Neutron flux from linear accelerators is conventionally monitored using ionization chambers containing one or
more foils thinly coated with a fissionable or fissile material. Due to the long pulse rise times resulting from the
ionization mechanism, fission chambers are prone to pulse pile-up in high-neutron-flux environments. In addition,
their relatively low efficiencies result in extremely long counting times in low-flux environments. To ameliorate
these effects, a novel type of neutron flux monitor, consisting of fissionable material loaded in a liquid scintillator,
has been developed, characterized, and tested in the beam line at the Los Alamos Neutron Science Center. This
is a rugged, cost-efficient detector with high efficiency, a short signal rise time, and the ability to be used in low
neutron-flux environments. Compared with a conventional fission chamber, the fissionable scintillator displays a
significantly higher event rate. Related research on nanocomposite scintillators for gamma-ray detection suggests
the possibility of extending this approach by synthesizing fissionable material nanoparticles and loading them
into an organic scintillator. We will present results of the design and characterization process and an analysis of
the results of the beam line experiments.
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.
A number of dithioacetate and dithiolate mono- and dianions have been synthesized and characterized through Z-scan measurements, with some showing significant third order nonlinear optical (NLO) behavior. Tetralkylphosphonium cations were utilized in tandem with the nonlinear anions so as to minimize electrostatic interactions within the salt, consequently resulting in the materials being room temperature ionic liquids (RTILs), which have numerous advantages over typical organic-based materials. Anions composed of metal-ligand systems were also tested for NLO behavior as components of novel ionic liquid materials. These RTILs introduce a new class of materials with potential applications in optical limiting and other all-optical devices.