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HK: Fachverband Physik der Hadronen und Kerne

HK 27: Poster

HK 27.49: Poster

Dienstag, 28. März 2017, 16:45–18:45, F Foyer

High resolution picoamperemeters for high voltage applications — •Dimitri Schaab, Justus Rödel, Markus Ball, Reinhard Beck, and Bernhard Ketzer — Helmholtz-Institut für Strahlen- und Kernphysik, Bonn, DE

Modern tracking detectors, as the future Time Projection Chambers for ALICE and the CBELSA/TAPS experiment, are based on Micro Pattern Gaseous Detector technology. In either case, Gaseous Electron Multipliers (GEM) will be used for the amplification of primary charges. In this scope, several studies at GEM-based test detectors are done which involve current measurements down to the order of picoamperes. For this purpose, current-meters with a high-impedance op-amp are used. Since GEM-related measurements have to be performed at voltages of several kilovolts, the current-meter must be designed such that it is decoupled from any external ground potential. At the present time, they are powered by batteries and read out wirelessly in order to avoid an external ground connection. To do measurements independently of the battery lifetime, a potential-free optical power supply was developed and tested. Moreover, a fully automatic calibration station was built to calibrate the current-meters at controlled temperature conditions. Latest investigations revealed a non-negligible temperature dependence that can be compensated by software if the temperature is known. Thus, a temperature monitoring is necessary which implies a revision of the devices. At stable temperatures, the absolute precision was determined to be below 2pA.

Supported by SFB/TR16.