1 / 10

Internal transport barrier investigations in MAST

ITPA CDBM: ITB and Transport, St Petersburg, 2003. Internal transport barrier investigations in MAST. Presented by Martin Valovic for:-. A R Field, C Challis, P G Carolan, N J Conway, G Cunningham, H Meyer, M J Walsh and the MAST team. EURATOM/UKAEA Fusion Association, Culham Science Centre

uyen
Télécharger la présentation

Internal transport barrier investigations in MAST

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. ITPA CDBM: ITB and Transport, St Petersburg, 2003 Internal transport barrier investigations in MAST Presented by Martin Valovic for:- A R Field, C Challis, P G Carolan, N J Conway, G Cunningham, H Meyer, M J Walsh and the MAST team EURATOM/UKAEA Fusion Association, Culham Science Centre Abingdon, Oxon, OX14 3DB, UK • Introduction • Discharge scenario • Evidence for ITB • Transport simulations • Summary This work is funded jointly by the UK Department of Trade and Industry and EURATOM

  2. ITB Discharge Scenario • Aim for weak/reversed magnetic shear and high toroidal flow shear: • 4MA/s Ip ramp from initial 100 kA MC plasma • Early NBI heating, 2 MW • Low density, 1-21019 m-3 • Broad initial j(r) indicated by low Li ~ 0.6 • Significant NBI heating after 0.1 s due to • poor initial fast ion confinement

  3. ITB:- Ti, vi(C6+) and pi,e Profiles Ti and Vf profiles, from CXR C6+, showing large thermal gradient at high velocity shear. Electron and ion pressure profiles, showing steep gradients at position of high velocity shear.

  4. Measured Tiand Vi profile evolution in ITB discharge CXRS measurements of Ti and Vi on C6+ ions show steep Ti gradient coincides with high shear flow region.

  5. TRANSP modelling indicates reversed magnetic shear • Inputs to TRANSP • Te(r,t), ne(r,t) from Thomson scattering • TC6+(r,t), VC6+(r,t) from CXRS of C 6+ • EFIT determined boundary shape • Assumed Zeff profiles • Outputs • Ti (r,t), Vi (r,t) of fuel ions (deuterium) • neutron flux (compared with measurements) • Vloop , li , etc. • q(r,t) and j(r,t) • Some indications that ITB formation is associated with weak or reversed magnetic shear (e.g. in #7051, TRANSP suggests q  0 for extreme limits of Zeff ~ 1.5 to 3.0) but wider “causality” investigations and more detailed measurements are required; e.g. 200Hz TS and 200 chord Zeff now available)

  6. Criterion for presence of ITB • Velocity shear rate exceeding the turbulent growth rate:- • or, equivalently, (CEA criterion for presence of ITB):- ITB

  7. Preliminary Transport Simulations • A simple 1D ad hoc time dependent code which uses:- • Neo-classical thermal diffusivity: • Momentum diffusivity smaller by 3/2: • gives:- • Reasonable agreement with measured central C6+ temperature • and velocity (from CXRS) • Close coupling of D+ and C6+ toroidal flow

  8. Conclusions • Initial attempts at ITB formation on MAST have been successful. • Strongly sheared toroidal flow are accompanied by increases in pressure gradients. • More experiments are underway (e.g. density scans, co- and counter-NBI) with improved diagnostics (e.g. 200 Hz TS and 200 chord Zeff). • More in-depth tranport analyses are progressing (e.g. TRANSP).

  9. q r/a q-profile TRANSP predictions: sensitivity to Zeff

  10. Preliminary Transport Simulations using an ad hoc 1D code

More Related