tore supra 1 d. douai recent results on ion cyclotron wall conditioning 15 april 2010 recent results...
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1D. Douai Recent results on Ion Cyclotron Wall conditioning 15 April 2010
TORE SUPRA
Recent results on ICWC
D. Douai1, A. Lyssoivan2, V. Philipps3, S. Brezinsek3, V. Rohde4, T. Wauters1,2 T.Blackman5, V. Bobkov4, S. Brémond1, E. de la Cal6, T.Coyne5, M. Garcia-Munoz4, E. Gauthier1, M.Graham5, S.Jachmich2, E.Joffrin1, A. Kreter3, P.U. Lamalle7, E.Lerche2, G.Lombard1, M. Maslov5, M.-L. Mayoral5, P. Mollard1, I. Monakhov5, A.Miller5 , J.-M. Noterdaeme4,8, J. Ongena2, M.K. Paul3,
B. Pégourié1, R. Pitts7, V. Plyusnin9, F.C. Schüller7, G. Sergienko3, M. Shimada7, W. Suttrop4, C.Sozzi10, M.Tsalas11, E. Tsitrone1, D.Van Eester2, the TORE SUPRA Team, the TEXTOR Team, the ASDEX Upgrade Team and JET EFDA
Contributors*
1CEA, IRFM, Association Euratom-CEA, 13108 St Paul lez Durance, France.2LPP-ERM/KMS, Association Euratom-Belgian State, 1000 Brussels, Belgium, TEC partner.3IEF-Plasmaphysik FZ Jülich, Euratom Association, 52425 Jülich, Germany, TEC partner4Max-Planck Institut für Plasmaphysik, Euratom Association, 85748 Garching, Germany.5CCFE, Culham Science Centre, OX14 3DB, Abingdon, UK.6Laboratorio Nacional de Fusión, Association Euratom-CIEMAT, 28040 Madrid, Spain.7ITER International Organization, F-13067 St Paul lez Durance, France.8Gent University, EESA Department, B-9000 Gent, Belgium.9Centro de FNIST, Association Euratom-IST, 1049-001 Lisboa, Portugal.10IFP CNR, EURATOM ENEA CNR Fusion Association, Milano Italy.11NCSR ‘Demokritos’, Athens, Greece*See the Appendix of F. Romanelli et al., Proc. 22nd Int. FEC Geneva, IAEA (2008)
Plan:- Context- Selection of obtained experimental (and numerical)
results on TORE SUPRA, TEXTOR, AUG and JET- Conclusion & future plans
ERM-KMS
LPP
2D. Douai Recent results on Ion Cyclotron Wall conditioning 15 April 2010
TORE SUPRAContext
Conventional Glow Discharge Conditioning inefficient in the presence of permanent Btor
Need for alternative wall conditioning techniques compatible with Btor
- Plasma initiation (Impurities, fuel removal)
- Control of discharge content (isotopic ratio)
- Tritium removal in ITER
ICWC : the most promising one : low energy + fast neutrals
Experiments conducted in TS, Textor, AUG and JET in the frame of a collaborative work
Context
Goals:
•Characterization of Ion Cyclotron Wall Conditioning (ICWC) discharges
•Optimization and assessment of efficiency
ERM-KMS
LPP
3D. Douai Recent results on Ion Cyclotron Wall conditioning 15 April 2010
TORE SUPRAMain parameters of ICWC discharges
BT = 3,8 T (1-x)He:xH2, x = 00,6 pTorus = 5.10-2 10-1 Pa Sinusoidal BR+BV
Freq. = 48 MHz (ITER 40-55 MHz) 25 kW < PICRF < 150 kW 0 and -phasing operation CW and pulsed operation
Q2 RF antenna0,72 m
Exhaust + MS
Superconducting tokamak R = 2.4 m, a = 0,72 m ~ 70 m2 stainless steel alloy 316L ~ 14 m2 CFC N11 Twall = 120°C
1H ICR
4D. Douai Recent results on Ion Cyclotron Wall conditioning 15 April 2010
TORE SUPRA
-5 0 5 10 15 200
0.1
0.2
0.3
0.4
0.5
0.6
0.7
time (sec.)
n H/[
n H+
n D]
#43447
#43485
nH/[nH+nD] in ohmic shots (by means of NPA)
after 15+3’ ICWC
Reference ohmic shot before ICWC
Isotopic ratio measured during reference ohmic shots on PTL
high isotopic exchange after ~15 min. ICWC in He-H2
Recovery to ohmic plasma after 3 min. He-ICWC discharge (walls saturated with H)
Isotopic exchange
What is the ratio between implanted and desorbed particles ?
5D. Douai Recent results on Ion Cyclotron Wall conditioning 15 April 2010
TORE SUPRA
Isotopic ratio change from 1 to 20 % after 60 sec. ICWC
After that, one NSB (wall saturation by H atoms)
-1 0 1 2 3 4 5 60
0.2
0.4
0.6
0.8
1
time (sec.)
H/H
+D
#24841: IP
=1MA, n~1020 m-3
#24861: IP
=0,6MA, n~1020 m-3
#24867: IP
=0,6MA, n~4.1019 m-3
Before ICWC
After ~60 sec. He:H2 ICWC
nH/[nH+nD] in ohmic shots (by means of NPA)AUG
Strong Hydrogen isotopicexchange also in all-W AUG
6D. Douai Recent results on Ion Cyclotron Wall conditioning 15 April 2010
TORE SUPRA
-20 0 20 40 60 80 100
10-6
10-4
10-2
100
times (sec.)
par
tial
pre
ssu
re (
Pa) HeH
2HD
D2
PRF
/100 (kW) Weak D2 partial pressure !
PHD ~ 3 10-3 PaQHD ~ 2.3 1018 mol./sRRHD ~ 2.7 1016 mol./m2/s
Himplanted = 2.3 1021
Dpumped = 2.2 1020
Himplanted/Dpumped ~ 10
Particle balance : outpumped particles vs. injected particles
TS#43463 PRF~50 kW, He-30% H2 - 60 sec. long continuous operation of Q2 antenna
HDHinjH NN2NN2implanted
HDDD NN2N2outpumped
Long term outgassing with t-0,6±0,1, indicating diffusion process of desorbed species
Isotopic exchange
7D. Douai Recent results on Ion Cyclotron Wall conditioning 15 April 2010
TORE SUPRA
P~0,1 Pa, PRF ~ 50 kW
H2 depletion is decreasing from 90 to 45% within 10 discharges
(i.e. ~10 min. He-H2 ICWC)
Wall saturation by H atoms
-20 0 20 40 60 80 1000
0.002
0.004
0.006
0.008
0.01
0.012
0.014
times (sec.)
par
tial
pre
ssu
re (
Pa)
H2
HD
D2
0 2 4 6 8 1040
50
60
70
80
90
number of shots
H2 D
ep
letio
n (
%)
Depletion = pH2/pH2
pH2
pH2
TS#43456 #43475
-20 0 20 40 60 80 1000
0.002
0.004
0.006
0.008
0.01
0.012
0.014
times (sec.)
par
tial
pre
ssu
re (
Pa)
H2
HD
D2
0 2 4 6 8 1040
50
60
70
80
90
number of shots
H2 D
ep
letio
n (
%)
Depletion = pH2/pH2
pH2
pH2
TS#43456 #43475
Wall saturation
8D. Douai Recent results on Ion Cyclotron Wall conditioning 15 April 2010
TORE SUPRA
-5 0 5 10 15 200
0.1
0.2
0.3
0.4
0.5
0.6
0.7
time (sec.)
n H/[
n H+
n D]
#43447
#43485
nH/[nH+nD] in ohmic shots (by means of NPA)
after 15+3’ ICWC
Reference ohmicshot before ICWC
-5 0 5 10 15 200
0.1
0.2
0.3
0.4
0.5
0.6
0.7
time (sec.)
n H/[
n H+
n D]
#43447
#43485
nH/[nH+nD] in ohmic shots (by means of NPA)
-5 0 5 10 15 200
0.1
0.2
0.3
0.4
0.5
0.6
0.7
time (sec.)
n H/[
n H+
n D]
#43447
#43485
nH/[nH+nD] in ohmic shots (by means of NPA)
after 15+3’ ICWC
Reference ohmicshot before ICWC
0 2 4 6 8 10 12 14 16 18 2010
18
1019
1020
1021
1022
1023
shot number
# p
arti
cles
H injected
H pumpedH impl wall
D pumped
60% H2
30% H2
45% H2
He ICRF
nH/n
D~0,5
nH/n
D~0,04
within ~ 850 sec. of CW ICWC in He-H2 :
Total D desorbed : 3,4.1021 D 2 “monolayers”Total H implanted : 3,2.1022 H Himplanted/Dpumped = 9.4
Some signs of equilibrium between ICWC and wall after 15 min.
HDH2HH 2injimplanted
HDD2D 2pumped
D removal and H implantation
9D. Douai Recent results on Ion Cyclotron Wall conditioning 15 April 2010
TORE SUPRA
1. Right after glow discharge almost all injected H is lost to the walls
2. Amount of out pumped D decreases from shot to shot change IR wall
3. Amount of H lost to the wall remains constant at the end of the day
At end of day wall flux becomes predominantly H
Study evolution of (D2-loaded) wall during isotope exchange experiments
26 Nearly identical He/H2 ICWC discharges
Similar result on TORE SUPRA, JET
Particle balance for every ICWC discharge
Also observed in Textor
10D. Douai Recent results on Ion Cyclotron Wall conditioning 15 April 2010
TORE SUPRARecovery from disruption (TS)
2 disruptions on outboard poloidal limiter at Ip=1,2 MA (dIp/dt ~360 MA/s)
Each time, recovery after only 1 pulsed He-ICWC discharge (ON/OFF = 2s/8s 10 pulses)
Low ohmic current pulsed discharges (“Taylor-like”)
He- ICWC
DC-glows He QHD ~ 1-2 1018 mol./s
Similar with other conditioning techniques
2440 2460 2480 2500 2520
10-4
10-3
10-2
10-1
time (min.)
pre
ssu
re (
Pa)
ICWC
disruptions
Ohmic shots
Non sustainedbreakdown
11D. Douai Recent results on Ion Cyclotron Wall conditioning 15 April 2010
TORE SUPRAPulsed ICWC discharges
Pulsed He-ICWC discharge, duty cycle = 2 sec. ON / 8 sec. OFF
Increase due to summation of aftershot pressure level
Decrease due to wall desaturation (approach to p(H2)= 0)
Duty cycle can be decreased 2:20 or more
New results on pulsed discharges under analysis
0 50 100 1500
0.002
0.004
0.006
0.008
0.01
time (sec.)40 45 50 55 60 65 700
0.002
0.004
0.006
0.008
0.01
time (sec.)
TS#43532 PRF~60 kW, ~0,1 Pa
12D. Douai Recent results on Ion Cyclotron Wall conditioning 15 April 2010
TORE SUPRASimulation of ITER full field ICWC on JET
Development of He / D2-ICWC operation in conditions similar to ITER full field operationi.e. BT=5.3 T and 40-55 MHz frequency band for the ITER ICRF system same (f/BT)-ratio at JET gives BT=3.3 T and 25 MHz for on-axis =CD
+ A2-D@ 25.21 MHz, [email protected] MHz.
ICRF A2 -C
ICR
F A
2-D
ICRF A2 -A
ICR
F A
2-B
1 2 3 4
12
34
4 3 2 1
43
21
1
2
3
4
5
6
7
8
GIM4 : He4, also GIM1 0 (H2/D2) & GIM12 (He4)
Pressure gauge s T03&T04
CCD camera
FIR Interferometer(KG1)
Core Spe ctroscopy(KT3)
Low Energy NPA (KR 2)
Vertical Bolometer cameras (KB1 )
VUV Spectros copy(KT2)
Horizon tal Bolometercameras (KB1 )
H-alpha
Wide Angle IR
H-alpha H-alpha
ILA
LHC
D
JET antennas used for ICWC
-1.0
-0.8
-0.6
-0.4
-0.2
0.0
0.2
0.4
0.6
0.8
1.0
1.2
-1.2
R m
inor
[m]
1.0 1.5 2.0 2.5 3.0 3.5 4.0
Bt [T]
JET, f=25 MHz
cD+
cD+
cH+
Location of ICR layers in JET Torus at f=25 MHz
13D. Douai Recent results on Ion Cyclotron Wall conditioning 15 April 2010
TORE SUPRA
Main concern: Arcing in the VTL due to the high neutral gas pressure.
– VTL pressure trips reduced to 10-5 mbar (~5.10-5 mbar in Torus)
– MTL voltages restricted to 20kV maximum
– New VSWR cards installed
– Maximum of 10 trips per pulse / 100 trips for the whole experiment
– risk reduced by applying the RF before the gas injection
42 44 46 48 50 52 540
50
100
150
200
250
300
0,0
1,0x10-5
2,0x10-5
3,0x10-5
4,0x10-5
5,0x10-5
RF
po
wer
at
gen
erat
or
(kW
)
time (sec.)
Ant. D Ant. C
Gas pressure
Gas p
ressure (m
bar)
9 sec. RF ON
KL1-8-w (Wide visible camera) # 78582
D2: 4He ~ 0.85:0.15
General waveform for RF and gas injection
Antenna safe operation
JET
14D. Douai Recent results on Ion Cyclotron Wall conditioning 15 April 2010
TORE SUPRA
reflectometry (KG10) ne measured up to R=3.0 m
t=45 sec.pulse #78579, <PRF>~ 60kW
43 44 45 46 47 48 49 50 51 5210
16
1017
1018
1019
time (sec.)
inte
gra
ted
lin
e d
en
sit
y (m
-2)
43 44 45 46 47 48 49 50 51 520
50
100
150
200
250
300
co
up
led
RF
po
we
r (kW
)
LID1
LID4
RF power
interferometry (KG1) ne higher at LFS than at HFS
pulse #79323, D2-ICWC
LID1(HFS)
LID4(LFS)
ECE Te ~ a fews tens of eV
Discharge characterisation
JET
not in agreement
15D. Douai Recent results on Ion Cyclotron Wall conditioning 15 April 2010
TORE SUPRA
40 50 60 70 80 90
2
4
6
8
10x 10
-5
time (sec.)
pa
rtia
l pre
ssu
re (
mb
ar) P
D2
PHe
He retention during shot
He puff
pulse #78588, He-ICWC
He retention in JET
Ex: pure He-ICWC pulse (#78588), coupled RF power = 80 kW Heimplanted = 8.1020
Doutgassed = 2.1021
Antenna protection limiters in Bulk Be
He retention also observed in all W AUG
0 5 10 1510
18
1019
1020
1021
1022
1023
shot
ato
ms
D injectedD pumpedD retainedHe injectedHe pumpedHe retained
pure He
ohmic
Partial pressures from optical Penning gauges
No wall preloading
Particle balance & He retention in
He containing ICWC discharges
Over the whole session:
• 25% of D retained during the session released with 2 pure He –ICWC shots
(no wall preloading)
• But 4% He/D measured in 1st ohmic (#78590)
x 2,5
16D. Douai Recent results on Ion Cyclotron Wall conditioning 15 April 2010
TORE SUPRA
-20 -10 0 10 20 30 40 50
10-6
10-5
10-4
10-3
10-2
discharge time (sec.)
par
tial
pre
ssu
re (
mb
ar)
-20 -10 0 10 20 30 40 50
100
101
102
103
cou
pled
RF
po
we
r (kW)
PRF
PH2,inj
Mass 2 (H2)
PHe,inj
Mass 4 (He,D2)
Mass 3 (HD)
He retention observed in AUG W-materials during ICWC Also observed in DC glows
Important He retention also seen in AUG
He puff
He retention during shot
AUG#28458 PRF-coupled~150-200 kW, He:H2=50:50
D release
AUG
Note: unfortunatelythe gas-injectionof H2 and He waskept on until t=16 s
17D. Douai Recent results on Ion Cyclotron Wall conditioning 15 April 2010
TORE SUPRA
3. Assessment of efficiency for wall conditioning / isotopic exchange
- wall pre-loading with H2-GDC hydrogen prior to the session
- NO reference OH shot
- Isotopic Exchange using D2-ICWC
- 8 identical RF discharges in D2 : p= 2.10-5 mbar, PRF,coupled = 250 kW, BV=30 mT
- Analysis of gas after the cryo-pump regeneration by chromatography
D/(H+D) increases by 30% (divertor) or 50% (midplane spectroscopy)
Higher D/H ratio measured by spectroscopy (KS3B horizontal channel) than with divertor Penning gauges
0 10 20 30 40 50 60 700
0.2
0.4
0.6
0.8
1
cumulated discharge time (sec.)
[D]/
([H
]+[D
])
from divertor Penningfrom mid-plane spectroscopy
18D. Douai Recent results on Ion Cyclotron Wall conditioning 15 April 2010
TORE SUPRA
0
2
4
1
3
x 10-4
mean injected pressure (mbar)
0
200
400mean coupled power (kW)
79321 79322 79323 79324 79325 79326 79327 793280
2
4
6
8
10x 10
21
shot number
num
ber
of a
tom
s
D injected
D pumped
D implanted
H pumped
within ~ 70 sec. of D2 –ICWC
+ post-discharge
1,8.1022 H outgassed 7 “monolayers”5,2.1022 D implanted
Houtgassed / Dimplanted= 0,3
From mass spectrometry (including post-discharge)
Particle balance
Pressure set to 2.10-5 mbar in the RF discharge
Some difficulties to couple RF power to discharges
Analysis by chromatography of gas after regeneration of cryo-pumping (incl. pumping time between discharges)
Note: H2 is weakly pumped by cryo-pumps at 4.8 K below 10 -5 mbar
Within 70 sec. D2-ICWC: 1,6.1022 H outgassed
4,8.1022 D retainedQH=1,2.1018 m-2.s-1
QD, retention =3,4.1018 m-2.s-1
to be compared with short term retention accessible by plasma operation : 2.1023 D atoms
19D. Douai Recent results on Ion Cyclotron Wall conditioning 15 April 2010
TORE SUPRA
1. Integrated fast CX D flux (∫4SJET.Ddt , with energies > 1keV) is function of RF coupled power
2. Influence of CX D flux on H pumped not obvious
3. D retention is higher than CX D flux
Influence of fast CX D neutrals vs. low D+?
0 10 20 30 40 50 60 7010
18
1019
1020
1021
1022
cumulated discharge time (sec.)at
om
s, t
ota
l flu
xes
to w
all
0 10 20 30 40 50 60 7010
0
101
102
103
104
cou
pled
RF
po
wer (kW
)
D retainedH pumpedintegrated 'fast' D flux to the wallsRF power
Fast CX neutrals (from NPA)
JET
0 10 20 30 40 50 6010
10
1011
1012
1013
1014
1015
1016
E (keV)
flu
x (k
eV-1
.m-2
.s-1
.sr-1
)
D
HT(H)=11.7 keVT(D)=14.8 keV
0 10 20 30 40 50 6010
10
1011
1012
1013
1014
1015
1016
E (keV)
flu
x (k
eV-1
.m-2
.s-1
.sr-1
)
D
HT(H)=11.7 keVT(D)=14.8 keV
D charge exchange neutrals measured up to 50 keVFast H-atoms (=1/2CH
+@r=0 absorption mechanism?)
20D. Douai Recent results on Ion Cyclotron Wall conditioning 15 April 2010
TORE SUPRA
Arcing traces on Q2 antenna straps Shallow damages due to “micro-arcs” that propagates at the surface of the strap
Deposition or heating pattern visible on FS, no arcing trace plasma between FS and straps Unipolar arcs
For P > 120 kW, antenna protection triggered on too high reflected power/forwarded power ratio within 10µsec., discharge stopped after 20 trig.
Q2 antenna
0 200 400 600 800 10000
20
40
60
80
100
120
140
160
180
cumulated time (sec.)
RF
po
wer
(kW
)
0 200 400 600 800 10000
20
40
60
80
100
120
140
160
180
cumulated time (sec.)
RF
po
wer
(kW
)
He ICWC
RF operation (TS)
21D. Douai Recent results on Ion Cyclotron Wall conditioning 15 April 2010
TORE SUPRA
Goal: qualify the routine operation and the reliability of Ion Cyclotron Wall Conditioning (ICWC) in view of ITER
disruption recovery manage H, D, T wall content control of the impurities influx
Exi
stin
g I
CR
Ftr
an
smitt
ers
To Tore Supra standard IC antenna (2 straps)
New ICWC dedicated antenna - upper port?(single or double strap low power -200 kW- simple design with double stub matching unit)
RF switch
Some specs:
Same frequencies (42-73 MHz),
Work at any BT
RF Power coupled to ICWC discharge : a few tens up to ~200 kW
Wide Working pressure range (a few 10-3 Pa up to a few Pa)
Dedicated ICWC antenna on TORE SUPRA
22D. Douai Recent results on Ion Cyclotron Wall conditioning 15 April 2010
TORE SUPRA
Modelling of ICWC (PhD T. Wauters)
0D ‘kinetic’ description of H2/He ICWC discharges
Data to be combined with data from RF models (e.g. TOMCAT, D. Van Eester) and plasma wall interaction codes
Wall reservoir modeling to simulate isotopic ratio change over
23D. Douai Recent results on Ion Cyclotron Wall conditioning 15 April 2010
TORE SUPRA
ICWC discharges investigated in TS, JET, AUG and TEXTOR
Recovery from disruptions demonstrated in TORE SUPRA, using pulsed He-ICWC
optimisation of pulsed ICWC discharges under study
He / D2-ICWC scenarios in divertor tokamaks in conditions similar to ITER half and full field operation AUG: BT=2,0 T and f=30MHz for on-axis =CH
+
JET: BT=3.3 T and 25 MHz for on-axis =CD+
Strong isotopic ratio exchange in H2 (or D2) ICWC discharges
However always 2 to 10 more retention than outgassing pulsed ICWC
In JET, ICWC discharges could reach the central column. The equivalent of 10~20 % of the short term retained H could be exchanged with D within 70 sec. D2-ICWC (p = 2.10-5 mbar, PRF,coupled = 250 kW, BV=30 mT) , with 1 H outgassed for 3 D retained
A large He retention during He containing ICWC discharges in JET and AUG AUG: known from He-GDC and lab experiments JET : reason ? presence of Be as bulk material for antenna protection limiters
Flux of CX neutrals too low to explain outgassing and retention quantitatively
Arcing traces on antenna straps Need for antenna dedicated to ICWC in TS.
Conclusion
24D. Douai Recent results on Ion Cyclotron Wall conditioning 15 April 2010
TORE SUPRA
TS: superconducting tokamak
-Analysis of Pulsed discharges data on going
-High P/N discharges
-Assess efficiency against different type of disruptions
-Role of CX neutrals (use of NPA) vs. low energy species (RFA)
-Project of dedicated antenna
JET : assessment of efficiency on JET with ILW (Be first wall + W divertor)
-Repeat reference session on isotopic exchange with ILW
-assess He as working gas for ICWC with ILWNo specific wall
“preloading” (or with ohmic shots)
Future plans