Member of the Helmholtz Association OS2010| Institute of Energy Research–Plasma Physics | Association EURATOM – FZJ Spectroscopy on laser released particles from plasma facing materials in a tokamak B. Schweer, A. Huber, V. Philipps, M. Zlobinski, N. Gierse and U. Samm Institut für Energieforschung – Plasmaphysik, Forschungszentrum Jülich, Association EURATOM-FZJ, Trilateral Euregio Cluster, D Jülich, Germany

OPEN SYSTEMS 2010| Institute of Energy Research – Plasma Physics | Association EURATOM – FZJJuly 6th, 2010No 2 Introduction Wall characterisation with laser based methods Application in tokamaks (ITER) outline

OPEN SYSTEMS 2010| Institute of Energy Research – Plasma Physics | Association EURATOM – FZJJuly 6th, 2010No 3 Introduction 1.Retention of hydrogen isotopes in bulk material (accumulation effects?) 2.Development of mixed layers from eroded wall materials with -co-deposition of hydrogen isotopes -Formation of dust, flakes? ITER operation Proposed wall materials:  main chamber: Beryllium  Baffles:Tungsten  Divertor: CFC (H-H operation) Physical and chemical erosion of carbon Tungsten lamellae (D-T operation)? Physical erosion

OPEN SYSTEMS 2010| Institute of Energy Research – Plasma Physics | Association EURATOM – FZJJuly 6th, 2010No 4 measurement of tritium retention measurement of erosion and deposition Limit for allowed operation is 700 g T inventory (10 17 Bq)(technical regulation)technicalregulation T retention from global fuel gas balance (measurement) Strong inhomogeneous distribution of H isotopes in re-deposited material (plasma facing components, remote areas, dust, flakes) Local characterisation of ITER wall (pre-tritium phase) Identification of major deposition areas and material composition Results should support the decision to start tritium removal techniques, e. g. change of plasma configuration- strike points wall heating (surfaces) chemical reaction-oxidation, cleaning discharges remote access-local heating of surface layer (flashlamp, laser) exchange of components Motivation: Characterisation (monitoring) of wall conditions

OPEN SYSTEMS 2010| Institute of Energy Research – Plasma Physics | Association EURATOM – FZJJuly 6th, 2010No 5 In-situ diagnostics preferred: diagnostic developments: Laser induced desorption spectroscopy (LIDS) in-situ with main plasma pre-tritium and tritium phase Laser induced ablation spectroscopy(LIAS) in-situ with main plasma pre-tritium and tritium phase Laser induced breakdown spectroscopy(LIBS) in-situ without main plasma pre-tritium and tritium phase Investigation of physics requirements and principle feasibility Technical design and construction for ITER -remote operation -reliability -radiation constrains -large structures Laser based diagnostics Single laser shot analysis!

OPEN SYSTEMS 2010| Institute of Energy Research – Plasma Physics | Association EURATOM – FZJJuly 6th, 2010No 6 Knowledge of molecules decay process: (dissociation, excitation, ionisation) D 2  D* + D*  2D + + 2e  h (ionisation, dissociation, excitation) D 2  D e  D + + D* + e  2D + + 2e  h Measurement of absolute H  intensities Knowledge of plasma parameter and conversion factors (S/XB) Laser induced desorption spectroscopy LIDS First wall bulk Mixed layer (a:C-H) Main plasma H 2, (H n C m ) Laser In-situ diagnostic: 1.Fast heating and desorption release of hydrogen isotopes (H 2, hydrocarbon) HH HH HH detector 2.Excitation by plasma (ionisation, dissociation, excitation) observation of line radiation

OPEN SYSTEMS 2010| Institute of Energy Research – Plasma Physics | Association EURATOM – FZJJuly 6th, 2010No 7 Heating source Nd:YAG laser: L = 1064 nm, P pulse  20 kW, (3 Hz) t pulse  20ms, E L  60 J, P ave  300 W (5 Hz) A spot =0.29 cm 2 (d=6 mm) Laser induced desorption spectroscopy LIDS necessary conditions for desorption: laser power density (single pulse):P A  70 kW/cm 2  95% of hydrogen pulse duration: t p  5 ms, A spot  A laser necessary surface temperature T s  1800 K (for graphite) Penetration depth  z  100 µmT  900 K Sensitivity (inventory)N  /cm 2 observation system Absolute calibrated detector: CCD camera or Photodiode Optical transmission Interference filter parameter Edge plasma parameter (T e, n e ) Conversion factors S/XB High resolution spectrometer Discrimination H isotopes

OPEN SYSTEMS 2010| Institute of Energy Research – Plasma Physics | Association EURATOM – FZJJuly 6th, 2010No 8 system Laser outside concrete shielding Fibre length 35 m Core diameter 400 µm Fast camera: 7000 frames/s Standard: 500 frames/s high resolution spectrom. H  /D  Experimental arrangement at TEXTOR

OPEN SYSTEMS 2010| Institute of Energy Research – Plasma Physics | Association EURATOM – FZJJuly 6th, 2010No 9 LIDS on graphite (roof limiter) Camera frame frequency 1500 Hz

OPEN SYSTEMS 2010| Institute of Energy Research – Plasma Physics | Association EURATOM – FZJJuly 6th, 2010No 10 First wall bulk Mixed layer Main plasma Laser induced ablation spectroscopy LIAS High power laser H,W, Be, CLaser plasma In-situ diagnostic with plasma: 1.Fast heating and ablation destruction of surface (plasma) fast recombination (W, Be, cluster, H isotopes) Knowledge of spectroscopic and atomic data of released species in plasma Knowledge of plasma parameter Qualitative measurement Quantitative measurement 2. Excitation by plasma (ionisation, dissociation, excitation) simultaneous observation of (absolute) line radiation HH detectors Dichroic mirrors W I Be I W IBe I HH

OPEN SYSTEMS 2010| Institute of Energy Research – Plasma Physics | Association EURATOM – FZJJuly 6th, 2010No 11 Heating source: (e.g.) Nd:YAG laser (Q-switch): Laser = 1064 nm, (512nm, 353 nm) P pulse  300 MW, (Q switch) t pulse = 8 ns, E Laser  2.5 J, P av  25 W (10 Hz) A spot =3 cm 2 (d=10 mm) (w/o fibre) Laser induced ablation spectroscopy LIAS necessary conditions for ablation: laser power density (single pulse):P A  100 MW/cm 2 pulse duration: t p  10 ns, Laser ind. plasma temperature T p  1-10 eV Penetration depth  z  1 µm observation system Absolute calibrated detector: CCD camera or diode Optical transmission (UV to IR) Interference filter parameter Edge plasma parameter (T e, n e ) Conversion factors S/XB Wide range high resolution spectrometer

OPEN SYSTEMS 2010| Institute of Energy Research – Plasma Physics | Association EURATOM – FZJJuly 6th, 2010No 12 Laser induced ablation 0.4 µm / laser shot

OPEN SYSTEMS 2010| Institute of Energy Research – Plasma Physics | Association EURATOM – FZJJuly 6th, 2010No 13

OPEN SYSTEMS 2010| Institute of Energy Research – Plasma Physics | Association EURATOM – FZJJuly 6th, 2010No 14 Laser-induced ablation spectroscopy on TEXTOR Tungsten test limiter with 140 nm a-C:D coating Ruby laser t laser =10 ns P=25 MW/cm 2 E=0.25 J/cm 2 Threshold for ablation of layers is much lower

OPEN SYSTEMS 2010| Institute of Energy Research – Plasma Physics | Association EURATOM – FZJJuly 6th, 2010No 15 Investigation of ablation source on carbon bulk material Laboratory experiment: Laser spot

OPEN SYSTEMS 2010| Institute of Energy Research – Plasma Physics | Association EURATOM – FZJJuly 6th, 2010No 16 Time of flight measurement on fine grain carbon

OPEN SYSTEMS 2010| Institute of Energy Research – Plasma Physics | Association EURATOM – FZJJuly 6th, 2010No 17 First wall bulk Mixed layer Laser induced breakdown spectroscopy LIBS Knowledge of spectroscopic and atomic data of released species in plasma Knowledge of laser plasma parameter Qualitative measurement Quantitative measurement High power laser H,W, Be, CLaser plasma In-situ diagnostic w/o plasma: 1.Fast heating and ablation destruction of surface (formation of plasma) (W, Be, cluster, H isotopes) HH detectors Dichroic mirrors W I Be I 2. Laser induced plasma (fast recombination, excitation) no background radiation simultaneous observation of (absolute) line radiation W I HH Be I

OPEN SYSTEMS 2010| Institute of Energy Research – Plasma Physics | Association EURATOM – FZJJuly 6th, 2010No 18 LIBS spectra on graphite Reproducibility? Calibration?

OPEN SYSTEMS 2010| Institute of Energy Research – Plasma Physics | Association EURATOM – FZJJuly 6th, 2010No 19 Studies on technical implementation of LIDS, LIAS and LIBS in ITER

OPEN SYSTEMS 2010| Institute of Energy Research – Plasma Physics | Association EURATOM – FZJJuly 6th, 2010No 20 optical arrangement for port plug based diagnostic Laser beam (ns, ms) Observation endoscope For LIDS, LIAS and LIBS Focussing mirror with hole Rotation axis? First wall Hole in first wall

OPEN SYSTEMS 2010| Institute of Energy Research – Plasma Physics | Association EURATOM – FZJJuly 6th, 2010No 21 Sensitivity study for LIDS at ITER Assumptions: Laser spot size:A =1cm 2 H density:n H =3  /cm 2 nm Layer thickness:  l =100nm Pulse duration:  t =1ms Maxwellian source: T =0.2 eV Flux  spot =3  /s Equatorial view

OPEN SYSTEMS 2010| Institute of Energy Research – Plasma Physics | Association EURATOM – FZJJuly 6th, 2010No 22 Modelling studies on LIDS and LIAS during running ITER shots

OPEN SYSTEMS 2010| Institute of Energy Research – Plasma Physics | Association EURATOM – FZJJuly 6th, 2010No 23 ITER like optical system at TEXTOR Laser beam: Focal length:2.5 m Observation:Focal length:0.2 m Scanning area:10 cm x 10 cm Laser beam Line radiation X-Y tilting Tangential view LIDS LIAS LIBS

OPEN SYSTEMS 2010| Institute of Energy Research – Plasma Physics | Association EURATOM – FZJJuly 6th, 2010No 24 Summary Laser based diagnostic for ITER: LIDS: in-situ method with plasma for Tritium retention in the divertor and main chamber (poloidal distribution in equatorial view) Promising results at TEXTOR LIAS:in-situ method with plasma for first wall characterisation in the divertor and main chamber (equatorial view) Needs more investigation of the source (bulk / layer) dependence on pulse duration and exposure time LIBS:in-situ method without plasma for first wall characterisation in the divertor and main chamber Needs more investigation of the source (bulk / layer) dependence on pulse duration and exposure time parameter of laser plasma must be known (dynamic) ITER:coaxial injection and observation feasible modelling of line integrated signals in edge plasma requested

OPEN SYSTEMS 2010| Institute of Energy Research – Plasma Physics | Association EURATOM – FZJJuly 6th, 2010No 25

OPEN SYSTEMS 2010| Institute of Energy Research – Plasma Physics | Association EURATOM – FZJJuly 6th, 2010No Radius r / mm calculated radial temperature after 1 ms x 80 kW/cm Spot Radius 2 Temperature T/ o C t = pulse length D = diffusion coefficient K = heat conductivity  = specific density c = specific heat 1-dim heat conduction sufficient for spot centre temperature calculation: Microscopic image of a laser-desorbed spot on an a-C:D layer on graphite

OPEN SYSTEMS 2010| Institute of Energy Research – Plasma Physics | Association EURATOM – FZJJuly 6th, 2010No 27 Surface temperature (graphite) Laser power density