Use of a first-harmonic RF system in the NSLS booster

In order to capture and accelerate the maximum amount of beam injected into the booster from the linac and to put all of this beam into one bucket of the VUV or the X-Ray Ring, several scenarios involving a first-harmonic RF system can be considered: (a) accelerate with 5 full buckets (with the present 5th harmonic system) and coalesce the 5 bunches into one 1st harmonic bucket at flat-top, or possibly before flat top; (b) accelerate with a first harmonic (10.57 MHz) system all the way; or (c) accelerate with a first harmonic until the bunch has damped sufficiently to transfer to one of the fifth-harmonic buckets (suggested by Galayda to ease the voltage requirements on the first harmonic system). The capture efficiency at injection should be independent of the harmonic number of the RF system, unless there are deleterious beam-cavity interactions, in which case the first-harmonic system using ferrite could have an advantage because of its lossy characteristics at high frequencies. The acceleration efficiency should also be independent of harmonic number except at high beam intensities where collective instabilities can occur. In this domain the system with lower peak beam current would be favored. As will be seen, this consideration favors the fifth-harmonic acceleration system