T Loarer – TFE meeting – 20 February 2004 1

TORE SUPRA

AssociationEuratom-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

AssociationEuratom-Cea

 

T Loarer – TFE meeting – 20 February 2004 2

TORE SUPRA

AssociationEuratom-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 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)

T Loarer – TFE meeting – 20 February 2004 3

TORE SUPRA

AssociationEuratom-Cea

6th February39 consecutive and repetitive discharges# 62887 to 62926 DOC-L and L-modeIp=2MA

BT=2.4T

ICRH =3MW <ne>=3.8 1019m-3

Gas rate~1.5 1022 Ds-1 ~4.3 Bar.l per discharge

Steady state ~ 11s.

T Loarer – TFE meeting – 20 February 2004 4

TORE SUPRA

AssociationEuratom-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: Scryo_vessel=125m3s-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

T Loarer – TFE meeting – 20 February 2004 5

TORE SUPRA

AssociationEuratom-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

T Loarer – TFE meeting – 20 February 2004 6

TORE SUPRA

AssociationEuratom-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 ?

T Loarer – TFE meeting – 20 February 2004 7

TORE SUPRA

AssociationEuratom-Cea

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

T Loarer – TFE meeting – 20 February 2004 8

TORE SUPRA

AssociationEuratom-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 sec50% @ t~60 sec

T Loarer – TFE meeting – 20 February 2004 9

TORE SUPRA

AssociationEuratom-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…

T Loarer – TFE meeting – 20 February 2004 10

TORE SUPRA

AssociationEuratom-Cea

Recovery after the reference pulse…

Ref pulse Series

Pvessel61751 < Pvessel62925

Less particles recovered…after the pulse with the highest retention!

T Loarer – TFE meeting – 20 February 2004 11

TORE SUPRA

AssociationEuratom-Cea

Figure to be revisited…1.0

0.8

0.6

0.4

0.2

0.0

Ret

enti

on

1086420

puff (1022

s-1

)

H mode (6 MW) H mode (17 MW) H mode Reversed B L mode Long (4 MW)

but not a « simple » drop of the values !

T Loarer – TFE meeting – 20 February 2004 12

TORE SUPRA

AssociationEuratom-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 ?

- 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...