Abstract
Silicon photomultipliers have received a great deal of interest recently for use in applications spanning a wide variety of fields, including nuclear safeguards and nonproliferation. For nuclear-related applications, the ability of silicon photomultipliers to discriminate neutrons from gamma rays using pulse shape discrimination when coupled with certain organic scintillators is a characteristic of utmost importance. This work reports on progress characterizing the performance of twenty different silicon photomultipliers from five manufacturers with an emphasis on pulse shape discrimination performance and timing. Results are presented on pulse shape discrimination performance as a function of overvoltage for 6-mm x 6-mm silicon photomultipliers, and the time response to stilbene is characterized for silicon photomultipliers of three different sizes. Finally, comparison with a photomultiplier tube shows that some new-generation silicon photomultipliers can perform as well as photomultiplier tubes in neutron-gamma ray discrimination.
Highlights
THE ability to detect neutrons and characterize their sources is essential for a variety of nuclear security and safeguards tasks
This paper focuses on applications to homeland security and, as such, reports on progress in characterization of a suite of different silicon photomultipliers (SiPMs) in regard to their ability to discriminate neutrons from gamma rays when coupled to an organic scintillator, as well as their timing properties
A primary motivating factor for the assessment of SiPMs for nuclear security is their application to neutron detectors, especially organic scintillators that are sensitive to both gamma rays and neutrons
Summary
THE ability to detect neutrons and characterize their sources is essential for a variety of nuclear security and safeguards tasks. By operating these avalanche photodiodes in Geiger mode high gain is achieved, and the presence of many different microcells enables signal proportionality. They offer additional advantages characteristic of solid state technology such as mechanical ruggedness, insensitivity to magnetic fields, compactness, and a much lower operating voltage than PMTs [4] Their main drawback has been higher noise levels than PMTs which is primarily caused by thermal generation of charge carriers in the avalanche region of the SiPM that produce a signal indistinguishable from optically produced charge carriers. This paper focuses on applications to homeland security and, as such, reports on progress in characterization of a suite of different SiPMs in regard to their ability to discriminate neutrons from gamma rays when coupled to an organic scintillator, as well as their timing properties
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