Global optimization of an entire neutron guide hall

This paper describes the optimization of an entire neutron guide system, from the moderator to the sample position for several instruments simultaneously, using no more than a desktop computer and a few days of CPU time. This is made possible by merging two relatively advanced computational techniques. Neutron acceptance diagram shading is a fast new method for modelling neutron beams, using an approach based on polygons similar to those featuring in computer games. Optimization algorithms based on swarm intelligence are efficient and reliable ways to maximize numerically calculable figures of merit with many strongly coupled geometry parameters. Recent developments in these methods are described, as well as their combination to optimize the geometry of the H5 beamlines at the Institut Laue-Langevin. The optimization was such that all instruments simultaneously gain as much on-sample flux as possible by taking unused phase space from their neighbours, whilst no instrument suffers any losses in its useful flux.