Alcator C-Mod

Nathan Howard

Advisor: Dr. Martin Greenwald

Updated: 07/14/06

Transport, the loss of energy, particles, momentum, etc. from a plasma, is perhaps the most significant problem left to be understood in the development of a fusion reactor. Despite a well accepted and tested neoclassical theory of transport, experimental results differ from those predicted and the current theories of turbulent transport are incomplete. Currently, a great deal of research is being performed on different aspects of transport in an effort to explain the anamolous transport observed in all tokamaks. My work particularly focuses on the areas of particle and impurity transport, which have very important implications on fueling and peaked density profiles in tokamaks. Both of these aspects have great implications on the performance of any future fusion reactor.

Much of my time has been dedicated the study of particle transport and specifically the determination of particle transport coefficients. The use of smoothed density profiles along with the development of numerical computer codes that model the non-steady state behavior of the particle transport in Alcator's plasmas, allow for the determination of some basic transport properties present in magnetically confined plasmas. This non-steady state behavior, which is typically in the form of L –H and H-L transitions, allows the separation of the convective particle flow terms from the particle diffusion terms in the transport equations and therefore provides more detailed information on the plasma transport. The ultimate goal of this research is to shed some light on the physical processes that lie behind the anamolous transport that is found in all present day fusion devices.

My current work involves the set up and development of a laser blow off system for the experimental study of impurity transport. This system allows for the non petrubative introduction of trace impurities into the plasma through laser ablation of a thin film. A number of different spectroscopic diagnostics present on Alcator can then be used to track the movement of these impurities in the plasma and thus transport properties can be studied.