Plasma Physics Seminar

ProfessorThomas Pedersen Columbia University "Confinement of non-neutral and electron-positron plasmas in the CNT stellarator" The confinement of non-neutral plasmas on magnetic surfaces is a relatively unexplored area of plasma physics. The equilibrium of a pure electron plasma on magnetic surfaces is fundamentally different from that of  a pure electron plasma confined in a Penning trap, and fundamentally different from that  of a quasi-neutral plasma confined on magnetic surfaces. The confinement time is predicted to be very long for such plasmas, as long as the Debye length is small compared to the minor radius. The Columbia Non-neutral Torus (CNT) is a small, ultralow aspect ratio stellarator being constructed at Columbia University specifically to study non-neutral and electron-positron plasmas on magnetic surfaces. CNT will explore the physics not only of pure electron plasmas, but also partly neutralized plasmas, including helium plasmas with an electron surplus, and electron-positron plasmas. The former are of interest to fusion science, allowing a study of electron-ion plasmas in the extreme ion root. The latter are of importance to basic plasma physics due to the perfect symmetry between the electron and positron. We will present an overview of the physics issues being addressed in the CNT device, and give an update on the construction of CNT.