Thursday,  January 22,  Notes

Present: A. Byon, M. Binkley, C. Drennan, J. Elias,  S. Hahn, C. Nelson, 
	 S. Orr, K. Pitts, B. Rodewalt, R. Sanders, R. Schmitt, K. Schuh

COT
     M. Binkley described the present situation regarding the repeater cards.
They are to be mounted in arcs on the end wall and cooled by a copper plate on
the back of each card in contact with a water-cooled aluminum base plate.  The
micro coax leads emerge from the 30 degree crack and travel radially outward to
the cards. Further out in radius the outputs are connected to ribbon cables
which dive down into the slots between end wall hadron calorimeter modules and
are routed to the TDC crates some 20 feet away.
     Two "hard" grounds are provided.  One is at the ASDs on the end plates of
the chamber, and the other is at the TDC's.  A series resistor-inductor
combination on the repeater card is planned to isolate the two while providing
for a DC bias current return path.
     It is clear that this system is not a noise generator but rather, is a
potential victim.  The recommendations were all to this point.  
1) Installation of dielectric breaks in the cooling water lines to break up the
ground loop and minimize voltage excursions for the cooling plates.
2) Keep the low voltage power system for the ASDs quiet by using commercial
trifilar inductor packages at the supplies and air-core inductors at each load
as the B-field rules out magnetics there.
3) Carry out full system tests with a realistic configuration and enough
channels to expose coherent effects.  In particular, measure the repeater card
vulnerability to voltage excursions on the copper cooling plate, measure the
system vulnerability to radiated noise using C. Nelson's noise blaster, and
measure the system behavior with and without back termination resistors on the
ASD boards.  The more of this work that can be quantified with our EMI/EMC
equipment, the better.

Detector Control System
     R. Schmitt described what was being done for rack protection on the first
and second floors.  A planning meeting will happen soon for the front end
electronics rack protection.  Each upstairs rack is serviced by a 15-pair,
individually shielded cable.  The shields are all hard grounded at the
controller end and neither the sensors nor the shields make electrical
connection to the rack.  Sensors which require power like smoke detectors or
drip detectors are all powered over the cable.  The working group held the view
that hard grounding of the shields for the front end electronics racks should be
done at the racks and the shields floated (or AC terminated) at the controller
end.  As for the upstairs, no sensor should make electrical contact with the
rack.
     New cabling will not be put in for cryogenic control links to the coil.
However, these links are all hard grounded at the coil and floated on the first
floor.  This situation will be reversed; the shields will be lifted at the coil
and grounded at the controllers.  It is very important that none are grounded at
both ends, and the operational procedure for the changes should include a
verification step.
     There are extra copies of Rich's handouts available.

Next Meeting - Feb. 5th		Steve Hahn on source movers
				Keith Schuh on plug temperature control
				Jaco Konigsberg on the luminosity monitor