Hall probe carriage for in-tunnel measurements

A hand-held carriage that contains two Hall sensors is used to regularly scan the magnetic field profiles of all undulators at PETRA and FLASH. During maintenance shut-down periods, we screen all insertion devices for radiation induced damage by sliding the carriage along the magnet structures. The recorded field profile is normalized and compared to values from previous years and is checked for deviations along the beam axis. Radiation damage is usually strongest on the upstream side of the undulator and, if detected early, compensational measures can be taken.