TE Wave Measurement and Modeling

TL;DR

This paper reviews TE wave measurement techniques for electron cloud density, emphasizing the resonant cavity analysis, and presents experimental and simulation results from CESRTA and DAΦNE.

Contribution

It advocates for the resonant TE wave analysis method and demonstrates its application with experimental and simulation data from multiple facilities.

Findings

Resonant TE wave analysis provides detailed electron cloud measurements.

Bench measurements reveal standing wave patterns and cutoff modes.

Simulations show microwave resonances in electron cloud and magnetic field environments.

Abstract

In the TE wave method, microwaves are coupled into the beam-pipe and the effect of the electron cloud on these microwaves is measured. An electron cloud (EC) density can then be calculated from this measurement. There are two analysis methods currently in use. The first treats the microwaves as being transmitted from one point to another in the accelerator. The second more recent method, treats the beam-pipe as a resonant cavity. This paper will summarize the reasons for adopting the resonant TE wave analysis as well as give examples from CESRTA and DA{\Phi}NE of resonant beam-pipe. The results of bead-pull bench measurements will show some possible standing wave patterns, including a cutoff mode (evanescent) where the field decreases exponentially with distance from the drive point. We will outline other recent developments in the TE wave method including VORPAL simulations of microwave resonances, as well as the simulation of transmission in the presence of both an electron cloud and magnetic fields.