²⁵²Cf fission-neutron spectrum using a simplified time-of-flight setup: An advanced teaching laboratory experiment

The removal of PuBe and AmBe neutron sources from many university teaching laboratories (due to heightened security issues) has often left a void in teaching various aspects of neutron physics. We have recently replaced such sources with sealed ²⁵²Cf oil-well logging sources (nominal 10-100 μCi), and developed several experiments using them as neutron sources. This includes a fission-neutron time-of-flight experiment using plastic scintillators, which utilizes the prompt γ rays emitted in ²⁵²Cf spontaneous fission as a fast timing start signal. The experiment can be performed with conventional nuclear instrumentation and a 1-D multi-channel pulse-height analyzer, available in most advanced teaching laboratories. Alternatively, a more sophisticated experiment using liquid scintillators and n/γ pulse-shape discrimination can be performed. Several other experiments using these neutron sources are also feasible. The experiments can introduce students to the problem of detecting the dark matter thought to dominate the universe and to the techniques used to detect contraband fissionable nuclear materials.