Interferometry Of Single And Double wire plasma radiation source loads

Abstract

Models developed for the implosion of multi-wire arrays used as plasma radiation sources depend upon the assumption that the entire wire mass is ionized, forms a symmetric thin plasma shell and participates in the implosion process. Any deviation from this scenario in an actual experiment can lead to poor correlation between the model and experimental measurements at best or an incorrect picture of the real physics at worst. In order to address this problem, HY-Tech researchers are applying various time resolved interferometric techniques to study the evolution of plasmas from single and dual wire loads. One system employed uses a flashlanip pumped dye laser (approximately 300 ns pulse length) as a source and a gated, intensified framing/streak camera as the detector. Used in the framming mode, 20 ns snapshot-interferograms are produced giving a full view of the wire and surrounding plasma. Used in the streak mode, a radial view of the interferometer fringes (tirne resolved over the laser pulse) is produced for a given axial position on the wire thus providing a measure of the radial extent and motion of the wire plasma. In a separate system, single or double pulse, diffuse illumination holograms are produced with a ruby laser (10 ns pulse width). The double pulse hologram produces an interferogram upon reconstruction while the single pulse hologram reconstructs the original wavefront which can be post-processed using Schleiren or shadow techniques to highlight and measure plasma density gradients. Measurements will be presented showing the evolution of plasmas from single and dual wire loads.