Performance of the PANDA Barrel DIRC Prototype

1GSI Helmholtzzentrum für Schwerionenforschung GmbH, Darmstadt2Goethe-Universität Frankfurt

Marko Zühlsdorf1,2

for the PANDA Cherenkov Group

Marko Zühlsdorf

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Facility for Antiproton and Ion Research

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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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IEEE 2014 NSS/MIC 11

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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IEEE 2014 NSS/MIC 13

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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IEEE 2014 NSS/MIC 14

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

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Wide Plate

Simulation:

Geant 4

Radiator plateCylindrical lens

120° polar angle1.7 GeV/c pions

pixelated:

true locations:

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IEEE 2014 NSS/MIC 16

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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IEEE 2014 NSS/MIC 17

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