Ion feedback suppression in time projection chambers

“…In order to study a situation where the GEM foil does not act as a multiplier, a small potential difference was applied on a GEM foil [5,6] (in the case of this study DV GEM ¼ 20 V). The measured X-rays interaction rate was around 100 kHz/mm 2 .…”

Section: Measurements Of the Electron Transparencymentioning

confidence: 99%

Simulation of the dielectric charging-up effect in a GEM detector

Alfonsi

Croci

Pinto

et al. 2012

Nuclear Instruments and Methods in Physics Research Section A:

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a b s t r a c tThe charging up effect is well-known in detectors containing dielectric materials and it is due to electrons and ions liberated in an avalanche and collected on the dielectric surfaces. In particular in Gas Electron Multiplier (GEM) based detectors, charges can be captured by the Kapton that separates top and bottom electrodes. The collection of a substantial number of charges on the dielectric surfaces induces a modification of the field inside the GEM holes that implies important consequences on some fundamental parameters such as the electron transparency and the effective gain. The correct simulation of this effect opens new ways to the detailed study of the processes that happens in a GEM-based detector and gives the possibility to optimise the GEM geometry in order to avoid it. This paper compares results of the measurements and the simulations, with and without the introduction of the charging-up effect, of the GEM electron transparency in the case of a single GEM detector. The introduction of the charging up effect in the simulation resulted to be crucial in order to get the proper agreement with the measurements. The measurements and simulations of the GEM effective gain will be the subject of a future work.

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“…A limited positive charge can enter the drift volume before the resulting perturbation of the drift field seriously distorts the track. Gating techniques have been proposed, perhaps requiring another electrode layer [26]. A potential risk is that of electrical discharge or sparking, to which the chips are especially vulnerable.…”

Section: Summary Of Tests and Conclusionmentioning

confidence: 99%

Readout of TPC tracking chambers with GEMs and pixel chip

Kim¹,

Freytsis²,

Button‐Shafer³

et al. 2008

Nuclear Instruments and Methods in Physics Research Section A:

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Two layers of GEMs and the ATLAS Pixel Chip, FEI3, have been combined and tested as a prototype for Time Projection Chamber (TPC) readout at the International Linear Collider (ILC). The double-layer GEM system amplifies charge with gain sufficient to detect all track ionization. The suitability of three gas mixtures for this application was investigated, and gain measurements are presented. A large sample of cosmic ray tracks was reconstructed in 3D by using the simultaneous timing and 2D spatial information from the pixel chip. The chip provides pixel charge measurement as well as timing. These results demonstrate that a double GEM and pixel combination, with a suitably modified pixel ASIC, could meet the stringent readout requirements of the ILC.

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Ion feedback suppression in time projection chambers

Cited by 65 publications

References 38 publications

Development of a prototype GEM TPC with a gating grid for an H-dibaryon search experiment at J-PARC

Development of a prototype GEM TPC with a gating grid for an H-dibaryon search experiment at J-PARC

Simulation of the dielectric charging-up effect in a GEM detector

Readout of TPC tracking chambers with GEMs and pixel chip

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