Absolute calibration of accelerator beam energies by the crossover technique

An absolute method for the determination of the energy of a charged particle beam is described. The method is based on 0423 0450 V 2 scattering kinematics and exploits the variation with angle of the energy of particles scattered by elastic and inelastic processes 0423 0450 V 3 from different target nuclei. A determination of the angle at which particles scattered by two different reactions have the same 0423 0450 V 3 energy allows a precise calculation of the energy of the incident ion beam if the relativistic corrections are taken into account. A 0423 0450 V 3 simple system capable of supplying an absolute and accurate information on the beam energy in a short time has been designed and 0423 0450 V 3 tested. The system allows beam energy determinations over a wide energy range, from a few MeV up to several tens MeV and is not limited to some energy values in particular, in contrast with the use of resonance or threshold reactions. The system can in particular be employed for the calibration of accelerator beam energies in the energy interval typical of medium-energy commercial 0423 0450 V 3 cyclotrons, an increasing number of which are in operation in industry and in many fields of applied research. The paper briefly illustrates the theory underlying the “crossover” technique, describes the experimental apparatus and procedure and reports on experimental results for 12–36 MeV protons. The correction factors to be considered to fully exploit the accuracy of the technique 0423 0450 V 3 are discussed. The application of the method to the energy calibration of beams of deuterons and helium ions is described. A secondary and faster calibration procedure is also reported. This is derived from the main technique and can be routinely used once a number of energies have been determined and a sufficient data base of energy values has been built up. It is demonstrated that this secondary method is almost as accurate as the main technique.