From: IRBY@CMOD2.PFC.MIT.EDU
Subject: Alcator C-MOD Weekly Highlights
Organization: MIT
Newsgroups: sci.physics.plasma


Alcator C-MOD Weekly Highlights
March 25, 1997



Reassembly of Alcator C-Mod continues. All horizontal port
extensions have been installed and helium leak checked through their
secondary seals. As mentioned last week, the port extensions had to be in
place before some invessel installations could proceed. Installations
such as the divertor prototype cryopump and the JHU divertor spectrometer
are now progressing rapidly. The rf antennas and feedthroughs have
also been installed. Work on the curved bus and coaxes is nearly complete,
as is installation of all the LN2 cooling lines. The magnet cooling PLC has
been brought back into operation so that all the LN2 valves could be
checked for proper operation, and cooling paths verified. All heaters,
thermocouples, OH flux loops, and OH position sensors have been checked for
proper operation now that the tokamak is complete. The final hi-pot and
ringing tests required before the machine is sealed inside the cryostat
are underway. The lower cryostat is ready to be raised into position, after
which the vacuum hardware on the lower vertical ports can be installed.
The torus pumping station has been moved back into the cell and installed
on the port extension.
The DNB fabrication continued with design work on the ACCEL supply
control system, and successful no-load tests on both the ACCEL and the
Arc/Filament/Snubber supplies. We can now refill these supplies with oil
and begin filtering and degassing it in preparation for bringing them
back online.
Work continues preparing the magnet power supplies for
operation. OH2 upper and lower converter cabinets have been checked
and made ready for operation as have the IOC/current feedback boards.
The EF1 upper and lower converter cabinets and IOC/current feedback
boards were also checked and are ready for operation. In addition,
crowbar firing levels have been adjusted to specification.
The crowbar trigger circuits for the new transmitters have been
tested and are being calibrated. Preparations continue on the
crowbar cabinets with installation of the new trigger circuits expected
soon. Work continues on water cooling, control, and transmission
systems. Safety interlocks and bias and filament power supplies have
been tested on transmitter #4. The coax components fabricated at PPPL
have arrived.
During the past month, the collaborators from UT-FRC have been
concentrating on preparations for the spring campaign. Design of the
turbulence probe diagnostic was completed, and the vacuum hardware required
for C-Mod pumpdown was received at MIT along with all required CAMAC
equipment. The ECE radiometer which will be used by the Auburn/MIT/UT
collaboration for electron temperature profiles and fluctuations is now at
MIT, also with all its required CAMAC equipment. Testing of components
for two DNB diagnostics, BES and CXRS, is planned. The equipment for
both of these is in the final stages of preparation at UT.
Work continues on several diagnostic systems. Thermoelectric coolers
for stabilizing the reflectometer Gunn diode frequencies arrived at PPPL and
layout drawings have been generated for installing them at MIT. We have
begun to discuss with PPPL software and hardware changes that should much
improve the operation of the reflectometer system. Newly recoated optics have
been installed on the two-color-interferometer diagnostic, and improvements
made to the collimator mounts. This system is being brought back on line
now so that alignment can begin as soon as we have access to the torus. A new
95 microgram Cf252 source has arrived from Oak Ridge. It will replace the
old source which had decayed to the 18 microgram level. The new source
will allow us to achieve a good signal-to-noise level during our neutron
calibration in much less time. In order to measure the D0 Lyman alpha line,
molecular deuterium lines, and the strong carbon and nitrogen lines
above 1200 Angstroms, the long wavelength end of the spectral range of our
VUV spectrograph is being extended from 1100 to 2200 Angstroms. In
addition, an in situ calibration facility for the spectrograph has been
developed and is being installed and tested.
We continue to analyze spectroscopic rotation data. The argon
toroidal rotation radial velocity profile has been used to determine the
radial electric field during better H-mode and enhanced D-alpha H-mode
discharges. At r/a = .3, the field is 300 V/cm, about a factor of 2 larger
than the ion diamagnetic term.
Mark May and Sean Regan are here this week from JHU to complete
installation of their divertor spectrometer.
Bob Granetz was in Moscow last week for the ITER MHD Expert Group
meeting. Earl Marmar was in San Diego for a meeting of the FESAC ITER
review committee, which was held at UCSD.