Rob Akers ST Workshop, PPPL, 20Rob Akers ST Workshop, PPPL, 20thth Nov 2002 Nov 2002

Neutral Beam Heating and Current Drive in MAST

This work was funded by the UK DTI and EURATOM. The NB injectors are on loan from ORNL and the NPA This work was funded by the UK DTI and EURATOM. The NB injectors are on loan from ORNL and the NPA from PPPL.from PPPL.

B. Lloyd 1), J-W. Ahn 2), L.C. Appel 1), E.R. Arends 3), K.B. Axon 1), R.J. Buttery 1), C. Byrom 4), P.G. Carolan 1), C. Challis 1), D. Ciric 1), N.J. Conway 1), M. Cox 1), G.F. Counsell 1), G. Cunningham 1), A.C. Darke 1), A. Dnestrovskij 5), J. Dowling 1), M.R. Dunstan 1), A.R. Field 1), S.J. Fielding 1), S. Gee 1), M.P. Gryaznevich 1), P. Helander 1), M. Hole 1), M.B. Hood 1), A. Kirk 1), I.P. Lehane 6), G.P. Maddison 1), S.J. Manhood 1), R. Martin 1), G.J. McArdle 1), K.G. McClements 1), M.A. McGrath 7), H. Meyer 1), A.W. Morris 1), S.K. Nielsen 8), M.P.S. Nightingale 1), A. Patel 1), T. Pinfold 1), M.N. Price 1), J. Qin 2), C. Ribeiro 1), C.M. Roach 1), D.C. Robinson 1), O. Sauter 9), V. Shevchenko 1), S. Shibaev, 1) K. Stammers 1), A. Sykes 1), A. Tabasso 1), D. Taylor 1), M.R. Tournianski 1), G. Turri 2), M. Valovic 1), G.M. Voss 1), M.J. Walsh 10), S.E.V. Warder 1), J.R. Watkins 1), H.R. Wilson 1), Y. Yang 11), S. You 2) and the MAST and NBI teams.

1) EURATOM/UKAEA Fusion Association, Culham Science Centre, Abingdon, Oxon, UK2) Imperial College of Science, Technology and Medicine, London SW7 2BZ, UK3) FOM Institut voor Plasmafysica Rijnhuizen, Nieuwegein, Netherlands 4) University of Manchester Institute of Science & Technology, Manchester, UK 5) Kurchatov Institute, Moscow, Russia6) University College, Cork , Ireland 7) University College, Dublin, Ireland 8) University of Aarhus, Denmark9) CRPP, Association Euratom – Confederation Suisse, EPFL, 1015 Lausanne, Switzerland10) Walsh Scientific Ltd, Culham Science Centre, Abingdon, OX14 3EB, UK11) Institute of Plasma Physics, Hefei, 230031, P.R. China

Introduction

In order to simulate NBI discharges on MAST:

a) Codes are being built/commissioned - LOCUST, TRANSP, SCoPE etc.

and

b) an advanced set of diagnostics are being developed/installed to provide input and cross checking with code predictions eg. 100-200Hz TS, 200 chord Zeff, Scanning NPA.

Codes are being commissioned on highly suprathermal discharges where the beamsproduce a large perturbation to the plasma.

The MAST NBI injectors

2 ORNL NBI injectors

Co/counter tangential injection, RT=0.7m

E0 : 40keV 70keV

Pb : 1.5MW 2.5MW

Species : H or D D

Typical Design

NBI orbits in MAST are extreme:

40keV D orbits in #6894 @300ms, Ip~350kA

The LOCUST model (developments)

Diagnostics - code inputs and outputs:

equilibrium: magnetics + EFIT (+ Fast CCD as cross check)e- density and temperature: 100-200 Hz NdYAG TS or 300pt Ruby TSe- density (EDGE): Dmodel (M.Tournianski)ion temperature: CXRS or Ti=Te

ion rotation: CXRS (or assumed ~100km/s in core)Zeff: 200 point Bremsstrahlung camera + NdYAG/Rubyion density: assume fully stripped C6+ + Zeff + NBI modelneutral density: D array or model (DOUBLE) (or both)neutrons: Range available, including blanked off NPA stripsfast neutral efflux: Scanning NPAPsep: Langmuir probes + bolometry + IR cameraPlasma purity: SPRED (survey)

Challenge is to model/combine all these as a self consistent picture of the plasma

Electron density and temperature

Electron density, temperature etc. are reconstructed from 100-200Hz Nd-YAG data (fortime evolving simulation) or from 300 pt. Ruby TS data for fine scale reconstruction inthe pseudo steady state.

Zeff data

• Plasma imaged @ f-11 on an interference filter (/d : 5213/4Å) using telecentric optics. Filter imaged onto a frame-transfer CCD which is binned to 128x128 - 256x256 pixel/chord array @200-100Hz with reasonable noise (<2%)

• Abel inverted ZEBRA profile compared with Zeff=1 bremsstrahlung from MPTS

First results from the scanning NPA show radial behaviour of ions close to primary injection energy in agreement with modelling

Counter injection has been tested, producing high performance plasmas

(assuming Ti=Te)

0.0 0.05 0.10 0.15 0.20 0.25

Time (s)

Counter-NBI (#6612) Co-NBI (#6536)

Preliminary neutral beam current drive studies indicate beam drivencurrent comparable with theoretical predictions (INB/Ip ~ 0.2-0.3)

• INBCD ~ 70-100kA, consistent with Vloop

• Pabs~50% @ Ip~0.35MA, ne~1x1019m-3

• Highly suprathermal discharge (80% fast ion energy)• Growth and decay of beta indicates fast ion slowing down well modelled

Low current, low ne~1x1019/m3 suprathermal discharge #6894

0.0 0.1 0.2 0.3 0.4 0.5 Time (s)

150ms

0.6 1.0 1.4R(m)

n19

7051

Ruby

NdYAG1

2

3

Early NBI (~2MW) to inhibit current penetration weak central shear (EFIT)

Ti

7051 250-255ms

v

Modest density (ne ~ 1 - 3 x 1019m-3) for good beam penetration andhigh momentum input per particle to maximise flow shear

C6+

ITB discharge shown in M.Gryaznevich’s talk on Monday

Suprathermal discharges with high rotation and broad current profiles are well modelled

Pabs ~ 40%

#7051

A note on confinement time

W=WEFIT-Wfast

Quasi Steady State discharge #6952 shows Ti>Te

• Absorbed power Pabs~100% @ Ip~0.8MA• Ti(sep) > Te(sep) indicated by probes• Ti(H) > Te(H) required for match to W• Small amount of D contamination of H-beam• HH ~ 1.0 for quasi steady state period

Quasi Steady State discharge #6762 - submitted to ITPA

Conclusions

• An advanced set of NBI/CD codes are being developed/deployed on MAST eg. LOCUST, TRANSP, SCoPE

• An advanced suite of diagnostics is now commissioned, with futher upgrades and additions planned for the near future, (first data taken for 100-200Hz Nd-YAG TS, 2D Zeff,

scanning NPA)

• LOCUST, developed to model the extreme fast ion orbits in START fits the majority ofdischarges extremely well, even at very low Ip and density where plasmas are highlysuprathermal (~80% fast ions) and losses are high

• First tests of counter NBI yield high performance, ELM free plasmas

• First tests of NBCD at low Ip, low ne show NBCD to be at the expected level

• Next step: fully commission TRANSP and SCoPE, assess importance of beam-beam collisions, to understand any differences between TRANSP and LOCUST

• Use these tools to target long operation of MAST through optimisation of NBCD and pressure driven currents and to validate/develop simulations of next step devices (STPP, CTF etc.)