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Readout Electronics for LAr TPC: (the small picture). FLARE workshop Nov 4-6,2004. Paul Rubinov. Statement of the problem. So we have a LAr TPC: How much signal do we collect? How much noise do we have? Good news! I don’t have to think about it: ICARUS already built a LAr TPC
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Readout Electronics for LAr TPC: (the small picture) FLARE workshop Nov 4-6,2004 Paul Rubinov
Statement of the problem • So we have a LAr TPC: • How much signal do we collect? • How much noise do we have? • Good news! • I don’t have to think about it: • ICARUS already built a LAr TPC NIMA preprint“Design, construction and tests of the ICARUS T600 detector”
Statement of the problem • ICARUS already built a LAr TPC NIMA preprint“Design, construction and tests of the ICARUS T600 detector”
Statement of the problem Too simple: in fact the shape of the pulse depends on the geometry of the track relative to the wire! Sometimes the induced plane looks bipolar, sometimes it does not!
Statement of the problem • Lets assume a “typical” situation: 25000e signal on 500pF (ref A.Para)with a shaping time t~1usQ:How hard is that?A:Not too hard… • “Off the shelf” solution: MASDA-X by Tom Zimmerman
Solution of the problem • “Off the shelf” solution: MASDA-X by Tom Zimmerman at t~1.4ms, N=65e+5 e/pF=2500e noise (but this chip optimized for <100pF!) 2.5 e/pF is easy… for Tom et.al. • e.g. VA-1ch (IDEAS) is 125e+2.6e/pF @t=1.25mS • Key features: fat transistors (W/L), MUCHO current (Ids) • e.g.: VA-1ch => 10mA preamp bias MASDA-X=> 0.8mA preamp bias
Digression on noise a1~1/gm and gm~(Cgs1/2)(Ids1/2)/L http://www.inst.bnl.gov/MicroElectronics/PDF/NSS99_Invited_slides.pdf
Cost • ASICs are an extremely powerful tool. • If you can explain what you need, you will get it. • A new ASIC costs $1M (roughly, including everything) • For 250 K ch, that does not sound so bad • Other semi custom options also exist. • In this case a front end ASIC probably makes sense.
Cost • The point is the problem is not the FRONT END electronics. • The problem is the SYSTEM. • HV, cables, connectors, grounding, shielding, leakage currents, and on and on…