Commissioning of the Silicon Drift Detector of the ALICE experiment - PowerPoint PPT Presentation

Silicon Drift Detector of ALICE Calibration Conclusions Commissioning of the Silicon Drift Detector of the ALICE experiment at the LHC Emanuele Biolcati for ALICE collaboration Dipartimento di Fisica dell’Universit` a di Torino INFN Torino XLVII International Winter Meeting on Nuclear Physics Bormio - Jan. 26-30, 2009 1 Emanuele Biolcati Commissioning of the ALICE Silicon Drift Detector

Silicon Drift Detector of ALICE Detector Calibration Physics Conclusions Outlines Silicon Drift Detector of ALICE 1 Detector Physics Calibration 2 Front-end electronics: noise and gain SDD parameter: drift speed SDD response: charge collection Conclusions 3 2 Emanuele Biolcati Commissioning of the ALICE Silicon Drift Detector

Silicon Drift Detector of ALICE Detector Calibration Physics Conclusions ALICE experiment @ LHC 3 Emanuele Biolcati Commissioning of the ALICE Silicon Drift Detector

Silicon Drift Detector of ALICE Detector Calibration Physics Conclusions Pb-Pb event @ LHC (simulation) 4 Emanuele Biolcati Commissioning of the ALICE Silicon Drift Detector

Silicon Drift Detector of ALICE Detector Calibration Physics Conclusions The Inner Tracking System Pixel (SPD) 240 sensitive volumes Drift (SDD) 260 sensitive volumes Resolution Strip double-side (SSD) Detector x loc [ µ m ] z loc [ µ m ] occupancy [%] 1698 sensitive volumes SPD 12 70 1.5 - 0.4 SDD 38 28 2.5 - 1.0 SSD 20 830 4.0 - 3.3 5 Emanuele Biolcati Commissioning of the ALICE Silicon Drift Detector

Silicon Drift Detector of ALICE Detector Calibration Physics Conclusions ALICE Silicon Drift Detector Anodes 256 × 2 Cathodes 291 × 2 Anode pitch 294 µ m Cathode pitch 120 µ m HV (nominal) -1800 V 6 Emanuele Biolcati Commissioning of the ALICE Silicon Drift Detector

Silicon Drift Detector of ALICE Detector Calibration Physics Conclusions ALICE Silicon Drift Detector Anodes 256 × 2 Cathodes 291 × 2 Anode pitch 294 µ m Cathode pitch 120 µ m HV (nominal) -1800 V 6 Emanuele Biolcati Commissioning of the ALICE Silicon Drift Detector

Silicon Drift Detector of ALICE Detector Calibration Physics Conclusions The SDD module front back 7 Emanuele Biolcati Commissioning of the ALICE Silicon Drift Detector

Silicon Drift Detector of ALICE Detector Calibration Physics Conclusions The SDDs inside the ITS 8 Emanuele Biolcati Commissioning of the ALICE Silicon Drift Detector

Silicon Drift Detector of ALICE Detector Calibration Physics Conclusions Physical motivations of ITS (I) Primary vertex reconstruction → Secondary vertex reconstruction Track impact parameter 9 Emanuele Biolcati Commissioning of the ALICE Silicon Drift Detector

Silicon Drift Detector of ALICE Detector Calibration Physics Conclusions Physical motivations of ITS (II) Complement TPC tracking Standalone tracking 10 Emanuele Biolcati Commissioning of the ALICE Silicon Drift Detector

Silicon Drift Detector of ALICE Front-end electronics: noise and gain Calibration SDD parameter: drift speed Conclusions SDD response: charge collection Outlines Silicon Drift Detector of ALICE 1 Detector Physics Calibration 2 Front-end electronics: noise and gain SDD parameter: drift speed SDD response: charge collection Conclusions 3 11 Emanuele Biolcati Commissioning of the ALICE Silicon Drift Detector

Silicon Drift Detector of ALICE Front-end electronics: noise and gain Calibration SDD parameter: drift speed Conclusions SDD response: charge collection Baseline and noise 4 readout chips per SDD semi-module ⇒ different response function for each chip ⇓ equalization of the baseline calculation of noise per anode (133k) extimation of the common mode noise tag of good/bad anodes 12 Emanuele Biolcati Commissioning of the ALICE Silicon Drift Detector

Silicon Drift Detector of ALICE Front-end electronics: noise and gain Calibration SDD parameter: drift speed Conclusions SDD response: charge collection Baseline and noise distribution Calibration run results baseline equalized to 20 ADC raw noise ≃ 2.3 ADC signal peak by a MIP (close to the anodes) ≃ 120 ADC w/o common mode noise ≃ 1.9 ADC good anodes ≃ 99 . 5% 13 Emanuele Biolcati Commissioning of the ALICE Silicon Drift Detector

Silicon Drift Detector of ALICE Front-end electronics: noise and gain Calibration SDD parameter: drift speed Conclusions SDD response: charge collection Baseline and noise stability (during cosmic runs of 2008) 14 Emanuele Biolcati Commissioning of the ALICE Silicon Drift Detector

Silicon Drift Detector of ALICE Front-end electronics: noise and gain Calibration SDD parameter: drift speed Conclusions SDD response: charge collection Gain measurement test pulse = signal self-generated by the amplifier ⇓ measurement of the gain of the amplification chain 15 Emanuele Biolcati Commissioning of the ALICE Silicon Drift Detector

Silicon Drift Detector of ALICE Front-end electronics: noise and gain Calibration SDD parameter: drift speed Conclusions SDD response: charge collection Gain stability (during cosmic runs of 2008) gain ≃ 1.28 ADC/DAC variation due to a change of the ADC sampling rate (from 40 MHz to 20 MHz) 16 Emanuele Biolcati Commissioning of the ALICE Silicon Drift Detector

Silicon Drift Detector of ALICE Front-end electronics: noise and gain Calibration SDD parameter: drift speed Conclusions SDD response: charge collection The importance of the drift speed � v drift = µ e E µ e ∝ T ( K ) − 2 . 4 ALICE SDD requirement: σ x ∼ 40 µ m ⇓ drift speed very sensitive to temperature variations ⇓ need to measure ( frequently ) the drift speed value in many positions of the sensitive region of the detector 17 Emanuele Biolcati Commissioning of the ALICE Silicon Drift Detector

Silicon Drift Detector of ALICE Front-end electronics: noise and gain Calibration SDD parameter: drift speed Conclusions SDD response: charge collection Drift speed calculation 3 rows of 33 MOS injectors per semi-module ⇓ drift speed calculated in 33 positions (from linear fit of 3 points) ⇓ distribution vs anode position reflects temperature effects 18 Emanuele Biolcati Commissioning of the ALICE Silicon Drift Detector

Silicon Drift Detector of ALICE Front-end electronics: noise and gain Calibration SDD parameter: drift speed Conclusions SDD response: charge collection Drift speed vs module 19 Emanuele Biolcati Commissioning of the ALICE Silicon Drift Detector

Silicon Drift Detector of ALICE Front-end electronics: noise and gain Calibration SDD parameter: drift speed Conclusions SDD response: charge collection Drift speed vs time 20 Emanuele Biolcati Commissioning of the ALICE Silicon Drift Detector

Silicon Drift Detector of ALICE Front-end electronics: noise and gain Calibration SDD parameter: drift speed Conclusions SDD response: charge collection Reconstruction of a cosmic ray in the ITS before calibration after calibration Cosmic charge cluster → 21 Emanuele Biolcati Commissioning of the ALICE Silicon Drift Detector

Silicon Drift Detector of ALICE Front-end electronics: noise and gain Calibration SDD parameter: drift speed Conclusions SDD response: charge collection Charge distribution in SDD Cluster distribution from cosmic tracks (fitted with a convolution of Landau+Gaussian) 22 Emanuele Biolcati Commissioning of the ALICE Silicon Drift Detector

Silicon Drift Detector of ALICE Front-end electronics: noise and gain Calibration SDD parameter: drift speed Conclusions SDD response: charge collection Data vs simulation most probable value for energy deposition of a MIP in 300 µ m of silicon ⇓ conversion factor from ADC units to keV 23 Emanuele Biolcati Commissioning of the ALICE Silicon Drift Detector

Silicon Drift Detector of ALICE Front-end electronics: noise and gain Calibration SDD parameter: drift speed Conclusions SDD response: charge collection Charge vs drift distance dependence on the distance between impact point and the collection anodes ⇓ possible reasons: traps in Silicon, signal tails cut by threshold ⇓ offline correction of the measured charge value 24 Emanuele Biolcati Commissioning of the ALICE Silicon Drift Detector

Silicon Drift Detector of ALICE Front-end electronics: noise and gain Calibration SDD parameter: drift speed Conclusions SDD response: charge collection Charge vs drif distance: data and simulation 25 Emanuele Biolcati Commissioning of the ALICE Silicon Drift Detector

Silicon Drift Detector of ALICE Front-end electronics: noise and gain Calibration SDD parameter: drift speed Conclusions SDD response: charge collection Offline correction 26 Emanuele Biolcati Commissioning of the ALICE Silicon Drift Detector

Silicon Drift Detector of ALICE Calibration Conclusions Outlines Silicon Drift Detector of ALICE 1 Detector Physics Calibration 2 Front-end electronics: noise and gain SDD parameter: drift speed SDD response: charge collection Conclusions 3 27 Emanuele Biolcati Commissioning of the ALICE Silicon Drift Detector