We present a preliminary design for a neutron detection system that is compact, lightweight, and low power consuming, utilizing the CubeSat platform making it suitable for space-based applications. This is made possible using the scintillating crystal lithium indium diselenide ((LiInSe2)-Li-6), the first crystal to include Li-6 in the crystalline structure, and a silicon avalanche photodiode. The schematics of this instrument are presented as well as the response of the instrument to initial testing under alpha radiation. A principal aim of this work is to demonstrate the feasibility of such a neutron detection system within a CubeSat platform. The entire end-to-end system presented here is 10 x 10 x 15 cm(3), weighs 670 g, and requires 5 V direct current at 3 W. (C) 2016 Society of Photo-Optical Instrumentation Engineers (SPIE)

This thesis consists of two parts; the first part pertains to fractoluminescence as a potential background in crystal scintillator detectors, and the second part bears on the simulation of a 24Na source to be used during the liquid scintillator phase of the SNO+ experiment. I participated in early work to develop a test-bed to study fractoluminescence in scintillators, and report here on preliminary results I obtained before I shifted my focus to SNO+. Full results obtained by the group have since been reported in PRL 111 154301 [1]. This project follows the discovery that mechanical stress on a dark matter detector’s crystals was causing a background signal. The response of inorganic crystal scintillators (Bi4Ge3O12, ZnWO4 , CdWO4 ) compressed to the point of rupture was studied. The double cleavage drilled compression geometry was used to create controlled cracks in 20×5×3 mm3 samples. A correlation between a sudden drop of the force, a burst of photonic and of acoustic emissions was discovered and a lower bound was set on the conversion efficiency from strain energy to light energy. SNO+ is a large underground experiment that aims primarily to search for neutrinoless double beta decay. The SNO+ detector consists of an acrylic vessel of liquid scintillator surrounded by light detectors. A tagged 24Na source was proposed as one of several radioactive sources to be deployed within the vessel to calibrate the detector. To achieve this an activated NaI(Tl) crystal would be coupled to a photomultiplier tube and lowered into the center of the vessel. The second half of this thesis explores options for implementing this plan and presents the detector response to a 24Na source as simulated by the Monte Carlo software developed by SNO+. The size of the crystal influences the type of information that can be gleaned from using this source so four different crystal sizes are presented for comparison. The simulations show that the source can be used to test the linearity of the energy scale and the simulation’s quenching model. / Thesis (Master, Physics, Engineering Physics and Astronomy) -- Queen's University, 2014-06-18 17:46:15.685

<p>The ability to interrogate structure-function photophysical properties on lanthanide-doped nanoscale materials will define their utility in next-generation applications and devices that capitalize on their size, light-conversion efficiencies, emissive wavelengths, syntheses, and environmental stabilities. The two main topics of this dissertation are (i) the interrogation of laser power-dependent quantum yield and total radiant flux metrics for a homogeneous, solution phase upconversion nanocrystal composition under both continuous wave and femtosecond-pulsed excitation utilizing a custom engineered absolute measurement system, and (ii) the synthesis, characterization, and power-dependent x-ray excited scintillation properties of [Y₂O₃; Eu] nanocrystals, and their integration into a fiber-optic radiation sensing device capable of in vivo dosimetry.</p><p>Presented herein is the laser power-dependent total radiant flux and absolute quantum yield measurements of homogeneous, solution-phase [NaYF₄; Yb (15%), Er (2%)] upconversion nanocrystals, and further compares the quantitative total radiant flux and absolute quantum yield measurements under both 970 nm continuous-wave and 976 nm pulsed Ti-Sapphire laser excitation (140 fs pulse-width, 80 MHz). This study demonstrates that at comparable excitation densities under continuous-wave and fs-pulsed excitation from 42 - 284 W/cm<super>2</super>, the absolute quantum yield, and the total radiant flux per unit volume, are within a factor of two when spectra are integrated over the 500 - 700 nm wavelength regime. This study further establishes the radiant flux as the true unit of merit for quantifying emissive output intensity of upconverting nanocrystals for application purposes, especially given the high uncertainty in solution phase upconversion nanocrystal quantum yield measurements due to their low absorption cross-section. Additionally, a commercially available bulk [NaYF₄; Yb (20%), Er (3%)] upconversion sample was measured in the solid-state to provide a total radiant flux and absolute quantum yield standard. The measurements were accomplished utilizing a custom-engineered, multi-detector integrating sphere measurement system that can measure spectral sample emission in Watts on a flux-calibrated (W/nm) CCD-spectrometer, enabling the direct measurement of the total radiant flux without need for an absorbance or quantum yield value. </p><p>Also presented is the development and characterization of a scintillating nanocrystalline composition, [Y_2-xO₃; Eu_x, Li_y], in which Eu and Li dopant ion concentrations were systematically varied in order to define the most emissive compositions under specific x-ray excitation conditions. It is shown that these optimized [Y_2-xO₃; Eu_x, Li_y] compositions display scintillation responses that: (i) correlate linearly with incident radiation exposure at x-ray energies spanning from 40 - 220 kVp, and (ii) manifest no evidence of scintillation intensity saturation at the highest evaluated radiation exposures [up to 4 Roentgen per second]. X-ray excitation energies of 40, 120, and 220 kVp were chosen to probe the dependence of the integrated emission intensity upon x-ray exposure-rate in energy regimes where either the photoelectric or the Compton effect governs the scintillation mechanism on the most emissive [Y_2-xO₃; Eu_x, Li_y] composition, [Y_1.9O₃; Eu_0.1, Li_0.16]. These experiments demonstrate for nanoscale [Y_2-xO₃; Eu_x], that for comparable radiation exposures, when scintillation is governed by the photoelectric effect (120 kVp excitation), greater integrated emission intensities are recorded relative to excitation energies where the Compton effect regulates scintillation (220 kVp excitation). </p><p>The nanoscale [Y_1.9O₃; Eu_0.1, Li_0.16] was further exploited as a detector material in a prototype fiber-optic radiation sensor. The scintillation intensity from a [Y_1.9O₃; Eu_0.1, Li_0.16]-modified optical fiber tip, recorded using a CCD-photodetector or a Si-photodiode, was correlated with radiation exposure using a Precision XRAD 225Cx small-animal image guided radiation therapy (IGRT) system, an orthovoltage cabinet-irradiator, and a clinical X-ray Computed Tomography (CT) machine. For all x-ray energies tested from 80 - 225 kVp, this near-radiotransparent device recorded scintillation intensities that tracked linearly with total radiation exposure, highlighting its capability to provide alternately accurate dosimetry measurements for both diagnostic imaging and radiation therapy treatment. Because Si-based CCD and photodiode detectors manifest maximal sensitivities over the emission range of nanoscale [Y_1.9O₃; Eu_0.1, Li_0.16], the timing speeds, sizes, and low power-consumption of these devices, coupled with the detection element's linear dependence of scintillation intensity with radiation dose, demonstrates the opportunity for next-generation radiation exposure measuring devices for in/ex vivo applications that are ultra-small, inexpensive, and accurate.</p> / Dissertation

KOPIO is an experiment designed to search for the CP-symmetry-violating reaction K_L⁰ → π⁰νν̅. Measurement of the branching ratio of this reaction, depending on the accuracy of the measurement, could be the most precise measurement of the CP-violation parameters of the Standard Model to date. The K_L⁰ → π⁰νν̅ reaction is exceedingly rare, with an expected branching ratio of (2.6 ± 1.2) ·10⁻¹¹ . The rareness of this reaction means two things: 1) that we need prodigious numbers of kaons, and 2) that a multitude of "improper" decays will have to be screened out by means of a veto detector system, part of which is being designed here at Virginia Tech. This detector must be able to detect the passage of daughters of the undesired decay reactions (charged particles and gammas). It must be operational inside a magnetic field, and must have signal timing fast enough to accommodate the rate at which these decays occur. A detector consisting of alternating layers of scintillator and lead, with wavelength-shifting fibers embedded in the scintillator, provides the characteristics sought after. This paper presents methodology used in design and construction of this detector, as well as results of signal property tests, using both cosmic rays and gammas as event triggers. Also included is a discussion on transporting the detector signal outside of the magnetic field so it can be read by photomultiplier tubes resting outside of the sweeping magnet. / Master of Science

In this report the neutron-gamma discrimination capabilities of the new type of solid organic scintillator, EJ-299-33, was investigated using several pulse-shape discrimination (PSD) techniques. Among others, the analog zero-crossing method andthe digital charge-comparison and integrated-rise-time method were tested. The parameters of the digital PSD methods were optimised individually and the figure-of-merit was measured for each method and compared in different energy windows. The photoelectron yield of the setup was measured using two different photomultiplier tubes (PMT), a 3 inch diameter ET 9821 and a 5 inch diameter ET 9390KB. The highest photoelectron yield was measured with the ET 9390KB, which was the PMT used for the neutron-gamma discrimination capability measurements. In this work, four decay constants were found for the scintillator decay times. These were found by fitting average neutron and gamma-ray waveforms with the convolution of severeal exponential functions, that describes the light emission intensity of the scintillator, with an approximation of the PMT response function. Thebest agreement was found for the assumption that the scintillator light emission intensity is governed by four decay constants. The intensity of the two slowest components contain information about the incident particle.

Neutron diagnostics will play a fundamental role in future fusion plasma machines,where the harsh environment will make the use of many other type of diagnos-tics practically impossible. Complex techniques to measure the neutron spectrumemitted from tokamk plasmas have been developed over the years, producing stateof the art neutron spectrometers. However, recently compact neutron spectrom-eters have been gaining the interest of the research community. They are muchsimpler to operate and maintain, have lower cost and they can be employed in thechannels of a neutron camera, providing profile measurements. The drawbacks arethat they have a worse resolution and a response to neutrons that is not optimalfor spectroscopy.The goal of the work presented in this thesis is to estimate to which extenta compact detector such as a NE213 liquid scintillator can be used to performneutron emission spectroscopy analysis.The detector used for this study was installed in the back of the MPRu spec-trometer at JET in 2012. The characterization of the response of the detector wasdone using a combination of MCNPX simulations and real measurements. Thedata analysis was performed using the forward fitting approach: a model of theneutron spectrum is produced, then folded with the response of the detector andfinally compared with the data. Two types of plasma scenarios were analyzed, onewith NBI heating only, and another with NBI and third harmonic radio-frequencyheating. In both cases the TOFOR spectrometer was used as a reference to esti-mate the parameters in the model of the neutron spectrum.The results are promising and suggest that neutron spectroscopy can be per-formed with NE213 scintillators although the quality of the results, as given byperformance indicators such as uncertainties, is much lower than the performanceof high resolution spectrometers.

<p>The outcomes for both (i) radiation therapy and (ii) preclinical small animal radio- biology studies are dependent on the delivery of a known quantity of radiation to a specific and intentional location. Adverse effects can result from these procedures if the dose to the target is too high or low, and can also result from an incorrect spatial distribution in which nearby normal healthy tissue can be undesirably damaged by poor radiation delivery techniques. Thus, in mice and humans alike, the spatial dose distributions from radiation sources should be well characterized in terms of the absolute dose quantity, and with pin-point accuracy. When dealing with the steep spatial dose gradients consequential to either (i) high dose rate (HDR) brachytherapy or (ii) within the small organs and tissue inhomogeneities of mice, obtaining accurate and highly precise dose results can be very challenging, considering commercially available radiation detection tools, such as ion chambers, are often too large for in-vivo use.</p><p>In this dissertation two tools are developed and applied for both clinical and preclinical radiation measurement. The first tool is a novel radiation detector for acquiring physical measurements, fabricated from an inorganic nano-crystalline scintillator that has been fixed on an optical fiber terminus. This dosimeter allows for the measurement of point doses to sub-millimeter resolution, and has the ability to be placed in-vivo in humans and small animals. Real-time data is displayed to the user to provide instant quality assurance and dose-rate information. The second tool utilizes an open source Monte Carlo particle transport code, and was applied for small animal dosimetry studies to calculate organ doses and recommend new techniques of dose prescription in mice, as well as to characterize dose to the murine bone marrow compartment with micron-scale resolution.</p><p>Hardware design changes were implemented to reduce the overall fiber diameter to <0.9 mm for the nano-crystalline scintillator based fiber optic detector (NanoFOD) system. Lower limits of device sensitivity were found to be approximately 0.05 cGy/s. Herein, this detector was demonstrated to perform quality assurance of clinical 192Ir HDR brachytherapy procedures, providing comparable dose measurements as thermo-luminescent dosimeters and accuracy within 20% of the treatment planning software (TPS) for 27 treatments conducted, with an inter-quartile range ratio to the TPS dose value of (1.02-0.94=0.08). After removing contaminant signals (Cerenkov and diode background), calibration of the detector enabled accurate dose measurements for vaginal applicator brachytherapy procedures. For 192Ir use, energy response changed by a factor of 2.25 over the SDD values of 3 to 9 cm; however a cap made of 0.2 mm thickness silver reduced energy dependence to a factor of 1.25 over the same SDD range, but had the consequence of reducing overall sensitivity by 33%.</p><p>For preclinical measurements, dose accuracy of the NanoFOD was within 1.3% of MOSFET measured dose values in a cylindrical mouse phantom at 225 kV for x-ray irradiation at angles of 0, 90, 180, and 270˝. The NanoFOD exhibited small changes in angular sensitivity, with a coefficient of variation (COV) of 3.6% at 120 kV and 1% at 225 kV. When the NanoFOD was placed alongside a MOSFET in the liver of a sacrificed mouse and treatment was delivered at 225 kV with 0.3 mm Cu filter, the dose difference was only 1.09% with use of the 4x4 cm collimator, and -0.03% with no collimation. Additionally, the NanoFOD utilized a scintillator of 11 µm thickness to measure small x-ray fields for microbeam radiation therapy (MRT) applications, and achieved 2.7% dose accuracy of the microbeam peak in comparison to radiochromic film. Modest differences between the full-width at half maximum measured lateral dimension of the MRT system were observed between the NanoFOD (420 µm) and radiochromic film (320 µm), but these differences have been explained mostly as an artifact due to the geometry used and volumetric effects in the scintillator material. Characterization of the energy dependence for the yttrium-oxide based scintillator material was performed in the range of 40-320 kV (2 mm Al filtration), and the maximum device sensitivity was achieved at 100 kV. Tissue maximum ratio data measurements were carried out on a small animal x-ray irradiator system at 320 kV and demonstrated an average difference of 0.9% as compared to a MOSFET dosimeter in the range of 2.5 to 33 cm depth in tissue equivalent plastic blocks. Irradiation of the NanoFOD fiber and scintillator material on a 137Cs gamma irradiator to 1600 Gy did not produce any measurable change in light output, suggesting that the NanoFOD system may be re-used without the need for replacement or recalibration over its lifetime.</p><p>For small animal irradiator systems, researchers can deliver a given dose to a target organ by controlling exposure time. Currently, researchers calculate this exposure time by dividing the total dose that they wish to deliver by a single provided dose rate value. This method is independent of the target organ. Studies conducted here used Monte Carlo particle transport codes to justify a new method of dose prescription in mice, that considers organ specific doses. Monte Carlo simulations were performed in the Geant4 Application for Tomographic Emission (GATE) toolkit using a MOBY mouse whole-body phantom. The non-homogeneous phantom was comprised of 256x256x800 voxels of size 0.145x0.145x0.145 mm3. Differences of up to 20-30% in dose to soft-tissue target organs was demonstrated, and methods for alleviating these errors were suggested during whole body radiation of mice by utilizing organ specific and x-ray tube filter specific dose rates for all irradiations.</p><p>Monte Carlo analysis was used on 1 µm resolution CT images of a mouse femur and a mouse vertebra to calculate the dose gradients within the bone marrow (BM) compartment of mice based on different radiation beam qualities relevant to x-ray and isotope type irradiators. Results and findings indicated that soft x-ray beams (160 kV at 0.62 mm Cu HVL and 320 kV at 1 mm Cu HVL) lead to substantially higher dose to BM within close proximity to mineral bone (within about 60 µm) as compared to hard x-ray beams (320 kV at 4 mm Cu HVL) and isotope based gamma irradiators (137Cs). The average dose increases to the BM in the vertebra for these four aforementioned radiation beam qualities were found to be 31%, 17%, 8%, and 1%, respectively. Both in-vitro and in-vivo experimental studies confirmed these simulation results, demonstrating that the 320 kV, 1 mm Cu HVL beam caused statistically significant increased killing to the BM cells at 6 Gy dose levels in comparison to both the 320 kV, 4 mm Cu HVL and the 662 keV, 137Cs beams.</p> / Dissertation

In order to be able to determine neutrino mass hierarchy in the neutrino oscillation experiment JUNO we need to understand the dependence of the response of the signal from the scintillator on the deposited energy inside the scintillator. We measure the nonlinearity of the signal response via the Compton scattering inside the scintillator and via the precision gamma spectroscopy inside the HPGe detector. We observe effects of different parameters on the experiment via the Monte Carlo simulations. We also improve the data processing of the measured data and discuss what improvements of the experiment we can use in the future.

Single crystals with composition Lu3Al5O12 were synthesized using Czochralski and micro-pulling-down melt growth techniques. Polycrystalline ceramics of the same composition were synthesized by vacuum annealing of powders prereacted using a citrate-nitrate combustion technique and by spark-plasma-sintering of powders prereacted using a flame-spray-pyrolysis technique. Single crystals and polycrystalline ceramics are activated with Ce3+ or Pr3+ or doubly activated with Ce3+ and Tb3+ ions. Cerium-doped Czochralski-grown single crystals were compared to cerium-terbium codoped Czochralski-grown and micro-pulling down single crystals. Cerium-terbium codoped single crystals are also compared to similarly-activated polycrystalline ceramics sintered under vacuum using combustion-synthesized prereacted powders. X-ray diffraction analysis and fluorescence characterization were used to determine successful formation of single-phase LuAG and successful incorporation of doping species. Absorbance, fluorescence, radioluminescence, and scintillation decay analyses were used to compare synthesis processes and activator selection.

A scintillation counting system has been constructed with the use of BC-400 and EJ-212 series plastic scintillators along with a subminiature photomultiplier tube to investigate the effect of increasing plastic scintillator thickness on system-integrated counts. Measurements have been carried out using four different gamma sources with different energies ranging from 6keV to 1.332MeV and a Ni-63 beta source of maximum energy of 66keV. A simulation was also carried out in MCNP4a to verify the number of H-3 beta particles with max energy 18.6keV that would reach the plastic scintillator in a vacuum setting as well as in an air medium. Scintillator thicknesses ranged from 10μm to 2500μm. The response of the system was determined by measuring the integrated counts as a function of scintillator thickness. The results of these measurements showed the expected positive linear correlation between scintillator thicknesses and integrated counts for all the gamma sources while the slopes of the correlations of each gamma source was a function of the source energy. The beta particle response showed an initial increase of counts with scintillator thickness followed by a slight decrease. The MCNP simulation confirmed an analytical calculation of the fraction of H-3 beta particles for a given air concentration that would reach the scintillator. These results in conjunction with the experimental findings were used to assess the potential of a plastic scintillator system forming the basis of a tritium monitor for the detection of tritium in high-energy gamma backgrounds for Canadian nuclear power workers. / UOIT