Simulation and analysis of TE wave propagation for measurement of electron cloud densities in particle accelerators

Abstract

The use of transverse electric (TE) waves has proved to be a powerful, noninvasive method for estimating the densities of electron clouds formed in particle accelerators. Results from the plasma simulation program VSim have served as a useful guide for experimental studies related to this method, which have been performed at various accelerator facilities. This paper provides results of the simulation and modeling work done in conjunction with experimental efforts carried out at the Cornell electron storage ring "Test Accelerator" (CesrTA). This paper begins with a discussion of the phase shift induced by electron clouds in the transmission of RF waves, followed by the effect of reflections along the beam pipe, simulation of the resonant standing wave frequency shifts and finally the effects of external magnetic fields, namely dipoles and wigglers. A derivation of the dispersion relationship of wave propagation for arbitrary geometries in field free regions with a cold, uniform cloud density is also provided.

Electron cloud density measurements in accelerator beam-pipe using resonant microwave excitation

“…4, where the local EC density n e can be a function of time and of the position within the resonator. This expression and simulations of electron cloud in resonant beam-pipe are in good agreement [16].…”

Time Resolved Measurement of Electron Cloud Densities from Dispersion of Transverse Electric Pulses

“…The dispersion relation for a waveguide filled with a dielectric medium is well known. For an electron cloud in a region free of external magnetic fields, the dispersion relationships have been worked out in Refs [5], [6]. It is also shown that the relationship between δk and the electron density is linear for frequencies that are not too close to the waveguide cutoff frequencies.…”