Alcator C-MOD Weekly Highlights
				May 12, 1994

Phase II Plasma operation is continuing, with good progress being made this
week in bringing the machine up to speed, as well as on diagnostics and ICRF
preparation. 

Standard deuterium plasmas, with currents above 600kA and pulse lengths of
about one second, were run on Tuesday. Discharge cleanliness seems to be
improving well as operation proceeds. Good diverted equilibria with 2 cm inner
and outer gaps and elongation over 1.55 have been produced. Optimization of
x-point location and matching to the shape of the new ICRF antennas is
proceeding. 

The new toroidal halo current rogowski coils and the new shunts on the outer
divertor modules are collecting interesting data. The halo currents at the top
of the machine on upward moving VDE's are found to smaller, by a factor of 
three or more, than the halo currents observed at the bottom of the machine on
downward moving VDE's. The difference is believed to be due to the different
conducting structures, primarily the divertor, in contact with the scrapeoff
plasma in the downward-moving cases.

The new poloidal-field pickup coils installed on the outboard (RF-protection)
limiters are also operational. The unintegrated signals are being used to
observe MHD activity in the plasma. 

The ECE grating polychromator obtained from Livermore is online and taking
data. This diagnostic will complement the scanning Michelson ECE diagnostic,
and will be particularly useful for observing transient phenomena, such as
H-mode transitions, and for perturbative transport experiments. 

The U. of Md. Optical Multi-channel Analyser diagnostic has been re-installed
and is again operational. All of the visible light arrays, used for
reconstruction of H-alpha and/or other visible line emissivity spatial
profiles, are also now installed and operational.

The full D-port ICRF antenna tuning and matching system is installed and
operational. The system has been tuned for vacuum coupling and antenna
conditioning has begun.

The "fizzle detector", which triggers power supply inversions when the plasma
current terminates early, has been tested and is now operational on all
supplies. The benefits include reduced heating of magnets, shortening the
time between shots, and reduced wear-and-tear on supplies, which otherwise tend
to be driven to their pre-set limits when the plasma terminates and the
feedback loops are still active. 

Some of the problems with magnetics signals mentioned in previous reports have
been traced to faulty 20-pin connectors and feedthroughs. The connector
contacts apparently become unreliable after a relatively small number of
mating/disconnect operations. This problem has been acknowledged by the
manufacturer. A temporary repair has been effected on the particular connector
containing the suspect magnetics used for machine control. Plans are being
formulated for a more extensive permanent repair; there are 57 such connectors
in the magnetics system, one third of which are in vacuum. 

Miklos Porkolab and Paul Bonoli attended the meeting of the Transport Task
Force Modeling Working Group at GA last week. Ten Alcator team members,
including staff and students, attended and presented papers at the Diagnostics
Conference in Rochester.