Determining Light Decay Curves in Plastic Scintillators using Cosmic Ray Muons

Plastic scintillators are used in HEDP and ICF research to measure neutron energies using a time of flight method. The energy resolution and sensitivity of an nToF system has a direct correlation to the scintillation decay time of the plastic. To decrease the decay time, xylene scintillators are quenched with oxygen and consequentially become less efficient at producing light. As time passes, the scintillator becomes oxygen deficient which increases light production and the decay time. Mono-energetic calibration neutrons used to monitor these increases are unavailable at most HEDP and ICF facilities. As a result, it is difficult to determine if oxygen concentration has decreased within these systems. Here, a possible method of calibrating xylene detectors in situ is presented. If the detectors response to cosmic ray muons is known, it can be used to determine the scintillation decay curve produced by a mono energetic neutron. As a result, the need for the remote accelerator based calibration of the xylene detectors is eliminated.