Scott Joffre – 2016

Joffre_3Characterization of Cation Intercalation in Surface Bound Prussian Blue Analogues

Research Advisor: Dr. Jennifer Hampton

With the increasing popularity of handheld, rechargeable devices (such as smartphones) the demand for Lithium-ion batteries has also increased to fill this need. Alternative battery types provide an opportunity to lower costs by using more earth abundant elements. Prussian Blue Analogue (PBA) films are one alternative that have the benefit of admitting a more diverse range of ionic intercalants than lithium. This study focuses on the characterization of PBA films which are exposed to a variety of cations (Li+, Na+, K+) that differ from the initial solution in which they were created. We found that some films would exhibit enhanced features, such as, a larger charge capacity. Preliminary results demonstrate that some cation intercalants are more kinetically favorable, and out-compete each other for interstitial site occupation within the PBA lattice. Further research could look to the effect of using 2+ ions (Mg2+ and Ca2+) as the intercalant.

This material is based upon work supported by the Hope College Department of Physics, the Hope College Dean for Natural and Applied Sciences Office, and the National Science Foundation under NSF-MRI Grant No. CHE-0959282.

Jacob Pledger – 2016

PledgerCrystalline Channeling of MeV Ion Beams

Research Advisor: Dr.Stephen Remillard

Thin films of strontium titanate (SrTiO3) on single crystal magnesium oxide (MgO) substrate and strontium manganate (SrMnO3) also on single crystal MgO substrate are being considered for use in engineered superlattices. These superlattice structures exhibit unique properties which make them valuable in the semiconductor industry as well as applications which require a high sheering resistance. Crystal matching of the films to the substrates, which is essential for a low defect density, is indicated by effective channeling of ion beams through the lattice. Ion beam channeling, which occurs when the beam’s incidence angle is parallel to crystal planes, can occur in well-ordered and pure crystals. With the addition of the ability to control the azimuthal angle as well as the altitudinal angle, two dimensional rastering of the incident angle is achieved. Comparison of the backscattering yields at different incident altitudinal and azimuthal angles shows a drop in yield as the channeling angle is approached. Channeling is seen in both the bulk SrTiO3 and MgO samples, although the yield suppression revealed structure around normal incidence. This structure is observed to be consistent between two MgO samples obtained from different suppliers and has different spacing in peaks than the SrTiO3 sample.

This research was supported in part by an award to Hope College from the Howard Hughes Medical Institute through the Undergraduate Science Education Program and by the Hope College Department of Physics.

Alec Nelson – 2016

Nelson_3Scanning of the Intermodulation of Superconductor Resonators

Research Advisor: Dr. Stephen Remillard

At the resonant frequency, superconductor resonators produce intermodulation distortions, smaller signals near the resonant frequency. By inducing external microwave signals, it is possible to analyse the patterns of intermodulation distortions (IMD) in several different types of superconductor resonators. These measurements can be used to complement the main peak values like quality factor and frequency shift in order to understand nonlinearities present in the material of the superconductor. Once spatial distributions of IMD have been identified, they can be used to interpret IMD signals from unknown superconductors and identify various defects in the crystal structure. Using a probe outputting two combined tones into the resonator, it was possible to map the whole of a two-dimensional resonator, using the IMD as the z-direction. In order to best resolve the intermodulation distortions, two superconductors were imaged, a hairpin wide-line resonator and a thin, line resonator. A contour plot of the data was then generated, which displays the IMD of the given resonator.

Funding for this project was provided by The Hope College Natural and Applied Sciences Division and Award number DMR-1505617 from the National Science Foundation.

Caleb Sword – 2016

Sword_3Determining the Nuclear Structure of an Unstable 25O Isotope

Research Advisor: Dr. Paul DeYoung

One of the primary goals of nuclear physics research is to better understand the force that binds nucleons. This can be accomplished by studying the structure of neutron-rich isotopes. For this experiment, excited 25O nuclei were formed by a collision between a 101.3 MeV/u 27Ne ion beam and a liquid deuterium target at the National Superconducting Cyclotron Laboratory. One resulting reaction involved two-proton removal from 27Ne particles, which created excited  25O nuclei that decayed into three neutrons and an 22O fragment. The four-vectors for the neutrons and 22O fragments were determined, allowing the calculation of the decay energy for this process on an event-by-event basis. However, another reaction would also take place, in which an alpha particle was stripped from the beam, creating 23O nuclei that decayed into an 22O fragment and a single neutron. In order to distinguish between 22O fragments and neutrons from both 25O and 23O isotopes, members of the MoNA collaboration are conducting GEANT4 simulations of each decay process in order to uncover their distinguishing characteristics. By successfully correlating simulated decay processes to experimental data, the relative cross sections of the two decay processes will be determined, and their decay energies will reveal more about their nuclear structures.

This work is supported by the National Science Foundation under grants No. PHY-1306074 and No. DUE-1153600; and by the Hope College Division of Natural and Applied Sciences and the Hope College Department of Physics.