From: WOLFE@PSFC.MIT.EDU
Reply-To: WOLFE@PSFC.MIT.EDU
Subject: Alcator C-Mod Weekly Highlights
Approved: plasma@cs.uml.edu
Newsgroups: sci.physics.plasma


Alcator C-Mod Weekly Highlights
Jan 16, 2001


Work continued at Alcator C-Mod last week on modifications to the J-port
ICRF antenna, repairs and refurbishment to the DNB diagnostics,
and continued maintenance of engineering systems.


General Engineering
-------------------

The LN2 sump was opened up last week and the LN2 pump filters were removed
and cleaned. The filter for the TF first-to-last turn leg was also
inspected and found free of any debris.

Some components for the inner divertor upgrade are arriving from our
vendors. Inconel 718 bolts needed for the upgrade are now in house as
are some of the molybdenum tiles. A small quantity of tiles from one vendor
did not meet spec and have already been returned to the vendor to be reworked.
Major components such as backing plates and C-plates that make up the girdle
are on schedule.

Modifications are nearly complete of the OH commutation bank that will allow
for much easier inspection and component replacement. A failed capacitor
in one of these banks took several days to find and replace during the
last run period.


ICRF Systems
------------

The fabrication of the new boron nitride tiles for the J-port antenna
was completed last week. The tiles were cleaned and then baked at 500C over
the weekend to prepare them for invessel installation. Fit up of the new
antenna septum indicated that modifications to the stainless steel spline that
holds the BN tiles would be required. These changes will be completed
this week. Mockups of the new dB/dt probes were also fit up on the antenna,
and exact lengths for the coax signal leads were determined. We have decided
to delay the pumpdown somewhat so that a better inspection and cleanup of,
and possible modification to the antenna feedlines could be undertaken.
Tracking and arcing marks discovered between the strip lines and septum need
careful evaluation. These components have not been inspected since the
beginning of the 2000 run campaign (Jan 00).


DNB and Related Diagnostics
---------------------------

The DNB optical diagnostics have been carefully inspected. The CXRS optics
were still in alignment, but had been coated during vessel boronizations.
They were removed from the vessel and cleaned. Hoods will be added to slow
the boron deposition rate. The MSE/BES optical alignment was found to be
shifted by approximately 1 cm since the last calibration due to disruption
damage to one of the mirrors. That mirror and its support were removed from
the vessel for repair. An inspection of the inner wall of the vacuum vessel
opposite the DNB duct showed no beam damage. Also, there was no further
beam-induced damage to the DNB duct. Baking of the beam line has begun in
preparation for offline operation of the beam which will continue during
the up-to-air period.


Visitors and Travel
-------------------

Gary Taylor spent the week at C-Mod working on the electron cyclotron
emission diagnostics. A PPPL microwave source was used to optimize GPC2
signals and to carry out tests of the instrument functions of both
GPC and GPC2.

Steve Wolfe and Ron Parker participated in the DIII-D Advisory Committee
Meeting at General Atomics in San Diego last week. Wolfe also presented
a talk on recent C-Mod results to the DIII-D group.