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
28, 2001
All C-Mod invessel work was completed on Friday
evening, 4/27. Following
inspections,
documentation, completion of the invessel checklist, and a final
wipe down
of the chamber, one of the two access port flanges was installed.
On
Saturday, 4/28, the final access port was sealed and Alcator C-Mod
was
pumped down. The cryostat is being purged with nitrogen gas in
preparation
for liquid nitrogen cooldown of the magnets.
Approximately the
next three weeks will be devoted to baking the
vacuum vessel, ECDC wall
conditioning, vacuum conditioning of the rf
antennas, and bringing power
systems and diagnostics back online.
Work
this week was focused on completing installation of the
J-Port antenna and
preparing the vessel for pumpdown.
Progress was
also made on DNB related diagnostics, the Lower Hybrid
MIE Project, and
preparations for operation of the ICRF
transmitters.
Physics
-------
Stewart Zweben
was on-site for the entire week, analyzing data from the
turbulence
imaging diagnostic. This diagnostic has successfully acquired
many ~1
microsecond snapshots of the edge emission. He also discussed
future plans
for this diagnostic and our plans for comparing the
experimental results
with turbulence modelling.
ICRF
Systems
------------
Installation of the J-Port antenna was
completed late this week. Careful
measurements
have been made of the positions of major antenna components.
The B-dot
probes located in the antenna boron nitride protection tiles are
installed
and calibrated. A picture of the
antenna can be seen at
http://www.psfc.mit.edu/cmod/operations/EngImages/INVESSEL/2001/Close_Up_Survey/P0001531.JPG
Note
the new boron nitride septum at the middle of the antenna added to
break
up field line connection paths along the face of the antenna. New
boron nitride tiles have also been
added to completely cover moly
surfaces that showed arc damage during the
last run period.
The FMIT#3 and FMIT#4 ICRF transmitters have been
re-tuned for operation
at 78 MHz.
At least 2 MW of power has been delivered to the dummy load from
each
transmitter. PPPL has supplied us with
spreadsheet models for more easily
tuning these transmitters, as well as
more up-to-date drawings of the cavities.
The testing of all phase
balance boards and their associated arc phase
modules has been
completed.
Lower Hybrid MIE Project
------------------------
The
Lower Hybrid launcher design is continuing to proceed smoothly
at
PPPL. Procurements have been placed for
copper plating of the
prototype coupler and for fabrication of larger
corner radius ceramic
windows. An
RFQ is being generated for the large oval shaped bellows
which allows
radial coupler motion with respect to the plasma. Brazing of
additional coupler prototypes for testing and
optimization is scheduled
for the upcoming week.
Mechanical
drawings have been generated and released for fabrication of the
transmitter
protection system racks. Requisitions
for electrical, mechanical,
and PC board components are being issued. The transmitter key-inlock
configuration
drawing has been generated and is undergoing the review
process. A dialog with the key manufacturer, the high
voltage power
supply vendor, and MIT is ongoing to ensure a seamless
key-interlock system.
Tests of the SFOLs and the active feedback
loop continue. A clock
synchronization
problem is being resolved.
DNB
---
The
DNB duct is fully installed with the new pressure gauges, and
windows for
the H-alpha monitors have been attached.
The external H-alpha
monitors are tested and ready for installation
as needed. A DNB
cryopump
compressor failed, but has been replaced, tested, and is ready
for
operation. The beamline is again under
vacuum.
Inner Divertor
--------------
All
inconel 718 bolts needed to secure the inner divertor tiles are now
in
house, and undergoing the QA process.
Vendors indicate that all girdle
plates will be in house by the end
of next month. We are proceeding
with
fabrication of a very accurate inner wall mockup that will be used to
test
inner divertor components before installation.
Power
Systems
-------------
Work continues updating power system and
alternator documentation to reflect
upgrades to the commutation banks and
hi-yard instrumentation we have made over
the last few weeks.
Diagnostics
-----------
At
PPPL, Larry Guttadora has started checkout and adjustment of power
supply
modules for the two higher frequency mm-wave channels that
are to be added
to the C-Mod reflectometer for density and fluctuation
measurements
farther up the edge pedestal.
The installation of the new CXRS
shutters was completed this week.
A picture of the shutters invessel can
be seen at
http://www.psfc.mit.edu/cmod/operations/EngImages/INVESSEL/2001/Close_Up_Survey/P0001558.JPG
Travel
and Visits
-----------------
Miklos Porkolab attended the
Memorial Service in Princeton on April 23
in honor of Tom Stix, who passed
away last week. He was the pioneer
in
wave propagation and RF heating in magnetically confined plasmas. His
passing is a great loss to the
whole fusion community.
We had several visitors from PPPL at MIT
this week. Chris Brunkhorst
visited
from Monday to Wednesday and was a great help in completing the
final tune up
of the FMIT#3 and FMIT#4 transmitters. Martha Redi was here on 4/24, and
discussed
various aspects of the new ITB discharges and modeling of C-Mod
transport
with Catherine Fiore, Tunde Fulop, John Rice, Paul Bonoli, and Steve
Wolfe. Stewart Zweben also visited as noted
above.
Yves Peysson (Cadarache) visited this week to discuss a
collaboration
to develop an x-ray camera for C-Mod. He also gave a seminar on recent
lower
hybrid current drive results on Tore Supra.
Amanda Hubbard attended
the International Workshop on Physics of Internal
Transport Barriers, Edge
Pedestal, and Steady State Operation in Tokamaks, in
Garching,
Germany. She gave talks on C-mod
pedestal and ITB results, and also
made plans for a comparison experiment
with ASDEX-Upgrade on Type II elms
and EDA modes.