Coincidence and anti-coincidence measurements in prompt gamma neutron activation analysis with pulsed cold neutron beams

A novel approach is implemented to alleviate some persistent problems in ne utron capture prompt gamma activation analysis (PGAA). Detection sensitivit ies of PGAA are often restricted by the following factors: poor signal to n oise ratios, interferences from background signals, and, in some cases, ove rlapping energy lines from different origins, namely ultra short-lived deca y lines interfering with prompt decay. Timing the gamma-ray acquisition wit h the actual capture events using a pulsed beam of cold neutrons allows dis crimination between prompt and delayed emissions from a sample source as we ll as against background events. Coincidence gating selects the prompt gamm a-ray emissions. Contributions of background capture gamma-rays are suppres sed because of different flight times of neutrons to the sources of backgro und radiation, providing a reduction in direct gamma-ray interferences. Ant i-coincidence gating allows measurement of only decay radiation that origin ates from short-lived activated states of the nuclides after capture. Spect ra of decaying nuclides are free of interfering prompt activities, as well as have lower continuum background from Compton scattering of high-energy p rompt gamma-rays in the detector. The measurements provide the opportunity to use ultrashort half-life nuclides for analytical purposes, no sample tra nsfer times are lost, and repetitive activation and counting cycles are ach ieved with the use of pulsed neutron beams.