Alcator C-Mod Weekly Highlights
		          July 20, 1998


Engineering:

	Fixturing for the inductive soldering process was completed last week
and has produced excellent quality solder joints.  Production soldering of the
lower TF arms will begin this week.  We have gone to two 10 hour shifts per
day to complete this work in a timely fashion.  However, silver plating of the
TF arms and core has been delayed.  The plating applied to the TF arms did not
pass one of our qualification tests and will have to be redone using a
modified plating process.  Wear tests indicate that the quality of the silver
plating on the contact surface is critical in determining feltmetal lifetime;
therefore any change in the plating process will require re-qualification with
a feltmetal wear test.

	We have begun a redesign of the spring plates used to apply
pressure across the finger joints and feltmetal pads.  Analysis of out-of-
plane loads during high field, high current operation indicates that
the compliance of the spring plates could be marginal.  We are now considering
both changes in design of the spring plate packet and the material used
for the plates.  Elgiloy, suggested to us by Peter Bonanos of PPPL, is being
considered as a replacement for the 301 stainless steel currently being
used.  Elgiloy has twice the yield strength of the 301 and will allow us
to double the pressure applied to the joint while also doubling the range
over which the spring plate operates.  Changes to the design of the
spring plate packet could also double the compliance.

	Progress on the DNB this week centered on cleaning up nuisance
problems encountered in the conditioning of the DNB plasma source.  These
included recalibration of current trip levels on the power supplies for the
arc and the filaments, changes in instrumentation for measurement of currents
and voltages at the arc, and resetting of local timeouts on the filament power
supplies.  Some design modifications were also made to the control scheme
for the accelerator power supply based on the conditioning results.  Work
continued on assembly of the fiber optic control system.

	The new vacuum interface window and coupling-horn beam line, for the
ECDC microwave system which will be installed at H-Port, has been
leak-checked, assembled, and tested for RF transmission properties. The
reflected power is found to be about 5%, which is well within allowable
specifications.

Physics:

Plans are underway to allow the view of C-Mod's vacuum ultra-violet
spectrograph to be scanned across the X-point and divertor regions during a
shot. This will be accomplished without sacrificing any of the core-plasma
viewing capability of the spectrograph. A platinum-coated, shuttered mirror,
placed in the port, but near the vessel outer wall, will be scanned so that
profiles of VUV emission from the divertor (in particular, deuterium
Lyman-alpha) can be obtained every ~0.2 s. This profile information should
allow much more detailed analyses of X-point radiation, divertor MARFEs, and
Lyman-alpha opacity. Previous observations have shown that the electron
temperature in the cold (Te ~ 1 eV) regions, where atomic deuterium
radiates, can be measured using the VUV spectra. Thus profiles of this
quantity may be available as well.

Thirty-two C-Mod Abstracts for the upcoming APS Division of Plasma Physics
Meeting underwent internal review last week. This total includes thirteen
presentations from our non-MIT collaborators. 

Travel and Visits:

	Martin Greenwald travelled to PPPL on Tuesday and Wednesday for a
workshop on turbulence and transport.  The workshop was attended by about 30
people, of which about 10 came from outside labs and the rest from PPPL. He 
presented highlights of recent transport work on C-Mod.
	Ken Gentle from U. Texas was here discussing his analysis of
transient  responses to impurity injections and L-H transitions.  His plans
for the next run campaign were also discussed. Ben Carreras from Oak Ridge
continued his visit this week and gave a seminar.