CMS ECAL The Status of the CMS Electromagnetic

CMS ECAL 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

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

Compact Muon Solenoid CMS ECAL HCAL Total weight: 12, 500 t Overall diameter: 15 m Overall length: 21. 6 m Magnetic field: 4 T Muon chambers Tracker ECAL 4 T solenoid Iron yoke Elba May 2006 R M Brown - RAL 3

ECAL design objectives CMS ECAL High resolution electromagnetic calorimetry is central to the CMS design Benchmark process: H m / m = 0. 5 [ E 1/ E 1 E 2/ E 2 / tan( / 2 )] Where: E / E = a / E b c/ E Aim (TDR): Barrel Stochastic term: a= 2. 7% Coloured histograms are separate contributing backgrounds for 1 fb-1 End cap 5. 7% (p. e. stat, shower fluct, photo-detector, lateral leakage) Constant term: b = 0. 55% (non-uniformities, inter-calibration, longitudinal leakage) Noise: (electronic, pile-up) Low L c = 155 Me. V 770 Me. V High L 210 Me. V 915 Me. V Optimised analysis (d relies on interaction vertex measurement) Elba May 2006 R M Brown - RAL 4

Challenges & Choices CMS ECAL Challenges: • Fast response (25 ns between bunch crossings) • High radiation doses and neutron fluences (10 year doses: 1013 n/cm 2, 1 k. Gy at =0 • • 2 x 1014 n/cm 2, 50 k. Gy 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

Lead tungstate properties CMS ECAL Fast light emission: ~80% in 25 ns Peak emission ~425 nm (visible region) Short radiation length: X 0 = 0. 89 cm Small Molière radius: RM = 2. 10 cm Radiation resistant to very high doses But: Temperature dependence ~2. 2%/OC ® Stabilise to 0. 1 OC Formation and decay of colour centres in dynamic equilibrium under irradiation ® Precise light monitoring system Low light yield (1. 3% Na. I) ® Photodetectors with gain in mag field Elba May 2006 R M Brown - RAL 6

ECAL Layout CMS ECAL Pb/Si Preshowers: 4 Dees (2/endcap) 4300 Si strips (~ 63 x 1. 9 mm 2) Tapered crystals Pointing ~ 3 o from vertex Barrel: 36 Supermodules (18 per half-barrel) 61200 Crystals (34 types) – total mass 67. 4 t Dimensions: ~ 25 x 230 mm 3 (25. 8 X 0) D x D = 0. 0175 x 0. 0175 Elba May 2006 Endcaps: 4 Dees (2 per endcap) 14648 Crystals (1 type) – total mass 22. 9 t Dimensions: ~ 30 x 220 mm 3 (24. 7 X 0) D x D = 0. 0175 x 0. 0175 ↔ 0. 05 x 0. 05 R M Brown - RAL 7

Crystal production CMS ECAL Crystal delivery determines ECAL Critical Path Suppliers: BTCP (Bogoroditsk, Russia) ~ 1100/month SIC (Shanghai, China) ~ 130/month ~ 80% of Barrel crystals already delivered (48 950/61 200) Preseries of Endcap crystals: 100 BTCP, 300 SIC Ø Last Barrel crystal delivery Feb 2007 Ø Last Endcap crystal delivery Jan 2008 Elba May 2006 R M Brown - RAL 8

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

Crystal Radiation Resistance CMS ECAL Light loss is characterised by an ‘induced absorption’ Light loss saturates at a value that depends on dose-rate CMS specification requires: μ 420 < 1. 5 m-1 (Under uniform (lateral) 60 Co irradiation at >30 Gy/hr) Under LHC-like conditions for the Barrel (~0. 15 Gy/hr) Light yield loss ≾ 6% 80 70 60 50 40 initial 30 after irradiation 20 10 0 300 350 400 450 500 550 600 650 700 T(%) Under irradiation at room temperature, a dynamic equilibrium forms between formation and annealing of colour centres. wavelength(nm) Verification: BTCP: Use correlation between sharpness of absorption edge and radiation hardness (Check with sample irradiations) SIC: All crystals irradiated by producer 0 5 Light Yield Loss (%) Elba May 2006 R M Brown - RAL 10

Photodetectors Barrel - Avalanche photodiodes (APD) Two 5 x 5 mm 2 APDs/crystal - Gain: 50 QE: ~75% - Temperature dependence: -2. 4%/OC - Delivery complete 40 mm CMS ECAL Endcaps: - Vacuum phototriodes (VPT) More radiation resistant than Si diodes (with UV glass window) - Active area ~ 280 mm 2/crystal - Gain 8 -10 (B=4 T) Q. E. ~20% at 420 nm - Delivery ~80% = 26. 5 mm VPT Delivery & Test status Elba May 2006 R M Brown - RAL MESH ANODE 11

On-detector electronics CMS ECAL VFE x 5 FE Front End card (FE) Trigger Sums Trigger Tower (TT) Data x 12 x 6 APD/VPT x 1 2 1 12 bit ADC 0 12 bits Logic 2 bits VFE architecture for single channel Elba May 2006 LVR Very Front End card (VFE) HV MGPA MB Trigger primitives computed on the detector Command & control via token ring 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 Level 1 accept) R M Brown - RAL 12

On-detector electronics: status CMS ECAL ASICs in 0. 25 mm IBM CMOS Technology Very high yield (typically >85%) 30 Me. V 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 45 Me. V Noise distribution for 1700 channels of SM 13 View of a Super. Module (SM) showing on-detector electronics Elba May 2006 R M Brown - RAL 13

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

Cooling &Temperature Stability CMS ECAL Ø Power dissipation of Barrel on-detector electronics ~160 k. W Ø Combined temperature sensitivity of (crystal + APD): Stabilise temperature to better than ± 0. 05 OC Ø Chilled water at 50 l/s DT at APD when electronics is powered-up (Worst case: Bottom Supermodule) Elba May 2006 Water manifold and pipes on SM Cooling bars in direct contact with electronic cards R M Brown - RAL 15

Laser light monitoring (1) CMS ECAL 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 The Solution: Damage and recovery during LHC cycles tracked with a laser monitoring system 2 wavelengths are used: 440 nm and 796 nm Light is injected into each crystal Normalisation given by PN diodes (0. 1%) Elba May 2006 R M Brown - RAL Simulation of crystal transparency evolution at LHC (L =2 x 1033 cm-2 s-1) - based on test beam irradiation results 0. 95 Correlation between transmission losses for scintillation light and laser light 16

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

Construction: Barrel CMS ECAL 2 Regional Centres: CERN and Rome 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 Elba May 2006 R M Brown - RAL 18

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

Preshower detector CMS ECAL Rapidity coverage: 1. 65 < | | < 2. 6 (End caps) Motivation: Improved 0/ discrimination • 2 orthogonal planes of Si strip detectors behind 2 X 0 and 1 X 0 Pb respectively • Strip pitch: 1. 9 mm (63 mm long) • Area: 16. 5 m 2 (4300 detectors, 1. 4 x 105 channels) High radiation levels - Dose after 10 yrs: • ~ 2 x 1014 n/cm 2 • ~ 60 k. Gy Operate at -10 o C Elba May 2006 R M Brown - RAL 20

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

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

Intercalibration from Laboratory Measurements CMS ECAL 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 e. Q are gain and quantum efficiency of the photo-detectors cele is the calibration of the electronics chain Ratio: Test beam/Lab Test beam vs Lab Intercalibration Elba May 2006 R M Brown - RAL = 4. 2% 23

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

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

Endcap Construction Schedule CMS ECAL ØAssembly plan assumes last EE crystal delivered end Jan 08. ØAim is to have Endcaps installed for 2008 Physics Run ØAll cables and services are already installed ØGoal: D 1 Sept 07, D 2 Nov 07, D 3 Jan 08, D 4 Apr 08 ECAL Endcap installation Elba May 2006 R M Brown - RAL 26

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

Spares Elba May 2006 R M Brown - RAL CMS ECAL 28

Calibration strategy Pre-calibration Lab LY Initial pre-calibration by ‘dead reckoning’ based on lab measurements (~4%) Reference pre-calibration of few SM with 50/120 Ge. V electrons in test beam (<2%) Test Beam LY = 4. 0% 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) In-situ calibration -symmetry w/jet trigger (ET > 120 Ge. V) Inter-calibration precision % Lab measurements CMS ECAL • Precision with 11 M events • Limit on precision 0 -ring inter-calibration and Z e + e cross-calibration (~1% in 1 day) 0. 5 1. 0 Z e+e Barrel Finally: calibration to < 0. 5% with W + e in ~2 months Test Beam LY – Lab LY Elba May 2006 70 R M Brown - RAL 80 90 100 Ge. V 29