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

简而言之，研究辐射对生物材料的影响的最终目的是保护一般和专业人员免受辐射照射，包括原子弹幸存者、核电站辐射工作人员、体检人员和操作人员。为了进行这种研究，必须准确地了解放射性对人体和生物材料的影响。最近，我国广岛大学放射生物学研究所研制出了能产生1.2 MeV以下中子的单能中子发生器，并开始研究其中子效应及其机理。在研究中子效应时，我们必须知道它的中子的特性。其中最重要的是能谱，为此有必要根据测量结果进行验证。我们测试了一些方法，如he3计数器，但它们还不够。在本研究中，我们采用最精确的“飞行时间（TOF）”方法。在进一步的研究中，我们测量了中子的飞行时间，并由此计算了它们的能量。该仪器由日清电器有限公司制造。为了使束流弯曲，我们采用5kV脉冲电源对束流进行切割。被切断的光束击中了一个锂靶。根据（p, n）反应，从锂靶发射脉冲中子。中子是由闪烁探测器探测到的。从斩波器和闪烁体的脉冲信号中，我们可以根据两个信号的时间差来测量中子的飞行时间。中子的能量由中子的估计速度决定。该装置安装在中子发生器系统中，获得的中子能量分析功率为20 ns，相当于500 keV中子分辨率的8%。作为这项研究的结果，我们几乎可以完成我们最初的计划。我们将更加努力，以获得更高的准确性。通过这个研究计划，我们可以确定精确的中子能谱。对生物物质的辐射效应机理的分析将比以往深入得多。少

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