Graduate Seminar, 23rd May

Speaker: Dobromił Załoga

Title: Research on emission of visible and X-ray radiation, and estimations of electron temperature in discharges of Plasma-Focus type

Abstract: This presentation reports on results of detailed experimental studies of the visible and x-ray emission, as well as estimations of plasma electron temperatures in discharges of the Plasma-Focus (PF) type, particularly in the PF‑1000U facility at IPPLM. In particular there are summarized measurements of the visible radiation from PF discharges, measurements performed by means of laser interferometry, time-integrated measurements of x-rays, as well as time-resolved measurements of soft x‑rays, which were performed by means of framed MCP (Micro-Channel Plate) and “pinhole” cameras equipped with scintillation detectors, as well as by means of a set of 4 semiconductor PIN-type diodes equipped with appropriate absorption filters. It was shown that the formation of different microstructures inside the dense and hot plasma column during PF‑type discharges depends strongly on experimental conditions, and particularly on gas conditions. At the same experimental conditions microstructures in form of plasma-current filaments are relatively well reproducible in the macroscopic scale, but microstructures in form of hot-spots are irreproducible. Due to a stochastic character of the formation of such microstructures, their parameters (i.e. positions, lifetime, density and electron temperature) can differ considerably, e.g. local values of electron temperature Te can change in a range from about 100 eV to about 880 eV.