102
deposition rate is the critical pirameter
and this depends only on the dose rate.
This ig not the cace for the BF
Chamber, nowever,
The fonirzntion curren
produced in the BF3 Chamber is proportional
to the number of fret neutrons which have
been thermalized in the sixth centimeter
polyethylene moderator and this depends on
_ energy.
According to Enyder and Neufeld,
the ratio according to fast rem rate at
five MEV and the depth of gix MEV in
tiseve is ten to one, but at ten MEV it is
only one to a hundred.
All our instrument calibrations
are done in terma of polonium beryllium
and plutonium beryllium neutron sources.
These have essentially the same spectron
and so for the calibration of counters,
counting time instruments all that is needed
to know is the output of the source.
However, for instrunents suoh as
fonization chambers, which are also sensitive
to gamma radiation, it is necessary to know
the gamma output of the cources,