Reduction of Surface Flashover of the Beam Screen of the LHC Injection Kickers

The LHC injection kicker magnets include beam screens to shield the ferrite yokes against wake fields resulting from the high intensity beam. The screening is provided by conductors lodged in the inner wall of a ceramic support tube. Operation with increasingly higher bunch intensity, and narrow bunches, now requires improved ferrite screening. This will be implemented by additional conductors; however the good high-voltage behaviour of the kicker magnets must not be compromised by the supplementary screening. Extensive studies and optimisations have been carried out, to better satisfy the often conflicting requirements for low beam coupling impedance, fast magnetic field rise-time, high vacuum and good high voltage behaviour. A new configuration is proposed which reduces significantly the electric field associated with the screen conductors and the secondary electron yield of the surface of the ceramic tube. Results of high voltage test results are also presented.