SHINE 2009: Adiabatic Modeling of Inner Source Pickup Ions
Inner source pickup ions have been treated very similarly to those from interstellar space, but the physics of the two regions differ significantly. The density of electrons close to the Sun, and consequently the rate of electron impact ionization, is many orders of magnitude greater than in the outer heliosphere (Figure 1). The velocity of the neutral source of the pickup ions has, in the solar wind frame, more than the expected -Vsw term (Figure 2). An azimuthal term perpendicular to the solar wind is caused by the Keplerian orbits of the dust grains from which the neutrals arise. In addition, many of these new ions should be picked up where the solar wind is sub-Alfvénic. The Alfvén wave velocity, orbital velocity, and dominant electron-impact ionization terms strongly affect predictions for pickup ion peak locations and densities. This poster describes the adiabatic expansion of inner source pickup ions based on a spherically symmetric Fokker-Planck equation.
SHINE09_final poster
EIPBN 2008: Design and Fabrication of a Particle-Transparent Ultraviolet Filter for Solar Wind Measurements
Upcoming in-situ measurements of ion and neutral populations very close to the Sun will be very valuable in modeling coronal heating and solar wind acceleration. The acquisition of such measurements is complicated by the difficulties inherent in inserting and operating sensors in near-solar orbits. Minimization of the mass, power consumption, and complexity of sensor components are required to make such missions possible. This poster addresses the design and fabrication of a new particle-transparent ultraviolet filter requiring no power or moving parts. The fabrication combines the standard processes of nanoimprinting, liftoff, and through-wafer deep-reactive ion etching of silicon-on-insulator wafers with a modified Bosch process grating etch with scalloping under 7nm. Addition of a thin conformal oxide coating to the grating walls can significantly enhance the photon absorption below 155 nm wavelength, vastly increasing the effectiveness of the filter.
EIPBN08_final poster
SHINE 2006: Neutrals near the Sun and the inner source pickup ions
There is a source of neutral particles near the Sun, resulting in so-called “inner source pickup ions.” Pickup ions from this inner source have to date been treated very similarly to those from interstellar space. In particular, the assumption has been made that they are effectively motionless when picked up, and thus in the solar wind frame have a velocity of -Vsw which then isotropizes into ring or hemispheric distributions. We suggest that there are other motions or effective motions of these neutral particles in the near-solar environment that need to be considered. Many, if not most, of the neutral particles arise from dust grains spiraling into the Sun in Keplerian orbits, and thus these neutrals have a large azimuthal velocity perpendicular to the solar wind and the average heliospheric magnetic field. In addition, many of these ions should be picked up where the solar wind is sub-Alfvénic. As such, the Alfvén wave velocity needs to be taken into account when finding the effective frame in which ions are picked up, and their thermal velocity should isotropize around a value dependent upon major speed contributions. This value, much larger than that of the currently accepted stationary pickup, strongly affects the cooling of pickup ions in the inner heliosphere, and hence the interpretation of inner source pickup ion measurements done to date.

SHINE06_final poster
SHINE 2005: A New Instrument for Measuring the Near-Solar Neutral Atom Population
Neutral-atom physics in the heliosphere is still a relatively unexplored topic since we lack adequate in-situ data with which to form theories. In particular, the formation of pick-up ions in near-solar regions depends on significant neutral populations that we so far have not detected except through optical means. Unfortunately, current neutral atom detectors are generally large and heavy. Microelectromechanical systems (MEMS) technologies allow for the creation of detectors of similar or greater sensitivity for far smaller mass, volume, and energy costs, ideal for spacecraft with tightly constrained design budgets. We present here a Coke-can sized neutral-atom instrument design for Solar Probe that uses MEMS devices massing only a few grams.
SHINE05_final poster
SHINE 2004: Energetic Photon Filtration via Laser Etched Conductive Gratings
Ionizing radiation can cause significant false data points in a myriad of space-based sensors. In particular, the Hydrogen Lyman-alpha band at 121.6 nanometers creates false counts in microchannel plates, solid state detectors, and other sensors intended to monitor solar wind particle densities and properties. Current sensors use bulky geometric means to filter the photons out of the charged particle stream, but freestanding conductive gratings have been demonstrated to serve the same function with far smaller mass and volume. This poster focuses around a new means of creating these fine-grain gratings using a femtosecond laser etch.
SHINE04_final poster
Mentoring Across Educational Levels through the EECS 425 Capstone Class
The WIMS ERC seeks to open the technology pipeline from research institutions to high schools. A substantial part of that effort is a mentoring program connecting senior level electrical engineering students in the 425 Design and Fabrication Class and K-12 schools, particularly traditionally underrepresented minorities and females. Through this inter-level connectivity it is felt that students will feel more relevance to their math, science and technology classes and that significantly more serious consideration of a career in engineering would result.
MEMS425 poster