pprp september 2002 uk cms 1 cms endcap electromagnetic calorimeter and global calorimeter trigger,...

PPRP September 2002 UK CMS 1

CMS

Endcap Electromagnetic Calorimeter and Global Calorimeter Trigger, Physics & Computing

Presented by Peter Hobson, Brunel University on behalf of

Bristol UniversityBrunel UniversityImperial College of Science, Technology & MedicineRAL


The Compact Muon Solenoid Detector for LHC

Physics goals: SUSY, Higgs, Heavy flavours, heavy ions

EndcapElectromagneticCalorimeters


ECAL design objectivesHigh resolution electromagnetic calorimetry is a basic design objective of CMS

Benchmark physics process: Sensitivity to a low mass Higgs via H


ECAL Parameters Parameter Barrel End caps

Coverage Δφ x Δη Xtal size (mm3) Depth in X0

| η | <1.48

0.0175 × 0.0175

21.8 × 21.8 × 230 25.8

1.48 < | η | < 3.0

0.0175 × 0.0175 to 0.05 × 0.05

30.0 × 30.0 × 220 24.7

# of crystals Volume (m3) Xtal mass (t)

61200 8.14 67.4

14648 2.7

22.0

3° off-pointing pseudo-projective geometry

3.5 m

6.3 m


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


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 radiation resistant than borosilicate glass

= 26.5 mm

MESH ANODE

Order placed with RIE (Russia):2600 devices delivered so far and >1600 tested


VPT Characterisation

4.0T Superconducting solenoid at Brunel

1.8T Dipole Magnet at RAL

A sample of VPTs are measured at B =4.0T and = 15o at Brunel

All VPTs are measured at

0 B 1.8T and -30o 30o at RAL


0.0

0.2

0.4

0.6

0.8

1.0

1.2

-90 -60 -30 0 30 60 90VPT angle (deg.)

Re

l. A

no

de

Re

sp

on

se

VPT Characteristics

Response vs. Angle

YT-49 Batch 30797a19.3 kGy dose

-0.02

0

0.02

0.04

0.06

0.08

0.1

300 400 500 600 700 800

Wavelength (nm)

Ind

uc

ed

ab

so

rba

nc

e

Production tubes

0

5

10

15

20

25

30

35

40

45

0.8 0.85 0.9 0.95 1 1.05 1.1 >1.1

Relative 4T/0T pulsed gain (upper bin edge)

Nu

mb

er

in b

in

Passed

Critical magnetic field and radiation tolerance tests are done in the UK

Only 8% loss of transparency after 20 kGy (10 years)

4T test


VPT Characteristics

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

On schedule


Construction: end caps

The endcap is mechanically complexTight tolerance on dimensions, deflections and thermal management.



‘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)



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



Engineering Design Reviews2000 - 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.


Evaluation of endcap crystals

Ongoing developments have progressively increased the boule diameter:Two barrel crystals are now cut from a single boule in current productionEven 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).

Crystal lab at ICSTM has studied in detail the formation and annealing of colour centres


Evaluation of endcap crystals

-0.025

-0.020

-0.015

-0.010

-0.005

0.000

0.005

0.010

0.015

0.020

0.025

-0.8 -0.6 -0.4 -0.2 0 0.2 0.4 0.6 0.8

RNUF

R-S

lop

e(3

50

nm

) -

R-S

lop

e(3

65

nm

)

ICSTM crystal laboratoryMeasurements 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.


• 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

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'.

ECAL Readout architecture


Global Calorimeter Trigger

Global Calorimeter Trigger (GCT) sorts trigger “objects” and forms energy sums


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


Physics simulationUK 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


Physics simulation

0

20

40

60

80

100

120

1 2 3 4 5 6 7 8 9 10

Barrel layer

Dat

a-ra

te /

FE

D (

MB

/s)

High lumi p-p (100 kHz)Low lumi p-p (100 kHz)Pb-Pb (8 kHz)

The data rate is everywhere small compared with the200 MB/s limit that the DAQ can cope with.

Heavy-ion

High and low luminosity pp

Data rate in the silicon tracker (barrel)


• 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

CMS computing in the UK


• 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

ECAL, GCT & Computing Summary


• 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.

ECAL Concerns


• 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.

Overall Summary

Despite these concerns, the UK projects are making excellent progress.

pprp september 2002 uk cms 1 cms endcap electromagnetic calorimeter and global calorimeter trigger,...

Documents

uk cms

uk commitments

t test slide

mechanics slide

h slide

schedule slide

tested slide

outer circumference