Digital holographic interferometry employing Fresnel transform reconstruction for the study of flow shear stabilized Z-pinch plasmas

The ZaP-HDflowZ-pinch project provides a platform to explore how shearflow stabilizedZ-pinches could scale to high-energy-densityplasma(plasma with pressures exceeding 1 Mbar) and fusion reactor conditions. TheZ-pinch is a linearplasma confinement geometry in which theplasma carries axial electric current and is confined by its self-induced magnetic field. ZaP-HD generates shear stabilized, axisymmetricZ-pinches with stable lifetimes approaching 60μs. The goal of the project is to increase theplasma density andtemperature compared to the previous ZaP project by compressing theplasma to smaller radii ( ≈1 mm). Radial and axialplasmaelectron density structure ismeasured using digital holographic interferometry (DHI), which provides the necessary fine spatial resolution. ZaP-HD ’s DHI system uses a 2 ns Nd:YAG laser pulse with a second harmonic generator (λ = 532 nm) to produce holograms recorded by a Nikon D3200 digital camera. The holograms are numericallyreconstructed with the Fresneltransformreconstruction method to obtain the phase shift caused by the interaction of the laser beam with theplasma. This provides a two-dimensional map of line-integratedelectron density, which can be Abel inverted to determine the localnumber density. The DHI resolves line-integrated densities down to 3 × 1020 m−2 with spatial resolution near 10μm. This paper presents the first application of Fresneltransformreconstruction as an analysis technique for aplasma diagnostic, and it analyz...

Source: Review of Scientific Instruments - October 12, 2016 Category: Physics Authors: M. P. Ross and U. Shumlak Source Type: research