Alcator C-Mod

Vincent Tang

Title: Characterization of Alcator C-Mod ICRF minority protons via a multi-channel Compact Neutral Particle Analyzer and full wave/Fokker-Planck simulations.

Thesis Advisor: Prof. R.R. Parker

Updated: 07/14/06

My research is currently centered on the diagnosis and physics of energetic particles in fusion plasmas. Specifically, in Alcator C-Mod, a heating scheme called ICRF minority heating is used to deliver megawatts of power to the plasma via microwaves. These microwaves interact primarily with the protons that form approximately 5% of the mostly deuterium plasma; the waves thus heat these minority protons to temperatures of ~100keV. These minority protons then slow down on the cooler bulk plasma and heat it. Thus, the minority protons can be seen as a power conduit coupling the external power sources and the bulk fusion plasma. From a physics point of view, these heated protons also permit the study of energetic ion confinement in fusion plasmas. This is an area of interest because self-heated reactor-grade plasmas will contain a large population of very energetic alphas particles created from the D-T fusion reaction.

Experimentally, my thesis work on Alcator C-Mod is composed of a new multi-channel Compact Neutral Particle Analyzer (CNPA) that can diagnose these energetic protons in both real and phase space. This diagnostic resulted in first time measurements of the core minority proton population in Alcator C-Mod. On the theoretical side, the work consists of simulating these energetic protons using state-of-the art full-wave and Fokker-Planck (AORSA/CQL3D) solvers. Preliminary results are encouraging and show that the use of these very complex codes is required to simulate these energetic populations with some degree of accuracy. These experimental and theoretical studies form a solid foundation for the examination of even more complex wave-energetic particle interactions, such as Toroidal Alfvén Eigenmodes.