Radiation Detectors
PROPORTIONAL COUNTER CIRCUITRY
The BF3 proportional counter is used to monitor low power levels in a nuclear reactor. It is used
in the "startup" or "source range" channels. Proportional counters cannot be used at high power
levels because they are pulse-type detectors. Typically, it takes 10 to 20 microseconds for each
pulse to go from 10% of its peak, to its peak, and back to 10%. If another neutron interacts in
the chamber during this time, the two pulses are superimposed. The voltage output would never
drop to zero between the two pulses, and the chamber would draw a steady current as electrons
are being produced.
Summary
Proportional counter circuitry is summarized below.
Proportional Counter Circuitry Summary
The proportional counter measures the charge produced by each particle of
radiation.
The preamplifier/amplifier amplifies the voltage pulse to a usable size.
The single channel analyzer/discriminator produces an output only when the input
is a certain pulse size.
The scaler counts the number of pulses received during a predetermined length
of time.
The timer provides the gating signal to the scaler.
Rev. 0
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IC-06
