A 14 MeV neutron tube for radiotherapy.

Abstract

A sealed tube is being developed as a neutron source for radiotherapy. Essential features of such a source for clinical use are an output of at least 1012 neutrons/second to ensure a reasonably short treatment period and a life of several hundred hours to minimize maintenance. The design principles and performance of this and earlier tubes are outlined. The device contains an ion source which provides a mixture of deuterium and tritium ions in equal proportions. These are accelerated to 250 keV, with which energy they strike a thick target film where they generate 14 MeV neutrons according to the reaction: The use of this mixture of deuterium and tritium atoms which constantly recirculate between the target and ion source avoids the usual progressive decrease in output due to isotopic dilution in the target. This, together with the development of a high-capacity gas replenisher and very thick target films, provides very long operational lives at high neutron output rates. At the time of presentation of this paper, outputs in excess of 3 × 1011 neutrons/second were achieved and extrapolation of the tube performance data indicated that the design output and life would be achieved.