Resolution studies of cosmic-ray tracks in a TPC with GEM readout

• Published in: Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment Vol. 538; no. 1; pp. 372 - 383
• Main Authors: Carnegie, R.K., Dixit, M.S., Dubeau, J., Karlen, D., Martin, J.-P., Mes, H., Sachs, K.
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 11.02.2005
• Subjects: Gas electron multiplier; Gaseous detectors; Micro-pattern gas detectors; Position-sensitive detectors; Position-sensitive detectors; Gas electron multiplier; 29.40.Cs; Gaseous detectors; 29.40.Gx; Micro-pattern gas detectors
• ISSN: 0168-9002; 1872-9576
• DOI: 10.1016/j.nima.2004.08.132

A large volume time projection chamber (TPC) is a leading candidate for the central tracking detector at a future high energy linear collider. To improve the resolution a new readout based on micro-pattern gas detectors is being developed. Measurements of the spatial resolution of cosmic-ray tracks in a GEM TPC are presented. We find that the resolution suffers if the readout pads are too wide with respect to the charge distribution at the readout plane due to insufficient charge sharing. For narrow pads of 2 × 6 mm 2 we measure a resolution of 100 μ m at short drift distances in the absence of an axial magnetic field. The dependence of the spatial resolution as a function of drift distance allows the determination of the underlying electron statistics. Our results show that the present technique uses about half the statistical power available from the number of primary electrons. The track angle effect is observed as expected.