M.V. Castillo

Physical properties of the TOF (Time of Flight) scintillation counters of Delphi

Abstract In this paper we report the physical properties of the time of flight (TOF) scintillator counters used for the DELPHI Experiment at CERN. We discuss the different choices studied for the wrapping of the counters in order to obtain best efficiencies for light transmission. A very good agreement of the performances of the counters has been found with the results of an original Monte Carlo program. The main characteristics of the TOF counters of DELPHI are: an effective light attenuation length of 135 cm, effective light speed of 15.91 cm/ns, a time resolution of 1.2 ns, and an efficiency for detection of minimum ionizing particles of 99.9%.

A method for calibration and test of the time-of-flight detectors for delphi

Abstract We describe a method for calibration and test of large-area TOF counters using cosmic radiation. We applied the method to the time-of-flight system of the DELPHI detector at the LEP e + e − storage ring, made of scintillation (NE110) counters (20 × 350 cm 2 ). The photomultipliers used (EMI 9902KB) reach an average gain of 5×10 8 at 1700 V and the time resolution achieved is 1.2 ns. Using this method we measured the counter efficiencies as a function of the position; we obtained 135 cm for the effective attenuation length and 40 photoelectrons for a minimum-ionizing particle crossing the center of the counter.