Ion backflow studies with a triple-GEM stack with increasing hole pitch

Abstract

Gas Electron Multipliers have undergone a very consistent development since their invention in 1997. Their production procedures have been tuned in such a way that nowadays it is possible to produce foils with areas of the order of the square meter that can operate at a reasonable gain, uniform over large areas and with a good stability in what concerns electrical discharges. For the 3rd run of LHC, they will be included in the CMS and ALICE experiments after significant upgrades of the detectors, confirming that these structures are suitable for very large experiments. In the special case of Time Projection Chambers, the ion backflow and the energy resolution are sensitive issues that must be addressed and the GEM has shown to be able to deal with both of them. In this work, a stack of three GEMs with different pitches has been studied as a possible future approach for ion backflow suppression to be used in TPCs and other detection concepts. With this approach, an ion backflow of 1 % with an energy resolution of 12 % at 5.9 k\eV has been achieved with the detector operating in an Ar/Co (90/10) mixture at a gain of ∼ 2000.

Effective Gain and Ion Back Flow study of triple and quadruple GEM detector

“…Large IBF tends to cause a distortion of the uniform electric field because of the slow drift velocity of heavier positive ions. Over the past decade several research groups have worked significantly to reduce the IBF both without the effect of magnetic field [11,[14][15][16] and also under the effect of magenetic field [17]. One way to minimize 2022 JINST 17 T12004 IBF for a specific effective gain of the GEM detector is to operate the detector such that the electric fields in different gaps are not the same [14][15][16][17].…”

“…Over the past decade several research groups have worked significantly to reduce the IBF both without the effect of magnetic field [11,[14][15][16] and also under the effect of magenetic field [17]. One way to minimize 2022 JINST 17 T12004 IBF for a specific effective gain of the GEM detector is to operate the detector such that the electric fields in different gaps are not the same [14][15][16][17]. In this study for minimizing IBF in triple GEM detector, an effective gain of 2500 was chosen and the corresponding IBF as in figure 5(b) was 36%.…”

Numerical estimation of discharge probability in GEM-based detectors

“…Recently, the triple GEM detectors being used to upgrade the Muon system of CMS [5] also implements similar distribution of amplification fields in different GEM layers. This distribution, however, has adverse effect on the ion back-flow suppression which is of importance for a GEM-based TPC [19][20][21].…”