TFE Th Loarer – SEWG – 12 September 2007 1 Euratom Th Loarer V Philipps 2, J Bucalossi 1, D Brennan 3, J Brzozowski 4, N Balshaw 3, R Clarke 3, G Esser.

TFE

Th Loarer – SEWG – 12 September 2007 1

Euratom

Th Loarer

V Philipps2, J Bucalossi1, D Brennan3, J Brzozowski4, N Balshaw3, R Clarke3, G Esser2, M Freisinger2, S Grünhagen5, J Hobirk6, S Knipe3, A Kreter2,

Ph Morgan3, R Stagg3, L Worth3 and JET EFDA contributors*

Fuel retention in L and H-mode experiments in JET

1 - Association EURATOM-CEA, DSM-DRFC, CEA Cadarache, 13108 St Paul lez Durance, France.2 - IPP, Forschungszentrum Juelich, D-52425 Juelich, Germany3 - Euratom-UKAEA Association, Fusion Culham Science Centre, Abingdon, OX14 3EA, UK.4 - EURATOM/VR Association - Fusion Plasma Physics, EES, KTH, Stockholm, Sweden5 - FZ Karlsruhe, Postfach 3640, D-76021 Karlsruhe, Germany6 - Max-Planck IPP-EURATOM Association, Garching, Germany*See Appendix of M.L.Watkins et al., Fusion Energy Conference 2006 (Proc. 21st Int. Conf.

Chengdu) IAEA, (2006)

Outline

Introduction

Evaluation of fuel retention at JET

Short and long term retention; associated particle fluxes

Recycling flux and ELMs

Recovery between discharges

Summary

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Th Loarer – SEWG – 12 September 2007 2

Euratom Introduction

- Evaluation of hydrogenic retention in present tokamaks is of high

priority to establish a database for ITER (400 sec ~ 7min…10-20 sec

today).

- A retention of 10% of the T injected would lead to the limit of 350g

(working guideline for initial operation) in “only” 35 pulses.

- Fuel retention experiments in JET studied in a series of repetitive and

identical discharges to minimise the contribution from previous

experiments (history), achieve a high accuracy (~1.2%)

- Reference database under C-wall conditions completed before Be/W

Evaluation of Long term fuel retention with different materials

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Euratom

physics: material erosion, migration & fuel retention

• QMB measurements

• Spectroscopy

• Gas balance measurements

• Deposition probes

• 13C migration

• Post mortem tile analysis

D,T

Mechanisms for fuel retention

Two basic mechanisms for

Long term fuel retention

Deep Implantation, Diffusion/Migration,

Trapping

C, Be C, Be, D ,T

In JET (and other carbon wall devices ) Codeposition dominates retention (also expected for Be wall conditions, JET ILW, ITER)

Codeposition

Short term retention (Adsorption: dynamic retention)

Recovered by outgasing in between discharges

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Calibrated Particle Source

(Gas, NBI…)

Divertor cryo-pumps

Retention (wall)

Long & Short Term

Procedure on JETRegeneration of the cryopump before and after the session (1.2%) Repeat the same discharge (~10) w/o conditioning between pulses

Plasma

Injection = Pumped + Short Term Ret + Long Term Ret

Total Recovered from Cryo regeneration:Pumped + outgassing in between pulses ~800s (Short Term Ret)

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Euratom Gas Balance

From cryo-pump regeneration (~1%) and calibrated gas injection

Evaluation of the pumped flux

- During the plasma

- Between pulses

t (s)0 10 100 1000

Plasma

During plasmainj>pump

Retention>0

Short & Long term

Between pulsesinj=0

pump= OutgasingRetention<0

Short term retention only(dynamic retention)

Evaluation of Short and Long term retentionInjection = Long Term Ret + Short Term Ret + Pumped flux

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Euratom Type III ELMs

# 68619

Ip/BT=2.0MA/2.4T,

6.0MW ICRH “only”

13 repetitive pulses

Also in L mode and Type I ELMy H-mode

Reproducible plasma

conditions in all shots

Type III ELMs53-70 s

PTOT ~ 6.0MW

Density

Fueling 5.8 1021Ds-1

D (in & out)

Div Pressure

Vessel pressure

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Euratom

L-mode

Total Injected: 1.349 1024 D (4.511g)

Total Recovered (Pumped flux and outgassing in between pulses): 1.208 1024 D (3.946g)

Long Term Retention: 0.141 1024 D (0.472g) Heating Phase (81 s) Injection Long Term Ret

~1.8x1022Ds-1 1.74x1021Ds-1 ~10%

L-mode, Type I & III ELMy H-mode

Evaluation of Short and Long term retention during the pulse

Heating Phase Injection Long Term RetType III 221s ~0.6x1022Ds-1 1.31x1021 Ds-1 ~20%

Type I 32 s ~1.7x1022Ds-1 2.83x1021Ds-1 ~17%

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Euratom Particle fluxes: L mode

Drop of retention not only due to decrease of inj

Ip=2.0MA, BT=2.4T1.2MW ICRH “only”

@15 sec,

Ret~6.5x1021Ds-1

LongRet=1.74x1021Ds-1 (25%)

ShortRet=4.8x1021Ds-1 (75%)

@25 sec,

Ret~4.65x1021Ds-1

LongRet=1.74x1021Ds-1 (35%)

ShortRet=2.91x1021Ds-1 (65%)

Injection

Pumped flux

Retention

Long term Ret

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Euratom During the pulse: H mode Type III

Ip=2.0MA, BT=2.4T

~5MW ICRH “only”ITER_like conf.

@16 sec, Ret=53%

Ret~6.3x1021Ds-1

LongRet=1.3x1021Ds-1 (33%)

ShortRet=2.0x1021Ds-1 (66%)

@28 sec, Ret=43%

Ret~2.35x1021Ds-1

LongRet=1.3x1021Ds-1 (55%)

ShortRet=1.05x1021Ds-1 (45%)

Injection

Pumped flux

Retention

Long term Ret

Lower gas rate (1/3) but codeposition becomes dominant

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Euratom Particle fluxes: H mode Type I

From L mode to Type I ELM H-mode Increase of long term retention- with the recycling flux- with ELMs Energy

Ip=2.0MA, BT=2.4T

13MW NBI+ICRH ELM Energy~150kJ

@16 sec,

Ret~5.2x1021Ds-1

LongRet=2.8x1021Ds-1 (54%)

ShortRet=2.4x1021Ds-1 (46%)

@20 sec,

Ret~2.9x1021Ds-1

LongRet=2.8x1021Ds-1 (97%)

ShortRet=0.1x1021Ds-1 (3%)

Injection

Pumped flux

Retention

Long Term Ret

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Strong increase of the recycling flux in Type I ELMy H-modeSame behavior observed with CIII

Recycling flux: D signals

D Inner leg

D Outer leg

D Horizontal viewType IType IIIL mode

- L mode and Type III Similar recycling (D ) In, Out and Horizontal.

- No significant variation on the Outer leg region (“small” ELMs~150kJ).

-Strong increase of recycling flux (D) when moving to Type I ELMy H-mode

- Same behavior on the Horizontal view as on the inner leg.

Type IType IIIL mode

CIII Horizontal view

CIII Inner leg

CIII Outer leg

Higher recycling and ELM Enhanced carbon erosion and transport leading to stronger carbon deposition and fuel codeposition

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Integrated Hα and CIII horizontal light (L-mode, Type III and Type I ELMs)

The slope for Type I ELMy H-mode show enhanced recycling and total carbon source.

Integrated particle fluxes

H α

CIII

Type I ELMs

Type III ELMs

L mode

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Recovery in between pulses

• Small fraction recovered > plasma content ~ 0.5x1022D (70m3, <ne>~5-6 1019m-3)

• Except for disruptions, this amount is ~constant and independent of Ip, BT, ne, Pin, inj, Wdia (plasma scenario)

• Independent of inventory accumulated during the pulse and previous pulses

Within a factor of ~2 the recovery is constant in the range 1-3x1022DNo major contribution on the overall retention

6

5

4

3

2

1

0

Rec

over

ed a

fter p

ulse

(x

1022

D)

6543210

Total injected (x 1023

D)

Type III Type I L mode

6

5

4

3

2

1

0

Rec

over

ed a

fter p

ulse

(x

1022

D)

6543210

Total Injected (x 1023

D)

Type III Type I L mode High Ip (Type I ELMs) Mixed L mode, Type I & Type III

Short term retention

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Euratom Summary

- Repetitive pulses on JET for fuel retention analysis (accuracy ~1.2%)Evaluation of both short and long term retention

Confirm the strong concerns about fuel retention in C tokamak ITER with mixed material (C, Be, W)Burning Phase Injection Long Term Ret 400s ~ 5x1022Ts-1 ?

- In all the cases, the recovery in between pulses corresponds to a weak contribution in the overall fuel retention (short term retention)

Heating Phase Injection Long Term RetL mode 81s ~1.8x1022Ds-1 1.74x1021 Ds-1 ~10%

Type III 221s ~0.6x1022Ds-1 1.31x1021 Ds-1 ~20%

Type I 32 s ~1.7x1022Ds-1 2.83x1021Ds-1 ~17%

- Increase of long term retention- with the recycling flux- with ELMs Energy

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Euratom

Slides in reserve

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Euratom ELM induced C deposition

QMB1 (inner): Deposition per ELM vs. ELM energy

- Increased deposition due to thermal decomposition of co-deposited layers - Enhanced carbon erosion (Recycling and ELM energy) and transport

leading to stronger carbon deposition and fuel codeposition

Fit formula:y = 1012 * x * exp(x/165)

C d

epo

siti

on

per

EL

M [

ato

ms/

cm2 ]

WELM [kJ]0 100 200 300 400 500

1013

1014

1015

1016

"Area" term "Thermal" term

1

3

4 6

7

8

LBSRP

QM

B 1

QM

B 5

B field configuration

A.Kreter, H.G.Esser

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Euratom

Injection

(integral:1.8 x 1023 D-atoms)

Divertor pumping

Wall pumping

Long term retention (codeposition)

2 x 1021 D/s

Dynamic wall retention (decrease in 10 sec by about 50%)

3.9 x 1021

2.2 x 1021

Integrated wall pumping 3 x 1022

Measured long term outgassing (800s)

2.85 x 1022

Example: particle balance in 70534 during steady state phase

Long and short term retention

V Philipps

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Euratom

1. Campaign averaged retention about 5 times smaller due to effects of long term outgassing, thermal release from subsequent plasma

operation, GDC, disruptions (reasonable)

Codeposition

DC

C, D

Local C-erosion and redeposition does not contribute much to retention (similar D content of eroded and deposited layers)

Needed: long range transport from net erosion to deposition areas

main chamber to divertor

outer strike zone to PFR, inner divertor ,..

freshly deposited C-layers are D-rich (analysis after about 2h)

Further reduction by long term outgassing (reduction by about a factor of 2 between 2h and 24h ) and subsequent plasma operation

Discussion