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

The ECAL Endcap Calorimeter for CMS D J A Cockerill RAL - UK 2002 LHC Days at Split Split - Croatia October 2002. Outline of Talk. The CMS ECAL Endcaps Performance targets Layout Radiation Environment Crystal Endcap Calorimeter Lead Tungstate Crystals

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

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  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 1

  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 2

  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 3

  4. CMS ECAL Endcap Performance targets • ~40% of H    eventsinvolve the ECAL Endcaps, MH 90-150 GeV Width of Higgs peak limited by experimental resolution • high resolution electromagnetic calorimetry • homogeneous scintillating medium • PbWO4 crystals – fast, dense, moderately rad hard • Higgs mass resolution, H  1 2 , target ~0.5% • m /m = 0.5[E1/E1  E2/E2   / tan(/2)] • whereE/E = a/E  b  c/E for each photon • Target • BarrelEndcap • Stochastic term a= 2.7% 5.7% • Constant term b= 0.55% 0.55% • Noise term, Low Lc= 155MeV 205MeV • High Lc= 210MeV 245MeV 2002 LHC Days at Split, Split, October 2002 D J A Cockerill - RAL 4

  5. 0/Discrimination ( - jet) is potentially the most serious background to H    Track isolation cut reduces (-jet) to  50% of the intrinsic (-) background (pTcut=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 3X0) 2002 LHC Days at Split, Split, October 2002 D J A Cockerill - RAL 5

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

  7. CMS ECAL Endcaps - Layout Forward muon chambers HCAL Endcap ECAL Crystal Endcap 1.48 <  < 3.0 PbWO4 crystals Endcap Preshower 1.65 < < 2.6 Pb/Si detectors 2002 LHC Days at Split, Split, October 2002 D J A Cockerill - RAL 7

  8. CMS ECAL Endcaps - Layout Crystal ECAL Barrel Crystal ECAL Endcaps 14648 crystals Vol 2.7 m3 Mass 22 t 3° off-pointing, pseudo-projective geometry 3m 4T field 3.5m Tracker volume Preshower 2 planes of Si 2 Xo and 1 Xo Pb 4288 sensors 2002 LHC Days at Split, Split, October 2002 D J A Cockerill - RAL 8

  9. Radiation levels, CMS ECAL Endcaps 225 HB Absorbed dose 10 years,  = 3 (inner edge) 200 kGy at shower max 50 kGy behind crystals Dose rate,  = 3.0 15 Gy/h, high luminosity, shower max EB cm HE EE 0 0 400 cm 1.4x106 105 104 103 102 101 Gy Dose and neutron fluence • Neutron fluence • 10 years,  = 2.6 • 1.5.1014 cm-2, preshower • 7.1014 cm-2 behind crystals • 0.8.1014 cm-2 for electronics behind neutron moderator Neutron fluence (1013cm-2) Dose (kGy)  = 1.48 2002 LHC Days at Split, Split, October 2002 D J A Cockerill - RAL 9

  10. Endcap PbWO4 crystals Properties of dense inorganic scintillators 220mm 1” Photodetector 30mm • All identical size/shape • 30 x 30 x 220 mm3 • 24.7 Xo in depth • 2 mm taper, back to front • 25.6 mm photo-detector at rear 200 Endcap R&D xtals produced to date. 2002 LHC Days at Split, Split, October 2002 D J A Cockerill - RAL 10

  11. Endcap PbWO4 crystals PbWO4 crystals produced at BTCP – Russia. 138 ovens. Successful production of larger boules - crucial for the larger ECAL Endcap crystals 30x30 mm2 vs ~26x26 mm2 in Barrel. Larger size to reduce channel count, increased cost effectiveness 2002 LHC Days at Split, Split, October 2002 D J A Cockerill - RAL 11

  12. Endcap PbWO4 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 12

  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 13

  14. =26.7 mm MESH ANODE Vacuum Phototriodes (VPTs) • B-field orientation in end caps favourable for VPTs • (Tube axes 8.5o<||<25.5o with respect to field) • Vacuum devices offer greater radiation hardness than Si diodes • Gain 8-10 at B = 4T • Active area of ~280mm2/crystal • Q.E.~20% at 420nm • 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 40 mm 26.7 mm 2002 LHC Days at Split, Split, October 2002 D J A Cockerill - RAL 14

  15. Light VPT operation Cs-Sb Photocathode Primary photoelectron 10 µm pitch mesh anode (+1000V) Dynode (+800V) 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 15

  16. VPT Characteristics 12 10 8 6 4 2 0 Gain vs Dynode voltage for VA = 1000V and 800V Gain vs Bias Gain • Gains typically 8 -10 • Require HT stability to ~2V VA = 1000V VA = 800V 0 200 400 600 800 1000 VD (Volts) VPT Faceplate transmission 100 90 80 60 40 20 0 Window transmission vs Dose % • Losses <10%, 20kGy • (10 years LHC at  = 2.6 over PbWO4 emission spectrum, 430 nm) 300 400 500 600 700 nm 2002 LHC Days at Split, Split, October 2002 D J A Cockerill - RAL 16

  17. VPT Characteristics All VPTs are measured at 0  B  1.8T and -30o    30o at RAL 1.8T Dipole Magnet at RAL 24 VPT test containers 2002 LHC Days at Split, Split, October 2002 D J A Cockerill - RAL 17

  18. VPT Characteristics VPTs pulsed with a blue LED system at 470 nm 0 - 1.8T field VPT angle to field, - 30o    30o 1.8T Arrows indicate angular regions of end caps 15o Response vs field Response vs Angle 2002 LHC Days at Split, Split, October 2002 D J A Cockerill - RAL 18

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

  20. VPT Characteristics 4T batch sampling tests Relative response of VPTs at 4T at 15o to field in comparison to 0T 0.8 4.0T through bore Superconducting solenoid 120 tubes OK 1 (just) outside cut 2002 LHC Days at Split, Split, October 2002 D J A Cockerill - RAL 20

  21. VPT Production status Contract placed with Research Institute Electron (RIE), Russia 2000 – 500 pre-production devices 2001 – Mass production contract for 15,000 devices Oct 2002 - 2600 devices delivered >1600 tested Delivery rate 4000 per annum On schedule 2002 LHC Days at Split, Split, October 2002 D J A Cockerill - RAL 21

  22. Crystal Endcap Calorimeter Design and construction • Crystals and VPTs held in modular units called supercrystals • 5x5 array of PbWO4 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 22

  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 23

  24. Crystal Endcap Calorimeter Design and construction An Endcap ‘Dee’ 14 cantilevered ‘part supercrystals’ per Dee 138 5x5 cantilevered supercrystals per Dee 3662 crystals per Dee 14648 crystals for the 4 Dees Crystal mass: 5.4 tonnes per Dee 2002 LHC Days at Split, Split, October 2002 D J A Cockerill - RAL 24

  25. CMS Endcap preshower detector 2 orthogonal planes of Si strip detectors behind 2 X0 and 1 X0 Pb respectively Silicon area 16.5m2 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 25

  26. CMS Endcap preshower detector Performance targets Two photons (~1cm spacing) from a 30 GeV PToincident on the SE/EE 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. 2002 LHC Days at Split, Split, October 2002 D J A Cockerill - RAL 26

  27. CMS Endcap preshower detector The preshower silicon micromodule 4288 total, 1.4 x105 channels 600 (14%) have been built and tested 63 mm 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 27

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

  29. CMS Endcap preshower detector A completed compact Endcap preshower detector 2.6m , 0.2m thick C6F14 cooling at –15o for –5o on strips 2002 LHC Days at Split, Split, October 2002 D J A Cockerill - RAL 29

  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 30

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

  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, ET > 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 32

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

  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 2,3,4 2006 Preshower 2006 ECAL Endcaps installed in CMS Jan 2007 Mass production of ECAL Endcap components has started Mechanical design complete. A challenging schedule ahead. 2002 LHC Days at Split, Split, October 2002 D J A Cockerill - RAL 34

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