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Single-Electron Response Using a GEM-MIGAS Electron Multiplier

2008; Institute of Electrical and Electronics Engineers; Volume: 55; Issue: 4 Linguagem: Inglês

10.1109/tns.2008.2001887

1558-1578

J.A. Mir, J.M. Maia, A.S. Conceição, R. Stephenson, J. Lipp, N.J. Rhodes, E.M. Schooneveld, H. Natal da Luz, J.F.C.A. Veloso, J.M.F. dos Santos,

Electron and X-Ray Spectroscopy Techniques

A Gas Electron Multiplier with a Micro-Induction Gap Amplifying Structure (GEM-MIGAS) is formed when a conventional GEM is operated with a short induction gap, typically set at 50 $\mu{\rm m}$ . Experimental studies were carried out to investigate the single-electron response of a GEM-MIGAS, using a ${\rm He/iso}{-}{\rm C}_{4}{\rm H}_{10}$ (85/15%) gas mixture operated in a flow mode at atmospheric pressure. The additional charge multiplication in the induction gap results in a gain increase up to one order of magnitude when compared to the GEM mode operation alone. A series of measurements were undertaken to examine the pulse height distributions induced by single-electrons under a wide range of bias voltages applied across the GEM holes, 100 to 550 V, and for a wide range of electric fields in the induction gap, 0.6 to 100 kV/cm. It was possible to sustain effective charge gains in excess of $3\times 10^{5}$ and multiplication relative variances around 0.4 over a large range of GEM voltages, enabling us to demonstrate single-electron detection efficiencies above 98%.