1. Scintillator HCAL read-out and calibration Felix Sefkow TILC08 at Sendai, Japan March 4, 2008

2. Felix Sefkow TILC08, Sendai, March 3-7, 2008Scintillator HCAL readout & calibration 2 Outline Test beam Calibration and monitoring methods New read-out electronics under test

3. Felix Sefkow TILC08, Sendai, March 3-7, 2008Scintillator HCAL readout & calibration 3 Scintillator HCAL prototype Steel scintillator sandwich 38 layers, 2cm steel absorbers Scintillator tiles 3x3x0.5cm 3 7608 SiPMs (MEPhI / Pulsar) Versatile calibration and monitoring system

4. Felix Sefkow TILC08, Sendai, March 3-7, 2008Scintillator HCAL readout & calibration 4 Test beam experience Established the scintillator SiPM technology on large scale (7608 SiPMs) –Robust and stable operation, 95% up-time, 1.6% dead channels (mostly solder) –Noise occupancy 10 -3 as expected, 0.8 MIP = 25 MeV / hit –Imaging capability nicely demonstrated, millions of events collected

5. Felix Sefkow TILC08, Sendai, March 3-7, 2008Scintillator HCAL readout & calibration 5 Analysis ongoing Electromagnetic showers: Verify detector model and calibration procedures Hadrons: test simulation models and particle flow performance N.WattimenaO. Wendt Ongoing thesis work

6. Felix Sefkow TILC08, Sendai, March 3-7, 2008Scintillator HCAL readout & calibration 6 Next: technical prototype Integration issues –Readout architecture –Ultra-low power ASICs –Calibration system –Tile and SiPM integration –Absorber mechanics with minimal cracks See V.Zutshi’s talk Feed-back from test beam essential –Calibration concept Goal: A compact and realistic (i.e. scaleable) scintillator HCAL structure with embedded electronics

7. Felix Sefkow TILC08, Sendai, March 3-7, 2008Scintillator HCAL readout & calibration 7 Calibration Pixel photo-diode is non-linear: need 2 reference scales –MIP: muon test beam –Gain: low intensity LED light Energy deposition –E[MIP] = A / A MIP * f ( A / A pixel ) Saturation correction f –From test bench Gain

8. Felix Sefkow TILC08, Sendai, March 3-7, 2008Scintillator HCAL readout & calibration 8 Temperature and voltage Signal (charge) depends on gain and Geiger efficiency: A ~ ε * G Both depend on overvoltage  U = U bias – U breakdown Breakdown voltage U breakdown depends on temperature Figures: S.Uozumi For x = A, G: dx/dT = - dx/dU * dU breakdown /dT Ratio of amplitude and gain coefficient is the same for U and T dependence

9. Felix Sefkow TILC08, Sendai, March 3-7, 2008Scintillator HCAL readout & calibration 9 Voltage dependence Measured for A and G at ITEP test bench, stored in data base Reproduced in CERN test beam set-up ITEP CERN This and following slides: N.Feege, A.Kaplan

10. Felix Sefkow TILC08, Sendai, March 3-7, 2008Scintillator HCAL readout & calibration 10 Temperature dependence Measured in test-beam only Red: low  U group

11. Felix Sefkow TILC08, Sendai, March 3-7, 2008Scintillator HCAL readout & calibration 11 Amplitude and gain coeff.s Check model: dA/dT / dG/dT = dA/dU / dG/dU ? Mean (norm) -4.0 -1.7 5.6 -2.6 %/(K or 0.1V) RMS (norm) 2.8* 0.4 0.8 0.4 mean spread

12. Felix Sefkow TILC08, Sendai, March 3-7, 2008Scintillator HCAL readout & calibration 12 Correction methods Temperature correction: x = x 0 [ 1 + dx/xdT (T-T 0 ) ], x = A, G –Instantaneous, but non-local Gain correction A = A 0 [ 1 + { dA/AdU / dG/GdU } (G-G 0 ) ] –Local, but not instantaneous Combination of both – all to be tried –Success not guarenteed – may introduce additional errors Voltage adjustment U = U 0 + ( G – G 0 ) / dG/dU –More radical, but most effective

13. Felix Sefkow TILC08, Sendai, March 3-7, 2008Scintillator HCAL readout & calibration 13 Bias working point Critical for signal / noise optimization, not recoverable offline N.D’Ascenzo Derived from Light yield = A/G

14. Felix Sefkow TILC08, Sendai, March 3-7, 2008Scintillator HCAL readout & calibration 14 Voltage adjustment Test beam preparation at DESY vs. CERN Required bias adjustment from observed gain shift (average per layer) observed Temperature-corrected Voltage-corrected (prediction)

15. Felix Sefkow TILC08, Sendai, March 3-7, 2008Scintillator HCAL readout & calibration 15 Auto-calibration With single photo-electron (pixel) peaks the pixel photo-diode provides its own reference scale Promising tool for monitoring temperature- induced response variations Opens possibilities for further simplification of calorimeter design –No external reference –Small amplitudes –Loose stability requirements Stability of saturation correction –Under study, so far OK

16. Felix Sefkow TILC08, Sendai, March 3-7, 2008Scintillator HCAL readout & calibration 16 LED on board Attractive option - if auto- calibration of SiPM sufficient Proof-of-principle test borad, check for cross-talk, uniformity, dynamic range,… M.Reinecke, DESY First tests: electrical cross-talk small

17. Felix Sefkow TILC08, Sendai, March 3-7, 2008 Scintillator HCAL readout & calibration 17 Estimate Crosstalk Mathias ReineckeEUDET annual meeting – Paris8.-10. Oct. 2007 Scope in averaging mode Crosstalk ≈ 2.5% Consistent with optical XT Light in Tile 1 Crosstalk to tile 2 and tile 4 ≈40mV ≈1mV Very encouraging Ongoing optimization and measurements (ligt uniformity, dyn. range,…)

18. Felix Sefkow TILC08, Sendai, March 3-7, 2008Scintillator HCAL readout & calibration 18 LEDs: to be continued Uniformity not yet sufficient (LED to LED variation) –Do not want to –remote- control or tune each driver –Discussions with manufacturer –Could in principle be solved with pre-selection Driver uniformity? Dynamic range – the more, the merrier Systematic investigation using CALICE DAQ –ILC-SiPM ASIC and CRC A.Lucaci, S.Weber

19. Felix Sefkow TILC08, Sendai, March 3-7, 2008Scintillator HCAL readout & calibration 19 New ASIC on the test benches Auto-triggering and time measurements ADC and TDC integrated Power pulsing, low (continuous) power DAC LAL DESY

20. Felix Sefkow TILC08, Sendai, March 3-7, 2008Scintillator HCAL readout & calibration 20 Analogue part Gain and pedestal uniformity good (as expected from SiGe 0.35) Somewhat smaller gain and larger noise than in simulation L.Raux, S.Callier

21. Felix Sefkow TILC08, Sendai, March 3-7, 2008Scintillator HCAL readout & calibration 21 Input DAC SiPM bias adjustment Must be extremely low power (~10µW), since always on! Non-linearity ~2%, just OK L.Raux, S.Callier

22. Felix Sefkow TILC08, Sendai, March 3-7, 2008Scintillator HCAL readout & calibration 22 Autotrigger Fast shaper (10ns) and discriminator Can triger on 0.5 p.e. Small threshold dispersion Cross-talk 0.3% Time walk 6ns L.Raux, S.Callier

23. Felix Sefkow TILC08, Sendai, March 3-7, 2008Scintillator HCAL readout & calibration 23 SPIROC meets SiPM Still a lot of tests to be done Understand response with auto-trigger, control thresholds Internal ADC not yet usable R.Fabbri, B.Lutz

24. Felix Sefkow TILC08, Sendai, March 3-7, 2008Scintillator HCAL readout & calibration 24 Summary A nice concept for the 2 nd generation HCAL prototype with embedded electronics and calibration system is emerging Readout with many new features –Auto-trigger (zero-suppression) –On-chip digitization –Time measurement –Power pulsing Auto-calibration of PPDs is a very powerful tool – but remains a challenge for sensor and electronics design Test beam experience vital and rich source to develop calibration concept

25. Felix Sefkow TILC08, Sendai, March 3-7, 2008 Scintillator HCAL readout & calibration25 Back-up slides

26. MC Felix Sefkow TILC08, Sendai, March 3-7, 2008 Scintillator HCAL readout & calibration 26 Integrated layer design Sector wall Reflector Foil 100µm Polyimide Foil 100µm PCB 800µm Bolt with inner M3 thread welded to bottom plate SiPM Tile 3mm HBU Interface 500µm gap Bottom Plate 600µm ASIC TQFP-100 1mm high Top Plate 600µm steel Component Area: 900µm high HBU height: 6.1mm (4.9mm without covers => absorber) Absorber Plates (steel) Spacer 1.7mm Top Plate fixing DESY integrated