Measurement of the absolute neutron beam polarization from a supermirror polarizer and the absolute efficiency of a neutron spin rotator for the NPDGamma experiment using a polarized 3He neutron spin-filter
Measurement of the absolute neutron beam polarization from a supermirror polarizer and the absolute efficiency of a neutron spin rotator for the NPDGamma experiment using a polarized 3He neutron spin-filter
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DOI：
10.1016/j.nima.2018.03.055
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发表时间：
2018-07-01
影响因子：
1.4
通讯作者：
Wilburn, W. S.
中科院分区：
文献类型：
--
作者：
Musgrave, M. M.;Baessler, S.;Wilburn, W. S.
高通量、大面积中子束的束流极化特性的精确测量是许多中子物理实验的必要条件。基本中子物理束线（FnPB）是一束脉冲中子束，在NPDGamma实验中使用超反射镜偏振器进行偏振。极化中子束的通量类似于每秒每厘米（2）10（9）个中子，横截面积为10 × 12厘米（2）。该中子束的极化和安装在该束下游的RF中子自旋旋转器的效率通过中子透射通过极化He-3中子自旋过滤器测量。的SNS的脉冲性质使我们能够采用绝对测量技术的两个量，这不依赖于准确的知识的相空间的中子束或He-3极化的自旋过滤器，因此是感兴趣的任何实验慢中子束从脉冲中子源，需要知识的绝对值的中子极化。在这项工作中测量的极化和自旋反转效率是为NPDGamma实验完成的，该实验测量了在质子上捕获极化中子时违反伽马射线角分布相对于中子自旋方向的不对称性的宇称。讨论了实验技术、结果、系统效应和在中子俘获靶上的应用。
Accurately measuring the neutron beam polarization of a high flux, large area neutron beam is necessary for many neutron physics experiments. The Fundamental Neutron Physics Beamline (FnPB) at the Spallation Neutron Source (SNS) is a pulsed neutron beam that was polarized with a supermirror polarizer for the NPDGamma experiment. The polarized neutron beam had a flux of similar to 10(9) neutrons per second per cm(2) and a cross sectional area of 10 x 12 cm(2). The polarization of this neutron beam and the efficiency of a RF neutron spin rotator installed downstream on this beam were measured by neutron transmission through a polarized He-3 neutron spin-filter. The pulsed nature of the SNS enabled us to employ an absolute measurement technique for both quantities which does not depend on accurate knowledge of the phase space of the neutron beam or the He-3 polarization in the spin filter and is therefore of interest for any experiments on slow neutron beams from pulsed neutron sources which require knowledge of the absolute value of the neutron polarization. The polarization and spin- reversal efficiency measured in this work were done for the NPDGamma experiment, which measures the parity violating gamma-ray angular distribution asymmetry with respect to the neutron spin direction in the capture of polarized neutrons on protons. The experimental technique, results, systematic effects, and applications to neutron capture targets are discussed.