Thermal neutron capture cross-section and resonance integral measurements of ¹³⁹La(n,$\gamma$)¹⁴⁰La and ¹⁴⁰Ce(n,$\gamma$)¹⁴¹Ce using a Am-Be neutron source

Abstract.

Thermal neutron capture cross-sections and resonance integrals of ¹³⁹La(n,$\gamma$)¹⁴⁰La and ¹⁴⁰Ce (n,$\gamma$)¹⁴¹Ce are measured with respect to reference reactions ¹⁹⁷Au(n,$\gamma$)¹⁹⁸Au and ⁵⁵Mn(n,$\gamma$)⁵⁶Mn using the neutron activation technique. Measurements are carried out using neutrons from an Am-Be source located inside a concrete bunker. Two different methods are used for determining self-shielding factors of activation foils as well as for finding the epithermal neutron spectrum shape factor. For ¹³⁹ La with reference to ¹⁹⁷ Au and ⁵⁵ Mn the measured thermal cross sections are $9.24 \pm 0.25$ b and $9.28 \pm 0.37$ b, respectively, while the measured resonance integrals are $12.18 \pm 0.67$ b and $11.81 \pm 0.94$ b, respectively. For ¹⁴⁰ Ce with reference to ¹⁹⁷ Au and ⁵⁵ Mn the measured thermal cross sections are $0.44 \pm 0.01$ b and $0.44 \pm 0.02$ b, respectively, while the measured resonance integrals are $0.55 \pm 0.03$ b and $0.54 \pm 0.04$ b, respectively. The present measurements are compared with earlier measurements and evaluations. Presently estimated values confirm the established ¹³⁹La(n,$\gamma$)¹⁴⁰La cross-sections. The presently measured thermal capture cross-section ¹⁴⁰Ce(n,$\gamma$)¹⁴¹Ce , though lower than the evaluated data, is having higher accuracy compared to previous measurements with large uncertainties. The resonance integral measured is higher (like most previous measurements) than most evaluations requiring a revision of the evaluated data.