LOCO CORRECTIONS FOR BEAM TRAJECTORY OPTIMISATION ON THE ISIS ACCELERATOR

The ISIS facility at the Rutherford Appleton Laboratory, UK, produces neutron and muon beams for condensed matter research. Its 50 Hz, 800 MeV proton synchrotron delivers a mean beam power of 0.2 MW to two tungsten spallation targets. The beam optics correction technique implemented in this work is Linear Optics from Closed Orbits (LOCO). LOCO modifies existing accelerator models according to a measured orbit-response matrix (ORM). This correction technique identifies imperfections in the machine lattice, and discrepancies between the machine and model. The identification of erroneous elements through analysis of the measured ORM is demonstrated in this paper. In comparison to the operational settings achieved through the existing correction techniques, the initial test of the LOCO code demonstrates a 17 % improvement to the RMS trajectory deviation in the horizontal plane. It also shows an 11 % horizontal and 30 % vertical decrease to the standard deviation of trajectory measurements.