Trilateral Euregio Cluster

TEC

Institut für PlasmaphysikAssoziation EURATOM-Forschungszentrum Jülich

Development of in situ diagnostic for fuel retention, material deposition and dust detection

in ITER

A. Huber (project leader), B. Schweer, F. Irrek S. Brezinsek, V. Philipps, G. Sergienko,

Ph. Mertens, W. Biel

Trilateral Euregio Cluster

TEC

Institut für PlasmaphysikAssoziation EURATOM-Forschungszentrum Jülich

Urgent need to develop in situ diagnostic for fuel retention, material deposition and dust production generation, recognised by ITER (design change request Nr: )

Proper gas balance should be a main method to measure fuel retention in a global way

No further information from post mortem tile analysis

Development of in situ laser based methods for fuel retention, material deposition and dust production to

• support gas balance and enable (some) space resolution

• determine amount and composition of material deposition (correlation with gas balance)

• allow dust detection near deposition dominated areas

Idea: develop a single laser and mirror based system for all 4 methods which can scan some part of inner

wall/divertor area in ITER

Methods

During discharges

Smooth (≈ 1 ms) laser desorption with spectroscopy to measure fuel retention

Laser ablation with spectroscopy to measure material deposition

Rayleigh / Mie scattering for dust monitoring

In-between discharges

Laser-induced breakdown spectroscopy (LIBS) for material deposition and composition

TEC

Strategy: a Nd:YAG laser operating with/without Q-switch

Operating modes

Laser-induced desorption

(LID):

Laser without Q-switch

at 1064 or 532 nm;

Pulse duration: up to 3 ms;

Total energy: up to 120 J.

Rayleigh/Mie scattering:Laser without Q-switch

at 1064 or 532 nmPulse duration:

up to 10 ms

Total energy: up to 120 J.

Laser-induced Ablation (LIA):

Laser with Q-switch at 532 nm;

Pulse duration:

up to 10 ns;

Total energy: 5 J.

Laser-induced Breakdown Spectroscopy (LIBS):

Laser with Q-switch at 532 nmPulse duration: up to 10 ns;

Total energy: 5 J.Operation without plasma

TEC

Movable target holder

Quadrupol MS

Fast IR linear array

camera

Fiber coupling

TEXTOR Tokamak

Laboratory Device

YAG Laser

Limiter lock system 1

Optical diagnostic D (H/D ratio) D, Dγ, CD CII, CIII

Pulse duration: 0.1-20ms

Spot size : 4-20 mm2

Power density: 20-120 kW/cm2

Status of work : laser induced desorption TEC

Laser-Spot

( a-C:D on Graphite)

0.0 0.4 0.80

1000

2000

Te

mp

era

ture

T /

°C

Radius r / mm

calculatedradial Temperatureafter

1 ms x 80 kW/cm2

SpotRadius

Mean power Density: 95 kW/cm2

SIMS: 96% Reduction of D-Inventory,

Hig

her

P,

t

0.0 0.5 1.0 1.5

0.0

0.5

1.0

1.5

0

500

1000

1500

Temperature

2nd Shot

1st Shot

Num

ber

of R

elea

sed

Mol

ecul

es /

10

15

t / ms

Tem

pera

ture

T /

°C

Mass 4

Closed valves

180 nm a-CH layer on graphiteTECThermal desorption: qualification in Lab experiments

Graphite EK98 target exposed to TEXTOR plasma, LDS measured

45 nm (2.2x1017 H/cm2), ±30%

Laser-desorption of pre-coated samples for calibration

TEC

LID has been qualified in TEXTOR to measure in situ and shot by shot

fuel retention in C materials ( PSI contribution)

Application in TEXTOR with H Spectroscopy

Sample surface at 48 cm 49 cm 50 cm

Application in TEXTOR with H Spectroscopy

46

47

48

49

50Rad

ial P

ositi

on r

/ cm

Rad

ial P

ositi

on r

/ cm

Rad

ial P

ositi

on r

/ cm

5130 50405060

FWHM: 3.3 cm FWHM: 5.3 cmFWHM: 2.0 cm

46

47

48

49

50

46

47

48

49

50

Quantification of H light needs large optical view

Good agreement with S/XB literature values for r < 49 at TEXTOR

LCFS

Plasma

Experimental setup: limiter lock III

Ablation: qualification in TEXTOR

ALT- II Limiter,r=46.0cm

Plasma

Spectrometer

2D spectroscopyFilters:D (656.3 nm)CII (426.7 nm)WI (400.8 nm)

C-W Twin Limiter can be rotated

Plasma

He-Ne Laser

Amplifiers

Telescope

Pwith Q-switcht=20ns Q=20J

mirror

TEC

r = 48 cmSspot= 0.3 cm2

TEC

Trilateral Euregio Cluster

Institut für PlasmaphysikAssoziation EURATOM-Forschungszentrum Jülich

Tungsten test limiter with

140 nm a-C:D coating

Tungsten substrate

Second laser shotr = 50 cmSspot= 0.16 cm2First laser shot

580 600 620 640 660 6800

100

200

300

400

500

600

CII(678.4nm)

CII(658nm)H(656nm)CII(589nm)

inte

nsity

/ a

.u.

wavelength / nm

r = 48 cmSspot= 0.4 cm2

Ruby Laser (20 J max) in 20

ns time scale

Ablation: qualification in TEXTOR

larger laser spot

reduced spot, same power

Ti melting

TEXTOR test limiter (Ti), coated

by Textor plasma

For C-layers deposited on W and Ti, an operational window exits for complete C layer ablation (one laser shot) without ablation of substrate

TEC

TECSummary

Laser fuel desorption and material ablation with spectroscopic detection in TEXTOR standard plasmas has been sufficiently qualified in TEXTOR

Next steps: Conceptual design of a system for possible ITER application (2008)

Procurement of a laser with ≈ 120 J for ≈ 10 ms. Manufacture of beam line and detection (2009)

Testing of the system in the laboratory (2010)

Installation and testing of the system in a fusion plasma 2011 (e.g. TEXTOR)