Transient beam loading reduction during multi-batch coalescing in the Fermilab main ring

Abstract

Increasing the number of proton bunches in the Tevatron Collider from 6 to 36 places new demands on the bunch coalescing process in the Main Ring. As many as 132 proton bunches may have to be simultaneously coalesced into 12 high-intensity bunches before being injected into the Tevatron. In order to efficiently produce these high-intensity bunches, the total Main Ring RF cavity fundamental voltage at h=113 must first be adiabatically reduced to below a few kilovolts. Under these conditions, with many proton bunches filling a fraction of the Main Ring, the transient beam loading voltage generated in the cavities can exceed this value by an order of magnitude. A method of reducing this transient loading by temporarily shorting 16 of the 18 RF cavities is described, along with data illustrating the transient voltage reduction. >