Member of the Helmholtz Association Meike Clever | Institute of Energy Research – Plasma Physics | Association EURATOM – FZJ Graduiertenkolleg 1203 Dynamics of hot plasmas - Dynamik heißer Plasmen Hydrogen recycling and transport in the helical divertor of TEXTOR Mitgliederversammlung GRK1203, Bad Breisig - 27 to 28 October 2008

Meike Clever | Institute of Energy Research – Plasma Physics | Association EURATOM – FZJ15 October Dynamic Ergodic Divertor Control exhaust of particles and heat from the plasma Helical divertor structure unperturbed flux surfaces stochastisation of magnetic field DED

Meike Clever | Institute of Energy Research – Plasma Physics | Association EURATOM – FZJ15 October Helical Divertor (DED)Wendelstein7-AS from Y. Feng et al., Physics of island divertors as highlighted by the example of W7-AS, Nuclear Fusion, 2006, 46, Divertor target upstream downstream flux tube Divertor target Connection length Radial coordinate  Parallel, convective transport to the DED target  Effect similar to classical SOL Laminar flux tubes Island divertor Topological similarity

Meike Clever | Institute of Energy Research – Plasma Physics | Association EURATOM – FZJ15 October Low recycling Divertor regimes Attachment (Low recycling and high recycling regime) : momentum, energy and particles reach divertor target plates unhindered envisaged divertor regime for future fusion devices Tokamak Low recyclingHigh recyclingDetachment Low recyclingDetachment Stellarator DED ?? plasma density Detachment: strong reduction of momentum, energy and particle flux protects target material from high heat fluxes

Meike Clever | Institute of Energy Research – Plasma Physics | Association EURATOM – FZJ15 October Divertor regimes at high densities High recycling: plasma source localised at the target temperature gradient low temperatur at the target low physical sputtering Detachment: strong temperature drop momentum sink decreased ion flux to the target downstream upstream ionization target downstream upstream ionization target (mechanism at TEXTOR?)

Meike Clever | Institute of Energy Research – Plasma Physics | Association EURATOM – FZJ15 October Introduction 2The diagnostic 3Detachment in the helical divertor of the DED 4Conclusion and Outlook Overview

Meike Clever | Institute of Energy Research – Plasma Physics | Association EURATOM – FZJ15 October Top view of TEXTOR - diagnostics Digital camera system  exchangeable interference filters (H and C)  1 megapixel CCD chip  10 bits dynamic range  max. 33 frames/s

Meike Clever | Institute of Energy Research – Plasma Physics | Association EURATOM – FZJ15 October Introduction 2The diagnostic 3Detachment in the helical divertor of the DED 4Conclusion and Outlook Overview

Meike Clever | Institute of Energy Research – Plasma Physics | Association EURATOM – FZJ15 October Detachment in the helical divertor of the DED plasma core Limiter (without DED) H   (656  nm) last closed flux surface (LCFS)

Meike Clever | Institute of Energy Research – Plasma Physics | Association EURATOM – FZJ15 October Detachment in the helical divertor of the DED plasma core upstreamdownstream H   (656  nm) Helical divertor (DED)

Meike Clever | Institute of Energy Research – Plasma Physics | Association EURATOM – FZJ15 October Detachment in the helical divertor of the DED Migration of the ionisation front

Meike Clever | Institute of Energy Research – Plasma Physics | Association EURATOM – FZJ15 October Detachment in the helical divertor of the DED DED flat top density ramp Migration of the ionisation front

Meike Clever | Institute of Energy Research – Plasma Physics | Association EURATOM – FZJ15 October DED flat top Detachment in the helical divertor of the DED Migration of the ionisation front density ramp

Meike Clever | Institute of Energy Research – Plasma Physics | Association EURATOM – FZJ15 October DED flat top Detachment in the helical divertor of the DED Migration of the ionisation front density ramp

Meike Clever | Institute of Energy Research – Plasma Physics | Association EURATOM – FZJ15 October Detachment in the helical divertor of the DED DED flat top Migration of the ionisation front density ramp

Meike Clever | Institute of Energy Research – Plasma Physics | Association EURATOM – FZJ15 October Detachment in the helical divertor of the DED DED flat top Migration of the ionisation front density ramp

Meike Clever | Institute of Energy Research – Plasma Physics | Association EURATOM – FZJ15 October Detachment in the helical divertor of the DED DED flat top Migration of the ionisation front density ramp

Meike Clever | Institute of Energy Research – Plasma Physics | Association EURATOM – FZJ15 October Detachment in the helical divertor of the DED DED flat top Migration of the ionisation front density ramp

Meike Clever | Institute of Energy Research – Plasma Physics | Association EURATOM – FZJ15 October Detachment in the helical divertor of the DED DED flat top Migration of the ionisation front density ramp

Meike Clever | Institute of Energy Research – Plasma Physics | Association EURATOM – FZJ15 October Detachment in the helical divertor of the DED DED flat top Migration of the ionisation front density ramp

Meike Clever | Institute of Energy Research – Plasma Physics | Association EURATOM – FZJ15 October Detachment in the helical divertor of the DED DED flat top Migration of the ionisation front density ramp

Meike Clever | Institute of Energy Research – Plasma Physics | Association EURATOM – FZJ15 October Detachment in the helical divertor of the DED toroidaler Winkel  [°] Profile for intensity change in the strike points deconvolution poloidale Koordinate [mm]

Meike Clever | Institute of Energy Research – Plasma Physics | Association EURATOM – FZJ15 October Detachment in the helical divertor of the DED lower divertor integration Temporal evolution of H  photon flux ~ particle flux at target plates lower divertor upper divertor

Meike Clever | Institute of Energy Research – Plasma Physics | Association EURATOM – FZJ15 October Temporal evolution of the H  photon flux during the density ramp Detachment in the helical divertor of the DED inner strike point outer strike point Divertor (DED)Limiter (without DED)

Meike Clever | Institute of Energy Research – Plasma Physics | Association EURATOM – FZJ15 October Comparison to the island divertor Analogous results at W7-AS with EMC3/EIRENE code Comparative modeling of the observed effect at TEXTOR is running from Y. Feng et al, Nuclear Fusion, 2006, 46, (5)

Meike Clever | Institute of Energy Research – Plasma Physics | Association EURATOM – FZJ15 October Introduction 2The diagnostic 3Detachment in the helical divertor of the DED 4Conclusion and Outlook Overview

Meike Clever | Institute of Energy Research – Plasma Physics | Association EURATOM – FZJ15 October Conclusion and Outlook  Further comparison and analysis necessary High recycling ? Detachment mechanism ? Local plasma parameters (n e, T e ) from simultaneously taken images of Balmer lines H   (656  nm) H   (486  nm) H   (434  nm) Low recycling Detachment Stellarator DED ?Detachment plasma density Helical DED divertor Stellarator divertors ?

Meike Clever | Institute of Energy Research – Plasma Physics | Association EURATOM – FZJ15 October Outlook - Diagnostic under construction Simultaneous image recording with four different filters Four CCD cameras (two of them intensified) Filter wheels for neutral density filters interference filters Optical fiber for high resolution spectrometer Simultaneous DED target IR image recording heat flux measurement

Meike Clever | Institute of Energy Research – Plasma Physics | Association EURATOM – FZJ15 October Thank you for your attention! and to S. Brezinsek, J.W. Coenen, M. W. Jakubowski, M. Lehnen, A. Pospieszczyk, O. Schmitz, B. Schweer, H. Stoschus, B. Unterberg, U. Samm and the TEXTOR team

Meike Clever | Institute of Energy Research – Plasma Physics | Association EURATOM – FZJ15 October Appendix

Meike Clever | Institute of Energy Research – Plasma Physics | Association EURATOM – FZJ15 October Detachment in the helical divertor of the DED Expectation: Detachment at comparably high T e, because of large momentum losses due to opposing particle flows inside the flux tubes at the target High recycling difficult, because of open ergodic divertor sources cannot be localised at the target

Meike Clever | Institute of Energy Research – Plasma Physics | Association EURATOM – FZJ15 October Analogy to divertors in stellarator Wendelstein7-AS: Island divertor

Meike Clever | Institute of Energy Research – Plasma Physics | Association EURATOM – FZJ15 October Analogy to divertors in stellarators Large Helical Device (LHD)  helical divertor and island divertor

Meike Clever | Institute of Energy Research – Plasma Physics | Association EURATOM – FZJ15 October Sheath limited (or linear/ low recycling) regime parallel heat conduction almost no temperature gradient high target temperatures (>> 5 eV) large mean free path for neutrals downstream density linearly follows upstream density almost all power entering upstream reaches the target Divertor regimes downstream upstream ionization target

Meike Clever | Institute of Energy Research – Plasma Physics | Association EURATOM – FZJ15 October High recycling (or conduction limited) regime rising downstream density mean free path of neutrals decreases near target re-ionization increased recycling nonlinear connection to upstream density upstream and target temperature decrease (> 5 eV) parallel heat conduction decreases Divertor regimes downstream upstream ionization target

Meike Clever | Institute of Energy Research – Plasma Physics | Association EURATOM – FZJ15 October Detachment regime further increase of upstream density reduction of ion flux to the target T and n e decrease sharply towards the target (T < 1.5 eV) Divertor regimes downstream upstream ionization target

Meike Clever | Institute of Energy Research – Plasma Physics | Association EURATOM – FZJ15 October Diagnostic method - Passive spectroscopy Flux of atomic hydrogen from Balmer line emission local electron density and temperature needed Temperature [eV] Recombination Ionisation Charge Exchange h ¾ ¢ v i[ m ¡ 3 s ¡ 1 ] 5 eV

Meike Clever | Institute of Energy Research – Plasma Physics | Association EURATOM – FZJ15 October Diagnostic method Passive hydrogen spectroscopy Atoms: Balmer series - emission of radiation for the electronic transition to lower level n = 2 (H  = 656 nm, H  = 486 nm, H  = 434 nm,...) Molecules: Fulcher-  band ( nm) Measurement at DIII-D

Meike Clever | Institute of Energy Research – Plasma Physics | Association EURATOM – FZJ15 October Comparison to the island divertor Analogous results at W7-AS