Neutron beam transport by using a magnetic lens and multi-capilary fibers

高强度的窄束中子束将开辟广泛的中子利用领域。我们研究了两种聚焦中子束的方法。一种是利用六极磁场的中子磁透镜，另一种是多毛细管光纤。对于磁透镜，我们首先测量了通过透镜的中子强度，发现模拟和实验的聚焦强度存在2个因素的差异。我们试图解释原因，我们发现，由于强磁场的强大作用力，透镜系统中存在一些失真，这将导致磁体组件之间的间隙。这些差距降低了强度。我们成功地研究了磁透镜对中子束的强迫和平行作用，在该系统中，两个透镜串联排列。对于这样的系统，我们需要中子自旋翻转来改变两个透镜之间的中子自旋的方向。我们利用自旋翻转器观测到了中子聚焦和散焦的证据。其次，我们研究了中子在多毛细光纤中传输的波长依赖关系，以了解利用白光的有效性。开发了一个三维模拟程序来分析输运特性。传输强度取决于光纤的半径，也取决于光纤设置的曲率。长波中子的透射率随着半径的增大而增大。模拟表明，传输的波长依赖关系不能用光纤的理想状态来解释，需要在光纤中引入波动等失真。这些数据对制造使用多毛细光纤的设备非常有用。

Narrow neutron beam with high intensity will open wide variety of neutron utilization fields. We studied two methods to focusing the neutoron beam. One is neutron mzgnetic lens by using 6 pole magnetic field, and the other is multi-capilary fiber.About magnetic lens, first we measured the neutron intensity through the lens and found that there exist factor 2 difference in focusing intensity between simulation and experiment. We tried to explain the reason of We found that there existed some distortion in the lens system due to strong force of high magnetic field and that this would cause gaps between magnet components. These gaps reduced the intensity. Succeedingly, we studied a function of the mfagnetic lens to forcus and pararell the neutron beasm, in which system two lenses are arranged in a series. For such a system we need neutron spin flipper to change orientation of the neutron spin between the two lenses. We observed the evidence of the neutron focusing and defocusing by using the spin flipper. This suggest the system works as neutron focusing and pararelling device.Second, we studied the wavelength dependence of neutron transmission through a multi-capirally fiber in order to know the effectiveness for utilization of white beam. A three dimensional simulation code was developed to analyze the transport characteristics. Transmission intensity depend on the radius of the capirally and also on the curvature of the fiber setting. The transmission of longer wavelength neutrons increases with the radius. Simulation indicated that the wavelength dependence of transmission could not be explained by ideal condition of the fiber and we needed to introduce distorsion in the fiber, such as waving. These data are very useful to make devices using multi-capiraly fiber.