High-voltage measurement and calibration techniques for precision experiments with electron coolers at ion storage rings
by Daniel Winzen (Institut für Kernphysik, WWU Münster)
at GSI ( KBW Lecture Hall - Sider Room )
In precision experiments at ion storage rings the velocity of the ions is a critical quantity. For measurements at the ESR and at CRYRING@ESR the ion velocity is determined by electron coolers. Consequently, a precise knowledge of the acceleration voltage of the cooler’s electron beam is essential for the accuracy of the experiments. The current standard technique to measure high voltages is to scale down the voltage to the most sensitive range of commercially available 8.5 digit resolution digital multimeters. In this method the scaling of high voltages is realized by custom-made HV-divider systems with ppm-precise scale factors. To guarantee the precision of the scale factors, calibration techniques in the same precision regime are mandatory. The fundament of calibrations is the traceability to natural standards provided by national metrology institutes such as the Physikalisch-Technische Bundesanstalt (PTB). Until recently this was not possible for high-voltage dividers due to the lack of suitable calibration methods. However, with different new techniques developed by University of Münster, University of Darmstadt and PTB traceability to natural standards such as the Josephson voltage standard has been accomplished. In this talk high-voltage measurement and calibration techniques will be presented based on measurements with the new CRYRING@ESR high-voltage divider which was constructed at the University of Münster.
This work was supported by BMBF under contract number 05P15PMFAA, GSI F&E project MSWEIN1416 and HGS-HIRe for FAIR.