e
——
a
With the Hornyak, this occurs at
about 400 KEV and with the Hurst this occurs
at about 200 KEV,
For many purposes these values are
entirely too hich and a large proportion of
an energy degraded neutron spectrum cannot
be measured, particularly this is the cace
when the maximum original energy of a neutron
occurs at about 15 MEV.
There exists a high energy basis in
which the hydrogen cross section on which all
these counter instruments that we use depends
to a greater or lesser extent varies from its
maximum zero energy values of about 80 down
to about one barn in 10 MEV and 2/10th of ‘«
barn in 40 MEV,
Now, since most counters either
raise a count when a pulse ie higher than
the precent peak voltage, this mesns that
due to the emall size of the instrument and
the decreasing cross section it is difficult
to get reliable results when neutron being
measured has energies higher than 15 MEV, the
long counter recponse ia down to about 85 per
cent at 5 MEV due to the increase in the rean
free path of the instant neutron in the paraf-~
fine Jacket.
a,
107