Alcator C-MOD  
			Weekly Highlight Report 
			August 25, 1993


Alcator C-MOD has completed the second block of runs in the Phase I 
experimental program and is now engaged in a scheduled three-week maintenance
period. 

The final plasma run day of this block was dedicated to ICRF coupling
studies using the movable monopole antenna. Over 250 kW net power was
successfully launched into the plasma. The best loading was obtained with
the antenna located 1cm behind the limiter. Inferred loading resistances
appear to be consistent with expectations based on code modeling. Effects
of the injected RF power were observed on several diagnostics, including
soft xrays, radiated power, and edge probes. No major influxes of
impurities were observed, nor was there evidence of RF heating. The
radiated power increased by significantly less than the injected RF power.
For these shots, the minority (hydrogen) concentration was not being
controlled, as the run started with a hydrogen target plasma and changed
over to deuterium operation in the course of the day. This run was also the
first time a deuterium majority target plasma has been used on C-MOD (the
pellet run earlier in the week used deuterium pellets into a hydrogen
target plasma). 

The power systems group tested the reverse bridges of all of the Robicon
PF supplies in preparation for four quadrant operation, which will be available
following installation of the new reactors in the crowbar buss. Some minor
problems were identified in the tests, which will be addressed during the
maintenance period.

Annual maintenance in the high-voltage yard and substation is being carried
out this week. This work, which is coordinated with the Francis Bitter
National Magnet Laboratory, which also uses the substation, requires that
experimental power be shut down for about a week. Additionally, maintenance
was performed on the 480VAC breaker feeding the test cell on Tuesday. 

A clean vent of the tokamak (no manned access) has been carried out this
week. The capillary gas puff tubes in the lower divertor assembly were
brought out to a set of valves, and will be connected to one of the gas
plenums for use in radiative and gaseous divertor experiments. A
twelve-hour calibration of the neutron detector system was carried out with
the source inside the vessel during this vent.  Some additional minor
vacuum maintenance was performed, and small system adjustments and
installations were made for other diagnostics. The machine is now back
under vacuum, pending leak checking.

The charge exchange neutral particle analyzer diagnostic has been installed
on F-port. This system, which is an upgrade of a diagnostic used on Alcator C, 
will be used for ion temperature measurements, analysis of RF-generated ion
tails, and determination of the H/D ratios in hydrogen minority heating
experiments. 

Dr. C.H. Ma, from Oak Ridge National Laboratory, visited the lab this week
to begin installation of his Faraday rotation experiment. This
diagnostic is to be installed in conjunction with the C-MOD two color
interferometer system (which is already in routine operation), and will
provide current density profile measurements. 

The flywheel, which is scheduled to be installed following completion of the
the Phase I campaign, and which will provide the stored energy to allow
operation of the C-MOD facility at full design parameters, has passed its
final spin testing and has been accepted. The flywheel is now in transit
from the testing site to its port of departure for shipment to the US.