Alcator C-Mod Weekly Highlights
                        Jan 17, 2012

FY2011 weeks of research operations
   Target: 17 weeks
   Completed: 1.3 weeks
   Plasma Shots: 281

Operations
-----------

Last week was a maintenance week at Alcator C-Mod. No plasma operation was
scheduled. Plasma experiments are planned to resume this week.

Run Planning
------------

A meeting of the C-Mod Experimental Program Committee was held on Friday, Jan
13. The operating schedule, plans, and program priorities were
discussed. Seven new or revised miniproposals were reviewed and approved.

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

After several years of successful operation, the Fast Ferrite Tuner (FFT) #2
was disassembled following observations of arcing during high power operation
of the E-port antenna. We found four ferrite tiles were debonded from one
section of the center conductor (paddle) and there were extensive arc tracks
nearby.  The ferrite cooling channels and cooling lines in the electromagnet
were cleared, and the arc tracks were smoothed with buffing. The rf fields in
the long cavity region between the outer conductor and the permanent magnet
were also large enough to cause arcing damage.  We are analyzing several
options to mitigate the RF fields in this region.

Pending repairs to the FFT, the E-port external transmission lines and matching
system have been reconfigured to use the motor-driven phase shifter and stub
tuner elements that were previously employed for this antenna. We plan to
verify the operation of the E-port antenna during plasma operation this week.


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

Progress on the transmitter protection system (TPS) upgrade continues.  The
klystrons were energized and operated with ~5 kW RF output in the first hot
test of the TPS upgrade.  The collector over temperature system (COTS)
real-time calculation of the collector temperature is behaving as anticipated
for the measured beam voltage and current.  Changes to the high voltage ground
wiring, modifications to some filter capacitors, and changes to the TPS
firmware have been required during commissioning of this major hardware
upgrade.

Diagnostics
-----------

Following an extensive qualification process, the upgraded Thomson scattering
lasers were steered into the cell last week and aligned through the C-Mod
vessel. On Thursday the vessel was partially filled with argon to allow for
the collection of Rayleigh scattering signals, enabling initial tests of data
acquisition timing. Further tests , and an initial round of calibrations, are
planned to proceed during plasma operations this week.

During last week's maintenance period, we investigated and repaired a problem
with the high frequency channels of the FRCECE high temporal and spatial
resolution ECE diagnostic. A waveguide was found to have been displaced from
its socket on the air side of the vacuum interface so that it no longer viewed
the plasma. The waveguide was reseated. Preparations were made to recalibrate
the high frequency channels during upcoming plasma shots. The low frequency
channels were recalibrated during the previous week.

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

Paul Bonoli and Steve Wukitch sat on a committee to review and assess the
DIII-D Fast Wave ICRF System at a meeting held at General Atomics on January
12, 2012. Paul traveled to GA for the meeting and Steve attended the meeting
via remote videoconference.

Miklos Porkolab attended the Liu Chen 40 Year Anniversary Symposium at UC
Irvine, Jan 12,13, and gave an invited talk: "Gyrokinetic analysis of the
Linear Ohmic Confinement Regime in Alcator C-Mod. "

John Rice attended the CMTFO Winter School at UCSD Jan.9-10 where
he gave a lecture on C-Mod rotation and LOC/SOC results.

As part of MIT's Independent Activities Program (IAP), the PSFC brought in a
number of outside speakers.  Two of these, Thomas Zurbuchen (U. Mich.) and
Brian Wirth (U. Tenn.) took the opportunity to interact with members of the
C-Mod research team on topics concerning plasma wall interactions.
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