Plasma Physics Seminar ( Phys 769)

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
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.