time of flight detector

The forward spectrometer is complemented by a time-of-flight (TOF) detector, an essential component for particle identification because it provides flight-time information for both charged and uncharged particles. It is to cover the polar angular range up to 12 degrees at a distance of 5m from the target. The detectors of the former ELAN setup that had been in use until recently have been developping an unexpected inefficiency within the last 12 months and have been discarded. A replacement setup consisting of two walls made of detectors from the former SAPHIR experiment is currently under construction. These detectors are 14 vertically aligned 2700mm x 200mm x 35mm and 8 horizontally aligned 3400mm x 210mm x 60mm plastic scintillators, respectively, with photomultiplier readout at both ends. A subset of five of the shorter detectors has been very carefully tested using cosmic radiation in the framework of a bachelor thesis [1]. Another set of 12 detectors was subjected to tests within a diploma thesis [2]. All detectors show satisfying results. The with respect to the ELAN detectors reduced time resolution of approx. 500ps of the SAPHIR detectors will be compensated by adding 48 scintillators from the GRAAL experiment [3], consisting of 3000mm x 115mm x 30mm plastics with photomultiplier readout at both ends. A sample of 4 of these detectors has arrived in Bonn and is currently under investigation. The full setup is expected to be ready for data taking latest end of 2012.


[1] L. Schildgen, Bachelor thesis, Bonn (2012)
[2] P. Meiß, Diploma thesis, Bonn, in preparation
[3] O. Bartalini et al., Eur. Phys. J. A26 (2005) 399