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Hydrocarbon spectroscopy on EU tokamaks

Hydrocarbon spectroscopy on EU tokamaks. TF-E. S. Brezinsek on behalf of the EU task force for Plasma-Wall Interaction presented by V. Phillips. TEXTOR: Photon efficiencies for different types of hydrocarbons in ionising plasmas

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Hydrocarbon spectroscopy on EU tokamaks

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  1. Hydrocarbon spectroscopy on EU tokamaks TF-E S. Brezinsek on behalf of the EU task force for Plasma-Wall Interaction presented by V. Phillips TEXTOR: Photon efficiencies for different types of hydrocarbons in ionising plasmas HYDKIN: Measured and calculated photon efficiencies in different devices AUG: Chemical erosion and photon efficiencies under detached plasma conditions JET: Chemical erosion yielded in higher hydrocarbons

  2. TEXTOR– Photon Efficiencies for Hydrocarbons: CD4 Aim: Measure D/XB values without contamination from deposited and re-eroded hydrocarbons. Comparison with HYDKIN and ERO calculations CD A-X band (CD from CD4) D/XBExp. =36 D/XBHYDKIN=46 D/XBERO=32

  3. TEXTOR: Effective Photon Efficiencies for CxHy, CxDy CH A-X band (Gerö band) C2 d-a band (Swan band) Brezinsek et al. PSI 2006 CxHy in D plasmas: Te=35 eV, ne=2.2*1018m-3 at the emission location CxDy in H plasmas: Te=45 eV, ne=1.8*1018m-3 at the emission location

  4. TEXTOR: CD+ Observed in Hot Edge Plasmas => CD+ identified in TEXTOR plasmas => break-up via molecular ions important • TEXTOR benchmark experiment with CD4: • 20 % of theoretically expected CI 909.5 nm per C observed • 50 % of theoretically expected CII at 426.7 nm per C+ observed • 20 % of theoretically expected Dg per H observed

  5. HYDKIN: CH+ vs. CH in the Hydrocarbon chain CH4+ CH3+ CH2+ CH+ C+ C2+ Part of the dissociation chain (CH4): CH4 CH3 CH2 CH C Reaction kinetic analysis with HYDKIN (Reiter 2006) for CH4 Cold divertor plasma (AUG, JET) Hot limiter plasma (TEXTOR) CH+ CH CH CH+ Te=45 eV Te=5 eV

  6. HYDKIN: Effective Photon Efficiencies for Methane Comparison of measured effective photon efficiencies with HYDKIN calculations (const. plasma, no deposition, no transport) Brezinsek et al. PSI 2006 • Janev-Reiter database is reliable in the range between 5 eV and 100 eV • Detailed comparison with the aid of erosion and deposition models necessary

  7. AUG: Hydrocarbon Injection in Detached Plasmas • L-mode discharges with outer divertor detachment • Injection of CH4 and C2H4 in the SOL, Separatrix and PFR in the volume: Te=1.2 eV, ne=3*1020m-3 at the target (separatrix): Te=2.3 eV, ne=4*1018m-3

  8. AUG: Photon Efficiencies in Detached Plasmas Intrinsic CD A-X spectrum --- attached plasma --- Intrinsic CD A-X spectrum with strong BD contamination --- detached plasma --- CH A-X spectrum from injection and CD A-X intrinsic background --- detached plasma --- CH A-X spectrum from injection and CD A-X intrinsic background --- attached plasma --- Brezinsek et al. PFCM 2006

  9. AUG: Erosion Yields in Detached Plasmas Measured D/XB values are higher than in attached plasmas and higher than predictions with HYDKIN! D/XB for CH from CH4: 18+-/7 D/XB for CH from C2H4: 47 +/-19 D/XB for C2 fromC2H4: 407 +/-134 Decrease of CH and C2 light much stronger than increase of D/XB => Significant decrease of the hydrocarbon flux in detachment Erosion yield at the separatrix for detached conditions: Ychem=3.2*10-2 (ion flux only) Ychem=2.9*10-3 (atom and ion flux) Erosion yield in line with Roth-formula: Ychem=2.5*10-3 (atom and ion flux) Reduced influx is largely compensated by lower plasma outflux. => Consideration of neutral outflux to the target is important!

  10. JET: CxHy Contribution to the Erosion Yield Circumferential injection into the attached outer divertor: i) Discharge with C2H4 injection ii) Discharge with H2 injection Nearly identical local plasma conditions Assumption: symmetric and homogenous injection Brezinsek et al. EPS 2005

  11. JET: CxHy Contribution to the Erosion Yield • Most reliable value for Ychem is achieved • when the strike point is at GIM10 • Toroidal inhomogeneity of gas injection • module included (=> information from • tracer experiments) • Bypass in the outer divertor considered! • Photon efficiencies and erosion yield lowered in comparison to first analysis (EPS 2005) • D/XB for C2 Swan band from C2H4 about 75 • Ychem associated to higher hydrocarbons about 0.6% Brezinsek et al. PSI 2006

  12. Summary • TEXTOR: • Photon efficiencies for different hydrocarbons • Information about hydrocarbon catabolism • Detection of CH+ in the hot edge plasma • AUG: • Photon efficiencies for CH in detached plasma conditions • Hydrocarbon particle flux reduction in detached plasmas • Neutral flux to the target important for yield determination • JET: • Circumferential injection in the outer divertor • Erosion which yielded in C2Hy lower than previously deduced • HYDKIN: • Janev & Reiter data base reliable for ionising conditions • Normalised D/XB values deduced in different machines • and compared with HYDKIN

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