Secondary electron yield and groove chamber tests in PEP-II

Abstract

Possible remedies for the electron cloud in positron damping ring (DR) of the International Linear Collider (ILC) includes thin-film coatings, surface conditioning, photon antechamber, clearing electrodes and chamber with grooves or slots [1]. We installed chambers in the PEP-II Low Energy Ring (LER) to monitor the secondary electron yield (SEY) of TiN, TiZrV (NEG) and technical accelerator materials under the effect of electron and photon conditioning in situ. We have also installed chambers with rectangular grooves in straight sections to test this possible mitigation technique. In this paper, we describe the ILC R&D ongoing effort at SLAC to reduce the electron cloud effect in the damping ring, the chambers installation in the PEP-II and latest results.

Investigation into electron cloud effects in the International Linear Collider positron damping ring

“…Measurements of the reduction in secondary yield afforded by such grooves have been performed at PEP-II [23,24]. More recently, measurements of the reduction of cloud buildup in a grooved aluminum vacuum chamber relative to that for a smooth chamber surface in the CESR positron storage ring showed an improvement by more than a factor of two, corresponding to a decrease in the peak SEY value from 2.0 to 1.2 [25].…”

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

“…In particular, wiggler vacuum chambers with a range of mitigations applied have been produced in collaboration with our KEK, LBNL, and SLAC colleagues. After the conclusion of the BaBar/PEP-II B-physics program, the EC hardware that had been deployed in the positron low energy ring (LER) of PEP-II [26,27] was transferred to CESR to continue the studies that had not yet been completed at PEP-II. Finally, vacuum chambers with various low SEY coatings have been prepared in collaboration with our colleagues at CERN, KEK, LBNL and SLAC.…”

Final Report for "Modeling Electron Cloud Diagnostics for High-Intensity Proton Accelerators"

“…In this task we simulated the transmission of both TE and TM modes though uniform, cold electron clouds while applying external magnetic fields in various directions. An applied dipole in the transverse direction has been used to measure the cyclotron resonance [5] and we undertook simulations to understand this effect. Applied solenoidal magnetic fields, in the propagation direction, are a strong candidate for mitigation of electron cloud effects if they can be shown to confine secondary electrons near the beam pipe walls instead of getting into the path of the beam.…”