Some of the electron capture radionuclides such as
Be and
I emit low energy gamma radiation
which will not be detected very efficiently by Geiger detectors
. The low energy gamma probe, is used for these
radionuclides. It is a NaI crystal and photomultiplier tube which is used with
the same ratemeters as the Geiger tubes. The
operating voltage has to be correctly adjusted to prevent incorrect readings
or damage.