Presented by: Mikhail Tournianski, for the MAST team Overview of recent results and plans on MAST This work was jointly funded by the UK Engineering &

Presented by:Mikhail Tournianski, for the MAST team

Overview of recent results and plans on MAST

This work was jointly funded by the UK Engineering & Physical Sciences Research Council and Euratom

MAST Parameters

Plasma cross-section and Ip comparable to ASDEX-U & DIII-D

Open divertor, up-down symmetric - upgraded 2004 Flexible configuration and adaptable fuelling systems

2.6

Performance optimisation and plasma control Confinement and transport Neutral Beam Current Drive Plasma exhaust Non solenoid start up

Plans and future upgrades to MAST

Focus and Plans

Address key ITER physics issues

Explore long-term potential of the ST

Address key ITER physics issues

Explore long-term potential of the ST



Overview of recent results on MAST

Error field correction coils

a set of four error field coils have been installed on MAST wired with opposite coils in series to give a dominantly n=1 field coils have been used both for locked mode scaling experiments and for intrinsic error field correction

Error field induced mode locking is a concern for ITER can be partially corrected using an external set of EF coils

Locked mode scaling

16.036.111.069.017.01.121 cylTeBB qBnT

16.036.111.069.017.01.121 cylTeBB qBnT

AaRnB

Be

t

)/(21

Aspect ratio comparison

]3.0,3.0[Based on 2004 DIII-D data:

Similar to those from large aspect ratio tokamaks

Error field correction error field correction expands the MAST operational space up to half density than attainable without EF correction

based on linear CCD camera with a D bandpass filter

controller is a standard PC running real-time Linux Abel-inverted to yield an estimate of the plasma radius measures outer midplane radius at 1kHz rate a better alternative to magnetics

Real time optical feedback

raw data

filtered data

filtered maxinversion max

outboard

pixel number

pix

el v

alu

e




Energy confinement in MAST approximately agree with the IPB98(y,2) scaling.

Confinement studies

Confinement studies

Strong interplay:

3 1 0.77*/( )EB

3 0 0.58*/( )EB

For gyro-Bohm scaling with degradation as in IPB98(y,2)):

For gyro-Bohm with independence:

MAST data significantly extend international database in beta (by factor 2.5)and inverse aspect ratio (= a/R) by factor of 2.2 and introduce a powerful constraint on dimensionless scaling laws

Comparison of matched MAST/DIII-D discharges support gyro-Bohm scalingand confirm dependence(Valovic & Petty, ITPA 2005)

M. Valovic etal, Nucl.Fusion 45 (2005) 942

Ip ~750 kABT ~0.6T<ne> ~3x1019m-3

Spectrometer coupled to 224 chords 64 toroidal chords on each NBI 32 passive toroidal chords 64 poloidal chords (32 32 on/off-beam) being commissioned

New enhanced CXRS (R~Li)

Detailed electron and ion temperature and density distributions in edge and internal transport barriers

Co- ITB

Counter- ITB

in early counter-NBI campaigns in MAST an electron ITB could be clearly seen but apparently not so for the ions (limited spatial resolution and weak signals).

ion barrier was seen using new enhanced CX diagnostic with R~Li

H-mode is one of the ITER base line scenarios PL-H is difficult to control

instead change drsep by plasma vertical movement lead to L-H transition switch

H-mode control on MAST

)(2072.07.0

9.07.020

7.0 AFZ

SnBP effHL

)(2072.07.0

9.07.020

7.0 AFZ

SnBP effHL

H-mode control is one of the key

Issues for the future experiments

Scaling doesn't cover all physics: drsep plays a key role in MAST




Classical fast ion confinement in MAST

Larmor orbit corrected Monte Carlo tracker (TRANSP), and the full gyro orbit treatment in (LOCUST). Advanced plasma diagnostics

- 300pt TS, 50Hz multi pt TS

- Zeff prof, BES(NBI),edge n0

Compare with NPA results Multi chord NPA data(edge , radial) in both L and H-modes Classical behaviour of fast ions reinforced confidence in heating and NBCD modelling

DND LSND USND

NBI NBI NBI

#13419, 320ms #13458, 320ms #13459, 320ms

NBCD studies : Off axis NBCD

Consider that ion born at the top or bottom of the orbit B is in opposite directions for USND and LSND angle between VNBI & B differ

trapped/passing balance changes due to NBI deposition effect specific to ST (B ~ B)

U-LSND – different NBCD efficiency

Large B in STs results in in a much different CD efficiencies in the two cases: upper and lower SNDs

U-LSND : Different CD efficiency predicted

-30 -20 -10 0 10 20 300.0

0.5

1.0

1.5

USNDLSND

li

0

100

200

300

EFIT SXR

Ohmic

Upper-low SNDs (L-mode, 280-300ms)

qaxis

=1 (ms)

0.0

0.5

1.0

Zmag

(cm)

T0

e (keV)

similar ne and Te

and plasma shapeLSND: q=1 appearance delay in both SXR data and EFIT data

li is much lower

in LSND

U/L SND comparison can be effective tool for experimental observations of off axis CD in STs

Off axis heating and CD on MAST

full modelling is challenging

( mid-plane diagnostics) and ongoing significant heating with off axis NBI (similar to on axis) NBCD of ~25% in low density (ne(0) ~1.5 10-19 m-3 MAST

IBS is negligible (low ne)

plasmas (TRANSP, LOCUST) significant conservation of volt/sec plans to repeat with higher PNBI

10-19

100 200 300 400 5000

1

2

3

4 MAST #11420

LH

E s

ign

al,

mW

Frequency, MHz

0.255 s 0.285 s 0.290 s

EBW studies on MAST

0.0 0.1 0.2 0.30

1

012

0

1

0

1

LH

, a.u

.

Time, s

124 MHz 134 MHz 142 MHz

<n

el>

, 1020

m-2

Plasma Density

a.u

. D

P, (

MW

) RF Power

Conversion of ECR into EBW is key importance for heating&CD Initial tests of O-X-B scheme (60GHz) LH probe (loop & L shape antennas) 76-545MHz LH waves provide valuable diagnostic of theory studies estimate coupling to EBW of at least 50%




ELM spatial structure (experiment)

Groundbreaking work exploiting the MAST geometry Filament-like structures exist during ELMs and some types of disruptions In ELMs the filaments are generated on a 100 s timescale, rotate with the outboard edge of the plasma and accelerate out from the outboard side.

ELM spatial structure(experiment+theory)

Image simulation of the expected structure with q95=4 and n=10

Filaments are consistent with the structures expected from the theory of the non-linear evolution of ballooning modes [Wilson and Cowley]

The effect of rotation - edge velocity shear

Using a box-car technique and averaging over several ELMs

Edge velocity shear greatly reduced at ELM peak

one of the possible loss mechanism involves great reduction in the edge velocity shear pressure grads can’t be sustained without velocity shire and plasma goes into deep L-mode Experimentally observed by the box-car technique

The importance of these filaments is that they can provide toroidally and poloidally localised heat fluxes to plasma facing components

Filaments as a pre-cursor to other disruptions

Visible images of single (n=1) filaments observed prior to some disruptions

evidence for these filaments

IR images of the interaction of filaments with vessel components

Heat load onPF coil

Heat load onPF coil

Heat load on

edge of beam dump

DIV camera

wide angle telecentric collection lense system good spatial coverage + narrow bandpass filters

2 cameras, programmable, 1 Mega-pixel visible CCD, 48+ Hz, electronic shutter (~ 100 s integration)

remote filter changers (D, D, C, He, Ar, …)

compact/modular/portable

UPPER DIVERTOR

D (750 s integration)CIII (465 nm) 13808

CII (514 nm)




Alternative start-up schemes

compatible with future ST design Double-null merging (DNM) involves breakdown at a quadrupole null between pairs of poloidal coils in upper and lower divertor Modelling predicts merging of plasma rings as current in coils ramped to zero

t=15ms Ip = 150 kA t=21ms Ip = 250 kA t=45ms Ip = 450 kA

t=60ms Ip = 600 kAt=75ms Ip = 600 kA

M.Gryaznevich

these proceedings

Plasma ring formation and merging clearly seen on centre column magnetic array Over 340kA plasma driven for >50ms solenoid was physically disconnected Hot (500eV) and dense plasma achieved Good target for NBI or RF current drive

DNM - Non-solenoid start-up




Neutral beam systems- higher power, longer pulse, improved reliability- 2 x 2.5MW for 5s capability

Ongoing modifications to MAST

Actively cooled calorimeter (gate in closed position)

Residual Ion DumpsNew JET-style PINI

Upcoming diagnostic upgrades

Divertor camera Spinning mirror for angular scan of EBW emission and proof of principle edge q-profile measurements 28GHz(150kW) EBW start up CD (~150kA(modelling)) CNPA (IPP) Edge Thomson scattering TAE antenna 64 chord poloidal CX system RGB camera, Gundestrup Probe etc.

Heating upgrade (10 MW, long pulse):

4 JET PINIs for 10 MW, 5 s

Off-axis NBCD capability

EBW CD, ~ 20 GHz, ~ 2 MW

New centre stack (higher Bt and Vs)

Pre-chilled,

Pumped divertor (density control):

- Closed configuration

- 2 100,000 L/s cryo-pumps

- CFC tiles required (temp rise ~ 1050°C after 4s at full power)

- Space to test materials and “pebble” divertor Modified poloidal field coils

Vertical stability at high elongation

Strike point control

Improved diagnostics, e.g. turbulence, q(r)

Key elements of proposed MAST upgrades

Proposed Divertor Upgrade

Additional PF coilsCryo-pump

Baffle

On-axis, counter-PINI

Jackable on/off-axis co-PINI

Double box: 2 co-PINIson- and off-axis

Investigating bold options for NBI current profile control

Flexible system 4 PINIs, up to 10 MW (1 counter- and 3 co-current)

Off-axis NBCD optimised with 2 off-axis co- and 2 on-axis co/counter PINIs

MAST Upgrades: Proposed NBI Systems

Optimal 4-PINI configuration gives 1.05 MA NI-CD with q0 > 1.5

800

600

400

200

0

0 1 2 3 4 5 6

Config. 1Config. 2Config. 3Config. 4

Time (seconds)Time [s]

Beam

dri

ven

curr

ent

,kA

Configuration:

# off on ctr INI [MA]

1 2 2 - 1.2

2 1 2 1 0.8

3 2 1 1 1.05

4 1 3 - 1.0

Ip = 1.2 MA, Bt = 0.64 T

q0 = 1.7, = 2.5, -1 = 1.43

Ti,e (0) = 3 keV

<Ti,e> = 1.35 keV

MAST Upgrades: more 1MA INI expected

TRANSP q profile simulations with 4 PINI operation

MAST Upgrades: Current profile control

q=1

Normalised ()

14

Config. 1Config. 2Config. 3Config. 4

0.2 0.4 0.6 0.8 1.0

12

10

8

6

4

2

0

r/a

Safety factor (4 sec)

q(r)

Configuration:

# off on ctr INI [MA]

1 2 2 - 1.2

2 1 2 1 0.8

3 2 1 1 1.05

4 1 3 - 1.0

Ip = 1.2 MA, Bt = 0.64 T

q0 = 1.7, = 2.5, -1 = 1.43

Ti,e (0) = 3 keV

<Ti,e> = 1.35 keV

0 0.2 0.4 0.6 0.8 1

14

12

10

8

6

4

2

0

J-W. Ahn 2), R.J. Akers 1), F.Alladio 11), L.C. Appel 1), D. Applegate 1), K.B. Axon 1), Y. Baranov 1), C. Brickley 1), C. Bunting 1), R.J. Buttery 1), 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. Darke 1), A. Dnestrovskij 3), J. Dowling 1), B. Dudson 4), M.R. Dunstan 1), A.R. Field 1), S. Gee 1), M.P. Gryaznevich 1), D. Howell 1), P. Helander 1), T.C. Hender 1), M. Hole 1), N. Joiner 2), D. Keeling 1), A. Kirk 1), I.P. Lehane 5), B. Lloyd 1), F. Lott 2), G.P. Maddison 1), S.J. Manhood 1), R. Martin 1), G.J. McArdle 1), K.G. McClements 1), H. Meyer 1), A.W. Morris 1), M. Nelson 6), M. R. O'Brien 1), A. Patel 1), T. Pinfold 1), J Preinhaelter 7), M.N. Price 1), C.M. Roach 1), V. Rozhansky 8), S. Saarelma 1), A. Saveliev 9), R. Scannell 5), S. Sharapov 1), V. Shevchenko 1), S. Shibaev 1), K. Stammers 1), J. Storrs 1), A. Sykes 1), A. Tabasso 1), D. Taylor 1), M.R. Tournianski 1), A. Turner 1), G. Turri 2), M. Valovic 1), F. Volpe 1), G. Voss 1), M.J. Walsh 10), J.R. Watkins 1), H.R. Wilson 1), M. Wisse 5) and the MAST, NBI and ECRH Teams.

1)EURATOM/UKAEA Fusion Association, Culham Science Centre, Abingdon, Oxfordshire OX14 3DB, UK2)Imperial College, Prince Consort Road, London SW7 2BZ, UK3)Kurchatov Institute, Moscow, Russia4)Oxford University, UK5)University College, Cork, Ireland 6)Queens University, Belfast, UK7)EURATOM/IPP.CR Fusion Association, Institute of Plasma Physics, Prague, Czech Republic8)St. Petersburg State Politechnical University, Polytechnicheskaya 29, 195251 St. Petersburg, Russia9)A.F. Ioffe Physico-Technical Institute, St. Petersburg, Russia10)Walsh Scientific Ltd, Culham Science Centre, Abingdon, OX14 3EB, UK11)ENEA, Frascati, Italy

Contributors and Conclusions

Additional slides

70 keV, RT = -0.8 m, dZ = -0.1 m 70 keV, RT =-0.8 m, dZ = -0.6 m

Current P5geometry - forupgrade, coilswill be movedtowards mid-plane

On-axis PINI Off-axis PINI

Compact, intense neutron source (line-integral flux same as JET, JT-60U)

Beam-target neutron distribution sensitive diagnostic of fast-ions

Investigating possibilities for diagnostics, e.g. Stilbene detectors

drsep plays a key role in MASTMAST has fully symmetric upper and lower divertors and can operate from LSN to USN

New studies now show that PL-H decreases by factor 2 in CDND compared to similar shaped Lower SND plasmas

Same trend observed in MAST-ASDEX upgrade similarity experiments. Factor 1.25 reduction in PL-H

Neutral Beam Current Drive

0

200

400

600

MAST #9382

ne (m-3)

ne

Te

Te (eV)

0.4 0.6 0.8 1.0 1.2 1.40.0

2.0

4.0 Z

eff

R (m)

0

2x1019

4x1019

NBCD Modelling Multi-chord, 50Hz Te,ne, Ti and Zeff diagnostics

NBI monitoring by BES (div etc.), edge n0 from linear CDD

Larmor orbit Monte Carlo tracker (TRANSP), and the full gyro orbit treatment in (LOCUST).

EBE from

plas

ma

to ra

diom

eter

Tilted spinning mirror for angular scan (multi frequency) of EBW emission (red ellipses)& its time evolution Proof of Principle: Inclination of the contours of BXO conversion efficiency (colour ellipses) Inclination of field lines at cutoff location q-profile

12,000 rpm prototype (5ms resolution)

Tilted spinning mirror for angular scan of EBW emission

Radial electrostatic streamers observed in calculations up ~100e wide (~1cm)

Nonlinear collisionless ETG calculations in flux-tube geometry, assuming adiabatic ions, at n=0.4 surface in MAST

Non-linear GS2 analysis for e- transport - radial electrostatic streamers predicted

Nonlinear collisionless ETG calculations in flux-tube geometry, assuming adiabatic ions, at n=0.4 surface in MAST

Non-linear GS2 analysis for e- transport - radial electrostatic streamers predicted

Nonlinear simulation converges well for range

of flux tube dimensions and wavenumbers

Indicates e ~ 10 m2/s (cf Gyro-Bohm estimate

of e = 0.6 m2/s)

- within a factor 2 of TRANSP value

L-mode H-mode

Ip ~750 kABT ~0.6T<ne> ~3x1019m-3

Ip ~750 kABT ~0.6T<ne> ~3x1019m-3

Spectrometer coupled to 224 chords 64 toroidal chords on each NBI 32 passive toroidal chords 64 poloidal chords (32 32 on/off-beam) being commissioned

New enhanced CXRS (R~Li)

H-mode discharge as calculated by TRANSP neutrals contribute to the particle balance only towards the edge (r/a>0.6)(specific to H-mode) in the core the particle balance dominated by Gbeam and the neocl. ware pinch source GW=neVw

moderate ne peaking required in CTF seems to be possible due to significant Gbeam fueling

Particle Confinement

ne profiles in MAST are defined by NBI fuelling and neoclassical pinch sources

Co- and counter NBI discharges

H-mode easily achieved in cntr NBIsimilar ne,Te pedestals, ne profile has no density ears

much higher Vf in cntr NBI case

Co- and counter NBI discharges

similar Ip and input PNBI

similar WMHD despite increase fast ion losses lower neutron rate indicative of increased fast ion losses

Heating power in cntr NBi only half of co-NBI at similar input PNBI

Confinement in cntr NBI twice as good as in co NBI NBI generated Er<0 (augments edge Er in H-mode)

EBW driven current with (solid) and without trapping effects (dashed) in a range of plasma temperatures and densities.Input power 150 kW, 28 GHz.

expected next vac. break non inductive current up 150kA is predicted

EBW CD start up on MAST

Documents

Presented by: Mikhail Tournianski, for the MAST team Overview of recent results and plans on MAST This work was jointly funded by the UK Engineering &