  A beam loss in the superconducting part of the SNS linac has been observed
during its commissioning and operation. Although the loss does not prevent the
SNS high power operation, it results in an almost uniform irradiation of linac
components and increased radiation levels in the tunnel. Multi-particle
tracking could neither account for the magnitude of the observed loss nor its
dependence on machine parameters. It was recently found that the loss is
consistent with the intrabeam particle collisions resulting in stripping of H-
ions. The paper describes experimental observations and corresponding
analytical estimates of the intrabeam stripping.
