Development of an Interferometer Diagnostic for the Spheromak Turbulent Physics Experiment (STPX)

ORAL

Abstract

Laser interferometry is a proven method for measuring electron density in fusion plasmas. Typically, far-infrared interferometers are used because of the large phase shift due to the change in the index of refraction of the plasma and their relative insensitivity to vibrations. A two-color (CO$_{2}$: $\lambda $=10.6 $\mu $m, HeNe: $\lambda $=633 nm) interferometer has been designed for installation on STPX. The interferometer is a Mach-Zehnder configuration with a single-chord, double pass probe beam. The laser beams copropagate along a 10-meter path for vibration subtraction along with frequency modulation for heterodyne detection. Detection is carried out using a HgCdTe photoconductor for the CO$_{2}$ and a Si APD for the HeNe. The capabilities and challenges with the installation of the interferometer on STPX will be discussed.

*Work supported by grants from the US Department of Energy.

–

Authors

  • Jerry Clark

    • Florida Agricultural \& Mechanical University, Center for Plasma Science \& Technology, Tallahassee, FL

  • J.B. Titus

    • Florida Agricultural \& Mechanical University, Center for Plasma Science \& Technology, Tallahassee, FL
    • Florida Agricultural \& Mechanical University, Tallahassee, FL
    • Center for Plasma Science \& Technology, Florida Agricultural \& Mechanical University, Tallahassee, FL

  • A.B. Alexander

    • Florida Agricultural \& Mechanical University, Center for Plasma Science \& Technology, Tallahassee, FL
    • Center for Plasma Science \& Technology, Florida Agricultural \& Mechanical University, Tallahassee, FL

  • E.D. Mezonlin

    • Florida Agricultural \& Mechanical University, Center for Plasma Science \& Technology, Tallahassee, FL
    • Florida Agricultural \& Mechanical University, Tallahassee, FL
    • Center for Plasma Science \& Technology, Florida Agricultural \& Mechanical University, Tallahassee, FL