Session E1: Contributed Papers - APS I

Formula recollection through a WORLDLY recognized mnemonic technique

Physics may be made fun, and encourage further learning through ease of recollection of complicated formulas; allthewhile increasing a student's confortability with their algebraic skills. Examples will be shown how ANY complicated formula will be made into a memorable acronym using this author's mnemonic technique, i.e. allowing each vowel to represent a mathematical operation: ``a'' multiplication implying ``@''; ``o''-division implying ``over''; ``i''-subtraction to imply ``minus''; ``u''-addition to imply ``plus''; and ``e'' implying ``equals''. Most constants and variables are indeed consonants; ``c'' = ``speed of light'' \& ``z'' = ``altitude''. With this mnemonic technique ANY formula may be algebraically manipulated into a word, or series of words for ease of recollection. Additional letters may be added to enhance the intelligibility of such a letter combination, but these additional letters need be consonants ONLY. This mnemonic technique was developed as a compensatory memory method when taking physics at Texas A\&M University following a severe head injury (19 days unconsciousness!) suffered by this author.   

Voltage Tunable, Plasmon Meditated Detection of THz Radiation

Resonant excitation of plasmons in the two dimensional electron gas, (2DEG), of a high electron mobility transistor provides a means to detect THz radiation. Because the allowed resonance is strongly dependant on the sheet charge concentration of the 2DEG, an external bias can be used to control the wavelength detected. This class of frequency agile THz detector is expected to find use in ``spectrometer on a chip'' applications where a simple voltage ramp can be used to alter the device response by over a 1 THz bandwidth. Because of its microelectronic type size and weight, as well as the potential for array fabrication, the device is believed suitable for satellite based THz imaging applications. Recent theoretical and experimental progress on the development of such a device will be discussed.   

Design and Calibration of a High-Precision Density Gauge for Firn and Ice Cores

The Maine Automated Density Gauge Experiment (MADGE) is a field deployable gamma-ray density gauging instrument designed to provide high resolution (3.3 mm) and high precision ($\pm 0.004$ g cm$^{-3}$) density profiles of polar firn and ice cores at a typical throughput of 1.5 m h$^{-1}$. The resulting density profiles are important in ice sheet mass balance and paleoclimate studies, as well as the modeling electromagnetic wave propagation in firn and ice for remote sensing and ground penetrating radar applications. This study describes the design (optimal gamma-ray energy selection, measurement uncertainty analysis, dead-time corrections) and calibration (mass-attenuation coefficient and absolute density calibrations) of the instrument, and discusses the results of additional experiments to verify the calculated measurement uncertainty. Data collected from firn cores drilled on the recent 2006-2007 U.S. Internation Trans-Antarctic Scientific Expedition are also shown and discussed.   

Thiophene based Conjugated Polymers for Organic Solar Cells

Renewable energy resources are becoming increasingly important in view of pressure on petroleum resources and concerns about global warming. One of the alternate green sources of energy is solar energy. Conjugated polymers, which are an important class of materials, are extensively used for the fabrication of solar cells. Here, we report the optical properties of some thiophene based conjugated polymers in solid film. The photoluminescence of these thiophene copolymers are completely quenched when blended with Phenyl C61 Butyric Acid Methyl Ester (PCBM) (1:1 wt ratio) indicating the probability of charge transfer from conjugated polymers to PCBM. It unveils the possibility of using these copolymers as one of the components of the active layer in bulk heterojunction solar cells. In another efforts, using Poly[(9,9-dioctylfluorenyl-2,7-diyl)-co-(bithiophene)] as a dye in dye sensitized titania cells, an open circuit voltage of 0.64V, a short circuit current of 0.36 mA/cm$^{2}$ with an overall power conversion efficiency of 0.12{\%} is achieved.   

Spacecraft charging in sunlight: new evidence of monopole-dipole potential distribution

We present the results of a statistical study on high-level charging of spacecraft in sunlight at geosynchronous altitudes. Below the critical temperature of the ambient plasma, no spacecraft charging occurs in eclipse. A spacecraft has a shadowed side in sunlight. The critical temperature remains the same and the ratio of the surface potential in sunlight to that in eclipse is about 1/3, agreeing with the monopole-dipole model.   

Solar Energetic Particle Events with High Iron Charge State at Low SEP Energies

The ionic charge states of Solar Energetic Particle (SEP) events provide direct information about the environment of the source plasma. Gradual events show consistent Q$_{Fe}$ of $\sim $10 reflecting typical corona temperature, while impulsive events show a sharp increase of Q$_{Fe}$ with energy, indicating energy dependent stripping. Both types of events have similar Q$_{Fe}$ at E$<$0.1 Mev/nuc, indicating a similar source temperature of 1-3 MK. However, Q$_{Fe}>$16 is frequently found in the solar wind, particularly coming from active regions, suggesting high Q in source populations, while so far only low Q$_{Fe}$ was observed at low SEP energies. Therefore, we performed a survey of iron charge states of all SEP events observed with ACE SEPICA during 1998 -- 2000, complemented by ACE SWICS and SOHO STOF. We found a set of 6 events with Q$_{Fe}>$14 over the entire SEPICA energy range. The observation of high iron charge states at low SEP energies points to a source temperature of 2-6 MK. However, these events are rather rare, indicating that additional conditions must be met to accelerate high Q source populations.   

The Fast Neutron Imaging Telescope (FNIT) for Detection of Illicit Nuclear Materials

We report on the characterization, modeling, and algorithm development for FNIT -- a Fast Neutron Imaging Telescope. Initially designed to measure solar neutrons in the inner heliosphere, it was later tailored to detect and measure clandestine special nuclear material (SNM) with unique spectral and directional information. To make such measurements, a double scatter telescope is needed. Laboratory testing with a FNIT prototype has been performed in order to characterize such instrumental parameters as time-of-flight, spatial, energy and angular resolutions. Extensive GEANT4 modeling has been performed in an effort to fully characterize the instrument response. These simulations, along with the tests performed with a strong Cf-252 fission neutron source, will allow us to develop efficient, on-line spectral de-convolution and imaging algorithms for a scaled-up, field ready portable neutron telescope. We will present the most recent analysis results.   

Bio-habitability Indicators on Polar Mars found by the 2007 Phoenix Mars Scout Mission

The Phoenix Mars Scout landed on 25 May 2008 at the northern polar latitude of 68N and longitude 234E (areocentric). Analyses included excavating the Mars regolith with a robotic arm and delivering samples to payload instruments including a scanning calorimeter-mass spectrometer (TEGA) and an electrochemical analyzer, (WCL). This exciting mission has been used to inspire many students from junior high through graduate school. The instruments on board are often utilizing very basic physical and chemical properties to make small discoveries that feed into very large questions. Students can have some of the excitement of arriving at answers themselves or discovering how their lessons connect directly to some of NASA's largest initiatives. The work reported here addresses the implications of the Phoenix observations for the prospects of Mars biohability. TEGA confirmed the presence of water ice in the regolith, not bound as a chemical ligand. The salts by WCL offer evidence for the past presence of liquid water on Mars. Sources of bio-energy, key bio-elements and ions, and environmental toxicity and pH will also be discussed.