tore supra 1 d. douai recent results on ion cyclotron wall conditioning 15 april 2010 recent results...

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


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


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


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 ?


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


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


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


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


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


-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


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


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


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


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


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


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


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


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


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


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


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


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?)


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)


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


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


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


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

tore supra 1 d. douai recent results on ion cyclotron wall conditioning 15 april 2010 recent results...

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