Absolute measurements of cross-sections of nuclear reactions induced by fast neutrons

Abstract

Nuclear reactions induced by 2.3 MeV and 14.7 MeV neutrons in some light and medium weigh elements (nitrogen, oxygenm, fluorine, phosphorus, calcium, iron, copper and selenium) have been investigated by activation techniques. The cross-section of (n,p), (n, t), (n, α) (n, 2n), (n, m(^1)) and (n, ɤ) reactions have neen measured, and are discussed with reference to the predictions of the nuclear models. The 2.3 MeV neutrons were obtained from the (^2)H(d, n) (^3)He reaction while those of 14 MeV were obtained from the (^3)H(d, n)(^4)He reaction. The deuterons were accelerated on a 200 KV Cockcroft-Walkton and a 400KV S.A.M.E.S accelerator. A method was developed to determine the absolute flux at both energies using the associated particles method. Recoil particles were counted on a silicon surface barrier detector mounted in the accelerator drift tubes. Absolute disintegration rates were determined by end-window proportional counters, annular liquid sample Geiger Müller counters and on various NaI(Tl) ɤ-ray scinitillation spectrometers. These were calibrated using sources which were standardised using 4πβ counting and or 4πβ/ɤ or β/ɤ coincidence techniques. The active species resulting from irradiation were separated radiochemically before further identification and determination by counters.