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Tracking R&D at SCIPP: Charge Division with Microstrips Ladder Length Limitations

This presentation discusses the use of charge division with microstrips for tracking, focusing on the limitations of ladder length in practical detectors. The simulation results show that network effects can reduce the longitudinal resolution, but the results apply to multi-strip sensors as well. The presentation also explores the limitations of long ladder lengths and suggests design considerations. The observed results are compared to the expected results, and the potential for wider strips or center-readout is discussed.

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Tracking R&D at SCIPP: Charge Division with Microstrips Ladder Length Limitations

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  1. Tracking R&D at SCIPP: • Charge Division with Microstrips • Ladder Length Limitations 2011 Linear Collider Workshop, Granada, Espana 26-30 September 2011 Bruce Schumm SCIPP/UC Santa Cruz

  2. But: practical detectors aren’t isolated strips. Include two nearest-neighbors in simulation: Network ef-fects lead to ~5% reduction in longitudinal resolution, but anti-correlation reduces from 60% to 40%  Single-strip results also apply for multi-strip sensors, essentially unchanged.

  3. Areas of Activity

  4. Limitations on Ladder Length Long ladders with precise resolution is unique to the ILC. What constrains ladder length? What limitations arise for maximal lengths?  Design considerations

  5. Typical electronics characterization: e vs. capacitive load S:N ~ 16:1 ~ 1m  Suggest ladder lengths > 1m easily achieved

  6. Standard Form for Readout Noise; Lumped Element Approximation (Spieler) Series Resistance Parallel Resistance Amplifier Noise (parallel) Amplifier Noise (series) Dominant term for long ladders (grows as L3/2) Fi , Fv are signal shape parameters that can be determined from average scope traces.

  7. Expected Noise vs. Ladder Length “Lumped element” Load Series noise expected to dominate for narrow (50 m) pitch sensors above ~25 cm long

  8. Lumped approximation implies significant limitations due to strip resistance • How accurate is this approximation? • Test with extensible, ILC-like ladder • SiD 50 m pitch “Charge Division” Sensors • 4.75 cm strip length • 287  per strip (~ 8 m width) • 5.2 pF per strip

  9. Sensor “Snake” Sensor “Snake”: Read out up to 13 daisy-chained 4.75 cm sensors (with LSTFE-1 ASIC) LSTFE1 chip on Readout Board Can read out from end, or from middle of chain (“center-tap”)

  10. Naïve Expectation vs. Observation “Lumped” Load Observed

  11. Exploring Long-Ladder Noise Results To explore/understand difference between expected and observed, a full network simulation was developed in SPICE

  12. Comparison with Full Network Model Full network simulation

  13. Maximal ladder length: Operating Point Efficiency 1-Occupancy 99.9% efficient 00.1% occupancy Maximal ladder length: 14.05 * 4.75cm = 67 cm Trigger Threshold

  14. Resolution v. Readout Threshold for Maximal Ladder Length Readout Threshold

  15. Typical electronics characterization: e vs. capacitive load Operating Point for ½ Maximal Ladder Length Trigger Threshold

  16. Typical electronics characterization: e vs. capacitive load Resolution for ½ Maximal Ladder Length Readout Threshold

  17. Further Reduction: “Center-Tapping” Center-Tap Observed Center-Tap Simulated  NIM paper in preparation

  18. Wrap-Up • Charge Division: • Resolution of ~6mm seems possible for 10cm ladder • Of interest in reconstructing jets at Ecm = 500 GeV • Long Ladder Readout Noise: • Strip resistance less than naively expected, but still dominant • Limits ladder length to ~70 cm for conventional readout and sensors • Think about wider, thicker strips and/or center-readout

  19. (No) Backup Slides

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