Аннотация:The purpose of this research was precision statistical simulation of multi-particle radiation transport using a realistic 3D model of clinical setup prototype and the systems of slot-hole collimators for on-line monitoring of Bragg-peak position at a proton therapy complex Prometheus to define of an available detecting accuracy and the choice of its optimum parameters. Numerical simulation of the experiments was carried out based on the RTS&T high-precision radiation transport software package using files of evaluated nuclear data from ENDF/B VIII.0 library. Results: To determine the error of the longitudinal Bragg peak monitoring, a series of 24 calculations was performed using different sequences of pseudo-random numbers to construct trajectories of particles in the calculation system. When using 3 slits, the RMS-error in determining the longitudinal coordinate was 1.5 mm. Keywords: radiation transport, Monte Carlo method, radiation therapy, medical accelerators, Bragg peak verification, mathematical modeling, irradiation planning, detection techniques.