Plasma density measurements on the FuZE-Q sheared-flow-stabilized (SFS) Z pinch

Zap Energy is developing the sheared-flow-stabilized (SFS) Z pinch for use as a compact fusion energy source. On the FuZE-Q device, line-integrated plasma density is measured at several locations in the accelerator and compression regions with a 633 nm, fiber-coupled interferometer. Additionally, a digital holographic interferometer (DHI), operating at 532 nm, is used to image the plasma density in the compression region. Diagnostic designs and upgrades, along with recent data are presented. In the accelerator, transient, line-averaged densities in excess of 2 × 10²³ m^-3 are measured, and data indicate higher values in the compression region. Density observations are compared with data from other diagnostics such as high-speed camera images, spectral line emission, and magnetic field probes.