The use of crystals in particle accelerators allows 

Inside a crystal the atoms occupy precise positions in space: the interaction with a particle beam produces a wide range of coherent interaction phenomena which can be used to deflect particle beams, to generate x-rays and gamma-rays, innovative positron sources and ultra-compact detector to be used in physics and astrophysics experiments. A special case is the collimation of the ion beam circulating in LHC. In this case a suitably shaped silicon crystal can effectively replace the collimators typically used to preserve the superconducting magnets of the accelerator.