Implementation of an eight-cord equal path length, heterodyne interferometer on the Fusion Z-pinch Experiment FuZE*

The Fusion Z-Pinch Experiment (FuZE) project uses a radial-sheared axial flow stabilized Z-pinch to develop a compact fusion device. The machine is able to drive ~ 200 kA of pinch current, compressing the pinch to a radius of ~ 3 mm. By seeding the hydrogen Z-pinch with a minority concentration of deuterium, thermal fusion neutrons are produced. An extensive set of diagnostics provide key measurements, including an eight-cord equal path, heterodyne, quadrature phase differential interferometer. Three chords are located at acceleration region to investigate the snowplow and deflagration processes for long-lived Z-pinch structures. Five chords are located at the midplane of the 50 cm Z-pinch assembly region with 1 cm vertical spacing to measure the evolution of plasma density profile. Assuming cylindrical symmetry, Abel-inverted radial density profiles are reconstructed from these five-chord line-integrated electron density data. Furthermore, assuming a constant drift speed, the temperature profile is calculated and compared with ion Doppler spectroscopy measurement. The design of the interferometer and detailed data analysis will be presented.