Bemidji State University
As part of a new research project sponsored by the MnSGC, two students at BSU, Lisa Rossiter and Jessica Godwin, began preparation of road logs and preliminary mapping of the Leech Lake Area this past summer. Correlation with glacial deposits in other areas of the state as well as the mapping of significant geomorphic features related to the retreat of the Wadena ice lobe in Minnesota have also been accomplished. The retreat of the Wadena ice lobe occurred about 30,000 years ago in Minnesota and details of its behavior are not well understood. The work of these students is a first step in a larger program related to topics of Global Change sponsored by BSU.

Dave Kobilka spent the summer at Washington University through support from the MnSGC conducting research on the seismology of the Tonga Trench, one of the deepest in the Pacific Ocean. An understanding of the style and tempo of subduction associated with the trench will materially contribute to our understanding of global plate tectonics

Bethel College
As part of his ongoing NASA- and AFOSR-sponsored research on the performance of infrared detectors, Dr. Brian Beeken of Bethel College is working with physics senior Brad Johnson to determine the efficiency of detectors of visible light. For the past semester, they have been testing the quantum efficiency of a photomultiplier tube (PMT) by the counting of individual photons. The quantum efficiency is characteristic of the PMT and describes what percent of incident photons actually produce a current.

Brian and Dr. Beeken have constructed equipment designed to conduct the tests. The system, shown in the diagram below, consists of three main parts: the photon source, a series of filtration devices and the PMT. The source is a 1 milliwatt stabilized, polarized HeNe laser which puts out about 1010 photons each millionth of a second. Many of these photons must be filtered out so that the PMT will have time to respond to individual photons. The filtering is accomplished with a series of glass surface reflections and neutral density filters. This system permits the relatively precise theoretical calculation of the number of photons that arrive at the PMT. These photons produce a current from the PMT, and the current is analyzed by a digital oscilloscope. A pulse on the scope indicates that the absorption of one or more photons by the PMT has taken place. A pulse produced by two photons, for example, would be twice as large as a pulse generated by a single photon. Therefore the number of photons detected by the PMT during a certain time interval can be determined, and it is this number divided by the calculated number of incident photons that is the quantum efficiency of the PMT.

The College of St. Catherine
The MnSGC supported the work of Catherine DeMarco this summer and fall as she conducted CCD optical photometry of star fields, hoping to establish standards for dwarf cataclysmic variables. Catherine's work also involved regular trips to the O'Brien Observatory in Marine on St. Croix and the use of MIRA, an extremely difficult computer program designed to analyze her observations.

Macalester College
Two undergraduate students were supported by the MnSGC to collaborate on summer research with faculty in the geology department at Macalester College. Christine Ronnback ('96) began a study with Karl Wirth of xenoliths from recent volcanoes in the Bering Sea region of Alaska, which involves detailed chemical analyses of minerals to determine the temperature and pressure history of rock fragments that were carried from the Earth's mantle and lower crust to the surface by recent lavas. Preliminary results of the project, which were presented at the fall meeting of the American Geophysical Union in San Francisco, suggest that the lower crust in the region consists of significant quantities of mafic granulite and cumulates. The project will be continued as an honors project by Christine.

A second project involved Zachary Naiman ('97) in a study of the petrography, stratigraphy and metamorphism of lava flows and associated sediments from the midcontinent rift, which involved extensive mineralogical studies of the flows using an optical microscope and scanning electron microscope to determine the igneous and metamorphic history of the southern part of the exposed rift. Preliminary results of the project were presented at the International Field Conference and Symposium on the Petrology and Metallogeny of Volcanic and Intrusive Rocks of the Midcontinent Rift System (Duluth, MN, August 1995). A manuscript describing the metamorphism and the geochemistry is in preparation. Other aspects of the lavas will be the focus of Zachary's upcoming honors project.

University of Minnesota-Duluth
Research continues at UMD with the support of the MnSGC on tidal rhythmites -- rhythmic sequences of alternating silt and mud layers produced by tidal currents. Using Greg Ojakangas's FORTRAN program which produces synthetic rhythmites given presumed orbits of the earth and moon, Ojakangas and graduate student Haichuan Tan have successfully retrieved the lunar orbital elements for the simplified case where the earth has zero tilt of its spin axis, and the moon's orbit is circular. Increasingly complex cases are under investigation. In an exciting new development in this research, Ojakangas has found rhythmic tidal sequences in the two-billion-year-old Pokegama Formation in northern Minnesota. With support from MnSGC, Geology undergraduate Leif Johnson has prepared numerous samples of these rhythmic sediments for analysis. After slabbing, the rocks are coated with oil to enhance details, and photographed. The photographs have been digitized and are currently being analyzed and processed by computer. The goal is to attempt to retrieve or constrain the ancient (2 billion-year-old) lunar orbit from the rocks.

Research at UMD also continues on computer modeling of the orbital and thermal histories of Saturn's volcanic icy moon Enceladus. The accompanying figure shows some results from this work. In the case shown, the orbital eccentricity of Enceladus (the non-circularity of its orbit) is seen to increase as it enters a resonant state with Dione, another of Saturn's moons. After an initial rise, portions of the interior of Enceladus melt and volcanism ensues to the present day. Mathematical chaos arises in many of the cases simulated by the computer program. The case shown here is one example. The goal of this research is to understand Enceladus's long history of volcanic activity, as recorded in its cratered surface, as well as to show that it is probably volcanically active today.

The University of St. Thomas
The University of St. Thomas is gearing up for a new undergraduate research program in atomic physics. The initial research efforts are focusing on electron-atom interactions, specifically the measurement of total electron scattering cross sections at low energy (a few electron volts). Understanding electron scattering is critical to understanding and modeling of many physical systems such as lasers, gas discharges, fusion plasmas, upper planetary atmosphere and interstellar clouds. Since the initial work of Ramsauer in 1921, great strides have been made in the reliability and accuracy of experimental techniques used to measure total electron scattering cross sections. However, despite the numerous improvements much work remains to be done. Student researchers will first take a measurement of the total electron scattering cross section of SO2 from 2 - 300 eV and will use transmission and time-of-flight techniques to determine the cross section.