Bismuth-fission detectors for high energy nucleons: I. Registration characteristics

There is considerable current interest in the detection of high energy nucl eons around accelerators, spallation sources, and in cosmic rays. A detecto r that has its principal response at nucleon-energy above 50 MeV is provide d by the fission of Bi-209. The problem of limited sensitivity has been sol ved by: a) spark counting large detector areas, b) reducing the detector ba ckground by special counting procedures, c) using many replicates of a thin track detector between two Bi-209-radiators. Finally, the registration eff iciency has been evaluated and determined experimentally using proton beams with energies of 100, 150, and 250 MeV.