Dynamic fuel retention and release under ITER like wall conditions in JET
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Transcript of Dynamic fuel retention and release under ITER like wall conditions in JET
Dynamic fuel retention and release under ITER like wall conditions in JET V. Philipps1, T. Loarer2, M. Freisinger1, H.G.Esser1, S. Vartanian2, U. Kruezi3, S. Brezinsek1, G. Matthews3 and JET EFDA contributors
JET-EFDA, Culham Science Centre, OX14 3DB, Abingdon, UK1Forschungszentrum Jülich, Association EURATOM – FZJ, Jülich, Germany 2CEA, IRFM, F-13108 Saint-Paul-lez-Durance, France 3EURATOM/UKAEA Fusion Association, Culham Science Centre, UK. * See the Appendix to paper by F. Romanelli et al., Fusion Energy 2010 (Proc. 23st Int. Conf. Daejon, Republic of Korea, 2010) IAEA, Vienna 2010.
Background and MotivationBackground and Motivation JET with ITER-Like WallJET with ITER-Like Wall
Analysis of T retention under ITER like wall conditions is main objective of the JET ILW project .
Long term fuel (tritium) retention studied by gas balances using cryopump regeneration. Reduction of a factor >10 compared with C walls
This study: dynamic fuel retention (hydrogen retained during plasma operation and released in between discharges and over longer times (night etc.)
DiagnosticDiagnostic calibrated gas injection (JET GIMS)
Neutral pressure measurements in main chamber ( pennings) and subdivertor (baratrons)
Support form mass spectrometer data
Cross calibration of pennings versus baratrons
Consistency check: matching of particle balance in gas injection only ( no plasma)
Becoating
on Inconel
Bulk Be
Bulk W
Wcoating on CFC
Diverted plasma conditions Diverted plasma conditions Dynamic retention in Be walls ( limiter Dynamic retention in Be walls ( limiter
discharges)discharges)
82590 82600 82610 82620 826300
1x1020
2x1020
3x1020
4x1020
5x1020
6x1020
7x1020
8x1020
Shot Number
52 s
ec [7
.698
9e+02
0]
-8x1019
-7x1019
-6x1019
-5x1019
-4x1019
-3x1019
-2x1019
-1x1019
0
D
Wal
l re
ten
tio
n (
D/s
ec)
Gra
die
nt
of
rete
nti
on
(D
/sec
)
Initial wall retention rate (flat top density)
Gradient of retention (avarage over 5 sec)
Retention rate
Gradient
• Example of a long term limiter shot
• no sign of saturation
• 3x1022 D shot-end retention
40 50 60 700,0
0,5
1,0
0123
0
2
4
0
2
4
Plasma content
Wall retention
Cumulative injection
Subdivertor pressure
D x
10
23D x
10
21
D x
10
21
X 1
0-3 m
bar
Injection (circles) release until 770 sec (triangles) ,Extrapolated until next shot (squares)
Regeneration
Good agreement→ all dynamic retention released 82590 82600 82610 82620 82630
0
2
4
6
8
10
12
14
Inje
ctio
n (bar
l)
Shotnumber
injection
Release
Cryopump regeneration
Integral deuterium injection (dynamic wall retention in absence of pumping) and particle release for all limiter shots (limiterdatabase)
Retention at shot end up to 3x 10 22
• Strong wall retention in start of divertor phase
• Fast decay within few sec • ≈100% of retained deuterium released
in between shots (within data accuracy )
• Dverted plasmas: plasma interaction largely with W surfaces (+Be-deposits)
• reduced contact with Be walls
Stronger initial retention in divertor phase
Decay phase (1.4→ 0.4 x 1021/sec)
Flat phase : 4x 1020 D/sec No saturation
L-mode diverted, no cryopump active
0
2
4
6
Wal
l ret
enti
on
(x
1021
#/s
ec)
0
2
4
6
(x 1
021 )
Retention rate
Plasma content
40 45 50 55 60 65 700,0
0,5
1,0
1,5
2,0
2,5
(x
1022
D-a
tom
s)
Time
Cumulative retention
Limiter phase
Divertor phase
80655 80660 80665
0
4
8
12
16
20
24
Am
ount of gas ( b
arl
)
shotnumber
L-mode with cryopump
Injection
cryyopumping
Release after shot≈ dynamic retention
regeneration
With cryopump active, most injected D is pumped by cryopumps Evaluation of dynamic wall retention has larger uncertainty ( mismatch of regegeneration and integrated pressure data
Transient dynamic retention (> 1023 D-atoms, partly released during shot
100 1000 100001E-11
1E-10
1E-9
Ma
ss
4 s
ign
la (
arb
it u
n.)
Time after discharge (s)
Particle ( D) release after shots follows a power law
t– 0.7 ±0.1
t – 0.7 ±0.1
• Transient wall retention in density ramps with fast release during shot
• Particle release after shot with power law t– 0.7 ±0.1 for long times
• Reproducible retention of Be-walls ≈1.5 -0.4 x1021 D/sec (flat top, no memory effect of previous shots)• Retention rate decreases only slightly with time ( 0-8 % /sec) , no saturation in JET time scales • D-release behavior after discharge ≈ t– 0.7 ±0.1 (very similar to C wall conditions) • Nearly all dynamically retained D is released in between shots (within data accuracy) • Be retention will provide sufficient wall pumping for start up phase in ITER
Wall retention during limiter and divertor phase
Injection
Release 740 sec and til next shot
Limiter
Divertor
0,0
0,5
1,0
1,5
2,0
Re
ten
tio
n ( x
10
22 D
-at.)
81940 81950 81960 819700
4
8
12
16
Am
ou
nt
of
ga
s (
ba
rl)
shotnumber
Injection and release (740 sec and extrapolated to next shot ) + cryopump
regeneration
X 1
021
D-a
tom
s x
1022
D-a
tom
s x
1023
pre
ssur
e (m
bar)
82305
0
2
4
6
-8
-4
0
4
40 45 50 55 60 650,000
0,004
0,008
40 45 50 55 60 65 700,0
0,4
0,8
1,2
a b
c d
Time ( sec)
Plasma content
Div pressure
Retention rate
Total retention
40 45 50 55 60 65 70 75 80
0,0
0,2
0,4
0
1
2
0
1
2
012
(x 1
022 )
(x 1
021 /s
ec )
(x 1
0-3 m
bar )
Div pressure
Retention rate
Cumulative retention
Plasma content
30 consecutive repredocucible limiter shots
Time ( sec)
Time ( sec)
Typical shot
AcknowledgementsThis work was supported by EURATOM and carried out within the framework of theEuropean Fusion Development Agreement. The views and opinions expressed herein do
not necessarily reflect those of the European Commission.