Granted Patent B2

US 12,656,513 · App. 18/235,503 · Granted Jun 16, 2026

Inventors: Juergen Stein (Wuppertal, DE); Guntram Pausch (Dresden, DE)

Assignee: Rapiscan Holdings, Inc.

G01T3/06G01T1/2018

Abstract

Claims (46)

1 . 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.

2 . The apparatus of claim 1 , wherein the photo detector of the at least one gamma-ray detector is a photomultiplier tube, a silicon photomultiplier (SiPM), or an avalanche photodiode.

3 . The apparatus of claim 1 , wherein the lifetime of the at least one long-lived excited state is smaller than the light decay time of the at least one scintillator material.

4 . The apparatus of claim 1 , wherein the at least one isotope of the at least one neutron-gamma converter is at least one of 151 Eu, 155 Gd, 157 Gd, 133 CS, 70 Ge, 79 Br, 81 Br, 127 I, 56 Fe, 110 Cd, and 113 Cd.

5 . The apparatus of claim 1 , wherein the at least one scintillator material comprises the at least one neutron-gamma converter intrinsically, and is preferably at least one of SrI, SrI(Eu), LaBr 3 , LaBr 3 , (Ce), CeBr 3 , NaI, NaI(TI), CsI, CsI(Na), CsI(TI), organic materials, organic materials with Eu or Gd doping, bismuth germanate (BGO), CdWO 4 (CWO), Gd 2 SiO 5 (GSO), or GSO(Ce).

6 . The apparatus of claim 1 , wherein the analyzer is adapted to execute one or more pulse pile-up reconstruction techniques, wherein the pulse pile-up reconstruction techniques comprise decomposing the digitized time series data into their constituents in order to quantify the event parameters.

7 . The apparatus of claim 1 , wherein at least one neutron-gamma converter is arranged in form of a Eu-comprising coating at least partially covering the at least one scintillator material.

8 . The apparatus of claim 1 , wherein the apparatus comprises a first gamma-ray detector and a second gamma-ray detector, wherein

the first gamma-ray detector is adapted to detect both the prompt gamma radiation and the delayed gamma radiation emitted by the at least one neutron-gamma converter;

the second gamma-ray detector is adapted to predominantly detect only the delayed gamma radiation emitted by the at least one neutron-gamma converter; and

the analyzer is adapted to determine the event parameters by executing one of the following:

comparing the digitized time series data of the first gamma-ray detector and the second gamma-ray detector in order to find delayed coincidence detections comprising prompt components and delayed components between the first gamma-ray detector and the second gamma-ray detector and to quantify the time differences between said prompt components and delayed components between the first gamma-ray detector and the second gamma-ray detector, and the energy deposited in the at least one scintillator material by the delayed gamma radiation; or

finding and analyzing delayed detections comprising prompt components and delayed components in the digitized time series data of the first gamma-ray detector by means of pulse pile-up reconstruction techniques in order to quantify the time differences between said prompt components and delayed components, and the energy deposited in the at least one scintillator material by the delayed gamma radiation.

9 . The apparatus of claim 8 , wherein one of the at least one neutron-gamma converter is arranged between the first gamma-ray detector and the second gamma-ray detector, and the second gamma-ray detector comprises a layer of scintillating organic material, wherein the layer of scintillating organic material is adapted to provide an anti-coincidence signal if energetic charged particles from cosmic radiation enter the first gamma-ray detector through the said layer of organic material, thus serving as an anti-cosmic radiation shield for the first gamma-ray detector.

10 . The apparatus of claim 1 , wherein the at least one scintillator material and corresponding electronics are configured to be arranged in a handheld device, and the at least one scintillator material and the at least one neutron-gamma converter are non-toxic.

11 . The apparatus of claim 1 , wherein the at least one scintillator material and corresponding electronics are configured to be arranged in a backpack, and the at least one scintillator material and the at least one neutron-gamma converter are non-toxic.

12 . A method to detect neutrons and gamma rays, utilizing

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;

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 a daughter nucleus having a level scheme comprising at least one long-lived excited state, wherein the at least one long-lived excited state has 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, wherein the analyzer is further configured 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 wherein values defining said predefined energy range are dependent on a type of said scintillator material; and

compute a measure of neutron flux using the discriminated neutron capture events.

13 . The method of claim 12 , wherein the analyzer is further configured to execute one or more pulse pile-up reconstruction techniques, wherein the pulse pile-up reconstruction techniques comprise decomposing the digitized time series data into their constituents to quantify the event parameters.

14 . The method of claim 12 , wherein the method utilizes a first gamma-ray detector and a second gamma-ray detector, whereby the analyzer determines the event parameters by one of:

comparing the digitized time series data of the first gamma-ray detector and the second gamma-ray detector in order to find delayed coincidence detections comprising prompt components and delayed components between the first gamma-ray detector and the second gamma-ray detector and to quantify the time differences between said prompt components and delayed components between the first gamma-ray detector and the second gamma-ray detector, and the energy deposited in the at least one scintillator material by the delayed gamma radiation; and

finding and analyzing delayed detections in the digitized time series data of the first gamma-ray detector by means of pulse pile-up reconstruction techniques in order to quantify the time differences between said prompt components and delayed components, and the energy deposited in the at least one scintillator material by the delayed gamma radiation.

15 . The method of claim 12 , wherein the analyzer:

generates a distribution of time differences between prompt components and delayed components;

discriminates a first signal resulting from a time correlation between prompt components and delayed components from uncorrelated background in said distribution; and

determines a strength of said first signal, wherein the strength of said first signal provides a measure for a thermal neutron flux.

16 . The method of claim 12 , wherein the analyzer:

generates a distribution of energies disposed by the delayed components;

discriminates a second signal resulting from a distribution of energies disposed by the delayed components following neutron captures from uncorrelated background in said distribution; and

determines a strength of said second signal, wherein the strength of said second signal provides a measure for a thermal neutron flux.

17 . The method of claim 12 , wherein the at least one isotope of the at least one neutron-gamma converter is at least one of 151 Eu, 155 Gd, 157 Gd, 133 Cs, 70 Ge, 79 Br, 81 Br, 127 I, 56 Fe, 110 Cd, and 113 Cd.

Assignments (3)

Continuity (2)

References Cited (135)