This award is made in response to a proposal submitted to and reviewed within the context of the NSF-DoE Partnership in Plasma Science and Engineering joint solicitation NSF 08-589. The award provides funds to support undergraduate participation in the overall research effort, which is being funded by the DoE under contract DE-FG02-99ER54543.
Plasma transport phenomena generally involve fluctuations. Thus, a predictive theory of transport must describe them. The proposal is to determine the velocity-space structure of the fluctuations by making measurements between two spatial points and at two different ion velocities. Such measurements have never been made and provide a unique opportunity for new detailed tests of fluctuation theory. The proposed experiments are a logical and natural extension of the earlier work which has demonstrated the feasibility of phase-space resolved fluctuation measurements.
Understanding fluctuations is intimately linked to understanding the transport phenomena as well as the dynamics of plasmas. For example, the MFE fusion energy program has identified the need for well diagnosed experiments on ion-scale fluctuations with the goals being to characterize the fluctuations and to understand the mechanisms of transport. Fluctuation induced transport is fundamental to nearly every physical situation involving plasmas from space and astrophysical contexts to industrial applications. The experimental techniques developed in this research, specifically those having to do with laser induced fluorescence, are applicable in other contexts and so contribute to the general research infrastructure.
Graduate students, undergraduate students, and high-school students are involved in projects related to the research. The researcher also uses the laboratory as a starting point for popular lectures. The public lectures have also led to short-term collaborations helping local industry (mostly related to physical acoustics).
The undergraduate participation adds a broader educational impact through the early-year training of students by introducing them to scientific research as a possible career path.
In this project we explored the many complex ways that plasmas can move - both electrically and mechanically - with the aid of laser measurements. Using the same principle that police use to detect speeding cars (the Doppler effect) we selectively observed the vibrations of ions in an ionized gas (a plasma) and compared them with theory. What we observed is that the plasma has more complex ways of moving than was previously known. Normally, the waves and vibrations of a plasma are described using a "fluid" theory. One that treats plasma as if it were a gas or a liquid. However, plasmas have much more complex behavior because the individual particles do not collide with each other rapidly in a plasma the way they do in a gas. What we found is that the fluid theory does very well as describing some waves, but missed many other type of wave completely. Consequently, the vibrations of the plasma can be (and are) very different depending on which speed of particle you are observing. This results in there being many more types of wave traveling through plasma than through a gas, and each of these waves has its own type of vibratory motion (both electrical and mechanical). Our work has been to experimentally explore the types of wave that exist. Since the environment in outer space (and even in the ionized upper atmosphere of the earth) is in the plasma state, the existence of all these kinds of wave can affect radio communications as well as weather (and space-weather) events. In the course of this work we built a number of pieces of equipment (often as student projects). These projects included building a custom laser and wavelength- resolving light detection system that forms an image of the plasma in the way that a camera does. Students also built periscopes for collecting scattered laser light and devices for measuring the wavelength of the lasers. We also completely rebuilt and upgraded the entire experimental plasma chamber, laser, and detector systems.
