Nuclear Instruments and Methods in Physics Research A 513 (2003) 379–387 Luminescence and imaging with gas electron multipliers F.A.F. Fraga a,b, *, L.M.S. Margato a , S.T.G. Fetal a , M.M.F.R. Fraga a,b , R. Ferreira Marques a,b , A.J.P.L. Policarpo a,b a LIP—Coimbra, Departamento de F! ısica, Universidade de Coimbra, Coimbra 3004-516, Portugal b CFRMUC—Centro de F! ısica, Radia@ * ao e de Materiais, Departamento de F! ısica da, Universidade de Coimbra, Coimbra 3004-516, Portugal Abstract Although the GEM has been mainly used as a gaseous preamplifier device, it has been shown that using suitable gaseous mixtures the avalanches emit a large number of photons, in the UV, visible and/or NIR bands. This scintillation, readout by CCDs, has been used recently for the development of imaging detectors to be used with X-rays, alpha particles and neutrons. The luminescence process in the GEM and a summary of its applications will be presented. The latest developments, including the operation of the GEMs in photon counting mode, will also be referred. r 2003 Elsevier B.V. All rights reserved. PACS: 29.40.Cs; 29.40.Gx; 29.40.Mc Keywords: GEM detectors; CCD; Microstructures; Scintillation 1. Introduction The advantages of optical readout of detectors are well known: the electronics are decoupled from the detection media, becoming insensitive to electronic noise or RF pickup signals coming from the detector media and housing [1], they can cover large areas without dead spaces using optical systems such as lenses, mirrors, fibers and tapers, and, it should be emphasized, they are particularly suited for recording complex events when using true pixel readouts, making possible real multihit capability. 2D imaging detectors using gas scintil- lation with optical electronic readout have been widely used in Physics experiments during the last 30 years, but the idea of using the light pulses produced by the avalanches in proportional counters was suggested by Charpak as early as 1956 [2] and the earliest 2D gas scintillators with optical readout by PMs or intensified CCDs were initially used with wires and pure gases such as Xe, Kr, Ar and He with the addition of N 2 (see Fig. 1) [3]. These gases scintillate below 200nm and require the use of inefficient and expensive optics or optical wavelength shifters to couple the electronic optical readout to the detector. Later improvements, such as continuous ampli- fying structures (PPAC, grids) and the use of gas ARTICLE IN PRESS *Corresponding author. Address for correspondence: LIP- Coimbra, Departmento de F! ısica, Universidade de Coimbra, Coimbra 3000, Portugal. Tel.: +351-39-833-465; fax: +351-39- 822-358. E-mail address: francisco@lipc.fis.uc.pt (F.A.F. Fraga). 0168-9002/$-see front matter r 2003 Elsevier B.V. All rights reserved. doi:10.1016/j.nima.2003.08.066