Charge Transfer and Charge Broadening of GEM Structures in High Magnetic Fields

Abstract

We report on measurements of charge transfer in GEM structures in high magnetic fields. These were performed in the framework of the R&D work for a Time Projection Chamber at a future Linear Collider. A small test chamber has been installed into the aperture of a superconducting magnet with the GEM structures mounted perpendicular to the B field direction. The charge transfer is derived from the electrical currents monitored during irradiation with an ${}^{55}$Fe source. No severe loss of primary ionisation charge is observed, but an improved ion feedback suppression is achieved for high magnetic fields. Additionally, the width of the charge cloud released by individual ${}^{55}$Fe photons is measured using a finely segmented strip readout after the triple GEM structure. Charge widths between 0.3 and 0.5 mm RMS are observed, which originate from the charge broadening inside the GEM readout. This charge broadening is only partly suppressed at high magnetic fields.

11 pages, 9 figures

References in corpus (1)

• Modelling and Measurement of Charge Transfer in Multiple GEM Structures

Cited by in corpus (6)

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• Advances in ion back-flow reduction in cascaded gaseous electron multipliers incorporating R-MHSP elements
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• Reduction of ion back flow using a quadruple GEM detector with various gas mixtures
• Effective gain and Ion Back Flow study of triple and quadruple gem detector
• Performance of a large aperture GEM-like gating device for the International Linear Collider