Development of Metallic Magnetic Calorimeters and Paramagnetic Alloys of Ag and Er for Gamma-Ray Spectroscopy

A Metallic Magnetic Calorimeter (MMC) is a cryogenic calorimetric particle detector that employs a metallic paramagnetic alloy as the temperature sensor material. MMCs are used in many different applications, but this work will focus on their uses in high energy resolution gamma-ray spectroscopy. This technology is of great interest to the field of Nuclear Forensics and Nuclear Safeguards as a non-destructive assay for isotopic analysis of nuclear samples. The energy resolution of MMCs is an order of magnitude higher than the benchmark High Purity Germanium (HPGe) detectors that are currently used in the field and MMCs are also poised to outperform the current leading microcalorimeter, the Transition Edge Sensor (TES). This dissertation will cover the work in development of paramagnetic alloys of Ag and Er as the sensor material, and testing of two generations of devices. The heart of the MMC is the paramagnetic sensor material. The workhorse paramagnet for MMCs is currently an alloy of Au and Er. Although Au:Er is a high performing alloy, it starts to falter at the temperatures below 100 mK which are desirable to maximize the performance of the MMC. Au has a nuclear electric quadrupole moment, which at low temperatures, has its energy levels split by the radial electric fields created by the Er ions. This effect causes the specific heat of the alloy to increase as temperature is lowered, which diminishes device performance. A promising alternate paramagnet is an alloy of Ag and Er. Ag, with both naturally occuring isotopes having a nuclear spin of I=1/2, does not have a nuclear electric quadrupole moment. A technical challenge to working with Ag is that it has such a high affinity for oxygen that the usual method of creating Au:Er alloys may not be sufficient for Ag:Er. Much greater care has to be taken in removing oxygen from the alloy, as during creation the oxygen could adversely alter the Er dopant, thus degrading performance. To combat this, a vacuum induction furnace was developed to achieve the best possible control over synthesis process parameters. Description of the new furnace and test results from a successful synthesis of a Ag:Er alloy are discussed. The other half of the MMC is a high-performing Superconducting Quantum Interfence Device (SQUID) magnetometer. In previously reported devices, it was standard to have the sensing coil, magnetizing circuit, and paramagnet be on a separate chips from the SQUID magnetometer. The approach taken at UNM has been to integrate the SQUID magnetometer and paramagnetic sensor onto a single chip. Having an integrated device increases the performance of the MMC, at the cost of a more difficult fabrication process. Two exploratory wafers of magnetometers have been fabricated and tested for use as MMCs. The first wafer is a set of exploratory two-pixel devices, varying almost every aspect of the device to search for optimal device parameters. The second wafer consists of 14-pixel MMC arrays. A process of electroplating gold absorbers to the devices that now contain sensitive SQUIDs has been developed, using a two-mold system to define the legs and body of the absorbers. An initial Fe-55 spectrum from one of the new arrays is shown as a proof of concept measurement

Dressed-State Resonant Coupling between Bright and Dark Spins in Diamond

Under ambient conditions, spin impurities in solid-state systems are found in thermally mixed states and are optically “dark”; i.e., the spin states cannot be optically controlled. Nitrogen-vacancy (NV) centers in diamond are an exception in that the electronic spin states are “bright”; i.e., they can be polarized by optical pumping, coherently manipulated with spin-resonance techniques, and read out optically, all at room temperature. Here we demonstrate a scheme to resonantly couple bright NV electronic spins to dark substitutional-nitrogen (P1) electronic spins by dressing their spin states with oscillating magnetic fields. This resonant coupling mechanism can be used to transfer spin polarization from NV spins to nearby dark spins and could be used to cool a mesoscopic bath of dark spins to near-zero temperature, thus providing a resource for quantum information and sensing, and aiding studies of quantum effects in many-body spin systems.Engineering and Applied SciencesPhysic

X-RAY SPECTROSCOPY OF BROMINE COMPOUNDS AND BIOMEDICAL APPLICATIONS

Author Institution: Dept of Astronomy, Ohio State University; Biophysics Program, Ohio State University; Dept of Astronomy, Ohio State University; Physics Dept, Ohio State University; Dept of Chemistry,Ohio State University, Columbus, OH 43210; Catholic University of ChileIn conventional biomedical applications intense and broadband high energy X-rays are used in therapy and diagnostics (theranostics) to ensure sufficient tissue penetration for imaging or treatment. To avoid damages incurred by these, our proposed method, {\it Resonant Theranostics}$^{b,c}$, aims to find narrow energy regions that corresponds to {\em resonant} absorption or emission. We show that such energy bands lie {\it below} the K-shell ionization energy, contrary to the research focus on the K-shell ionization energy itself. Targeting these energy bands, Auger processes can be initiated to produce a number of photons and electrons from each atomic/molecular species via photon fluorescence and electron ejections. We will report our study on the bromine compound bromodeoxyuridyne (BUdR), widely used as radiological contrast agent in radiation imaging. The active system is Br$^o$-Br$^+$ combination, which can emit or absorb X-rays in the relative narrow energy range of 12 to 13.6 keV, through 1s-np transitions. We will present the oscillator strengths and transition probabilities for various Auger or K-shell $1s-np$ transitions. We will show that the corresponding cross sections and attenuation coefficients per unit mass, are orders of magnitude higher than the background and that at K-shell ionization energy. Employing these attenuation coefficients in the Monte Carlo simulation program Geant4, we study the intensities of photon and electron emission spectra

Prevalence and Factors Associated With Mental Health Symptoms in Adults Undergoing Covid-19 Testing

BACKGROUND AND OBJECTIVE: Understanding the mental health impact of the COVID-19 pandemic on persons receiving COVID-19 testing will help guide mental health interventions. We aimed to determine the association between sociodemographic factors and mental health symptoms at 8 weeks (baseline) after a COVID-19 test, and compare prevalence of mental health symptoms at baseline to those at 16-week follow-up. MATERIALS AND METHODS: Prospective cohort study of adults who received outpatient COVID-19 testing at primary care clinics. Logistic regression analyses were used to assess the association between sociodemographic characteristics and COVID-19 test results with mental health symptoms. Mental health symptoms reported at baseline were compared to symptoms at 16 weeks follow-up using conditional logistic regression analyses. RESULTS: At baseline, a total of 124 (47.51%) participants reported at least mild depressive symptoms, 110 (42.15%) participants endorsed at least mild anxiety symptoms, and 94 participants (35.21%) endorsed hazardous use of alcohol. Females compared to males were at increased risk of at least mild depressive symptoms at baseline (Adjusted Odds Ratio (AOR): 2.08; 95% CI: 1.14-3.79). The odds of at least mild depressive symptoms was significantly lower among those residing in zip codes within the highest quartile compared to lowest quartile of household income (AOR: 0.37; 95% CI: 0.17-0.81). Also, non-Hispanic Whites had significantly higher odds of reporting hazardous alcohol use compared to non-Whites at baseline (AOR: 1.94; 95% CI: 1.05-3.57). The prevalence of mental health symptoms remained elevated after 16 weeks. CONCLUSION AND RELEVANCE: We found a high burden of symptoms of depression and anxiety as well as hazardous alcohol use in a diverse population who received testing for COVID-19 in the primary care setting. Primary care providers need to remain vigilant in screening for symptoms of mental health disorders in patients tested for COVID-19 well after initial testing