Technical
Brief #5- Lifetime
BURLE has pioneered a family of
long-life glasses that are used exclusively in BURLE Long-Life™
Microchannel Plates (MCPs). These glass types have been specifically
engineered to be very stable, providing extended operational
life.
The lifetime of a microchannel
plate ultimately determines the useful working time of the device
in which it is placed. Figure 1 shows the superior gain stability
of Long-Life MCPs as compared to conventional MCPs. Decreased
lifetime for microchannel plates usually involves changes in
the first strike conversion efficiency when a primary event,
an ion or photon, strikes the channel wall on the input side.
If the conversion efficiency decreases over time, then the useful
lifetime of the multiplier will also be compromised. The intrinsic
secondary electron yield loss within the channel caused by contamination
or radiolytic damage to the inside of the channel walls may
also decrease lifetime. Care should be taken to prevent exposure
to high concentrations of halogens and hydrocarbons. BURLE's
long-life glass composition has been specifically formulated
to minimize the effects of these two loss mechanisms.
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Figure 1
Figure 2 demonstrates the typical
gain degradation of a Long-Life Microchannel Plate as a function
of extracted output charge in terms of coulombs per square centimeter.
After an initial burn-in period, in which the detector gain
changes as a result of degassing residual gas molecules from
the inside of the channel, detector performance is very stable
over a large amount of extracted output charge.
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Figure 2
Approximately 40 coulombs per square
centimeter can be extracted from a microchannel plate in a clean
working environment without significant gain degradation. Other
glass systems typically will produce a stable gain operating
period of about one to ten coulombs per square centimeter. Please
refer to BURLE’s Tech Brief
#6 - Storage and Handling Guidelines for additional information
on maximizing detector performance
