Alcator C-MOD Weekly Highlights
                      August 4, 1997



	The Alcator C-Mod maintenance period continues.  On Thursday an
up-to-helium was performed to re-install the Fast Scanning Probe and
Omegatron.  Checks on the calibration of the Inner Wall RF Probe Array were
also completed.  One final up-to-helium will be performed before ECDC
cleanup is begun again to install a new preionization source and replace the
K-bottom periscope.
	The contractor is onsite and repair of the alternator rotor
has begun.  Initial tasks include relocation of some of the alternator
equipment cabinets, improvements in the floor supports, and installation
of a plastic "cleanroom" in which the repair will be done. 
	Data from the divertor cryopump run is now being analyzed to
investigate its effect on impurity transport and pumping. Pumping
speeds in the range of 1000-1500 l/sec for D2 were determined. In nitrogen
injection experiments, pump operation reduced nitrogen concentrations in the
core by about a factor of two. In the private flux region of the
divertor the reduction was even greater. The cryopump also pumped the puffed
recycling impurities, Ar and Ne. The core electron density was also affected
by the pump, since slightly larger puff rates were required to obtain the
same density during the flattop portion of the discharge when the pump was on.
In addition, the density pump-out (occurring during the ramp-down phase) was
faster with the cryopump active. These results were obtained with a single
prototype pump, representing about 10% of the ultimate pumping speed, once
the full cryopump system is installed. 
	Preparation of the DNB power supplies continued with installation of
more power and control wiring.  Control power is now available for the Mod/Reg
Power Distribution rack cabinet.  Construction of the Arc/Filament/Snubber
Primary Controller Optical Receiver panel was completed and tested and is
ready for installation.  Development of the new control system for the DNB
continued.  Design for the vacuum system to PLC interface circuits was started,
as was the design of the suppressor switch to control system interface.
The PLC programming for the DNB vacuum system continued.  Maintenance supports
for the DNB plasma source were completed in preparation for installation of
the source.
	Maintenance work on the RF system continues.  Good progress has been
made repairing the leaking E-port H-probe (on the resonant loop).  The large
leaks from the seal have been fixed, but the probe still leaks around its
bolts.  New bolts are on order which will be used to stop these smaller leaks.
Work on the PLC for transmitters #3 and #4 is progressing.  A prototype DC
break for Langmuir probes was designed and tested.
	DIII-D is planning a major upgrade of their data system and is
considering the use of our MDSplus software as part of their new system.
Discussions concerning the use of MDSplus for that purpose were carried
out during a visit by GA and LLNL personnel; Dave Schissel, Chuck
Greenfield, Kathy Greene, Tom Casper, and Bill Meyer.  The visit
emphasized migration and porting issues. Tom Fredian of MIT will be at
GA this week to give an MDSplus presentation and to work with the GA staff.
A "demonstration" has been implemented at GA which gives access to PTDATA
and EFIT results via MDSplus. NSTX is planning on using MDSplus as well.
The advantages of uniform access to experimental data across the whole
tokamak program are obvious.
	Dr. Gerd Schilling from PPPL visited last Monday with the RF group.
RF hardware upgrades for which PPPL collaborators could provide expertise
and hardware were discussed.  Gary Hallock from FRC visited on 7/28-7/31. He
is helping with the design and construction of the PCI system.
	Josh Stillerman visited the RFX experiment at CNR in Padova Italy
last week and gave a talk on 'MDSplus Remote Collaboration Support'.  Their
MDSplus implementation, VME/realtime devices and future software projects
were discussed.