Neutron counting by delayed capture-gamma detection (DCD)

An apparatus to detect neutrons and gamma rays, comprising:

• at least one gamma-ray detector comprising at least one scintillator material with a light decay time coupled to a photo detector and an amplifier, wherein the at least one gamma-ray detector is adapted to record an electrical signal from an interaction between gamma rays and the at least one scintillator material;
• at least one neutron-gamma converter in gamma communication with the at least one scintillator material, wherein the at least one neutron-gamma converter is adapted to emit gamma radiation upon capturing neutrons, wherein the at least one neutron-gamma converter comprises at least one isotope having a thermal neutron capture cross-section larger than 1 barn and forming a daughter nucleus upon neutron capture, wherein the daughter nucleus has a level scheme including at least one long-lived excited state with a lifetime between 1 nanosecond and 500 nanoseconds that is at least sometimes populated in de-excitation cascades, such that neutron capture events produce a prompt gamma emission followed by a delayed gamma emission from the long-lived excited state;
• at least one digitizer, wherein each of the at least one digitizer is adapted to sample the electrical signal of the at least one gamma-ray detector with a predetermined frequency to generate digitized time series data;
• and
• an analyzer which is coupled operatively to the at least one digitizer, wherein the at least one digitizer is adapted to transmit the digitized time series data to the analyzer, and wherein the analyzer is adapted to:
• identify, in the digitized time series data, events comprising a prompt component and at least one delayed component;
• for each of the events, determine event parameters comprising a time difference between the prompt component and the at least one delayed component and an amount of energy deposited in the scintillator material by the at least one delayed component;
• for each of the events, discriminate between a neutron capture event and a gamma-ray-only event based on a combined analysis that is a function of the time difference between the prompt component and the at least one delayed component and an amount of the energy deposited by the at least one delayed component, wherein a neutron capture event is characterized at least in part by said energy being within a predefined energy range;
• and
• compute a measure of neutron flux using the discriminated neutron capture events.