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 22, 2001


We continued work on the J-port antenna, fixes to invessel diagnostics,
and DNB development last week.


ICRF Systems
------------

The PPPL J-Port ICRF antenna was removed from inside the vacuum vessel last
week for a careful visual inspection and relatively minor modifications.
However, arc damage found between the stripline feeds and the support
septum will require a more extensive cleanup and repair effort than planned.
These problems develop in areas where we have an along-field (E parallel
to B) path between the stripline and septum ground. Areas where the stripline
arc paths are predominantly across the magnetic field showed little or no
indications of arcing. Therefore we are investigating changes to the stripline
that will keep the breakdown paths perpendicular to the magnetic field and
therefore magnetically insulated.

A meeting was held here at MIT on Friday, 1/19, with our collaborators
from PPPL, to discuss changes to the antenna. Another meeting will
be held on Friday, 1/26, to finalize the design and discuss scheduling.


Lower Hybrid Project
--------------------

The procurement process for the second largest purchase of the program, the
circulator, is progressing. Proposals were received from three vendors at
the end of December. A source selection committee consisting of Monty Grimes
here at MIT, the head of the RF group at Bates Laboratory, and an outside
consultant is in the process of reviewing the proposals. The vendor
selection process should be complete by the end of the month. The largest
largest item being purchased for the project, the HV mod/reg supply, is on
schedule for an October 2001 delivery.

A design review of the Lower Hybrid project is scheduled for February 7th
and 8th. Preparations for this review are currently underway.

Modifications to the first klystron cart continue. This cart is the first
of three that will be installed in the cell following the current run
campaign.

Design of the klystron protection and control circuitry is being finalized.
In addition, the two channel analog-to-serial fiber-optic transmitter board
was prototyped and some testing has started, the design of serial-to-digital
analog fiber-optic receiver board is near completion and a prototype board is
being built, and work on the LH active controller continues. A test fixture
and cables for LH vector modulator and I-Q detector tests was finished
last week.


DNB and Related Diagnostics
---------------------------

The bake of the DNB continued until Thursday of last week. The results
of the bake will be assessed this week by generating a beam and
looking at the level of water components being extracted from the source.

After a prototype test fit in C-Mod, a hood was designed for the poloidal
CXRS system to retard the build up of boron coating during C-Mod operation.
The permanent repairs for the fueling system continued and will be finished
during the current week. It was decided to repair the damage to the MSE/BES
mirror by using a combination of epoxy and straps to hold it in place.
Experiments are being conducted to find an appropriate epoxy. Two were
tried last week. Two more will be tried this week. The one with the
best combination of holding ability and outgassing will be chosen.


Visitors and Travel
-------------------

Paul Bonoli and Bob Granetz co-chaired RF and MHD topical group sessions
at the NSTX Ideas Forum at PPPL held last week. Paul gave two short
presentations at the forum titled

"Full-wave simulations of HHFW in NSTX Using Exact MHD Equilibria"

and

"Future Modelling Plans for HHFW Heating in NSTX Using TORIC & TRANSP",

while Bob gave a talk discussing disruptions in spherical tokamaks.

Raffi Nazikian came to MIT 1/16-18 to attend the Next Step Option PAC
review and work on the reflectometer upgrade; Gerrit Kramer came to
MIT 1/16-18 to work on the reflectometer upgrade and MSE optics
repair. Joel Hosea, Randy Wilson, and Gerd Schilling from PPPL were
at MIT for the antenna meeting. Les Gereg and Joe Frangipani, also
from PPPL, visited to help with the J-port antenna.