Alcator C-Mod Weekly Highlights
			     July 7, 2008
				

FY2008 weeks of research operations:
    Target: 15 weeks
    Completed:  15.7 weeks


Physics
-------

An updated numerical model for deuterium diffusion and retention in
Molybdenum was applied by Dennis Whyte to C-Mod retention in the
divertor. It was found that the C-Mod retention results of ~1% D fluence
retained are not inconsistent with the expected permeation of the D fuel
to damage sites, and that the retention would be expected to show signs
of saturation, but only after several hundred discharges.  Also, a
simple examination of millisecond timescale disruption heating showed
that the rapid release of the D from deep in the molybdenum was
possible, as has been seen in experiments on C-Mod.


Operations
----------

The retaining cylinder was removed on Monday exposing the vertical TF
arms for the first time since the last inspection in 2002.  Later in the
week, the cover plates protecting the outer sliding joint fingers and
spring-plates were removed.  The spring-plates apply pressure across the
joint so that contact is maintained even during the highest C-Mod field
and plasma current operation.  Visual inspections of these areas
indicated they were in good condition.  Careful measurements were made
of the sliding joint resistances.  These data indicated the joints were
in good condition electrically, with resistances close to those measured
during the last re-assembly.  On Thursday, approximately 25% of the
spring-plates that secure the TF core fingers to the upper TF arm
fingers were removed using an hydraulic extraction tool.  These
components were also in good condition, and measurements of the
extraction force indicated they had maintained proper pressure on the
feltmetal. A borescope inspection down through the spring-plate slots
showed no evidence of degraded feltmetal.

Preparations for the alternator inspection, which is to begin in August,
included removal of power cables to the 2000 HP drive motor.  Exciter
bus-work was also removed.


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

The new IPA 10 kW amplifiers will be shipped to MIT soon.  Work
continued on the rf connections, cooling, and power service for this new
system.

We now have several quotes in house for the rf feedthroughs for the new
ICRF 4-strap antenna.  Analysis continued on the antenna rf simulation
of power and phase balance in the straps.


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

Work continued on rf simulations of the 4-way splitter.  The latest
simulation compensates for coupler geometry and maintains a more
constant phase along the four columns.

Testing of the CPS (coupler protection system) interface software was
successfully completed last week.


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

Martin Greenwald traveled to Dallas, Texas to attend a meeting of the
FESAC panel on alternate concepts last week.

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