The Online Undulator Magnetic Field Measurement System

The undulator is the core device for producing high-energy synchrotron radiation light in Synchrotron Radiation and Free Electron Laser facilities. The long-term operation of the undulator is bound to be damaged by radiation. Furthermore, this radiation damage leads to the reduction or even demagnetization of the magnetic field, directly affecting the electron beam's operating state and the light's performance and stability. This magnetic measurement system aims to monitor the magnetic flux change to obtain the undulator's local magnetic field disturbance or decay. Moreover, this system provides a way to get phase errors and electron trajectories by estimating the half-period magnetic field integrals for each magnetic pole. The measurement experiments on the undulator in SSRF are in progress.