Our research group performs one of the highest-precision tests of Einstein’s equivalence principle, perhaps the most fundamental property of gravitation, using a sensitive rotating torsion balance. Among the leading experimental challenges are temporal and spatial temperature variation. Notably, horizontal temperature gradients across the apparatus, if not properly characterized, can emulate an equivalence-principle violating signal. We have implemented thermal shielding and run tests to measure the thermal effects on our measurement. Past tests have shown a need for both absolute and differential temperature sensors with higher sensitivity. Hence, my research project focuses on investigating the effect of temperature gradient on our experiments by constructing a thermal monitoring system. I have designed, laid out, constructed, and tested sensitive bridge thermistor circuits that can function as both absolute and differential temperature sensors. Current tests of our prototypes have shown that temperature sensitivities reaching 10 micro-Kelvin in one second (10^-5K/Hz^0.5). We are scaling-up these sensors and plan to deploy them in this academic year. Successful completion of this project will yield improved understanding of the temperature gradients within our experimental apparatus, allowing us to test the equivalence principle with yet higher precision.

Here at the University of Washington we are characterizing one ton of NaI[Tl] crystal scintillator detectors for use in the COHERENT project. NaI[Tl] scintillating crystals detectors work by producing photons from the kinetic energy of charged particles passing through the scintillating material. COHERENT aims to detect coherent elastic neutrino-nucleus scattering, a novel interaction between neutrinos and matter that was first observed less than two years ago. It employs a large scale of scintillator detectors in order to record these events at an appreciable scale. Our characterization campaign allows us to group crystals with similar outputs by voltage which will determine the setup of our detectors once at ORNL. During this characterization, the crystals exhibited behaviors that correlated with the ambient temperature of the lab. The temperature dependence was first noticed during voltage gain characterization tests taken at different times of the day in the uncontrolled temperature environment of our lab. We expect the gain of our crystals to fit to a curve function, which breaks down if data is taken at different times of the day. The goal of this study is to understand the impact of temperature dependencies on our characterization campaign, and in particular to derive a relationship between voltage gain and temperature. I will present the data gathered toward this goal, and also our larger body of data on the relationship between light yield, voltage gain, peak resolution, and waveform rise time, as well as the techniques used to re-characterize previous crystals gain curve based on the derived relationship from this study.

At the UW tandem particle accelerator located at the Center for Nuclear Physics and Astrophysics (CENPA), a program is searching for new physics though precision measurements of electron spectra from radioactive decays. The most sensitive searches require very pure Neon-19, which has a halflife of about 17 seconds. Accordingly, we have designed and constructed a system that produces Neon-19. We first bombarded Sulphur Hexafluoride (SF₆) with protons from the accelerator. We then metered the SF₆ and Neon-19 mix out into a cryogenic trap where it freezes only the SF₆. After the trap, we transported the remaining Neon-19 with a turbomolecular pump into the detector. Once the trap had filled with solid SF₆, it was valved off from the target, then heated, at which time the frozen SF₆ sublimated into to a storage tank before refilling the target. By using a pair of traps, the experiment can be run continuously; one trap thaws while the other freezes. Through models based on nuclear cross-section data from previous experiments, the system will produce on the order of 10¹⁰ Neon-19 nuclei per second. Our system will contribute to an effort to better describe the interactions of particles and refine the Standard Model of particle physics.

Isotropic scattering in various spatial dimensions is considered for arbitrary finite-range potentials using non-relativistic effective field theory. With periodic boundary conditions, compactifications from a box to a plane and to a wire, and from a plane to a wire, are considered by matching S-matrix elements. General relations among (all) effective-range parameters in the various dimensions are derived through a functional relationship, and the dependence of bound states on changing dimensionality are considered. This research was conducted by matching the effective range parameters in one dimension to the particle scattering within another dimension. This relationship ultimately leads to the immediate functional relationship of the effective range parameters in varying dimensions. Generally, it is found that compactification binds the two-body system, even if the uncompactified system is unbound. For instance, compactification from a box to a plane gives rise to a bound state with binding momentum given by ln(1/2(3 + √5)) in units of the inverse compactification length. This binding momentum is universal in the sense that it does not depend on the two-body interaction in the box. This research will in the future allow for the calculations of practical and important thermodynamic variables such as pressure, energy of Bose gases with varying lengths of a three dimensional box.

HIT-SI, also know as steady-inductive helicity-injected torus experiment, uses three coplanar inductive helicity injectors to form and sustain a spheromak equilibrium. Spheromak is a configuration of the plasma that forms  into a shape of smoke ring and it is a promising approach to nuclear fusion energy based on its long confinement time and the confinment achieved by the self-induced current. This project is centered around data analysis from a new tomography diagnostic system to assess the symmetry of spheromak plasma density while varying the key current drive parameters of the HIT-SI3 plasma physics and fusion energy.  The tomography diagnostic system consists of four toroidal chord fans and three sets of three poloidal fans that provide 3D plasma emission information. Each fan expands from 130 degree wide angle lenses coupled to bundles of fiber optics. The light collected by the fiber optics is split, filtered at 668 nm and 728 nm, and imaged by a high-speed camera. Since the ratio of the 668/728 nm emission has a strong plasma density dependence within the range of typical HIT-SI3 plasma parameters, the 3D emissivity profile constructed by inverting line-averaged emissivity along chords can be related to the plasma density profile. The objective of this project is to find the correlations between parameters affecting wall conditioning and the plasma density profile, then use the results from the analysis to maximize the performance of the plasma toward the goal of improving confinement. The initial analysis will include all available data covering a variety of experimental plasma conditions. After the correlation is established from the initial analysis, a series of carefully controlled experiments will be conducted to test and improve the certainty of the initial results. In the controlled experiments, plasma discharges will be taken under more specific settings so the effects of different conditions on the plasma profile can be isolated and better understood.

High purity germanium (HPGe) detectors are an important technology in several leading experimental searches for dark matter and neutrinoless double beta decay. Understanding the interaction of various types of radiation on the different surfaces of HPGe detectors is essential to developing methods to reject unwanted signals from radioactive background sources. I have taken a leading role in the construction and use of the Collimated Alphas, Gammas, and Electrons (CAGE) test stand at the University of Washington, whose goal is to evaluate the response of an HPGe detector to different types of radiation on its various surfaces. CAGE is a vacuum cryostat with an internal system of motors that move a radiation source while keeping the detector active. It requires the operation of a liquid nitrogen cryostat, vacuum pump, temperature sensors, and various radioactive sources, all of which must be integrated into a single data acquisition (DAQ) system. We are currently constructing this system, fabricating and installing parts, and are planning to take initial data with the HPGe detector in the summer. In this talk I will present the current status of the CAGE detector, as well as preliminary data from radiation signals in the detector.

The Lyman-alpha power spectrum has previously been used to constrain the Universe’s initial conditions and particle constituents (such as the amount and mass of the dark matter) and the temperature of intergalactic gas (which constrains reionization processes). To further improve these constraints, we use another Lyman series transition (Lyman-beta). The Lyman-beta absorption cross-section is lower than that of Lyman-alpha so it probes the intergalactic medium at higher densities where Lyman-alpha features are saturated. Therefore, the Lyman-beta forest allows for a better measurement of the slope of the temperature-density relation, allowing additional constraints on reionization and the subsequent thermal evolution. In this work, we present an analysis of the Lyman-beta power spectrum using the VLT/XSHOOTER XQ-100 Legacy Survey.