M. Valovic L. Garzotti C. Gurl A. Kirk D. Dunai A.R. Field I. Lupelli G. Naylor A. Thornton The MAST Team
The fuelling of plasmas by shallow frozen pellets with simultaneous mitigation of edge- localised modes (ELM) by external magnetic perturbation is demonstrated on the MAST tokamak. In these plasmas post-pellet particle loss is dominated by ELMs. It is shown that the size of post-pellet ELMs can be controlled by external magnetic perturbations. Post…
Preprint PublishedS. S. Henderson L. Garzotti F.J. Casson D. Dickinson M. O'Mullane A. Patel C.M. Roach H.P. Summers H. Tanabe M. Valovic MAST team
Carbon and nitrogen impurity transport coefficients are determined from gas puff experiments carried out during repeat L-mode discharges on the Mega-Amp Spherical Tokamak (MAST) and compared against a previous analysis of helium impurity transport on MAST. The impurity density profiles are measured on the lowfield side of the plasma, therefore this…
Preprint PublishedS. S. Henderson L. Garzotti F. J. Casson D. Dickinson M. F. J. Fox M. O’Mullane A. Patel C. M. Roach H. P. Summers M. Valovic The Mast Team
Time-dependent helium gas puff experiments have been performed on the Mega Ampere Spherical Tokamak (MAST) during a two point plasma current scan in L-mode and a confinement scan at 900 kA. An evaluation of the He II spectrum line induced by charge exchange suggests anomalous rates of diffusion and inward convection in the outer regions of both L-m…
PublishedL. Garzotti J. Figueiredo C. M. Roach M. Valovic D. Dickinson G. Naylor M. Romanelli R. Scannell G. Szepesi The Mast Team
Reactor grade plasmas are likely to be fuelled by pellet injection. This technique transiently perturbs the profiles, driving the density profile hollow and flattening the edge temperature profile. After the pellet perturbation, the density and temperature profiles relax towards their quasi-steady-state shape. Microinstabilities influence plasma co…
PublishedC. D. Warrick R. J. Buttery G. Cunningham S. J. Fielding T. C. Hender B. Lloyd A.W. Morris M. R. O’Brien T. Pinfold K. Stammers M. Valovic M. Walsh,* H. R. Wilson Compass-D Rf Teams
Lower hybrid current drive (LHCD) with modest powers ( 10% of the total power input) has been used for the first time to completely stabilize performance limiting neoclassical tearing modes in many COMPASS-D tokamak discharges. The stabilizing effect in these experiments is consistent with a reduction in the free energy available in the current pro…
PublishedM Valovic G Cunningham L Garzotti C Gurl A Kirk G Naylor A Patel R Scannell The Mast Team
Shallow fuelling pellets are injected from the high field side into plasmas in which ELMs have been mitigated using external magnetic perturbation coils. The data are compared with ideal assumptions in the ITER fuelling model, namely that mitigated ELMs are not affected by fuelling pellets. Firstly it is shown that during the pellet evaporation an …
PublishedM Valovic L Garzotti C Gurl R Akers J Harrison C Michael G Naylor R Scannell The Mast Team
Access into H-mode is studied in the MAST tokamak when plasma is fuelled by cryogenic pellets. It is shown that pellet fuelling from the high field side allows access to Hmode in plasmas heated by neutral beams. Simple and two-stage L-H transitions are identified. The results of comparison of the L-H transitions with pellet injection with transitio…
PublishedJakub Urban Michal Stránsky Vladimíir Fuchs Irina Voitsekhovitch Martin Valovic
The COMPASS tokamak, a mid-sized flexible device with ITER-like shape, which can operate in H-mode, is starting its re-established operation at the Institute of Plasma Physics in Prague. A new 600 kW, 40 keV neutral beam injection (NBI) system is foreseen as a major upgrade. Reported here are predictive simulations with the ASTRA transport code, in…
PublishedA. Thyagaraja M. Valovic P. J. Knight
It is shown that the transition from L-mode to H-mode regimes in tokamaks can be reproduced using a two-fluid, fully electromagnetic, plasma model when a suitable particle sink is added at the edge. Such a model is implemented in the CUTIE code [A. Thyagaraja et al. , Eur. J. Mech. B/Fluids 23 , 475 (2004)] and is illustrated on plasma parameters t…
PublishedL Garzotti L Baylor F Köchl B Pégourié M Valovic K B Axon J Dowling C Gurl G P Maddison H Nehme T O’Gorman A Patel M Price R Scannell M Walsh
Pellet material deposited in a tokamak plasma experiences a drift towards the low field side of the torus induced by the magnetic field gradient. Plasma fuelling in ITER relies on the beneficial effect of this drift to increase the pellet deposition depth and fuelling efficiency. It is therefore important to analyse this phenomenon in present machi…
Published