Development of Neutron Compton Scattering and Neutron Absorption Methods

本项目的目的是利用KEK（KENS）的脉冲散斑中子源，研制一台中子康普顿散射谱仪和一台中子共振吸收谱仪。通过对本项目的电气系统、γ探测器和数据采集系统的进一步改进，成功地实现了这两台性能良好的谱仪。这两台谱仪分别被命名为RAT和DOG，安装在KENS上，利用RAT谱仪可以获得基态波函数psi_0r（^^*）的信息。本文用原子吸收光谱法测定了KHCO_3中氢原子波函数的空间分布。得到的分布是非常相似的理论分布，这可以从氢键化合物的新模型推导出来。结果表明，氢势可以描述为Mose型势和非对称势的叠加，DOG谱仪使杂质浓度的测定和杂质运动的观察成为可能，即使在小分子化合物中也能进行。例如，使用DOG，我们成功地确定了半导体Sb/Si中杂质Sb的浓度，并观察到Sb运动的温度依赖性。Sb的浓度约为0.001%。其次，我们观察了高Tc化合物La_（2-x）CuO_4中杂质（Ba）运动的温度依赖性，发现在Tc附近有相当大的变化。第三，我们观察了杂质在激光辐照下的运动，研究了电子-声子相互作用对杂质的影响。这三项典型研究的结果表明，DOG技术为“杂质研究”开辟了一个新的科学领域，并为工业上重要的无损检测和微量化学分析提供了进一步的可能性。

Aims of this project is to develop a neutron Compton scattering spectrometer and a neutron resonance absorption spectrometer, which have been investigated, for a long time, utilizing a pulsed spallation neutron source in KEK (KENS). By the further improvements of the electric system, gamma-ray detectors and data-acquisition system in this project, we succeeded to realize these two spectrometers with good performances. Those were named as RAT and DOG,and installed in KENS.RAT spectrometer makes it possible to obtain the information about the ground state wave function psi_0r (^^*). Using the RAT,We tried to determine the space-distribution of hydrogen wavefunction in KHCO3. The obtained distribution is very similar to the theoretical distribution, which can be derived from the new model for the hydrogen bonded compounds. This result show that the hydrogen potential can be described as a superimpose of the Mose-type potential and an asymmetric potential.DOG spectrometer makes it possible to determine the concentration of the impurity and to observe the impurity motion even in the small compound. For example, using the DOG,we succeeded to determine a concentration of the impurity Sb in the semi-conductor Sb/Si and to observe the temperature dependence of the Sb-motion. The concentration of Sb was about 0.001%. Second, we observed the temperature dependence of the impurity (Ba) motion in the high-Tc compound La2-xBaxCuO4, and found a considerable large change around the Tc. Third, we observed the impurity motion under the Laser-irradiation, and studied effects of the electron-phonon interaction on the impurity. The results of those three typical studies indicate that the DOG can open a new scientific field of the 'impurity research', and that the DOG can also provide the further possibility of nondestructive testing and microchemical analysis which are very important in the industrial.