TE Wave Measurement and Modeling

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 DAΦNE 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.

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

“…For this measurement, the microwaves are coupled in and out of the beam-pipe at the same longitudinal position using electrodes within this section that are normally connected to the beam position monitor (BPM) system. When the beam-pipe has a resonant response, the analysis to determine the EC density within it needs to be based on the response of these resonances to changes in EC density [10][11][12]. This paper describes a variation on the microwave transmission method that is based on techniques for plasma density measurement using resonant cavities.…”