The COSY-TOF barrel detector

A barrel-shaped scintillator hodoscope was developed as part of the time-of-flight spectrometer TOF operated at an external beam line of the cooler synchrotron COSY. The COSY-TOF spectrometer is used mainly to perform kinematically complete experiments on light meson production and proton-proton bremsstrahlung in proton-proton collisions for laboratory energies up to 2.5 GeV.
The newly developed scintillator hodoscope (BARREL1), one of several detector segments of the COSY-TOF spectrometer, consists of one layer of 96 scintillator bars of 15 mm thickness arranged to form a barrel with 3 m in diameter and 2.85 m in length.
For any given interaction process the TOF spectrometer allows to determine the velocity vectors of all charged ejectiles emerging from the target by measuring the time of flight between the start and the stop detector as well as the point of impact on the stop detector. For the BARREL1 detector the position information is obtained by two-sided light read-out of the scintillator bars. For minimum ionizing particles the spatial resolution was measured to be Delta z(FWHM) = 8 cm, corresponding to a polar angle resolution in the range 0.57 to 2.86 degrees, depending on the hit position. The binning in azimuthal angular direction amounts to 360/96 = 3.75 degrees. For the time-of-flight resolution of minimum ionizing particles a value of Delta t(FWHM) = 0.61 ns was obtained.