BPM Offset of NSLS-II Storage Ring Based on BBA Measurement
- Brookhaven National Lab. (BNL), Upton, NY (United States). Photon Sciences Directorate
Beam based alignment (BBA) is the final calibration of the Beam position monitor (BPM) readings based on the quadrupole centers and it becomes essential process for the modern synchrotron light sources. For the convenient BBA implementation, usually BPMs are placed close to the quadrupoles and the beam is adjusted to pass the center of the quadrupoles. Therefore, measured BPM BBAs are, in fact, the BPM offsets relative to the quadrupole centers, and by observing their variations, we can estimate the relative movements of the BPMs. In NSLS-II, the BPM BBAs are measured whenever the beam-time allows and the variations are being observed. However, because changing BBAs in the BPM readings has direct and significant impact on the machine operation as well as the user experiments, they are not applied instantly. Instead, in NSLS-II, the official BBA values are managed by the snapshot archiving and retrieving system, called MASAR (MAchine Snapshot Archiving and Retrieve), so that they are well organized and can be easily set to any stored set of BBAs values. NSLS-II is implementing MASAR as a part of EPICS control system for the convenient and mistake-free machine operation. Each snapshot is a group of key-value pairs where keys are EPICS Process Variables (PVs). The snapshots are organized by configurations where each configuration has specific PV sets. And each configuration saves snapshots with titles corresponding their purposes such as normal user operations or specific beam studies. Anyone with control system account can save snapshots and they can be restored whenever needed. One of the configurations is “SR_BPM_BBAS" and the configuration includes the set of EPICS PVs for the storage ring BPM BBA values. This configuration also includes the BBAs of the in the straight sections, called ID (insertion device) BPMs playing important roles in user experiments. The ID BPM BBAs are also directly engaged in the active interlock (AI) machine protection system, which prevents the mechanical damage from the ID radiation. However, in estimating ID BPM BBAs, because there is no quadrupoles around them, interpolations from the surrounding sector BPM BBAs are used. This note focuses on the BPM offset variations based on the BBA measurement data and does not discuss about the ID BPM BBAs because they are not the direct measures of the offsets.
- Research Organization:
- Brookhaven National Lab. (BNL), Upton, NY (United States)
- Sponsoring Organization:
- USDOE Office of Science (SC), Basic Energy Sciences (BES)
- DOE Contract Number:
- SC0012704
- OSTI ID:
- 1504396
- Report Number(s):
- NSLSII-ASD-TN-285; BNL-211217-2019-TECH
- Country of Publication:
- United States
- Language:
- English
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