First Results from Two Novel In-vacuum Magnetic Field Measurement Devices as Built at Hzb

The characterization of cryogenic in vacuum permanent magnet undulators with periods less than 20 mm and correspondingly narrow gaps requires new in-vacuum measurement systems. The positioning accuracy of the HZB in-vacuum Hallprobe bench has substantially been improved (a few μm) with appropriate feedback systems. A new in-vacuum cable tray has been developed. Another system for field integral measurements, an in-vacuum moving wire, is under commissioning. Both devices are presented. IN-VACUUM HALLPROBE BENCH Positioning Accuracy The general layout of the bench has been presented a few years ago [1]. The accuracy of the device is based on five piezo actuators and five optical measurement devices for feedback: three laser interferometer channels and two 2D-position sensitive detectors. The positioning accuracy of the in-vacuum Hallprobe bench has been successfully tested over a length of 0.5 m with the laser interferometer feedback switched on [2]. The range was limited because the cable tray was not operational, yet. Meanwhile extensive tests of the new in-vacuum cable tray have been performed. The tests will be described in the next section.