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Beetle; a front-end chip for LHCb VELO

Beetle; a front-end chip for LHCb VELO. ASIC lab Heidelberg. A collaboration between the ASIC-lab Heidelberg, NIKHEF Amsterdam and the University of Oxford. 25 stations (50 Si planes). Outline. Vertex detector Silicon strip detectors Beetle architecture Radiation hardness

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Beetle; a front-end chip for LHCb VELO

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  1. Beetle;a front-end chip for LHCb VELO ASIC lab Heidelberg A collaboration between the ASIC-lab Heidelberg, NIKHEF Amsterdam and the University of Oxford IWoRID; Niels van Bakel

  2. 25 stations (50 Si planes) Outline • Vertex detector • Silicon strip detectors • Beetle architecture • Radiation hardness • Measured characteristics • Conclusions IWoRID; Niels van Bakel

  3. The Vertex detector • Provide production and decay • vertex information • Detector resolution ~8 m • 200000 strip lines • Sampling frequency 40 MHz • 1 MHz accepted triggers; no dead • time if readout < 900 ns per event • Required S/N > 14 (10 pF load) • Power consumption < 6 mW/channel • Peaking time  25 ns • Pulse spill-over < 30 % after 25 ns • Dynamic range ± 10 MIP Decay distance resolution  120 m IWoRID; Niels van Bakel

  4. 5 cm Silicon strip detector • Detector capacitance 5-30 pF • Yearly radiation dose at 8 mm • ~11014 [1 MeV neutrons/cm2] • 300 (200) m thick • 40-60 m inter strip distance • 1 MIP creates ~22000 electrons • LHCb requirements depend on • efficiency, technical limits, costs • Energy loss distribution obeys • a Landau function • Non ionizing energy loss is expected to • be the major source of radiation damage • of the Silicon detector • Fully depleted IWoRID; Niels van Bakel

  5. Beetle architecture 128 channels test channel dummy channel pipeline readout Pipeline 128186 preamp shaper multiplexer 324 Readout via 2 m twisted-pair cable, repeater card Multi event buffer IWoRID; Niels van Bakel

  6. Beetle layout • Dimensions 6.1 mm  5.5 mm • Pitch input pads 41.2 m • Positive supply 2.5 V • Analog output driver • ~ 50 mV/MIP • No dead channels allowed • < 0.1 % dead pipeline cells 4 outputs front-end amplifiers pipeline multiplexers pipeline readout amplifiers 128 analogue inputs pipeline readout control I2C IWoRID; Niels van Bakel

  7. Gate oxide Field oxide Leakage current Radiation hard design Tolerable irradiation dose > 10 Mrad in 5 years • Obtain radiation hardness with: • Tox < 10 nm : tunneling decreases the • trapped ions in the gate-oxide • Enclosed nMOS prevents large • leakage currents • Guardrings around nMOS Single event upset (SEU) triggered by single particles; tests needed Control logic protected by SEU: use triple redundant flip-flops with majority encoding IWoRID; Niels van Bakel

  8. Vout [V] time [ns] Radiation tests (TID) Test with X-ray facility at CERN Total ionizing dose results in gate bias voltage shifts Beetle1.1 showed full functionality up to 30 Mrad (15 LHCb years): full trigger / readout functionality full slow control functionality performance degradations are small IWoRID; Niels van Bakel

  9. ENC measurements ENC behaviour of the new Beetle front end(measured on a test chip): 449 e- + 46.8 e-/pF The channel thermal noise dominates the noise for an input transistor with a large area: 45.3e-/pF (calculated) 1 MIP in the detector generates 22000 electrons IWoRID; Niels van Bakel

  10. Pulse shape • Measured • 15 ns rise time • 20 % spillover • HSPICE calculated • pulse (solid line) IWoRID; Niels van Bakel

  11. Beetle Beam telescope R and Phi 130 mm 40 mm Track 80 mm The Beetle in a Testbeam • Scintillator trigger • Tracks used • 40 MHz sampling rate • Two Beetle chips bonded • Aligned with ~30 m • precision IWoRID; Niels van Bakel

  12. Testbeam results 17.5 ns rise time 21.3 % spill over Preliminary Sstrip/Nstrip = 13.3 Scluster/Nstrip = 15.3 IWoRID; Niels van Bakel

  13. Conclusions and outlook • The Beetle1.1 fulfills the LHCb requirements: • rise time • spillover • S/N • sample frequency • radiation hardness • Additional data with 16 Beetle1.1 chips on a • VELO Beetle hybrid bonded to a silicon detector • Improved Beetle1.2 available since July (see LEB) • Beetle also considered for the Inner tracker, RICH • detector and the pile-up veto detector (LHCb) IWoRID; Niels van Bakel

  14. Residuals IWoRID; Niels van Bakel

  15. Landau? IWoRID; Niels van Bakel

  16. RF tests? IWoRID; Niels van Bakel

  17. Analogue readout? IWoRID; Niels van Bakel

  18. Comparator? left: - signal pulse shape - comparator output right: - binary readout (4 consecutive BX) track mode Comparator output level shifter is too slow  causes spill-over to the second BX  Beetle 1.2: has now an output buffer pulse mode IWoRID; Niels van Bakel

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