Overview of MAST results

I. T. Chapman, J. Adamek, R. J. Akers, S. Allan, L. Appel, O. Asunta, M. Barnes, N. Ben Ayed, T. Bigelow, W. Boeglin, J. Bradley, J. Brünner, P. Cahyna, M. Carr, J. Caughman, M. Cecconello, C. Challis, S. Chapman, J. Chorley, G. Colyer & 124 others N. Conway, W. A. Cooper, M. Cox, N. Crocker, B. Crowley, G. Cunningham, A. Danilov, D. Darrow, R. Dendy, A. Diallo, D. Dickinson, S. Diem, W. Dorland, B. Dudson, D. Dunai, L. Easy, S. Elmore, A. Field, G. Fishpool, M. Fox, E. Fredrickson, S. Freethy, L. Garzotti, Y. C. Ghim, K. Gibson, J. Graves, C. Gurl, W. Guttenfelder, C. Ham, J. Harrison, D. Harting, E. Havlickova, J. Hawke, N. Hawkes, T. Hender, S. Henderson, E. Highcock, J. Hillesheim, B. Hnat, J. Holgate, J. Horacek, J. Howard, B. Huang, K. Imada, O. Jones, S. Kaye, D. Keeling, A. Kirk, I. Klimek, M. Kocan, H. Leggate, M. Lilley, B. Lipschultz, S. Lisgo, Y. Q. Liu, B. Lloyd, B. Lomanowski, I. Lupelli, G. Maddison, J. Mailloux, R. Martin, G. McArdle, K. McClements, B. McMillan, A. Meakins, H. Meyer, C. Michael, F. Militello, J. Milnes, A. W. Morris, G. Motojima, D. Muir, E. Nardon, V. Naulin, G. Naylor, A. Nielsen, M. O'Brien, T. O'Gorman, Y. Ono, H. Oliver, S. Pamela, L. Pangione, F. Parra, A. Patel, W. Peebles, M. Peng, R. Perez, S. Pinches, L. Piron, M. Podesta, M. Price, M. Reinke, Y. Ren, C. Roach, J. Robinson, M. Romanelli, V. Rozhansky, S. Saarelma, S. Sangaroon, A. Saveliev, R. Scannell, A. Schekochihin, S. Sharapov, R. Sharples, V. Shevchenko, S. Silburn, J. Simpson, J. Storrs, Y. Takase, H. Tanabe, H. Tanaka, D. Taylor, G. Taylor, D. Thomas, N. Thomas-Davies, A. Thornton, M. Turnyanskiy, M. Valovic, R. Vann, N. Walkden, H. Wilson, L. V. Wyk, T. Yamada, S. Zoletnik

Research output: Contribution to journalArticle

12 Citations (Scopus)

Abstract

The Mega Ampere Spherical Tokamak (MAST) programme is strongly focused on addressing key physics issues in preparation for operation of ITER as well as providing solutions for DEMO design choices. In this regard, MAST has provided key results in understanding and optimizing H-mode confinement, operating with smaller edge localized modes (ELMs), predicting and handling plasma exhaust and tailoring auxiliary current drive. In all cases, the high-resolution diagnostic capability on MAST is complemented by sophisticated numerical modelling to facilitate a deeper understanding. Mitigation of ELMs with resonant magnetic perturbations (RMPs) with toroidal mode number nRMP = 2, 3, 4, 6 has been demonstrated: at high and low collisionality; for the first ELM following the transition to high confinement operation; during the current ramp-up; and with rotating nRMP = 3 RMPs. nRMP = 4, 6 fields cause less rotation braking whilst the power to access H-mode is less with nRMP = 4 than nRMP = 3, 6. Refuelling with gas or pellets gives plasmas with mitigated ELMs and reduced peak heat flux at the same time as achieving good confinement. A synergy exists between pellet fuelling and RMPs, since mitigated ELMs remove fewer particles. Inter-ELM instabilities observed with Doppler backscattering are consistent with gyrokinetic simulations of micro-tearing modes in the pedestal. Meanwhile, ELM precursors have been strikingly observed with beam emission spectroscopy (BES) measurements. A scan in beta at the L-H transition shows that pedestal height scales strongly with core pressure. Gyro-Bohm normalized turbulent ion heat flux (as estimated from the BES data) is observed to decrease with increasing tilt of the turbulent eddies. Fast ion redistribution by energetic particle modes depends on density, and access to a quiescent domain with 'classical' fast ion transport is found above a critical density. Highly efficient electron Bernstein wave current drive (1 A W-1) has been achieved in solenoid-free start-up. A new proton detector has characterized escaping fusion products. Langmuir probes and a high-speed camera suggest filaments play a role in particle transport in the private flux region whilst coherence imaging has measured scrape-off layer (SOL) flows. BOUT++ simulations show that fluxes due to filaments are strongly dependent on resistivity and magnetic geometry of the SOL, with higher radial fluxes at higher resistivity. Finally, MAST Upgrade is due to begin operation in 2016 to support ITER preparation and importantly to operate with a Super-X divertor to test extended leg concepts for particle and power exhaust.

Original languageEnglish
Article number104008
Pages (from-to)1-19
Number of pages20
JournalNuclear Fusion
Volume55
Issue number10
DOIs
Publication statusPublished - 19 Jun 2015

Fingerprint

refueling
pellets
perturbation
heat flux
filaments
preparation
ions
electrical resistivity
braking
scale height
high speed cameras
electrostatic probes
energetic particles
solenoids
ramps
spectroscopy
backscattering
simulation
fusion
vortices

Keywords

  • high confinement operation
  • mega ampere spherical tokamak
  • numerical modelling
  • resonant magnetic perturbations

Cite this

Chapman, I. T., Adamek, J., Akers, R. J., Allan, S., Appel, L., Asunta, O., ... Zoletnik, S. (2015). Overview of MAST results. Nuclear Fusion, 55(10), 1-19. [104008]. https://doi.org/10.1088/0029-5515/55/10/104008
Chapman, I. T. ; Adamek, J. ; Akers, R. J. ; Allan, S. ; Appel, L. ; Asunta, O. ; Barnes, M. ; Ayed, N. Ben ; Bigelow, T. ; Boeglin, W. ; Bradley, J. ; Brünner, J. ; Cahyna, P. ; Carr, M. ; Caughman, J. ; Cecconello, M. ; Challis, C. ; Chapman, S. ; Chorley, J. ; Colyer, G. ; Conway, N. ; Cooper, W. A. ; Cox, M. ; Crocker, N. ; Crowley, B. ; Cunningham, G. ; Danilov, A. ; Darrow, D. ; Dendy, R. ; Diallo, A. ; Dickinson, D. ; Diem, S. ; Dorland, W. ; Dudson, B. ; Dunai, D. ; Easy, L. ; Elmore, S. ; Field, A. ; Fishpool, G. ; Fox, M. ; Fredrickson, E. ; Freethy, S. ; Garzotti, L. ; Ghim, Y. C. ; Gibson, K. ; Graves, J. ; Gurl, C. ; Guttenfelder, W. ; Ham, C. ; Harrison, J. ; Harting, D. ; Havlickova, E. ; Hawke, J. ; Hawkes, N. ; Hender, T. ; Henderson, S. ; Highcock, E. ; Hillesheim, J. ; Hnat, B. ; Holgate, J. ; Horacek, J. ; Howard, J. ; Huang, B. ; Imada, K. ; Jones, O. ; Kaye, S. ; Keeling, D. ; Kirk, A. ; Klimek, I. ; Kocan, M. ; Leggate, H. ; Lilley, M. ; Lipschultz, B. ; Lisgo, S. ; Liu, Y. Q. ; Lloyd, B. ; Lomanowski, B. ; Lupelli, I. ; Maddison, G. ; Mailloux, J. ; Martin, R. ; McArdle, G. ; McClements, K. ; McMillan, B. ; Meakins, A. ; Meyer, H. ; Michael, C. ; Militello, F. ; Milnes, J. ; Morris, A. W. ; Motojima, G. ; Muir, D. ; Nardon, E. ; Naulin, V. ; Naylor, G. ; Nielsen, A. ; O'Brien, M. ; O'Gorman, T. ; Ono, Y. ; Oliver, H. ; Pamela, S. ; Pangione, L. ; Parra, F. ; Patel, A. ; Peebles, W. ; Peng, M. ; Perez, R. ; Pinches, S. ; Piron, L. ; Podesta, M. ; Price, M. ; Reinke, M. ; Ren, Y. ; Roach, C. ; Robinson, J. ; Romanelli, M. ; Rozhansky, V. ; Saarelma, S. ; Sangaroon, S. ; Saveliev, A. ; Scannell, R. ; Schekochihin, A. ; Sharapov, S. ; Sharples, R. ; Shevchenko, V. ; Silburn, S. ; Simpson, J. ; Storrs, J. ; Takase, Y. ; Tanabe, H. ; Tanaka, H. ; Taylor, D. ; Taylor, G. ; Thomas, D. ; Thomas-Davies, N. ; Thornton, A. ; Turnyanskiy, M. ; Valovic, M. ; Vann, R. ; Walkden, N. ; Wilson, H. ; Wyk, L. V. ; Yamada, T. ; Zoletnik, S. / Overview of MAST results. In: Nuclear Fusion. 2015 ; Vol. 55, No. 10. pp. 1-19.
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abstract = "The Mega Ampere Spherical Tokamak (MAST) programme is strongly focused on addressing key physics issues in preparation for operation of ITER as well as providing solutions for DEMO design choices. In this regard, MAST has provided key results in understanding and optimizing H-mode confinement, operating with smaller edge localized modes (ELMs), predicting and handling plasma exhaust and tailoring auxiliary current drive. In all cases, the high-resolution diagnostic capability on MAST is complemented by sophisticated numerical modelling to facilitate a deeper understanding. Mitigation of ELMs with resonant magnetic perturbations (RMPs) with toroidal mode number nRMP = 2, 3, 4, 6 has been demonstrated: at high and low collisionality; for the first ELM following the transition to high confinement operation; during the current ramp-up; and with rotating nRMP = 3 RMPs. nRMP = 4, 6 fields cause less rotation braking whilst the power to access H-mode is less with nRMP = 4 than nRMP = 3, 6. Refuelling with gas or pellets gives plasmas with mitigated ELMs and reduced peak heat flux at the same time as achieving good confinement. A synergy exists between pellet fuelling and RMPs, since mitigated ELMs remove fewer particles. Inter-ELM instabilities observed with Doppler backscattering are consistent with gyrokinetic simulations of micro-tearing modes in the pedestal. Meanwhile, ELM precursors have been strikingly observed with beam emission spectroscopy (BES) measurements. A scan in beta at the L-H transition shows that pedestal height scales strongly with core pressure. Gyro-Bohm normalized turbulent ion heat flux (as estimated from the BES data) is observed to decrease with increasing tilt of the turbulent eddies. Fast ion redistribution by energetic particle modes depends on density, and access to a quiescent domain with 'classical' fast ion transport is found above a critical density. Highly efficient electron Bernstein wave current drive (1 A W-1) has been achieved in solenoid-free start-up. A new proton detector has characterized escaping fusion products. Langmuir probes and a high-speed camera suggest filaments play a role in particle transport in the private flux region whilst coherence imaging has measured scrape-off layer (SOL) flows. BOUT++ simulations show that fluxes due to filaments are strongly dependent on resistivity and magnetic geometry of the SOL, with higher radial fluxes at higher resistivity. Finally, MAST Upgrade is due to begin operation in 2016 to support ITER preparation and importantly to operate with a Super-X divertor to test extended leg concepts for particle and power exhaust.",
keywords = "high confinement operation, mega ampere spherical tokamak, numerical modelling, resonant magnetic perturbations",
author = "Chapman, {I. T.} and J. Adamek and Akers, {R. J.} and S. Allan and L. Appel and O. Asunta and M. Barnes and Ayed, {N. Ben} and T. Bigelow and W. Boeglin and J. Bradley and J. Br{\"u}nner and P. Cahyna and M. Carr and J. Caughman and M. Cecconello and C. Challis and S. Chapman and J. Chorley and G. Colyer and N. Conway and Cooper, {W. A.} and M. Cox and N. Crocker and B. Crowley and G. Cunningham and A. Danilov and D. Darrow and R. Dendy and A. Diallo and D. Dickinson and S. Diem and W. Dorland and B. Dudson and D. Dunai and L. Easy and S. Elmore and A. Field and G. Fishpool and M. Fox and E. Fredrickson and S. Freethy and L. Garzotti and Ghim, {Y. C.} and K. Gibson and J. Graves and C. Gurl and W. Guttenfelder and C. Ham and J. Harrison and D. Harting and E. Havlickova and J. Hawke and N. Hawkes and T. Hender and S. Henderson and E. Highcock and J. Hillesheim and B. Hnat and J. Holgate and J. Horacek and J. Howard and B. Huang and K. Imada and O. Jones and S. Kaye and D. Keeling and A. Kirk and I. Klimek and M. Kocan and H. Leggate and M. Lilley and B. Lipschultz and S. Lisgo and Liu, {Y. Q.} and B. Lloyd and B. Lomanowski and I. Lupelli and G. Maddison and J. Mailloux and R. Martin and G. McArdle and K. McClements and B. McMillan and A. Meakins and H. Meyer and C. Michael and F. Militello and J. Milnes and Morris, {A. W.} and G. Motojima and D. Muir and E. Nardon and V. Naulin and G. Naylor and A. Nielsen and M. O'Brien and T. O'Gorman and Y. Ono and H. Oliver and S. Pamela and L. Pangione and F. Parra and A. Patel and W. Peebles and M. Peng and R. Perez and S. Pinches and L. Piron and M. Podesta and M. Price and M. Reinke and Y. Ren and C. Roach and J. Robinson and M. Romanelli and V. Rozhansky and S. Saarelma and S. Sangaroon and A. Saveliev and R. Scannell and A. Schekochihin and S. Sharapov and R. Sharples and V. Shevchenko and S. Silburn and J. Simpson and J. Storrs and Y. Takase and H. Tanabe and H. Tanaka and D. Taylor and G. Taylor and D. Thomas and N. Thomas-Davies and A. Thornton and M. Turnyanskiy and M. Valovic and R. Vann and N. Walkden and H. Wilson and Wyk, {L. V.} and T. Yamada and S. Zoletnik",
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Chapman, IT, Adamek, J, Akers, RJ, Allan, S, Appel, L, Asunta, O, Barnes, M, Ayed, NB, Bigelow, T, Boeglin, W, Bradley, J, Brünner, J, Cahyna, P, Carr, M, Caughman, J, Cecconello, M, Challis, C, Chapman, S, Chorley, J, Colyer, G, Conway, N, Cooper, WA, Cox, M, Crocker, N, Crowley, B, Cunningham, G, Danilov, A, Darrow, D, Dendy, R, Diallo, A, Dickinson, D, Diem, S, Dorland, W, Dudson, B, Dunai, D, Easy, L, Elmore, S, Field, A, Fishpool, G, Fox, M, Fredrickson, E, Freethy, S, Garzotti, L, Ghim, YC, Gibson, K, Graves, J, Gurl, C, Guttenfelder, W, Ham, C, Harrison, J, Harting, D, Havlickova, E, Hawke, J, Hawkes, N, Hender, T, Henderson, S, Highcock, E, Hillesheim, J, Hnat, B, Holgate, J, Horacek, J, Howard, J, Huang, B, Imada, K, Jones, O, Kaye, S, Keeling, D, Kirk, A, Klimek, I, Kocan, M, Leggate, H, Lilley, M, Lipschultz, B, Lisgo, S, Liu, YQ, Lloyd, B, Lomanowski, B, Lupelli, I, Maddison, G, Mailloux, J, Martin, R, McArdle, G, McClements, K, McMillan, B, Meakins, A, Meyer, H, Michael, C, Militello, F, Milnes, J, Morris, AW, Motojima, G, Muir, D, Nardon, E, Naulin, V, Naylor, G, Nielsen, A, O'Brien, M, O'Gorman, T, Ono, Y, Oliver, H, Pamela, S, Pangione, L, Parra, F, Patel, A, Peebles, W, Peng, M, Perez, R, Pinches, S, Piron, L, Podesta, M, Price, M, Reinke, M, Ren, Y, Roach, C, Robinson, J, Romanelli, M, Rozhansky, V, Saarelma, S, Sangaroon, S, Saveliev, A, Scannell, R, Schekochihin, A, Sharapov, S, Sharples, R, Shevchenko, V, Silburn, S, Simpson, J, Storrs, J, Takase, Y, Tanabe, H, Tanaka, H, Taylor, D, Taylor, G, Thomas, D, Thomas-Davies, N, Thornton, A, Turnyanskiy, M, Valovic, M, Vann, R, Walkden, N, Wilson, H, Wyk, LV, Yamada, T & Zoletnik, S 2015, 'Overview of MAST results', Nuclear Fusion, vol. 55, no. 10, 104008, pp. 1-19. https://doi.org/10.1088/0029-5515/55/10/104008

Overview of MAST results. / Chapman, I. T.; Adamek, J.; Akers, R. J.; Allan, S.; Appel, L.; Asunta, O.; Barnes, M.; Ayed, N. Ben; Bigelow, T.; Boeglin, W.; Bradley, J.; Brünner, J.; Cahyna, P.; Carr, M.; Caughman, J.; Cecconello, M.; Challis, C.; Chapman, S.; Chorley, J.; Colyer, G.; Conway, N.; Cooper, W. A.; Cox, M.; Crocker, N.; Crowley, B.; Cunningham, G.; Danilov, A.; Darrow, D.; Dendy, R.; Diallo, A.; Dickinson, D.; Diem, S.; Dorland, W.; Dudson, B.; Dunai, D.; Easy, L.; Elmore, S.; Field, A.; Fishpool, G.; Fox, M.; Fredrickson, E.; Freethy, S.; Garzotti, L.; Ghim, Y. C.; Gibson, K.; Graves, J.; Gurl, C.; Guttenfelder, W.; Ham, C.; Harrison, J.; Harting, D.; Havlickova, E.; Hawke, J.; Hawkes, N.; Hender, T.; Henderson, S.; Highcock, E.; Hillesheim, J.; Hnat, B.; Holgate, J.; Horacek, J.; Howard, J.; Huang, B.; Imada, K.; Jones, O.; Kaye, S.; Keeling, D.; Kirk, A.; Klimek, I.; Kocan, M.; Leggate, H.; Lilley, M.; Lipschultz, B.; Lisgo, S.; Liu, Y. Q.; Lloyd, B.; Lomanowski, B.; Lupelli, I.; Maddison, G.; Mailloux, J.; Martin, R.; McArdle, G.; McClements, K.; McMillan, B.; Meakins, A.; Meyer, H.; Michael, C.; Militello, F.; Milnes, J.; Morris, A. W.; Motojima, G.; Muir, D.; Nardon, E.; Naulin, V.; Naylor, G.; Nielsen, A.; O'Brien, M.; O'Gorman, T.; Ono, Y.; Oliver, H.; Pamela, S.; Pangione, L.; Parra, F.; Patel, A.; Peebles, W.; Peng, M.; Perez, R.; Pinches, S.; Piron, L.; Podesta, M.; Price, M.; Reinke, M.; Ren, Y.; Roach, C.; Robinson, J.; Romanelli, M.; Rozhansky, V.; Saarelma, S.; Sangaroon, S.; Saveliev, A.; Scannell, R.; Schekochihin, A.; Sharapov, S.; Sharples, R.; Shevchenko, V.; Silburn, S.; Simpson, J.; Storrs, J.; Takase, Y.; Tanabe, H.; Tanaka, H.; Taylor, D.; Taylor, G.; Thomas, D.; Thomas-Davies, N.; Thornton, A.; Turnyanskiy, M.; Valovic, M.; Vann, R.; Walkden, N.; Wilson, H.; Wyk, L. V.; Yamada, T.; Zoletnik, S.

In: Nuclear Fusion, Vol. 55, No. 10, 104008, 19.06.2015, p. 1-19.

Research output: Contribution to journalArticle

TY - JOUR

T1 - Overview of MAST results

AU - Chapman, I. T.

AU - Adamek, J.

AU - Akers, R. J.

AU - Allan, S.

AU - Appel, L.

AU - Asunta, O.

AU - Barnes, M.

AU - Ayed, N. Ben

AU - Bigelow, T.

AU - Boeglin, W.

AU - Bradley, J.

AU - Brünner, J.

AU - Cahyna, P.

AU - Carr, M.

AU - Caughman, J.

AU - Cecconello, M.

AU - Challis, C.

AU - Chapman, S.

AU - Chorley, J.

AU - Colyer, G.

AU - Conway, N.

AU - Cooper, W. A.

AU - Cox, M.

AU - Crocker, N.

AU - Crowley, B.

AU - Cunningham, G.

AU - Danilov, A.

AU - Darrow, D.

AU - Dendy, R.

AU - Diallo, A.

AU - Dickinson, D.

AU - Diem, S.

AU - Dorland, W.

AU - Dudson, B.

AU - Dunai, D.

AU - Easy, L.

AU - Elmore, S.

AU - Field, A.

AU - Fishpool, G.

AU - Fox, M.

AU - Fredrickson, E.

AU - Freethy, S.

AU - Garzotti, L.

AU - Ghim, Y. C.

AU - Gibson, K.

AU - Graves, J.

AU - Gurl, C.

AU - Guttenfelder, W.

AU - Ham, C.

AU - Harrison, J.

AU - Harting, D.

AU - Havlickova, E.

AU - Hawke, J.

AU - Hawkes, N.

AU - Hender, T.

AU - Henderson, S.

AU - Highcock, E.

AU - Hillesheim, J.

AU - Hnat, B.

AU - Holgate, J.

AU - Horacek, J.

AU - Howard, J.

AU - Huang, B.

AU - Imada, K.

AU - Jones, O.

AU - Kaye, S.

AU - Keeling, D.

AU - Kirk, A.

AU - Klimek, I.

AU - Kocan, M.

AU - Leggate, H.

AU - Lilley, M.

AU - Lipschultz, B.

AU - Lisgo, S.

AU - Liu, Y. Q.

AU - Lloyd, B.

AU - Lomanowski, B.

AU - Lupelli, I.

AU - Maddison, G.

AU - Mailloux, J.

AU - Martin, R.

AU - McArdle, G.

AU - McClements, K.

AU - McMillan, B.

AU - Meakins, A.

AU - Meyer, H.

AU - Michael, C.

AU - Militello, F.

AU - Milnes, J.

AU - Morris, A. W.

AU - Motojima, G.

AU - Muir, D.

AU - Nardon, E.

AU - Naulin, V.

AU - Naylor, G.

AU - Nielsen, A.

AU - O'Brien, M.

AU - O'Gorman, T.

AU - Ono, Y.

AU - Oliver, H.

AU - Pamela, S.

AU - Pangione, L.

AU - Parra, F.

AU - Patel, A.

AU - Peebles, W.

AU - Peng, M.

AU - Perez, R.

AU - Pinches, S.

AU - Piron, L.

AU - Podesta, M.

AU - Price, M.

AU - Reinke, M.

AU - Ren, Y.

AU - Roach, C.

AU - Robinson, J.

AU - Romanelli, M.

AU - Rozhansky, V.

AU - Saarelma, S.

AU - Sangaroon, S.

AU - Saveliev, A.

AU - Scannell, R.

AU - Schekochihin, A.

AU - Sharapov, S.

AU - Sharples, R.

AU - Shevchenko, V.

AU - Silburn, S.

AU - Simpson, J.

AU - Storrs, J.

AU - Takase, Y.

AU - Tanabe, H.

AU - Tanaka, H.

AU - Taylor, D.

AU - Taylor, G.

AU - Thomas, D.

AU - Thomas-Davies, N.

AU - Thornton, A.

AU - Turnyanskiy, M.

AU - Valovic, M.

AU - Vann, R.

AU - Walkden, N.

AU - Wilson, H.

AU - Wyk, L. V.

AU - Yamada, T.

AU - Zoletnik, S.

PY - 2015/6/19

Y1 - 2015/6/19

N2 - The Mega Ampere Spherical Tokamak (MAST) programme is strongly focused on addressing key physics issues in preparation for operation of ITER as well as providing solutions for DEMO design choices. In this regard, MAST has provided key results in understanding and optimizing H-mode confinement, operating with smaller edge localized modes (ELMs), predicting and handling plasma exhaust and tailoring auxiliary current drive. In all cases, the high-resolution diagnostic capability on MAST is complemented by sophisticated numerical modelling to facilitate a deeper understanding. Mitigation of ELMs with resonant magnetic perturbations (RMPs) with toroidal mode number nRMP = 2, 3, 4, 6 has been demonstrated: at high and low collisionality; for the first ELM following the transition to high confinement operation; during the current ramp-up; and with rotating nRMP = 3 RMPs. nRMP = 4, 6 fields cause less rotation braking whilst the power to access H-mode is less with nRMP = 4 than nRMP = 3, 6. Refuelling with gas or pellets gives plasmas with mitigated ELMs and reduced peak heat flux at the same time as achieving good confinement. A synergy exists between pellet fuelling and RMPs, since mitigated ELMs remove fewer particles. Inter-ELM instabilities observed with Doppler backscattering are consistent with gyrokinetic simulations of micro-tearing modes in the pedestal. Meanwhile, ELM precursors have been strikingly observed with beam emission spectroscopy (BES) measurements. A scan in beta at the L-H transition shows that pedestal height scales strongly with core pressure. Gyro-Bohm normalized turbulent ion heat flux (as estimated from the BES data) is observed to decrease with increasing tilt of the turbulent eddies. Fast ion redistribution by energetic particle modes depends on density, and access to a quiescent domain with 'classical' fast ion transport is found above a critical density. Highly efficient electron Bernstein wave current drive (1 A W-1) has been achieved in solenoid-free start-up. A new proton detector has characterized escaping fusion products. Langmuir probes and a high-speed camera suggest filaments play a role in particle transport in the private flux region whilst coherence imaging has measured scrape-off layer (SOL) flows. BOUT++ simulations show that fluxes due to filaments are strongly dependent on resistivity and magnetic geometry of the SOL, with higher radial fluxes at higher resistivity. Finally, MAST Upgrade is due to begin operation in 2016 to support ITER preparation and importantly to operate with a Super-X divertor to test extended leg concepts for particle and power exhaust.

AB - The Mega Ampere Spherical Tokamak (MAST) programme is strongly focused on addressing key physics issues in preparation for operation of ITER as well as providing solutions for DEMO design choices. In this regard, MAST has provided key results in understanding and optimizing H-mode confinement, operating with smaller edge localized modes (ELMs), predicting and handling plasma exhaust and tailoring auxiliary current drive. In all cases, the high-resolution diagnostic capability on MAST is complemented by sophisticated numerical modelling to facilitate a deeper understanding. Mitigation of ELMs with resonant magnetic perturbations (RMPs) with toroidal mode number nRMP = 2, 3, 4, 6 has been demonstrated: at high and low collisionality; for the first ELM following the transition to high confinement operation; during the current ramp-up; and with rotating nRMP = 3 RMPs. nRMP = 4, 6 fields cause less rotation braking whilst the power to access H-mode is less with nRMP = 4 than nRMP = 3, 6. Refuelling with gas or pellets gives plasmas with mitigated ELMs and reduced peak heat flux at the same time as achieving good confinement. A synergy exists between pellet fuelling and RMPs, since mitigated ELMs remove fewer particles. Inter-ELM instabilities observed with Doppler backscattering are consistent with gyrokinetic simulations of micro-tearing modes in the pedestal. Meanwhile, ELM precursors have been strikingly observed with beam emission spectroscopy (BES) measurements. A scan in beta at the L-H transition shows that pedestal height scales strongly with core pressure. Gyro-Bohm normalized turbulent ion heat flux (as estimated from the BES data) is observed to decrease with increasing tilt of the turbulent eddies. Fast ion redistribution by energetic particle modes depends on density, and access to a quiescent domain with 'classical' fast ion transport is found above a critical density. Highly efficient electron Bernstein wave current drive (1 A W-1) has been achieved in solenoid-free start-up. A new proton detector has characterized escaping fusion products. Langmuir probes and a high-speed camera suggest filaments play a role in particle transport in the private flux region whilst coherence imaging has measured scrape-off layer (SOL) flows. BOUT++ simulations show that fluxes due to filaments are strongly dependent on resistivity and magnetic geometry of the SOL, with higher radial fluxes at higher resistivity. Finally, MAST Upgrade is due to begin operation in 2016 to support ITER preparation and importantly to operate with a Super-X divertor to test extended leg concepts for particle and power exhaust.

KW - high confinement operation

KW - mega ampere spherical tokamak

KW - numerical modelling

KW - resonant magnetic perturbations

UR - http://www.scopus.com/inward/record.url?scp=84948148773&partnerID=8YFLogxK

U2 - 10.1088/0029-5515/55/10/104008

DO - 10.1088/0029-5515/55/10/104008

M3 - Article

VL - 55

SP - 1

EP - 19

JO - Nuclear Fusion

JF - Nuclear Fusion

SN - 0029-5515

IS - 10

M1 - 104008

ER -

Chapman IT, Adamek J, Akers RJ, Allan S, Appel L, Asunta O et al. Overview of MAST results. Nuclear Fusion. 2015 Jun 19;55(10):1-19. 104008. https://doi.org/10.1088/0029-5515/55/10/104008