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The Status of the CMS Electromagnetic Calorimeter

The Status of the CMS Electromagnetic Calorimeter. R M Brown On behalf of the CMS ECAL Group. Overview. Introduction Design objectives and technology choices Description and status: Crystals Photo-detectors On-detector electronics Off-detector electronics Laser monitoring system

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The Status of the CMS Electromagnetic Calorimeter

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  1. The Status of the CMS Electromagnetic Calorimeter R M Brown On behalf of the CMS ECAL Group Elba May 2006 R M Brown - RAL 1

  2. Overview • Introduction • Design objectives and technology choices • Description and status: • Crystals • Photo-detectors • On-detector electronics • Off-detector electronics • Laser monitoring system • Mechanical construction and assembly • Pre-shower • Intercalibration with cosmic muons • Construction and installation schedule • Summary Elba May 2006 R M Brown - RAL 2

  3. HCAL Muon chambers Tracker 4T solenoid ECAL Iron yoke Compact Muon Solenoid Total weight:12,500t Overall diameter:15m Overall length:21.6m Magnetic field:4T Elba May 2006 R M Brown - RAL 3

  4. Coloured histograms are separate contributing backgrounds for 1fb-1 ECAL design objectives High resolution electromagneticcalorimetry is central to the CMS design Benchmark process: H    m /m = 0.5[E1/E1  E2/E2   / tan(/2)] Where:E/E = a/E  b  c/E Aim (TDR): Barrel End cap Stochastic term: a= 2.7% 5.7% (p.e. stat, shower fluct, photo-detector, lateral leakage) Constant term: b= 0.55% 0.55% (non-uniformities, inter-calibration, longitudinal leakage) Noise: Low Lc= 155MeV 770MeV High L210MeV 915MeV (dq relies on interactionvertex measurement) (electronic, pile-up) Optimised analysis Elba May 2006 R M Brown - RAL 4

  5. Challenges & Choices Challenges: • Fast response (25ns between bunch crossings) • High radiation doses and neutron fluences (10 year doses: 1013 n/cm2, 1kGy at =0 2x1014 n/cm2, 50kGy at  =2.6) • Strong magnetic field (4 Tesla) • On-detector signal processing • 0/ discrimination • Long term reproducibility Choices: • Lead tungstate crystals • Avalanche photodiodes (Barrel), Vacuum phototriodes (Endcaps) • Electronics in 0.25 mm CMOS • Pb/Si Preshower detector in Endcap region • Laser light monitoring system Elba May 2006 R M Brown - RAL 5

  6. Fast light emission: ~80% in 25 ns Peak emission ~425nm (visible region) Short radiation length: X0 = 0.89cm Small Molière radius: RM = 2.10cm Radiation resistant to very high doses But: • Temperature dependence ~2.2%/OC • Stabilise to  0.1OC Formation and decay of colour centresin dynamic equilibrium under irradiation • Precise light monitoring system Low light yield (1.3% NaI) • Photodetectors with gain in mag field Leadtungstateproperties Elba May 2006 R M Brown - RAL 6

  7. Pb/Si Preshowers: 4 Dees (2/endcap) 4300 Si strips (~ 63x1.9 mm2) Tapered crystals Pointing ~ 3o from vertex Barrel: 36 Supermodules (18 perhalf-barrel) 61200 Crystals (34 types) – total mass 67.4t Dimensions: ~ 25x25x230 mm3 (25.8X0) DxD = 0.0175 x 0.0175 Endcaps: 4 Dees (2 per endcap) 14648 Crystals (1type) – total mass 22.9t Dimensions: ~ 30x30x220 mm3 (24.7X0) DxD = 0.0175 x 0.0175 ↔ 0.05 x 0.05 ECAL Layout Elba May 2006 R M Brown - RAL 7

  8. Crystal production • Crystal delivery determines ECAL Critical Path • Suppliers: • BTCP (Bogoroditsk, Russia) ~ 1100/month • SIC (Shanghai, China) ~ 130/month • ~ 80% of Barrel crystals already delivered (48950/61200) • Preseries of Endcap crystals: 100 BTCP, 300 SIC • Last Barrel crystal delivery Feb 2007 • Last Endcap crystal delivery Jan 2008 Elba May 2006 R M Brown - RAL 8

  9. SIC BTCP SIC BTCP Crystal Quality Assurance • Automatic control of: • Dimensions • Optical Transmission • Light yield • Longitudinal uniformity CERN INFN/ENEA Rome Transmission at 420 nm Light Yield Elba May 2006 R M Brown - RAL 9

  10. 8 0 7 0 6 0 T(%) 5 0 4 0 i n i t i a l 3 0 a f t e r i r r a d i a t i o n 2 0 1 0 0 3 0 0 3 5 0 4 0 0 4 5 0 5 0 0 5 5 0 6 0 0 6 5 0 7 0 0 w a v e l e n g t h ( n m ) 0 5 Light Yield Loss (%) Crystal Radiation Resistance Light loss is characterised by an ‘induced absorption’ Under irradiation at room temperature, a dynamic equilibriumforms between formation and annealing of colour centres.  Light loss saturates at a value that depends on dose-rate CMS specification requires: μ420 < 1.5 m-1(Under uniform (lateral) 60Co irradiation at >30 Gy/hr) Under LHC-like conditions for the Barrel (~0.15 Gy/hr) Light yield loss ≾ 6% Verification: BTCP: Use correlation between sharpness of absorption edge and radiation hardness (Check with sample irradiations) SIC: All crystals irradiated by producer Elba May 2006 R M Brown - RAL 10

  11. Endcaps: - Vacuum phototriodes (VPT) • More radiation resistant than Si diodes • (with UV glass window) • - Active area ~ 280 mm2/crystal • Gain 8 -10 (B=4T) Q.E.~20% at 420nm • Delivery ~80%  = 26.5 mm VPT Delivery & Test status MESH ANODE Photodetectors • Barrel - Avalanche photodiodes (APD) • Two 5x5 mm2 APDs/crystal • Gain: 50 QE: ~75% • Temperature dependence: -2.4%/OC • Delivery complete 40mm Elba May 2006 R M Brown - RAL 11

  12. VFE x 5 FE Front End card (FE) MB Trigger Sums LVR Data Trigger Tower (TT) Very Front End card (VFE) HV 2 x12 12 bits Logic 1 x6 12bitADC 2 bits 0 MGPA x1 APD/VPT VFE architecture for single channel On-detector electronics • Trigger primitives computed on the detector • Command&controlviatokenring • Modularity: Trigger Tower (25 channels in Barrel) • - 1 Low Voltage Regulation Board (LVR) • 5 VFE Boards (5 channels each) • 1 FE Board • 1 Fibre sending trig primitives (every bunch Xing) • 1 Fibre sending data (on Level1 accept) Elba May 2006 R M Brown - RAL 12

  13. ASICs in 0.25 mm IBM CMOS Technology • Very high yield (typically >85%) • ADC MGPA FENIX • Status: • All ASICS procured and tested • All systems for 30 SMs are tested & burned-in Full Barrel set available for most components • Endcap components following close behind 30 MeV 45 MeV Noise distribution for 1700 channels of SM13 View of a SuperModule (SM) showingon-detector electronics On-detector electronics: status Elba May 2006 R M Brown - RAL 13

  14. Clock & Control System (CCS) Trigger Concentrator Card (TCC) Data Concentrator Card (DCC) • Status: • CCS finished for whole ECAL • DCC in production for Barrel • TCC for Barrel: Production started • TCC For Endcaps: Schematic finishedFirst board by September LV Power supplies: ~60% of Barrel ordered (rest soon) Order for Endcaps in 2007 Off-Detector electronics Elba May 2006 R M Brown - RAL 14

  15. DT at APD when electronics is powered-up(Worst case: Bottom Supermodule) Cooling &Temperature Stability • Power dissipation of Barrel on-detector electronics ~160 kW • Combined temperature sensitivity of (crystal + APD):  Stabilise temperature to better than ± 0.05 OC • Chilled water at 50l/s Water manifold and pipes on SM Cooling bars in direct contact with electronic cards Elba May 2006 R M Brown - RAL 15

  16. The Problem: Colour centres form in PWO under irradn Transparency loss depends on dose rate Equilibrium is reached after a low dose Partial recovery occurs in a few hours Correlation between transmission losses for scintillation light and laser light 0.95 The Solution: Damage and recovery during LHC cycles tracked with a laser monitoring system 2 wavelengths are used: 440nm and 796nm Light is injected into each crystal Normalisation given by PN diodes (0.1%) Simulation of crystal transparency evolution at LHC (L =2x1033cm-2s-1)- based on test beam irradiation results Laser light monitoring (1) Elba May 2006 R M Brown - RAL 16

  17. An optical switch directs light to one half-supermodule orone quarter Dee at a time 440nm 796nm Light is injected through fibres into the front (Barrel) orrear (Endcap) of each crystal Resolution before irradn / after irradn and correction Laser light monitoring (2) APD Elba May 2006 R M Brown - RAL 17

  18. Sub-module: 10 crystals Module: 400/500 crystals Bare SM SM with cooling Super-module: 1700 crystals Assembly status: 26/36 bare SMs assembled 15/36 SMs completed Production rate 4/month Construction: Barrel 2 Regional Centres: CERN and Rome Elba May 2006 R M Brown - RAL 18

  19. Supercrystal: 25 crystals Dee (½ endcap): 3662 crystals Backplates successfully test mounted on HCAL Construction: Endcaps Production status All mechanical parts delivered Endcap crystal production starts in summer 2006 Elba May 2006 R M Brown - RAL 19

  20. Preshower detector • Rapidity coverage: 1.65< ||< 2.6 (End caps) • Motivation: Improved 0/ discrimination • 2 orthogonal planes of Si strip detectors behind • 2 X0 and 1 X0 Pb respectively • Strip pitch: 1.9mm (63mm long) • Area: 16.5m2 (4300 detectors,1.4x105channels) • High radiation levels - Dose after 10 yrs: • ~2x1014n/cm2 • ~60kGy •  Operate at -10oC Elba May 2006 R M Brown - RAL 20

  21. Status of Preshower Detector Micromodules System motherboards - production finished by end 2006 System Tests Ongoing - 8 ladders shown here Ladders Pre-series underwayProduction by mid 2007 Mechanics Preshower on schedule forinstallation at end of 2007 Off-Detector Readout Electronics First module alreadyprototyped – 12-channeloptical receiver (optoRx) Production completed ~September 07 All ES “complete disc” elements ready for installation at end 2006(before the beam pipe) D.Barney Elba May 2006 R M Brown - RAL 21

  22. Cosmic muons Event: 4161 Cry: 168 Cosmic Muon Test&Calibration • Each SM operated with cosmic rays for ~1 week  Intercalibration: 1-3% (stat) depending on η Mip deposits ~250MeV(increase APD gain from 50 to 200) Status: 10 SM Calibrated Muons through full crystal Elba May 2006 R M Brown - RAL 22

  23. Intercalibration from Laboratory Measurements During assembly, all detector components are characterised Thus the relative calibration ci of each channel may be estimated: Where: LY is crystal light yield, M and eQ are gain and quantum efficiency of the photo-detectorscele is the calibration of the electronics chain Ratio: Test beam/Lab Test beam vs Lab Intercalibration s = 4.2% Elba May 2006 R M Brown - RAL 23

  24. EB+ EB+ Surface Installation EB- Surface Installation (12/18) EB- U’ground Installation (6/18) EB- Reduced time 3→2months Barrel construction schedule Elba May 2006 R M Brown - RAL 24

  25. Insertion at point 5 ECAL Barrel installation Gap HB+/HB- ~ 1mm SM Rails on HB+ 2 SMs inserted 27 April for magnet test Supermodule Installation Elba May 2006 R M Brown - RAL 25

  26. ECAL Endcap installation Endcap Construction Schedule • Assembly plan assumes last EE crystal delivered end Jan 08. • Aim is to have Endcaps installed for 2008 Physics Run • All cables and services are already installed • Goal: D1 Sept07, D2 Nov07, D3 Jan08, D4 Apr08 Elba May 2006 R M Brown - RAL 26

  27. Summary • High resolution electromagnetic calorimetry is a central feature of CMS • The construction of the Barrel ECAL is in the final phase • All mechanical components are delivered for the Endcap ECAL • Crystal delivery sets the schedule for both Barrel and Endcap • The Pre-shower detector is on course for completion as planned • Supermodules are being commissioned and calibrated with cosmic rays • The CMS ECAL will meet its design goals – see next talk! Elba May 2006 R M Brown - RAL 27

  28. Spares Elba May 2006 R M Brown - RAL 28

  29. Pre-calibration In-situ calibration -symmetry w/jet trigger (ET > 120 GeV) Initial pre-calibration by ‘dead reckoning’ based on lab measurements (~4%) • Precision with 11M events • Limit on precision Inter-calibration precision % Lab LY Fast in-situ calibration based on principle that mean energy deposited by jet triggers is independent of  at fixed  (after correction for Tracker material)(~2-3% in few hours) 0 0.5 1.0  Test Beam LY  = 4.0% -ringinter-calibration andZe+e cross-calibration (~1% in 1 day) Z e + e Barrel Test Beam LY – Lab LY Calibration strategy Lab measurements Reference pre-calibration of few SM with 50/120GeV electrons in test beam (<2%) Finally: calibration to < 0.5% with W   + e in ~2 months 70 80 90 100 GeV Elba May 2006 R M Brown - RAL 29

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