Simulation of main plasma parameters of a cylindrical asymmetric capacitively coupled plasma micro-thruster using computational fluid dynamics

Computational fluid dynamics (CFD) simulations of a radio-frequency (13.56 MHz) electrothermal capacitively coupled plasma (CCP) micro-thruster have been performed using the commercial CFD-ACE+ package. Standard operating conditions of a 10W, 1.5 Torr argon discharge were used to compare with previously obtained experimental results for validation. Results show that the driving force behind plasma production within the thruster is ion-induced secondary electrons ejected from the surface of the discharge tube, accelerated through the sheath to electron temperatures up to 33.5 eV. The secondary electron coefficient was varied to determine the effect on the discharge, with results showing that full breakdown of the discharge did not occur for coefficients less than or equal to 0.01

Density Measurements in Low Pressure, Weakly Magnetized, RF Plasmas: Experimental Verification of the Sheath Expansion Effect

This experimental study shows the validity of Sheridan's method in determining plasma density in low pressure, weakly magnetized, RF plasmas using ion saturation current data measured by a planar Langmuir probe. The ion density derived from Sheridan's method which takes into account the sheath expansion around the negatively biased probe tip, presents a good consistency with the electron density measured by a cylindrical RF-compensated Langmuir probe using the Druyvesteyn theory. The ion density obtained from the simplified method which neglects the sheath expansion effect, overestimates the true density magnitude, e.g., by a factor of 3 to 12 for the present experiment

THE CURRENT-FREE ELECTRIC DOUBLE LAYER IN A CORONAL MAGNETIC FUNNEL

Current-free double layers (CFDLs) have been recently discovered in a number of laboratory devices, when a low collisional plasma is forced to expand from a high magnetic field source region to a low magnetic field diffusion region. This experimental setup bears a striking resemblance to the natural conditions prevailing in the magnetic funnels of the solar corona. It was commonly thought that magnetic-field-aligned potential disruptions were driven by electron currents, although the theoretical possibility of a CDFL has been known of for some time. Given its recent experimental verification, we make here a contribution to solar plasma physics by investigating the possibility of CFDLs in coronal funnels, which have much in common with the laboratory experiments. Therefore, CFDLs may play an important role in supplying and accelerating plasma in coronal funnels. Subject headings: acceleration of particles — magnetic fields — plasmas — Sun: corona — Sun: transition region Online material: color figur

Transitions from electrostatic to electromagnetic whistler wave excitation

The transition and excitation phenomena of electromagnetic whistler wave was investigated. The refractive index was anisotropic and exhibited resonances at certain angles caused by electron inertia at frequencies below electron cyclotron and above hybri

How plasma induced oxidation, oxygenation, and de-oxygenation influences viability of skin cells

The effect of oxidation, oxygenation, and de-oxygenation arising from He gas jet and He plasma jet treatments on the viability of skin cells cultured in vitro has been investigated. He gas jet treatment de-oxygenated cell culture medium in a process referred to as "sparging." He plasma jet treatments oxidized, as well as oxygenated or de-oxygenated cell culture medium depending on the dissolved oxygen concentration at the time of treatment. He gas and plasma jets were shown to have beneficial or deleterious effects on skin cells depending on the concentration of dissolved oxygen and other oxidative molecules at the time of treatment. Different combinations of treatments with He gas and plasma jets can be used to modulate the concentrations of dissolved oxygen and other oxidative molecules to influence cell viability. This study highlights the importance of a priori knowledge of the concentration of dissolved oxygen at the time of plasma jet treatment, given the potential for significant impact on the biological or medical outcome. Monitoring and controlling the dynamic changes in dissolved oxygen is essential in order to develop effective strategies for the use of cold atmospheric plasma jets in biology and medicine