Physics Commons^™

Discovering New Strong Gravitational Lenses In The Desi Legacy Imaging Surveys, Xiaosheng Huang, Christopher Storfer, A. Gu, V. Ravi, A. Pilon, W. Sheu, R. Venguswamy, S. Bankda, A. Dey, M. Landriau, D. Lang, A. Meisner, J. Moustakas, A. D. Myers, R. Sajith, E. F. Schlafly, D. J. Schlegel

Physics and Astronomy

We have conducted a search for new strong gravitational lensing systems in the Dark Energy Spectroscopic Instrument Legacy Imaging Surveys’ Data Release 8. We use deep residual neural networks, building on previous work presented in Huang et al. (2020). These surveys together cover approximately one third of the sky visible from the northern hemisphere, reaching a z-band AB magnitude of ∼ 22.5. We compile a training sample that consists of known lensing systems as well as non-lenses in the Legacy Surveys and the Dark Energy Survey. After applying our trained neural networks to the survey data, we visually inspect and …

Characterizing Plasma With Emission Tomography-Feasibility Study On Synthetic And Experimental Data, M. Nikolić, A. Samolov, A. Godunov, L. Vušković,, S. Popović

Physics Faculty Publications

We present a feasibility study on different tomographic algorithms to overcome the issues of finite sets of projection data, limited viewing angles, and noisy data, which cause the tomographic reconstruction to be an ill-posed inversion problem. We investigated three approaches: single angle Abel inversion, two angle approach, and multiple angle 2D plasma tomography. These methods were tested on symmetric and asymmetric sample functions and on experimental results from a supersonic flowing argon microwave plasma sustained in a cylindrical quartz cavity. The analysis focused on the afterglow region of the microwave flow where a plasmoid-like formation was observed. We investigated the …

Design And Construction Of A Computer Controlled Astronomical Spectropolarimeter, Jacob Marchio

Honors College

A theoretical description of a simple optical train, modulated signal based spectropolarimeter is discussed. The design includes, after the telescope optical tube (in this case, a 9.25” Schmidt Cassegrain), a rotating quarter waveplate (compensator), a fixed linear polarizer (analyzer), and transmission grating of 100l/mm, with a ZWO ASI290mm astronomical camera. The practical constraints on implementing such an instrument are discussed, and the construction of the spectropolarimeter is detailed, including the necessary optics, optomechanics, and electromechanics. The rotation and recording of the rotating compensator is facilitated by a motorized connection with proportional feedback control, and the uncertainty in measuring the angle …

Kondo Signatures Of A Quantum Magnetic Impurity In Topological Superconductors, Rui Wang, Wei-Yi Su, Jian-Xin Zhu, Chin-Sen Ting, Hai Li, Changfeng Chen, Baigeng Wang, Xiaoqun Wang

Physics & Astronomy Faculty Research

We study the Kondo physics of a quantum magnetic impurity in two-dimensional topological superconductors (TSCs), either intrinsic or induced on the surface of a bulk topological insulator, using a numerical renormalization group technique. We show that, despite sharing the p+ip pairing symmetry, intrinsic and extrinsic TSCs host different physical processes that produce distinct Kondo signatures. Extrinsic TSCs harbor an unusual screening mechanism involving both electron and orbital degrees of freedom that produces rich and prominent Kondo phenomena, especially an intriguing pseudospin Kondo singlet state in the superconducting gap and a spatially anisotropic spin correlation. In sharp contrast, intrinsic TSCs support …

Graphene Used As A Lateral Force Microscopy Calibration Material In The Low-Load Non-Linear Regime, Mathias J. Boland, Jacob L. Hempel, Armin Ansary, Mohsen Nasseri, Douglas R. Strachan

Physics and Astronomy Faculty Publications

A lateral force microscopy (LFM) calibration technique utilizing a random low-profile surface is proposed that is successfully employed in the low-load non-linear frictional regime using a single layer of graphene on a supporting oxide substrate. This calibration at low loads and on low friction surfaces like graphene has the benefit of helping to limit the wear of the LFM tip during the calibration procedure. Moreover, the low-profiles of the calibration surface characteristic of these layered 2D materials, on standard polished oxide substrates, result in a nearly constant frictional, adhesive, and elastic response as the tip slides over the surface, making …

An Apparatus For Studying Electrical Breakdown In Liquid Helium At 0.4 K And Testing Electrode Materials For The Neutron Electric Dipole Moment Experiment At The Spallation Neutron Source, T. M. Ito, J. C. Ramsey, W. Yao, D. H. Beck, V. Cianciolo, S. M. Clayton, Christopher B. Crawford, S. A. Currie, B. W. Filippone, W. C. Griffith, M. Makela, R. Schmid, G. M. Seidel, Z. Tang, D. Wagner, W. Wei, S. E. Williamson

Physics and Astronomy Faculty Publications

We have constructed an apparatus to study DC electrical breakdown in liquid helium at temperatures as low as 0.4 K and at pressures between the saturated vapor pressure and ∼600 Torr. The apparatus can house a set of electrodes that are 12 cm in diameter with a gap of 1–2 cm between them, and a potential up to ±50 kV can be applied to each electrode. Initial results demonstrated that it is possible to apply fields exceeding 100 kV/cm in a 1 cm gap between two electropolished stainless steel electrodes 12 cm in diameter for a wide range of pressures …

Design And Fabrication Of Liquid Scintillator Counter, Andrea Calderon Saucedo, John L. Orrell

STAR Program Research Presentations

Pacific Northwest National Laboratory (PNNL) is currently developing an ultra-low background liquid scintillator counter (ULB LSC) in the shallow underground laboratory. At a depth of 35-meters water-equivalent, the underground laboratory has a multi-layered shielding to keep out cosmic-ray induced background. The ULB LSC, which is located in a clean room facility, is a multi-layered design made up of various materials, including plastic scintillator veto panels, borated polyethylene, lead and copper. These layers help lower the contributions of the terrestrial background and intrinsic background, resulting from the impurities present in the materials, to the overall background count rate observed by the …

Gps Phase Scintillation At High Latitudes During Geomagnetic Storms Of 7–17 March 2012 – Part 1: The North American Sector, P. Prikryl, R. Ghoddousi-Fard, E. G. Thomas, J. M. Ruohoniemi, S. G. Shepherd

Dartmouth Scholarship

During the ascending phase of solar cycle 24, a series of interplanetary coronal mass ejections (ICMEs) in the period 7–17 March 2012 caused geomagnetic storms that strongly affected high-latitude ionosphere in the Northern and Southern Hemisphere. GPS phase scintillation was observed at northern and southern high latitudes by arrays of GPS ionospheric scintillation and TEC monitors (GISTMs) and geodetic-quality GPS receivers sampling at 1 Hz. Mapped as a function of magnetic latitude and magnetic local time, regions of enhanced scintillation are identified in the context of coupling processes between the solar wind and the magnetosphere–ionosphere system. Large southward IMF and …

Dual-Spacecraft Reconstruction Of A Three-Dimensional Magnetic Flux Rope At The Earth's Magnetopause, H. Hasegawa, B. U. Ö. Sonnerup, S. Eriksson, T. K. M. Nakamura

Dartmouth Scholarship

We present the first results of a data analysis method, developed by Sonnerup and Hasegawa (2011), for reconstructing three-dimensional (3-D), magnetohydrostatic structures from data taken as two closely spaced satellites traverse the structures. The method is applied to a magnetic flux transfer event (FTE), which was encountered on 27 June 2007 by at least three (TH-C, TH-D, and TH-E) of the five THEMIS probes near the subsolar magnetopause. The FTE was sandwiched between two oppositely directed reconnection jets under a southward interplanetary magnetic field condition, consistent with its generation by multiple X-line reconnection. The recovered 3-D field indicates that a …

Instrument For Precision Long-Term Ss-Decay Rate Measurements, M. J. Ware, Scott D. Bergeson, J. E. Ellsworth, M. Groesbeck, J. E. Hansen, D. Pace, J. Peatross

Faculty Publications

We describe an experimental setup for making precision measurements of relative ß-decay rates of ²²Na, ³⁶Cl, ⁵⁴Mn, ⁶⁰Co, ⁹⁰Sr, ¹³³Ba, ¹³⁷Cs, ¹⁵²Eu, and ¹⁵⁴Eu. The radioactive samples are mounted in two automated sample changers that sequentially position the samples with high spatial precision in front of sets of detectors. The set of detectors for one sample changer consists of four Geiger-Müller (GM) tubes and the other set of detectors consists of two NaI scintillators. The statistical uncertainty in the count rate is few times 0.01% per day for the GM …

The Optical Luminosity Function Of Gamma-Ray Bursts Deduced From Rotse-Iii Observations, X. H. Cui, X. F. Wu, J. J. Wei, F. Yuan, W. K. Zheng, E. W. Liang, C. W. Akerlof, M. C. B. Ashley, H A. Flewelling, E. Göǧüş, T. Güver, Ü. Kızıloǧlu, T. A. Mckay, S. B. Pandey, E. S. Rykoff, W. Rujopakarn, B. E. Schaefer, J. C. Wheeler, Sarah A. Yost

Physics Faculty Publications

We present the optical luminosity function (LF) of gamma-ray bursts (GRBs) estimated from a uniform sample of 58 GRBs from observations with the Robotic Optical Transient Search Experiment III (ROTSE-III). Our GRB sample is divided into two sub-samples: detected afterglows (18 GRBs) and those with upper limits (40 GRBs). We derive R-band fluxes for these two sub-samples 100 s after the onset of the burst. The optical LFs at 100 s are fitted by assuming that the co-moving GRB rate traces the star formation rate. While fitting the optical LFs using Monte Carlo simulations, we take into account the …

Laser Frequency Stabilization For Lisa, Andrew B. Parker, Andrew J. Sutton, Glenn De Vine

STAR Program Research Presentations

This research focuses on laser ranging developments for LISA (Laser Interferometer Space Antenna), a planned NASA-ESA gravitational wave detector in space. LISA will utilize precision laser interferometry to track the changes in separation between three satellites orbiting 5 million kilometers apart. Specifically, our goal is to investigate options for laser frequency stabilization. Previous research has shown that an optical cavity system can meet LISA's stability requirements, but these units are large and heavy, adding cost to the implementation. A heterodyne Mach-Zehnder interferometer could be integrated onto LISA’s existing optical bench, greatly reducing the weight, provided the interferometer meets the stability …

Environmental Testing Of Lasers For Jpl's Cold Atom Laboratory, Carey L. Baxter

STAR Program Research Presentations

NASA’s Cold Atom Lab (CAL) is a multi-user facility designed to study ultra-cold quantum gases in the microgravity environment of the International Space Station (ISS). One of the main goals of CAL is to explore the unknown territory of extremely low temperatures—possibly as low as the picokelvin range!—where new and fascinating quantum phenomena can be observed. At such temperatures matter stops behaving as particles and instead becomes macroscopic matter waves. CAL will be remotely controlled to perform a multitude of experiments and is scheduled to launch in 2016. In order to anticipate problems that might occur during and post-launch, including …

Maximizing Precision Of Variable Star Photometry With Digital Cameras In Suburban Environments, David Hergesheimer

STAR Program Research Presentations

Photometry is the measure of the brightness of an object. When making such measurements on stars, it is done is units of magnitude, which is on a logarithmic scale with a base of ~2.512. Variable star photometry using a commercially available digital camera is not going to be as accurate and precise as equipment used by astronomers, and because of the logarithmic scale of magnitude used, determining how much of an effect different error reduction strategies have is not straightforward, and is best done experimentally.

My research is conducting photometry on variable stars (changing brightness) with a digital camera, and …

Characterization Of Samples For Optimization Of Infrared Stray Light Coatings, Carey L. Baxter, Rebecca Salvemini, Zaheer A. Ali, Patrick Waddell, Greg Perryman, Bob Thompson

STAR Program Research Presentations

NASA’s Stratospheric Observatory for Infrared Astronomy (SOFIA) is a converted 747SP that houses a 2.5 m telescope that observes the sky through an opening in the side of the aircraft. Because it flies at altitudes up to 45,000 feet, SOFIA gets 99.99% transmission in the infrared. Multiple science instruments mount one at a time on the telescope to interpret infrared and visible light from target sources. Ball Infrared Black (BIRB) currently coats everything that the optics sees inside the telescope assembly (TA) cavity in order to eliminate noise from the glow of background sky, aircraft exhaust, and other sources. A …

Flitecam Data Process Validation, Jesse K. Tsai, Sachindev S. Shenoy, Brent Cedric Nicklas, Zaheer Ali, William T. Reach

STAR Program Research Presentations

FLITECAM Data Processing Validation

Many of the challenges that come from working with astronomical imaging arise from the reduction of raw data into scientifically meaningful data. First Light Infrared Test CAMera (FLITECAM) is an infrared camera operating in the 1.0–5.5 μm waveband on board SOFIA (Stratospheric Observatory For Infrared Astronomy). Due to the significant noise from the atmosphere and the camera itself, astronomers have developed many methods to reduce the effects of atmospheric and instrumental emission. The FLITECAM Data Reduction Program (FDRP) is a program, developed at SOFIA Science Center, subtracts darks, removes flats, and dithers images.

This project contains …

Discontinuities And Alfvenic Fluctuations In The Solar Wind, G. Paschmann, S. Haaland, B. Sonnerup, T. Knetter

Dartmouth Scholarship

We examine the Alfvenicity of a set of 188 solar wind directional discontinuities (DDs) identified in the Cluster data from 2003 by Knetter (2005), with the objective of separating rotational discontinuities (RDs) from tangential ones (TDs). The DDs occurred over the full range of solar wind velocities and magnetic shear angles. By performing the Walen test in the de Hoffmann–Teller (HT) frame, we show that 77 of the 127 crossings for which a good HT frame was found had plasma flow speeds exceeding 80 % of the Alfven speed at an average angular deviation of 7.7◦; 33 cases had speeds …

Telescope Assembly Alignment Simulator Performance Optimization, Joshua G. Thompson, Brian Eney, Zaheer Ali, Bob Thompson

STAR Program Research Presentations

The Telescope Assembly Alignment Simulator (TAAS) calibrates scientific instruments (SI’s) that are installed on the Stratospheric Observatory For Infrared Astronomy (SOFIA). An SI’s accuracy is directly dependent on the consistent performance of the TAAS, which has never been fully characterized. After designing various thermal and optical experiments to identify the current unknowns of TAAS, we now have a far better grasp on how the equipment behaves.

Comment On "Generation Of Cold Low Divergent Atomic Beam Of Indium By Laser Ablation", A. Denning, A. Booth, S. Lee, M. Amonson, Scott D. Bergeson

Faculty Publications

We present measurements of the velocity distribution of calcium atoms in an atomic beam generated using a dual-stage laser back-ablation apparatus. Distributions are measured using a velocity selective Doppler time-of-flight technique. They are Boltzmann-like with rms velocities corresponding to temperatures above the melting point for calcium. Contrary to a recent report in the literature, this method does not generate a subthermal atomic beam.

The Cosmic Ray Observatory Project: A Statewide Outreach And Education Ex-Periment In Nebraska, Daniel Claes, Gregory Snow

Gregory Snow Publications

Abstract: The Cosmic Ray Observatory Project (CROP) is a statewide education and research ex-periment involving Nebraska high school students, teachers and university undergraduates in the study of extensive cosmic-ray air showers. A network of high school teams construct, install, and op-erate school-based detectors in coordination with University of Nebraska physics professors and graduate students. The detector system at each school is an array of scintillation counters recycled from the Chicago Air Shower Array in weather-proof enclosures on the school roof, with a GPS re-ceiver providing a time stamp for cosmic-ray events. The detectors are connected to triggering elec-tronics and a …

Temperature Dependence Of Stark Width Of The 463.054 Nm Nii Spectral Line, Vladimir Milosavljevic, Ruzica Konjevic, Stevan Djenize

Articles

Stark width of the 463.054 nm singly ionized nitrogen spectral line, that belong to transition, have been measured in a linear pulsed, low pressure, arc discharge. The working gas was helium-nitrogen-oxygen mixture. Electron densities of 0.7510²³ to 1.4510²³ were determined in the electron temperature range between 30000 K - 38000 K. The measured values have been compared with our calculated data, using the modified semiempirical approximation. On the basis of the agreement among experimental and theoretical Stark width data, the isolated 463.054 nm NII spectral line can be recommended as convenient spectral line for plasma diagnostics.

Aliasing Reduction In Staring Infrared Imagers Utilizing Subpixel Techniques, Joseph C. Gillette, Thomas M. Stadtmiller, Russell C. Hardie

Electrical and Computer Engineering Faculty Publications

We introduce and analyze techniques for the reduction of aliased signal energy in a staring infrared imaging system. A standard staring system uses a fixed two-dimensional detector array that corresponds to a fixed spatial sampling frequency determined by the detector pitch or spacing. Aliasing will occur when sampling a scene containing spatial frequencies exceeding half the sampling frequency. This aliasing can significantly degrade the image quality. The aliasing reduction schemes presented here, referred to as microscanning, exploit subpixel shifts between time frames of an image sequence. These multiple images are used to reconstruct a single frame with reduced aliasing. If …