marco musy
DESCRIPTION
Aerogel as Cherenkov radiator for RICH detectors. Marco Musy. INFN and Universit y of Milano-Bicocca. Pylos, June 2002. The LHCb experiment. Proton-proton interactions at √ s = 14 TeV at LHC. Particle ID needed between 1-150 GeV/c. Two RICH systems with 3 Cherenkov radiators. - PowerPoint PPT PresentationTRANSCRIPT
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Marco MusyMarco Musy
INFN and University of Milano-Bicocca
Pylos, June 2002
Aerogel as Cherenkov radiatorAerogel as Cherenkov radiator for RICH detectorsfor RICH detectors
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The LHCb experimentThe LHCb experiment
Particle IDneeded between1-150 GeV/c
Proton-protonProton-proton interactions at √s = 14 TeV at LHC
Two RICHsystems with3 Cherenkovradiators
Acceptance: 10-300 mrad (bending plane)
10-250 mrad (non-bending plane)
RICH1
RICH1
RICH2
RICH2
Local Luminosity 2 x 1032 cm-2s-1
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3
Momentum
LHCb RICHes detectors
LHCb RICHes detectors
RICHRICH22 RICHRICH11
m RICHRICH11
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Aerogel as Cherenkov radiator
Aerogel as Cherenkov radiator
• Light, solid quartz-like structure SiO2
• Physical properties: low density, = 0.15 g/cm³ n = 1.01 ÷ 1.10,
(n = 1 + 0.20)
A = 95.88 ± 0.04, C = (6.44 ± 0.01) 10ˉ³ μm¯4 /cm A = 91.97 ± 0.05, C = (7.22 ± 0.01) 10ˉ³ μm¯4 /cmA = 88.18 ± 0.06, C = (6.95 ± 0.01) 10ˉ³ μm¯4 /cm
Novosibirsk
tile 10x10 cm²tile 7x8 cm²tile1 + tile2
Aerogel type :• Novosibirsk, Boreskov Institute of Catalysis, Russia (hygroscopic)
• SP30 Matsushita Electric works Ldt, Japan (hydrophobic) T = A e-Cd/4
A is the long transmittance
C is the clarity coefficient
8cm
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Ageing tests with γAgeing tests with γ 60Co (E= 1.3 MeV, 1.7 MeV)
Dose : 420 rad/min
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1 year LHCb operation
Ageing tests with protonsAgeing tests with protons
Source of radiation: Proton beam 24 GeV/cFlux : 9 109 p/cm2/s Spot size : 2 x 2 cm2
Depletion in Transmittance of ~1% after 1 year run(w.r.t. non irradiated sample taken as a reference)
13
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Humidity testsHumidity testsExpose hygroscopic aerogel tile to humid air (70%)
Measure water absorption through weight
Measure Transmittance in range 200-800 nm
Loss of 30% at 300 nm Loss of 15% at 400 nm Loss of 8% at 500 nm
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TestTest beam Set-up at CERNTestTest beam Set-up at CERN
Beam from CERN-PS: πˉ and p/π in the range 6 – 10 GeV/c (Δp/p = 1%)
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Quantum Efficiency of the 4 photocathodes > 20% (=280-380nm)
• Bialkali photocathode, K2CsSb• Fountain shaped electric field, demagnification factor ≈ 2.3• Silicon pad sensor 2048 pixels (16 sectors x 128 pads 1x1 mm² 2.3x2.3 mm² granularity on ph.cathode)
Hybrid Photo Detectors
Hybrid Photo Detectors
AEROGEL test beam
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Aerogel
Glass filter
Place holder
Rayleigh scattering Refraction on the boundaries Light absorption Light detection on photocathode Photocathode transparency...
All relevant processes are considered in the simulation:
Beam axis
photons
Geant4
Aerogel tile
Mirror
Photo Detectors
Silicon layers
Monte Carlo Monte Carlo descriptiondescriptionMonte Carlo Monte Carlo descriptiondescription
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Sector #4
Sector #8
Ring region
Out of ring
sect 4
sect 8
Test beam resultsTest beam resultsTest beam resultsTest beam results• 9 Gev/c π¯ beam• 4 cm aerogel Novosibirsk• noise/pad < 2%
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Photoelectron yieldPhotoelectron yieldPhotoelectron yieldPhotoelectron yield
Number of ph.electrons
Novosibirsk4 cm aerogel8 cm aerogel
On ring
• Integrate signal across the measured arcs and compare with Monte Carlo• Evaluate nr. photoelectrons: - on ring, |R-R| < 3σ - out of Cherenkov ring
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Novosibirsk No filter
Filter D263
4 cm 8.3 ± 0.310.0 ± 1.1
5.6 ± 0.26.4 ± 0.7
8 cm10.7 ± 0.412.9 ± 1.1
8.4 ± 0.38.9 ± 1.0
Photoelectron yield Photoelectron yield cont’dcont’dPhotoelectron yield Photoelectron yield cont’dcont’d
Contributions to total error:• background subtraction (±1σ): ~ 5%• inefficient or noisy pads : ~ 4%• definition of ‘active region’ (±1mm): 2%• separation of on-ring/off-ring (±2mm): 3%• signal losses outside ADC thresholds (±1σ): 3%
DataMC
results are normalised to 2π acceptance
on-ring
off-ring
Npe
8 cm
4 cm
8 cm
4 cm
No filterD263
4 cm(off-ring)
1.00 ± 0.100.81 ± 0.08
0.57 ± 0.040.55 ± 0.04
8 cm(off-ring)
1.10 ± 0.101.06 ± 0.11
0.94 ± 0.070.84 ± 0.10
results are in units of 10¯²/cm²
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Ring reconstructionRing reconstruction
Thickness No filter Filter D263 Glass
θc σθ θc σθ θc σθ
4 cm 250.0 5.4248.7 4.0
247.1 5.0246.8 3.0
243.6 5.3243.2 3.8
8 cm 246.8 5.8245.0 3.9
245.4 4.8243.7 3.0
246.0 5.3 --
6 cm 250.2 8.7 250.9 5.8 251.3 5.4
8 cm 249.5 9.8 250.3 6.2 --
Data
MC
Data
Novosibirsk
Matsushita
rad
• Study resolution as a function of - filter type - aerogel thickness - aerogel type
• Results per single photoelectronsingle photoelectron are (mrad):
-- Data-- Monte Carlo4cm Novosibirsk (no filter)
θc
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Ring reconstruction Ring reconstruction cont’dcont’d
• Contribution to angular resolution is determined with the simulation:
• Resolution is expected to scale as A/√N + k (in the 3σ ring region)
Sourceσ (mrad)
Pixelling 1.3
Chromaticity 2.5
Point spread func.+ Emission point
1.1
Beam divergence
0.7
Allignement 2.2
TOTAL 3.8
-- Fit to data
Resolutions differ by ~20-40% in MC with respect to the Data.Still under investigation.
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/p separation at
PID performancePID performance
8 GeV
8 GeV
6 GeV
10 GeV
rad
SINGLE ph.e.
6.1
4.8
3.1
θ
~30,000 events
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PID performance cont’dPID performance cont’d
• Evaluate separations Nσ = Δθ/σθ, scaling with the Npe and extrapolate to the total acceptanceEnergy θp θπ Nσ
6 GeV194.0±7.8
243.6±2.9
9.3
8 GeV216.4±4.1
244.3±2.8
8.1
10 GeV224.8±3.0
242.8±2.3
6.8
π-ring
p-ring
Clear π/p separation
• For 4 cm aerogel + filter:
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ConclusionConclusion The use of aerogel as Cherenkov radiator has
become reliable in high energy particle physics
Test beam has shown a photon yield which agrees with the Monte Carlo expectations
Good PID ability in the momentum range 6 – 10 GeV/c
Further studies are on the way