Review of electron beam macroinstabilities and other EBIS related stability and issues

Abstract

Plasma magnetohydrodynamics and macro-instability theories are briefly reviewed.Although the configuration of any EBIS is inherently susceptible to a number of classical beam instabilities, the small radial dimension of an EBIS plasma prevents modes from occurring in EBIS traps with low beam compression due to physical limitation. In EBIS devices with high electron beam compression, where the potential for beam instabilities is great, the radial dimension is smaller than the Debye length, which renders any plasma theory invalid. However, a RHIC EBIS is expected to have a diameter which is much larger than the Debye length. Hence, it may be the first EBIS, in which the various plasma theories could be valid. For this and future devices like it, a framework is established to analyze and offer remedies plasma instabilities in EBIS.

Eliminating unwanted electrons in EBIS devices

“…Total cross section σ e,i for such interaction with gold atoms 11 (it's most likely higher with ions) is 10 -15 cm 2 . Therefore, the collision frequency with gold ions is at least f c = 3.4x10 5 Hz. But, the collision frequency increases a Z 2 , where is Z the ion charge state.…”

“…A variety of microinstabilities due to axial positive slope gradients in configuration and velocity space are also possible 4,5 . Stripped electrons can accumulate in the positively biased gates and facilitate these instabilities 6 by providing a source of free energy.…”

Plasma Micro-Stability Analysis for the RHIC Electron Beam Cooler

“…Harris derived this equation to ease micro-stability analysis in magnetic mirror device 5 , whose diameter to length ratio is of order unity. Hershcovitch modified that equation and adapted it to cylindrically shaped plasma systems 6,7,8,9 (gated electron traps, and EBIS devices) that are characterized by large lengths and tiny diameters. In particular, EBIS bares an additional similarity to PRF RHIC E-Cool bunches with its different lengths of electron and ion columns.…”

“…In particular, EBIS bares an additional similarity to PRF RHIC E-Cool bunches with its different lengths of electron and ion columns. The most suitable dispersion relation 9 for our system is…”