CMU Meeting Notes  September 11, 1997

Present:  A. Byon, R. DeMaat, G. Drake, J. Elias, S. Hahn, L. Holloway,
	  C. Nelson, S. Orr, A. Tollestrup
 
Situation:
A unique EMI problem in the CMU has been mitigated by installing a capacitor
across the 300 ohm resistor which breaks up the ground loop in the negative high
voltage cable braid.  This configuration shunts currents into the steel of the
detector creating an EMI problem for the EM shower max strip chamber.  Since
configurations which drive currents through the steel of the detector are not
allowed, a special meeting was held to evaluate the options.

Options:
Eliminate the CMU susceptibility by reworking the negative high voltage end of
the chambers so that the present HV "braid plate" sits at chamber ground.
Leave the capacitor "fix" in place and comply with the rules by installing a
pure resistor break in the cable braid at the power supply.

Plan:
Take no action now and continue to install chambers with the bypass capacitor.
Test the efficacy of breaking the loop at the power supply (Wednesday, Sep 17th
Gary Drake & company).
Obtain physics-based limits on the pedestal rms. for the shower max strip
chambers (S. Kuhlman, K. Byrum, and B. Wicklund in about a month).
Dig up the D-Zero safety analysis for their resistor isolated high voltage power
supplies. (J. Elias)
Try to determine what effect the "noise blaster" test is having on the CMU
chamber itself.  (L. Holloway)
Revisit the subject when there is more data on the table.

Worry:
The performance of the CES and the CMU are essential to the physics we want to
do, and both may already be in EMI trouble in a fundamental way.