Physics & Astronomy Space Plasma Seminar - Dr. Umair Siddiqui, W. Virginia Uni.

Title: "Investigations of Electric Fields in Laboratory Plasmas"

October 13, 2015
3:30 pm - 4:30 pm
Location
Wilder 111
Sponsored by
Physics & Astronomy Department
Audience
Public
More information
Tressena Manning
603-646-2854

Abstract:  Despite plasmas being comprised of mobile charged particles capable of responding to electromagnetic forces, steady-state electric fields arise in a variety of situations. These potential gradients are purported to drive a host of physical phenomena, such as auroral, solar wind, and reconnection outflow particle acceleration. Electric fields also form near particle-absorbing boundaries in plasmas, which accelerate ions towards the surfaces causing sputtering and wall erosion – a major issue for the next generation of fusion experiments. Here we present several investigations of freestanding “double layer” electric fields, and “presheath” electric fields near absorbing objects. Double layers are measured at the interfaces of hot and cold plasmas, as well as in regions of geometric plasma expansion. Ion flows in presheaths are measured in systems where strong magnetic fields obliquely intersect the boundary. Canonical models for such flows are shown to be inaccurate. The results of the presented experiments are compared to observations in space plasmas, and are applied to anomalous wall erosion results in Hall thrusters and in divertor tokamaks.

Location
Wilder 111
Sponsored by
Physics & Astronomy Department
Audience
Public
More information
Tressena Manning
603-646-2854