Impact of Ion Clearing Electrodes on Beam Dynamics in DAFNE

TL;DR

This paper investigates how ion clearing electrodes affect beam dynamics in DAFNE, revealing their impedance contributions and demonstrating that removing them improves collider performance and luminosity.

Contribution

It provides the first detailed analysis of ICE impact on DAFNE beam dynamics, including wake field calculations and experimental validation, and shows benefits of electrode removal.

Findings

ICE contribute significantly to machine impedance

Removing ICE improves beam stability and luminosity

Experimental data confirms theoretical impedance estimates

Abstract

Presently clearing electrodes are being considered as a possible cure of e-cloud driven problems in existing and future colliders. 'Invisible' electrodes, made of a thin highly resistive layer pasted on a dielectric plate, have been proposed as one of design solutions for the e-cloud clearing. For the first time such electrodes were successfully used in the electron-positron accumulator (EPA) of LEP. Similar electrodes had been using for a long time for ion clearing purposes in the DAFNE electron ring. Theoretical considerations and experimental measurements at DAFNE have revealed a substantial contribution of the ion clearing electrodes (ICE) to the machine broad-band impedance giving rise to several harmful effects degrading the collider performance. In this paper we discuss the impact of the electrodes on DAFNE beam dynamics, show the results of ICE wake field and impedance calculations and compare them with available experimental data. We also describe the procedure of ICE removal from the wiggler sections of the electron ring that has resulted in remarkable improvements in terms of beam dynamics and geometric luminosity.