A system for charged particle therapy verification, comprising; - a detector, the detector comprises an array of low density hydrogen-rich plastic optically segmented organic scintillator elements wherein the array is arranged having a cross-section perpendicular to the length of the scintillator elements, the system being characterized by further comprising: - photodetector array, arranged at both ends of the scintillator elements, and - a processing unit in connection with the photodetector array, wherein the processing unit is configured to estimate the direction and energy of the incoming fast neutrons and gamma-rays, the system is configured for detection of secondary particles of both fast neutrons and prompt gamma-ray types emitted from a target irradiated with a charged particle beam, wherein the detector is configured to detect at least two consecutive elastic scatter collisions (3,4) for incident neutrons and at least two incoherent scatter collisions for incident prompt gamma-rays in different scintillator elements to achieve sufficient counting statistics for both particle types, and the processing module is configured to reconstruct momenta of recoil proton of said two consecutive elastic scatter collisions to reconstruct the incident neutrons' energy and incident angle located along an event line and estimate range landmarks obtained from both neutron and prompt gamma-ray profiles with sub-millimetric precision. - a detector, the detector comprises an array of low density hydrogen-rich plastic optically segmented organic scintillator elements wherein the array is arranged having a cross-section perpendicular to the length of the scintillator elements, the system being characterized by further comprising: - photodetector array, arranged at both ends of the scintillator elements, and - a processing unit in connection with the photodetector array, wherein the processing unit is configured to estimate the direction and energy of the incoming fast neutrons and gamma-rays, the system is configured for detection of secondary particles of both fast neutrons and prompt gamma-ray types emitted from a target irradiated with a charged particle beam, wherein the detector is configured to detect at least two consecutive elastic scatter collisions (3,4) for incident neutrons and at least two incoherent scatter collisions for incident prompt gamma-rays in different scintillator elements to achieve sufficient counting statistics for both particle types, and the processing module is configured to reconstruct momenta of recoil proton of said two consecutive elastic scatter collisions to reconstruct the incident neutrons' energy and incident angle located along an event line and estimate range landmarks obtained from both neutron and prompt gamma-ray profiles with sub-millimetric precision. - photodetector array, arranged at both ends of the scintillator elements, and - a processing unit in connection with the photodetector array, wherein the processing unit is configured to estimate the direction and energy of the incoming fast neutrons and gamma-rays, the system is configured for detection of secondary particles of both fast neutrons and prompt gamma-ray types emitted from a target irradiated with a charged particle beam, wherein the detector is configured to detect at least two consecutive elastic scatter collisions (3,4) for incident neutrons and at least two incoherent scatter collisions for incident prompt gamma-rays in different scintillator elements to achieve sufficient counting statistics for both particle types, and the processing module is configured to reconstruct momenta of recoil proton of said two consecutive elastic scatter collisions to reconstruct the incident neutrons' energy and incident angle located along an event line and estimate range landmarks obtained from both neutron and prompt gamma-ray profiles with sub-millimetric precision.