Proton Recoil Neutron Spectrometry With Organic Scintillators

Author : Josh Arthur Brown
Publisher :
ISBN 13 :
Total Pages : 129 pages
Book Rating : 4.:/5 (16 download)

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Download or read book A Double Time of Flight Method For Measuring Proton Light Yield written by Josh Arthur Brown and published by . This book was released on 2017 with total page 129 pages. Available in PDF, EPUB and Kindle. Book excerpt: Organic scintillators have been used in conjunction with photomultiplier tubes to detect fast neutrons since the early 1950s. The utility of these detectors is dependent on an understanding of the characteristics of their response to incident neutrons. Since the detected light in organic scintillators in a fast neutron radiation field comes primarily from neutron-proton elastic scattering, the relationship between the light generated in an organic scintillator and the energy of a recoiling proton is of paramount importance for spectroscopy and kinematic imaging. This relationship between proton energy deposited and light production is known as proton light yield. Several categories of measurement methods for proton light yield exist. These include direct methods, indirect methods, and edge characterization techniques. In general, measurements for similar or identical materials in the literature show a large degree of variance among the results. This thesis outlines the development of a new type of indirect method that exploits a double neutron time of flight technique. This new method is demonstrated using a pulsed broad spectrum neutron source at the 88-Inch Cyclotron at Lawrence Berkeley National Laboratory. The double time of flight method for proton light yield measurements was established using two commercially available materials from Eljen Technology. The first is EJ-301, a liquid scintillator with a long history of use. Equivalent materials offered by other manufacturers include NE-213 from Nuclear Enterprise and BC-501A from Saint-Gobain Crystals. The second material tested in this work is EJ-309, a liquid scintillator with a proprietary formulation recently introduced by Eljen Technology with no commercial equivalents. The proton light yield measurements were conducted in concert with several system characterization measurements to provide a result to the community that is representative of the material itself. Additionally, the errors on the measurement were characterized with respect to systematic uncertainties, including an evaluation of the covariance of data points produced and the covariance of fit parameters associated with a semi-empirical model. This work demonstrates the viability of the double time of flight technique for continuous measurement of proton light yield over a broad range of energies without changes to the system configuration. The results of the light yield measurements on EJ-301 and EJ-309 suggest answers to two open questions in the literature. The first is that the size of the scintillation detector used to measure the proton light yield should not effect the result if the spatial distributions of Compton electrons and proton recoils are equivalent. Second, the shape of the scintillation detector should not effect the light yield with the same constraint on the spatial distributions. A characterized hardware and software framework has been developed, capable of producing proton light yield measurements on additional materials of interest. The acquisition, post processing, error analysis, and simulation software were developed to permit characterization of double time of flight measurements for a generic system, allowing it to be utilized to acquire and analyze data for an array of scintillation detectors regardless of detector size or geometric configuration. This framework establishes an extensible capability for performing proton light yield measurements to support basic and applied scientific inquiry and advanced neutron detection using organic scintillators.