MAST News Bulletin - February 2004

	News from MAST - February 2004 MAST Development The MAST project is close to the end of a 9 month Engineering Break to implement a number of major improvements (see MAST News Bulletin Dec 2003 for a detailed description). Despite the incorporation of additional work, the main tasks of installing the new centre column and the new divertor have been completed on schedule. The MAST re-start programme will begin in April with first physics experiments scheduled for May. Recent additional MAST developments incorporated into the present engineering break include major improvements to the charge exchange recombination spectroscopy (CXRS) diagnostics, improvements to the electron Bernstein wave (EBW) antenna systems and the installation of a 4-coil error field correction coil system. Two new ports have been successfully drilled into the 2cm thick stainless steel vacuum vessel to allow improved CXRS measurements.
	Drilling of new ports in the MAST vessel for improved charge exchange spectroscopy measurements.
	The new CXRS geometry allows the two neutral beam systems to be viewed separately and at the same time the number of viewing chords is being increased by an order of magnitude. This system provides measurements of ion temperature and toroidal rotation velocities (2 x 64 chords).
	Schematic of new CXRS toroidal views in MAST
	In addition, new optical systems have been installed inside the MAST vessel to facilitate measurements of poloidal rotation velocities (64 chords) across most of the plasma cross-section, in particular covering the regions of internal and edge transport barrier formation. Re-alignment of the 60GHz EBW antenna system has been completed and an in-situ alignment monitoring system is being implemented. The antenna comprises 21 mirrors (7 fixed, 14 moveable) for control of the poloidal and toroidal launch angles, as well as the polarisation of the 7 microwave beams.
	MAST EBW antenna
	NBI System Upgrade In parallel with the MAST developments described above, and in the December 2003 bulletin, a major upgrade of the MAST neutral beam heating systems is underway to provide reliable long pulse operation at high power. New residual ion dumps and calorimeters based on hypervapotrons have been installed and the NBI sources are being replaced by JET style PINI systems.
	Actively cooled calorimeter - gate in closed position	Residual beam ion dumps
	The South injector is being upgraded to a PINI system for the M4 campaign and is expected to be available for high power operation in July. The South-West injector will operate with its present source in M4 and will be replaced by a PINI source in November 2004. MAST Research Forum A MAST Research Forum was held at Culham Science Centre on 22/23 January to discuss the detailed experimental programme for 2004. The forum was attended by a number of international and UK university collaborators and an initial batch of 81 experimental proposals has been submitted for the 2004 (M4) campaign. The primary thrusts of the M4 campaign are on confinement scaling, transport & turbulence, ELMs and pedestal physics, electron Bernstein wave heating and integrated scenario development. Other high priority areas include start-up, neutral beam & fast ion physics and disruptions & divertor biasing. Detailed planning of experiments is now underway as well as planning of the substantial restart activities. The M4 physics campaign will run from May until early November. Experimental/Analysis Activities Further MAST data from the 2003 (M3) campaign has been prepared for submission to the ITPA Pedestal Database, the Global Confinement Database and the Profile (ITB) Database. Mikhail Gryaznevich visited NSTX in February to participate in high beta experiments. These experiments confirmed the high beta capability of the spherical tokamak, setting a new tokamak world record for normalised beta and reaching values of toroidal beta close to the world record set in the START spherical tokamak at Culham in 1998. Hendrik Meyer, also visited NSTX in February to complete a campaign of MAST-NSTX H-mode comparison studies which started with experiments in MAST in 2003. These studies, conducted by Hendrik, and Rajesh Maingi (ORNL) of the NSTX team showed that H-mode threshold power levels were similar under comparable conditions. Furthermore, the strong dependence on magnetic geometry reported in MAST was also seen in NSTX where once again optimum H-mode access was observed for a connected double null divertor configuration. Glenn Counsell, Andrew Kirk and Marcus Price visited ASDEX Upgrade in February to conduct joint experiments on the study of edge localised modes (ELMs) and in particular the interaction with the first wall. Direct comparison with MAST data is expected to yield valuable information on a number of key issues. 14th Culham-Ioffe Symposium Five members of the MAST team participated in the annual Culham-Ioffe Symposium in St. Petersburg, 26 - 28 January 2004. Two days of presentations were followed by discussions on future collaboration activities. The Ioffe Institute is home to the Globus-M spherical tokamak, a device intermediate in size between START and MAST/NSTX.