Development of the Fast Timing Panda Barrel Time-of-Flight Detector
Publication author reference:
Thursday, 4 February, 2021
The Barrel Time-of-Flight Detector (B-ToF) is a timing detector for the Panda experiment which is currently under construction at the Facility for Antiproton and Ion Research (FAIR) in Darmstadt, Germany. In fixed target p̄p collisions, with antiprotons accelerated up to a momentum of 15 GeV/c producing a center of mass energy of up to 5.5 GeV, open questions of hadron physics will be studied. This effort includes charmonium spectroscopy and the search for exotics and hybrids as well as the study of hypernuclei and of hadrons in matter. In this context the B-ToF complements the particle identification information of the DIRC detectors and provides valuable information for particles in the lower momentum range up to about 1 GeV/c via relative time-of-flight measurements. A >1800 mm long transmission line PCB connects the SiPMs on the scintillators to the front-end electronics and provides mechanical support to the scintillator tiles acts as the backbone of the detector. In order to determine the best performing layout three prototype iterations are examined and tested for the crosstalk level and signal attenuation effects. While the crosstalk is negligible in all design iterations an amplitude reduction of (11.7 ± 0.5) % is observed for the newest board prototype using low loss materials. This is well above the attenuation of a standard coaxial cable. The employed connections lead to a doubling of the signal rise time. The effect of this on the time resolution is yet to be determined. To achieve intended functionality a highly granular and efficient detector design is necessary providing a time resolution of below 100 ps. The detector is made up of 16 identical sections each carrying 120 scintillating tiles, which are read out by an array of four SiPMs connected in series. This work presents time resolution scans using a 90 Sr source over the entire scintillator surface in order to evaluate the detector performance and determine the optimal scintillator tile thickness. Comparing four 3 mm to 6 mm thick scintillator tiles, the measurements show that a 5 mm thick scintillator providing a mean time resolution of 52.3 ps with a spread of ±5.9 ps over the entire surface, is the optimal choice for the detector. In addition the performance was verified in test beam measurements at the T9 beamline at CERN under conditions closer to the expected conditions in Panda using mixed particle beam mainly containing pions and kaons. Time resolutions of (55.8 ± 4.3) ps to (80.1 ± 1.5) ps were measured for detector modules utilizing SiPMs by different manufacturers.