Overview of new MAST physics in anticipation of first results from MAST Upgrade
Artikel i vetenskaplig tidskrift, 2019

The mega amp spherical tokamak (MAST) was a low aspect ratio device (R/a = 0.85/0.65 similar to 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 psi(n) similar to 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 B at the target compared with the X-point arc 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

MAST Upgrade

spherical tokamak

Författare

J. R. Harrison

CCFE

R. J. Akers

CCFE

S. Y. Allan

CCFE

J. S. Allcock

CCFE

Durham University

J. O. Allen

University of York

L. Appel

CCFE

M. Barnes

Plasma Sci & Fus Ctr, 167 Albany St

University of Oxford

CCFE

N. Ben Ayedl

CCFE

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

CCFE

M. Cecconello

Uppsala universitet

C. D. Challis

CCFE

S. Chapman

The University of Warwick

I. T. Chapman

CCFE

G. J. Colyer

University of Oxford

University of Exeter

S. Conroy

Uppsala universitet

N. J. Conway

CCFE

M. Cox

CCFE

G. Cunningham

CCFE

R. O. Dendy

The University of Warwick

CCFE

W. Dorland

University of Maryland

University of Oxford

B. D. Dudson

University of York

L. Easy

University of York

CCFE

S. D. Elmore

CCFE

T. Farley

University of Liverpool

CCFE

X. Feng

Durham University

A. R. Field

CCFE

A. Fil

University of York

G. M. Fishpool

CCFE

M. Fitzgerald

CCFE

K. Flesch

University of Wisconsin Madison

M. F. J. Fox

CCFE

University of Oxford

H. Frerichs

University of Wisconsin Madison

S. Gadgil

The University of Warwick

D. Gahle

CCFE

University of Strathclyde

L. Garzotti

CCFE

Y-C Ghim

Korea Adv Inst Sci & Technol

CCFE

University of Oxford

S. Gibson

Durham University

CCFE

K. J. Gibson

University of York

S. Hall

CCFE

C. Ham

CCFE

N. Heiberg

CCFE

S. S. Henderson

CCFE

Edmund Hood Highcock

Chalmers, Fysik, Subatomär fysik och plasmafysik

B. 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

Durham University

CCFE

I Katramados

CCFE

D. Keeling

CCFE

A. Kirk

CCFE

I Klimek

Uppsala universitet

L. Kogan

CCFE

J. Leland

University of Liverpool

CCFE

B. Lipschultz

University of York

B. Lloyd

CCFE

J. Lovell

Oak Ridge Natl Lab

B. Madsen

Danmarks Tekniske Universitet (DTU)

O. Marshall

University of York

R. Martin

CCFE

G. McArdle

CCFE

K. McClements

CCFE

B. McMillan

The University of Warwick

A. Meakins

CCFE

H. F. Meyer

CCFE

F. Militello

CCFE

J. Milnes

CCFE

S. Mordijck

Coll William & Mary, Dept Comp Sci

A. W. Morris

CCFE

D. Moulton

CCFE

D. Muir

CCFE

K. Mukhi

CCFE

University of Manchester

S. Murphy-Sugrue

CCFE

University of Liverpool

O. Myatra

University of York

G. Naylor

CCFE

P. Naylor

University of York

S. L. Newton

CCFE

T. O'Gorman

CCFE

J. Omotani

CCFE

M. G. O'Mullane

University of Strathclyde

S. Orchard

University of York

CCFE

S. J. P. Pamela

CCFE

L. Pangione

CCFE

F. Parra

CCFE

University of Oxford

Perez

Florida International University

L. Piron

CCFE

M. Price

CCFE

M. L. Reinke

Oak Ridge Natl Lab

F. Riva

CCFE

C. M. Roach

CCFE

D. Robb

University of Glasgow

D. Ryan

CCFE

S. Saarelma

CCFE

M. Salewski

Danmarks Tekniske Universitet (DTU)

S. Scannell

CCFE

A. A. Schekochihin

University of Oxford

O. Schmitz

University of Wisconsin Madison

S. Sharapov

CCFE

R. Sharples

Durham University

S. A. Silburn

CCFE

S. F. Smith

University of York

CCFE

A. Sperduti

Uppsala universitet

R. Stephen

CCFE

N. T. Thomas-Davies

CCFE

A. J. Thornton

CCFE

M. Turnyanskiy

CCFE

M. Valovic

CCFE

F. Van Wyk

Daresbury Laboratory

University of Oxford

CCFE

R. G. L. Vann

University of York

N. R. Walkden

CCFE

I Waters

University of Wisconsin Madison

H. R. Wilson

University of York

CCFE

Nuclear Fusion

0029-5515 (ISSN)

Vol. 59 11 112011

Ämneskategorier

Energiteknik

Fysik

DOI

10.1088/1741-4326/ab121c

Mer information

Senast uppdaterat

2019-10-16