# Presentation: 076293

## 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.**

## B. Lloyd 1), J-W. Ahn 2), L.C. Appel 1), E.R. Arends 3), K.B. Axon 1), R.J. Buttery 1), 

**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**

## 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.

## 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 TS
- e- density (EDGE):			Dmodel (M.Tournianski)
- ion temperature:			CXRS or Ti=Te
- 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:			D 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

## 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.

## Zeff data

- 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)

## Preliminary neutral beam current drive studies indicate beam driven

**Preliminary neutral beam current drive studies indicate beam driven**
**current comparable with theoretical predictions (I****NB****/I****p**** ~ 0.2-0.3)**

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

** ****I****NBCD**** ~ 70-100kA, consistent with V****loop**
** ****P****abs****~50% @ Ip~0.35MA, n****e****~1x10****19****m****-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)

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

**150ms**

**0.6**

**1.0**

**1.4**

**R(m)**

**n****19**

**7051**

**Ruby**

**NdYAG**

**1**

**2**

**3**

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

- Ti

**7051**

**250-255ms**

- v

- C6+

## Pabs ~ 40%

- 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

- Quasi Steady State discharge #6952 shows Ti>Te

** ****Absorbed power P****abs****~100% @ Ip~0.8MA**
** ****T****i****(sep) > T****e****(sep) indicated by probes**
** ****T****i****(H) > T****e****(H) required for match to W**
** ****Small amount of D contamination of H-beam**
** ****H****H**** ~ 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 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
- pressure driven currents and to validate/develop simulations of next step devices (STPP, CTF etc.)