Stability Regimes in a Rotating Quadrupole Focusing Accelerator
Abstract
A number of high current accelerator designs utilize strong focusing in the form of helical quadrupole and axial guide fields. We obtain a linear dispersion relation for an electron beam propagating in a cylindrical waveguide subject to helical quadrupole and longitudinal magnetic fields, electromagnetic waveguide modes and image fields. The electromagnetic waveguide modes are expressed in terms of right-hand and left-hand circularly polarized waves. We find that the electron beam centroid, depending on the system parameters, can be (1) orbit unstable independent of the waveguide modes, (2) three-wave unstable or (3) fully stable. Analytic expressions for the various stability conditions are obtained in the limit of zero beam current, where the right-hand and left-hand circularly polarized waves decouple. Algebraic expressions for the growth rate in each of the three-wave unstable regimes are presented. The full dispersion relation is solved numerically with results that are in good agreement with both the stability conditions and the growth rate expressions. (kr)
Document Details
- Document Type
- Technical Report
- Publication Date
- Mar 07, 1990
- Accession Number
- ADA219513
Entities
People
- Chai AMei Tang
- F. Mako
- Jonathan F. Krall
- P. Serafim
- Phillip A. Sprangle
Organizations
- United States Naval Research Laboratory