Measurement of Electron Trapping in the CESR Storage Ring

Abstract

The buildup of low-energy electrons has been shown to affect the performance of a wide variety of particle accelerators. Of particular concern is the persistence of the cloud between beam bunch passages, which can impose limitations on the stability of operation at high beam current. We have obtained measurements of long-lived electron clouds trapped in the field of a quadrupole magnet in a positron storage ring, with lifetimes much longer than the revolution period. Based on modeling, we estimate that about 7% of the electrons in the cloud generated by a 20-bunch train of 5.3 GeV positrons with 16-ns spacing and $1.3x10^{11}$ population survive longer than 2.3 $\mu$s in a quadrupole field of gradient 7.4 T/m. We have observed a non-monotonic dependence of the trapping effect on the bunch spacing. The effect of a witness bunch on the measured signal provides direct evidence for the existence of trapped electrons. The witness bunch is also observed to clear the cloud, demonstrating its effectiveness as a mitigation technique.

6 pages, 9 figures, 28 citations

References in corpus (4)

• Comparison of Electron Cloud Mitigating Coatings Using Retarding Field Analyzers
• Investigation into electron cloud effects in the International Linear Collider positron damping ring
• Measurement and Modeling of Electron Cloud in a Field Free Environment Using Retarding Field Analyzers
• Shielded button electrodes for time-resolved measurements of electron cloud buildup

Cited by in corpus (4)

• The Conversion of CESR to Operate as the Test Accelerator, CesrTA, Part 1: Overview
• Fast Instability Caused by Electron Cloud in Combined Function Magnets
• Instrumentation for the Study of Low Emittance Tuning and Beam Dynamics at CESR
• Measurement and modeling of electron-cloud-induced betatron tune shifts at the Cornell Electron-positron Storage Ring test accelerator