Physics 451: Fall 1996

Nuclear Magnetic Resonance

In addition to the physics of the phenomema, you will need to learn something about tuned LC circuits and impedance matching, about how to produce an inhomogeneous magnetic field and to measure it. Having picked up a black box for measuring magnetic fields, you may well decide that you should find out how it works and do a "mini-experiment" on how magnetic fields are measured. In the end you may relate what you have learned to Magnetic Resonance Imaging (MRI) which is used universally as a medical diagnostic tool.

Superconductivity

1. the destruction of superconductivity by a magnetic field or by an electrical current
2. the way magnetic flux which penetrates the superconductor is quantized.
3. what happens when two superconductors are connected by an insulator.

Historically superconductivity appeared only in metals and alloys and only near liquid Helium temperatures (~4 to 20 K), but within the past 10 years a very large family of superconductors have appeared in rather complex metallic cuprates, most of which are superconductiving above liquid N temperatures (70 to 150 K). You will investigate some properties of both high and low temperature superconductors. Maybe we will try to answer the question: "Are magnetically levitated superconducting trains technologically and economically practical?"

Superfluidity

Helium gas becomes a liquid at about 4.2 K. If you cool it to still lower temperatures, there is a phase transition at about 2.2K to a new liquid state called a superfluid. Below 2.2K the real liquid is a mixture of normal and superfluid. In this regime many properties of the two components are different. It will be your job to learn to handle liquid helium; to learn about the different properties; to determine which properties we can measure and to do such measurements. In particular:

1. Devise a way to observe the phase transition from normal to superfluid.
2. Measure the velocity and attenuation of a thermal wave at several temperatures in the superfluid phase.

X-ray Diffraction

You all know about the optical diffraction (interference) grating and roughly how it works. In fact, any periodic structure will produce an interference pattern when it is irradiated by an electromagnetic (or deBroglie) wave whose wavelength is approximately equal to the spacing, d, of the periodic structure. Starting with a system in which both d and the wavelength are about 3 cm, you will learn how both the geometrical and physical properties are important in the interaction. You will then proceed to the case where both d and the wavelength are about 10^-8 cm and finally if we are lucky, take some data on a real crystal using a "state of the art" x-ray system and do a careful analysis of the crystal structure of the crystal. We may consider the connection between what you have learned and the medical diagnostic tool, the CAT scan.

Nuclear Radiation Physics

This is a set of experiments in which you will learn some of the experimental techniques which are used in Nuclear Physics to study the energy spectrum, absorption and the lifetime of the nuclear decay process. These include:

1. The properties of different detectors and the electronics to operate those detectors and analyze the spectrum of radiation detected by them.
2. The energy spectrum of several different radioactive decay processes.
3. The "ultimate" experiment involves measuring the lifetime of muons which are produced by cosmic rays and which decay in the laboratory.
   Here too we may study some aspect of the biological effects (good and bad) of nuclear radiation.
   

Physics 451

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