Darmstadt 2016 – wissenschaftliches Programm

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HK: Fachverband Physik der Hadronen und Kerne

HK 61: Instrumentation XVIII

HK 61.6: Vortrag

Donnerstag, 17. März 2016, 18:00–18:15, S1/01 A2

Measurement of ion mobility in Argon and Neon based gas mixtures — •Alexander Deisting for the ALICE collaboration — Research Division and EMMI, GSI Helmholtzzentrum für Schwerionenforschung — Physikalisches Institut, Universität Heidelberg

Gaseous drift chambers are currently operated at different experiments. In addition such detectors are foreseen for new experiments or upgrades of existing experiments. The performance of detectors with gas as detection medium strongly depends on the parameters of the gas used. One of these is the ion mobility µ, relating the velocity of drifting ions to the applied drift field. If the ion mobility is known it is e.g. possible to estimate the time development of space charges created by ions drifting through the gas volume of the detector and to correct for them.

To measure µ a dedicated gaseous detector was built. It features a gas amplification stage using a stack of three Gas Electron Multiplier (GEM) foils. In parallel to the GEM stack a mesh is mounted, which serves as drift cathode. For the measurement this detector is irradiated with an ionising source. The primary ionisation charges are then amplified by the GEM stack and a signal at the pad plane can be measured. In addition the ions produced during the amplification process will drift towards the mesh and induce a signal there. From the time difference between these signals, the ion mobility can be calculated.

With this setup the ion mobility in several Argon and Neon based gas mixtures was measured. The influence of O₂ and H₂O contamination on the mobility was studied as well.