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2006 Nuclear Science Symposium and Medical Imaging Conference (IEEE-NSS), San Diego : États-Unis (2006)
Micromegas TPC R&D results
P. Colas1, Y. Giomataris1, V. Lepeltier2, M. T. Ronan, K. Sachs, T. Zerguerras3

We present final analyis results of cosmic ray data taken with a Large-Area Micromegas TPC by the Berkeley-Orsay-Saclay (BOS) collaboration. The TPC gas chamber for these R&D studies was 50 cm diameter and 50 cm long and was operated with three gas mixtures, Ar:CF4 3%, Ar:CH4 (P10) and Ar:Isobutane 5% in magnetic fields up to 2 tesla. A large-area, 38 cm diameter, copper Micromegas electro-mesh with 60 micron pitch, and 50 micron mesh to anode pad plane gap provided gains up to 3000. Over 1000 channels of TPC readout electronics, with 1X10 and 2X10 mm^2 anode pads, have been used to cover the detector area. The detector ran very smoothly with excellent gain uniformity. Precision measurements of drift velocity, transverse and longitudinal diffusion, and electron attachment have been made and compared to MagBoltz simulations. We have obtained a Micromegas TPC extrapolated zero-drift, point resolution of 50 microns. We compare the measured resolution dependence on drift distance, up to 50 cm, to parameterized simulations of the drift and avalanche of individual ionization electrons for the gases studied. We show expectations for a large gaseous International Linear Collider (ILC) detector based on a 1.7-2 m radius TPC tracking chamber, operating at 1 atmosphere in a magnetic field of 3-4 tesla with electron drifts up to 2.5 m.
1 :  DAPNIA - Département d'Astrophysique, de physique des Particules, de physique Nucléaire et de l'Instrumentation Associée
2 :  LAL - Laboratoire de l'Accélérateur Linéaire
3 :  IPNO - Institut de Physique Nucléaire d'Orsay
Physique/Physique/Instrumentations et Détecteurs