Rob Akers ST Workshop, PPPL, 20th Nov 2002

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Rob Akers ST Workshop, PPPL, 20th Nov 2002
This work was funded by the UK DTI and EURATOM.
The NB injectors are on loan from ORNL and the
NPA from PPPL.
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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, UK 2) Imperial College of
Science, Technology and Medicine, London SW7 2BZ,
UK 3) FOM Institut voor Plasmafysica Rijnhuizen,
Nieuwegein, Netherlands 4) University of
Manchester Institute of Science Technology,
Manchester, UK 5) Kurchatov Institute, Moscow,
Russia 6) University College, Cork , Ireland 7)
University College, Dublin, Ireland 8)
University of Aarhus, Denmark 9) CRPP,
Association Euratom Confederation Suisse, EPFL,
1015 Lausanne, Switzerland 10) Walsh Scientific
Ltd, Culham Science Centre, Abingdon, OX14 3EB,
UK 11) Institute of Plasma Physics, Hefei,
230031, P.R. China
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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
beams produce a large perturbation to the plasma.
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The MAST NBI injectors
2 ORNL NBI injectors Co/counter tangential
injection, RT0.7m
Typical Design
E0 40keV 70keV Pb 1.5MW 2.5MW Species
H or D D
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NBI orbits in MAST are extreme
40keV D orbits in 6894 _at_300ms, Ip350kA
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The LOCUST model (developments)
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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 TS e- density
(EDGE) Da model (M.Tournianski) ion
temperature CXRS or TiTe ion rotation CXRS
(or assumed 100km/s in core) Zeff 200 point
Bremsstrahlung camera NdYAG/Ruby ion
density assume fully stripped C6 Zeff NBI
model neutral density Da array or model
(DOUBLE) (or both) neutrons Range available,
including blanked off NPA strips fast neutral
efflux Scanning NPA Psep Langmuir probes
bolometry IR camera Plasma purity SPRED
(survey)
Challenge is to model/combine all these as a
self consistent picture of the plasma
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Electron density and temperature
Electron density, temperature etc. are
reconstructed from 100-200Hz Nd-YAG data
(for time evolving simulation) or from 300 pt.
Ruby TS data for fine scale reconstruction in the
pseudo steady state.
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Zeff data

• Plasma imaged _at_ 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 _at_200-100Hz
  with reasonable noise (lt2)
• Abel inverted ZEBRA profile compared with Zeff1
  bremsstrahlung from MPTS

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First results from the scanning NPA show radial
behaviour of ions close to primary injection
energy in agreement with modelling
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Counter injection has been tested, producing high
performance plasmas
(assuming TiTe)
0.0 0.05
0.10 0.15
0.20 0.25
Time (s)
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Preliminary neutral beam current drive studies
indicate beam driven current comparable with
theoretical predictions (INB/Ip 0.2-0.3)
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Low current, low ne1x1019/m3 suprathermal
discharge 6894
0.0 0.1
0.2 0.3
0.4 0.5
Time (s)

• INBCD 70-100kA, consistent with Vloop
• Pabs50 _at_ Ip0.35MA, ne1x1019m-3
• Highly suprathermal discharge (80 fast ion
  energy)
• Growth and decay of beta indicates fast ion
  slowing down well modelled

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ITB discharge shown in M.Gryaznevichs talk on
Monday
7051
250-255ms
150ms
7051
3
Ti
n19
2
Ruby
C6
v?
NdYAG
1
0.6
1.0
1.4
R(m)
Early NBI (2MW) to inhibit current penetration ?
weak central shear (EFIT)
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Suprathermal discharges with high rotation and
broad current profiles are well modelled
7051
Pabs 40
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A note on confinement time
WWEFIT-Wfast
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Quasi Steady State discharge 6952 shows TigtTe

• Absorbed power Pabs100 _at_ Ip0.8MA
• Ti(sep) gt Te(sep) indicated by probes
• Ti(H) gt Te(H) required for match to W
• Small amount of D contamination of H-beam
• HH 1.0 for quasi steady state period

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Quasi Steady State discharge 6762 - submitted to
ITPA
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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 of
• discharges extremely well, even at very low Ip
  and density where plasmas are highly
• suprathermal (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