Physics Commons^™

High Altitude Dependence Of Ionizing Radiation From Cosmic Rays, Zack Gibson, Akihiro Nagata, Midori Morikawa, Takuyuki Sakai, Takahiro Shimizu, Yuta Takahashi, Shusuke Okita, Raul Ramirez, Alexandra Hughlett, Toshihiro Kameda, Jr Dennison

Posters

The flux of ionizing radiation from cosmic background sources has been measured as a function of altitude using a compact Geiger counter aboard a high altitude balloon. The payload was developed by researchers from University of Tsukuba and flown under the auspices of the Utah State Get-Away-Special (GAS) team. Dose rate, temperature, pressure, humidity, altitude and position data were acquired during a ~4 hour flight up to an altitude of 32 km in August 2016. The altitude reached by this balloon was more than 5 times the height of that reached by Victor Hess’ experiment in 1912, which later won …

Relaxation Of Radiation Effects On The Optical Transmission Of Polymers, Alexandra Hughlett, Tyler Kippen, J. R. Dennison

Posters

Changes in optical transmission of polymers over time were studied to determine the factors contributing to relaxation of defect states induced by intense radiation doses. Samples of low density polyethylene (LDPE), polyether ether ketone (PEEK), polypropylene (PP), and polyimide (PI) received doses up to 500 MGy from an 8 MeV electron accelerator. These doses were intended to simulate long-term exposure of common spacecraft materials in geosynchronous orbit. Features and absorption edges in ~250 nm to 1000 nm UV to IR transmission spectra can be related to energies associated with various defects previously observed in these highly disordered materials. Recent work …

Temperature Dependency Of Electrostatic Breakdown In Ldpe And Peek, Tyler Kippen, Allen Andersen, Jr Dennison

Posters

Electrostatic breakdown is a leading cause of many of the anomalies and failures attributed to spacecraft interactions with the space environment. It is therefore critical to understand how the electrostatic field strength varies due to changing environmental conditions, including temperature and radiation dose. Standard step-up to electrostatic discharge (ESD) tests were performed on two polymers, low density polyethylene (LDPE) and polyetheretherketone (PEEK). Tests were done at room temperature and at other temperatures ranging from ~130 K to ~350 K. Preliminary analysis found that samples tested at a higher temperature had lower average breakdown field strength and a narrower distribution of …

Predictive Formula For Electron Penetration Depth Of Diverse Materials Over Large Energy Ranges, Anne C. Starley, Gregory Wilson, Lisa Phillipps, Jr Dennison

Posters

No abstract provided.

Dependence Of Electrostatic Field Strength On Voltage Ramp Rate For Spacecraft Materials, Krysta Moser, Allen Andersen, Jr Dennison

Posters

No abstract provided.

Cubesat Space Environments Effects Studied In The Space Survivability Test Chamber, Jr Dennison, Gregory Wilson, Alex Souvall, Ben Russon, Katie Gamaunt

Posters

CubeSats are particularly susceptible to environmental-induced modifications, which can lead to deleterious or catastrophic consequences. This is increasingly important as small satellites—with minimal shielding due to reduced mass and size constraints and reliance on more compact and sensitive electronics—have longer mission lifetimes and make more diverse, complex and sensitive measurements. The current push to expand deployment of CubeSats beyond LEO, into even more demanding environments where modest relief due to shielding by the Earth’s magnetosphere is absent (such as polar or GEO orbits), can further exacerbate these problems.

Testing of small satellites is therefore critical to avoid such problems. A …

Simultaneous, Collocated Rayleigh And Sodium Lidar Temperature Comparison, Leda Sox, Vincent B. Wickwar, Tao Yuan, Neal Criddle

Posters

There are relatively few instruments that have the capabilities to make near continuous measurements of the mesosphere-lower-thermosphere (MLT) region. Rayleigh-scatter (RS) and resonance lidars, particularly sodium (Na) resonance lidar, have been the two dominant ground-based techniques for acquiring mesosphere and MLT vertical temperature profiles, respectively, for more than two decades. With these measurements, the dynamics and long-term temperature trends of the MLT region can be studied. For the first time, we will present simultaneous, night-time averaged temperatures acquired from the same observational site, on the campus of Utah State University (USU), using these two lidar techniques. This comparison is also …

Obtaining Continuous Observations From The Upper Stratosphere To The Lower Thermosphere Using The Alo-Usu Rayleigh-Scatter Lidar., Jonathan L. Price, Vincent B. Wickwar, Leda Sox, Matthew T. Emerick, Joshua P. Herron, Shayli Elliott, Bryant Ward, Benjamin Lovelady

Posters

The Rayleigh-scatter lidar at the Atmospheric Lidar Observatory at Utah State University (ALO-USU; 41.74° N, 111.81° W) started observations in 1993. In 2012 the original lidar system was upgraded with an array of larger mirrors and two lasers to enable observations of the upper mesosphere and lower thermosphere from 70 km to about 115 km in altitude. (Continued refinement should provide data to above 120 km.) Recently, the original system was reconfigured [Elliott et al., 2016] to again observe the lower mesosphere between 40 km and 90 km. Initial data collected by these two parts of the Rayleigh system have …

Seasonal Temperatures From The Upper Mesosphere To The Lower Thermosphere Obtained With The Large, Alo-Usu, Rayleigh Lidar, Vincent B. Wickwar, Leda Sox, Matthew T. Emerick, Joshua P. Herron

Posters

Observations have been made with the large, Rayleigh-scatter lidar at the Atmospheric Lidar Observatory at Utah State University (ALO-USU; 41.74° N, 111.81° W) from summer 2014 to summer 2015. During this first operational year, the lidar acquired nearly 100 nights of observations between 70 and 115 km altitude, i.e., from the upper mesosphere, through the mesopause, and into the lower thermosphere. This was possible because of the large 4.9 m2 collecting area of the mirrors and the 42 W of 532 nm emission at 30 Hz. These two factors produce a figure of merit, the power-aperture-product, of 206 Wm2, making …

Reestablishing Observations Throughout The Mesosphere With The Alo-Usu Rayleigh-Scatter Lidar, Shayli Elliott, Bryant Ward, Benjamin Lovelady, Jessica Gardiner, Lucas Priskos, Matthew T. Emerick, Vincent B. Wickwar

Posters

In the last few years, the Rayleigh-scatter lidar at the Atmospheric Lidar Observatory at Utah State University (ALO-USU; 41.74° N, 111.81° W) has been upgraded to extend observations from 70 km up to 115 km. This project describes a student project to build and use a complementary Rayleigh-scatter lidar to go from 40 to 90 km, from the upper stratosphere to the upper mesosphere. At the upper end, this new lidar overlaps with the high-altitude lidar. This was done in a period of just over two months. This lidar shares the same lasers, but introduces a 44-cm mirror and a …

Searching For Troposphere-Mesosphere Connections Using The Alo-Usu Rayleigh-Scatter Lidar, David K. Moser, Vincent B. Wickwar, Joshua P. Herron

Posters

The paucity of whole-atmosphere data introduces significant challenges that hinder the study of atmospheric couplings. The mesosphere in particular is a low-information void between the lower and upper atmosphere, which may prevent us from a complete realization of vertical interactions. The Rayleighscatter lidar at Utah State University’s Atmospheric Lidar Observatory (ALO-USU; 41.74° N, 111.81° W), operated with little interruption from 1993 to 2004, providing a valuable temporal and spatial (45 – 90 km) resource in this realm. When studied alongside a multitude of other atmospheric data sources, possible unforeseen connections or insights may result. In this study, an adaptive fit …

Uv Degradation Effects: Terrestrial Versus Space Environment, Katie Gamaunt, Krysta Moser, Alex Souvall, Jr Dennison

Posters

The decrease in visible and ultraviolet transmission spectra of polymeric and glass spacecraft materials has been measured to determine the extent of degradation due to high energy UV radiation similar to the solar spectrum (both above and below the stratosphere). This project looked at the effects that the atmosphere has in regards to blocking UV radiation and thus, slowing down the UV degradation process. Materials such as quartz, borosilicate glass, sodium glasses, polyethylene, polyimide, and polyethylene terephthalate polymers were exposed to radiation from a focused high intensity deuterium lamp source, which generates radiation in the UVA and UVB spectrum. Duplicates …

Perspectives On The Distributions Of Esd Breakdowns For Spacecraft Charging Applications, Allen Andersen, Krysta Moser, Jr Dennison

Posters

Electrostatic discharge (ESD) continues to pose significant risks to space missions despite decades of intense study. We emphasize here the advantages to spacecraft designers and modelers from considering the stochastic distributions of breakdown and how it can be affected by factors including spacecraft environment conditions, design geometries, material temperature, material purity, charging history, and appropriate timescales. Spacecraft charging models and spacecraft designs typically rely on tabulated values or ranges of breakdown strength, often based on cursory measurements with little or no experimental detail. Depending on the timescales and history of environmental and orbital changes or durations of specific missions, it …

Temporal And Spatial Correlations In Electron-Induced Arcs Of Adjacent Dielectric Islands, Justin Christensen, Jr Dennison, Justin Dekany

Posters

This study investigates very short duration (<1ms) flashes caused by rapid discharge arcs from charged insulating epoxy “glue dots” to an underlying grounded substrate. There were 36 separate ~3 mm diameter hemispherical bisphenol/amine epoxy “glue dots” positioned around the conducting polymeric/carbon nanocomposite substrate edge exposed simultaneously to nearly identical electron fluxes. Most arcs are found to be random events which occur when built up charge produces an electric field large enough for electrostatic breakdown to occur. The possibility that a given arc might stimulate arcs in adjacent “glue dots” was investigated through coincidence correlation analysis. The dependence of such correlations with “glue dot” separation was also studied.

The data for this project were collected at Marshall Space Flight Center. The epoxy “glue dot” samples were mounted inside a high vacuum (<10^-4 Pa) chamber on a Black Kapton substrate attached to a large grounded metal plate, cooled with liquid nitrogen to ~120 K. An electron gun was used to bombard the sample with electrons of a known energy (12 to 40 keV) and flux density (0.3 to 5 nA/cm²), similar to what would be seen in a typical space environment. Light emitted from the samples was monitored with …

Pea System Modeling And Signal Processing For Measurements Of Volume Charge Distributions In Thin Dielectric Films, Lee H. Pearson, Jr Dennison, Erick W. Griffiths, A. C. Pearson

Posters

This paper discusses an effort to develop advanced pulsed electroacoustic (PEA) measurement system capabilities that incorporate state-of-the-art hardware and improved signal processing and modeling to characterize embedded charge distributions in thin dielectric films. Objectives in developing this system include: (1) improved spatial resolution, while maintaining reasonable temporal resolution; (2) improved signal processing tools for increased signal/noise ratios; (3) integrated PEA modeling tools; and (4) integrated environmental controls. We emphasize system improvements required to achieve high spatial resolution for in vacuo measurements of thin dielectrics charged using electron beam injection, which are most applicable for spacecraft charging tests. PEA measurement systems …

Synergistic Models Of Electron Emission And Transport Measurements Of Disordered Sio2, Jr Dennison, Jodie Corbridge Gillespie, Allen Andersen, Amberly Evans Jensen, Gregory Wilson, Justin Dekany, Alec M. Sim, Ryan Hoffmann

Posters

A critical component in the prediction and mitigation of spacecraft charging issues is an accurate model of the charging, transport and electron emission properties of a broad array of materials used in the construction of spacecraft. The increased sensitivity, longer-duration missions, and ventures into more demanding environments only serve to heighten this need. One important way for the spacecraft charging community to address this issue is to expand the role of more fundamental materials physics. This includes the development of unifying theoretical models of the charge transport equations based on the creation, distribution, and occupancy of defect densities of states. …

Predictive Formula For Electron Range Over A Large Span Of Energies, Anne C. Starley, Gregory Wilson, Lisa Montierth Phillipps, Jr Dennison

Posters

An empirical model developed by the Materials Research Group that predicts the approximate electron penetration depth—or range—of some common materials has been extended to predict the range for a broad assortment of other materials. The electron range of a material is the maximum distance electrons can travel through a material, before losing all of their incident kinetic energy. The original model used the Continuous-Slow-Down-Approximation for energy deposition in a material to develop a composite analytical formula which estimated the range from 10 MeV with an uncertainty of v, which describes the effective number of valence electrons. N_V was empirically …

Dependence Of Electrostatic Field Strength On Voltage Ramp Rate For Spacecraft Materials, Krysta Moser, Allen Andersen, Jr Dennison

Posters

This work investigated the dependence of electrostatic field strength for spacecraft materials on voltage ramp rate, by applying an increasing electrostatic field until electrostatic breakdown (a permanent, catastrophic failure of a dielectric material) occurs. Enhanced understanding of prolonged exposure to high static electric fields (DC aging) of insulating materials based on expanded experimental studies is of critical to understand the physics of highly disordered insulating materials, as well as for applications in spacecraft charging, high voltage DC power transmission cables and switching, thin film dielectrics, and semiconductor devices and sensors. Electrostatic discharge (ESD) and the associated material breakdown at the …

Absolute Electron Emission Calibration: Round Robin Tests Of Au And Polyimide, Jr Dennison, Justin Christensen, Clint Thomson, Neal Nickles, Robert E. Davies, Mohamed Belhaj, Kazuhiro Toyoda, Arifur R. Khan, Kazutaka Kawasaki, Shunsuke Inoue, Isabel Montero, Maria E. Davila, Leandro Olano

Posters

Accurate determination of the absolute electron yields of conducting and insulating materials are essential for models of spacecraft charging and related processes involving charge accumulation and emission due to electron beams and plasmas. Apparatus using low-fluence pulsed electron beam sources and various methods to minimize charge accumulation have been developed at facilities around the world. This study presents a round robin comparison of such tests performed in CSIC at Instituto de Ciencia de Materiales de Madrid, LaSeine at Kyushu Institute of Technology, DESSE at ONEREA, and the Space Environment Effects Materials (SEEM) test facility at Utah State University. The primary …

Effects Of Voltage Ramp Rates On Electrostatic Field Strength In Highly Disordered Insulating Materials, Krysta Moser, Allen Andersen, Jr Dennison

Posters

At high enough electrostatic fields or after long exposure times, insulators can break down, causing large current flow through the material: this breakdown is called electrostatic discharge (ESD). ESD is a permanent, catastrophic failure of a dielectric material: what was an insulator is now essentially a conductor. Previous tests done by the USU Materials Physics Group (MPG) using our ESD custom vacuum chamber have found that, for the polymeric materials biaxially oriented polypropylene (BOPP), polyimide (PI), and low density polyethylene (LDPE), the electrostatic field strength at breakdown depends on the ramp rate of voltage applied across some materials, but possibly …

Developing A Safe Test System For High-Energy Electron Flux Environments Testing, Heather Tippets

Posters

In order to predict and mitigate adverse environmental effects prone to spacecraft in orbit about earth, a versatile pre-launch test capability for assessment and verification of small satellites, systems, and components was developed by Utah State University’s Materials Physics Group. To further diversify this project, a 100 mCi strontium-90 beta radiation source (0.5 MeV – 2.5 MeV) was exploited to simulate high energy electron flux characteristic of geostationary orbit. Various samples including in-the-loop hardware, spacecraft materials, optical components, and solar arrays will be irradiated to gain a better understanding how these materials and electronics break down in space environments. For …

Voltage Ramp-Rate Dependence Of Dc Breakdown In Polymeric Insulators: Physical Models Versus Data, Allen Andersen, Krysta Moser, Jr Dennison

Posters

Purpose/Aim

The standard handbook values for dielectric breakdown strength of necessity come from accelerated test methods. In some applications the breakdown voltage may vary significantly with voltage ramp rates; therefore, a theoretical model for the ramp-rate dependence of breakdown is needed to extrapolate from realistic tests to long-duration material service lifetimes.

Experimental/Modeling methods

Series of step-up to breakdown tests were performed for ramp rates from 0.5 to 500 V/s for biaxially-oriented polypropylene (BOPP), low density polyethylene (LDPE), and polyimide (PI) films. The data were fit with standard empirical methods, as well as two physics-based defect-driven models.

Results/discussion

Table 1 in …

The Space Survivability Test Chamber, Alex Souvall, Benjamin Russon, Brian Wood, Gregory Wilson, Jr Dennison

Posters

No abstract provided.