The Neutron Emission from a Generator operating at 300 kV

The measurement of neutron emission by three independent methods is described, namely, (a) reduction to thermal neutrons and measurement of the radioactivity induced by these neutrons in rhodium, (b) measurement of the intensity of γ rays emitted when the neutrons of thermal energy combine with protons to form deuterium nuclei, and (c) measurement of the ionisation produced by the fast neutron beam in air. The three methods lead to consistent results. The emission is found to be about 106 neutrons/microcoulomb of 320 kV ions. Currents of 700–900 μA of 300 kV ions, and later 500 μA of 360 kV ions have regularly been obtained, so that the dependable steady output of the generator is at present equivalent to about 30 curies of radon and beryllium. The energy absorption in tissues at the nearest point to the target at which biological material may be placed is, under good working conditions, about equal to that due to 2 r/min. of gamma radiation.