From:
irby@PSFC.MIT.EDU
Reply-To: IRBY@PSFC.MIT.EDU
Subject: Alcator C-Mod
Weekly Highlights
Newsgroups: sci.physics.plasma
Organization:
MIT
Alcator C-Mod Weekly Highlights
April 25, 2003
Plasma operation continued
Tuesday through Friday this week.
Commissioning of the LH klystrons made
excellent progress, and the
Lower Hybrid MIE Project can be declared
complete. Plasma
conditioning of
the ICRF antennas has begun.
Operations
----------
Machine
operations this week concentrated on plasma cleanup. Low
density plasmas were produced throughout the week as we
cleaned the
plasma facing surfaces and began reducing the amount of
hydrogen in
the discharges.
Startup reliability, which began at 50% on Monday,
was 86% by
Thursday. Cleanup and rf conditioning
of the rf antennas
will continue next week.
Physics
-------
On
Friday, the first run with the new non-axisymmetric control coils
in
operation took place. Early in the run,
low density discharges
showed evidence of locked mode activity. However, changes in the
density later
in the run made it difficult to assess the effect of the
coils. These experiments will continue when the
machine is better
conditioned, and probably with higher plasma currents
where more
robust locked modes can be produced.
Lower
Hybrid Project
--------------------
Eleven of the twelve
klystrons are now operational at power levels of
more than 200 kW and
pulse lengths of 1 s. Nevelle
Greenough, PPPL,
spent the week at MIT to help with the commissioning
effort.
Work has also continued on phase and amplitude control
electronics.
Fabrication has begun on PLC electronics required to
control the launcher
temperature regulation system, and positioning
equipment. The design of fixturing required to mount
the launcher in
our vacuum test stand is proceeding. A new clean room for working on
the
launcher vacuum components is being constructed in the rf lab.
ICRF
Systems
------------
Plasma conditioning of the ICRF antennas
was started this week. Both
D and
E-Port were conditioned to ~ 1 MW and ~20 kV.
J-Port reached
250 kW, but a fault in a low power relay and rf
preamp stopped
conditioning efforts until repairs can be made.
Diagnostic
Neutral Beam
-----------------------
The beam is again in
operation during C-Mod discharges with good
beam performance. All beam control software has been ported
to
Linux.
Travel and Visits
-----------------
Manfred
Bitter and Ken Hill, both from PPPL, were at MIT on
4/22-23/2003 to
discuss the installation of the NSTX X-ray imaging
crystal spectrometer on
C-Mod with John Rice and Earl Marmar.
The
spectrometer consists of a spherically bent crystal and a 10 cm
x 30
cm large position-sensitive detector and will provide radial
profiles
of the ion and electron temperatures, the toroidal plasma
rotation
velocity, and the ionization equilibrium.
Stewart
Zweben, PPPL, was at C-Mod 4/22-25 and helped prepare the Gas
Puff Imaging
diagnostic for the run. Initial data
was taken using the
two Xybion cameras, and nice images of the edge
turbulence structure
were obtained.
Steve Wolfe traveled to San
Diego to participate in the review of the
General Atomics proposal for
operation of DIII-D for the next five
years.