Overview of new MAST physics in anticipation of first results from MAST Upgrade
Reviewartikel, 2019

The mega amp spherical tokamak (MAST) was a low aspect ratio device (R/a = 0.85/0.65 ∼ 1.3) with similar poloidal cross-section to other medium-size tokamaks. The physics programme concentrates on addressing key physics issues for the operation of ITER, design of DEMO and future spherical tokamaks by utilising high resolution diagnostic measurements closely coupled with theory and modelling to significantly advance our understanding. An empirical scaling of the energy confinement time that favours higher power, lower collisionality devices is consistent with gyrokinetic modelling of electron scale turbulence. Measurements of ion scale turbulence with beam emission spectroscopy and gyrokinetic modelling in up-down symmetric plasmas find that the symmetry of the turbulence is broken by flow shear. Near the non-linear stability threshold, flow shear tilts the density fluctuation correlation function and skews the fluctuation amplitude distribution. Results from fast particle physics studies include the observation that sawteeth are found to redistribute passing and trapped fast particles injected from neutral beam injectors in equal measure, suggesting that resonances between the m = 1 perturbation and the fast ion orbits may be playing a dominant role in the fast ion transport. Measured D-D fusion products from a neutron camera and a charged fusion product detector are 40% lower than predictions from TRANSP/NUBEAM, highlighting possible deficiencies in the guiding centre approximation. Modelling of fast ion losses in the presence of resonant magnetic perturbations (RMPs) can reproduce trends observed in experiments when the plasma response and charge-exchange losses are accounted for. Measurements with a neutral particle analyser during merging-compression start-up indicate the acceleration of ions and electrons. Transport at the plasma edge has been improved through reciprocating probe measurements that have characterised a geodesic acoustic mode at the edge of an ohmic L-mode plasma and particle-in-cell modelling has improved the interpretation of plasma potential estimates from ball-pen probes. The application of RMPs leads to a reduction in particle confinement in L-mode and H-mode and an increase in the core ionization source. The ejection of secondary filaments following type-I ELMs correlates with interactions with surfaces near the X-point. Simulations of the interaction between pairs of filaments in the scrape-off layer suggest this results in modest changes to their velocity, and in most cases can be treated as moving independently. A stochastic model of scrape-off layer profile formation based on the superposition of non-interacting filaments is in good agreement with measured time-average profiles. Transport in the divertor has been improved through fast camera imaging, indicating the presence of a quiescent region devoid of filament near the X-point, extending from the separatrix to ψ n ∼ 1.02. Simulations of turbulent transport in the divertor show that the angle between the divertor leg on the curvature vector strongly influences transport into the private flux region via the interchange mechanism. Coherence imaging measurements show counter-streaming flows of impurities due to gas puffing increasing the pressure on field lines where the gas is ionised. MAST Upgrade is based on the original MAST device, with substantially improved capabilities to operate with a Super-X divertor to test extended divertor leg concepts. SOLPS-ITER modelling predicts the detachment threshold will be reduced by more than a factor of 2, in terms of upstream density, in the Super-X compared with a conventional configuration and that the radiation front movement is passively stabilised before it reaches the X-point. 1D fluid modelling reveals the key role of momentum and power loss mechanisms in governing detachment onset and evolution. Analytic modelling indicates that long legs placed at large major radius, or equivalently low at the target compared with the X-point are more amenable to external control. With MAST Upgrade experiments expected in 2019, a thorough characterisation of the sources of the intrinsic error field has been carried out and a mitigation strategy developed.

MAST

spherical tokamak

MAST Upgrade

Författare

J.R. Harrison

Culham Lab

R. Akers

Culham Lab

S.Y. Allan

Culham Lab

J.S. Allcock

Culham Lab

J. O. Allen

University of York

L. Appel

Culham Lab

M. Barnes

Culham Lab

N. Ben Ayed

Culham Lab

W. Boeglin

Florida International University

C. Bowman

University of York

J. Bradley

University of Liverpool

P. Browning

University of Manchester

P. Bryant

University of Liverpool

M. Carr

Culham Lab

M. Cecconello

Uppsala universitet

C. Challis

Culham Lab

S. Chapman

The University of Warwick

I.T. Chapman

Culham Lab

G. Colyer

University of Oxford

S. Conroy

Uppsala universitet

N.J. Conway

Culham Lab

M. Cox

Culham Lab

G. Cunningham

Culham Lab

R.O. Dendy

Culham Lab

William D. Dorland

University of Oxford

Benjamin Dudson

University of York

Luke Easy

Culham Lab

S.D. Elmore

Culham Lab

T. Farley

Culham Lab

X. Feng

Durham University

A.R. Field

Culham Lab

A. Fil

University of York

G.M. Fishpool

Culham Lab

M. Fitzgerald

Culham Lab

K. Flesch

University of Wisconsin Madison

M.F.J. Fox

Culham Lab

H. Frerichs

University of Wisconsin Madison

S. Gadgil

The University of Warwick

D. Gahle

Culham Lab

Luca Garzotti

Culham Lab

Y.-C. Ghim

Culham Lab

S. Gibson

Culham Lab

K.J. Gibson

University of York

S. Hall

Culham Lab

C. Ham

Culham Lab

N. Heiberg

Culham Lab

S.S. Henderson

Culham Lab

Edmund Hood Highcock

University of Oxford

Chalmers tekniska högskola

Bogdan Hnat

The University of Warwick

J. Howard

Australian National University

J. Huang

Chinese Academy of Sciences

S.W.A. Irvine

The University of Warwick

A.S. Jacobsen

Max Planck-institutet

O. Jones

Culham Lab

I. Katramados

Culham Lab

D. Keeling

Culham Lab

A. Kirk

Culham Lab

I. Klimek

Uppsala universitet

L. Kogan

Culham Lab

J. Leland

Culham Lab

B. Lipschultz

University of York

B. Lloyd

Culham Lab

J. Lovell

Oak Ridge National Laboratory

B. Madsen

Danmarks Tekniske Universitet (DTU)

O. Marshall

University of York

R. Martin

Culham Lab

G. McArdle

Culham Lab

K. McClements

Culham Lab

B. McMillan

The University of Warwick

A. Meakins

Culham Lab

H.F. Meyer

Culham Lab

F. Militello

Culham Lab

J. Milnes

Culham Lab

S. Mordijck

The College of William and Mary

A.W. Morris

Culham Lab

D. Moulton

Culham Lab

D. Muir

Culham Lab

K. Mukhi

Culham Lab

S. Murphy-Sugrue

Culham Lab

O. Myatra

University of York

G. Naylor

Culham Lab

P. Naylor

University of York

Sarah Newton

Culham Lab

T. O'Gorman

Culham Lab

John Omotani

Culham Lab

M.G. O'Mullane

University of Strathclyde

S. Orchard

Culham Lab

S.J.P. Pamela

Culham Lab

L. Pangione

Culham Lab

F. I. Parra

Culham Lab

R.V. Perez

Florida International University

L. Piron

Culham Lab

M. Price

Culham Lab

M. Reinke

Oak Ridge National Laboratory

F. Riva

Culham Lab

C. M. Roach

Culham Lab

D. Robb

University of Glasgow

D. Ryan

Culham Lab

S. Saarelma

Culham Lab

M. Salewski

Danmarks Tekniske Universitet (DTU)

S. Scannell

Culham Lab

AA Schekochihin

University of Oxford

O. Schmitz

University of Wisconsin Madison

S. E. Sharapov

Culham Lab

R. Sharples

Durham University

S.A. Silburn

Culham Lab

S.F. Smith

Culham Lab

A. Sperduti

Uppsala universitet

R. Stephen

Culham Lab

N.T. Thomas-Davies

Culham Lab

A.J. Thornton

Culham Lab

M. Turnyanskiy

Culham Lab

Martin Valovic

Culham Lab

F van Wyk

Culham Lab

R.G.L. Vann

University of York

N. R. Walkden

Culham Lab

I. Waters

University of Wisconsin Madison

H.R. Wilson

Culham Lab

Nuclear Fusion

0029-5515 (ISSN)

Vol. 59 11 112011

Ämneskategorier

Meteorologi och atmosfärforskning

Annan fysik

Fusion, plasma och rymdfysik

DOI

10.1088/1741-4326/ab121c

Mer information

Senast uppdaterat

2019-10-07