Alcator C-Mod Weekly Highlights
		         March 9, 1998
 

The Alcator C-Mod maintenance period continued last week with the removal of
diagnostics, igloo blocks, gas systems, thermocouple and heater cabling, and
RF transmission lines and resonant loops.  The upper cryostat cover was
removed and the drawbars holding the upper dome to the cylinder were loosened.
The removal of the bus tunnel and inspection plate at A-side allowed a first
inspection of the TF to be made.  The fault seems to have been confined to the
A-right vertical leg which contains the first and last turn of the TF magnet.
A detailed inspection will be possible later this week when the cylinder is
removed.

Glow discharge cleaning in helium was run last week in preparation for
bringing the machine up-to-air.  Several up-to-air/pumpdown cycles were
performed to react the residual boron compounds with room air.  One of the
large horizontal ports was removed and room air is now purging through the
vessel.  We are preparing for machine entry to make radiation surveys, do
video documentation, and perform calibrations of several optical diagnostics.
Following the calibrations, the remaining horizontal and vertical ports can be
removed, preparing the way for removal of the cylinder.

A great deal of work was completed on the Mod/Reg system for the diagnostic
neutral beam last week.  Design of the control architecture and identification
of the control signals were completed, 120 VAC service was installed, power
distribution system controls were tested, and the isolation transformer/power
distribution system construction was begun.  With installation of the
isolation amplifiers, and a test of the MDSPlus data acquisition, the beam
profile monitor was completed and is ready for installation in the beamline.
The process gas system for fueling the source was successfully calibrated and
tested using nitrogen gas.  The PLC processor was moved to its final location
to facilitate addition of power supply controls to the system currently
controlling DNB vacuum hardware.

We have begun to look at improvements to the over-voltage protection circuits
for several of the magnet power supplies.  Some shots were lost during the
last campaign because of spurious over-voltage indications.  In addition,
discussions on improvements to the OH and EFC supplies have continued as we
attempt to improve plasma position control.

Earl Marmar attended the "National Compact Stellarator Concept Design Study
Informal Program Advisory Committee" meeting last week (March 5-6), held at
the Princeton Plasma Physics Laboratory.  Earl is a member of the Informal
PAC.

Several scientists visited or continued visits here last week as part of the
PPPL collaboration.  Dave Johnson and Ben Leblanc were here working on the
X-point Thomson scattering system.  They also assisted in preparing the
X-point system for the up-to-air.  Gerd Schilling continued to help with the
analysis of our latest RF heating data.