Lattice for a 1.1-GeV 500-μ A fast cycling proton synchrotron

A very high intensity proton synchrotron lattice has been designed for a spallation neutron source system. The synchrotron is to accelerate a beam of 6.25 × 10¹³ protons from 200 MeV to 1100 MeV in 15 msec. A detailed discussion on the synchrotron is described elsewhere. The proposed lattice is in modular form of storage ring type consisting of normal cells, dispersion suppressor cells and matching and straight section cells. Due to the fast repetition rate, the maximum required energy gains per turn is approximately 100 KeV, and this in turn needs approximately 20 meters or more of straight sections for the acceleration cavities. Such spaces for the cavities are to be provided by the insertion straight section. One of the important concerns for high intensity, high rep rate (50 pulses/sec) machine is stability of the beam. Considerations of the transverse space charge limits and the transverse stability criterion favor a high tune machine over a low tune machine of the same circumference. This high tune concept makes the average beta function throughout the lattice smaller and at the same time the momentum dispersion function smaller compared to a low tune machine. The smaller dispersion functions enables operation of the machine with a larger momentum bite, and a large momentum spread to alleviate the longitudinal instability. For these reasons, we made the tune as high as possible by making the cell length as short as possible.