In a given experimental configuration, the energy value determined by the condition
that the
detector response would be unchanged if the cadmium cover surrounding the detector was replaced
by a fictitious cover opaque to neutrons with energy below this value and transparent
to neutrons with energy above this value.
Source:
PAC, 1982, 54, 1533
(Glossary of terms used in nuclear analytical chemistry (Provisional))
on page 1540