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Linear Collider TPC R&D in Canada. Madhu Dixit Carleton University. ExB & track angle systematics in a TPC (Aleph TPC example). TPC wire/pad readout. ExB cancels track angle effect. 100 µm. Average Aleph resolution ~ 150 µm About 100 µm best for all drift distances
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Linear Collider TPC R&D in Canada Madhu Dixit Carleton University
ExB & track angle systematics in a TPC(Aleph TPC example) TPC wire/pad readout ExB cancels track angle effect 100 µm Average Aleph resolution ~ 150 µm About 100 µm best for all drift distances Limit from diffusion (10 cm drift) ~ 15 µm; (2 m drift) ~ 60 µm 100 µm limit for all drift distances comes from wide pad response M. Dixit
TPC read out with a Gas Electron Multiplier (GEM*) * F. Sauli, NIM A386,531 (1997) GEM spatial resolution ~ 40 µm with 200 µm pitch anodes Impractical for a TPC TPC pad widths ~ mm All charge on a single pad for a TPC in high B field Difficult centroid finding Resolution ~ Pad width/√12 How to find charge centroid in a GEM? • Zigzag shape makes chevrons share charge between pads to facilitate centroid finding • Optimize readout geometry and diffusion to do the best with rectangular pads • Where is the induced signal on the neighboring pads? M. Dixit
MPGD-TPC R&D in Canada - Goals • New ideas to get good space-point resolution from ~ mm wide pads • Studies with a GEM & Micromegas test cells using collimated x-rays • Limits to achievable resolution by with conventional techniques by optimizing geometry and gas diffusion • 15 cm drift TPC with GEM readout • Operating parameters • Cosmic ray tracking studies • Assess the performance of MPGD-TPC in a test beam and in a high magnetic field • (r-) ~ 70 µm within reach with R&D, M. Dixit
Pads centroid from induced signals in a GEM GEM Proportional wire Anode pads Cathode pads Short ~ 200 ns signal Wire/pad readout electronics won’t work! Need fast high frequency pulse shape sampling electronics M. Dixit
Resistive anode GEM test cell setup M. Dixit
Outlook & summary • Consensus for a 500 GeV e+ e- linear collider within this decade - proposals in Europe & in the US & Japan • A micro-pattern detector (MPGD) readout TPC is being be developed for the LC detector with resolution and 2 track resolving power approaching diffusion limits • Better MPGD-TPC resolution has a significant impact on the design of the LC detector design and its physics reach M. Dixit