Thermal Neutron Flux Measurement by Counting Conversion Electrons from 134mCs Generated in a CsI Scintillator

A new method to measure low intensity neutrons such as secondary neutrons generated in radiotherapy has been developed. In the proposed method, thermal neutron flux is determined by measuring the conversion electrons from 134m Cs generated in a CsI(Tl) scintillator irradiated by neutrons. Because the generated 134m Cs is contained in the scintillator as internal sources, the emitted conversion electrons fully stop in the scintillator and counted with high efficiency. The thermal neutron flux in the neutron radiography facility of the Kindai University\u27s research reactor, UTR-KINKI, was measured by the proposed method. The cadmium difference method was used to separate the contributions of thermal and epi-thermal neutrons. The result was in good agreement with the one obtained by the conventional gold foil activation method. It was concluded that the proposed method is useful for the measurement of thermal neutron flux

Symphony in B minor

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Experimental evaluation of validity of simplified Monte Carlo method in proton dose calculations

It is important for proton therapy to calculate accurately dose distributions in treatment planning. Dose calculations in the body for treatment planning are converted to dose distributions in water and the converted calculations are then generally evaluated by the dose measurements in water. In this paper, proton dose calculations were realized for a phantom simulating a clinical heterogeneity. Both dose calculations in the phantom calculated by two dose calculation methods, the range-modulated pencil beam algorithm (RMPBA) and the simplified Monte Carlo (SMC) method, and dose calculations converted to dose distributions in water by the same two methods were verified experimentally through comparison with measured distributions, respectively. For the RMPBA, though the converted calculations in water agreed moderately well with the measured ones, the calculated results in the actual phantom produced large errors. This meant that dose calculations in treatment planning should be evaluated by the dose measurements not in water but in the body with heterogeneity. On the other hand, the results calculated in the phantom, even by the less rigorous SMC method, reproduced the experimental ones well. This finding showed actual dose distributions in the body should be predicted by the SMC method

A Two-dimensional Transmission Counter with A Backgammon-Drift Read-Out Technique

A new type of two-dimensional position sensitive gas counter for transmission counter with a backgammon-shaped flat electrode has been developed. The two dimensional position read-out can be achieved with the combination of the backgammon-shaped flat electrode read-out. as horizontal position and the drift time measurement read-out as vertical position. The gas counter is designed as a transmission trajectory counter that can be used to determined angle of incident charged particle in the charged particle detecting system. To check the characteristics of this gas counter, test experiments are performed with a coincidence plastic scintillation counter and p - ray source of 90Sr