Energy-Loss Extraction System with Thin-Septum Plunged Magnet at Nimrod

Details are given of a system involving an energy-loss target, a plunged 1 cm septum magnet and correction of the Nimrod field by radially focusing elements where the beam emerges. These elements are energised partly from Nimrod fringe flux and partly from powered windings. The applied current has to be programmed with the magnet pulse to minimise disturbance of the accelerator field. Design work has so far been done with the program TRIM, solving sections of the configuration at various azimuths as two-dimensional problems. The lip and targetting program LIMP has been used to generate "realistic" assemblies of, typically, 100 particles, which are then tracked through the extraction system using the program NIMDYN. A tagging facility enables particle identity to be retained through to the final statistics on assemblies of 100 particles or less.