From: IRBY@CMOD.PFC.MIT.EDU
Subject: Alcator C-MOD Weekly Highlights
Newsgroups: sci.physics.plasma
Organization: MIT


Alcator C-MOD Weekly Highlights
March 18, 1997



Last Saturday the upper dome was lowered into place, and each of
the 48 drawbars was tensioned to the 500,000 lbs required to support the
forces generated primarily by the TF magnet. Now that the machine proper
is complete, we are working to install the curved bus, TF bus, horizontal
ports, cooling lines, RF antennas, and invessel components. In
addition, we have continued a wide range of continuity, ringing, and
resistance tests on the magnets and coaxes. The bus tunnel has been moved
back into position, and many of the tests that have been performed in the
experimental cell, will soon be conducted from the power room so that other
bus components and diagnostics can be tested.
Invessel work is going quickly. The upper ceiling modules have
been reinstalled. These modules were modified to accept the new
inboard periscopes. Gas capillary tubes have been repaired and in one
case relocated. Studs have been added to support the new invessel
telescope and the conduit for the new edge XUV diode array, and to increase
the stability of the TTCI mirror mount. Coaxes for the full limiter probes
have been reinstalled. Cables for the inner divertor probe array have also
been reinstalled. This last installation was required before some of our
disruption/halo diagnostics could be put back into place. Modifications to
the wall tiles required before installation of the new RF probes can proceed
have been completed.
The tangentially viewing XUV diode arrays are complete and are
undergoing final testings and alignment. The edge array, already installed
invessel inside the full RF limiter between F and G ports, will measure
radiated power at the edge of the plasma at the midplane. This 19 channel
diode array will have a nominal 2 mm spatial resolution and span approximately
4 cm of the edge plasma. The second array, with a 16 channel detector
installed in the same housing as the core foil bolometers, will look at
the core plasma, with a nominal radial resolution of 1 cm. Both arrays are
capable of a frequency response greater than 100kHz. Since these new arrays
are insensitive to neutral particles, they will, in combination with the
foil bolometer array, provide new information on the power loss due to
charge exchange neutrals.
Work continues on the installation of the ACCEL supply for the DNB.
A controller for the new supply has been selected and modifications to
this unit are now underway. A method for coordinating the ACCEL supply
turn-on with the MOD/REG timing has been chosen to minimize the voltage
drop across the MOD/REG tube. The implementation of the control system
can now proceed with this strategy in mind. Analysis of the oil for the
ACCEL supply and for the filament/bias supply has been arranged. CAMAC
equipment for DNB control, and a temporary support for the beamline
to be used during testing have both arrived from the University of Texas.
The power systems group continues to ring out the power supplies.
The OH1 shakedown has been completed. The regulator, gates, crowbar, and
all fault detection circuitry have been checked. The OH2 upper and lower
regulators have also been checked, and we are beginning work in the converter
and crowbar cabinets.
Crowbar trigger circuits for transmitters #3 and #4 have been
completed. The water supply for transmitter #3 FPA has been connected.
We are fabricating transitions and flanges for the FPA anode cooling pipes
for transmitter #4. The final assembly of these components will be done
at PPPL. John Gumpus is visiting this week from PPPL to continue his work
with us on the new RF transmitters.
Mark May from the Johns Hopkins University was at C-Mod in
preparation for the installation of the new XUV divertor monochromator and
for small modifications of the core plasma "Moly Monitor". Ben Welch
and Jim Weaver are here from the University of Maryland directing
installation of there spectroscopy diagnostics. G. Cima from the
University of Texas was here discussing ECE diagnostics.
Amanda Hubbard was at PPPL last week serving on the selection
committee for the National Undergraduate Fellowship program in Plasma
Physics and Fusion Engineering. Bruce Lipschultz was in San Diego
at the ITER Divertor Database meeting. Earl Marmar participated in the
6th meeting of the ITER expert group on plasma diagnostics held
at the Naka Joint Work Site in Japan.