Department of Physics, UW-Madison
http://digital.library.wisc.edu/1793/8332
Materials from the Department of Physics2021-09-21T06:03:59ZAdvances in Fetal Magnetocardiography Using SERF Atomic Magnetometers
http://digital.library.wisc.edu/1793/79209
Advances in Fetal Magnetocardiography Using SERF Atomic Magnetometers
DeLand, Zachary
Description of experiments and results pertaining to the development of a 4x2 channel atomic magnetometer array for use in detection of fetal magnetocardiography signals.
PhD Thesis, 2017
2017-12-01T00:00:00ZDownstream hydrogen plasma cleaning for mass metrology at NIST
http://digital.library.wisc.edu/1793/78501
Downstream hydrogen plasma cleaning for mass metrology at NIST
Benck, Eric
On International Metrology Day, May 20, 2019, the redefinition of the International System of Units (SI) is scheduled to be implemented. When this occurs the kilogram, the last remaining unit defined by a physical artifact, will be redefined to be based on a fundamental physical constant, the Planck constant. As a consequence, the NIST mise en pratique, a series of steps for the realization and dissemination of the revised definition of the kilogram, must be significantly modified. In particular, the mise en pratique will need to address for the first time the measurement and handling of masses in a vacuum. At NIST this will includes 5 major components: NIST-4 Kibble Balance, Magnetic Suspension Mass Comparator (MSMC), Mass-in-Vacuum Comparator, storage chambers, and mass transport vehicles (MTV). In addition to these components, there also is a need to develop new procedures to maintain and clean masses in vacuum. Over long periods of time masses can become coated with a carbon containing contamination layer, even while stored in a vacuum. A downstream hydrogen plasma source is being investigated as a means of gently removing these carbonaceous layers. Atomic hydrogen can react with carbon on the mass surface and convert it to volatile hydrocarbons which can then be pumped out of the system. Initial results demonstrating the etching of carbon coatings off a quartz crystal microbalance (QCM) in our downstream hydrogen plasma cleaner will be presented.
2018-06-01T01:19:56ZMeasurements of branching fractions using Fourier transform and grating spectroscopy
http://digital.library.wisc.edu/1793/78313
Measurements of branching fractions using Fourier transform and grating spectroscopy
Nave, Gillian
The measurement of lifetimes using laser-induced fluorescence at the University of Wisconsin-Madison has been one of the most productive experiments in the measurement of atomic spectroscopic data. The NIST bibliographic database on Atomic Transition Probabilities lists over 60 papers with Jim Lawler as an author or coauthor on lifetimes of neutral and singly-ionized elements ranging from carbon to mercury. The applications of these measurements range from astrophysics to lighting research. However, it is necessary to combine these lifetimes with branching fractions in order to obtain the atomic transition probabilities, and these branching fractions are now frequently the limiting factor in the accuracy of the measurements. I shall describe how the combination of measurements of branching fractions using Fourier transform spectroscopy at NIST with those of weak lines using the UW echelle spectrograph can improve the reliability of these measurements and provide the atomic data for weak lines that are challenging to measure using Fourier transform spectroscopy alone.
2018-04-30T14:14:47ZHigh energy density plasma simulations using ultracold neutral plasmas
http://digital.library.wisc.edu/1793/78309
High energy density plasma simulations using ultracold neutral plasmas
Bergeson, Scott
Strongly-coupled Coulomb systems are typically fluid-like plasmas characterized by the ratio of the nearest-neighbor electrical potential energy to the average kinetic energy. When this ratio is near unity, the plasmas are non-ideal and the foundational assumptions of plasma physics are no longer valid. Astronomical examples include the crusts of white dwarf stars, the interior of Jovian planets, and the dust belts of Saturn. Laboratory examples include laser-driven compression shocks, exploding wires, inertially confined plasmas, and, surprisingly, photo-ionized laser-cooled atoms. Transport properties in these widely disparate plasmas scale with the ratio of potential-to-kinetic energy (the Coulomb coupling parameter). Even systems that are widely disparate in temperature and density can be thermodynamically similar if this ratio is the same. I'll talk about our work in photo-ionized laser-cooled atoms, presenting progress in thermalization, transport, and equilibration.
2018-04-27T18:21:55Z