Alcator C-MOD Weekly Highlights
				Oct 29, 1996


	Work on Alcator C-MOD continues. The top and bottom EF coil packages
are now being removed from the machine so that we can inspect these coils
and also reach locations on the vessel wall where several heaters need to
be replaced.  The heaters are used to keep the vessel wall at approximately
35C during operation.  We have also installed a stand around the vessel so
that machine entry can begin again.  Invessel work during this up-to-air will
include a survey of tiles and first wall components and installation of new
diagnostics including a tangential XUV array and the Johns Hopkins invessel
XUV divertor spectrometer. A clean area has been setup for inspecting TF
components. All TF arms will be inspected and their documentation updated.
Tests on the OH2U coax indicate that small increases in the spacing (.002")
between the coax foot and the coil terminal can cause factors of two
increases in the contact resistance.  Changes in the  clamping force on the
foot may have resulted in the resistance increases seen during machine
operation.  Measurements on the OH2L and OH1 coaxes are being made for
comparison with the OH2U data.
	The RF switches for the new transmitters have been assembled
and are ready for testing.  The tunable cavities have been installed and
tested for proper movement and limit switch indications.  Control wiring
installation for the new crowbar cabinets has been resumed.
	Power systems continue to be upgraded and documented.  Modelling
of the EF4 supply and coil has been completed and a set of specifications
for the new EF4 inductor is being written.  The EF4 overvoltage bus
sensing wiring has been changed to eliminate an unnecessary connection through
the voltage isolation board.  PLC and Paragon software used to measure the
EF4 coil temperature is being modified to read properly in the parallel
configuration.  Breakover diodes for use in a new overvoltage circuit to be
installed in all the supplies are in house and work on the new boards can
begin.  Drawings are being updated to reflect ECO's initiated throughout the
last campaign.
	A multi-stage amplifier with improved time response for the He^3
neutron detector bank was added during the last campaign.  Well resolved time
histories of neutron sawteeth during both Ohmic and RF heated plasmas have
been obtained. The data typically have behavior more characteristic of an
off-axis ECE channel , rather than the central one.  The neutron rate
is well correlated to MHD activity.  The fall of the neutron rate at the
sawtooth crash is clearly slower than the electron temperature fall, and can
be characterized by an exponential decay time of 0.3 to 0.6 ms.  Whether
the neutron sawteeth result from ion density oscillations, ion temperature
changes, or ion temperature profile effects cannot be determined from these
data.
	A 1-D Monte-Carlo code has been developed to calculate some aspects
of the neutral dynamics in Alcator C-Mod plasmas. By following
many neutral deuterium particles, power balance (ion-neutrals), ionization
rates, D_alpha emission and power loss ("radiated power") can be
calculated. We hope to gain some insights in the edge dynamics especially
in comparing L and H mode discharges.
	Ian Hutchinson, Earl Marmar, and Miklos Porkolab all attended
the DOE-OFES retreat held last week at Xerox Document University in
Leesburg, Virginia.