[Halld-tracking-hw] Source of oxygen contamination found

[Lubomir Pentchev]

I wanted to inform everybody that our last experiment with the 
testing chamber was successful: just coating the O-ring groove in the 
G10 frame with Hysol reduced the oxygen contamination from 1400ppm to 
300ppm. Taking into account that the incoming gas has 200ppm, the chamber 
now contributes only 100ppm!

The configuration of the testing chamber is, from bottom to top: Lexan 
sheet, plastic spacer ring (with two Buna-N O-rings), empty cathode G10 
frame (with one EPDM O-ring) on which the groove was coated, top Lexan 
sheet.The gas flow is 220scc/min using 40/60 Ar/CO2.

On Monday we will replace the two Buna-N O-rings with the old type EPDM 
ones, to see if there's an effect. In any case we start preparing for the 
chamber refurbishment and will begin with the third package.

  Best regards,
   Lubomir