Pham Duc Khue

Method for detector calibration in radiation measurement of large samples

A method for detector calibration in radiation measurements of large samples by Monte-Carlo calculation is presented. This method is useful in the absolute radioactivity measurements when the relative method cannot be applied as suitable large standard samples are not available.

Measurement of isomeric yield ratios of 99m,g;101m,g;102m,gRh in the natPd(γ,pxn) reactions with the bremsstrahlung end-point energies of 50–70 MeV

The isomeric yield ratios of 99m,gRh, 101m,ggRh, and 102m,gRh isomeric pairs produced from the natPd(γ,pxn) reactions were measured with the bremsstrahlung end-point energies of 50-, 55-, 60-, 65-, and 70-MeV at the 100MeV electron linac of the Pohang Accelerator Laboratory, Korea. The measurements were carried out with the activation method in combination with off-line γ-ray spectrometry. In order to improve the accuracy of the activity measurements, the separation of the overlapping γ-rays and the necessary corrections for the counting losses were made. The new experimental results are compared with the theoretical values of the TALYS-1.6 code.

Study of the \(^{nat}\)Sm\((\gamma ,xn)^{143m,g}\)Sm Reactions Induced by Bremsstrahlung with End-point Energies Just above GDR Region

We investigate the energy dependence of the isomeric yield ratios for the natSm(γ,xn)143m,gSm reactions with bremsstrahlung energies of 40-, 45-, and 50-MeV, just above the giant dipole resonance (GDR) region by the off-line γ-ray spectrometric method. The bremsstrahlung photons were produced from the 100 MeV electron linear accelerator (linac) at the Pohang accelerator laboratory (PAL), Pohang, Korea. In order to improve the accuracy of the experimental results the necessary corrections were made. The present results are compared with similar literature data of the natSm(γ ,xn)143m,gSm reactions measured at various photon energies and of the natSm(n,2n)143m,gSm reaction induced by 14 MeV neutrons in order to examine the effects of an excitation energy and an input angular momentum.

Study of Multiple Photoneutron Reactions on 197Au Induced by 2.5 GeV Bremsstrahlung

We identified eight radionuclides Au, Au, Au, Au, Au, Au, Au, Au formed via the multiple photoneutron reactions Au(γ, kn)197−kAu with 2.5 GeV bremsstrahlung. The yields of radionuclides that decay by emitting γ-ray were measured using high purity germanium (HPGe) detector coupled to a PC-based multichannel analyzer. In order to improve the accuracy of the experimental results the necessary corrections were made. The obtained results are compared with reference data and the variations of the 197Au(γ,kn)197−kAu reaction yields according to incident bremsstrahlung energy and neutron multiplicity are also discussed.

Measurement of Thermal Neutron Capture Cross Section and Resonance Integral for the \(^{45}\)Sc\((n,\gamma)^{46}\)Sc Reaction with Pulsed Neutrons

Thermal neutron capture cross section and resonance integral for the 45Sc(n,γ)46Sc reaction were measured by the activation method using the 197Au(n,γ)198Au reaction as a single comparator. The high-purity scandium and gold samples with and without Cd cover with the thickness of 0.5 mm were irradiated in a pulsed neutron field of the 100 MeV electron linac of the Pohang Accelerator Laboratory (PAL). The induced activities in the activated foils were measured with a well calibrated HPGe detector. In order to improve the accuracy of the experimental results the effect of the non-ideal epithermal spectrum was taken in to account by determining the neutron spectrum shape factor (α), and the corrections for the thermal (Gth) and the resonance (Gepi) neutron self-shielding effects, the γ-ray attenuation (Fg) and the γ-ray coincidence summing effect were made. The thermal neutron cross-section for the 45Sc(n,γ)46Sc reaction has been determined to be σo = 27.6 ± 0.8 barn. By assuming the cadmium cut-off energy of 0.55 eV, the resonance integral for the 45Sc(n,γ)46Sc reaction has been determined to be Io = 12.7±0.7 barn. The present results are compared with the reference data and discussed.

An empirical formula for (n, 2n) reaction cross sections in the neutron energy range of about 14.5 MeV

The (n,2n) threshold reaction cross-sections, available in the literature are analysed for nuclei with 20≤Z≤92 in the neutron energy range of about 14.5 MeV. An empirical formula based on multiple regression technique is proposed for quick estimation of the (n,2n) reaction cross sections. The results obtained are compared with experimental data and those from other empirical formulae as long as byN-Z systematic. The validity of this formula is discussed.

Cross-sections of (n,p) reaction at a neutron energy of 14–15 MeV

The (n,p) reaction cross-sections induced by 14–15 MeV neutrons have been analyzed on the basis of available data taken from the literature, using the multiple regression technique. An empirical formula describing the dependence of (n,p) reaction cross-sections on 5 parameters: neutron (N) and proton (Z) number, asymmetry factor ((N−Z)/A) where A=N+Z, neutron and proton binding energies (Bn, Bp) has been found. Its validity is checked and discussed.