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Abstract  

Nondestructive measurements of γ-ray and X-ray emissions are often made to characterize special nuclear materials. Various computer codes are available to determine the relative isotopic composition of uranium or plutonium (along with certain other associated nuclides) from analysis of the spectra resulting from such measurements. MGA (Gunnink, Proceedings of the 9th ESARDA symposium on safeguards and nuclear management 167, 1987) and MGAU (Gunnink et al., Proceedings of the IAEA symposium on international safeguards 541, 1994) are among the major isotopic codes. The purpose of this study was to investigate MGA and MGAU performance versus energy resolution of the counting system.

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Abstract  

Excitation functions for the production of198mAu,198Au,198(m+g)Au, by (, 2pn) reactions on gold and isomeric ratios for198Au were determined experimentally. The method of activation of metallic foils was employed. The irradiations were performed in the isochronous cyclotron at Karlsruhe (Germany) with -particles at 90 MeV. Gamma-spectrometry by means of an intrinsic Ge detector was used to determine the nuclides produced. In addition, a comparison between the cross sections obtained and a calculation using the hybrid model of pre-equilibrium reactions, in combination with the statistical model development by ERNST is presented.

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Journal of Radioanalytical and Nuclear Chemistry
Authors: Md. Rahman, Kyung-Sook Kim, Manwoo Lee, Guinyun Kim, Youngdo Oh, Hee-Seock Lee, Moo-Hyun Cho, In Ko, Won Namkung, Van Nguyen, Duc Pham, Tien Kim, and Tae-Ik Ro

Abstract  

We measured isomeric-yield ratios for the 197Au(γ,n)196m,gAu reactions with bremsstrahlung energies of 50-, 60-, 70- MeV, and 2.5-GeV at the two different electron linac of the Pohang accelerator laboratory by using the activation method. The photons were produced when a pulsed electron beam hit a thin tungsten target. The well-known photoactivation method was used and hence the induced activities in the irradiated foils were measured with the high-resolution γ-ray spectrometric system consisting of lithium drifted high-purity Germanium detector and a multichannel analyzer. The measured isomeric-yield ratios for the 197Au(γ,n)196m,gAu reactions were (4.95 ± 0.51) × 10−4, (5.72 ± 0.72) × 10−4, (6.03 ± 0.50) × 10−4, and (9.27 ± 0.83) × 10−4 for 50-, 60-, 70-MeV, and 2.5-GeV bremsstrahlung energies, respectively. The present results measured with the bremsstrahlung energy higher than 60-MeV are the first measurement.

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Abstract  

Excitation functions for the production of194Au,195(m+g)Au,196(m+g)Au,198mAu,195gAu and199Au were determined experimentally. In addition, the yields of thick targets of these products were calculated and a comparison between the cross sections obtained using the hybrid model of pre-equilibrium reactions in combination with the statistical model of compound nucleus is presented. The method of activation of metallic foils was employed. The irradiations were performed in the internal beam of the isochronous cyclotron at Karlsruhe (FRG) with -particles at 90 MeV. Gamma-spectrometry by means of an intrinsic Ge detector was used to determine the nuclides produced.

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Summary  

Single neutron transfer reactions on 197Au induced by 12C and 16O at near Coulomb barrier energies have been studied using radiochemical and off-line gamma-ray spectrometric techniques. High spin yield fraction (HSF = σm/(σmg)) for 196m,gAu and formation cross section ratio (σ198196) of 198Au and 196Au have been determined for both 197Au+12C and 197Au+16O reactions at different excitation energies near the Coulomb barrier. The HSF of 196m,gAu and σ198196 values in both reactions are seen to sharply increase with increasing excitation energy near the Coulomb barrier and then slowly increase reaching a constant value at high projectile energy. These observations have been analyzed in terms of nuclear structural and kinematic parameters. A comparison the effects of Coulomb excitation and nucleon transfer process during heavy-ion interactions indicates a predominant effect of the latter process in the background of the Coulomb excitation. Observed reaction systematics seem to follow the quasi-elastic transfer process.

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