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
January 17, 2000


Good progress was made on several fronts over the last week. Work on the
DNB, RF antennas and transmitters, and invessel activities continued to be
our primary interests.


Engineering:

The DNB was operated in its test cell beginning January 7 and continuing
through January 13. The tests included more than 200 shots with
varying combinations of power supplies. A neutral beam was generated on a
majority of shots and at will. The maximum accelerating voltage attained
for the demand interval of 90 ms was 45 kV. Currents above 4 Amps were
generated for voltages above 40 kV. The beam is operating as expected and
is now ready to be installed on C-Mod. This work completes on schedule
another major DNB milestone.

The boron nitride tiles to be installed on the E-port antenna have
completed their bake. They have been stored in our clean room in
a low humidity atmosphere and will be installed as one of our last
invessel operations. The J-port antenna is very nearly complete with only
a few bolts remaining to be installed. Machining of the inner divertor module
for the new rangefinder view has been completed. A great deal of work is
still going on in our shop for invessel components, including parts for
alignment jigs, emissive and flux probes, CXRS telescopes, the DNB aperture,
pressure sensors, and mirror mounts and housings.

All four FMIT water systems will be fully assembled and under test this
week. Modifications to the FMIT#2 input cavity have been completed and
installed. The 2274 tube recently returned from CPI has also been installed.
Installation of the output cavity with improved RFI chokes is in progress.

Work continues on the TMX Power Supplies. The 15 volt power supplies have
been tested and are all operating correctly. The interface wiring to the
new gate boards has been installed and tested. Hi-potting of the SCR
bridges and testing of the SCR gates continues. The new gate drive
prototype circuit has been tested in place with only some minor changes
required. The documentation for the new board is in progress.


Physics:

Dr. Alan Glasser (LANL) has provided us with a copy of version 3.10 of his
MHD stability code DCON. The present version of DCON evaluates the
Mercier criterion D_I > 0 for unstable localized ideal interchange
modes; the related criterion D_R > 0 of Glasser, Greene, and Johnson for
localized resistive interchange modes; the criterion C_A < 0 for ideal
MHD ballooning modes in the limit of large toroidal mode number; the
generalized Newcomb criterion for the internal ideal MHD stability of
one low toroidal mode number; and the plasma, vacuum, and total response
matrices and their eigenvalues for determining free-boundary stability.
A future version of DCON will treat resistive instabilities. Dr. Glasser will
be working with C-Mod personnel to interface the DCON code to the MDSplus\
data acquisition and analysis system.


Travel and Visits:

John Rice attended the JSPF meeting in Sendai from Nov.23-27 and presented
an invited talk on 'Toroidal Rotation in Alcator C-Mod Plasmas'. From Nov.27
to Jan.5 he participated in ongoing experiments at LHD in Toki, and
worked on analysis of the 'Breathing Plasma' with Byron Peterson.

Stefano Bernabei, Douglas Loesser, Norton Bretz, Bob Cutler, and Dave Johnson,
all from PPPL, visited MIT last week. Stefano Bernabei and Douglas Loesser
came to discuss plans for the LH experiment. Discussions on what ports
to use, how to best implement the launchers, and scheduling took place.
Norton Bretz and Bob Cutler visited to bring up the external optics and
electronics for the MSE diagnostic. They also worked on the invessel
shutter for this diagnostic as well as a solution to some interference
problems at the port. Dave Johnson visited to take some optical components
back to PPPL for use on NSTX; they are no longer needed for C-Mod.