Experimental study of new laser-based alignment system at the KEK B-factory injector linear accelerator

A new laser-based alignment system for the precise alignment of accelerator components along an ideal straight line at the KEK B-factory injector linear accelerator (linac) is under development. This system is strongly required in the next generation of B-factories for the stable acceleration of high-brightness electron and positron beams with high bunch charges and also for maintaining the stability of injection beams with high quality. A new laser optics for the generation of a so-called Airy beam has been developed for the laser-based alignment system. The laser propagation characteristics both in vacuum and at atmospheric pressure have been systematically investigated in an 82-m-long straight section of the injector linac. The laser-based alignment measurements based on the new laser optics have been carried out with a measurement resolution of ±0.1 mm level by using an existing laser detection electronics. The horizontal and vertical displacements from a reference laser line measured using this system are in good agreement with those measured using a standard telescope-based optical alignment technique. In this report, we describe the experimental study in detail along with the basic designs and the recent developments in the new laser-based alignment system.