2002 LHC Days at Split, Split, October 2002 D J A Cockerill - RAL 1 The ECAL Endcap Calorimeter for CMS D J A Cockerill RAL - UK 2002 LHC Days at Split Split - Croatia October 2002

2002 LHC Days at Split, Split, October 2002 D J A Cockerill - RAL 2 Outline of Talk The CMS ECAL Endcaps Performance targets Layout Radiation Environment Crystal Endcap Calorimeter Lead Tungstate Crystals Vacuum Phototriode Photodetectors Design and construction Endcap Preshower detector Silicon detectors Design & construction Prototype performance Status summary

2002 LHC Days at Split, Split, October 2002 D J A Cockerill - RAL 3 CMS ECAL Endcap Performance targets High resolution electromagnetic calorimetry basic design objective of CMS Benchmark physics process sensitivity to a low mass Higgs via H

2002 LHC Days at Split, Split, October 2002 D J A Cockerill - RAL 4 CMS ECAL Endcap Performance targets Higgs mass resolution, H 1 2, target ~0.5% m / m = 0.5 [ E 1 / E 1 E 2 / E 2 / tan( / 2 ) ] where E / E = a / E b c/ E for each photon Target Barrel Endcap Stochastic term a = 2.7% 5.7% Constant term b = 0.55% 0.55% Noise term, Low L c = 155 MeV 205 MeV High L c = 210 MeV 245 MeV ~40% of H events involve the ECAL Endcaps, M H GeV Width of Higgs peak limited by experimental resolution high resolution electromagnetic calorimetry homogeneous scintillating medium PbWO 4 crystals – fast, dense, moderately rad hard

2002 LHC Days at Split, Split, October 2002 D J A Cockerill - RAL 5 0 / Discrimination ( - jet) is potentially the most serious background to H Track isolation cut reduces ( - jet) to 50% of the intrinsic ( - ) background ( p T cut = 2GeV/c ) Use 0 / discrimination in the ECAL to gain an extra margin of safety Barrel: Lateral shower shape in crystals (limited by crystal size at high E 0 ) End cap: Cluster separation in preshower (limited by shower fluctuations at 3X 0 )

2002 LHC Days at Split, Split, October 2002 D J A Cockerill - RAL 6 CMS ECAL Endcaps - Layout Endcap Electromagnetic Calorimeters Scale Muon chambers

2002 LHC Days at Split, Split, October 2002 D J A Cockerill - RAL 7 Endcap Preshower 1.65 < < 2.6 Pb/Si detectors ECAL Crystal Endcap 1.48 < < 3.0 PbWO 4 crystals HCAL Endcap CMS ECAL Endcaps - Layout Forward muon chambers

2002 LHC Days at Split, Split, October 2002 D J A Cockerill - RAL 8 CMS ECAL Endcaps - Layout Crystal ECAL Barrel Preshower 2 planes of Si 2 X o and 1 X o Pb 4288 sensors Crystal ECAL Endcaps crystals Vol 2.7 m 3 Mass 22 t 3° off-pointing, pseudo-projective geometry 3.5m Tracker volume 3m 4T field

2002 LHC Days at Split, Split, October 2002 D J A Cockerill - RAL 9 Radiation levels, CMS ECAL Endcaps cm cm 1.4x Gy Dose (kGy)Neutron fluence (10 13 cm -2 ) = 1.48 Absorbed dose 10 years, = 3 (inner edge) 200 kGy at shower max 50 kGy behind crystals Dose rate, = Gy/h, high luminosity, shower max Dose and neutron fluence HB EB EE HE Neutron fluence 10 years, = cm -2, preshower cm -2 behind crystals cm -2 for electronics behind neutron moderator

2002 LHC Days at Split, Split, October 2002 D J A Cockerill - RAL 10 Endcap PbWO 4 crystals Properties of dense inorganic scintillators All identical size/shape 30 x 30 x 220 mm X o in depth 2 mm taper, back to front 25.6 mm photo-detector at rear 1 Photodetector 200 Endcap R&D xtals produced to date. 30mm 220mm

2002 LHC Days at Split, Split, October 2002 D J A Cockerill - RAL 11 Endcap PbWO 4 crystals PbWO 4 crystals produced at BTCP – Russia. 138 ovens. Successful production of larger boules - crucial for the larger ECAL Endcap crystals 30x30 mm 2 vs ~26x26 mm 2 in Barrel. Larger size to reduce channel count, increased cost effectiveness

2002 LHC Days at Split, Split, October 2002 D J A Cockerill - RAL 12 Endcap PbWO 4 crystals At present, plant dedicated to Barrel crystal production – on CMS critical path 2 Barrel crystals per boule of 65 mm diameter Barrel crystal yield 86%, productivity increase 160% Start Endcap crystal mass production, 2 crystals per boule of 75 mm diameter, in 2003 (1000 crystals) On critical path to meet ECAL Endcap installation deadline of Jan 2007

2002 LHC Days at Split, Split, October 2002 D J A Cockerill - RAL 13 Vacuum Phototriodes (VPTs) ECAL Endcap within 4T magnetic volume of CMS Require magnetic field tolerant and radiation tolerant photodetectors with gain Vacuum phototriode (VPT) photodetectors chosen for the ECAL Endcaps

2002 LHC Days at Split, Split, October 2002 D J A Cockerill - RAL 14 Vacuum Phototriodes (VPTs) B-field orientation in end caps favourable for VPTs (Tube axes 8.5 o < | | < 25.5 o with respect to field) Vacuum devices offer greater radiation hardness than Si diodes Gain at B = 4 T Active area of ~ 280 mm 2 /crystal Q.E. ~ 20% at 420 nm Excess noise factor is F ~ 3 Insensitive to shower leakage particles UV glass window - less expensive than quartz - more radiation resistant than borosilicate glass Irradiation causes darkening of window Loss in response < 10% after 10 yrs – acceptable Split – photocathode efficiency scans across faceplate = 26.7 mm MESH ANODE 26.7 mm 40 mm

2002 LHC Days at Split, Split, October 2002 D J A Cockerill - RAL 15 VPT operation Light Cs-Sb Photocathode 10 µm pitch mesh anode (+1000V) Dynode (+800V) Primary photoelectron Dynode gain is ~ 20 but collection efficiency is about 50% Typical tube gain is ~10

2002 LHC Days at Split, Split, October 2002 D J A Cockerill - RAL 16 VPT Characteristics V D (Volts) Gain V A = 1000V V A = 800V Gain vs Bias Window transmission vs Dose % nm Gain vs Dynode voltage for V A = 1000V and 800V VPT Faceplate transmission Losses <10%, 20kGy (10 years LHC at = 2.6 over PbWO 4 emission spectrum, 430 nm) Gains typically Require HT stability to ~2V

2002 LHC Days at Split, Split, October 2002 D J A Cockerill - RAL 17 VPT Characteristics All VPTs are measured at 0 B 1.8T and -30 o 30 o at RAL 1.8T Dipole Magnet at RAL24 VPT test containers

2002 LHC Days at Split, Split, October 2002 D J A Cockerill - RAL 18 VPT Characteristics T field VPT angle to field, - 30 o 30 o VPTs pulsed with a blue LED system at 470 nm 15 o 1.8T Arrows indicate angular regions of end caps Response vs AngleResponse vs field

2002 LHC Days at Split, Split, October 2002 D J A Cockerill - RAL 19 VPT Characteristics Yield, 1.8T vs P*G, 0TYield (e/MeV), 1.8T 4 70 VPT electron yield in e/MeV - normalised using test beam data P*G P, photocathode eff. G, Gain VPT yields meet Endcap performance requirements 70 Yield (e/MeV)

2002 LHC Days at Split, Split, October 2002 D J A Cockerill - RAL 20 VPT Characteristics 4T batch sampling testsRelative response of VPTs at 4T at 15 o to field in comparison to 0T 120 tubes OK 1 (just) outside cut T through bore Superconducting solenoid

2002 LHC Days at Split, Split, October 2002 D J A Cockerill - RAL 21 VPT Production status On schedule Contract placed with Research Institute Electron (RIE), Russia 2000 – 500 pre-production devices 2001 – Mass production contract for 15,000 devices Oct devices delivered >1600 tested Delivery rate 4000 per annum

2002 LHC Days at Split, Split, October 2002 D J A Cockerill - RAL 22 Crystal Endcap Calorimeter Design and construction Crystals and VPTs held in modular units called supercrystals 5x5 array of PbWO 4 crystals/VPTs Thin walled (400 m) carbon fibre alveolar unit – 330 (60%) made HT filter cards Optical fibres for monitoring crystal transparency

2002 LHC Days at Split, Split, October 2002 D J A Cockerill - RAL 23 Crystal Endcap Calorimeter Design and construction Prototype construction for Crystal Endcap beam tests in 2003 Front end electronics readout volume

2002 LHC Days at Split, Split, October 2002 D J A Cockerill - RAL cantilevered part supercrystals per Dee 3662 crystals per Dee crystals for the 4 Dees Crystal mass: 5.4 tonnes per Dee 138 5x5 cantilevered supercrystals per Dee Crystal Endcap Calorimeter Design and construction An Endcap Dee

2002 LHC Days at Split, Split, October 2002 D J A Cockerill - RAL 25 CMS Endcap preshower detector 2 orthogonal planes of Si strip detectors behind 2 X 0 and 1 X 0 Pb respectively Silicon area 16.5 m 2 Incident beam direction Crucial to keep Si as close as possible to Pb for optimal performance

2002 LHC Days at Split, Split, October 2002 D J A Cockerill - RAL 26 CMS Endcap preshower detector Performance targets o : photon separation usually a few mm in Endcaps For o / discrimination: require x-y spatial reconstruction of shower to ~300 m. Achieved with Si strip detectors. Two photons (~1cm spacing) from a 30 GeV P T o incident on the SE/EE

2002 LHC Days at Split, Split, October 2002 D J A Cockerill - RAL 27 CMS Endcap preshower detector The preshower silicon micromodule 4288 total, 1.4 x10 5 channels 600 (14%) have been built and tested 63 mm 32 Strips 1.8 mm width pitch 1.9 mm 320 m p + on n 4k.cm, 300V

2002 LHC Days at Split, Split, October 2002 D J A Cockerill - RAL 28 CMS Endcap preshower detector Arrangement of the micromodules Ladder for 8 micromodules

2002 LHC Days at Split, Split, October 2002 D J A Cockerill - RAL 29 CMS Endcap preshower detector C 6 F 14 cooling at –15 o for –5 o on strips A completed compact Endcap preshower detector 2.6m, 0.2m thick

2002 LHC Days at Split, Split, October 2002 D J A Cockerill - RAL 30 Crystal Endcap Calorimeter Design and construction Thermal shield Preshower Completed Endcap

2002 LHC Days at Split, Split, October 2002 D J A Cockerill - RAL 31 Prototype Performance Energy Resolution without preshower No preshower detector

2002 LHC Days at Split, Split, October 2002 D J A Cockerill - RAL 32 Prototype Performance Energy resolution with preshower Energy resolution degraded by Pb absorber - substantially restored using Si p.h. information Excellent agreement between MC and data Required performance achieved for E > 60 GeV, E T > 20 GeV OK for H (Pb 10% thicker than final CMS, in this test)

2002 LHC Days at Split, Split, October 2002 D J A Cockerill - RAL 33 Prototype Performance Preshower spatial resolution Target spatial resolution of 300 m achieved above 60 GeV Spatial resolution for electrons Excellent agreement with Monte Carlo

2002 LHC Days at Split, Split, October 2002 D J A Cockerill - RAL 34 CMS ECAL Endcaps Status summary Crystals Mass production to start in 2003 VPTs Mass production 2600 of 14,648 (18%) Preshower Sensors mass production 600 of 4288 (14%) Mechanics Supercrystal alveolar units 330 of 560 (60%) Monitoring system Components ordered and delivery on schedule Dee Electronics Analogue front end, fibre optic digital readout substantial redesign and cost optimisation in 2002 first prototypes expected in 2003 Milestones Dee1 complete 2005 Dee 2,3, Preshower 2006 ECAL Endcaps installed in CMS Jan 2007 Mass production of ECAL Endcap components has started Mechanical design complete. A challenging schedule ahead.