Radioactive source calibration

An apparatus for calibration of a radioactive sample, the apparatus comprising:

• a receptacle containing a sample chamber and configured to retain the radioactive sample;
• an array of at least three scintillation detectors disposed around the sample chamber;
• an array of light transducers, each light transducer optically coupled to a respective one of the scintillation detectors;
• and
• a plurality of electronic counters comprising an electronic counter for each respective scintillation detector;
• wherein each light transducers is electrically coupled to a respective one of the electronic counters for independently counting radioactive decay events of the radioactive sample detected by the respective scintillation detector.

One or more computer-readable media storing instructions which, when executed by one or more hardware processors, cause the one or more hardware processors to perform operations comprising:

• (a) synchronizing respective counting electronics for an array of at least three particle detectors;
• (b) time-tagging digital packets of particle detection events for each of the particle detectors;
• (c) maintaining respective queues for the particle detectors, wherein time-tagged events of each of the particle detectors are stored in a respective one of the queues;
• (d) maintaining respective pointers to a respective marker event in each of the queues wherein, for any given queue, the time-tagged events earlier than the respective marker event have already been tested for coincidence and the time-tagged events later than the respective marker event have yet to be tested for coincidence;
• (e) selecting an earliest among the marker events;
• (f) determining a number N of other marker events which are in coincidence with the earliest marker event;
• (g) incrementing a counter;
• and
• (h) advancing the pointer to the earliest marker event and, in a case where N≥1, advancing the pointers to the other marker events which are in coincidence with the earliest marker event.

A method for calibrating a radioactive sample, comprising:

• providing a plurality of scintillation detectors coupled by photodetectors to respective counting electronics;
• tuning bias power supply outputs coupled to the photodetectors so that photopeaks of particles emitted by a radioactive calibration source appear at aligned energy channels at the respective counting electronics;
• positioning a sample container containing the radioactive sample at a central location amid the scintillation detectors;
• time-tagging decay events detected at the scintillation detectors, independently for each scintillation detector;
• detecting coincidences among the time-tagged decay events from two or more of the scintillation detectors;
• aggregating time-tagged decay events from the scintillation detectors, with coincidences being singly counted, to obtain a correlated event rate;
• determining a radioactivity level of the radioactive sample from the correlated event rate;
• and
• reporting the determined radioactivity level.