Seminars are held on Tuesdays, 3:45-4:45pm in SB 101, unless otherwise noted. Meet at 3:30 in SB 157 for refreshments (refreshments are available even on Tuesdays with no seminar!). See Calvin's Visitor Resources for maps and directions to the Science Building.

Schedules from previous semesters:Spring 2004, Fall 2003, Spring 2003, Fall 2002

October 4: Locking Laser Frequencies to Atomic Frequencies.
         Chris Walker, senior, and Prof. Matt Walhout.
The atom-trapping experiments here at Calvin require lasers with very well defined frequencies. We will give an overview of our investigations of krypton atoms and point out the various atomic transition energies to which our lasers must be matched. We will then describe some of our methods for locking lasers to the atomic resonances. In particular, Chris Walker will describe a device that he built in order to lock the frequency of a diode laser to that of another, "master" laser. His lock involves the mixing, or "heterodyning," of two lasers on a fast detector, and it allows the difference between the laser frequencies to be monitored and controlled with radio-frequency electronic components.

November 4: "Keep the Noise Down!" Using Thermodynamics to Improve Radio Receiver Performance.
         Prof. Steve Remillard.
Tired of poor cell phone service? Limited coverage of the radio tower is one of the factors that cause you that grief. And this limitation arises from one of the system designer's greatest nightmares: noise. This seminar will treat the problem of noise, from its basic physics, to its impact on the radio and on system performance. The review of the physics of noise will lead directly to a solution for noise reduction, which was built in the laboratory, tested in the field and developed into commercial products.

November 9: Characterizing the Microquasar SS 433: Discovery of the Mass Donor Star.
         Dr. Todd Hillwig, Valparaiso University.
SS 433 is an X-ray binary, a close binary star system in which one of the two stars is either a neutron star or a black hole. SS 433 is also one of the prototypes of the class of "microquasar," X-ray binary systems with relativistic jets. Spectroscopy of SS 433 was obtained in the poorly studied blue spectral range of optical light. The spectra were obtained at the optimal time to observe the companion or "mass donor" star in the system. I will show that the resulting spectrum is consistent with an A-type supergiant star. Determining the characteristics of this star allows us to find the masses of both of the stars in the binary system. The impact of the results on the theory that this system contains a black hole will be discussed. I will also present current research results by other groups and future proposed research plans for this interesting system.

November 30: The Singing of the Waters: The physics, engineering, and applications of nuclear magnetic resonance in the earth's magnetic field.
         Prof. David Van Baak.
Nuclear Magnetic Resonance (NMR) is a mature field based on physical discoveries of half a century ago, but it has become so important in the sciences and medicine that there's a continuing imperative to train scientists in its principles. One effective way to do so is to perform NMR in the ambient terrestrial magnetic field, in which NMR of protons occurs at frequencies of just kiloHertz, and on a time scale of seconds--thus directly accessible to human senses. This talk describes the design of an apparatus which makes such NMR experiments possible, and recent improvements of it developed at Calvin and now in production at TeachSpin. In addition to a variety of classic physics experiments, including the evocative phenomenon of the 'spin echo', this apparatus can illustrate the technologically important capability of Magnetic Resonance Imaging (MRI) in a conceptually understandable way. Finally, the whole project illustrates the process of science-based design and the real-life issues of prototyping and production engineering.

December 7 : Highlights of the 36th Annual Division of Planetary Sciences Meeting, November 2004.
         Prof. Larry Molnar.
In the last year, the Cassini spacecraft arrived safely in the Saturn system, two rovers have been cruising the Martian landscape, adaptive optics is making spacecraft quality images a reality for Earthbound telescopes, and much more. This presentation will review the highlights of these new observations as they were presented at the recent international meeting of the Division of Planetary Sciences. Other questions to be addressed include: What are the chances that Uranus and Neptune swapped places? What fraction of asteroids are actually asteroid pairs? Which planet has the most moons this year?