Youngdo Oh

Radiography simulation on single-shot dual-spectrum X-ray for cargo inspection system

We propose a method to identify materials in the dual energy X-ray (DeX) inspection system. This method identifies materials by combining information on the relative proportions T of high-energy and low-energy X-rays transmitted through the material, and the ratio R of the attenuation coefficient of the material when high-energy are used to that when low energy X-rays are used. In Monte Carlo N-Particle Transport Code (MCNPX) simulations using the same geometry as that of the real container inspection system, this T vs. R method successfully identified tissue-equivalent plastic and several metals. In further simulations, the single-shot mode of operating the accelerator led to better distinguishing of materials than the dual-shot system.

Measurement of the Neutron Total Cross Sections of Natural Palladium by Using Pulsed Neutrons at Pohang Neutron Facility

The neutron total cross-sections of palladiums are measured in the neutron energy region from 0.1 eV to 500 eV by using time of flight method at the Pohang Neutron Facility. The Pohang Neutron Facility consists of an electron linac, a water-cooled tantalum target with a water moderator, and a 12 m long time-of-flight path, and is producing pulsed neutron beam from 65 MeV electron as 10~15 Hz repetition rate. The neutron detector is using a 6Li-ZnS(Ag) scintillator with a diameter of 12.5 cm and a thickness of 1.6 cm. Natural palladium metal plates with 5 × 5 cm2 in area and 0.5 mm, 1 mm in thickness, are used for the neutron transmission measurement. The background level is determined by using a notch-filter of Co, In, and Cd sheets. The measurements are compared with other measurements and the evaluated data in ENDF/B-VII.0.

Measurements of keV-Neutron Capture Cross-Sections and Capture γ-rays of 105Pd

The neutron capture cross-sections and capture γ-rays of 105Pd were measured for keV-neutron using the 3-MV Pelletron accelerator of the Research Laboratory for Nuclear Reactors at the Tokyo Institute of Technology. Pulsed neutrons were produced from the 7Li(p,n)7Be reaction, and the incident neutron spectrum on a capture sample was measured by neutron time-of-flight method with a 6Li-glass detector. The capture γ-rays were detected with a large anti-Compton NaI(Tl) γ-ray spectrometer. A pulse-height weighting technique was applied to measure the capture γ-ray pulse-height spectra to derive capture yields. The capture cross-sections were obtained by using the standard capture cross-section of 197Au. And we obtained the γ-ray energy spectrum of capture γ-ray by the pulse-height unfolding method. The present results were compared with the previous measurements and the evaluated data of ENDF/B-VII, JEFF-3.1, and JENDL-3.3.