Plasma Density Measurement On The TAE Bias Test Stand With A Millimeter-Wave Interferometer

Active control of electrode biasing of the divertor plasma in C-2W device plays an important role to achieve the sustained steady-state high performance C-2W FRC plasma [1]. To study the electrode biasing effects with different biasing configurations, TAE is in the process of building a bias test stand to support the Copernicus design, TAE's next FRC machine, and its future operation. To characterize the plasma behavior, a mm-wave interferometer is being built to install on the bias test stand. The system is an upgraded diagnostic from the one that was used on our C-2U machine [2]. The interferometer is a heterodyne system with the probe beam at 139.9 GHz and the local oscillator at 35 GHz which is frequency quadrupled before mixing with the probe beam. Currently the upgraded system has been installed on an optical table in the lab for bench testing. The upgraded design, bench test results, and initial plasma density measurements will be presented.