M. F. M. De Bock N. J. Conway M. J. Walsh P. G. Carolan N. C. Hawkes
A multichord motional Stark effect MSE system has recently been built on the MAST tokamak. In MAST the π and σ lines of the MSE spectrum overlap due to the low magnetic field typical for present day spherical tokamaks. Also, the field curvature results in a large change in the pitch angle over the observation volume. The measured polarization ang…
PublishedG. Cunningham
In frequency modulated continuous wave reflectometry, used for density profile measurement in fusion plasmas, it is usual to measure the beat frequency between the launched wave and the reflected wave, and from this to calculate the position of the reflecting layer in the plasma. The absolute phase of the beat signal is usually neglected. The reaso…
PublishedP. Molchanov V. Rozhansky S. Voskoboynikov S. Tallents G. Counsell A. Kirk
A comparison is presented of measured and simulated parallel flows in the low field side scrape-off layer of MAST Ohmic shots. Simulations with B2SOLPS5.0 code reproduce the experimentally observed co-current rotation direction. The absolute values of the simulated Mach number are smaller than those of the measured ones; the difference might reach …
PublishedR. J. Mckay K. G. McClements A. Thyagaraja L. Fletcher Euratom/Ukaea
A full orbit test-particle approach is used to study the collisional transport of impurity (carbon) ions in spherical tokamak (ST) plasmas with transonic and subsonic toroidal flows. The efficacy of this approach is demonstrated by reproducing the results of classical transport theory in the large aspect ratio limit. The equilibrium parameters used…
PublishedJ.W. Connor A. Kirk H.R. Wilson
Edge Localised Modes (ELMs) are periodic disturbances of the plasma periphery occurring in tokamaks with an H-mode edge transport barrier. As a result, a fraction of the plasma energy present in the confined hot edge plasma is transferred to the open field lines in the divertor region, ultimately appearing at the divertor target plates. These event…
PublishedA. Thyagaraja F. Schwander K. G. McClements
Collective fast ion effects on flows in tokamaks are investigated analytically and numerically. A general analysis of noncollisional electrodynamic momentum transfer from fast ions to bulk plasma is presented, with polarization effects and dissipation in the bulk plasma taken into account. The analysis is illustrated using idealized simulations of …
PublishedV. Shevchenko G. Cunningham A. Gurchenko E. Gusakov B. Lloyd M. O’Brien A. Saveliev A. Surkov F.Volpe M. Walsh
There is a comprehensive, closely-interlinked electron Bernstein wave (EBW) programme on MAST covering heating experiments, plasma start-up studies, plasma emission measurements, theory and modelling. In this paper we report on proof-of-principle EBW heating experiments conducted on MAST with a 60 GHz, 1 MW gyrotron complex. A 28 GHz (200 kW) EBW s…
PublishedV. Shevchenko G. Cunningham A. Gurchenko E. Gusakov B. Lloyd M. O’Brien A. Saveliev A. Surkov F. Volpe M. Walsh
Burning plasma spherical tokamaks (STs) rely on off-axis current drive (CD) and nonsolenoid start-up techniques. Electron Bernstein waves (EBWs) may provide efficient off-axis heating and CD in high-density ST plasmas. EBWs may also be used in the plasma start-up phase because EBW absorption and CD efficiency remain high even in relatively cold pla…
PublishedN. J. Conway P. G. Carolan J. Mccone M. J. Walsh M. Wisse
A major upgrade to the charge exchange recombination spectroscopy system on MAST has recently been implemented. The new system consists of a high-throughput spectrometer coupled to a total of 224 spatial channels, including toroidal and poloidal views of both neutral heating beams on MAST. Radial resolution is 1 cm, comparable to the ion Larmor rad…
Published