Verification of Angular Properties of a Divergent Pencil Beam of the Prometheus Therapeutic Facility

A method for determining angular characteristics of a spread of a pencil proton beam, associated with the nonuniform distribution of the initial momenta of particles, is examined. Considering this phenomenon is crucial when planning patient irradiation and conducting radiobiological experiments, because angular characteristics directly affect the size of the field during particle transport through air or other media. Experimental data are also compared with Monte Carlo simulations performed with the TOPAS MC software package using the obtained parameters. The results demonstrate good agreement and validate the described method.