Performance of the PANDA Barrel DIRC Prototype
1GSI Helmholtzzentrum für Schwerionenforschung GmbH, Darmstadt2Goethe-Universität Frankfurt
Marko Zühlsdorf1,2
for the PANDA Cherenkov Group
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Facility for Antiproton and Ion Research
11/12/2014 IEEE 2014 NSS/MIC
HESR
SIS 100/300
SIS18
RESR/CR
30 GeV Protons70 MeV
p-Linac
p Target
107 p/s @ 3 GeV
CollectingAccumulating
Precooling
AcceleratingCooling
100m
PANDA
Darmstadt, Germany
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AntiProton ANnihilation at DArmstadt
12 m
• Hadron physics experiment at FAIR• Wide range of fields
(e.g. charm physics, exotics, hypernuclear physics, …)
• Cooled antiprotons up to 15 GeV/con a fixed target
• Almost 4π coverage
target
• Hadronic PID in the center part covered by two DIRC detectors
• PANDA Barrel DIRC for polar angle range 22° - 140°• Pion/kaon separation up to 3.5 GeV/c
DIRC counter used successfully at BaBar
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p
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Detection of Internally Reflected Cerenkov Light
Condition for Cherenkov radiation:
• Always some Cherenkov photons totally internally reflected
• Propagation to the readout end of the radiator bar
• Focused on readout plane
• High optical surface quality
→ Cherenkov angle information conserved
• Synthetic fused silica
• Radiation hard
• Optically homogeneous
• Optically transparent
• Low dispersion with refractive index
Marko Zühlsdorf
511/12/2014 IEEE 2014 NSS/MIC
PANDA Barrel DIRC
Baseline Design (based on BaBar)
• Barrel radius: 47.6 cm
• 80 radiator bars, synthetic fused silica
• Bar dimensions: 1.7 cm × 3.2 cm × 240 cm
• Expansion volume:
• 30 cm depth
• mineral oil
• 15k - 20k channels of MCP-PMT
• Expected performance:
• Single photon Cherenkov
angle resolution: 10 mrad
• At least 15 detected photons
for track
radiator
readout electronics
Design Options
Radiator, focusing optics, expansion volume, ...
focusingoptics
expansion volume
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Baseline design working solution for PANDAAlternative designs to improve performance and reduce cost
RadiatorOne wide plate instead of 5 narrow bars per segment• Fewer pieces to be polished• Less strict requirements for optical and
mechanical quality of side surfaces
Potential significant cost reduction butPID capability not proven
Expansion volume (camera)One synthetic fused silica prism per segment instead of oil tank• Better optical properties• Smaller detection surface
Fewer photon sensors neededLess readout channelsPID capability not proven
DIRC Design Options
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30 cm
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Photon Sensors
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Requirements:• Single photon sensitivity, low dark count rate• High photo detection efficiency• Fast timing: 100 ps• Operation in magnetic field (1T)• Long lifetime: 0.5 C/cm²/yr
Promising candidates: MCP-PMTs, MAPMTs, SiPM
Ongoing ageing tests show improvement of MCP-PMT lifetime(poster and talk J. Schwiening, N07-12; N36-1)
(poster J. Rieke, N24-31 on High Resolution MCP-PMTsfor the PANDA Disc DIRC)
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DIRC Optics
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Radiator Quality:• DIRCs have tight mechanical requirements on flatness,
squareness, and parallelism of the radiator surfaces• Surface roughness 10 – 20 Å rms• Production difficult, potentially expensive
Worked with vendors in Germany, Russia, USA, and Japan to produce a number ofradiators using different fabrication techniques.
125 cm
30 cm
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Geometrical Reconstruction
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radiator detection plane
20° track polar angle 140°
20° track polar angle 140°
10
m
rad
30
10
m
rad
30
trac
k az
imut
h an
gle
trac
k az
imut
h an
gle
Geometrical reconstruction uses location of bar and pixel to determine photon vector in the radiator.
Works well for narrow bars but fails for wide plates
Width of radiator not negligible anymore
5 narrow bars, unfocused (MC Simulation)
3 wider bars, unfocused
inspired by BaBar DIRC
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Probability density functions (pdf) can be generated with ~100k Monte Carlo tracks with same parameters and saved in histograms.
Probability Density Functions
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22° polar anglep = 3.5 GeV/c
π K
In 3 dimensions (x, y, t) hit patterns show differences between particle species
πK
PMT map, with 5 x 3 sensors, 64 pixels eachx
y
normalized PDF for a specific pixel
π sampleK sample
Inspired by Belle II TOP
MCSimulation
Likelihood ratio test lnLK-lnLP
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Prototype Tests
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Prototypes tested in 2008, 2009, 2011, 2012, 2014
2012 Prototype with narrow bars CERN PSmixed hadron beam 1 – 10 GeV/c
Determined photon yield and single photon Cherenkov angle resolution for different bars and focusing optics over wide angular range.
First tests with plate prototypeBeam data Simulation
2012 setup
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2012 Prototype Test
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Simulation Beam data Beam data
Beam data
σ = 13 mrad
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2014 Prototype Test
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122.5 cm
Pion beam1.7 GeV/c
PrototypeBeam time at GSI; 5 weeks in summer 2014
2014 prototype is similar to a module of the final detector
5 x 3 Planacon MCP-PMT960 pixels (in total >1200 readout channels)
Wide plate w/ and w/o focusing lensNarrow bar with different lenses
Simulation has just started
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Preliminary Results
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Narrow Bar Data
New 3-component lens with better focusing and no air gap to reduce photon loss
No comparison with simulation yet but data shows typical folded ring structure
Beam data, 125 deg:
SiO2
NLAK
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IEEE 2014 NSS/MIC 15
Preliminary Results
11/12/2014
Wide Plate
Simulation:
Geant 4
Radiator plateCylindrical lens
120° polar angle1.7 GeV/c pions
pixelated:
true locations:
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Preliminary Results
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Wide Plate Data:
First glimpse on occupancies with raw cuts on timing and event multiplicity
Simulation predicts ~20 hits/track
Simulation:
Beam data:
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Summary and Outlook
Summary• The Barrel DIRC is a key component of the PANDA particle identification system. • Baseline design with narrow bars and high-refractive lens meets PANDA PID
goals.• Cost optimization identified two design alternatives (wide plate, solid fused silica
camera), to be validated with simulation and prototype tests.• A first look at the 2014 prototype data shows promising results for radiator plate.
Outlook• Improve simulation to better match beam data• Validate plate reconstruction approach• Measure PID performance in mixed hadron beam
at CERN in summer 2015
Decision on a design for PANDA Barrel DIRC TDR in early 2016
11/12/2014
Marko Zühlsdorf
IEEE 2014 NSS/MIC 18
Summary and Outlook
Summary• The Barrel DIRC is a key component of the PANDA particle identification system. • Baseline design with narrow bars and high-refractive lens meets PANDA PID
goals.• Cost optimization identified two design alternatives (wide plate, solid fused silica
camera), to be validated with simulation and prototype tests.• A first look at the 2014 prototype data shows promising results for radiator plate.
Outlook• Improve simulation to better match beam data• Validate plate reconstruction approach• Measure PID performance in mixed hadron beam
at CERN in summer 2015
Decision on a design for PANDA Barrel DIRC TDR in early 2016
11/12/2014
Thank you!
t x
PD plate top view
Y. Arita, March 9, 2013,QFPU Final International Forum
Belle II TOP