Long-Term Stability Characteristics of Commonly Used Channel Electron Multipliers

The gains of seven units of a commonly used channel electron multiplier model have been observed as a function of total accumulated counts in a clean, ion-pumped vacuum station at 3 ?? 10-10 Torr. After decreasing by a factor of two to three during the first 5 ?? 107 counts of operation, all gains remained relatively constant until the channel multipliers had each accumulated about 1010 counts at which time a continual degradation began. A typical channel electron multiplier degraded from a gain of 1.25 ?? 108 at 1010 counts to 7.0 ?? 107 at 1.4 ?? 1011 total accumulated counts, The effects of gain fatigue on high count-rate capability, on resistance, and on the output pulse-height spectrum shape are also presented, Less extensive data showing the long-term stability characteristics of a newer model of channel multiplier with longer life are included.