Deuterium retention in Tore Supra long discharges

1E. Tsitrone 20th IAEA Vilamoura 1-6/11/2004

EuratomDeuterium retention in Tore Supra long discharges

• Interpreting the particle balance

• Particle retention during long discharges

• Particle recovery (after shot, glows, disruptions)

• Experimental results

E. Tsitrone, C. Brosset, J. Bucalossi, B. Pégourié, T. Loarer, P. Roubin2, Y. Corre, E. Dufour, A. Géraud, C. Grisolia , A. Grosman, J. Gunn , J. Hogan3 , C. Lowry, R. Mitteau , V. Philips4,

D. Reiter4, J. Roth5, M. Rubel6, R. Schneider7, M. Warrier7

Association Euratom-CEA, CEA Cadarache, CEA-DSM-DRFC, F-13108 Saint Paul-lez-Durance, France2 : LPIIM, UMR 6633, Université de Provence, Centre Saint-Jérôme13 397 Marseille cedex 203 : Fusion Energy Division, ORNL, Oak Ridge, TN 37831-8072 USA4 : Institut für Plasmaphysik, FZ Jülich, Euratom Association, D-52425 Jülich, Germany5 : Max Planck Institute für Plasmaphysik, Euratom Association, Boltzmannstr. 2, D-85748 Garching Germany6 : Alfven Laboratory, Royal Institute of Technology, Association Euratom VR, 100 44 Stockholm, Sweden7 : Max Planck Institute für Plasmaphysik, Euratom Association, Teilinst. Greifswald, Wendelsteinstrasse 1, D-17491 Greifswald Germany


EuratomTore Supra : the CIEL configuration

• Long pulse : LH driven discharge at Vloop ~ 0, low plasma current/density low density hot edge plasma (Te ~ 100 eV at the LCFS)

Toroidal pump limiter (TPL)

Bumpers

Outboard movable limiter

• 15 m2 of carbon plasma facing components• Active cooling : stationary PFC temperaturefrom 120°C (cooling loop) up to 250°C on the limiter for long pulses

Plasma loaded zones

Shadowed zones

CCD imaging of the TPL

• Active pumping : neutralisers below TPL


Euratom

Phase 1 Phase 2

Particle retention in long discharges

No saturation of in vessel retention after 15 minutes of cumulated plasma time

• Phase 2Constant retention rate (= 50% of injected flux)No saturation after 6 minutes

• Identical shot to shot behaviour

• Phase 1 (~ 100 s)Decreasing retention rate

• In vessel inventory shot duration in phase 2(Imax = 8 1022 D for 6 minutes)


Euratom

Phase 1 Phase 2

Retention phase 1

x 1021

Particle recovery after shot

• Recovery > plasma content : the wall releases particles

x 1022

• Recovery correlated to retention in phase 1 : transient retention mechanism

• Small fraction recovered after shot

~ 100 s


EuratomParticle recovery after glow discharge and disruptions

Recovery after He glow discharge (6 hours) : 1.5 - 2 1022 D < Imax

• Independent of the quantity trapped during the day of experiment

0.2 0.4 0.6 0.8 1 1.2 1.4 1.60

20

40

60

80

100

120

Plasma current before disruption (MA)

Par

ticle

exh

aust

(P

a.m

3)

Tore Supra - Disruptions 2002-2004

0.2 0.4 0.6 0.8 1 1.2 1.4 1.60.2 0.4 0.6 0.8 1 1.2 1.4 1.60

20

40

60

80

100

120

0

20

40

60

80

100

120


Par

ticle

exh

aust

(P

a.m

3)


Recovery after disruption : up to 5 1022 D < Imax

• Large scatter at given Ip : machine history dependent ?(highest exhaust in start up phase)

• Threshold in Ip :

• Ip < 0.8 MA : ~ after shot recovery• Ip > 0.8 MA : increase with Ip dissipated energy high enough to heat D rich deposited layers [D. Whyte, PSI 2004]


EuratomSample analysis : D content

Outboard limiter

Cold deposits (~ 120 °C)D/C ~ 10 %ND ~ 1022 at /m2 / m * S * d

TPL

Neutraliser finger

Hot deposits (> 500°C)D/C ~ 1 %ND ~ 1021 at/m2 * S

[C. Brosset, PSI 2004]

TPL deposits analysis still in progressCold deposits in shadowed areas D reservoir

Several ms

Shadowed

< 1 m

Plasma facing

Several ms

Carbon deposits

Net deposition zoneNet erosion zone (main plasma interaction area)

Net deposition zones


EuratomInterpreting the particle balance

BUT : does not explain shot to shot behaviour unless very strong diffusion takes place

Phase 1

Progressive saturation of bombarded surfaces (D+, D0) until CDmax reached

• Implantation D C D+, D0

dimp< 0.1 m

Carbon

D+

D0

D2+

D2

TPL

Bumpers

[E. Tsitrone, PSI 2004]

Saturation time : from ~ 1s (TPL) to ~ 100 s (bumpers)


Euratom

Phase 1

Interpreting the particle balance

• Outgassing after shot ~ phase 1 duration ( ~ 100s) : ok with filling / emptying the porosity reservoir

Good candidate for phase 1 BUT : extrapolation from lab to tokamak environment (temperature)

• TS deposited layers : 100 times more porous than original CFC [P. Roubin, PSI 2004]

• Filling the CFC porosityD2, D0

Adsorption

M. Warrier et al., Contrib. Plasma Phys. 44, No. 1-3, (2004)

• Adsorption : weak bond ( chemical bond) ok for transient mechanism

• Extrapolation from lab exp (77 K) : 1022 D/g deposits 0.5 g enough to account for phase 1

5 1021 D



Phase 1 + 2

• ok with Zeff, ok with low net erosion on TPL (high local redeposition), ok with layers growing rate

1020 C/s1.5 1020 CD4/s

Distant redeposition (TPL shadowed areas, neutralisers, outboard limiter …)

6 1020 C/s (phys. + self)

1.5 1020 CD4/s (chem.)

Erosion

5 1020 C6+/s

Local redeposition

Preliminary estimates of carbon erosion sources • physical + chemical sputtering by D+ and D0

• self sputtering by Cn+ (assumed 5% C in D+ flux)

• Codeposition :

Carbon deposits

C, D

CxDy

physical sputtering

chemical sputtering

carbon balance roughly coherent



Phase 1 + 2

• If D/C = 0.1 : need 2 1021 C/s of net redeposition : high erosion/redeposition on TPL ( > 100 m on 4 m2): not observed

No coherence between D retention rate / D/C ratio / C erosion/redeposition

D rich film created during the discharge subsequently depleted in D (glows, disruptions) ?

Hard to explain the retention rate in phase 2 with codeposition alone

• 1/3 of produced CD4 trapped : but high D/C ratio film : not observed

2 1020 D/s

1020 C/s1.5 1020 CD4/s

Distant redeposition (TPL shadowed areas, neutralisers, outboard limiter …)6 1020 C/s

1.5 1020 CD4/s

Erosion

5 1020 C6+/s

Local redeposition

• Codeposition : D balance


Euratom Summary

Phase 2Phase 1

• D implantation in C : progressive saturation but not transient

• D adsorption in porosity : good candidate, but to be assessed in tokamak environment

• Codeposition of D and C :Can hardly explain the retention rate in phase 2

• D content sample analysis : D mainly in cold deposits in shadowed areas (120 °C)

Missing D not found yet but still a lot to investigate (TPL deposits, pumping ducts …)

• D recovery (He glow discharge, disruptions) < in vessel inventory accumulated in a single long discharge

• D retention : no wall saturation after 15 minutes in high Te / low ne edge plasma

Transient retention : recovered after shot

Permanent retention : NOT recovered after shot


Euratom


EuratomTore Supra : well equipped for particle balance

• Gas injection : manometers

• Active pumping : 10 neutralisers with turbo-molecular pumps equipped with 20 pressure gauges (1 in vertical port, 1 at the pump) + 2 Penning gauges (D2/He) + mass spectrometer• 2 pressure gauges in the chamber (equatorial ports)• pressure gauges in primary exhaust system

• Systematic calibration procedure : calibrated gas injection in the chamber with/without pumps activated

D+

to pumps

dNp/dt = inj – pump – in vessel


EuratomEffect of active pumping

Pumping on

Active pumping on Tore Supra : no effect on dynamic wall retention but offset on gas injection

Pumping off

Same wall inventory

Shifted gas injection


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0 50 100 150 200 250 300 350 400 450 5000

1

2

3

4

0 50 100 150 200 250 300 350 400 450 5000

50

100

150

200

250

300

350

LH power (MW)

Injected flux (Pa.m3/s)Extracted Flux (Pa.m3/s)

Gas Puffing

Vessel Inventory

TPL exhaust

Vessel ExhaustPlasma Content x100

Inve

nto

ries

(P

a.m

3 )

s

Time (s)

Shot 32299

Particle balance sensitive to LH power loss



Euratom

Shot 33067

T (°C) before/after disruption (20 ms)

Disruption heats deposited layers

Net erosion zone (main plasma interaction area)

Thickest deposition zone (shadowed/plasma area)

Moderate deposition zone (plasma interaction area)

T > 220 °CPlasma loaded zones

Shadowed zones

CCD imaging of the TPL


Euratom

T°C #33067 (t-20ms) T #33067 (disruption)

IR shows cold deposits


EuratomD inventory in the machine

Estimated D inventory in the machine : From analysed samples : ~ 5 1022 D (80% in cold deposits)From non analysed samples (TPL surface) : ~ 4 1022 D (most of it in TPL shadowed zones)Total : ~ 9 1022 D

Estimated D inventory from particle balance integrated over a campaign: From averaged net retention rates : ~ 1.5 1024 DGlow discharge : ~ 4 1023 DDisruptions : ~ 3 1023 DTotal : ~ 8 1023 D

No firm conclusion can be drawn on D balance

BUT : surface/depth of layers difficult to assess, samples still to be analysed

BUT : retention rate scenario dependent, not all disruptions recorded, glow D2 not accounted, cleaning discharges …










minimize the retention rate optimize the recovery techniques

ITER in vessel T inventory limit : (retention rate - recovery rate) dt < 350 g


Euratom

Phase 1 Phase 2

Particle retention in long discharges


No saturation of in vessel retention after 15 minutes of cumulated plasma time

• Phase 2Constant retention rate (= 50% of injected flux)No saturation after 6 minutes

• Identical shot to shot behaviour

• Phase 1 (~ 100 s)Decreasing retention rate

• In vessel inventory shot duration in phase 2(Imax = 81022 D for 6 minutes)


EuratomSample analysis : D content

Outboard limiter


TPL

Neutraliser finger



TPL deposits analysis still in progressCold deposits in shadowed areas D reservoir

Several ms

Shadowed

< 1 m

Plasma facing

Several ms

Carbon deposits

Net deposition zone Net erosion zone (main plasma interaction area)

Moderate deposition zone (plasma interaction area)

Thickest deposition zone (shadowed area)

D content in analysed samples < D inventory over campaign



Phase 1 + 2

• Codeposition :

Carbon deposits

C, D

CxDy

Physical sputtering (C/s)

Chem. sputtering (CD4/s)

Self sputtering (C/s)

D+ (1022 /s) 3 1020 1.25 1020 D0 (4 1021 /s) 4.5 1019 2.75 1019

C 6 + (5 1020 /s) 2.6 1020

Estimates of carbon erosion sources

• ok with Zeff, ok with high redeposition (low net erosion on TPL), ok with layers growing rate carbon balance roughly coherent 1020 C/s

1.5 1020 CD4/s

Distant redeposition (TPL shadowed areas, neutralisers, outboard limiter …)6 1020 C/s

1.5 1020 CD4/s

Erosion

5 1020 C6+/s

Local redeposition

• C source underestimated : no synergy D+/D0, no localised hot Tsurf, no LH accelerated e-


EuratomSample analysis : D content Net erosion zone

Plasma facing

< 1 m

Carbon substrate

Neutraliser finger

Outboard limiter


TPL



TPL deposits analysis still in progressCold deposits in shadowed areas

Several ms

Shadowed

hot deposits

cold deposits< 1 m

Plasma facing

Several ms

Carbon deposits

Net deposition zone


Euratom

Phase 1

Interpreting the particle balance

68

1019

2

4

68

1020

2

S (s

-1)

500450400350

t (s)

0.001

2

3

4

56

0.01

2

P (Pa)

68

1019

2

4

68

1020

2

S (s

-1)

500450400350

t (s)

0.001

2

3

4

56

0.01

2

P (Pa)68

1019

2

4

68

1020

2

S (s

-1)

500450400350

t (s)

0.001

2

3

4

56

0.01

2

P (Pa)

68

1019

2

4

68

1020

2

S (s

-1)

500450400350

t (s)

0.001

2

3

4

56

0.01

2

P (Pa)pvessel

Soutgas

dpvessel/dt = Soutgas – Seff pvessel

• Recovery ~ phase 1 duration : ok with filling / emptying the porosity reservoir

Good candidate for phase 1 BUT : extrapolation from lab to tokamak environment

(temperature, pressure, incident particles)

• Filling the CFC porosity

• TS deposited layers : 100 times more porous than virgin CFC [P. Roubin, PSI 2004]

D2, D0

Adsorption

M. Warrier et al., Contrib. Plasma Phys. 44, No. 1-3, (2004)

• Adsorption : weak bond ( chemical bond) ok for transient mechanism

• Extrapolation from lab exp : 1022 D/g deposits 0.5 g enough to account for phase 1

5 1021 D










minimize the retention rate optimize the recovery techniques

ITER in vessel T inventory limit : (retention rate - recovery rate) dt < 360 g


EuratomParticle recovery after glow discharge and disruptions

Recovery after He glow discharge (6 hours) : 1.5 - 2 1022 D < Imax

• Independent of the quantity trapped during the day of experiment • ~ desaturation of 15 m2 of carbon implanted with D for 300 eV incident He

0.2 0.4 0.6 0.8 1 1.2 1.4 1.60

20

40

60

80

100

120


Par

ticle

exh

aust

(P

a.m

3)


0.2 0.4 0.6 0.8 1 1.2 1.4 1.60.2 0.4 0.6 0.8 1 1.2 1.4 1.60

20

40

60

80

100

120

0

20

40

60

80

100

120


Par

ticle

exh

aust

(P

a.m

3)


Recovery after disruption : up to 5 1022 D < Imax

• Large scatter at given Ip : machine history dependent ?(highest exhaust in start up phase)

• Threshold in Ip :

• Ip < 0.8 MA : ~ after shot recovery• Ip > 0.8 MA : increase with Ip dissipated energy high enough to outgas deposited layers [D. Whyte, PSI 2004]



BUT : does not explain shot to shot behaviour unless very strong diffusion takes place

Phase 1

Progressive saturation of bombarded surfaces (D+, D0) at CDmax = f(Einc, Tsurf )

• Implantation D C D+, D0

dimp< 0.1 m

Carbon

D+

D0

D2+

D2

TPL

Bumpers

[E. Tsitrone, PSI 2004]

Saturation time : from ~ 1s (TPL) to ~ 100 s (bumpers)

Implantation of D0 in bumpers

Deuterium retention in Tore Supra long discharges

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