[en] Spin-polarized electrons have been generated from a GaAs crystal whose surface was coated with a NEA (negative electron affinity) layer. The electron polarization was measured using the Mott polarimeter. The work was done utilizing the photocathode test-stand in the Pohang Accelerator Laboratory. That stand was constructed to characterize GaAs photocathodes for use in PES (polarized electron source) development. The test-stand consists of a GaAs crystal, devices for NEA surface production, an electrostatic bend, and a Mott polarimeter. All components, except the polarimeter are contained in a extremely high vacuum (XHV) chamber that can provide a vacuum better than 5 X 10^-10 Torr. Circularly polarized photons are provided by a multi-color laser with quarter-wavelength plates. In order to have a clean surface on the GaAs crystal, which is essential for successful production of a NEA layer, we have adopted the method of hydrogen glow-discharge cleaning. With careful cathode cleaning and activation (NEA surface production), spin-polarized electrons are routinely generated with a quantum efficiency of 3.01 % and a polarization of 30.4 %.

[en] We measured the production cross-sections of ^99mTc, ^96(m+g)Tc, ^95mTc, and ^95gTc radioisotopes for proton-induced reactions on molybdenum by using a stacked-foil activation technique in the energy range of 10 - 30 MeV at the MC50 cyclotron of the Korea Institute of Radiological and Medical Sciences. Reactions induced on the aluminum and copper foils were used to monitor the parameters of the proton beam. The present measurements are in generally good agreement with the earlier reported data in the investigated energy region.

[en] The neutron total cross-section of natural Dy has been measured in the energy region from 0.025 eV to 100 eV by the neutron time-of-flight method at Pohang Neutron Facility, which consists of an electron linear accelerator, a water-cooled Ta target with a water moderator, and a time-of-flight path with an 11 m length. A ⁶Li-ZnS(Ag) scintillator with a diameter of 12.5 cm and a thickness of 1.5 cm has been used as a neutron detector and a metallic plate of Dy sample have been used for the neutron transmission measurement. The background level has been determined by using notch-filters of Co, Ta, and Cd sheets. In order to reduce the gamma rays from a Bremsstrahlung and that from a neutron capture, we have employed a neutron-gamma separation system based on their different pulse shape. The present measurements are in general agreement with the previous ones and the evaluated data in ENDF/B-VI. The resonance parameters of Dy isotopes (^161,162,163Dy) have been extracted from the transmission data by using the SAMMY code and compared with the previous ones

[en] As the first phase of applying the Monte Carlo technique, specifically using the GEANT4 toolkit, to clinical patient support, we modeled and simulated the beam delivery system of the proton therapy facility installed at the National Cancer Center (NCC), Korea. Thanks to the properly designed architecture of the GEANT4 toolkit to extend its application area, modeling the elements of the beam delivery system and of their dynamic behaviors was efficiently implemented. The simulation was validated over a treatment range of passive scattering mode in a water phantom by estimating the initial beam energy and by applying this information to a simulated therapeutic proton beam (termed the spread-out Bragg peak), resulting in good correlations with the measurement data.

[en] The Pohang Neutron Facility, which is based on an electron linear accelerator, has been equipped with a new CAMAC data acquisition system consisting of a neutron-gamma separation circuit and a four-position sample changer for nuclear data production and for basic science experiments using neutrons. The system has been tested by measuring the neutron flux and the neutron total cross-sections of natural W and Ti samples with the ⁶Li-ZnS (Ag) scintillator by using the neutron time-of-flight method. The measured neutron total cross-sections are compared with other measured data and the evaluation data in ENDF/B-VI. The present measurements are in generally good agreement with other data and the evaluated data.

[en] The neutron total cross section of natural Dy, Ag, and Sm has been measured in the energy region from 0.1 eV to 100 eV by the neutron time-of-flight method at Pohang Neutron Facility, which consists of an electron linear accelerator, a water-cooled Ta target with a water moderator, and a time-of-flight path with an 11 m length. A ⁶Li-ZnS(Ag) scintillator with a diameter of 12.5 cm and a thickness of 1.6 cm has been used as a neutron detector and metallic plates of Dy, Ag, and Sm samples have been used for the neutron transmission measurement. The background level has been determined by using notch-filters of Co, In, and Cd sheets. In order to reduce the gamma rays from a Bremsstrahlung and that from a neutron capture, we have employed a neutron-gamma separation system based on their different pulse shape. The present measurements are in general agreement with the previous ones and the evaluated data in ENDF/B-VI. The resonance parameters of Dy isotopes (^161,162,163Dy) have been extracted from the transmission data and compared with the previous ones

[en] The Pohang Neutron Facility, which consists of an electron linear accelerator, a water-cooled Ta target with a water moderator, and a time-of-flight path with an 11 m length has been operated since 2000. We report the status activities on the neutron total cross-section measurements in the neutron energy region from 0.01 eV to 100 eV by the neutron time-of-flight method at Pohang Neutron Facility. A 6Li-ZnS(Ag) scintillator with a diameter of 12.5 cm and a thickness of 1.5 cm has been used as a neutron detector. The background level has been determined by using notch-filters of Co, In, and Cd sheets. In order to reduce the gamma rays from Bremsstrahlung and that from neutron capture, we have employed a neutron-gamma separation system based on their different pulse shape. The present measurements for Ag, Hf, and Ta samples are compared with the previous ones and the evaluated data in ENDF/B-VI. The resonance parameters for Ag and Hf samples have been extracted from the transmission data by using the SAMMY code