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CMS ELECTROMAGNETIC CALORIMETER

CMS ELECTROMAGNETIC CALORIMETER. OVERVIEW. Bernard ILLE. IPN Lyon. Int. Conf. on instrumentation for colliding beam physics Hamamatsu, Japan, 15-19 November 1999. CMS PHYSICS. CMS ( C ompact M uon S olenoid) is a general purpose detector.

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CMS ELECTROMAGNETIC CALORIMETER

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  1. CMS ELECTROMAGNETIC CALORIMETER OVERVIEW Bernard ILLE IPN Lyon Int. Conf. on instrumentation for colliding beam physics Hamamatsu, Japan, 15-19 November 1999

  2. CMS PHYSICS CMS (Compact Muon Solenoid) is a general purpose detector. It will be one of the 4 experiments on the LHC : pp and heavy ions collider with Ecm=14 TeV/charge • First run in 2005, for 10 years • Luminosity : 30 fb-1 for 3 years • Physics : • Particles searches : Higgs, SUSY • B physics • Heavy ions

  3. CMS ECAL PERFORMANCE Benchmark for low luminosity : Higgs physics : Needs high resolution : AND • magnetic field of 4 T • crossing at 40 MHz • radiations : 0.15-0.3 Gy/h in the barrel, up to 15 Gy in the endcaps Choice of lead tungstate crystals (fast, rad hard, density) + Avalanche PhotoDiodes (APD) in barrel (B not sensitive, gain) + Vacuum PhotoTriodes (VPT) in endcaps (rad hard, gain)

  4. PHYSICS 130 GeV Higgs in 2 photons

  5. LEADTUNGSTATE : PbWO4 ADVANTAGES • 26 radiation lengths in 23 cm of material (barrel), endcaps : 22 cm • moliere radius of 21.9 mm, density of 8.2 g/cm3 COMPACT CALORIMETER • 85% of the light in 20 ns, l ~ 420 nm • radiation hardness : saturated loss < 5% for 0.15 Gy/h BUT • LOW Light Yield : about 60 photons/MeV for a crystal • readout with APDs (gain 50) and VPTs (gain 6-8 in 4T) • low run temperature : 16-18 oC to maximise LY • Temperature sensitivity of crystals and APDs (~ -2%/oC) requires a 0.1 oC temperature stabilisation.

  6. PHOTODETECTORS APD gain curve

  7. PHOTO DETECTORS : APDs and VPTs • APDs at present time (Hamamatsu): • no magnetic field sensitivity • gain 50, with a voltage sensitivity of 3%/V • temperature sensitivity of -2.3%/oC • quantum efficiency of 70% • area of 25 mm2 2 APDs 50 mm2 and 4 pe/MeV • radiations increase bulk current electronic noise 2 after 10 years : keep good resolution. • Capacitance ~ 80 pF Forseen : C ~ 80 pF, 1/M.dM/dV ~ 2-3%/V • VPTs(Hamamatsu, RIE St. Petersbourg, Electron Tubes Ltd) : • more resistant to radiations than APDs, 250 mm2 • drop of gain by a factor 2 in axial 4 T magnetic field

  8. PHOTODETECTORS READOUT : P.A. + Sample ADC + optic link RAD HARD ELECTRONIC (DMILL, HARRIS) with low power dissipation: • Transimpedance P.A. • FPU : Switches of gains (1,4,8,32) to have better resolution • Sampling ADC : 40 MHz, 4096 channels (A.D. 9042) • One serialiser per channel (800 Mbit/s) to bring out the SADC samples with digital optic link

  9. ECAL STRUCTURE BARREL GRANULARITY OF 360 (f) x 170 (q) crystals A submodule = 2x5 crystals in reflective alveola, + tablet A module = 10x4 (5) submodules = 400 (500) crystals, + grid + basket A supermodule = 4 modules 36 supermodules = 61200 crystals ENDCAPS 7810x2 crystals grouped in supercrystals (5x5 alveolar unit) TOTAL : 76820 crystals

  10. Calibration and Monitoring • TEST BEAM CALIBRATION OF ALL CRYSTALS (CERN) in their modules, before detector installation • LIGHT MONITORING TO KNOW CRYSTALS AND READOUT EVOLUTION • CALIBRATION IN SITU WITH PHYSICS E/p calibration with electrons measured by tracker Within 35 days at low luminosity Mapping of all crystals Intercalibration better than 0.3 %

  11. MONITORING

  12. CONCLUSION • PERFORMANCES LIKE TDR RECOMMANDATIONS • PRODUCTION OF CRYSTALS STARTED • PHOTODETECTORS R&D IS NEARLY FINISHED, PRODUCTION IN 2000 • RAD HARD ELECTRONIC READOUT WILL BE FULLY TESTED IN 2000 • SM1 WILL BE BUILT IN 2000 • CALIBRATION of FIRST SMs WILL BEGIN IN 2001

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