Proposal

Sonoluminescence (SL) was first observed in the early 1900ís. It did not become widely known until Seth Putterman of Cal. Tech. began studying it in 1989 [1]. Since then it has come to the forefront, with more and more labs endeavoring to answer different questions [1,3,4,5]. In SL an acoustically levitated bubble grows and collapses in a repeating cycle. There are many seeming mysteries attracting scientists to the study of SL, such as the relative energies of sound and light -sound is 12 orders of magnitude weaker than light, which it produces here- and what could be contributing to make up for this difference. The temperature of this bubble can reach higher than 15,000 K [5], for comparison the surface temperature of the sun is about 5,500 K. This bubble has been found to be a thermally conducting, partially ionized plasma [2]. At each collapse a burst of light is emitted, the growth and collapse time is so short that the light appears constant. Current theories find that the ~100ps width of this burst is due to electron conduction and the fluctuating opacity of the plasma [3].

The Advanced Physics Laboratory (course 331) is strongly recommended for all physics majors planning to do research during the summer or to pursue science after graduation. Taking 331 this semester is what led me to the idea of adding a sonoluminescence experiment to the course. Most experiments worked with during the course are already fundamentally understood by physicists. It is still beneficial for undergraduates to do these experiments, but an experiment in a current hot area of research has advantages also. During the course each student writes two publication style papers on two of the experiments they do. It is necessary to do outside reading and research for these papers. A SL paper has the advantage of teaching the student how to write a paper that may have as many questions as answers. In the SL experiment students could follow the lab book, or research current questions about SL and design their own experiment to explore one.

Over the course of the 10 weeks this summer I will design and build the apparatus, stabilize the set up and experiment, and write the laboratory guide. I will begin by researching how different laboratories have built their apparatus and what the advantages and disadvantages of each method are. In order to design my apparatus I will have to decide what the goals for the 331 physics lab are in comparison to those of an active research lab. I will build the apparatus itself, and then make adjustments to it to achieve the desired results. I will develop a reproducible experiment, and write it in detail for future 331 lab students. I will have guidance from Mike Noel and Thomas Carroll during each phase.

The apparatus for the experiment can be surprisingly simple. A function generator is used as a source of power and to control the frequency. An audio power amplifier is used to create the correct sonic pressure. A Piezo-Electric Transducer (PZT) creates an ultra-sonic horn (USH) when attached to a metal rod [6]. The bubble will be created inside a spherical glass flask, filled with a water and glycerin solution. Much of the equipment for the apparatus is already available in the physics department. A high estimate of the cost is $500 for anything we do not already have.

References:
1. G. Brumfiel, Nature, Vol 437, 27 October 2005
2. W.C. Moss, Physical Review E, Vol 59 Issue 3, March 1999
3. W.C. Moss, Science, Vol 276, 30 May 1997
4. D.J. Flannigan, K.S. Suslick, Nature, Vol 434, 3 March 2005
5. D. Lohse, Nature, Vol 434, 3 March 2005
6. C.J. Visker, Hamline University, St. Paul Minnesota, Physics Honors Project, 2005