The positional relationship between eBPM in the storage ring, XBPM in the frontend and DBPM in the beamline

Abstract The Taiwan Photon Source (TPS) employs various types of beam position monitors (BPMs) to ensure beam stability and provide feedback during routine operations. These include electron BPMs (eBPMs), X-ray BPMs (XBPMs), and diamond BPMs (DBPMs). Each type of BPM plays a crucial role in monitoring different aspects of beam behavior. For the electron beam’s positional shifts, the position shift detected by the XBPM closely corresponds with that observed by the eBPM shift. However, the position shifts measured by DBPMs are typically smaller compared to those detected by eBPMs. This discrepancy arises because the slit or mask used before DBPMs confines the beam, reducing the observed motion. Additionally, the photon beam’s movement around the focus point is less sensitive to variations in the electron beam’s position, particularly concerning changes in the emission photon angle. During adjustments to the gap of the insertion device, the XBPM measurements can exhibit substantial variations. In contrast, the position detected by the DBPM remains relatively stable, due to its method of using the beam center for position detection.