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In this research work, the cross-sections for the natAg(n,xn){106m,g,104m,g,105g}-Ag, natEr(n,xn){165,161}-Er and natEr(n,x){167,166g}-Ho reactions within the neutron energies of 14 to 37 MeV, the natCd(gamma,xn){115m,g,111m,109,107,105,104}-Cd and natCd(γ,x){113g,112,111g,110m}-Ag reactions in the bremsstrahlung end-point energies of 50 and 60 MeV were determined by using an activation and off-line gamma-ray spectrometry technique. For the better elaboration of the reaction cross-sections, uncertainties were also estimated and incorporated with the experimental data. The isomeric cross-section ratios (IR) of {104m,g}-Ag and {106m,g}-Ag for the natAg(n,xn) reactions and the {115m,g}-Cd for the 116Cd(γ,n) reaction were also obtained at the above mentioned neutron and bremsstrahlung energies. On the basis of the produced activities, the integral yield of cadmium and silver isotopes production from the natCd(γ,x) reactions were also estimated.
In the neutron induced reactions, the quasi-mono energetic neutron beams were produced from the 9Be(p,xn)9B reaction by using the proton beam energies of 25 to 45 MeV at the Korean Institute of Radiological and Medical Sciences (KIRAMS), Republic of Korea. Similarly, the bremsstrahlung was produced by hitting the high energy accelerated electron on a W target at Pohang Accelerator Laboratory, Republic of Korea. Monte Carlo simulation MCNPX code was used to simulate the neutron energy spectra, whereas Geant4 simulation code was used to simulate the bremsstrahlung spectra. For the neutron flux estimation, we used 27Al(n,alpha) monitor reaction for natural silver target and 197Au(n,xn) monitor reactions for natural erbium target. For the photon flux estimation, Au(γ,n) reaction was used for cadmium target.
Some of the cross-sections for the Ag(n,x), Er(n,x) and Cd(γ,x) reactions from the present work are the first time measurements. Similarly, the integral yield measurements of cadmium and silver isotopes production from the natCd(γ,x) reaction are also the first time measurements. Some of the reaction products of present work have various applications in medical, industrial and nuclear technological fields.
The nuclear reaction cross-sections for the natAg(n,xn){106m,g,104m,g,105g}-Ag, nat-165,161 nat-Er(n,x){167,166g}Ho, nat-Cd(γ,xn){115g,m,111m,109,107,105,104}-Cd reactions and the nat-Cd(γ,x){113g,112,111g,110m}-Ag reactions were also theoretically calculated by using the computer codes TALYS-1.8 and EMPIRE-3.2 malta. The experimentally determined reaction cross-sections and isomer ratios of the present work are found to be in general agreement with the theoretical values and with the values of evaluated nuclear data libraries. This indicates the validity and test of theoretical models as well. It is also observed that the theoretical and experimental reaction cross- sections increase sharply with increasing energies to a certain point and then decreases with increasing energies due to the opening of new reaction channels due to partition of excitation energy for different reaction channels.
The IR values of the {106m,g}-Ag, {104m,g}-Ag and {115m,g}-Cd from the present work in the nat-Ag(γ,xn) and 116-Cd(γ,n) reactions are compared with the similar data of nat-Ag(n,xn), nat-Pd(p,xn), nat-Rh(alpha,xn) and 116-Cd(n,2n) reactions of similar compound nucleus. In all these reactions, the IR values of {106m,g}-Ag, {104m,g}-Ag and {115m,g}-Cd increase with excitation energy. At the same excitation energy, the IR values are higher in the alpha-induced reaction than those in proton-, neutron- and photon- induced reactions. These two observations indicate the role of entrance channel parameters such as excitation energy and input angular momentum. However, at same excitation energy, it is surprise to see that in spite of very low input angular momentum of neutron (spin= 1⁄2), the IR values of {106m,g}-Ag, {104m,g}-Ag and {115m,g}-Cd in the nat-Ag(n,xn) and 116-Cd(n,2n) reactions are significantly higher than that in the nat-Ag(γ,xn) and 116-Cd(γ,n) reactions. This is due to the higher spins of the compound nuclei in the neutron induced reactions than in the photon induced reactions. This indicates the role of compound nucleus spin besides the effect of excitation energy.
Thesis Advisor: Prof. Guinyun Kim