Session PJ: Mini-symposium in Applications of Nuclear Physics II

A precise investigation of the ${}^{76}$Br decay for PET imaging

Radioisotopes are used in over 14 million medical imaging and therapy procedures each year. New isotopes are constantly introduced to optimize targeting or decay radiation. The dose of internal radiation is calculated from data which in some cases have not been updated for several decades. A thorough investigation of these isotopes using modern technologies and improved analysis techniques is vital to ensure accurate quantification of dose to patients. In this work, we explore the decay of ${}^{76}$Br, a ${\beta}^{+}$ emitter for PET (positron emission tomography), which is used with ${}^{77}$Br for therapy. A sample containing several isotopes of interest, including ${}^{76,77}$Br, was produced at the University of Wisconsin Medical School, shipped to Argonne National Lab, and assayed for 7 days using the Gammasphere detector array, running both analog and digital data acquisition systems simultaneously. More than 6 terabytes of data were collected from the $\sim$1MBq source. Analysis of this data set shows new strength to high-lying levels, and allows a reappraisal of the received dose as well as an investigation of count-rate advantages of digital Gammasphere.   

Systematic measurements of proton-induced reactions on enriched molybdenum

Between 2008 and 2010, shortages in the world-wide supply of Mo highlighted weaknesses in the current fission-based production method of $^{\mathrm{m}}$Tc, a critical medical isotope. This crisis sparked interest in developing the direct production of $^{\mathrm{m}}$Tc from proton-induced reactions on enriched Mo targets as an alternative. One complication with this method is that $^{\mathrm{m}}$Tc must be chemically extracted from the irradiated target. Therefore, radiopharmaceuticals produced from proton bombardment will contain a mixture of all Tc-species with open production channels, affecting radiochemical purity, specific activity and total production yield of $^{\mathrm{m}}$Tc---factors critical for the feasibility of this production method. Reactions on trace impurities in the enriched targets have been shown to impact these factors dramatically. Precise cross-section measurements for all Mo $+$p reactions that lead to Tc or Mo species are required for proper assessment of this production technique. Cross-section measurements for the main reaction of interest, $^{\mathrm{m}}$Tc(p,2n), have been performed in recent years, however, other reactions producing Tc have been mostly neglected. We will introduce a systematic study of proton-induced reactionson 92, 94-98, 100 Mo currently being performed at Notre Dame. Preliminary results will be presented.   

Calculation of in-target production rates for radioactive isotope beam production at TRIUMF

Rare Isotope Beam (RIB) facilities around the world, such as TRIUMF\footnote{TRIUMF, Canada's National Laboratory for Particle and Nuclear Physics, Vancouver BC}, work towards development of new target materials to generate exotic species. Access to these rare radioactive isotopes is key for applications in nuclear medicine, astrophysics and fundamental nuclear science. To better understand production from these and other materials, we have built a computer simulation of the RIB targets used at the TRIUMF Isotope Separation and ACceleration (ISAC) facility, to support new target material development. Built at Simon Fraser University, the simulation runs in the GEANT4\footnote{Agostinelli, S. et al., Nuc. Instrum. Meth. A 506 (2003) 250-303} nuclear transport toolkit, and can simulate the production rate of isotopes from a given set of beam and target characteristics. The simulation models the bombardment of a production target by an incident high-energy proton beam and calculates isotope in-target production rates different nuclear reactions. Results from the simulation will be presented, along with an evaluation of various nuclear reaction models and a experimentally determined RIB yields at the ISAC Yield Station\footnote{Kunz, P. et al., Rev. Sci. Instrum. 85 (2014) 053305}.   

Study of Cosmic Ray Muon Lateral Distribution with Geant4 Simulation

Cosmic ray radiation has galactic origin and consists primarily of protons and a small percentage of heavier nuclei. The primary cosmic ray particles interact with the molecules in the atmosphere and produce showers of secondary particles at about 15 km altitude. In recent years, with the advancement in particle detection technology, there is a growing interest of exploring the applications of cosmic ray muons ranging from Homeland Security, correlation study with the atmospheric weather, etc. A Geant4-based cosmic ray shower simulation is developed to study secondary cosmic ray particle showers in the full range of the Earth's atmosphere. In this talk, the diurnal and latitudinal variations of muon lateral distributions will be presented.   

Neutron activation analysis via nuclear decay kinetics using gamma-ray spectroscopy at SFU

Gamma-ray spectroscopy is a powerful tool used in a variety of fields including nuclear and analytical chemistry, environmental science, and health risk management. At SFU, the Germanium detector for Elemental Analysis and Radiation Studies (GEARS), a low-background shielded high-purity germanium gamma-ray detector, has been used recently in all of the above fields. The current project aims to expand upon the number of applications for which GEARS can be used while enhancing its current functionality. A recent addition to the SFU Nuclear Science laboratory is the Thermo Scientific P 385 neutron generator. This device provides a nominal yield of 3$\times$10$^{8}$ neutrons/s providing the capacity for neutron activation analysis, opening a major avenue of research at SFU which was previously unavailable. The isotopes created via neutron activation have a wide range of half-lives. To measure and study isotopes with half-lives above a second, a new analogue data acquisition system has been installed on GEARS allowing accurate measurements of decay kinetics. This new functionality enables identification and quantification of the products of neutron activation. Results from the neutron activation analysis of pure metals will be presented.   

Thin film deposition using rarefied gas jet

The rarefied gas jet of aluminium is studied at Mach number \textit{Ma }$=$\textit{ (U\textunderscore j / }$\backslash $\textit{sqrt\textbraceleft kb T\textunderscore j / m\textbraceright )}in the range \textit{.01 \textless Ma \textless 2}, and Knudsen number \textit{Kn }$=$\textit{ (1 / (}$\backslash $\textit{sqrt\textbraceleft 2\textbraceright }$\backslash $\textit{pi d\textasciicircum 2 n\textunderscore d H)} in the range \textit{.01 \textless Kn \textless 15}, using two-dimensional (2D) direct simulation Monte Carlo (DSMC) simulations, to understand the flow phenomena and deposition mechanisms in a physical vapor deposition (PVD) process for the development of the highly oriented pure metallic aluminum thin film with uniform thickness and strong adhesion on the surface of the substrate in the form of ionic plasma, so that the substrate can be protected from corrosion and oxidation and thereby enhance the lifetime and safety, and to introduce the desired surface properties for a given application. Here, $H$is the characteristic dimension, \textit{U\textunderscore j}and \textit{T\textunderscore j}are the jet velocity and temperature, \textit{n\textunderscore d}is the number density of the jet, $m$and $d$ are the molecular mass and diameter, and \textit{kb}is the Boltzmann constant. An important finding is that the capture width (cross-section of the gas jet deposited on the substrate) is symmetric around the centerline of the substrate, and decreases with increased Mach number due to an increase in the momentum of the gas molecules. DSMC simulation results reveals that at low Knudsen number \textit{((Kn }$=$\textit{ 0.01);}shorter mean free paths), the atoms experience more collisions, which direct them toward the substrate. However, the atoms also move with lower momentum at low Mach number$,$which allows scattering collisions to rapidly direct the atoms to the substrate.   

From Beamline to Scanner with $^{225}$Ac

Due to the high linear energy transfer and short range of alpha-radiation, targeted radiation therapy using alpha-emitting pharmaceuticals that successfully target small disease clusters will kill target cells with limited harm to healthy tissue, potentially treating the most aggressive forms of cancer. As the parent of a decay chain with four alpha- and two beta-decays, $^{225}$Ac is a promising candidate for such a treatment. However, this requires retention of the entire decay chain at the target site, preventing the creation of freely circulating alpha-emitters that reduce therapeutic effect and increase toxicity to non-target tissues. Two major challenges to $^{225}$Ac pharmaceutical development exist: insufficient global supply, and the difficulty of preventing toxicity by retaining the entire decay chain at the target site. While TRIUMF works towards large-scale (\~ Ci amounts) production of $^{225}$Ac, we already use our Isotope Separation On-Line facility to provide small ($<$ 1 mCi) quantities for in-house chemistry and imaging research that aims to improve and assess $^{225}$Ac radiopharmaceutical targeting. This presentation provides an overview of this research program and the journey of $^{225}$Ac from the beamline to the scanner.   

Renewing Liquid Fueled Molten Salt Reactor Research and Development

Globally there is a desperate need for affordable, safe, and clean energy on demand. More than anything else, this would raise the living conditions of those in poverty around the world. An advanced reactor that utilizes liquid fuel and molten salts is capable of meeting these needs. Although, this technology was demonstrated in the Molten Salt Reactor Experiment (MSRE) at ORNL in the 60’s, little progress has been made since the program was cancelled over 40 years ago. A new research effort has been initiated to advance the technical readiness level of key reactor components. This presentation will explain the motivation and initial steps for this new research initiative.   

Ion Diffusion in Battery Materials Probed with $\beta$NMR and $\mu$SR

Radioactive beam magnetic resonance techniques, $\beta$-detected NMR ($\beta$-NMR) and muon spin rotation and relaxation ($\mu$SR), have been used to study the microscopic diffusion of lithium ions and muons (Mu$^+$), which can be considered light protons, in poly(ethylene oxide) (PEO), a common polymer electrolyte in lithium ion batteries. $\beta$-NMR measurements were performed on thin films of PEO with lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) and lithium trifluoroacetate (LiTFA) with monomer-to-salt ratios of 8.3. Hopping of $^8$Li$^+$ above $\sim$250 K follows an Arrhenius law in all of the films. The diffusion parameters of $^8$Li$^+$ in the salt-containing films are strongly correlated with the ionicity of the lithium salt rather than the glass transition temperature of the sample. The intrinsic hop rate increases exponentially with ionicity, while the activation energy for hopping increases approximately linearly going from $6.3 \pm 0.2$ kJ/mol in PEO:LiTFA to $17.8 \pm 0.2$ kJ/mol in PEO:LiTFSI. $^8$Li$^+$ diffusion is fastest in pure PEO. Hopping of Mu$^+$ is observed in pure PEO above the glass transition temperature with an activation barrier of $11.8 \pm 0.1$ kJ/mol.