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
April 18, 2003


Alcator C-Mod resumed plasma operations on Friday. Work continues on
Lower Hybrid, ICRF, and DNB systems.


Physics
-------

Joe Snipes has analyzed the Zeff and triangularity dependence of the
H-mode threshold across a number of tokamaks using the ITPA
Confinement Database. He has found that there is a strong Zeff
dependence of the threshold with increasing threshold for increasing
Zeff. Although ASDEX-Upgrade reports an increase in threshold with
increasing triangularity, there was no clear triangularity dependence
of the threshold across the various tokamaks in the database.


Operations
----------

A fault in the alternator motor gate drive electronics required
several days to fix this week. The alternator was then brought up to
full speed on Friday morning and power tests were begun. All power
supplies and coil systems were successfully tested. The first plasma
attempt in the afternoon produced a 500 kA plasma. Operations will
continue next Tuesday as we condition the vessel and regain physics
quality discharges.

A schedule for plasma operations can be found at

http://www.psfc.mit.edu/cmod/operations/schedule.txt


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

With the delivery of the shroud/stacked waveguide assembly to MIT on
4/15, and the completion of the rear waveguide/power splitter
assembly, PPPL has completed all the tasks required for the LHCD
launcher part of the C-Mod LHCD Project. PPPL and MIT will now work
to install the launcher and bring it into operation during the
fall/winter run campaign.

At MIT, the four chassis for the Lower Hybrid Active Controller
System electronics have been wired and assembled. Placement of the
major components in the four rack cabinets for the Lower Hybrid Active
Controller has been determined, and mechanical detailing has begun.
The modifications to the top of the Low Power Microwave Rack are near
completion.

We continue to bring klystrons into operation. We are ready to begin
long pulse tests (each klystron will be tested into a dummy load to
approx 200 kW for 1 s).


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

All transmitters are now in operation. On Wednesday and Thursday of
this week vacuum conditioning of the D, E, and J-Port antennas was
begun at rf voltages of up to 30 kV. We expect to begin rf operation
into plasmas early next week.


Diagnostic Neutral Beam
-----------------------

The beam is ready to operate into C-Mod plasmas. The beam power system
reliability has been improved during the up-to-air period, and beam
performance is very good.

We are upgrading the Java beam control program. The immediate goal
is to improve the automation of the beam operation so that operator
intervention is not required on every shot.


Travel and Visits
-----------------

Dmitri Mossessian and and Amanda Hubbard participated by video
conference in the ITPA Pedestal Group meeting in Naka, Japan and
presented results and plans for C-Mod-AUG and C-Mod-JET dimensionless
identity experiments.

Drs. R. Maqueda and I. Furno, LANL, were at MIT for the week. They
spent this time re-installing and calibrating the LANL IR camera. Glen
Wurden, LANL, continues to direct the LANL effort.