Trilateral Euregio Cluster TEC Institut für Plasmaphysik Assoziation 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 Plasmaphysik Assoziation 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 nm Pulse 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 nm Pulse 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: ms Spot size : 4-20 mm 2 Power density: kW/cm 2 Status of work : laser induced desorption TEC

Laser-Spot ( a-C:D on Graphite) Mean power Density: 95 kW/cm 2 SIMS: 96% Reduction of D-Inventory, Higher P, t Mass 4 Closed valves 180 nm a-CH layer on graphite TEC Thermal desorption: qualification in Lab experiments

Graphite EK98 target exposed to TEXTOR plasma, LDS measured 45 nm (2.2x10 17 H/cm 2 ), ±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 cm49 cm50 cm Application in TEXTOR with H  Spectroscopy Radial Position r / cm FWHM: 3.3 cm FWHM: 5.3 cmFWHM: 2.0 cm 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 Plasma He-Ne Laser Amplifiers Telescope P with Q-switch t=20ns Q=20J mirror TEC

r = 48 cm S spot = 0.3 cm 2 TEC Trilateral Euregio Cluster Institut für Plasmaphysik Assoziation EURATOM-Forschungszentrum Jülich Tungsten test limiter with 140 nm a-C:D coating Tungsten substrate Second laser shot r = 50 cm S spot = 0.16 cm 2 First laser shot CII(678.4nm) CII(658nm) H  (656nm) CII(589nm) intensity / a.u. wavelength / nm r = 48 cm S spot = 0.4 cm 2 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

TEC Summary 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)