Measurement of neutron activation cross sections for major elements of water, air and soil between 35 and 70 MeV

Neutron activation cross sections between 35 and 70 MeV were measured by the activation method using a semimonoenergetic neutron field settled at the AVF cyclotron of the Cyclotron and Radioisotope Center(CYRIC),Tohoku University. Natural samples of N, O, Si and Na which were the major elements of water, air and soil were irradiated in this neutron field generated through the 7Li(p,n) 7Be reaction by 35, 50 and 70 MeV protons on thin Li target. Neutron yields were measured with the time-of-flight method using a calibrated NE213 organic liquid scintillator. From the induced activities measured with the HPGe detectors, we estimated cross sections of 14 N(n,2n)13N, 14 N(n,X) 11C, 14N(n,X) 7Be, 16O(n,2n) 15O, 16O(n,X) 13N, 16O(n,X) 11C, 16O(n,X) 7Be , 23Na(n,g) 24Na, 23Na(n,2n) 22Na, nat Si(n,X) 28Al, natSi(n,X) 29Al, natSi(n,X) 26Mg, natSi(n,X) 24Na and natSi(n,X) 22Na