Organic-based scintillators are indispensable materials for radiation detection owing to their high sensitivity to fast neutrons, low cost, and tailorable properties. There has been a recent resurgence of interest in organic scintillators due to exciting discoveries related to neutron discrimination and gamma-ray spectroscopy, which represent capabilities previously thought not possible in these materials. I will discuss our development of crystalline and polymer-based scintillators for these applications. Structure-property relationships related to intermolecular interactions and host-guest electronic exchange will be discussed in the context of energy-transfer pathways relevant to scintillation. An emphasis will be placed on the rational design of these materials, as guided by first principles and DFT calculations.
Two related topics will be discussed:
1) Incorporation of organometallic triplet-harvesting additives to plastic scintillator matrices to confer a 'two-state' (singlet and triplet) luminescence signature to different types of ionizing radiation. This approach relies upon energetic and spatial overlap between the donor and acceptor excited states for efficient electronic exchange. Key considerations also include synthetic modification of the luminescence spectra and kinetics, as well as the addition of secondary additives to increase the recombination efficiency.
2) Design of organotin-containing plastic scintillators as a route towards gamma-ray spectroscopy. Organometallic compounds were selected on the basis of distance-dependent quenching relationships, phase compatibility with the polymer matrix, and the gamma-ray cross sections. This approach is guided by molecular modeling and radiation transport modeling to achieve the highest possible detection sensitivity luminescence intensity.
A directional scintillating fiber detector for 14-MeV neutrons was simulated using the GEANT4 Monte Carlo simulation tool. Detail design aspects of a prototype 14 MeV neutron fiber detector under development were used in the simulation to assess performance and design features of the detector. Saint-Gobain produced, BCF-12, plastic fiber material was used in the prototype development. The fiber consists of a core scintillating material of polystyrene with 0.48 mm × 0.48 mm dimension and an acrylic outer cladding of 0.02 mm thickness. A total of 64 square fibers, each with a cross-sectional area of 0.25 mm2 and length of 100 mm were positioned parallel to each other with a spacing of 2.3 mm (fiber pitch) in the tracking of 14-MeV neutron induced recoil proton (n-p) events. Neutron induced recoil proton events, resulting energy deposition in two collinear fibers, were used in reconstructing a two dimensional (2D) direction of incident neutrons. Blurring of recoil protons signal in measurements was also considered to account uncertainty in direction reconstruction. Reconstructed direction has a limiting angular resolution of 3° due to fiber dimension. Blurring the recoil proton energy resulted in further broadening of the reconstructed direction and the angular resolution was 20°. These values were determined when incident neutron beam makes an angle of 45 degree relative to the front surface of the detector. Comparable values were obtained at other angles of incidence. Results from the present simulation have demonstrated promising directional sensitivity of the scintillating fiber detector under development.
Conference Committee Involvement (8)
Radiation Detectors in Medicine, Industry, and National Security XIX
22 August 2018 | San Diego, California, United States
Radiation Detectors in Medicine, Industry, and National Security XVIII
9 August 2017 | San Diego, California, United States
Radiation Detectors: Systems and Applications XVII
31 August 2016 | San Diego, California, United States
Radiation Detectors: Systems and Applications XVI
12 August 2015 | San Diego, California, United States
Radiation Detectors: Systems and Applications XV
19 August 2014 | San Diego, California, United States
Penetrating Radiation Systems and Applications XIV
28 August 2013 | San Diego, California, United States
Penetrating Radiation Systems and Applications XIII
14 August 2012 | San Diego, California, United States
Penetrating Radiation Systems and Applications XII
22 August 2011 | San Diego, California, United States
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