From:
irby@PSFC.MIT.EDU
Reply-To: IRBY@PSFC.MIT.EDU
Subject: Alcator C-Mod
Weekly Highlights
Organization: MIT
Newsgroups:
sci.physics.plasma
Alcator C-Mod Weekly Highlights
Jan 24, 2003
Physics
-------
The
new core Thomson Scattering (TS) polychromators became operational
during
the last run campaign and give reliable profiles of the
electron
temperature and density with ~10% accuracy. Both core
temperature and
density profiles match up well to the edge TS
data. The TS temperature is
systematically 10-15% higher in the core
region than that derived from the
ECE diagnostics. The absolute
calibration of the new core TS density was
made using ECE cutoff
data. Integrals of TS profiles mapped along TCI
chords are
systematically 10-15% lower than nl data; however, the
agreement is
better for the outer TCI chords. This result is consistent
with the
TCI inversion profiles, which are close to the TS density
profiles at
large radii but are too high in the core; possibly because
the
interferometer sees extra nl from the scrape-off layer. The
effective
charge derived from the VB and TS data is ~1 in most L-mode
discharges
and ~1.1-1.4 during H-modes.
Impurities are observed to accumulate in
the center of some ITB
discharges resulting in a Zeff of up to 2.5 in
the core.
Operations
----------
The
first of eight aluminum frames for the new field control coils was
completed
this week. Cable has arrived for
winding the first coil,
and the coil winding equipment has been set up in
the power room and
tested. We
expect to have the first coil completed next week.
Production of the
remaining coil forms has begun. Work is
nearly
complete on the power supply we will use for the initial control
coil
experiments. High power tests
of the supply into a dummy load is
expected next week. Data and Hybrid control system interfaces
and
software upgrades to support the new coils are also underway. A
drawing
of the new coils may be seen at
http://www.psfc.mit.edu/cmod/operations/EngImages/MACHINE/PF/correction_coils_side.jpg
We
continued invessel work this week.
Reassembly of the cryostat and
preparations for re-installation of
the vertical flanges also
proceeded.
Lower Hybrid MIE
Project
------------------------
At MIT work was delayed on the
high power klystron tests using the
HVPS as we work with the vendor to
update the crowbar fault detection
boards. Components are being fabricated that will support the
circulators
and dummy loads. Procurement plans for
the output
waveguide are being finalized.
Work continued on the phase and
amplitude control system, data
acquisition components, and serial
fiber optic links.
Good
progress continued to be made at PPPL on the LHCD launcher. All
heaters and thermocouples have been
installed on the shroud and
forward waveguide. The shroud and waveguide assembly were
subsequently welded,
and will be leak checked shortly.
Cleaning of
brazing residue off the ceramic surfaces is
progressing, with plans to
finish by 2/1.
Acid etching may not be required for final cleanup.
Microwave
transformers, slide bushings and radial motion rails have
been delivered
to PPPL. The radial motion mechanism is
assembled and
being tested. The
signal patch panel design is completed, and wiring
has begun.
ICRF
Systems
------------
Simulations of the J-Port antenna feedline
and straps continues in an
effort to model proposed changes needed to
increase the breakdown
voltages at critical locations. We also continued simulations of the
voltage
and current probes to be added to the D- and E-Port antennas.
The
simulations indicate that spurious rf pickup on the current probes
could
be reduced a factor of 10 by adding multiple slots in the
current probe
aperture.
We continue to develop improved fault detection and
control
electronics for the transmitters.
Travel and
Visits
-----------------
Stewart Zweben, PPPL, was at MIT this
week to discuss plans for the
Gas Puff Imaging diagnostic and for a
possible mini-proposal on H-mode
control.
Martin Greenwald
traveled to PPPL for the NSTX PAC meeting.
Presentations focused on their
5 year proposal.