System and method to count neutrons

A method to detect neutrons and gamma rays, comprising a gamma-ray detector including a 127I scintillator crystal and a photodetector with an amplifier, a digitizer comprising an analog to digital converter (ADC) and, an analyzer operatively coupled to said digitizer, wherein the method comprises the following steps:

• generating 128I upon neutron capture of neutrons interacting with 127I of the scintillator crystal, wherein 128I de-excites both under a prompt emission of gamma radiation and at least partially via at least one long-lived excited state feeding another long-lived excited state, which at least sometimes leads to two delayed energy depositions in the scintillator crystal corresponding to two delayed de-excitation steps producing either conversion electrons or gamma radiation interacting with the scintillator crystal, following a primary signal component which is due to the prompt emission;
• generating, by said gamma ray detector, an electrical signal in succession of an interaction between gamma rays or conversion electrons and said scintillator crystal, wherein said electrical signal is in a known relationship with the energy deposited by the detected gamma rays or conversion electrons in said scintillator crystal;
• sampling, by said digitizer, the electrical signal of said gamma-ray detector with a predetermined frequency of at least 20 mega samples per second to generate a digitized time series of the detected gamma rays, and transmitting the digitized time series to the analyzer;
• identifying, by said analyzer, a primary signal component in the digitized time series corresponding to an energy deposition E0 in a predefined range;
• searching, by said analyzer, for a first delayed signal component in the digitized time series, wherein the first delayed signal component corresponds to an energy deposition ranging between 15 kV and 50 keV, and following the primary signal in time;
• searching, by said analyzer, for a second delayed signal component, wherein the second delayed signal component corresponds to an energy deposition ranging between 100 keV and 200 keV;
• and
• counting, by said analyzer, the number of digitized time series comprising at least the first delayed signal component and the second delayed signal component as neutron events, thereby providing a measure for the neutron flux exposure to the scintillator crystal.