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


Alcator C-MOD Weekly Highlights
February 25, 1997



Several days were lost on the reassembly schedule last week after
an inspection revealed some spring plates to have been installed incorrectly.
These plates insure that proper pressure is applied to the TF finger joints,
which is critical to magnet performance. The machine was lifted from the
lower dome and placed back on the assembly stand for access. Following
re-installation of the spring plates and another complete set of inspections,
the machine is now back on the lower dome.
We continue to make progress on the DNB installation. Riggers have
been contracted to move the Tara gyrotron power supplies from their
current location to the power room. In preparation for the move, we have
drained the oil from the supplies and cleared the area around the
supplies for better access. The beamline itself has now been moved to a
new lab area where it will be assembled and intial tests begun.
A great deal of work was done last week preparing the EF4 supply for
the next campaign. The new overvoltage board was installed and tested,
as was the latch circuitry that interfaces with the PLC. Fuses and gates
have been checked on the converter and crowbar circuits. The new fast type
I fault circuit has also been installed. The supply has been hi-potted
and the regulator has been checked (integrator, clamps, faults, feedback
V and I, lockout etc). Cabling has been replaced and rerouted in some
locations to improve noise immunity and eliminate possible ground loops.
The first crowbar trigger circuit for the new transmitters is
complete. Three other units are being fabricated. Switchgear for the
#3 transmitter is complete and tested, and we are completing work on
the switchgear for the #4 transmitter. We continue to work on control
circuitry for the new transmitters, and are working with PPPL to complete
the new coax runs.
The prototype cryopump has been installed inside a mockup of the
outer divertor on our vacuum test stand. An extensive set of pumping tests
have been carried out. The pump easily handles gas loads larger than those
expected on C-Mod. Pumping speeds of 1000 l/s have been measured during
deuterium gas puffs with peak pressures of 25 mTorr.
Analysis of C-Mod data continues. Toroidal rotation velocities
greater than 1e7 cm/sec (200 kR/sec) have been observed in the highest
H-factor H-mode plasmas (ICRF only), in the co-current direction. When Ip
is reversed, the rotation also reverses direction. Spatial scans indicated
the rotation velocity is highly peaked near the magnetic axis. These
measurements were made by observing the Doppler shift in X-Ray line
radiation from highly stripped Argon.
Mike McCarthy from PPPL visited last week to discuss upgrades
to the reflectometer system. Schedules and work plans were developed for
MIT and PPPL with the goal of installing the reflectometer for the next
run campaign with improved fluctuation measurement capability and frequency
stability.
Steve Wukitch went to PPPL last week to participate in mode conversion
experiments.