ToF counters

Eng Up Kedr

A hodoscope of scintillation counters for time of flight (TOF) is destinied in order to make a fast trigger, to help in fast tracks finding, to identify the charged particles both using TOF and ionization losses. Moreover this hodoscope will be useful for rays pattern which converted before the calorimeter.

The barrel system consists of 32 scintillation counters covered the angular region 41 - 139 degrees which corresponds to a solid angle of 0.75x4pi sr, the average distance from the beam is 71 cm. Each counter of 1640x141x10 mm in size, is viewed through bent lightguides by two photomultipliers placed inside of the iron yoke. The screens were designed to suppress the tension of magnetic field to the value of not more than 0.1 mT within the PM position.

Endcaps are made of one layer of scintillation counters, of 520x20 mm, trapezioidal shape, viewed by one PM XP2262. In each endcap 32 counters are used.

As a scintillator in TOF system BICRON BC-408 is applied. Average number of photoelectrons is about 100 per one PM.

Measurements in runs of 1998 gave a time resolution better than 300 ps. Such a resolution allows to suppress effectively the background from cosmic particles and to separate pi- and K-mesons by time of flight up to 620 MeV/c momentum (at 2 sigma level).

Last modified on 19 February 2000