Anna Wormmeester – 2016

Wormmeester_2Spectroscopic Emission from Argon and Nitrogen Microplasmas

Research Advisor: Dr. Stephen Remillard

Many electronics utilize microgaps, and these electronics can produce plasma, whether intended or not, if it was not intended this plasma can damage the electronics. The breakdown condition and spectral emission of nitrogen and argon plasmas were examined in a microgap under microwave excitation. The differences of the plasma discharge were studied in three different microgap sizes, using nitrogen and argon. The breakdown condition was defined as the input power that ignites microplasma, and the breakdown condition exhibited three distinct pressure domains. These three domains were: under 10 torr, 10 – 300 torr and 300 – 700 torr.   A diffraction grating spectrometer was used to test nitrogen and argon by exploring the emission spectra and by comparing the spectra from microgaps to large gaps, revealing peak oppression and enhancement in the microgaps. This enhancement is shown at a gap of 15μm and is then oppressed at a gap of 1.6mm, at a wavelength of 414nm with a 4 -> 5 vibration transition, and at 426nm with a 1 -> 5 vibration transition in N2. This is also shown in Ar at wavelengths of 591.2nm and 419.8nm.

This work was supported by the Hope College Dean for Natural and Applied Sciences and the Hope College Department of Physics, and is based on earlier support from the Michigan Space Grant Consortium.

Jason Gombas – 2016

GombasRefining the r-process Described by Theoretical Models

Research Advisor: Dr. Paul DeYoung

Where did all of the heavy elements originate? The rapid neutron capture process (r-process), currently only characterized by theoretical calculations, model the nuclear reactions that lead to heavier nuclei in intense astrophysical locations such as supernovas. Experimenting with the few reactions reproducible on Earth can refine the theoretical calculations of reactions currently impossible to replicate. A cocktail beam of heavy nuclei associated with the r-process around 104Nb with a magnetic rigidity of 3.2097Tm was produced at the National Superconducting Cyclotron Laboratory. The beam implanted in an energy and position detector located inside an efficient gamma detector called the Summing NaI(Tl) detector (SuN). Beta-decay events were correlated to implantation events to identify the A and Z of the decayed nucleus. Using the correlated gamma-ray energies measured in SuN, values such as the beta-decay intensity distribution will then be calculated and compared to values predicted by models that are used to calculate the abundance distribution of the various nuclei observed today.

This material is based upon work supported by the National Science Foundation under grant No. PHY-1306074

Anna Lunderberg – 2016

LunderbergExploring the Effects of Copper on Composition and Charge Storage of Prussian Blue Analogue Pseudocapacitors

Research Advisor: Dr. Jennifer Hampton

As energy usage has increased in recent years, there has been great demand for efficient, cost-effective, and earth-abundant materials to be used for energy storage. The ability to produce hexacyanoferrate (HCF) modified nickel film for use as a pseudocapacitor has already been demonstrated. This project focuses on the effects on the modification procedure and the resulting material of adding copper to the nickel metal film. A NiCu film was deposited onto a gold substrate with a controlled potential electrolysis experiment, then was modified and characterized with a cyclic voltammetry experiment. The composition was determined with a scanning electron microscope with energy dispersive x-ray spectroscopy before and after the modification process. Copper was selectively removed in some cases as a result of the modification. With increased levels of copper, the material can become structurally unsound and result in unintentional stripping of the material. Preliminary data suggests that as the pre-modification level of copper is increased, the resulting charge storage of the HCF film increases as well.

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

Richard Huizen – 2016

Huizen_2Evidence for Distinct Sources of Superconducting Nonlinearity

Research Advisor: Dr. Stephen Remillard

The nonlinear response of cuprate superconducting devices present technological hurdles and scientific opportunities.  Intermodulation Distortion (IMD) generated by the nonlinear response is usually undesirable in superconducting devices, however, some devices leverage IMD to their advantage.  By analyzing the magnetic relaxation of IMD in a YBa2Cu3O7 (YBCO) superconducting thin film, the effect of magnetic fluxon dynamics on nonlinear response reveals information about the origins of nonlinearity.  A carrier wave, resonant with the YBCO superconducting circuit, and two off-resonance probe signals were injected into the resonator.  The combination of these three signals locally excited synchronous second and third order IMD (IMD2 and IMD3).  Upon removal of an applied static magnetic field, IMD3 relaxed with a single decay mode while IMD2 relaxed with slow and fast decay modes that are temperature dependent.  The slow process in the IMD2 decay transitioned from concave down to concave up as the superconductor warmed through an inflection temperature.  This temperature dependent transition of decay modality in IMD2 is due to crossing over either the irreversibility line or the surface barrier activation line.  IMD2 and IMD3 exhibited unique dependencies on temperature and magnetic field, therefore, even and odd order nonlinearities must result from different physical mechanisms.

This work was supported by grant No. DMR-1505617 from the National Science Foundation.

Grant to Nuclear Group Continues Three Decades of NSF Support

A new major research grant from the National Science Foundation (NSF) to the Nuclear Group at Hope College continues three decades of support from the agency, a long-time run which if not unique is at the very least rare, reflecting the quality of the work being conducted.

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