Velocity measurements of plasma jets generated by conical-wire arrays driven by a 1-kJ pulsed-power system

Po-Yu Chang^1*, Yen-Cheng Lin¹, Ming-Hsiang Kuo¹, Cheng-Han Du¹, Ming-Cheng Jheng^2,1, Chih-Jui Hsieh¹, Jia-Kai Liu¹

¹Institute of Space and Plasma Sciences, National Cheng Kung University, Tainan, Taiwan
²Affiliation: National Synchrotron Radiation Research Center, Hsinchu, Taiwan

* Presenter:Po-Yu Chang, email:pchang@mail.ncku.edu.tw

We are studying plasma jets generated by conical-wire arrays driven by the pulsed-power system. In particular, the velocity of the plasma jets was measured. The plasma jet will be used to study the supersonic plasma flows, such as solar winds and plasma jets in Herbig-Haro (HH) objects, in the laboratory environment. The 1-kJ pulsed-power system, the Pulsed-power Generator for Space science (PGS) machine, is capable of providing a pulsed current with a peak current of 135±1 kA and a rise time of 1592±3 ns. The current is used to drive the 13.9-mm conical-wire array consisting of four 20-μm tungsten wires. The diameters of the conical-wire array at the cathode side and the anode side are 5 mm, and 21 mm, respectively, i.e., an inclination angle of 30°. The plasma jet is generated when the heated and ionized plasma from the wire merges at the center of the conical-wire array due to the nonuniform z-pinch effect. A Q-switch Nd:Yag laser with a wavelength of 532 nm is used as the backlighter for taking time-resolved shadowgraph and Schlieren images with a temporal resolution in the order of nanoseconds. From measuring the length of the plasma jet in the Schlieren images at different times, the speed of the plasma jet, 170±70 km/sec, was obtained. Therefore, the estimated velocity of ablated plasma from the tungsten wires was 50±20 km/s. Thus, how two plasma jets interact with each other will be studied in the near future.

Keywords: Pulsed-power system, Plasma jet, Conical-wire array, Schlieren image, Laboratory astrophysics and space sciences