THE PRODUCTION OF ¹³N₂ BY 50-MeV PROTONS FOR USE IN BIOLOGICAL NITROGEN FIXATION

An experimental system for the continuous production of radioisotopic nitrogen, 13 N 2 , has been developed using the sector-focused cyclotron at the University of Manitoba. The radioisotope is produced by 50 MeV proton bombardment of 14 N 2 with powdered melamine as the nitrogen-containing target material. A trap system necessary for the removal of unwanted reaction products is described and details of experimental procedures involving changes in proton beam current and in state of beam focus are presented.Using the radioisotope, a number of microorganisms isolated from sub-Arctic soils of the Fort Churchill region have been examined for their nitrogen fixation potential. Several of these, including a species of Rhodotorula and a species of Pullularia in addition to bacterial forms, have demonstrated nitrogen fixation at a rate comparable with that shown by Azotobacter vinelandii.