High resolution surface scanning of Thick-GEM for single photo-electron detection

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13 Citations (Scopus)

Abstract

An optical system for high resolution scanning of TGEM UV photon detection systems is introduced. The structure exploits the combination of a single Au-coated TGEM under study, and an asymmetric MWPC (Close Cathode Chamber) as post-amplification stage. A pulsed UV LED source with emission down to 240 nm has been focused to a spot of 0.07 mm on the TGEM surface, and single photo-electron charge spectra has been recorded over selected two dimensional regions. This way, the TGEM gain (order of 10-100) and TGEM photo-electron detection efficiency is clearly separated, unlike in case of continuous illumination. The surface structure connected to the TGEM photon detection is well observable, including inefficiencies in the holes and at the symmetry points between holes. The detection efficiency as well as the gas gain are fluctuating from hole to hole. The gain is constant in the hexagon around any hole, pointing to the fact that the gain depends on hole geometry, and less on the position where the electron enters. The detection probability map strongly changes with the field strength above the TGEM surface, in relation to the change of the actual surface field configuration. The results can be confronted with position-dependent simulations of TGEM electron transfer and gas multiplication.

Original languageEnglish
Pages (from-to)16-23
Number of pages8
JournalNuclear Instruments and Methods in Physics Research, Section A: Accelerators, Spectrometers, Detectors and Associated Equipment
Volume694
DOIs
Publication statusPublished - Dec 1 2012

Keywords

  • High resolution scan
  • Thick GEM
  • UV photon detector

ASJC Scopus subject areas

  • Nuclear and High Energy Physics
  • Instrumentation

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