cea TORE SUPRA 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.

  2. 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 D2 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) Assessment of fuel retention in JET

  3. 6th February39 consecutive and repetitive discharges# 62887 to 62926DOC-L and L-modeIp=2MA BT=2.4T ICRH =3MW <ne>=3.8 1019m-3Gas rate~1.5 1022 Ds-1~4.3 Bar.l per dischargeSteady state ~ 11s.

  4. Overall gas balanceTotal 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: Scryo_vessel=125m3s-1Balance during the dry run : Pressure and time constant : very good agreementFor these pulses : outgasing between discharges ~ 15% of the injected fluxExhausted flux during the pulse adjusted during the pulse : retention of 15% of the injected flux

  5. Particle fluxes : Gas injection only by - GIM 7 : ~2/3- GIM 8 : ~1/3(top of the machine)Retention :(Fpuff - Fexh)/ Fpuff ~ 15% Particle balance for one typical discharge of the series # 62925

  6. Balance- Injected : 4.48 Bar.l- Pumped :3.81 Bar.l- Wall : 0.67 Bar.lOutgasing 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. Comp. with the ref. pulse 61751 (Nov 2003) Psub_div61751 < Psub_div62925 Scryo61751= Scryo62925 Since Inj61751>Inj62925 Ret # 61751 (35%)> # 62925 (15%) Difference from plasma geometry ? 5.95 Barl 4.5 Barl

  8. 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 sec50% @ t~60 sec

  9. Balance- Injected : 5.95 Bar.l- Pumped :4.14 Bar.l- Wall : 1.78 Bar.lRetention at the end of the pulse : 30% Integral particle balance reference pulse # 61751 Outgasing after the end of the pulse…

  10. Recovery after the reference pulse… Ref pulse Series Pvessel61751 < Pvessel62925 Less particles recovered…after the pulse with the highest retention!

  11. Figure to be revisited… but not a « simple » drop of the values !

  12. 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 ? - Scryo 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 1022s-1) H-mode... Conclusions

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