Experimental Measurements of e-Cloud Mitigation Using Clearing Electrodes in the DAФNE Collider

Recently the DAФNE electron-positron collider has started delivering luminosity to the KLOE-2 experiment. For this run special metallic electrodes were installed in all the dipole and wiggler magnets of the positron ring to cope with the effects induced by the e-cloud formation. Experimental measurements have shown an impressive effectiveness of these devices in mitigating the e-cloud impact on the positron beam dynamics. The electrodes allow reducing the vertical beam size and the growth rate of transverse instabilities as well as the tune shifts induced by the electron cloud itself. Moreover frequency shift measurements of the vacuum chamber resonances, switching on and off the electrodes, indicate an evident reduction of the electron cloud density. This paper reports and analyses all the experimental observations and measurements done to suppress the e-cloud induced effects by using metallic electrodes.