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Neutron induced thermal cross-section of naturally occurring Tantalum (Ta) has been analyzed by using four different Ta samples with thickness 4.0, 2.0, 1.0 and 0.5 mm (respectively equivalent to 0.0224, 0.0111, 0.0055, and 0.0025 atoms/barn) at the Pohang Neutron Facility, Republic of Korea. The PNF consists of a 100 MeV electron linear accelerator (LINAC), a water cooled Tantalum (Ta) target, 12.06 m TOF path length, four position automatic sample changer controlled remotely by the CAMAC data acquisitions systems, and a 6 LiZnS(Ag) inorganic scintillator as a neutron detector. The distance from the water cooled Ta target to the sample changer is 5.4 m. To reduce the gamma flash originated from the neutron target we have employed a neutron-gamma separation system based on their different pulse shape. The samples were highly pure (~99.9 %). In order to estimate the background and also to calibrate the energy we used notch filter of Cobalt (Co), Indium (In), and Cadmium (Cd) that has a large resonance peaks within our analyzed energy region. The area of the each samples of notch filter was 100 × 100 mm, and the thickness were 0.5 mm for Co and Cd; and 0.2 mm for the In. To get more events, experiments were done around 110 hours. The unwanted events were deleted from the real events by fitting with black resonances events of notch filter. The weighted mean of the measured thermal total neutron cross-section of Ta was compared with the existing experimental as well as evaluated nuclear data files.

Abstract. The Pohang Neutron Facility based on an electron linear accelerator was operated for the neutron total cross section measurements by using the pulsed neutrons produced in a water-cooled Ta-target with a water moderator. The neutron total cross sections of Ta and Mo were measured in the neutron energy region from 0.01 eV to 100-200 eV by using the time-of-flight method. A 6 LiZnS(Ag) glass scintillator with a diameter of 12.5 cm and a thickness of 1.6 cm was used as a neutron detector. The neutron flight path from the water-cooled Ta target to the neutron detector was 12.1 m. The background level was determined by using notch-filters of Co, In, Ta, and Cd sheets. In order to reduce the gamma rays from Bremsstrahlung and those from neutron capture, we employed a neutron-gamma separation system based on their different pulse shapes. The present measurements of Ta and Mo are in general agreement with the evaluated data in ENDF/B-VI. Cross sections for residual radio-nuclide production by proton-induced reactions on natural molybdenum were measured from their respective threshold energies to 42 MeV by using the MC-50 cyclotron at KIRAMS. The activation method and a stacked-foil technique using high-resolution HPGe gamma-ray spectrometry were applied to determine the excitation functions. The reactions induced on Al and Cu foils were used to monitor the parameters of the proton beam. The present results are in generally good agreement with the earlier reported data and with the calculations based on the ACILE-IPPE code.