CMOS Based Beam Loss Monitor at the SLS

For several years, the SLS storage ring was not equipped with loss monitors to observe loss patterns around the storage ring; hence, any understanding of the operational losses, accidental losses, or manual beam dumps was missing. Initially, a long quartz fibre (350 m) was installed around the ring to locate losses, and read out with a photomultiplier tube. With the long fibre, we garnered some understanding yet, it was not easy to locate the position of the losses. Hence, we opted for scintillator based fibre loss monitors, installed in choice locations. All the fibres are read out together with a single CMOS based 2.3 MP camera. A device was built with 28 channels. Ten fibres were connected and are located in the injection kicker in the BTRL and three arcs of the storage ring. With these loss monitors, we were able to detect and locate the position of losses due to injection and sudden beam dumps/losses. In this paper, we will introduce the concept and the components of this monitor, and present the data processing algorithm that identifies the individual fibres in the images, allowing us to locate and track the losses in the SLS storage ring.