Study on Fragment Production by Protons and Neutrons and its Effects to the Materials and Living Bodies

辐射引起的半导体器件的软、硬误差是现代信息社会面临的严重问题。为了追踪这一问题，我们开展了以下工作：（1）发展了测量数十MeV核子碎片产生截面的实验技术;（2）获得了重要核素的系统实验数据;（3）评价了碎片产生的理论模型及其对材料和生物体的影响。在碎片测量方面，采用了1）布拉格曲线计数器（BCC）和2）能量飞行时间（E-TOF）方法，并从信噪比、动态范围和效率等方面对方法进行了改进，实现了质子和中子碎片的测量。本文首次获得了中子诱发碎片产生的数据，并将脉冲高度范围扩大了一倍左右。我们采用了新的正负极时间差信息，降低了碎片识别的阈值能量 ...更多信息 B）提出一种估算穿透BCC敏感体积的破片初始能量的方法。通过研制具有同心圆分段阳极的BCC以及相应的碎片识别和本底降低的改进，提高了中子数据。对于体心立方技术难以测量的低能粒子，我们采用微通道板和半导体探测器构建了E-TOF谱仪.利用研制的装置，我们进行了70 MeV质子和65 MeV中子的碎片产生的测量。碎片数据是从氦到氧在0度的中子和在30，60，90，135度的质子。我们比较了我们的实验碎片光谱与理论计算和评估碎片生产，以评估其有效性和问题。总的来说，模型与实验结果存在较大的偏差，有待进一步改进。少

Soft errors and hard errors of semiconductor devices by radiations are of serious problems in mode information society. To trace the problem, we carried out the followings : (1) Development of experimental technique to measure the fragment production cross sections for ten's of MeV nucleons, (2) acquisition of systematic experimental data of important nuclides, and (3) evaluation of theoretical models for fragment production and its influence on the materials and living bodies.1. For fragment measurement, we adopted 1) a Bragg curve Counter (BCC) and 2) energy-TOF(E-TOF method), and realized the measurement of fragments for protons and neutrons by improving the method with respect to signal-to-noise ratio, dynamic range and efficiency. The neutron induced-fragment production data is the first one in the world We extended the pulse-height range up to about twice by a)lowering the threshold energy of fragment identification by newly adopting the information on the anode-cathode time-diff … More erence (corresponding to range), and b)developing a method to estimate the original energy of fragment which penetrated the sensitive volume of BCC. The data for neutrons were upgraded by the development of BCC with a segmented anode of concentric circle and according improvement in fragment identification as well as background reduction. For low energy particles which are difficult to measure with the BCC technique, we constructed and adopted an E-TOF spectrometer employing a micro-channel plates and semiconductor detectors.2. Employing devices developed, we conducted measurement of fragment production for 70 MeV protons and 65 MeV neutrons. Fragment data were obtained from helium to oxygen at 0-deg for neutrons and at 30, 60, 90, 135-deg for protons.3. We compared our experimental fragment spectra with theoretical calculations and evaluations for fragment production to evaluate their validities and problems. Generally, the models showed serious disagreement with experiment and should be improved greatly. Less