FRC and Plasma Diagnostics Research
Tobin Munsat, Sam Wurzel, William Willcockson, and C. Leland Ellison

The FRC and Plasma Diagnostics group is working on a number of projects based on measurement and assessment of turbulence and cross-field transport in Field Reversed Configuration (FRC) and other magnetically confined plasmas. This work combines local experiments at CU with collaborations with universities and national laboratories.

The Colorado FRC
A new experiment has been built at CU for the study of turbulence, flow, stability and cross-field transport in a field-reversed configuration. The facility is a merged-spheromak device driven by magnetized coaxial plasma guns. Experimental emphasis is given to advanced diagnostic development, including high spatial resolution and high time resolution instruments for measurement of fluctuating quantities and bulk velocity in high beta plasmas. Instruments at various stages of development include a multichord quadrature CO2 interferometer, a multichannel Mach-probe array, a multifrequency reflectometry system, and a number of magnetic diagnostics.

Microwave Imaging Diagnostic Development
Diagnostic development work involves an ongoing collaboration with PPPL, U.C. Davis, and the FOM Institute in The Netherlands to develop a new microwave imaging instrument for simultaneous density and temperature fluctuation measurements in tokamaks. The instrument is a combined Electron Cyclotron Emission Imaging (ECEI) and Microwave Imaging Reflectometer (MIR) system, which is installed on the TEXTOR tokamak. Both subsystems use a shared set of large microwave optics to image the emitting/reflecting layer onto an array of detectors to provide high-resolution, time-resolved measurements.

Velocity Fields in edge turbulence images on NSTX
Additional data analysis work by the group includes collaboration with the NSTX spherical torus at PPPL. This research involves the derivation of velocity field maps from time-dependent image sequences produced by the Gas Puff Imaging instrument. This is a diagnostic system which records line-emission from the edge of tokamak plasmas with high spatial and temporal resolution. The velocity-field analysis reveals the dynamics of intermittent structures visible at the plasma periphery.