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
Performance optimisation and plasma control Confinement and transport Neutral Beam Current Drive Plasma exhaust Non solenoid start up
Plans and future upgrades to MAST
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
Performance optimisation and plasma control Confinement and transport Neutral Beam Current Drive Plasma exhaust Non solenoid start up
Plans and future upgrades to MAST
Overview of recent results on MAST
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
Performance optimisation and plasma control Confinement and transport Neutral Beam Current Drive Plasma exhaust Non solenoid start up
Plans and future upgrades to MAST
Overview of recent results on 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%
Performance optimisation and plasma control Confinement and transport Neutral Beam Current Drive Plasma exhaust Non solenoid start up
Plans and future upgrades to MAST
Overview of recent results on MAST
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)
Performance optimisation and plasma control Confinement and transport Neutral Beam Current Drive Plasma exhaust Non solenoid start up
Plans and future upgrades to MAST
Overview of recent results on MAST
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
Performance optimisation and plasma control Confinement and transport Neutral Beam Current Drive Plasma exhaust Non solenoid start up
Plans and future upgrades to MAST
Overview of recent results on MAST
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