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Negative Ion Drift and Diffusion in a TPC near 1 Bar  [PDF]
C. J. Martoff,R. Ayad,M. Katz-Hyman,G. Bonvicini,A. Schreiner
Physics , 2004, DOI: 10.1016/j.nima.2005.08.103
Abstract: Drift velocity and longitudinal diffusion measurements are reported for a Negative Ion TPC (NITPC) operating with Helium + carbon disulfide gas mixtures at total pressures from 160 to 700 torr. Longitudinal diffusion at the thermal-limit was observed for drift fields up to at least 700 V/cm in all gas mixtures tested. The results are of particular interest in connection with mechanical simplification of Dark Matter searches such as DRIFT, and for high energy physics experiments in which a low-Z, low density, gaseous tracking detector with no appreciable Lorentz drift is needed for operation in very high magnetic fields.
Space-Charge Effects in an Ungated GEM-based TPC  [PDF]
F. V. B?hmer,M. Ball,S. D?rheim,C. H?ppner,B. Ketzer,I. Konorov,S. Neubert,S. Paul,J. Rauch,M. Vandenbroucke
Physics , 2012,
Abstract: A fundamental limit to the application of Time Projection Chambers (TPCs) in high-rate experiments is the accumulation of slowly drifting ions in the active gas volume, which compromises the homogeneity of the drift field and hence the detector resolution. Conventionally, this problem is overcome by the use of ion-gating structures. This method, however, introduces large dead times and restricts trigger rates to a few hundred per second. The ion gate can be eliminated from the setup by the use of Gas Electron Multiplier (GEM) foils for gas amplification, which intrinsically suppress the backflow of ions. This makes the continuous operation of a TPC at high rates feasible. In this work, Monte Carlo simulations of the buildup of ion space charge in a GEM-based TPC and the correction of the resulting drift distortions are discussed, based on realistic numbers for the ion backflow in a triple-GEM amplification stack. A TPC in the future PANDA experiment at FAIR, in which antiproton-proton interaction rates up to 2 x 10^7 per second will be reached, serves as an example for the experimental environment. The simulations show that space charge densities up to 65 fC per cubic cm are reached, leading to electron drift distortions of up to 10 mm. The application of a laser calibration system to correct these distortions is investigated. Based on full simulations of the detector physics and response, we show that it is possible to correct for the drift distortions and to maintain the good momentum resolution of the GEM-TPC.
Performances of a GEM-based Time Projection Chamber prototype for the AMADEUS experiment  [PDF]
M. Poli Lener,M. Bazzi,G. Corradi,C. Curceanu,A. D'Uffizi,C. Paglia,A. Romero Vidal,E. Sbardella,A. Scordo,D. Tagnani,J. Zmeskal
Physics , 2013,
Abstract: A large number of high-energy and heavy-ion experiments successfully used Time Projection Chamber (TPC) as central tracker and particle identification detector. However, the performance requirements on TPC for new high-rate particle experiments greatly exceed the abilities of traditional TPC read out by multi-wire proportional chamber (MWPC). Gas Electron Multiplier (GEM) detector has great potential to improve TPC performances when used as amplification device. In this paper we present the R&D activity on a new GEM-based TPC detector built as a prototype for the inner part for AMADEUS, a new experimental proposal at the DAFNE collider at Laboratori Nazionali di Frascati (INFN), aiming to perform measurements of the low-energy negative kaons interactions in nuclei. In order to evaluate the GEM-TPC performances, a 10x10 cm2 prototype with a drift gap up to 15 cm has been realized. The detector was tested at the pM1 beam facility of the Paul Scherrer Institut (PSI) with low momentum pions and protons, without magnetic field. Drift properties of argonisobutane gas mixtures are measured and compared withMagboltz prediction. Detection efficiency and spatial resolution as a function of a large number of parameters, such as the gas gain, the drift field, the front-end electronic threshold and particle momentum, are illustrated and discussed. Particle identification capability and the measurement of the energy resolution in isobutane-based gas mixture are also reported.
A Study of a Mini-drift GEM Tracking Detector  [PDF]
B. Azmoun,B. DiRuzza,A. Franz,A. Kiselev,R. Pak,M. Phipps,M. L. Purschke,C. Woody
Physics , 2015,
Abstract: A GEM tracking detector with an extended drift region has been studied as part of an effort to develop new tracking detectors for future experiments at RHIC and for the Electron Ion Collider that is being planned for BNL or JLAB. The detector consists of a triple GEM stack with a small drift region that was operated in a mini TPC type configuration. Both the position and arrival time of the charge deposited in the drift region were measured on the readout plane which allowed the reconstruction of a short vector for the track traversing the chamber. The resulting position and angle information from the vector could then be used to improve the position resolution of the detector for larger angle tracks, which deteriorates rapidly with increasing angle for conventional GEM tracking detectors using only charge centroid information. Two types of readout planes were studied. One was a COMPASS style readout plane with 400 micron pitch XY strips and the other consisted of 2x10mm2 chevron pads. The detector was studied in test beams at Fermilab and CERN, along with additional measurements in the lab, in order to determine its position and angular resolution for incident track angles up to 45 degrees. Several algorithms were studied for reconstructing the vector using the position and timing information in order to optimize the position and angular resolution of the detector for the different readout planes. Applications for large angle tracking detectors at RHIC and EIC are also discussed.
GEM operation in helium and neon at low temperatures  [PDF]
A. Buzulutskov,J. Dodd,R. Galea,Y. Ju,M. Leltchouk,P. Rehak,V. Tcherniatine,W. J. Willis,A. Bondar,D. Pavlyuchenko,R. Snopkov,Y. Tikhonov
Physics , 2005, DOI: 10.1016/j.nima.2005.04.066
Abstract: We study the performance of Gas Electron Multipliers (GEMs) in gaseous He, Ne and Ne+H2 at temperatures in the range of 2.6-293 K. In He, at temperatures between 62 and 293 K, the triple-GEM structures often operate at rather high gains, exceeding 1000. There is an indication that this high gain is achieved by Penning effect in the gas impurities released by outgassing. At lower temperatures the gain-voltage characteristics are significantly modified probably due to the freeze-out of impurities. In particular, the double-GEM and single-GEM structures can operate down to 2.6 K at gains reaching only several tens at a gas density of about 0.5 g/l; at higher densities the maximum gain drops further. In Ne, the maximum gain also drops at cryogenic temperatures. The gain drop in Ne at low temperatures can be reestablished in Penning mixtures of Ne+H2: very high gains, exceeding 10000, have been obtained in these mixtures at 50-60 K, at a density of 9.2 g/l corresponding to that of saturated Ne vapor near 27 K. The results obtained are relevant in the fields of two-phase He and Ne detectors for solar neutrino detection and electron avalanching at low temperatures.
Study of ion feedback in multi-GEM structures  [PDF]
A. Bondar,A. Buzulutskov,L. Shekhtman,A. Vasiljev
Physics , 2002, DOI: 10.1016/S0168-9002(02)01763-1
Abstract: We study the feedback of positive ions in triple and quadruple Gas Electron Multiplier (GEM) detectors. The effects of GEM hole diameter, detector gain, applied voltages, number of GEMs and other parameters on ion feedback are investigated in detail. In particular, it was found that the ion feedback is independent of the gas mixture and the pressure. In the optimized multi-GEM structure, the ion feedback current can be suppressed down to 0.5% of the anode current, at a drift field of 0.1 kV/cm and gain of 10^4. A simple model of ion feedback in multi-GEM structures is suggested. The results obtained are relevant to the performance of time projection chambers and gas photomultipliers.
Triple GEM operation in compressed He and Kr  [PDF]
A. Bondar,A. Buzulutskov,L. Shekhtman,V. Snopkov,A. Vasiljev
Physics , 2002, DOI: 10.1016/S0168-9002(02)01414-6
Abstract: We study the performance of the triple GEM (Gas Electron Multiplier) detector in pure noble gases He and Kr at high pressures, varying from 1 to 15 atm. The operation in these gases is compared to that recently studied in Ne, Ar and Xe. It turned out that light noble gases, He and Ne, have superior performance: the highest gain, approaching 10^5, and an unusual gain dependence on pressure. In particular, the maximum gain in He and Ne does not decrease with pressure, in contrast to Ar, Kr and Xe. These results are of high relevance for understanding basic mechanisms of electron avalanching in noble gases and for applications in cryogenic particle detectors, X-ray imaging and neutron detectors.
Triple-GEM performance in He-based mixtures  [PDF]
A. Bondar,A. Buzulutskov,L. Shekhtman,A. Vasiljev
Physics , 2006,
Abstract: The performance of triple-GEM detectors in He+N2 gas mixtures is studied in the range of 1-10 atm. The results obtained are relevant in the field of minimization of ionic space-charge effect in the TPC and neutron detection.
Advances in Thick GEM-like gaseous electron multipliers. Part I: atmospheric pressure operation  [PDF]
C. Shalem,R. Chechik,A. Breskin,K. Michaeli
Physics , 2006, DOI: 10.1016/j.nima.2005.12.241
Abstract: Thick GEM-like (THGEM) gaseous electron multipliers are made of standard printed-circuit board perforated with sub-millimeter diameter holes, etched at their rims. Effective gas multiplication factors of 100000 and 10000000 and fast pulses in the few nanosecond rise-time scale were reached in single- and cascaded double-THGEM elements, in atmospheric-pressure standard gas mixtures with single photoelectrons. High single-electron detection efficiency is obtained in photon detectors combining THGEMs and semitransparent UV-sensitive CsI photocathodes or reflective ones deposited on the top THGEM face; the latter benefits of a reduced sensitivity to ionizing background radiation. Stable operation was recorded with photoelectron fluxes exceeding MHz/mm2. The properties and some potential applications of these simple and robust multipliers are discussed.
Cosmic ray tests of a GEM-based TPC prototype operated in Ar-CF4-isobutane gas mixtures  [PDF]
M. Kobayashi,R. Yonamine,T. Tomioka,A. Aoza,H. Bito,K. Fujii,T. Higashi,K. Hiramatsu,K. Ikematsu,A. Ishikawa,Y. Kato,H. Kuroiwa,T. Matsuda,O. Nitoh,H. Ohta,K. Sakai,R. D. Settles,A. Sugiyama,H. Tsuji,T. Watanabe,H. Yamaoka,T. Yazu
Physics , 2010, DOI: 10.1016/j.nima.2011.02.042
Abstract: Argon with an admixture of CF4 is expected to be a good candidate for the gas mixture to be used for a time projection chamber (TPC) in the future linear collider experiment because of its small transverse diffusion of drift electrons especially under a strong magnetic field. In order to confirm the superiority of this gas mixture over conventional TPC gases we carried out cosmic ray tests using a GEM-based TPC operated mostly in Ar-CF4-isobutane mixtures under 0 - 1 T axial magnetic fields. The measured gas properties such as gas gain and transverse diffusion constant as well as the observed spatial resolution are presented.
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