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Efficient ion blocking in gaseous detectors and its application to gas-avalanch...
Lyashenko, A.; Breskin, A.; Chechik, R.; Santos, J. M. F. dos; Amaro, F. D.; Veloso, J. F. C. A.http://www.sciencedirect.com/science/article/B6TJM-4T8HH99-2/2/f970f5561a88e355e57ce6de077a59fa
The Photon-Assisted Cascaded Electron Multiplier Operation in CF _4 for Ion Ba...
Amaro, F. D.; Veloso, J. F. C. A.; Santos, J. M. F. dos; Breskin, A.; Chechik, R.; Lyashenko, A.The operation of the recently introduced photon assisted cascaded electron multiplier (PACEM) in CF4 is investigated. The PACEM uses the VUV scintillation produced in the electron avalanches of the first multiplier of the cascade to transfer the signal to the subsequent ones. The VUV scintillation induces the emission of a large number of photoelectrons from a Csl photocathode placed on the top-surface of the s...
PACEM: a new concept for high avalanche-ion blocking
Veloso, J. F. C. A.; Amaro, F. D.; Azevedo, C. D. R.; Santos, J. M. F. dos; Breskin, A.; Lyashenko, A.; Chechik, R.We present the Photon-Assisted Cascaded Electron Multiplier (PACEM) as a potential alternative for ion back-flow suppression in gaseous cascade electron multipliers. Using a Micro Hole and Strip Plate-Gas Electron Multiplier (MHSP-GEM) configuration, the number of ions flowing back to the scintillation region is about 1.5 ions per primary electron at an optical gain of 6.5 and a drift field of 0.1 kV/cm, and ab...
Micro-hole and strip plate-based photosensor
Freitas, E. D. C.; Veloso, J. F. C. A.; Breskin, A.; Chechik, R.; Amaro, F. D.; Ferreira, L. F. Requicha; Maia, J. M.; Santos, J. M. F. dosThe performance of a new VUV photosensor, based on an micro-hole and strip plate (MHSP) electron multiplier with a CsI photocathode deposited on its top electrode, is described. This photosensor presents gains above 104 when operating in an Ar-5%Xe gas mixture at 1 atm. Although the gain of a single MHSP is not sufficient for efficient detection of single photons, this simple UV photosensor may be useful for th...
Operation of a single-GEM in noble gases at high pressures
Amaro, F. D.; Conceição, A. S.; Veloso, J. F. C. A.; Coelho, L. C. C.; Fernandes, L. M. P.; Ferreira, L. F. Requicha; Lopes, J. A. M.We report the performance of a single-Gas Electron Multiplier (GEM) operating in pure Ar, Xe, and in Ar-50lmbar Xe mixtures, in the range of 1-7lbar. The maximum gain and voltage that can be applied to the GEM are investigated as a function of filling pressure and compared to the results obtained with triple-GEM and MHSP (Micro Hole and Strip Plate) multipliers. The maximum gain achieved at 1lbar Xe is about 10...
Ion-induced effects in GEM and GEM/MHSP gaseous photomultipliers for the UV and...
Breskin, A.; Mörmann, D.; Lyashenko, A.; Chechik, R.; Amaro, F. D.; Maia, J. M.; Veloso, J. F. C. A.; Santos, J. M. F. dosWe report on the progress in the study of cascaded GEM and GEM/MHSP gas avalanche photomultipliers operating at atmospheric pressure, with CsI and bialkali photocathodes. They have single-photon sensitivity, ns time resolution and good localization properties. We summarize operational aspects and results, with the highlight of a high-gain stable gated operation of a visible-light device. Of particular importanc...
MHSP operation in pure xenon
Luz, H. Natal da; Veloso, J. F. C. A.; Amaro, F. D.; Ferreira, L. F. Requicha; Santos, J. M. F. dos; Breskin, A; Chechik, R.We present latest results of a micro-hole and strip plate (MHSP) electron multiplier operating in pure xenon at atmospheric pressure. We report on avalanche gain of ~2×104, stable within ~3% after an accumulated charge of 4 [mu]C/mm2, when irradiated with 0.5 kHz/mm2 5.9 keV photons. No photon-induced secondary effects or discharges have been observed at this gain. An energy resolution of 14% was obtained with ...
MHSP in reversed-bias operation mode for ion blocking in gas-avalanche multipliers
Veloso, J. F. C. A.; Amaro, F. D.; Maia, J. M.; Lyashenko, A. V.; Breskin, A.; Chechik, R.; Santos, J. M. F. dos; Bouianov, O.; Bouianov, M.We present recent results on the operation of gas-avalanche detectors comprising a cascade of gas electron multipliers (GEMs) and Mico-Hole & Strip Plate (MHSP) multiplier operated in reversed-bias (R-MHSP) mode. The operation mechanism of the R-MHSP is explained and its potential contribution to ion-backflow (IBF) reduction is demonstrated. IBF values of 4×10-3 were obtained in cascaded R-MHSP and GEM multipl...
Planar LAAPDs: temperature dependence, performance, and application in low-ener...
Ludhova, L.; Amaro, F. D.; Antognini, A.; Biraben, F.; Cardoso, J. M. R.; Conde, C. A. N.; Covita, D. S.; Dax, A.; Dhawan, S.; Fernandes, L. M. P.An experiment measuring the 2S Lamb shift in muonic hydrogen ([mu]-p) was performed at the Paul Scherrer Institute, Switzerland. It required small and compact detectors for 1.9 keV X-rays (2P-1S transition) with an energy resolution around 25% at 2 keV, a time resolution better than 100 ns, a large solid angle coverage, and insensitivity to a 5 T magnetic field. We chose Large Area Avalanche Photodiodes (LAAPDs...
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