Comparison of Lithium Gadolinium Borate Crystal Grains in Scintillating and Nonscintillating Plastic Matrices

Abstract

We present a method for detecting neutrons using scintillating lithium gadolinium borate crystal grains in a plastic matrix while maintaining high gamma rejection. We have procured two cylindrical detectors, 5" × 5", containing 1% crystal by mass and with the crystal grains having a typical dimension of 1 mm. One detector was made with scintillating plastic, and one with nonscintillating plastic. Pulse shape analysis was used to reject gamma ray backgrounds. The scintillating detector was measured to have an intrinsic fast fission neutron efficiency of 0.4% and a gamma sensitivity <; 4.93 × 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-9</sup> , while the nonscintillating detector had a neutron efficiency of 0.6 or 0.7%, depending on analysis integration limits, with gamma sensitivity <; 4.93 × 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-9</sup> and (3.25 ±2.84) × 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-7</sup> , respectively. We determine that increasing the neutron detection efficiency by a factor of 5-6 will make the detector competitive with moderated <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sup> He tubes, and we discuss several simple and straightforward methods for obtaining or surpassing such an improvement. We end with a discussion of possible applications, both for the scintillating-plastic and nonscintillating-plastic detectors.