CMS ECAL Elba May 2006 R M Brown - RAL 1 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

CMS ECAL

The Status of the CMS Electromagnetic Calorimeter

R M Brown

On behalf of the CMS ECAL Group


CMS ECAL

Overview

Introduction Design objectives and technology choices Description and status: Crystals Photo-detectors On-detector electronics Off-detector electronics Laser monitoring system Mechanical construction and assembly

Pre-shower Intercalibration with cosmic muons Construction and installation schedule Summary


CMS ECAL

Compact Muon Solenoid

ECAL

Tracker

4T solenoid

Muon chamber

s

HCAL

Iron yoke

Total weight: 12,500 tOverall diameter: 15 mOverall length: 21.6 mMagnetic field: 4 T


CMS ECAL

Coloured histograms are separate contributing backgrounds for 1fb-1

ECAL design objectives

(electronic, pile-up)

High resolution electromagneticcalorimetry is central to the CMS design

Benchmark process: H

m / m = 0.5 [E1/ E1 E2

/ E2 / tan( / 2 )]

Where: E / E = a / E b c/ E

Aim (TDR): Barrel End cap

Stochastic term: a = 2.7% 5.7% (p.e. stat, shower fluct, photo-detector, lateral leakage)

Constant term: b = 0.55% 0.55% (non-uniformities, inter-calibration, longitudinal leakage)

Noise: Low L c = 155 MeV 770 MeV

High L 210 MeV 915 MeV

( relies on interaction vertex measurement)

Integrated luminosity for 5 discovery (fb-1)

No syst errors

with syst errors

Integrated luminosity for 5 discovery (fb-1)Integrated luminosity for 5 discovery (fb-1)

No syst errors

with syst errors

Optimised analysis


CMS ECAL

Challenges & Choices

Challenges:• Fast response (25ns between bunch crossings)

• High radiation doses and neutron fluences(10 year doses: 1013 n/cm2, 1kGy at =0 2x1014 n/cm2, 50kGy 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 m CMOS• Pb/Si Preshower detector in Endcap region• Laser light monitoring system


CMS ECAL

Lead tungstate properties

Temperature dependence ~2.2%/OC Stabilise to 0.1OC

Formation and decay of colour centresin dynamic equilibrium under irradiation Precise light monitoring system

Low light yield (1.3% NaI) Photodetectors with gain in mag field

But:

Fast light emission: ~80% in 25 ns

Peak emission ~425 nm (visible region)

Short radiation length: X0 = 0.89 cm

Small Molière radius: RM = 2.10 cm

Radiation resistant to very high doses


CMS ECAL

ECAL Layout

Barrel: 36 Supermodules (18 per half-barrel)

61200 Crystals (34 types) – total mass 67.4 t

Dimensions: ~ 25 x 25 x 230 mm3 (25.8 X0)

x = 0.0175 x 0.0175

Tapered crystalsPointing ~ 3o from vertex

Pb/Si Preshowers: 4 Dees (2/endcap)

4300 Si strips(~ 63 x 1.9 mm2)

Endcaps: 4 Dees (2 per endcap)

14648 Crystals (1 type) – total mass 22.9 t

Dimensions: ~ 30 x 30 x 220 mm3 (24.7 X0)

x = 0.0175 x 0.0175 ↔ 0.05 x 0.05


CMS ECAL

Crystal productionCrystal delivery determines ECAL Critical PathSuppliers:

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 Last Barrel crystal delivery Feb 2007 Last Endcap crystal delivery Jan 2008

30000

35000

40000

45000

50000

55000

Feb-05 May-05 Sep-05 Dec-05 Mar-06 Jul-06

BTCP Deliveries

30000

35000

40000

45000

50000

55000

Feb-05 May-05 Sep-05 Dec-05 Mar-06 Jul-06

BTCP Deliveries


CMS ECAL

Crystal Quality Assurance

BTCPSIC

SICLight Yield

Automatic control of:• Dimensions• Optical Transmission • Light yield • Longitudinal uniformity

CERN INFN/ENEARome

BTCP

Transmissionat 420 nm


CMS ECAL

Crystal Radiation ResistanceLight loss is characterised by an ‘induced absorption’

Under irradiation at room temperature, a dynamic equilibriumforms between formation and annealing of colour centres.

Light loss saturates at a value that depends on dose-rate

CMS specification requires: μ420 < 1.5 m-1

(Under uniform (lateral) 60Co irradiation at >30 Gy/hr)

Under LHC-like conditions for the Barrel (~0.15 Gy/hr) Light yield loss ≾ 6%

0

10

20

30

40

50

60

70

80

300 350 400 450 500 550 600 650 700

initialafter irradiation

wavelength (nm)

T(%

)

)(T

)(Tln

L

1)(

rad

0

xtl

Verification:

BTCP: Use correlation between sharpness ofabsorption edge and radiation hardness(Check with sample irradiations)

SIC: All crystals irradiated by producer 0 5 Light Yield Loss (%)


CMS ECAL

PhotodetectorsBarrel - Avalanche photodiodes (APD)

Two 5x5 mm2 APDs/crystal- Gain: 50 QE: ~75%- Temperature dependence: -2.4%/OC- Delivery complete

20

40m

Endcaps: - Vacuum phototriodes (VPT)More radiation resistant than Si diodes (with UV glass window)- Active area ~ 280 mm2/crystal- Gain 8 -10 (B=4T) Q.E.~20% at 420nm- Delivery ~80%

= 26.5 mm

MESH ANODE

VPT Delivery & Test status


CMS ECAL

On-detector electronics

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 Level1 accept)

Trigger Tower (TT) Very Front End card (VFE)

Front End card (FE)

Trigger Sums

Data

x12

x6

x1MGPA

Logic

12 bit ADC

2

1

0

12 bits

2 bits

HV

APD/VPT

VFE architecture for single channel

VFE x 5

MB

FE

LVR


CMS ECAL

On-detector electronics: status

ASICs in 0.25 m IBM CMOS TechnologyVery high yield (typically >85%)

ADC MGPA FENIXStatus:All ASICS procured and testedAll systems for 30 SMs are tested & burned-in Full Barrel set available for most componentsEndcap components following close behind

30 MeV 45 MeV

View of a SuperModule (SM)

showingon-detector electronics

Noise distribution for 1700 channels of SM13


CMS ECAL

Off-Detector electronicsClock & Control System (CCS)

Data Concentrator Card (DCC)

Trigger Concentrator Card (TCC)

Status:CCS finished for whole ECALDCC in production for BarrelTCC for Barrel: Production startedTCC For Endcaps: Schematic finishedFirst board by September

LV Power supplies:~60% of Barrel ordered (rest soon)Order for Endcaps in 2007


CMS ECAL

0.1 oC0.1 oC

at APD when electronics is powered-up(Worst case: Bottom Supermodule)

Cooling &Temperature Stability

Power dissipation of Barrel on-detector electronics ~160 kW

Combined temperature sensitivity of (crystal + APD):

Stabilise temperature to better than ± 0.05 OC

Chilled water at 50l/s

C/4%dT

dA o

LYAPD

Water manifold and pipes on SM

Cooling bars in direct contact with electronic cards


CMS ECAL

Laser light monitoring (1)

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%) 0.95

Correlation between transmission losses for scintillation light

and laser light

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

Simulation of crystal transparency evolution at

LHC (L =2x1033cm-2s-1)- based on test beam

irradiation results


CMS ECAL

Laser light monitoring (2)

APD

Light is injected through fibres into the front (Barrel) orrear (Endcap) of each crystal

F1 F2

PIN FE

LaserS

PWO

F1 F2

PIN FE

LaserS

PWO

440 nm796 nm

An optical switch directs light to one half-supermodule orone quarter Dee at a time

Resolution before irradn / after irradn and correction


CMS ECAL

Construction: Barrel

Sub-module: 10 crystals

Super-module: 1700 crystals

2 Regional Centres: CERN and Rome

Module: 400/500 crystals

Assembly status:26/36 bare SMs assembled15/36 SMs completed Production rate 4/month

Bare SM SM with cooling


CMS ECAL

Construction: Endcaps

Production statusAll mechanical parts delivered

Endcap crystal production starts in summer 2006

Backplates successfully test mounted on HCAL

Dee (½ endcap): 3662 crystalsSupercrystal: 25 crystals


CMS ECAL

Preshower detectorRapidity coverage: 1.65 < || < 2.6 (End caps) Motivation: Improved 0/ discrimination

• 2 orthogonal planes of Si strip detectors behind 2 X0 and 1 X0 Pb respectively

• Strip pitch: 1.9 mm (63 mm long)

• Area: 16.5 m2 (4300 detectors, 1.4 x105 channels)

High radiation levels - Dose after 10 yrs:

• ~ 2 x1014 n/cm2

• ~ 60 kGy

Operate at -10o C


CMS ECAL

Status of Preshower Detector

Micromodules

Ladders

System motherboards- production finished by end 2006

System Tests Ongoing- 8 ladders shown here

Mechanics

All ES “complete disc” elements ready for installation at end 2006(before the beam pipe)

Off-Detector Readout ElectronicsFirst module alreadyprototyped – 12-channeloptical receiver (optoRx)

Production completed~September 07

D.B

arn

ey

Pre-series underwayProduction by mid 2007

Preshower on schedule forinstallation at end of 2007


CMS ECAL

Mip deposits ~250MeV(increase APD gain from 50 to 200)

Cosmic Muon Test & CalibrationCosmic muons Each SM operated with cosmic rays for ~1 week

Intercalibration: 1-3% (stat) depending on η

Muons through full crystal

Event: 4161 Cry: 168 Status:10 SM Calibrated


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 Q are gain and quantum efficiency of the photo-detectors

cele is the calibration of the electronics chain

Intercalibration from Laboratory Measurements

= 4.2%Test beam vs Lab IntercalibrationRatio:Test beam/Lab


CMS ECAL

Barrel construction schedule

Reduced time 3→2months

EB+ Surface Installation

EB- Surface Installation

(12/18)

EB- U’ground Installation

(6/18)

EB+

EB-


CMS ECAL

Supermodule InstallationInsertion at point 5

2 SMs inserted 27 April for magnet test

SM Rails on HB+

Gap HB+/HB- ~ 1mm

ECAL Barrel installation


CMS ECAL

Endcap Construction ScheduleAssembly plan assumes last EE crystal delivered end Jan 08.

Aim is to have Endcaps installed for 2008 Physics Run

All cables and services are already installed

Goal: D1 Sept07, D2 Nov07, D3 Jan08, D4 Apr08

ECAL Endcap installation


CMS ECAL

Summary

High resolution electromagnetic calorimetry is a central feature of CMS

The construction of the Barrel ECAL is in the final phase

All mechanical components are delivered for the Endcap ECAL

Crystal delivery sets the schedule for both Barrel and Endcap

The Pre-shower detector is on course for completion as planned

Supermodules are being commissioned and calibrated with cosmic rays

The CMS ECAL will meet its design goals – see next talk!


CMS ECAL

Spares


CMS ECAL

Calibration strategy

Lab measurements Pre-calibration

70 80 90 100 GeV

Reference pre-calibration of few SM with 50/120 GeV electrons in test beam (<2%)

Finally: calibration to < 0.5% with W + e in ~2 months

Test Beam LY

Lab

LY

Test Beam LY – Lab LY

= 4.0%

Initial pre-calibration by ‘dead reckoning’ based on lab measurements (~4%)

In-situ calibration

• Precision with 11M events• Limit on precision

0 0.5 1.0

Inte

r-ca

libra

tion

pre

cisi

on

% -symmetry

w/jet trigger (ET > 120 GeV)

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)

Z e + eBarrel

-ring inter-calibration andZ e + e cross-calibration (~1% in 1 day)

Documents

CMS ECAL Elba May 2006 R M Brown - RAL 1 The Status of the CMS Electromagnetic Calorimeter R M Brown On behalf of the CMS ECAL Group