MEASUREMENTS OF NEUTRON SPALLATION CROSS-SECTIONS OF C-12 AND BI-209 IN THE 20 TO 150-MEV ENERGY-RANGE

The neutron spallation cross sections of C-12 and Bi-209 have been mea sured in the quasi-monoenergetic p-Li-7 neutron fields in the 20- and 150-MeV energy range. The irradiation experiments were performed at fo ur cyclotron facilities: (a) the Institute for Nuclear Study (INS), Un iversity of Tokyo; (b) the Cyclotron and Radioisotope Center Tohoku Un iversity; (c) the Takasaki Research Establishment (TIARA), Japan Atomi c Energy Research Institute; and (d) the Institute of Physical and Che mical Research (RIKEN). The neutron spectrum has been measured with th e time-of-flight method using an organic liquid scintillator, and the absolute value of peak neutron fluence has been estimated from the act ivation method of lithium target at INS, RIKEN, and the proton recoil counter telescope at TIARA. The cross-section data of C-12(n,2n)C-11 a nd Bi-209(n,xn) (x = 3,12) reactions are reported. Our experimental da ta were compared with other experimental data [only for C-12(n,2n)C-11 and 209Bi(n,3n)Bi-207 reactions] and the ENDF/B-VI high-energy file d ata. The comparison showed good agreement between our data and others. Our data of Bi-209(n,xn) reactions above 20 MeV and of C-12(n,2n)C-11 reactions above 40 MeV are the first experimental data and will be ap plied to high-energy neutron spectrometry for the Pi spallation detect or.