Investigation of the Surface Resistivity Tolerance of the Kicker Ceramic Vacuum Chamber at Aps*

The conductive coating on kicker ceramic vacuum chambers was found to affect the pulse width, amplitude, and phase of the kicker magnetic field. Differences in the surface resistivity between the chambers caused each kicker magnetic field to have a slightly different pulse shape, resulting in unwanted betatron oscillations of the stored beam during injection into the storage ring at the Advanced Photon Source. Orbit oscillations were measured with the present kicker mismatch and optimized for a closed bump. Tracking simulations of the closed bump provided an idealized tolerance for the variation of chamber surface resistivity consistent with minimizing the betatron oscillations. The pulse shape of the kicker current was dependent on the current level and the coupling between the kicker magnet and chamber. Local magnetic fields in two prototype kicker chambers were measured and compared with eddy current calculations.