Abstract: A high energy neutron generator for use in neutron therapy.The generator comprises a source for charged particles (preferably protons) with an energy level equal to at least 15 MeV, a target constituted by at least two lithium deuteride elements, whose thickness is such that under the impact of the charged particles, neutrons with an energy level equal to at least 15 MeV are largely produced in the forward direction, and target cooling means constituted by means for the circulation of a gas which does not chemically react with lithium deuteride. This generator may also comprise a collimator for defining an irradiation field of a patient and a permanent magnet able to deflect the charged particles not absorbed by the target towards a stopping unit positioned in and integrally formed with one wall of the collimator.