In proton therapy, it is important to very accurately determine the range of the proton beam. Recently it was found that this range can be determined from the distribution of the prompt gammas generated along the beam's passage. The Compton imaging technique can be considered to be a promising candidate for accurate determination of prompt gamma distributions, in that it produces a better image for higher-energy gammas when compared with conventional mechanicalcollimation-type imagers. In the present study, the Compton imaging technique was evaluated by experimentally obtaining Compton images of relatively high-energy gamma sources positioned in an anthropomorphic phantom. Preparatory to that, two point-like gamma sources, 137 Cs (662 keV) and 22 Na (1275 keV), were placed in the brain region of the phantom at different depths and imaged using a double-scattering Compton camera. The Compton camera, recently developed as a prototype system, consists of two position-sensitive semiconductor detectors as scatterer detectors and a scintillation detector as an absorber detector. The evaluated imaging and angular resolutions for the source energies of 662 and 1275 keV were 13.7 mm and 5.9 ˚FWHM and 11.4 mm and 3.8 ˚FWHM, respectively.

ABSTRACT.A simulation study for the separation of rare isotopes such as beryllium and aluminum was performed for a new beam line to be attached to the 3MV Tandetron accelerator at the accelerator mass spectrometry (AMS) facility of Seoul National University in Korea. The new beam line will also be used for other scientific applications, namely, ion implantations, Rutherford backscattering, and nuclear astrophysics experiments. It mainly consists of 30° and 100° deflection dipole magnets and drift spaces. A transfer matrix for the beam line was determined by the TRANSPORT code. Simulation of the rare isotope separation was performed by a ray tracing method using the TURTLE code. The simulation results, including the effect of the energy degrader, provide feasibility for the separation of isobars with small mass differences in 10 Be-10 B and 26 Mg.

While it is customary to use solid samples for measuring the 14C/12C ratio, it is sometimes necessary to handle liquid or gas samples. Motivated by a scientific purpose to count radiocarbon yields in deuterated acetone irradiated with energetic neutrons, we developed a new combustion system to treat liquid or gas samples. In contrast with the typical combustion system using CuO for solid samples, the new combustion system uses high-purity O2 (99.999%) gas. As an initial investigation, we combusted deuterated acetone (acetone-d6, certified 100.0 atm % D) to make CO2 under the ambient O2 pressure. The resulting CO2 gas then went through the reduction process to form graphite for further accelerator mass spectrometry (AMS) measurement.

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