From: IRBY@PSFC.MIT.EDU
Reply-To: IRBY@PSFC.MIT.EDU
Subject: Alcator C-Mod Weekly Highlights
Organization: MIT
Newsgroups: sci.physics.plasma


Alcator C-Mod Weekly Highlights
January 24, 2000


Work continued on the DNB, RF systems, and invessel work last week.
The invessel work has become particularly important as we approach
the scheduled mid February pumpdown.


Engineering:

All work on the DNB in the test lab has been completed, and we have
begun to move the DNB equipment into the C-Mod cell. The move is going
smoothly with some major beam components already moved to the cell.

J-port antenna has been installed. The protection tiles were aligned
without modifying the tiles. Measurements will now be taken to
document the antenna location relative to the central column.
The E-port BN top protection tiles installation preparations have been
completed. The tiles should be installed this week.

Modifications to FMIT#2 input cavity and high voltage connection have
been completed. The input cavity modification is a cut back and
tapering of the isolation capacitor teflon. The high voltage
connection modification includes the replacement of two sets of two
stacked 25 kV capacitors with two sets of 40 kV and 750 pF capacitors
and 5 uH inductors. The cavity was successfully hi-potted to 40
kV which is greatly improved over the previous design. This upgrade should
allow the transmitter to operate at the highest plate voltage and
allow higher power operation. FMIT#1 input cavity has also been
modified. The reassembly has been slowed because of a broken ferrite
ring. Replacements have been found and are on order and this delay will
not impact the overall schedule for restarting C-Mod operations.

Invessel work included machining of components needed for the reflectometer
invessel alignment and the CXRS poloidal view telescope. The baking
of numerous components to prepare them for installation was completed
over the weekend. As mentioned above, work on all three ICRF antennas is
nearly complete, and RF installations will present no problem for our
pumpdown schedule.

We continue to make some upgrades to the bus tunnel and LN2 sump. These
changes will improve the seals and reduce the possibility of water vapor
penetration into the bus tunnel. The LN2 manifold relief valves have
been tested and a new manifold added to divert any LN2 that escapes from the
valves down into the sump. We have also made some improvements to the heater
system that maintains the vacuum vessel near room temperature when the
magnets are cooled down to LN2 temperatures. During the last campaign
water condensation on some of the heater cables made its way into the
heater connectors and damaged them. These connectors have all been
checked out, repaired where required, and covered with a water tight seal.


Travel and Visits:

Miklos Porkolab attended the 10th International Conference on Plasma Physics
and Controlled Nuclear Fusion (ITC-10) in Toki, Japan, January 18-21.
He also was invited to make a special public lecture to the citizens of Toki
on Saturday, January 22. The title of his 1 hr presentation was:

"Contribution of Fusion to Solve the Energy Problem and
the Environmental Issues in the World"

The lecture was translated simultaneously into Japanese by Prof. Watari
of NIFS and the University of Tokyo.

Robert Granetz attended a US/Japan workshop on MHD stability at high beta,
held at the JAERI Naka site. He presented some of the initial results of an
MIT-JAERI collaboration on disruption neutral point studies in Alcator C-Mod.
Presentations from Japan included not just JT-60U, but also the recently
commissioned Large Helical Device, which apparently has significantly better
energy confinement than predicted by the empirically-derived stellarator
scaling law. Detailed studies of Mercier stability (high-k interchange modes)
are being carried out in LHD, but so far, MHD modes do not limit confinement
performance. Several tokamaks (JT-60U, ASDEX-U, TCV) reported that
neoclassical tearing modes are sometimes seen even for beta_p down to 0.7,
which is within the range of values that have been achieved on Alcator C-Mod.
Therefore, we should go back through our MHD data to determine whether or not
such modes have occurred in our machine.

Steve Wolfe participated in the meeting of the DIII-D Advisory Committee (DAC)
at General Atomics in San Diego last week. He also continued discussions
regarding the EFIT code and MDSplus with Lang Lao, Qian Peng, and
Jeff Schachter.