Study of Cryogenic Complex Plasma

Abstract

Abstract : Overall goal is to study basic physics of a complex plasma at a room temperature as well as in a cryogenic environment and to reveal novel natures of a cryogenic complex plasma produced by a stable discharge above or in super fluid liquid helium . This final report describes research on Complex plasma, also known as dusty plasma and plasma with micron-sized dust particles in which charged dust particles interact with background plasma. A system with dust particles is characterized by low frequency oscillations, 1 to 10 Hz, and a system with plasma particles is characterized by high frequency oscillations, 0.1 to 10GHz. The interaction between two distinct systems produces novel features. Basic features of complex plasma at a room temperature have been studied by a device YCOPEX, while cryogenic complex plasma has been studied by YD-1 and YD-2. Researchers have produced discharge plasma in the vapor of liquid helium in the device YD-2 and in the helium gas cooled by liquid helium in the device YD-1. In YD-1, cryogenic RF plasma is produced in a helium gas in a glass tube surrounded by cryogenic liquid (liquid nitrogen or liquid helium) and dust particles are introduced in the plasma. In YD-2, a cryogenic plasma is produced in the vapor of liquid helium above the super fluid liquid helium. Stable complex plasma in a cryogenic environment has been produced successfully in YD-1 as well as in YD-2. A linear device YCOPEX (Yokohama Complex Plasma Experiment, installed in the summer, of 2006) has been used to study the fundamental physics of room temperature complex plasma. Theoretical study on Coulomb clusters by dust particles revealed the CME (configuration of minimum energy) structures for elongated plasma confinement. Theoretical and simulation study on cryogenic complex plasma has revealed the diffusion process of charged dust particles produced in the vapor of liquid helium toward the surface of liquid helium.