From: wolfe@PSFC.MIT.EDU
Reply-To: WOLFE@PSFC.MIT.EDU
Subject: Alcator C-Mod Weekly Highlights
newsgroups: sci.physics.plasma
Organization: MIT



Alcator C-Mod Weekly Highlights
August 27, 2001

The Maintenance, Upgrade and Inspection period continued at Alcator C-Mod last
week. Partial disassembly of the machine is proceeding, and preparation for
the planned upgrade installations is progressing on schedule.

Operations
----------

The cryostat has been disassembled and moved away from the machine. The
machine connections, cooling tubes, and electrical insulation are in very
good condition. The status of these systems has been documented, and we
are continuing with disassembly. A view of the machine can be found at

http://www.psfc.mit.edu/cmod/operations/EngImages/Inspection_2001-2002/Disassembl
y_Assembly/P0001863.JPG

The k-port horizontal flange is being prepared for removal in this picture.

The in-vessel railing to support divertor modification activities has been
installed, and inner divertor work is proceeding. The LED in-vessel lighting
system has been installed and is operational. Additional LED spot lights have
been purchased and installed. New tent racks to facilitate vessel access
are in place.

The Power Systems Group has completed plans for the installation of cooling
fans in the TMX supplies, including both the mechanical and electrical aspects
of the job. The parts and tooling for the job have been ordered. The
construction of the prototype duct box for cooling of the Interphase
transformers at the TF supplies is in progress.

The cell is now ready for outside contractors to begin their work on the
new mezzanine needed to support the lower hybrid klystons. Transformers
located on the east wall of the cell have been relocated on the north side,
freeing up space for the mezzanine. RF transmission lines have also been
moved out of the way, and diagnostic systems have been removed from the cell.


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

All three ICRF antennas and their associated vacuum feed thrus have been
removed from the machine. This includes the Faraday screens from D and E-port
antennas that have not been removed in over 5 years. To summarize the
observations from the inspection thus far, the feedthrus for J and D-port
antennas are in excellent condition. Two of E-port's feedthrus will require
some work to repair arc damage on the vacuum side. There is evidence of
arcing between the D and E-port antenna straps and their respective Faraday
screen. The BN tile fasteners show some damage from excessive heat. The
J-port Faraday screen is in good condition, and the straps have arc damage at
the ground bridge. As on D and E, the J-port BN fasteners show damage
associated with overheating.

Diagnostic Neutral Beam Systems
--------------------------------

The DNB duct was completely detached from C-Mod to make way for
continued disassembly of C-Mod. The duct was removed, inspected and
stored. The in-vessel MSE optics were detached from the F-port
flange to allow removal of the flange. These optics were also
detached from the in-vessel supports in preparation for removal from
the vacuum vessel along with F-port early next week.

Lower Hybrid MIE Project
------------------------

The concrete pad to support the HVPS has been poured. Several meetings
between contractors, and MIT and C-Mod personnel were held throughout the
week to make sure the pad will conform to spec.

One of the new CPCI data acquisition crates has been installed in the Lower
Hybrid control room for use during power supply and active controller testing
and eventually for data acquisition in that area.


Inner Divertor
--------------

The vendor continues to make good progress on the remaining girdle
plates. We continue to make fitups and test new diagnostics that will
be installed in and behind the divertor.

Removal of the old inner divertor modules is 95% complete. The survey of the
inner wall has been completed. Preliminary installation trials with the stud
welding fixture are complete.

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

David Mikkelsen (PPPL) visited MIT and ran EFIT, with help from Steve
Wolfe. He has now demonstrated that the 'q' and magnetic shear at the
mid-radius of C-Mod plasmas are not strongly constrained by the available data
(including the sawtooth inversion radius at a/3). He also discussed with Earl
Marmar the prospects for improving the constraints on q and shear, using the
Lithium pellet ablation cloud internal magnetic field measurements, which
could make possible more definitive predictions of turbulent transport.

Rex Gandy from University of Idaho visited PSFC from Monday, August 20 to
Tuesday, August 21. He and Yongkyoon In discussed the electron temperature
fluctuations using radiometry.