26/May/2008Calor LHCb Preshower(PS) and Scintillating pad detector (SPD): commissioning, calibration, and monitoring Eduardo Picatoste Universitat de Barcelona on behalf of the LHCb Collaboration XIII International Conference on Calorimetry in High Energy Physics CALOR May Pavia, Italy 26/May/2008Calor OUTLINE Introduction PS/SPD design Commissioning Initial calibration LED measurements Time alignment Cosmics measurements Calibration Monitoring Summary 26/May/2008Calor (1) Introduction: LHCb detector LHCb calorimeter: SPD/PS (present talk) ECAL (Irina Machikhiliyan talk today at 14:00h) HCAL (Iouri Guz talk on Thursday at 9:20h) Trigger (Regis Lefevre on Thurday at 12:30h) OT VELO RICH-1 TT IT Magnet Muon Stations M2-M5 -5m 5m y 10m 15m 0m HCAL ECAL PS/SPD Calorimeters RICH-2 M1 26/May/2008Calor (1) SPD/PS detector role Preshower (PS) and Scintillator Pad Detector (SPD): e-e- SPD LEAD PS ECAL 2.5 radiation lengthes SPD PS Lead 26/May/2008Calor (2) PS/SPD design: readout electronics PMT 64ch SPD VFE CLOCK ctrl x100 x16 Digital PMT 64ch PS VFE CLOCK Analogue FE Control Board Trigger path DAQ path x cells Optical fibers LED DETECTORVFE boxesFE crates ~20 m (top) ~30 m bottom 6016 cells Multiplicity Trigger x100 Crate: 14 FE + 2 CB 26/May/2008Calor (2) PS/SPD design VFE electronic boxes VFEs VFE electronic box VFE electronic boxes Cable chain Crate OUTER (cell 12x12cm 2 ) MIDDLE (cell 6x6cm 2 ) INNER (cell 4x4cm 2 ) 26/May/2008Calor (3) Commissioning: initial calibration Detector cells calibration before installation: Number of photoelectrons per MIP on each cell Calibrated using cosmics Detector modules placed horizontally # cells Nphe/MIP Super-module cells with number of fotoelectrons per MIP: 26/May/2008Calor (3) Commissioning: initial calibration PS: Pedestals: Mean ~140 ADC counts lower than 300 ADC counts Noise: Lower than 1.2 ADC counts (MIP is ~10 ADC counts) SPD: Offset: All channels have been measured at values similar to the lab Noise: Lower than 3mV (signal is 100mV/MIP) # ch 26/May/2008Calor Data (3) Commissioning: time alignment Phases of signals between boards can be adjusted to time align between them. The phases to be aligned: (1) VFE, the integration starting time. Depends on data cable length and integration clock. (2) VFE-ADC, the sampling of VFE signal by the ADC. (3) ADC-FE, the sampling of ADC signal by the FE-PGA. VFE, VFE-ADC, and ADC-FE are correlated. The game consists in choosing the authorised regions. Signal PMT 64ch VFE FE... Time Delay Unit ADC Experiment clock ADC-FE Time Delay Unit FEPGA Time Delay Unit Integration CLOCK VFE VFE-ADC Phases to be set within PS boards: VFE boxesFE cratesDET. 26/May/2008Calor ) Sample VFE integration, fixed ADC-FE 2) Re-sample in FEB FE-PGA, fixed VFE plateau Validity diagrams against ADC phase based on FE & VFE pedestal signals For all FEB/VFE C side VFE VFE-ADC ADC-FE VFE-ADC (3) Commissioning: electronics time alignment plateau 26/May/2008Calor VFE boxesFE cratesDET. Data (1) VFE : phase applied to the signal integration clock. It depends on the clock cable and optical fiber lengths. (2) VFE-FE : Read VFE data on FE. Depends on data cable length and integration clock. PMT 64ch VFE Integration CLOCK ctrl FE CB... ASIC LVDS mux Control... Time Delay Unit Time Delay Unit Regs Experiment clock VFE-FE VFE VFE-FE Phases to be set within SPD boards: BER test shows forbidden s: (3) Commissioning: electronics time alignment 26/May/2008Calor (3) Commissioning: LED measurements All PS and SPD detectors have been measured using LED system. As an illustration here is the 2D display of the detector showing the ADC value peak measured in the LED Flash with pedestal substracted. LED signals are varying on a large scale. Used for: detect dead channels check the detector stability Coarse time alignment 26/May/2008Calor (3) Commissioning: cosmics measurements Cosmic measurements have been taken using LHCb calorimeter Rate ~16 Hz. Data acquisition feature: +/-7 previous/next bunch-crossing data can be stored. Analyses of data are/will be providing: An initial time alignment between subdetectors. Identification of problems such as: Mapping issues: miscabling, mislabelling. Identify working/non-working channels. Data taking strategy: Trigger: HCAL and ECAL coincidence using the full L0 trigger path of the experiment Get previous/next readings for bunch-crossing alignment 26/May/2008Calor (3) Commissioning: cosmics measurements Cosmic event: SPD PS ECALHCAL 26/May/2008Calor (3) Commissioning: cosmics measurements Cosmics accumulated signal on some of the outer part: SPD PS x x yy ADC counts Cosmics multiplicity above threshold depending on bunch crossing (time slot): 26/May/2008Calor (3) Commissioning: cosmics measurements x y Cosmic event with mapping problem Same cosmic event with corrected mapping x y ECALPS 26/May/2008Calor E (MeV) (4) Calibration: PS Pedestals: Occupancy is low (10%), so run offline pedestal measurements on data To be performed periodically depending on stability Single pions energy diposition on PS: Adjust of gain corrective factors (MIP calibration): Set PMT expected voltage Particles at MIP needed. Identify channel with highest MIP value and tune PMT voltage so 1MIP = 10 ADC counts. Adjust all channel gain corrective factors so all channels present 10 ADC counts/MIP To be performed periodically depending on stability MIP 26/May/2008Calor (4) Calibration: SPD threshold scan SPD is has binary readout electronics: Output = 0/1 if signal below/over programmed threshold Threshold scan: Fix the threshold value. Take N events. Repeat for increasing values of threshold. Represent number of ones obtained divided by N for each threshold value. Transition from 1 to 0 is a measure of the VFE channel input signal. The scan is useful to measure: Channel offset values LED signal Find MIP peak Threshold scan for one SPD channel: 26/May/2008Calor (4) Calibration: SPD Electronic offset: Threshold scan without signal Need ~1000 triggers x 128 steps To be performed periodically depending on stability Threshold values: MIP calibration Th-scan with particles Calculate differential output (ones with threshold between E and E+E) and adjust curve to MIP peak Needed time is ~30s x 20 threshold steps To be done at start-up, after that, very scarcely Useful also for obtaining: Gain Nphe (from MIP peak width) MIP (Preliminary) Optimal position of threshold: ~0.7 MIPs Energy deposition in a CELL: DIFFERENCIATE Threshold scan with particles: E (MeV) Events 26/May/2008Calor (5) Monitoring Events reconstructed online ~5 Hz Useful to monitor: Trigger rate stability on PS check ADC MIP value is constant PS coefficient of energy for ECAL correction Calibrate with e - (refine MIP calibration) Efficiency on charged particles identification of SPD Occupancy Check pedestal stability, ageing of the detector,noisy channels,... Cross-talk Dead channels Normalize to neighboring cells 26/May/2008Calor (6) Summary The PS/SPD is aimed at tagging the electric charge and the electromagnetic nature of the calorimeter clusters for the first level of trigger. Commissioning is done: Nphe/MIP of cells has been obtained from cosmics measurements. Pedestals (PS) or offset (SPD) and noise first values have been measured. Time alignment within PS/SPD boards has been studied. LED system have been used to check all channels. Cosmic measurements have been started. Data is under analysis for time alignment and to check the mapping. Calibration procedures are stablished. SPD requires threshold scans. Monitoring tools are being designed to check the performance of the detectors during data taking. 26/May/2008Calor (7) Extra slides 26/May/2008Calor OUTER (cell 12x12cm 2 ) MIDDLE (cell 6x6cm 2 ) INNER (cell 4x4cm 2 ) 64 channel groups VFE electronic boxes PS/SPD design VFE electronic boxes