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Limitations on Microstrip Ladder Length. International Workshop on Future Linear Colliders University of Tokyo, 11-15 November 2013 Bruce Schumm Santa Cruz Institute for Particle Physics. Study involved: Measurements of readout noise vs. strip load
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Limitations on Microstrip Ladder Length International Workshop on Future Linear Colliders University of Tokyo, 11-15 November 2013 Bruce Schumm Santa Cruz Institute for Particle Physics
Study involved: • Measurements of readout noise vs. strip load • SPICE-level simulation of readout noise, including network effects • Pulse-development simulation to determine operating point and length limitations
Series Resistance Parallel Resistance Amplifier Noise (parallel) Amplifier Noise (series) Dominant term for long ladders (grows as L3/2) Standard Form for Readout Noise (Spieler) Fi , Fv are signal shape parameters that can be determined from average scope traces. Expression assumes single, lumped R, C load element; in fact, microstrip electrode is a distributed network
Sensor “Snake” Sensor “Snake”: Read out up to 13 daisy-chained 5cm sensors (with LSTFE-1 ASIC) LSTFE1 chip on Readout Board ( =1.8 s) Can read out from end, or from middle of chain (“center-tap”)
Pulse Development Simulation Long Shaping-Time Limit: strip sees signal if and only if hole is collected onto strip (no electrostatic coupling to neighboring strips) Include:Landau deposition (SSSimSide; Gerry Lynch LBNL), variable geometry, Lorentz angle, carrier diffusion, electronic noise and digitization effects
Expected Noise vs. Ladder Length Series noise expected to dominate for narrow (50 m) pitch sensors above ~25 cm long
PSpice predictions End readout (include network effects) Center tap First-Pass Results vs. Expectations (old…) Expected for end readout (Spieler formulation) Observed: End readout Center tap But: need to add in amplifier noise…
Observed noise Simulation, with LSTFE series and parallel noise Network values: 65 pF; 3700 Simulation, with LSTFE series noise only Include realistic feedback network; measured LSTFE-I noise (LSTFE-II now known to be similar) Good agreement; significantly less than naïve expectation Need to look at “center-tap” readout next.
Wrap-Up Time-Over-Threshold Readout (LSTFE) Second prototype under study in lab; functionality looks good (except for power cycling) Long Ladder Readout Noise: Measurements show much lower noise than naïve (lumped-element) analysis. Now confirmed with simulation promising for long-ladder solutions. Non-Prompt Tracks with SiD: Extended radial range of stau decay kinks from 21-46 cm to 6-46 cm, maintaining good efficiency and purity. Exploring 46-71 cm range.