Radiation Heating from Beam Loss on ISABELLE Ejection Septa

It is anticipated that radiation heating due to beam loss may place severe constraints on the operation of high energy accelerators which utilize superconducting magnets. Losses on ejection septa, assuming an unbunched beam mode of operation, are unavoidable and have direct impact on the design of the extraction system. Calculations of energy deposition densities downstream of ISABELLE ejection septa have been made using a modified version of the hadron cascade Monte Carlo computer program CASIM. The results of these calculations are described, giving emphasis to understanding the physical processes which dominate the energy deposition as a function of lattice geometry, which may include the presence of collimators. It is found that fast forward protons are particularly troublesome, since they are focused by the lattice until a dispersive element is reached. At 400 GeV/c, these leading particles produce an energy density of ~ 5 × 10-5 GeV/(cm3p) in the coils of ISABELLE dipoles, which implies that septum losses be less than 0.1% of the circulating beam if quenches are to be avoided.