2024/05/14(Tue) 14:00 -16:00 一樓演講廳 1F, Auditorium
Title
Study of the head-on collision of two plasma jets
Speaker
張博宇副教授 (國立成功大學太空與電漿科學研究所) Dr. Po-Yu Chang (Institute of Space and Plasma Sciences, National Cheng Kung University)Abstract
Head-on collisions of two plasma jets were studied in the laboratory. It was to simulate the astrophysical phenomena in the laboratory or to generate the stagnated plasma that commonly happens in inertial confinement fusion. The experimental platform was a pulsed-power system. The same technology will be used in the fusion facility, Formosa Intergraded Research Spherical Tokamak (FIRST), that is being developed. The pulsed-power system for the plasma-jet experiments provided a pulsed current with a peak of ~100 kA and a rise time of ~1.6 us. A bi-conical-wire array, consisting of two identical conical-wire arrays connected in series and facing against each other, was driven by the pulsed-power system. Both conical-wire arrays were made of four tungsten wires with a diameter of 20 um. The inclination angle, the diameter of the bottom, and the height of each conical-wire array were 30°, 5mm, and 10 mm, respectively. When the bi-conical-wire array was driven by the pulsed-power system, the tungsten wires were heated, vaporized, and ionized by the current via ohmic heating. The ablated plasma from the tungsten wires was pushed toward the center of each conical-wire array. When plasmas merged at the center of the conical-wire array, a plasma jet was generated. In other words, two counter-streaming plasma jets were generated. When two plasma jets collided with each other at the center of the bi-conical-wire array, a stagnated plasma was formed. Time-resolved Shadowgraph, Schlieren, and Interference images of the process were taken using a 5-ns Q-switch laser in 532 nm as the backlighter. Therefore, the density and the size of the stagnated plasma were obtained. Images showed that the plasma started stagnating at the center of the bi-conical-wire array ~600 ns after the current started and reached ~1016 cm-3 in density.
Poster
Language
演講語言 (Language): in English