Abstract: A system for detecting gamma radiation by neutron activation of a material includes a switchable radiation source and at least a first detector. The switchable radiation source includes a primary source assembly having an alpha particle emitter, and a target assembly in which, upon irradiation of the target assembly by alpha particles from the primary source assembly, secondary radiation comprising neutrons is produced. An alignment, proximity or exposure of the primary source assembly relative to the target assembly is adjustable to control irradiation of the target assembly by the primary source assembly and thereby selectively irradiate a material under interrogation with the secondary radiation. The first detector is configured to detect gamma radiation prompted by neutron activation of the material under interrogation.

Abstract: A switchable radiation source device includes a primary source assembly that emits primary radiation, and a target assembly in which, upon irradiation of the target assembly by the primary radiation, secondary radiation or radioactivity is produced. An alignment, proximity or exposure of the primary source assembly to the target assembly is adjustable to control irradiation of the target assembly by the primary radiation and thereby control the production of secondary radiation or radioactivity.