Newsgroups: sci.physics.plasma
From WOLFE@CMOD2.PFC.MIT.EDU Mon Jan 9 17:48:39 1995
From: WOLFE@CMOD2.PFC.MIT.EDU
Organization: MIT
Subject: Alcator C-MOD Weekly Highlights

Alcator C-MOD Weekly Highlights
Jan 9, 1995

Alcator C-MOD resumed operation this week after a one-week maintenance
interval, including a "clean" vent. Three runs were scheduled this week;
however, technical difficulties reduced the actual run time to a total of
about 10 hours over two days.

The first run of 1995, on Wednesday, was aimed at increasing the plasma
elongation and improving vertical stability, taking advantage of modifications
to the EFC circuit and increased derivative gain on the fast vertical position
feedback loop. The machine started up normally, with all indications being that
the wall conditioning had not degraded due to the vent. The experiment was
proceeding well when the run had to be stopped due to an interruption in
13.8kV power from Cambridge Electric Company, owing to a break in an
under-street feeder cable a few blocks from the lab.

Following restoration of 13.8 kV service on Thursday, a problem was discovered
in the alternator drive motor, probably an indirect consequence of the power
interruption. This was repaired and operations resumed on Friday. Completion
of the increased kappa run from Wednesday was scheduled as a piggyback
experiment. This experiment was successfully completed, with plasmas centered
on the midplane, the x-point in its nominal location, and elongations in
excess of 1.7, being produced and controlled. Satisfactory tuning of the PID
coefficients for the fast Z-position was established.

The main purpose of Friday's run was continuation of conditioning of the
E-port ICRF antenna. This was not accomplished, due to a problem in
the external stub tuner/phase shifter assembly. The run was terminated early,
upon completion of the piggyback activity, in order to inspect and begin
repair of this tuner. Conditioning of the E-port antenna is scheduled to
resume this week.

Further progress has been made in determining the halo current paths on
vertical disruptions. Signals from a set of B_tor pickup loops on the inner
wall indicate that the inner return path to the plasma is well below the
midplane, at or below the vicinity of the inner divertor module.

Bruce Lipschultz and Garry McCracken visited the University of Toronto last
week for a meeting with Peter Stangeby and his group on collaborations
involving the use of the DIVIMP 2-D impurity Monte Carlo code in the analysis
of C-MOD edge and divertor data.