cms ecal elba may 2006 r m brown - ral 1 the status of the cms electromagnetic calorimeter r m brown...
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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
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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
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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
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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
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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
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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
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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
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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
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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
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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 (%)
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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
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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
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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
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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
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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
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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
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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
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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
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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
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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
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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
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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
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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
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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-
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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
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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
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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!
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CMS ECAL
Spares
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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)