MAST News Bulletin - October 2004

	News from MAST - October 2004
	MAST Status The 2004 campaign is nearing its end. MAST continues to operate reliably and important new results have been obtained. Further measurements of the structure of edge localised modes (ELMs), using a new probe, have confirmed and extended the earlier ground-breaking work on the filamentary structure of ELMs. Results of the earlier studies, which exploited the excellent diagnostic imaging capabilities in MAST, have recently been reported in Physical Review Letters (Kirk A et al 2004, Phys. Rev. Lett. 92 245002). The new error field compensation system has significantly extended the operating regimes on MAST and initial error field scaling studies have been completed. These studies are in line with earlier results from JET, and the U.S. tokamak DIII-D, but provide additional information on scaling with plasma aspect ratio. Measurements of fast ion generation during "internal reconnection events" appear to confirm a theory developed at Culham and published in Physical Review Letters (P Helander et al 2002, Phys. Rev. Lett. 89 235002-1). Evidence of mode conversion to electron Bernstein waves (EBW) has been observed during experiments using the 60GHz ECRH facility at up to 1MW. The MAST team is presently preparing for a short intervention in Nov/Dec during which a number of changes to the port geometry will be made to further optimise plasma diagnostics. Diagnostic News First results have been obtained from the new charge exchange recombination spectroscopy diagnostic which provides measurements of ion temperature and plasma rotation velocity with improved spatial resolution.
	Improved spatial resolution of ion temperature profile measurements on MAST using the new charge exchange recombination spectroscopy (CXRS) system
	The design of the MAST vessel coupled with the geometry of the spherical tokamak make MAST uniquely suited for wide-angle in-vessel views. A new wide-angle lens for the high-speed infrared camera allows, for the first time on any tokamak, a simultaneous infrared view of almost half the total plasma facing surfaces at frame rates up to 320Hz. Infrared imaging thermography of the divertor wetted areas has already contributed to an improved understanding of power deposition in MAST, including during transients. The new wide-angle view allows exploration of toroidally asymmetric power deposition onto the first wall, which has been predicted to occur during large transient events such as type I ELMs and disruptions and which is a key area of study for ITER.
	Wide angle infra-red imaging on MAST showing power flow to lower divertor target during a vertical displacement event. Note the substantial toroidal asymmetries
	Collaboration Activities Gary Taylor of PPPL visited MAST to participate in EBW studies. Brian Lloyd delivered a presentation remotely to the NSTX Research Forum on 22nd September entitled "MAST Status, Plans and MAST/NSTX Collaborations 2005". Following a recent call for experimental proposals for ASDEX Upgrade, several proposals for collaborative experiments with MAST were submitted by MAST physicists. Geof Maddison, of the MAST team, attended the ASDEX Upgrade programme meeting at Schloss Ringberg. Other News Elise Delchambre has joined the MAST team on a Marie-Curie Fellowship to work on power loading studies using infra-red imaging. Steve Lisgo has also arrived from the University of Toronto to work on edge physics. Two new PhD students have joined the MAST team. Adam Foster (Strathclyde University) is working on impurity transport and Seb Tallents (Imperial College) is working on scrape-off layer physics studies. Publications & Presentations Mikhail Gryaznevich and Sergei Sharapov attended the 4th International ST Workshop in Kyoto, Japan, and delivered presentations on "Recent results from MAST" and Alfven eigenmodes in spherical tokamaks", respectively.
	Attendees at the 4th International ST Workshop, Kyoto, Japan
	William Morris, Andrew Darke and Steve Gee attended the 23rd Symposium on Fusion Technology in Venice, Italy, where they presented the following papers: A W Morris et al, "Spherical tokamaks: present status and role in the development of fusion power", A C Darke et al, "The MAST improved divertor", S Gee et al, "MAST neutral beam long pulse upgrade". The following journal publications have recently been issued: "A comparison of mid-plane scrape-off-layer measurements with model predictions in MAST and the calculation of cross-field transport coefficients" A Kirk et al 2004, Plasma Phys. Contr. Fusion 46 1591. "Stability at High Performance in MAST", R.J. Buttery et al 2004, Nuclear Fusion 44 1027. "High definition imaging in the MAST spherical tokamak from soft X-rays to the infrared" P G Carolan et al 2004, Rev. Sci. Instrum. 75 4069 "A versatile multi wavelength imaging diagnostic in the MAST spherical tokamak" A Patel et al 2004, Rev. Sci Instrum. 75 4145