Although the major use of geiger counters is for
particle detection, they are
also used as survey meters. A gamma survey meter has suitable shielding around
the detector to eliminate response to beta particles
and ensure that the instrument reads a gamma radiation field correctly in
appropriate units, namely mSv/h or
.
The geiger counter survey meter used widely at TRIUMF is the Ludlum
14C , which
is shown in Fig. 6.8
.
The instrument is used with a model 44-7
probe, but is also equipped with a small internal detector for high range
gamma detection.
In regions where a substantial magnetic field exists a Xetec 305 is used for gamma survey. These meters have a digital read-out which is insensitive to magnetic fields and their internal electronic components have been modified or shielded so that they are not affected by magnetic fields.
For very high radiation fields a Xetec Fission Pole is used. This is also basically a Model 305 instrument but has the detector mounted on a long pole so that it can be introduced into a field without the operator approaching too closely.
