May 12, 2000
Starting at about 1:06 UT May 12, 2000, the pressure in the propane volume of PCU 0 suddenly began decreasing. The propane pressure is expected to reach zero within a day. The PCU 0 high voltage is currently off. At this moment, we expect the xenon volume will be maintained, and we will test this early next week after the pressures have become stable.
We expect that PCU 0 will remain functional, have an increased background rate, and a somewhat different gain. We will provide additional information next week.
- Keith Jahoda for the PCA team
May 16, 2000
The propane layer of PCU 0 has effectively been emptied. The xenon
layer pressure has come to equilibrium at a value about 0.5% lower.
Pressure plots of loss can be found at
http://asd.gsfc.nasa.gov/users/keith/pcu1/ .
The xenon voltage in PCU 0 was turned on again briefly on May 15.
The xenon total rates were similar to what they were when the propane
layer was intact, as expected. The rate of events with one and only
one xenon anode triggered were 20-25 % higher than the corresponding
rate in PCU 2. The majority of this increase is expected to be due to
electrons entering the top layer of the xenon volume, which used to be
vetoed because they triggered both the propane layer and the top xenon
layer. Further analysis of these data will be presented soon.
Operations plans are being developed.
More Information about PCU 0