Characterization of electron clouds in the Cornell Electron Storage Ring Test Accelerator usingTE-wave transmission

Abstract

A relatively new technique for measuring the electron cloud density in storage rings has been developed and successfully demonstrated [S. De Santis, J. M. Byrd, F. Caspers, A. Krasnykh, T. Kroyer, M. T. F. Pivi, and K. G. Sonnad, Phys. Rev. Lett. 100, 094801 (2008).]. We present the experimental results of a systematic application of this technique at the Cornell Electron Storage Ring Test Accelerator. The technique is based on the phase modulation of the TE mode transmitted in a synchrotron beam pipe caused by the periodic variation of the density of electron plasma. Because of the relatively simple hardware requirements, this method has become increasingly popular and has been since successfully implemented in several machines. While the principles of this technique are straightforward, quantitative derivation of the electron cloud density from the measurement requires consideration of several effects, which we address in detail.

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

“…Due to the presence of several mechanical and electronic components all along the vacuum chamber, it is not very likely that one can perform phase shift experiments that are entirely free of internal reflections. As discussed in Ref [14], in an experiment, these internal reflections would potentially affect the value of the phase shift. A wave reflected from a device that lies beyond the segment being measured, would be received by the detector when it comes back after reflection.…”

The conversion of CESR to operate as the Test Accelerator, CesrTA. Part 3: electron cloud diagnostics

“…The analysis of the propagation of electromagnetic waves excited within the accelerator's beam pipe has recently emerged as a powerful method for the study of the electron cloud (EC) density [14][15][16][17]. Since this technique does not require the installation of any new hardware inside the vacuum chamber, it was possible to employ this method for different sections of CESR.…”

CESR Conversion Damping Ring Studies of Electron Cloud Instabilities (CESR-TA)

“…In addition to the RFA studies, TE Wave transmission methods [28] are being used to characterize the build-up around the ring and a simulation effort is underway to take full advantage of these results [29][30][31]. A final method to study local EC build-up is shielded pickup measurements [32], which provide additional constraints on the vacuum chamber surface parameters for the chambers in which they're installed.…”