EVALUATION OF TIME MEASUREMENT PRECISION IN THE COUNTING TEST FACILITY OF THE BOREXINO EXPERIMENT

The Counting Test Facility, the prototype of the Borexino experiment i nstalled at the Gran Sasso Laboratory, is an unsegmented liquid scinti llator detector in which the spatial reconstruction of the events play s an important role. The event localization is performed through a tim e of flight technique, which exploits the time informations of the sig nals of the photomultipliers detecting the photons escaping from the 4 tons scintillation sphere in the center of the detector; thus the unc ertainty affecting the time measurement of each anode output represent s the ultimate limit on the achievable spatial resolution. This uncert ainty has been evaluated through analytical and Monte Carlo calculatio ns based on the actual characteristics of the photomultipliers and of the scintillator adopted for the detector. In this work we present in detail the model assumed to perform the calculations together with the main results obtained.