Development of a method of neutron spectrum measurement for monoenergetic neutrons generated from an accelerator for the use of radiation biology

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The final purpose of the study radition effects for biological materials is, in short, to protect general and professional people from the exposure of radiation, for those of atomic bomb survivors, radiation workers in nuclear opwer plant and medical examinee and poerator. For this kind of study it is necessary to know precisely the radiobiological effects for ourselves and biological materials.Recently our Research Institute for Raciation Biology Hiroshima University developed monoenergetic neutron generator, which generate neutrons less than 1.2 MeV,and began to study the effect and the mechanism of the effect of its neutrons.In the study of neutron effects, we must know the characteristics of its neutrons. One of the most important one is the energy spectrum and for this it is necessary to verify according to the measurements. We tested some method such as a He3-counter, however, thev were not enough. In this study we apply the most accurate method of "time of flight (TOF)". In this … More study we measure flight time of neutrons and from this their energies are calculated.The apparatus was mede by Nissin Electric Co., Ltd. To bend the beam we used 5kV pulsed electric power source and chopped the beam. The chopped beam hit a lithium target. From the lithium target pulsed neutrons were emitted according to the (p, n) reaction. The neutrons were detected by a scintillation detector. From the pulse signals of the chopper and scintillator we can measure flight times of the neutrons from the time differences of both signals. The energy of the neutrons were determined by the estimated velocities of the neutrons.The apparatus was installed in the system of the neutron generator and analyzing power of the neutron energy was obtained as 20 ns, which correspond to the 8% of the resolution for 500 keV neutrons. WE could almost accomplished out initial plan as the results of this study. We will make more effort to obtain more accuracy. By this study plan we became to determine accurate neutron energy spectra. The analysis of the mechanism of the radiation effects for the biological substances will be able to make much more deeply than before. Less