The Los Alamos Neutron Science Center (LANSCE) is a linear accelerator in Los Alamos, New Mexico that accelerates a proton beam to 800 MeV, which then produces spallation neutron beams. Flight path FP15R uses a tungsten target to generate neutrons of energy ranging from several hundred keV to ~600 MeV. The beam structure has micropulses of sub-ns width and period of 1.784 ns, and macropulses of 625 μs width and frequency of either 50 Hz or 100 Hz. This corresponds to 347 micropulses per macropulse, or 1.74 x 104 micropulses per second when operating at 50 Hz. Using a very fast, cooled ICCD camera (Princeton Instruments PI-Max 4), gated images of various objects were obtained on FP15R in January 2015. Objects imaged included blocks of lead and borated polyethylene; a tungsten sphere; and a tungsten, polyethylene, and steel cylinder. Images were obtained in 36 min or less, with some in as little as 6 min. This is novel because the gate widths (some as narrow as 10 ns) were selected to reject scatter and other signal not of interest (e.g. the gamma flash that precedes the neutron pulse), which has not been demonstrated at energies above 14 MeV. This proof-of-principle experiment shows that time gating is possible above 14MeV and is useful for selecting neutron energy and reducing scatter, thus forming clearer images. Future work (simulation and experimental) is being undertaken to improve camera shielding and system design and to precisely determine optical properties of the imaging system.
In recent years, composite scintillators consisting of nanosize inorganic crystals in an organic matrix have been
actively developed. Ideally these scintillators would have efficiency and resolution similar to inorganic crystals,
but at the same time would be inexpensive and easy to manufacture. In order to make composite scintillators
optically transparent, McKigney et al. finds that nanosize inorganic crystals should be used in order to reduce
optical scattering. One way to produce these nanosize inorganic crystals is through wet milling, where inorganic
crystals are ground with microsize beads in an organic solvent to achieve size reduction. Milling is relatively
simple in terms of preparation and equipment; however, milling is also known to introduce defects into the
ground material. Therefore, a new light yield measurement technique is developed to evaluate the degree to
which milling alters the light yield of the milled inorganic crystals. In this work, the light yield measurement
technique is applied to samples containing BaFCl:Eu inorganic crystals milled in a tributyl phosphate (TBP)
and cyclohexane mixture.
Nanophosphor LaF3:Ce has been synthesized and incorporated into a matrix to form a nanocomposite
scintillator suitable for application to γ-ray detection. Owing to the small nanocrystallite size (sub-10 nm),
optical emission from the γ / nanophosphor interaction is only weakly Rayleigh scattered (optical attenuation
length exceeds 1 cm for 5-nm crystallites), thus yielding a transparent scintillator. The measured energy
resolution is ca. 16% for 137Cs γ rays, which may be improved by utilizing brighter nanophosphors. Synthesis of
the nanophosphor is achieved via a solution-precipitation method that is inexpensive, amenable to routine
processing, and readily scalable to large volumes. These results demonstrate nanocomposite scintillator proof-of-
principle and provide a framework for further research in this nascent field of scintillator research.
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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