  Noise and Malter breakdown have been studied at high rates in a test chamber
having the same cell structure and gas as in the BaBar drift chamber. The
chamber was first damaged by exposing it to a high source level at an elevated
high voltage, until its operating current at normal voltages was below
0.5nA/cm. Additives such as water or alcohol allowed the damaged chamber to
operate at 25 nA/cm, but when the additive was removed the operating point
reverted to the original low value. However with 0.02% to 0.05% oxygen or 5%
carbon dioxide the chamber could operate at more than 25 nA/cm, and continued
to operate at this level even after the additive was removed. This shows for
the first time that running with an O2 or CO2 additive at high ionisation
levels can cure a damaged chamber from breakdown problems.

High Energy Physics - Experiment