Alcator C-MOD   
			    Weekly Highlight Report  
				September 30, 1993


Plasma operation continues as scheduled on Alcator C-MOD.  We are now in the 
third week of the current campaign. 

Scrape-off layer and divertor studies were continued, using the fast-scanning
probe, flush-mount probes in the divertor tiles, and divertor bolometry, as
well as the U. of Md OMA and Johns Hopkins Moly Monitor. The subject plasmas
were well-diverted lower single nulls, with currents of 0.5MA and above. Under
some conditions, the MARFE, which is typically located on the inboard-side
above the midplane, was observed to rapidly shift down into the divertor,
accompanied by a large increase in divertor radiation and in the density
measured on the divertor probes.  These experiments were carried out in
hydrogen.

Starting on Friday, September 24, operation has been in deuterium. One run was
devoted to improving startup and discharge behavior with deuterium as the
working gas. Tuesday's run was devoted to RF conditioning and heating
experiments. The plasmas were deuterium majority with hydrogen minority. The
ICRF group has been carrying out antenna conditioning both during plasma
operation and between shots into vacuum. Maximum voltage in the line during
vacuum conditioning has been increased to 50kV. 

A toroidal field scan has been carried out to test transport and axisymmetric
stability at lower q; almost all of our previous runs have been with toroidal
field of approximately 5 Tesla. Starting from a nominal shot with toroidal
field of 5.3 Tesla and plasma current of 0.5MA, and elongation about 1.5, the
toroidal field was lowered to less than 2.5 Tesla. Safety factor q was reduced
from around 6 to of order 3. The toroidal field was ramped down during the 
shots, as well as being lowered at initiation. The startup must be re-tuned for 
each toroidal field setting, because of the field of the effective toroidal 
half-turns of the TF magnet and because changes in alternator loading affect the 
voltage capabilities of the PF supplies. 

Thursday's run is the second dedicated to pellet injection. Deuterium pellets
are injected into a deuterium target plasma with plasma current 0.6MA. Goals
of this run include measurements of density profile evolution, energy
transport effects, and impurity transport. Pellets with up to 2.e20 particles 
are being injected, more than doubling the target density.