V.Philipps, SEWG Gas balance and fuel removal, JET, 22.7.08, Association EURATOM – FZJ Effect of...

V.Philipps, SEWG Gas balance and fuel removal, JET, 22.7.08 , Association EURATOM – FZJ

Effect of disruptions on fuel release from JET wallsV. Philipps, M. Freisinger, A.Huber, T. Loarer and JET EFDA

contributors

Motivation• Disruptions affect gas balance measurements by additional

particle release• proposed as a possible T-removal method in ITER (controlled

mitigated disruptions)

This work

Long term study of particle injection and release in between discharges for disruptive and non disruptive shots in C5-C14 JET campaigns (2002-2004 )


Experimental method

Long term data (≈ 700sec ) of main chamber penning gauges

routinely check of calibration using dry gas injections

restriction of data base to all shots with

- long term penning data

- pumping by

- divertor cryopump (125m3/sec)

- main vessel turbopumps (8m3/sec)

- and 2 NBI beam crypopumps (40m3/sec each)


Number of shots

Number of disruptions

Average injection/shot (atoms)

Integrated injection (atoms)

Overall campaign

7297 709 (9.7% ) 7.12 x1022 5.2x 1026

Database 1091 112 (10% ) 9.7 x 1022 1.05x 1026

Database


70

0.0

4.0x10-5

8.0x10-5

0.0

8.0x105

1.6x106

4 1020/sec

1021D/sec

Pre

ssu

re (

mb

ar)

Time (sec)

Cu

rren

t

current

Pressure < 10-5 mbar

Particle release after non disruptive shots


Q (t) t n , n = -0.6

1 10 100

1019

1020

Time (sec)

rel

ease

rat

e (

D-a

tom

s/se

c)

Shot 69269

JET

TEXTOR

1 10 100 1E3 1E4 1E5

1016

1017

1018

1019

1020 # 80417T

Liner = 350 °C

12 h1 h

t-0.74

QMS D2

Total pressure

Rel

ease

rat

e [D

-ato

ms/

s]

Time after end of discharge [s]

1h

12h


• Long tail of particle release after non disruptive shots

• Pumping” of neutrals by plasma until very end of discharge

• Release just after the shot ≈ recycling flux at plasma end

• Consistent total release for all nondisruptive shots , average value 1.8 1022 atoms, does not correlate directly with amount of fuelling (quasi-saturation of dynamic wall inventory)

• Represents dynamic wall inventory in C- walls at ≈ 200C (1016/cm2, 10% of saturation value for erosion areas)


56000 58000 600000

1x1022

2x1022

3x1022

4x1022

5x1022

6x1022

To

tal r

ele

ase

up

to

70

0s (

ato

ms)

Shot number

Absolute particle release up to 700sec for all non disruptive shots (1091 shots)

Mean release: 1.8 x 1022/shot


56000 58000 600000.0

0.5

1.0

1.5

2.0

2.5

3.0

3.5

exh

au

st u

p t

o 5

0se

c/e

xha

ust

up

to

10

sec

Shot number

release up to 50sec/release up to 10sec for all nondisruptive and disruptive shots


0.0 2.0x106 4.0x106 6.0x106 8.0x1060.0

2.0x1022

4.0x1022

6.0x1022

8.0x1022

1.0x1023

Stored energy

Inte

grat

ed re

leas

e af

ter s

hot

Mean value of non disruptive shots


0.0 3.0x106 6.0x1061.0

1.2

1.4

1.6

1.8

2.0

Plasma stored energy (Joule)

Fra

ctio

n E

xhau

st (

50se

c)/e

xhau

st(1

0sec

)


Summary

All disruptive shots show a larger particle release

Release increases with stored energy

Temporal characteristic consistent with an instantaneous particle release during disruption ( similar a sin gas injection)

Consistent with thermal outgassing from disruptive heated areas

Additional release: ≈ 2x1022/dis = 40g D/campaign (7000shots, 10% disruptions), but effect on long term retention only possible for release from deposition dominated areasDisruptive release contribute to reduce fuel inventory on plasmaetted areas (≈0.1-0.2D/C) but not on remote areas (D/C ≈ 0.5-1)


surface concentration

≈1-5 1021D/m2

Erosion area: released fuel will be refilled

Deposition area: new layer deposited on top of existing

disruptive release can reduce inventory

1 m C layer

≈3 x 1022D/m2


100 200 300 400

0.0

4.0x10-6

8.0x10-6

1.2x10-5

1.6x10-5

2.0x10-5

Pre

ssu

re (

mb

ar )

Time (sec)

Pressure in main chamber

Shot 69269

4 x 10-7 mbar 9 x 10-7 mbar

shot

After shot

V.Philipps, SEWG Gas balance and fuel removal, JET, 22.7.08, Association EURATOM – FZJ Effect of...

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