Automatic-recording apparatus for fission-fragment time-of-flight measurements

An apparatus has been constructed to measure the velocities of both members of a fission-fragment pair. A zero-time signal is obtained at the expense of about one per cent of the fragment energy by detecting delta rays ejected by the fragment from a thin plastic foil placed near the source. The fragment times of flight are converted to pulse heights for analysis. An overall time resolution of 3.5 mμsec is obtained. A third variable, e.g. gamma-ray energy or prompt neutron time of flight, may also be recorded, the three pulse heights being punched consecutively on paper tape. Three-dimensional analysis is therefore possible but in practice sorting is done taking two variables at a time.