Orbit injection dump simulations of the H0 and H- Beams

Simulations of the transport of H⁰ and H^- beams to the spallation neutron source (SNS) ring injection dump are carried out using the ORBIT code. During commissioning and early operations, beam losses in this region have been the highest in the accelerator and have presented the most obvious hurdle to cross in achieving high intensity operation. Two tracking models are employed: 1) a piecewise continuous symplectic representation of the lattice elements in the injection chicane and dump line, and 2) particle tracking in full 3D magnetic fields, as obtained from OPERA code evaluations. The physics models also include estimations of scattering from both the primary and secondary stripper foils, and beam losses due to apertures throughout the beam line.

Introduction

To reach its specified operating parameters, SNS must achieve unprecedented low uncontrolled losses of one part in . Thus far, the most severe losses are observed in the vicinity of the ring injection dump. The SNS ring injection system (Fig. 1) utilizes a stripper foil to convert a 1 GeV linac beam to a circulating beam in the accumulator ring. The injection dump was designed [1] to collect beam that misses the stripper foil and also incompletely stripped beam. There is an insertion in the ring, the injection chicane [2], which was designed to accommodate the merging of the injected and circulating beams and to deliver the incompletely stripped beams to the dump. The chicane consists of four dipole magnets, primary and secondary stripper foils, and four horizontal and four vertical kickers. The second stripper foil, located before the fourth chicane dipole, converts the and waste beam components to for delivery to the dump, while the kickers are programmed with time-dependent waveforms to paint the circulating beam distribution. In addition to these components there is an injection septum dipole to steer the linac beam upstream of the primary foil and a combined function dump septum to steer and focus the waste beams at the beginning of the dump line.