Newsgroups: sci.physics.plasma
From WOLFE@CMOD2.PFC.MIT.EDU Wed Jan 10 12:02:57 1996
From: WOLFE@CMOD2.PFC.MIT.EDU
Organization: MIT
Subject: Alcator C-MOD Weekly Highlights

Alcator C-MOD Weekly Highlights
Jan. 9, 1996

Operation of Alcator C-MOD resumed last week with a half-day run to establish
a baseline condition prior to boronization. A campaign of boronization
wall-conditioning, using the electron cyclotron discharge cleaning (ECDC)
technique, was then begun.

Testing of the EF1 power supply with the new transformer was successfully
completed. This upgrade will allow higher voltages to be applied to the EF1
coils with a resulting improvement in plasma control.

A short clean vent (He backfill) was performed to remove an obstruction from
the Thomson scattering beam baffles. The obstruction was identified as a hose
clamp buckle which had apparently been accidentally left inside the vessel
during the last major opening.

A short (half-day) run was scheduled and carried out on Friday in order to get
a good baseline of machine operation before boronization. After a round of
helium ECDC, a series of five standard fiducial shots were run, followed by a
density scan. RF power up to 2MW was injected. One lithium pellet shot was
taken, resulting in a PEP mode.

The diborane (10% B2D6, 90% He) bottle was delivered on Friday and placed in
our external toxic gas storage cabinet.

Following a full run-through of the boronization procedure, using helium gas,
the diborane bottle was installed in the in-cell diborane cabinet. This
procedure was performed under controlled access by two people wearing Self
Contained Breathing Apparatus (SCBA). While the diborane is in the cell,
restricted access procedures are in effect.

The boronization campaign was begun on Sunday and is continuing this week. The
procedure being employed is similar to our normal ECDC, using the
helium-diborane mixture as the working gas. The toroidal field is swept to
move the resonance layer across the chamber. Unlike our usual procedure, the
discharge is pulsed at a 50% duty cycle to facilitate more uniform deposition
of boron on the walls. Once a satisfactory boron layer has been deposited,
tokamak operation will resume, beginning with a repetition of the baseline
shots taken last week.