A Prototype for the PANDA Disc DIRC

DIRC2013: Workshop on fast Cherenkov detectors

September 2013

Benno Kröck, Avetik Hayrapetyan, Daniel Mühlheim,
Erik Etzelmüller, Julian Rieke, Klaus Föhl,
Michael Düren, Oliver Merle

Uni Gießen

PANDA detector

PANDA Disc DIRC

PANDA

hadron spectroscopy
fixed target experiment
antiproton-proton interactions
interaction rate up to 20 MHz
antiproton beam momentum: 1.5 . . . 15 GeV/c

Disc DIRC

particle identification: pion/kaon separation up to 4 GeV
very compact Cherenkov detector
magnetic field up to 1.5 T
high radiation dose

Panda Disc DIRC

Total internal reflection within disc

Focussing elements

Focussing for same angle

Focussing for different angle

Disc DIRC prototype

30 PMTs, Hamamatsu H10515-B100
16 pixels per PMT, 480 pixels in total
mirror on bottom edge

Prototype focussing optics

acryl glass
16 millimeters thickness
mirror coating

Prototype readout electronics

HADES data acquisition system
multi-purpose trigger and readout board, TRBv2 with HPTDCs
time of flight addon board, charge to width measurement with NINOs
128 channels in total

Charge measurement with TRBv2

Figure: charge to width measurement from electromagnetic calorimeter
NINO supports time over threshold
Two NINO channels combined for charge to width measurement
Threshold adjustable for each channel individually

CERN testbeam

Gas Cherenkov DIRC
Trig1 TOF1 Trig2 TOF2
mixed beam, 3.5 GeV/c: protons, pions, kaons, electrons, muons, . . .

Disc DIRC prototype

30 PMTs, Hamamatsu H10515-B100
16 pixels per PMT, 480 pixels in total
mirror on bottom edge

Cherenkov light in Disc DIRC

CERN testbeam

Gas Cherenkov DIRC
Trig1 TOF1 Trig2 TOF2
mixed beam, 3.5 GeV/c: protons, pions, kaons, electrons, muons, . . .

Particle identification with time of flight

Particle identification with gas cherenkov detector

Cherenkov light from pions, kaons, electrons, muons, . . .

Cherenkov light from protons

Photons' time of propagation in disc

Direct Cherenkov light from proton

Reflected Cherenkov light from protons

Direct Cherenkov light from pions, kaons, electrons, muons, . . .

Reflected Cherenkov light from pions, kaons, electrons, muons, . . .

Separated Cherenkov light patterns

Result of detector calibration

For each PMT pixel and each time bin:

detection propability for proton hit, straight photon path
detection propability for proton hit, path for photons reflected at mirror
detection propability for pion hit, straight photon path
detection propability for pion hit, path for photons reflected at mirror

Values are used for single event reconstruction with likelihood-ratio test.

Results of single event reconstruction

Schedule / radiant exposure

TEK module, 25600 cells: exposition in steps until total destruction
TEK module, 12800 cells: exposition in steps until total destruction
two TEK modules, 12800 cells: lesser dose to study self healing

Bonn:

protons
14 MeV

Disc DIRC:

expected fluence for the sensors in 1 MeV neutron equivalent: ≈10¹² per square centimeter
fluence in 14 MeV proton equivalent is 3.7 times less

Scattering chamber

vacuum: 10⁻⁵ millibar
proton beam defocussed to illuminate quadratic area
fluorescence monitor to check homogeneous illumination
beam could be wobbled as well to irradiate sensor line by line, might illuminate more uniformly, but was not used here

Dark count maps

Unfortunately not as homogenously irradiated as expected
Stripe pattern in center of pixel not yet understood, might be corellated with sensor electronics

Dark count distributions

Summary/Outlook

Disc DIRC prototype provides particle identification for protons and pions
Next prototype test with improved optics and electronics scheduled for November 2013
Radiation hardness of tested Philips dSiPMs not good enough for PANDA Disc DIRC