Space-Charge and resonance considerations for choosing the SNS ring working points

The beam power of the SNS is an order of magnitude higher than that of existing accelerator facilities. This imposes a strict requirement on the uncontrolled beam loss at a $10^{-4}$ level. The major source of beam loss is associated with machine resonances. Thus, the first step towards reaching low beam loss is to find the best suitable working points on the tune diagram. In this note, we explore the tune space by considering machine resonances and the effect of space charge, which can drive particles into these excited resonances.In addition, space charge itself can induce resonances. Our present studies were driven by these facts and by the fact that previous working points [1] were identified for the shorter ring with 220 m circumference. Also, the combined effects of space charge and magnet errors raised concern for the nominal working point [2-3].