Research Projects
The projects and groups listed below are intended to provide interested students with an overview of research offerings in the Department of Physics, University of Washington. The list is not inclusive, but it is representative of the breadth of research opportunities within the Physics Department and INT. Students with particular interests should feel free to ask Wick or Martin whether special projects can be designed: we have done this in past years with good success.
NUCLEAR PHYSICS LABORATORY
Measurements of Photons from Resonances in 8Be
Faculty: Kurt Snover, Derek Storm, Jos van Schagen
This project involves the use of the NPL's superconducting linear accelerator to test symmetries that, in the Standard Model, relate the weak interaction to electromagnetism. Our precision measurements will help determine whether second-class weak currents exist, and test the conserved vector current hypothesis. The REU student will help our team measure the rate of photons produced when energetic helium nuclei collide and fuse with helium nuclei at rest. Opportunities exist for software development, accelerator operation of a superconducting linac , experimental measurements and data analysis.
The Rate for 7Be Solar Neutrino Production
Faculty: Kurt Snover, Tom Steiger, Jean-Marc Casandjian, Eric Adelberger
The "solar neutrino puzzle," one of the current major puzzles in physics, consists of the observation that many fewer neutrinos are observed here on earth relative to solar model calculations of the expected flux. We are developing the apparatus and techniques for a new experimental measurement of the cross section (reaction rate) for the fusion of 7Be nuclei with low energy protons. This reaction rate is a crucial ingredient in the solar model flux calculations. The interested REU student will have a hands-on participation in this work.
Testing the Equivalence Principle using a High-Precision Torsion Balance
Faculty: Eric Adelberger, Stefan Baessler, Jens Gundlach, Blayne Heckel
The Eot-Wash group is building a new instrument to make the world's most precise test of Einstein's equivalence principle which says that gravitation is equivalent to an acceleration of the coordinate frame and is the underpinning of general relativity. You can find out more about this by clicking on the Eot-Wash research group on the University of Washington Physics Department home page on the Web. We have several interesting technical projects suitable for experimentally inclined summer students. Our lab is well equipped with instrumentation, machine and electronic shops so that plenty of resources are available for attacking these problems. Two examples are:
1) developing a higher performance optical system for reading out the twist of the torsion balance
2) developing an actively controlled temperature-regulation system for the torsion balance. We currently hold the temperature constant to a few millidegrees and want to do better.
Measuring the Gravitational Coupling Constant G
Faculty: Jens Gunlach, Eric Adelberger, Blayne Heckel
The gravitational constant (Newtons constant) is one of the most fundamental constants in nature. Surprisingly its value is still relatively poorly known and has recently been subject to some controversy. We have developed a new method to measure this constant accurately and are now building the apparatus. Possible projects for an REU student range from numerical simulations to designing and building of the actual hardware. Check out http://mist.npl.washington.edu/eotwash.
Weak Interactions, Symmetries, and Neutrinos
Faculty: Steve Elliott, Hamish Robertson, Tom Steiger, John Wilkerson
Our group is involved in a number of projects on the weak interaction and neutrinos. These include emiT, a precision neutron beta decay measurement that is testing time-reversal invariance, analysis of data from the SAGE gallium solar neutrino experiment (an experiment sensitive to the low-energy p-p fusion neutrinos), and measurements and analysis of a new exploratory experiment on the detection of cosmic-rays in the radio-frequency spectrum. We are also investigating an idea for using Pb as a target in a new neutrino-oscillation search at an accelerator, as Pb has a relatively large cross section for neutrino interactions. An REU student is encouraged to consider working with us in any of these areas.
The Sudbury Neutrino Observatory
Faculty: Peter Doe, Steve Elliott, Hamish Robertson, Tom Steiger, John Wilkerson
Construction of the Sudbury Neutrino Observatory (SNO) in Sudbury, Ontario, is essentially complete, and initial data-taking is expected to take place in spring 1998. The experiment is aimed at trying to resolve the "solar neutrino problem", namely that experiments see fewer neutrinos from the sun than predicted by theory, and also that an explanation of the problem seems to require new neutrino properties such as mass and violation of lepton family number. Work at UW in the summer of 1998 by our SNO experimental group (5 Faculty, 6 graduate students) will include the final testing and first use of the SNO primary data acquisition system and the construction of a neutron detector system that will be used in SNO to make the key measurement of neutral-current neutrino interactions.
GEOPHYSICS
The Physics of Lightning
Faculty: Marcia Baker, Brian Swanson
Large drops (500 microns to millimeters in size) are necessary for lightning initiation. We suspect they shatter as they freeze and that the fragments play important roles in charge transfer. We have designed and built a table top apparatus to study this phenomenon, which would serve as an excellent REU project.
Experiments and Theory in the Phase Behavior of Ice in Porous Media: Frost Heave
Faculty: Greg Dash, John Wettlaufer, Van Hodgkin
A primary motivation for understanding surface phase transitions in ice concerns the important roles they can play in a host of environmental problems ranging from polar stratospheric cloud chemistry to frost heave in porous media. The dramatic deformation of water saturated soils in cold climates is known generically as "frost heave." Yet it is rather more appropriate to refer to frost heave as the collective action of a number of phenomena each of interest and intense study in its own right. Although frost heave is clearly not caused by the volume expansion of water during solidification, for many years it has been known to be associated with the existence of stable liquid water at subfreezing interfaces. However, the varied causes of this water have obscured attempts to extract the fundamental mechanisms driving frost heave. In a porous medium, curvature, confinement, interfacial roughness and disorder, impurities and interfacial premelting all contribute to the finite volume fraction of water at subfreezing temperatures. Individually, these effects have distinct temperature dependencies, but their combined effects have thus far limited frost heave research to semi-empirical treatments. It is for this reason that we have focused on isolating the role of interfacial melting in the existence and mobility of unfrozen interfacial water. The intermolecular origin of the films, the effect of external forcing and the geometry of the confining wall are the main features of our studies. A student would have an opportunity to engage in both experimental and theoretical work. The table top experiments center around an optically thin chamber that allows visual, photographic and interferometric observation of ice growth and solute redistribution in their very early development. Theory involves local studies of thin film flow and continuum mechanical treatments of collective phenomena.
PHYSICS EDUCATION GROUP
Instructional Strategies for Teaching Physics
Faculty: Lillian C. McDermott, Paula Heron, Peter Shaffer, Stamatis Vokos
The Physics Education Group conducts research on student understanding of physics and uses the results of this research to guide the design of instructional materials. REU participants will have the opportunity to participate in programs shaped by the group's research, such as the summer program for K-12 teachers and the tutorials for the introductory physics course. In addition to taking part in classroom activities, the 1995, 1996, and 1997 REU participants assisted in investigations of the effect of different instructional strategies on student understanding of important fundamental concepts by analyzing student performance on qualitative questions before and after instruction.
EXPERIMENTAL PARTICLE PHYSICS
The Large Hadron Collider
Faculty: Henry Lubatti
The experimental particle physics group is preparing to participate in the next generation of experiments at the Large Hadron Collider, an accelerator under construction at CERN, Geneva. The summer project would involve the testing of components of a muon system for a detector to be constructed at the LHC. An REU student could be easily integrated into the measurements and evaluation. The required physics knowledge can be acquired from discussions with group members and from reading.
Neutrino Physics with SuperKamiokande
Faculty: Jeff Wilkes, Ken Young
Super-Kamiokande is the worlds most sensitive working neutrino detector now taking data. We have already obtained the world's largest data sets to examine the hypothesis of neutrino flavour oscillation and proton decay. The dominant neutrino sources are the solar neutrinos and the neutrinos created by cosmic rays in the earth's atmosphere. These sources yield neutrinos with quite large and predictable variations in proper time between production and detection and so are amenable to neutrino flavour oscillation studies. In addition, we are capable of making detailed studies of super novae which occur in the Milky Way galaxy and for very sensitive searches for proton decay. Proof of either neutrino flavour oscillation or proton decay would yield insight into NEW physics beyond the standard model. In addition, we will be making preparations for a new project in which an artificial neutrino beam will be directed from a particle accelerator through 250 km of earth to Super-K. This experiment will give us a neutrino source with an event by event accurate determination of the proper time between production and detection. One or two REU students are invited to join our staff and graduate students in working on hardware construction, data analysis and support software.
COSMOLOGY
Dark Matter
Faculty: Chris Stubbs
We are engaged in a number of projects that address some of the most fundamental open questions in cosmology: 1) What is the nature and distribution of the dark matter that is the gravitationally dominant constituent of the Galaxy? 2) Will the expansion of the Universe continue forever, or will the Big Bang be followed by the big crunch?. We develop innovative instrumentation for astronomical observations, and in particular we make extensive use of the 3.5 meter diameter ARC telescope in New Mexico. One or more REU students would be welcome to join our group to help with our instrumentation efforts.
Cosmology and Large Scale Structure
Faculty: Tom Quinn, George Lake, Derek Richardson
Our knowledge of the largest structures in our Universe has grown dramatically in the past decade due to both both high quality observational surveys and theoretical simulations. Nevertheless, our understanding has been held back because of the difficulty in visualizing the complex three-dimensional structure. For example, a debate continues as to whether galaxies are found primarily on two-dimensional ``walls'', or one-dimensional ``filaments''. One REU student is invited to join our effort in analysis and visualization of observed and simulated galaxy catalogues.
Cosmological Nucleosynthesis
Faculty: Craig Hogan
The project will be scripting a web-based tool to assist in comparisons of observed astrophysical light-element abundances with the predictions of Standard Big Bang Nucleosynthesis. At present the precise predictions are not easily available to observers as they require running a simple but not widely maintained code using current values for nuclear reaction rates. The goal of the summer project will be to develop a web page which will allow the user to compute and tabulate or plot abundances including errors for various values of the baryon-to-photon ratio.
CONDENSED MATTER EXPERIMENT
Low Temperature Behavior of Thin Films
Faculty: Oscar Vilches
The Low Temperature Physics laboratory is engaged in experiments to study, at low temperatures, the thermal properties of one to several layers thick films of hydrogen, deuterium, deuterium hydride, and the two stable isotopes of helium, 3He and 4He. For single layer films, leading questions are: a) to what extent it is possible to control the solidification temperature of the molecular hydrogen isotopes, b) phases and phase separation in 3He-4He mixtures, c) supercooling of hydrogen, and d) frost heave in hydrogen in porous media. Items (a) and (c) are related to the possibility that if molecular hydrogen films could be kept in the fluid state down to about 1K they will become superfluid. Experiments are done in the range of 1 to 10K. Item (b) has a very interesting counterpart in bulk mixtures, where isotopic phase separation is observed in both the solid and the liquid mixtures. Item (d) has a strong similarity to studies of frost heave in water/ice, with the added possibility that quantum mechanical zero point motion plays a role. Depending on the interest of REU participants and the status of the experiments, students will be either incorporated to an existing team of resident student experimentalists, or be given a separate project which could be made part of a project in one of the four areas above.
Scanning Probe Microscopy
Faculty: Sam Fain
An REU student could learn about atomic force microscopy assisting in experiments on ice surfaces in my lab or do a project using the instructional scanning tunneling microscope recently acquired by the physics upper division instructional laboratories.
Materials Physics
Faculty: Tom Pearsall
I have three materials science projects suitable for REU students. The first involves micro-electro mechanical systems. We are designing and fabricating an optical bench with micrometer dimensions using precision lithography. This bench permits optical beam processing on the integrated circuit chip level. The second is a study of epitaxial growth of ordered semiconductor alloys. We are using molecular beam epitaxy to create metastable ordered alloys of GaAs and GaN. These alloys may exist only if they are ordered. We will characterize these materials for bandgap and conductivity. The third project is real-time detection of molecular composition in thin film deposition. We are using laser-induced fluorescence to identify the composition of source molecules used in thin film deposition by chemical vapor deposition. We are using a tunable UV Dye laser for excitation in the wavelength range between 200 nm and 400nm.
ATOMIC PHYSICS
Atomic Tests of Parity Nonconservation and Time Reversal Symmetry
Faculty: Norval Fortson, Blayne Heckel, Bruce Warrington, Michael Romalis
Students will be able to work directly on small scale atomic physics experiments that probe the elementary particle physics frontier. In one experiment, the electroweak force between electrons and quarks inside atoms is measured by the small degree of left-right asymmetry displayed by these atoms. In another, a permanent electric dipole of an atom is being looked for as evidence of forces that distinguish between forward and backward in time. In both kinds of experiments, students can use and develop high precision lasers and other tools of modern atomic physics.
Penning Trap Mass Measurements
Faculty: Robert Van Dyck, Jr.
The primary effort of my group is the development of the UW-Penning trap mass spectrometer to the highest possible accuracy. Using only rf methods for observing the normal mode frequencies of a single isolated ion, bound to a small electro-magnetic cage called the Penning trap, it has become possible to measure masses of low mass-to-charge ions relative to an appropriate calibration ion with a precision that is now expected to exceed one part in 10-billion. An applied magnetic field forces the ion to revolve in circular orbits about the field direction at the cyclotron frequency, which can be measured and compared with the corresponding frequency of the calibration ion, alternately stored in the same apparatus. The ratio of these two frequencies (corrected for trapping fields) yields the inverse mass ratio. Our immediate goal is the continued development of a high precision and high accuracy mass spectrometer with the added capability of external loading of ions. One possible application of such a spectrometer is an experiment that will yield an independent determination of the fine-structure constant. In fact, the long-range goal of all our efforts is to increase the consistency and accuracy of the total list of physical constants.
Measurements of the Electron and Positron g-factors
Faculty: Hans Demelt, Paul Schwinberg, Robert Van Dyck, Jr.
We are engaged in an effort to further improve our measurements of the electron and positron g-factors, which have provided a test of quantum electrodynamics of unprecedented accuracy. Our immediate goal here is to re-evaluate that experiment in hopes of first developing a more efficient method of loading positrons into our traps. Then, we will attempt to improve on our previous matter/anti-matter comparison by an order of magnitude.
RESEARCH IN THE PHYSICS OF MUSIC
Faculty: Vladimir Chaloupka
Physics of Music investigates the production, propagation and perception of musical sound. Some current projects include room acoustics studies using the modern "minimally intrusive" techniques, physics of consonance/dissonance, experiments on the absolute pitch perception, and measurement and evaluation of the pipe organ sound, with emphasis on the role of physical imperfections necessary to achieve the perception of perfection. Simulations are performed using advanced MIDI techniques. In addition to Physics, these projects touch on Computer Science, Electrical and Mechanical Engineering, Hearing Research, and of course Music. Many aspects of this research are well suited for the participation of undergraduate students.
THEORY
Atomic Cluster Physics
Faculty: Aurel Bulgac
Atomic clusters are like molecules in a way, only they are usually very large (from a few atoms to a few millions) and in most cases all atoms are identical. Perhaps the most famous one is the C60, often called buckyball, and for which Curl, Kroto and Smalley have been awarded the 1996 Nobel Prize in Chemistry. Atomic clusters are interesting since they do not behave either like simple molecules or like small pieces of matter and thus they provide the missing link between the atoms and bulk materials. Their properties are often puzzling and not yet completely understood. There are a variety of projects an REU student can work on: structural properties, phase transitions, goemetry of a cluster, electronic properties, and excitations. During summer, 1998, many of the world's experts in this subject will be in residence at the INT. Thus any student interested in this subject will have unusual resources at hand.
Numerical Methods for the Time-Dependent Local-Density Approximation
Faculty: George Bertsch
A powerful technique to model the electronic motion in atoms, molecules, and condensed matter is the time-dependent local-density approximation. The theory is limited by the computational methods, but so far they have not been optimized for this problem. The research is to make computer programs to try vary numerical techniques to improve the performance of the method. If we find methods that improve performance by a factor of 3-10, the reseach would not only be publishable but might lead to widespread adoption of the technique in the condensed matter community. The student must have experience in scientific programming and a concentration of course work in mathematics or mathematically oriented science (physics or engineering). Examples of the research in this area may be found on my web page, http://archive.int.washington.edu/users/bertsch/