Development and application of a neutron polarizing and focusing system based on magnetic field gradients

在本研究中，我们开发了一种基于中子磁矩与磁场相互作用的中子极化聚焦装置，其中我们分别使用四极和六极磁体来极化和聚焦中子。该装置可用于具有聚焦几何形状的小角偏振中子散射实验。中子偏振器是一个扩展的哈尔巴赫式四极磁铁，内径为15毫米，长度为2200毫米。测得四极磁体内部的磁场梯度为~ 150t /m。在JRR-3的束流线C3-1-2-1处设置了由四极磁体和两个六极磁体组成的中子偏振聚焦装置，进行了脉冲中子偏振聚焦试验。结果表明，我们可以将脉冲中子聚焦在0.8 ~ 1.05 nm的波长范围内。确定了在J-PARC的小角中子散射仪上安装中子偏振聚焦装置。

In this study, we have developed a neutron polarizing and focusing device based on interaction between a neutron magnetic moment and a magnetic field, where we use quadrupole and sextupole magnets to polarize and focus neutrons, respectively. The device is considered useful for small angle polarized neutron scattering experiments with focusing geometry. The neutron polarizer is an extended Halbach-type quadrupole magnet with an inner diameter of 15 mm and length of 2,200 mm. The magnetic field gradient inside the quadrupole magnet was measured to be ~150 T/m. We set up the neutron polarizing and focusing device composed of the quadrupole magnet and two sextupole magnets at the beamline C3-1-2-1 of JRR-3, and performed pulsed neutron polarizing and focusing test. As the result, we could focus the pulsed neutrons in the wavelength range from 0.8 to 1.05 nm. The neutron polarizing and focusing device has been determined to be installed to a small angle neutron scattering instrument of J-PARC.