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CMS

CMS. Endcap Electromagnetic Calorimeter and Global Calorimeter Trigger, Physics & Computing. Presented by Peter Hobson, Brunel University on behalf of Bristol University Brunel University Imperial College of Science, Technology & Medicine RAL.

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  1. CMS Endcap Electromagnetic Calorimeter and Global Calorimeter Trigger, Physics & Computing Presented by Peter Hobson, Brunel University on behalf of Bristol University Brunel University Imperial College of Science, Technology & Medicine RAL PPRP September 2002 UK CMS 1

  2. The Compact Muon Solenoid Detector for LHC Physics goals: SUSY, Higgs, Heavy flavours, heavy ions Endcap Electromagnetic Calorimeters PPRP September 2002 UK CMS 2

  3. ECAL design objectives High resolution electromagnetic calorimetry is a basic design objective of CMS Benchmark physics process: Sensitivity to a low mass Higgs via H    PPRP September 2002 UK CMS 3

  4. ECAL Parameters 6.3 m 3.5 m 3° off-pointing pseudo-projective geometry PPRP September 2002 UK CMS 4

  5. UK Commitments • Develop and prototype photodetectors • Procure and test photodetectors • Design and prototype Supercrystals • Design and procure Supercrystal mechanics and HV • Design and procure Supercrystal support structures • Evaluate lead tungstate crystals for endcap • Set up a Regional Centre for Supercrystal production • Construct and test Supercrystals and ship to CERN • Design, prototype and construct the Global Calorimeter Trigger PPRP September 2002 UK CMS 5

  6. =26.5 mm MESH ANODE Photodetectors: end caps • Vacuum Phototriodes (VPT) • Developed by CMS-UK in conjunction with industry (Western & Russian) • Vacuum devices offer greater radiation hardness than Si diodes • Gain 8 - 10 at B = 4 T • Active area of ~ 280 mm2/crystal • Q.E. ~ 20% at 420 nm • UV glass window - less expensive than ‘quartz’ • - more radiationresistant than borosilicate glass Order placed with RIE (Russia): 2600 devices delivered so far and >1600 tested PPRP September 2002 UK CMS 6

  7. All VPTs are measured at 0  B  1.8T and -30o 30o at RAL A sample of VPTs are measured at B =4.0T and  = 15o at Brunel VPT Characterisation 1.8T Dipole Magnet at RAL 4.0T Superconducting solenoid at Brunel PPRP September 2002 UK CMS 7

  8. VPT Characteristics 4T test Response vs. Angle Only 8% loss of transparency after 20 kGy (10 years) Critical magnetic field and radiation tolerance tests are done in the UK PPRP September 2002 UK CMS 8

  9. VPT Characteristics On schedule Anode response of production VPTs at 1.8T (averaged over 8O – 25O), in units of e-/MeV (using data from beam tests with PbWO4), plotted versus the product of photocathode efficiency and gain, as measured by the manufacturer at 0T PPRP September 2002 UK CMS 9

  10. Construction: end caps The endcap is mechanically complex Tight tolerance on dimensions, deflections and thermal management. PPRP September 2002 UK CMS 10

  11. Construction: end caps • ‘Supercrystal’: carbon-fibre alveola containing 5x5 tapered crystals + VPTs + HV filter • 156 Supercrystals per Dee • All crystals have identical dimensions • All Supercrystals are identical • (apart from inner and outer circumference) PPRP September 2002 UK CMS 11

  12. Construction: end caps Figure 6. The arrangement of components within a Supercrystal The principal components of a supercrystal: PbWO4 crystal, VPT, alveolar, optical fibre monitor, HT filter, mechanics PPRP September 2002 UK CMS 12

  13. Construction: end caps • Engineering Design Reviews • - Supercrystal mechanics approved • (332 Carbon-fibre/epoxy alveolar modules (60% of total) have now been produced in Russia to UK design) • 2002 – D and backplate mechanics approved • Three full-sized supercrystal prototypes completed. • These are major milestones achieved. The overall mechanical design is now frozen and the tendering process has begun. PPRP September 2002 UK CMS 13

  14. Evaluation of endcap crystals Crystal lab at ICSTM has studied in detail the formation and annealing of colour centres Ongoing developments have progressively increased the boule diameter: Two barrel crystals are now cut from a single boule in current production Even larger boules have been grown which could provide four crystals per boule • Transmission loss due to irradiation at 15 Gy/h for 24 hours. • Induced absorption fitted with Gaussians at 2.3 eV (540nm) and 3.1 eV (400nm). PPRP September 2002 UK CMS 14

  15. Evaluation of endcap crystals • ICSTM crystal laboratory • Measurements demonstrate that the low level of light collection non-uniformity means that no special surface/wrapping treatment is needed. • This is a crucial result since wrapping increases complexity and cost Correlation between light collection non-uniformity (RNUF) and optical parameters measured at the ICSTM Crystal Laboratory. PPRP September 2002 UK CMS 15

  16. ECAL Readout architecture • Original TDR ECAL design cannot be afforded • A new scheme (post GPD Mid-term Review) endorsed by CMS in March 2002 • Trigger primitive generation now moved to the front-end electronics • Fully digitised data can be restricted to events passing Level 1 trigger • Order of magnitude reduction in number of links and off-detector electronics • Major use of Tracker components (optical links, clock and control) and APV25 expertise in 0.25µm technology PPRP September 2002 UK CMS 16

  17. ECAL Readout architecture • CMS Requested the new VFE ASIC (FENIX) be designed by the Microelectronics group at RAL. • CMS and PPARC have agreed that the staff costs will be covered from the UK contribution to the 'Cost-to-Completion'. PPRP September 2002 UK CMS 17

  18. Global Calorimeter Trigger Global Calorimeter Trigger (GCT) sorts trigger “objects” and forms energy sums PPRP September 2002 UK CMS 18

  19. Global Calorimeter Trigger • FPGA processing using common module design • Data exchange via Gbit serial links • UK group developed the use of FPGA technology to implement the algorithms • Algorithm development has improved physics coverage and jet trigger performance • Milestone: Level-1 Trigger TDR Dec 2000 • System design complete, hardware prototyping starting now PPRP September 2002 UK CMS 19

  20. Physics simulation • UK is significantly involved in the Physics Reconstruction and Selection project to maximise our ability to exploit our detectors. • ECAL – e/gamma Group • Led by a UK Physicist • Responsible for all aspects of the ECAL software • Tracker – b/tau Group • UK physicist leading the ‘data-handling’ group • responsible for all aspects of offline software related to tracker readout/electronics • Provides test-beam analysis tools and contributes to the data analysis PPRP September 2002 UK CMS 20

  21. Physics simulation Data rate in the silicon tracker (barrel) High and low luminosity pp Heavy-ion The data rate is everywhere small compared with the 200 MB/s limit that the DAQ can cope with. PPRP September 2002 UK CMS 21

  22. CMS computing in the UK • Tier 1 centre at RAL for CMS • Fraction of a joint central LHC facility • Tier 2 centres in London and S.England • The focus for CMS-UK analysis in the future • Major contribution to the 2000-2 production challenge • 5 TB data produced in the UK, 6 UK physicists involved • Use of GRID computing technology • CMS first in HEP to deploy Grid-based production tools • Increasing profile within the CMS Core Computing and Software project PPRP September 2002 UK CMS 22

  23. ECAL, GCT & Computing Summary • Vacuum Phototriodes • Contract placed, delivery on schedule • Endcap mechanics • Two major design reviews successfully passed • Tender in process for supercrystal mechanics • Crystals • Prototype Endcap crystals evaluated • Pre-production order about to be placed • Global Calorimeter Trigger • December 2000 Level 1 trigger Technical Design Report • Prototypes of components will be produced early 2003 • Computing • Major contribution to the CMS production exercises • Leading roles in developing ECAL and Tracker related software PPRP September 2002 UK CMS 23

  24. ECAL Concerns • Crystal delivery • There have been delays in placing the order for endcap crystals. The delivery of crystals is on the critical path. • Electronics • Redesign of ECAL electronics has provided large cost savings. However the new and complex system must be successfully prototyped before the production phase. PPRP September 2002 UK CMS 24

  25. Overall Summary • Although CMS has encountered problems, this is to be expected in a project of such size and complexity. The problems are being tackled and CMS has Financial Plan and Master Schedule that aims to deliver a full detector in time for physics. • UK designing new ASIC for ECAL electronics • The cuts made for SCP4 have increased the risks associated with the project substantially. The Travel Budget in future years is of particular concern, as the focus of activities moves to CERN. Despite these concerns, the UK projects are making excellent progress. PPRP September 2002 UK CMS 25

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