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Tianchi Zhao
University of Washington
Concept of
an Active Absorber CalorimeterA Summary of LCRD 2006 Proposal
A Calorimeter Based on Scintillator and Cherenkov Radiator Plates Readout by SiPMs
Tianchi Zhao
University of Washington
Adam Para
Fermilab
March 12, 2006, LCWS06 Bangalore, India
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Energy Compensation
Reference:1. “Compensating hadron calorimeters with Cerenkov light” Winn, D.R. Worstell, W.A. , IEEE Trans. NS Vol 36 (1989) 334 2. “Hadron Detection with a Dual-Readout Calorimeter” N. Akchurina et al., NIM A 537 (2005) 537-5613. “Cherenkov Compensated Calorimetry”, Yasar Onel et al., 2004 LCRD Proposal
factorn compesatio : 1
sc
chsch E
EEE
Hadron energy Eh is given by:
Eh : Compensated hadron energy
Esc : Energy measured by plastic scintillators
Ech : Energy measured by cherenkov radiators
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Basic Idea of Active Absorber CalorimeterIn a sampling calorimeter based on active detector (scintillator)
+ absorber layers, partially replace absorber plates by cherenkov radiator and
read out both scintillation light and cherenkov light.• Thin plastic scintillator plates: Measure energy of both hadron and EM components of
hadron showers as in a standard sampling calorimeter
Cherenkov radiator
Plastic scintillator
Heavy structural layer
• Thick Cherenkov radiator plates: Measure mostly energies of EM components in hadron
showers in an active absorber calorimeter
• Both readout by WLS fiber and SiPM/MPPC
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Configuration Example Consider a 40 layer arrangement
Material LayersT
(cm)
Layer Thickness
(cm)No. of T
Plastic scintillator 40 80 40 0.5 = 20 0.25
Lead glass 30 30 30 2 = 60 2
Iron 30 16.8 30 0.5 = 15 0.89
Iron 10 16.8 10 2.5 = 25 1.49
TOTAL 40 120 4.63
20 mm lead glass
5 mm steel
~1.3 X0 25 mm steel
Last 10 layersFirst 30 layers 5 mm plastic scintillator
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Options for EM Calorimeter Section
15 mm PbF2
3 mm scintillator
2 mm tungsten
15 mm PbF2
3 mm scintillator
2 mm tungsten
20 layers
• Good EM energy resolution• Maintaining energy compensation
1. Any other EM calorimeter considered for ILC 2. A segmented active absorber calorimeter with dual energy readout
Example
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Transverse Segmetation
• Need Monte Carlo simulation to optimize the choice of segmentation for - EM section - Front part of hadron section - Back part of hadron section
• Minimum size of plates mainly limited cost considerations 3 cm × 3 cm (?)
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Number of p.e. measured by using cosmic ray muons
Lead glass: 2.4 0.5 p.e.
Bicron 408: 27 4 p.e. Ralph Dollan, 2004 Thesis
Cherenkov Light Readout by WLS Fiber
• Groove along 40 mm length
• White paper wrapped
• 1 mm BCF-91AWSL fiber
• One end open
• XP1911 PMT
(Average Q.E. ~ 13% for BCF-91A )
Bicron 408
6 x 6 x 30 mm3
P.E. yield of lead glass is about 5% of plastic scintillator
Lead glass SF57
10 x 10 x 40 mm3
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Cherenkov Light Yield of 1 Charged Particles
Forward
Cherenkov Radiator Density X0
(cm)
(cm)
Index of refractio
n
Absorption Edge (nm)
SF2 lead glass 3.85 2.76 38 1.65 330
SF6 lead glass 5.2 1.7 30 1.81 360
SF57 lead glass 5.5 1.5 28 1.85 370
PbF2 crystal 7.8 0.93 20 1.82 250
UVT acrylic 1 40 80 1.5 250• Lead glass was popular calorimeter material in LEP experiments
• Cast or extruded lead glass has the same light yield as cut/polished crystals
Plastic scintillator light yield
~ 10,000 photons/cm
Chrenkov light yield:
200 – 300 photons/cm
Isotropic
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Cherenkov Plate Readout by MPPC or SiPM
MPPC or SiPM WLS fiber
Cherenkov Radiator
2 cm
Target: Combined efficiency = η1 × η2 × η3 × η4 >1%
• η1 : probability of a photon hitting the core of a WLS fiber
• η2 : conversion efficiency of WLS fiber
• η3 : light trapping efficiency in WLS fiber
• η4 : MPPC/SiPM quantum efficiency
Cherenkov photon Photoelectrons
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Signals from a 1 Charged Particle
Number of P.E. = N0 x η1 x η2 x η3 x η4 = 400 x 1.6 % = 6.4
• Cherenkov light yield: N0 = 400 ’s in 2cm radiator
• Light collection efficiency by WLS fiber: η1 ~ 50%
• WLS fiber efficiency: η2 ~ 80%
• Assume η3 ~ 10% with mirror at far end of fiber
• MPPC Q.E.: η4 ~ 40 % (100 pixel device may be sufficient)
MPPCMirro
r
WLS fiber: high efficiency for blue light; emits green/yellow light to match MPPS
WLS fiber
Should be able to make reasonable measurements for high energy EM showers
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Basic structure
An Alternative Configuration
Material LayersT
(cm)
Layer Thickness
(cm)
No. of
T
Plastic scintillator 40 80 40 0.5 = 20 0.25
UVT Lucite 30 70.3 30 2 = 60 0.85
Uranium 30 10.5 30 0.5 = 15 1.43
Iron 10 16.8 10 2.5 = 25 1.49
TOTAL 40 30 120 4.02
20 mm lucite
5 mm uranium
25 mm steel
Last 10 layersFirst 30 layers
5 mm plastic scintillator
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Potential Advantages• Energy compensation for hadron showers on event by event basis
as demonstrated by the DREAM Project, but allowing for fine transverse and longitudinal segmentation
• Performance should be better than the dual r eadout calorimeter of Dream project since cherenkov radiator in our implementation is 2/3 of total volume!!
• Energy resolution should be better than a calorimeter based only on scintillator plates and should achieve the “required” jet energy resolution
• Tighter spatial spread of hadron showers recorded by Cherenkov radiator may help correctly assigning energy clusters in HCal to tracks that produced them, therefore, improving the results of PFA.
• Very flexible design options for material choices and segmentations
E/%30
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