J.R. Harrison G.M. Fishpool B.D. Dudson
Measurements of intensity fluctuation of light emission within the divertor volume of MAST provide strong evidence for the existence of filamentary structures within the private flux region (PFR). These filaments are observed in L-mode and H-mode confinement regimes. Correlation analysis of the camera data supports the hypothesis that the filaments…
Preprint PublishedA.J. Thornton A. Kirk P. Cahyna I.T. Chapman G. Fishpool J.R. Harrison Y.Q. Liu L. Kripner M. Peterka The MAST Team
The application of resonant magnetic perturbations (RMPs) produces splitting of the divertor strike point due to the interaction of the RMP field and the plasma field. The application of a rotating RMP field causes the strike point splitting to rotate, distributing the particle and heat flux evenly over the divertor. The RMP coils in MAST have been…
Preprint PublishedJ. R. Harrison G. M. Fishpool A. J. Thornton N. R. Walkden MAST team
The transport of particles via intermittent filamentary structures in the private flux region (PFR) of plasmas in the MAST tokamak has been investigated using a fast framing camera recording visible light emission from the volume of the lower divertor, as well as Langmuir probes and IR thermography monitoring particle and power fluxes to plasma-fac…
PublishedN.R. Walkden J. Adamek S. Allan B. D. Dudson S. Elmore G. Fishpool J. Harrison A. Kirk M. Komm
The ball pen probe (BPP) technique is used successfully to make profile measurements of plasma potential, electron temperature, and radial electric field on the Mega Amp Spherical Tokamak. The potential profile measured by the BPP is shown to significantly differ from the floating potential both in polarity and profile shape. By combining the BPP p…
Preprint PublishedI. Klimek M. Cecconello S. E. Sharapov J. Harrison G. Ericsson
On MAST, compressional Alfven eigenmodes can be destabilized by the presence of a sufficiently large population of energetic particles in the plasma. This dependence was studied in a series of very similar discharges in which increasing amounts of hydrogen were puffed into a deuterium plasma. A simple method to estimate the isotopic ratio nH/nD usi…
PublishedS. A. Silburn J. R. Harrison J. Howard K. J. Gibson H. Meyer C. A. Michael R. M. Sharples
A new coherence imaging Doppler spectroscopy diagnostic has been deployed on the UK’s Mega Amp Spherical Tokamak for scrape-off-layer and divertor impurity flow measurements. The system has successfully obtained 2D images of C III, C II, and He II line-of-sight flows, in both the lower divertor and main scrape-off-layer. Flow imaging has been obt…
PublishedA.J. Thornton A. Kirk J.R. Harrison P. Cahyna I.T. Chapman E. Nardon The Mast Team
The high pressure gradients in the edge of a tokamak plasma can lead to the formation of explosive plasma instabilities known as edge localised modes (ELMs). The control of ELMs is an important requirement for the next generation of fusion devices such as ITER. Experiments performed on the Mega Amp Spherical Tokamak (MAST) at Culham have shown that…
PublishedI.T. Chapman J.T. Holgate N. Ben Ayed G. Cunningham C.J. Ham J.R. Harrison A. Kirk G. Mcardle A. Patel R. Scannell The Mast Team
When resonant magnetic perturbations are applied in MAST, the plasma edge boundary experiences a three dimensional distortion, which can be a few percent of the minor radius in amplitude, in good agreement with ideal 3d equilibrium modelling. This displacement occurs in plasmas both with radial position feedback control applied, and without feedbac…
PublishedA. Kirk D. Dunai M. Dunne G. Huijsmans S. Pamela M. Becoulet J.R. Harrison J. Hillesheim C. Roach S. Saarelma The Mast Team
The type I ELMy H-mode is the baseline operating scenario for ITER. While it is known that the type I ELM ultimately results from the peeling-ballooning instability, there is growing experimental evidence that a mode grows up before the ELM crash that may modify the edge plasma, which then leads to the ELM event due to the peeling-ballooning mode. …
PublishedI.T. Chapman A. Kirk R.J. Akers C.J. Ham J.R. Harrison J. Hawke Y.Q. Liu K.G. McClements S. Pamela S. Saarelma R. Scannell A.J. Thornton The Mast Team
ELM mitigation has been demonstrated in MAST using resonant magnetic perturbations (RMPs) with toroidal mode number, n RM P = 2, 3, 4, 6. It has been observed that the mitigated ELM frequency increases with the amplitude of the applied field provided it is above a critical threshold. This threshold value depends on the mode number of the RMP, with …
Published