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
September
14, 2001
Work continued on the machine inspection this
week. Progress was
also made on
the new inner divertor, and lower hybrid and ICRF systems.
Physics
-------
Analysis
of the turbulence observed in the plasma edge with the PPPL Gas Puff
Imaging
diagnostic is continuing. Three types
of modeling efforts are being
pursued.
A direct image analysis of the 2-D experimental data attempts
to
extract spatial correlation lengths, k-spectra, fluctuation levels,
"blob"
structure and motion, and other pertinent information.
Darren Stotler is
working on modeling of the relationship between
light emission images and
the underlying density and temperature
fluctuations using the DEGAS 2
code. Klaus Hallatscheck (IPP) and
Barrett Rogers (Dartmouth) are performing theoretical modeling of the
C-Mod edge turbulence from first-principles models, e.g. Drift-Ballooning
Mode and Non-Local
Edge Turbulence codes.
J. Snipes presented ideas at our weekly
physics meeting for where a second
set of Active MHD antennas could be
placed toroidally in relation to the
first set, which will be mounted in
the GH sector. Conflicts with
antennas,
glow discharge electrodes, and other diagnostics limit the
location of the
new set of antennas to a toroidal region about 72 degrees
away from the
GH MHD set.
Operations
----------
Resistance
measurements of the TF sliding joints were carried out this
week as part
of the machine inspection. The
resistance of all the lower-outer
joints were measured and detailed
potential drop maps were made of selected
joints. These measurements together with careful
analysis will continue for
several days next week.
The
equipment needed to remove the spring plates holding the joint fingers
together
has been assembled and tested. We
expect to begin pulling selected
TF arms and legs off the machine early
next week.
Lower
Hybrid MIE Project
------------------------
Work on the C-Mod
Lower Hybrid launcher is progressing well at PPPL.
With the determination of the position of the
H-taper and of the
diagnostic probes, the last details of the 3 dB
splitter and front
extension are complete. The design of the full scale three-channel
test fixture is
complete and fabrication drawings are being created.
It will be used to
test the vacuum integrity under the specified
conditions and for all the
high power tests of the non-standard
waveguide components, probes and
cross talk.
One set of TPS boards including the front panels have
been completed and
wired to the PLC I/O control rack. Power-up test of the boards have begun
and
bidirectional I/O between the TPS and the PLC have been verified.
Holes
have been bored through the power room wall for the HVPS interface.
Installation
of the HVPS interface box is progressing.
Fabrication of the
HVPS dummy load continues in our shop. Development of fiber optic links
for
the LH project also continues.
Analysis
of the I/Q detectors that will be used to measure the relative
phase of
the klystrons continued this week and indicated only a 5 degree
variation
in phase over a factor of 20 range in signal level.
We continued
work on the lower hybrid low power microwave rack layout.
Contractors
continued the site modifications required for the LH project.
Coring of
the northeast cell wall for the HVPS power and control cables is
nearing
completion. Rails to secure the HVPS
supply are being installed on
the new concrete pad in the hi-yard. Specifications for the water system
sensors
and controls are being reviewed by C-Mod engineers as the 8" and
6"
supply line fabrication continues in the power room.
ICRF Systems
------------
We
continued developing more detailed models of the D, E, and J-Port
antennas. Work also continued gathering information
for a transmitter,
transmission, and coupler systems model.
Inner
Divertor
--------------
We are in the process of fitting-up the
entire complement of inner divertor
components invessel. A picture of this process can be found
at
http://www.psfc.mit.edu/cmod/operations/EngImages/Inspection_2001-2002/Disassembly_Assembly/part2/P0002068.JPG
The
fitup will allow us to determine if any processing of the plates
is
required to ensure the proper contact with the inner wall needed to
meet
strength and thermal conduction requirements.
Also, any conflicts with
inner wall diagnostics will be
addressed. After the fitup is
complete
work will begin on installation of the new studs. Techniques needed to
efficiently
install and test the new studs are being finalized.
Trips and
Visits
----------------
Dave Terry and Willy Burke met this
week via teleconference with Nevell
Greenough, Elmer Fredd, Chris
Brunkhorst, and other PPPL engineers, to
discuss demodulator and phase
detector designs. We hope to pool
our
knowledge on these systems and develop a new design capable of
handling
measurement and control tasks much more effectively than
the current designs
we both use.
Dave Terry traveled to Opal-RT in Canada for a
demonstration of their
RT-Lab software.
He discussed three of our possible applications with them,
including
the Lower Hybrid, Fast Ferrite Tuner, and Hybrid Computer systems.