Alcator C-Mod Weekly Highlights
			Dec. 27, 2005

FY2006 weeks of research operations:
   Planned:  14 weeks
   Completed: 4 weeks

Operations
----------

Scheduled maintenance activities continued at Alcator C-Mod last week. No
plasma operations were scheduled.

A meeting of the C-Mod Experimental Program Committee was held on Wednesday to
consider schedule options for the remainder of the FY06 campaign. In light of
the results with the screenless J-port ICRF antenna (see below), it was
decided to extend the current maintenance interval to allow a manned-access
vent, during which the J-port Faraday screen will be replaced. Plasma
operations are now planned to resume in February, 2006.

The tokamak has been brought up-to-air, and the vessel is being purged. G- and
B-ports have been prepared for removal. The first manned entry will take place
after the holiday.


Physics
--------

Analysis based on observations of Be-like and N-like Copper VUV emission lines
indicates that copper densities in the range of 10^17/m^3 were present in
recent high-power C-Mod discharges. Conditioning data indicate that the J-port
antenna operating without a Faraday screen is the major source of copper in
these plasmas. Video images showed significant interaction on the
copper-coated Inconel antenna straps. Examination of earlier data, before
removal of the screen, indicates much lower levels of Cu. The radiated power
loss due to the presence of the copper is significant to the power
balance. Copper radiation is emitted from the pedestal region with greater
efficiency than radiation from Mo.

ICRF System
-----------

The quarterly target "Operate J-port ICRF antenna with faraday screen removed;
with at least 2 MW launched power: compare heating and impurity generation to
previous results obtained with the faraday screen (Dec 31, 2006)" has been
completed. A report is in preparation.

Inspection of the FMIT#1 transmitter FPA upper cavity revealed a
misalignment of the cooling jacket diverter bell, which was allowing water
flow to bypass the proper cooling channel. This was re-aligned and reassembled
and the transmitter has been returned to service.

The stub tuner drive for FMIT#4 (J-port antenna) was removed and the
electronic brake replaced. The unit has been reinstalled and tested
successfully.

DNB System
----------

Work last week concentrated on getting the calorimeter thermocouples back
into operation.  This instrumentation provides information on the beam
profile width, and provides the only direct comparison to beam width
measurements made during qualification tests at the vendor's facilities.
All of the 11 thermocouples on the calorimeter were verified to check out
electrically, and their amplifier circuits were also tested successfully.
The beam was operated with full length pulses (total integrated "On" time
of 1.5 s), and the thermocouple digitization was extended to 60 seconds.
Under these conditions it was verified that 9 of the 11 thermocouples were
responding with appropriate signals, both in terms of amplitude and
temporal evolution.  One of the two broken TC's was subsequently fixed.

Lower Hybrid System
-------------------

We continue to prepare the lower hybrid stainless steel couplers for
installation on the launcher with development of the outer waveguide
plug welding process. Following evaluation of test samples from TIG welding
and laser welding vendors, as well as production of in-house
samples, a vendor has been selected and processing of the production couplers
is scheduled for this week.

High power calibration activities have been completed, and we are now ready to
remove the front shorts, absorbers, and other test fixtures for final assembly
of the launcher and installation into C-Mod.

Travel and Vistors
------------------

Mike Kotschenreuther, from the Institute for Fusion Studies, U. Texas at
Austin, visited the PSFC on Tuesday and Wednesday of this week. He gave a
seminar entitled "How Divertors Control Fusion Reactors", and had discussions
on topics of mutual interest with C-Mod scientists including Bruce Lipschultz,
Brian LaBombard, Martin Greenwald, Bob Granetz, Steve Scott, Earl Marmar,
Steve Wolfe, Amanda Hubbard, Paul Bonoli, Darin Ernst and Peter Catto.
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