[Experimental study of the relative biological effectiveness (R.B.E.) of a fast neutron beam (author's transl)].

A preliminary experimentation has been done with the synchrocyclotron (28 MeV deuton) in Lyon. The different characteristics of the beam have been determined through various dosimetric measurements. C57Bl mice have been irradiated with single doses and fractionated schedules (5 sessions). 7 day survival has been analysed. Comparison of neutron and cobalt gamma ray shows a R.B.E. of 1.95 for single dose and 2.5 for five fractions. This work is a confirmation of the effect of fractionation on the R.B.E. of the neutrons.