US-12625284-B1 - Silicon photomultipliers embedded in scintillator

US12625284B1US 12625284 B1US12625284 B1US 12625284B1US-12625284-B1

Abstract

A scintillator having a silicon photomultiplier (SiPM) embedded therein is described. The scintillator comprises an amorphous organic glass scintillator (OGS) material having a glass transition temperature above which the OGS material behaves as a supercooled or stable liquid, and a SiPM having a lead coupled thereto and having a temperature tolerance greater than the glass transition temperature of the OGS material. The SiPM is positioned in the OGS material while the OGS material is in a liquid state above the glass transition temperature, and the OGS material is cooled to an amorphous solid state below the glass transition temperature with the SiPM embedded therein.

Inventors

Melinda Dominique Sweany
Kyle James Weinfurther
Patrick L. Feng
Peter Anthony Marleau

Assignees

NATIONAL TECHNOLOGY & ENGINEERING SOLUTIONS OF SANDIA, LLC

Dates

Publication Date: 20260512
Application Date: 20240530

Claims (20)

1 . A scintillator having a silicon photomultiplier (SiPM) embedded therein, comprising; an organic glass scintillator (OGS) material having a glass transition temperature above which the OGS material exhibits supercooled liquid characteristics and below which the OGS material is in an amorphous solid state; and an SiPM having a lead coupled thereto and having a temperature tolerance greater than the glass transition temperature of the OGS material; wherein the SiPM is positioned in the OGS material while the OGS material is above the glass transition temperature, and wherein the OGS material is cooled to the amorphous solid state below the glass transition temperature with the SiPM embedded therein.
2 . The scintillator of claim 1 , wherein the SiPM and the amorphous OGS material are placed in a removable mold, where the amorphous OGS material is cooled to the amorphous solid state in the removable mold.
3 . The scintillator of claim 2 , wherein the SiPM is positioned in the mold prior to filling the mold with the OGS material.
4 . The scintillator of claim 2 , wherein the SiPM is positioned in the mold after filling the mold with the OGS material.
5 . The scintillator of claim 1 , wherein the OGS material is printed by a 3D printer, and wherein printing is paused for insertion of the SiPM and resumed after insertion of the SiPM.
6 . The scintillator of claim 1 , wherein the SiPM is positioned at least one attenuation length away from the outer surfaces of the scintillator.
7 . The scintillator of claim 1 , further comprising at least one of: internal reflective material that was mixed into the scintillator material while in an amorphous state, wherein the internal reflective material reflects light inside the scintillator toward the SiPM; or external reflective material positioned on an external surface of the solidified scintillator, wherein the external reflective material reflects light exiting the scintillator back into the scintillator material for detection by the SiPM.
8 . The scintillator of claim 1 , wherein the OGS material includes a plasticizer additive that reduces the glass transition temperature of the OGS material to a temperature below the SiPM temperature tolerance and decreases a melt viscosity of the OGS material at a given temperature above the glass transition temperature.
9 . The scintillator of claim 1 , wherein the lead is left protruding from the scintillator for connection to read-out circuitry.
10 . The scintillator of claim 1 , wherein the lead is coupled to read-out circuitry that is embedded in the scintillator with the SiPM.
11 . A method for manufacturing a solid scintillator having a silicon photomultiplier (SiPM) embedded therein, the method comprising: heating an organic glass scintillator (OGS) material to a temperature above a glass transition temperature of the OGS material above which the OGS material is in a supercooled or stable liquid state and below which the OGS material is in an amorphous solid state; positioning an SiPM with a lead coupled thereto in an interior cavity of a mold, the SiPM having a temperature tolerance above the glass transition temperature of the OGS material; flowing liquid OGS material into the mold; and cooling the OGS material until solid with the SiPM and at least a portion of the lead embedded therein.
12 . The method of claim 11 , further comprising removing the mold from the solidified OGS material.
13 . The method of claim 11 , further comprising positioning the SiPM in the mold prior to filling the mold with the OGS material.
14 . The method of claim 11 , further comprising positioning the SiPM in the mold after filling the mold with the amorphous OGS material.
15 . The method of claim 11 , wherein the glass transition temperature is in the range of 25° C. to 200° C.
16 . The method of claim 11 , further comprising positioning the SiPM at least one attenuation length away from an outer surface of the scintillator.
17 . The method of claim 11 , further comprising adding a plasticizer material to the OGS material, wherein the plasticizer material reduces the glass transition temperature of the OGS material to a temperature below the SiPM temperature tolerance and decreases a melt viscosity at a given temperature above the glass transition temperature.
18 . The method of claim 11 , further comprising using active cooling to cool the amorphous OGS material to reduce SiPM exposure to heat.
19 . A system for manufacturing a solid scintillator with a silicon photomultiplier (SiPM) embedded therein, the system comprising: a heat source that applies heat to an organic glass scintillator (OGS) material to maintain the OGS material in a liquid state above a glass transition temperature of the OGS material; a computing system that controls the heat source; a temperature monitor that monitors a temperature of the OGS material and which provides OGS material temperature information to the computing system; a mold having an interior cavity that receives amorphous OGS material; and a SiPM that is placed in the mold and is coupled to a lead that protrudes from the mold and the amorphous OGS material, wherein the SiPM has a temperature tolerance that is higher than the glass transition temperature.
20 . The system of claim 19 , further comprising an active cooling component that accelerates cooling of the amorphous OGS material with the SiPM embedded therein and reduces exposure of the SiPM to heat.

Description

STATEMENT OF GOVERNMENTAL INTEREST This invention was made with Government support under Contract No. DE-NA0003525 awarded by the United States Department of Energy/National Nuclear Security Administration. The U.S. Government has certain rights in the invention. BACKGROUND A scintillation detector includes a scintillator that scintillates (generates photons) upon ionizing radiation impinging upon the scintillator. The scintillation detector also includes a photodetector that detects photons generated by the scintillator (e.g., converts photons to electrons). The scintillation detector further includes processing circuitry that generates an output that is indicative of a characteristic of the ionizing radiation based upon electrons output by the photodetector. For example, the output can indicate that the ionizing radiation is gamma radiation (rather than a neutron impinging upon the scintillator) and that the gamma radiation has a particular energy. Conventionally, the photodetector in a scintillation detector is a photomultiplier tube (PMT). PMTs utilize the photoelectric effect to convert a photon to an electron and include a vacuum-housed dynode chain to focus and amplify the photoelectron into many secondary electrons where they are collected on an anode pad that can be read out for further analysis. PMTs are a relatively mature technology capable of single photon quantum efficiencies of up to 35%. PMTs, however, have several drawbacks, such as size (PMTs have relatively large volumes compared to their photosensitive areas) and ruggedness (PMTs are relatively fragile). An alternative technology to a PMT that addresses these drawbacks is a photodetector that includes solid-state single photon avalanche diodes (SPADs). SPADs are commonly found in silicon photomultipliers (SiPMs), where a SiPM includes thousands to tens of thousands of micron-scale SPADs (where a micron-scale SPAD is referred to herein as a microcell). In a SiPM, microcells are arrayed together into millimeter-scale photodetectors. SiPMs are more compact than PMTs, are more robust than PMTs, and require less power to operate than PMTs. Scintillation detectors find application in petroleum drilling and exploration, radiation protection, medical imaging, high-energy particle physics, and radioactive material detection and characterization. Such detectors can be configured to detect various types of radiation, such as alpha radiation, beta radiation, gamma radiation, or neutron radiation. Conventionally, scintillation detectors have employed a scintillator that is optically coupled to a photomultiplier tube to detect the interaction of radiation with the scintillator. More recently, pixelated arrays of SiPMs capable of detecting single-photon events have been developed. In some applications, a scintillator coupled to a SiPM can result in improved light collection in high aspect ratio scintillators. Materials used for scintillators have included stilbene crystals and certain types of radioluminescent plastics. However, these materials are poorly suited for irregularly shaped scintillators, as they generally must be cut from a larger crystal or other element and then polished to achieve desired light emission and propagation characteristics. For irregularly shaped scintillators, these machining operations risk damaging the scintillator, reducing manufacturing yield, reliability, and/or performance. Moreover, conventionally, SiPMs and PMTs are mounted to a flat exterior surface of the scintillator. Providing flat surfaces on the scintillator to mount the photodetector further reduces manufacturing yield by increasing manufacturing time and imposes constraints on the shape of the scintillator. SUMMARY The following is a brief summary of subject matter that is described in greater detail herein. This summary is not intended to be limiting as to the scope of the claims. Described herein are various technologies pertaining to organic glass scintillators having SiPMs embedded therein. When manufacturing the described scintillator, a computing system (e.g., a control module or the like) controls a heating element to heat an organic glass scintillator (OGS) material beyond its glass transition temperature to make the OGS material a supercooled or stable liquid that exhibits supercooled liquid characteristics including, e.g., viscous flow. In an example, one or more SiPMs having leads coupled thereto are positioned in an interior cavity of a mold (e.g., a silicone mold or the like) with their respective leads protruding therefrom. The mold is filled with the liquid OGS material, surrounding the SiPMs and the portions of their respective leads that are within the mold cavity. The liquid OGS material is cooled until it reaches an amorphous solid state with the SiPMs embedded in the solidified amorphous scintillator material with their leads protruding therefrom for connection to processing circuitry (also referred to herein as “read-out circuitry”). In o