Ishii, H. Adachi, J. Kosuge, T. Tanaka, H. JACoW Publishing Geneva, Switzerland 978-3-95450-207-3 10.18429/JACoW-MEDSI2018-THPH23 English 385-387 THPH23 controls PLC GUI software operation Contribution to a conference proceedings 2018 2018-12 https://doi.org/10.18429/JACoW-MEDSI2018-THPH23 http://jacow.org/medsi2018/papers/thph23.pdf A hybrid operation mode that enables beam time sharing between single-bunch users and multi-bunch users has been introduced in the PF 2.5GeV ring of KEK (High Energy Accelerator Research Organization). A pulse selector, a kind of optical chopper, is used to permit the passage only of an X-ray pulse that comes from a single bunch part of the hybrid filling pattern. We have developed a new pulse selector with a magnetic bearing. It comprises a rotating dish-shaped disk, a phase-lock-loop (PLL) controlled motor system, and other parts . The speed and phase of the rotating disk is controlled by TTL signals obtained by dividing the RF signal of the PF 2.5 GeV ring. A commercially available motor driver was designed for lower loading. The rotating disk for the pulse selector is heavier than those disks used previously in which air bearings are used. A rapid deceleration of the rotation causes problems through a large current flow back to the motor driver. In this study, we describe the prototype of a programmable logic controller based on an interlock system to avoid the current flow back problem in the pulse selector.