Alcator C-Mod Weekly Highlights
			July 9, 2007

FY2007 weeks of research operations:
     Target: 15 weeks
     Completed: 9.3 weeks

Operations
----------

Last week was a scheduled maintenance week, with no plasma operations planned.

On Monday, July 2, experiments were carried out to characterize ECDC
boronization film deposition using the quartz microbalances (QMB) on the
Surface Science Station.  The radial pattern of deposition was measured with
and without vertical field applied. The deposition with the vertical field
exhibited a steeper profile, peaked at the upper hybrid resonance. It was
found that the deposition rate had a complex dependence on vessel pressure and
the gas feedthrough rate.  At higher pressures, a maximum deposition rate ~ 3
nm/ minute was found, approximately 3-4 times that measured with the lower
pressure used in previous runs this year, while net erosion was observed at
still lower pressures.

We continue to work with our power utility to resolve the issue of increased
impedence on our 13.8 kV AC line. We have also taken steps to shift the 480V
control and intermediate power rf amplifier stages in transmitters #3 and 4
from a circuit fed by this line to another line. This modification, similar to
the configuration already in use for FMIT#1 and 2, should reduce the impact of
the utility change on the J-port ICRF system.

Plasma operations at C-Mod are planned to resume this week.


Milestones
-----------

C-Mod successfully completed its third quarter targets (sub-milestones) on
schedule. These were:

1) Investigate Lower Hybrid RF in L- and H-mode plasmas, including study of
combined Lower Hybrid RF and Ion Cyclotron RF. Third quarter target: Operate
LHRF into L-mode and H-mode plasmas, and investigate combined LHRF and ICRF
(June 30, 2007).

2) Investigate particle and density control with the new upper divertor
cryopump. Third quarter target: Investigate particle and density control in
tokamak plasma operation. (June 30, 2007).

Physics
-------

A real-time detection algorithm for locked modes has been tested against data
from the 2006 C-Mod experimental campaign. The algorithm, which is based on
identification of effects on the sawtooth period and amplitude observed by the
electron cyclotron emission (ECE) diagnostics, exhibited a 90% success rate in
identifying locked modes. This work, being carried out by an MIT graduate
student, is envisioned as supporting a real-time mitigation scheme for locked
mode induced disruptions which could be implemented in the C-Mod digital plasma
control system (DPCS).


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

Inspection and documentation of the "jungle gym" waveguide assembly
continued. Water loads were removed from the waveguides and tested; no leaks
were found. The jungle gym as been reassembled and the lower hybrid system is
ready for operation.

Design work for the next Lower Hybrid launcher system continued.

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

Ian Hutchinson, Ron Parker, Amanda Hubbard, and Steve Wukitch took part in the
34th EPS Conference on Plasma Physics, in Warsaw, Poland, last week. Hubbard
also attended a meeting of the Nuclear Fusion Board of Editors.

Prior to the EPS Meeting, Steve Wukitch traveled to Lausanne, Switzerland to
visit Mark Henderson of TCV regarding technical aspects of implementing a 170
GHz electron cyclotron system on C-Mod, to follow up on discussions at the RF
topical conference in May.  Wukitch then visited Riccardo Maggiora of
Politecnico de Torino regarding implementation of TOPICA and antenna
design. He also traveled to Advanced Ferrite Technologies in Stuttgart Germany
to discuss the design of new 4.6 GHz circulators and ferrite tuners.

Dennis Whyte presented an invited talk "Measuring and Controlling
Plasma-Surface Interactions of Low-Z Elements in a Tokamak Fusion Device" at
the joint meeting of the 17th Internal Vacuum Congress and 13th International
Conference on Surface Science held July 2-6 in Stockholm, Sweden
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