The ocean under Europa’s crust has the possibility of harboring life. Using the available energy, I have made an estimation of the possible biomass on Europa. The available energy was calculated using the available oxidants (O₂ and SO₄^2-) and reductants in the system (H₂). This was then compared to estimates for the amount of energy life needs to survive. The estimated biomass would result in a much smaller cell density in Europa’s oceans than in Earth’s oceans; however, it is most likely that any biomass on Europa would be concentrated where there is available energy instead of being evenly spread throughout.

DAMIC-M is a next-generation experiment to search for dark matter with charge coupled devices (CCDs) in the Modane Underground Laboratory in France. The final DAMIC-M experiment will feature a tower of fifty of the most massive CCDs ever built. These devices will implement a newly developed "skipper" readout mechanism, where ionization charge collected by each pixel in the CCD is measured many times over. The ultra-low noise achieved by the skipper CCDs will provide an improvement of several orders of magnitude in the exploration of the dark matter particle hypothesis, in particular of candidates pertaining to the so-called "hidden sector". To decrease interference from environmental radiation, the CCDs must be encased in low radioactivity electroformed copper. Electroformed copper is grown cylindrically, then flattened to create stackable trays that hold the CCDs. Because the DAMIC-M CCD tower will be operated at a temperature of 100 K, cooling might cause the flattened copper to warp about the axis of the cylindrical stock material. By taking various height profile measurements using a laser interferometer and a dial indicator, I quantified the deviations from flatness caused by the cooling of the trays. The results showed some warping around the corners of the tray, likely due to the measurement apparatus, but no significant warping about the axis of the cylindrical stock copper.  The warping at the corners was likely due to the substance used to hold the tray in place while the measurement was being taken.  While this complication was not ideal, it could be removed in analysis, allowing us to see that the results still showed what we were looking for, that the trays were not warping about the axis of the cylindrical stock copper.

The prospect of life on the icy ocean world of Europa is an exciting one. A common theory is that hydrothermal vents could produce the necessary reductants for chemosynthesis to take place on the ocean bottom. However, future missions to probe for life will initially focus on the icy surface and the ocean just below the ice. We propose a ‘viral elevator’, a mechanism which functions similarly to the ‘viral shunt’ in Earth’s oceans, which could create and shuttle dissolved organic matter (DOM) to the surface through viral carriers. Current studies model Europa’s ocean with a system of currents and a sub-ice freshwater layer (Soderlund et al. 2014, Zhu et al. 2017). Our calculations demonstrate that the viral elevator could feasibly move DOM through a combination of the ocean currents and diffusion through the freshwater layer. The end goal of this research is to create a functioning model for virus-bacteria dynamics in Europa’s ocean, based on the influx rate of DOM from the viral elevator. We have modified an existing closed-system model (Max Showalter, UW) for viral and bacterial populations in Earth’s sea ice to fit the open-system environment of Europa’s surface ocean. Our new model shows how the virus-bacteria ratio changes given likely parameters for Europa’s ocean.

The Project 8 experiment to measure the mass of the neutrino using beta decays of tritium (hydrogen-3) requires the use of several cold-head cryocoolers in order to maintain the required cryogenic temperatures. As the cryocoolers themselves undergo mechanical wear during normal function, it is helpful to monitor their activity in order to assess the condition of the cryocoolers over time. Borrowing from a technique first illustrated in a paper by a German group, my mentor and I have programmed and installed a vibrational analysis system that takes daily measurements on two of the laboratory cold-head cryocoolers, generating an activity envelope at their characteristic frequencies. Piezoelectric sensors attached to the cold-heads generate electrical pulses in response to mechanical stress: 57,312 data points measured over 5.5 seconds--which allows for a frequency spectrum analysis of up to 5000 Hz-- are relayed to an Arduino device and then transmitted to the console. The data sets allow us to generate spectrograms of mechanical activity in both cold-heads; from the spectrograms we can determine their characteristic vibrational frequencies and run the data through a band-pass filter in order to create activity envelopes. By comparing the measurements and activity envelopes over time, we will be able to monitor the cold-heads for mechanical wear and failure.

This project aims to develop the equipment and techniques to study the effects of linear strain on nanoscale materials. Nanoscale layered van-der Waals materials are first isolated by mechanical exfoliation down to the two-dimensional (2D) limit. These 2D materials offer a diversity of interesting properties like magnetism, superconductivity, and topological phases. Furthermore, these interesting phenomena may be tuned by changing conditions such as interlayer spacing, crystal symmetry, and stacking order. Uniaxial strain presents an enticing method for in-situ tuning of these properties. Recent attempts to apply strain to 2D materials have relied on the use of bendable substrates, which has limited the application of strain at cryogenic temperatures. Consequently, the unique physics of highly strained atomically thin materials has gone unexplored. Our project utilizes a piezoelectric strainer which allows for extreme tensile and compressive cryo-strain and is compatible with both optical and electrical probing techniques. We report the development of techniques and hardware to fabricate and measure 2D strain samples, as well as preliminary strain studies of the 2D layered antiferromagnet chromium triiodide (CrI₃). Theoretical predictions promise drastic changes to Cr_I3’s magnetism, crystal structure, and optical response which we intend to explore with uniaxial strain. Our ongoing and future research aims to bring versatile and reliable strain to the nanoscale regime, which could contribute to the discovery of novel physics in the plethora of 2D materials studied at the University of Washington and around the world.

Lightning is an intensely energetic phenomena that causes substantial loss of life and property. Lightning also perturbs atmospheric composition that regulates the natural cleansing power of the atmosphere and plays a key role in the natural fire cycle of ecosystems. Lightning changes the atmospheric composition by emitting nitrous oxides, a gas that contributes to the Earth’s warming in the ozone. Microscopic particles in the atmosphere, known as aerosols, act as cloud condensation nuclei (CCN). More aerosol particles, such as due to air pollution, lead to more, smaller cloud droplets when clouds form. More, smaller cloud droplets have been theorized to cause more collisions between cloud ice and liquid droplets and thus more charge separation in cumulonimbus (or thunderstorm) clouds which may be correlated with a greater frequency of lightning. We are analyzing global patterns in lightning frequency that may be influenced by variations in aerosol particle pollution. We are using data from the World-Wide Lightning Location Network (WWLLN), a network of stations that detects lightning from the specific frequencies of electromagnetic radiation it emits and that travel through the atmosphere. Our results indicate that some tropical urban areas have an increased lightning frequency, up to a factor of 7, when compared to the surrounding area. The results suggest that human activity can be linked with increased lightning with implications for climate, air quality, and wildfire frequency.

The generation of light at harmonic frequencies due to the non-linear interaction between a material and an electric field plays a critical role in several new technologies including ultra-short laser pulse shaping, spectroscopy, and quantum information networks. Gallium-Phosphide ring resonators can effectively convert incident light from visible to telecommunications band wavelengths, but nanoscale fabrication differences in the dimensions of ring resonators can significantly change the devices’ optimal resonant wavelengths. Unless these devices can perform optimally at uniform wavelengths, they cannot be implemented as part of any large-scale system. Post-fabrication etching methods could be used to change the width of the resonators and fine-tune their resonant frequencies. Diffusion-limited wet etching has been shown to remove angstroms-thick layers from III-V semiconductors similar to Gallium Phosphide. Hydrogen peroxide and acid solutions are alternately applied to form and remove oxide layers, reducing the width of the resonators by tens of angstroms each etching cycle. The shift in resonances near nominal wavelengths of 775 and 1550 nm after each etching cycle are measured and compared to simulated results.