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Parity and Time Reversal Invariance Test in Very Slow Neutron Reactions

极慢中子反应中的宇称和时间反转不变性测试

基本信息

批准号：
08044073
负责人：
MASAIKE Akira
金额：
$ 2.5万
依托单位：
KYOTO UNIVERSITY
依托单位国家：
日本
项目类别：
Grant-in-Aid for international Scientific Research
财政年份：
1996
资助国家：
日本
起止时间：
1996 至无数据
项目状态：
已结题

项目摘要

In order to study the origin of large enhancement of the parity violation effect in neutron resonance absorption reactions, the longitudinal asymmetries in p-wave resonances have been measured for In, Ag, Pd, Sb, Cs, Xe, Th and U targets in the energy region of 1 eV to 350 eV.We constructed a polarized proton filter for polarizing the neutron beam, and a spin flipper to reverse the diection of neutron spin. We used also liquid scintillator arrays as a neutron detector. A new computer code in which multi-level formula is used to calculate the neutron cross section has been developed.We have found 47 p-wave resonances which have large helicity asymmetries with the statistical significance greater than 3δ. The signs of the asymmetries have been found to random. The experiment shows that the large enhancement of parity violating effect is a prevalent feature of p-wave resonances. The weak spreading widths of nuclei (ΓィイD2wィエD2) have been determined from the experimental values of asymmetries . The obtained ΓィイD2wィエD2's agree with estimated value based on the statistical view.Furthermore, we have polarized protons in naphthalene crystals doped with pentacene using a dye laser at the temperature higher than 77 Kelvin. Such a polarized proton target can be used to obtain polarized neutrons.We obtained 50% polarization of La nuclei in mono-crystal of LaAloィイD23ィエD2 by means of the dynamic polarization method. The polarized La target will be of vital importance for the measurement of time reversal violation in the neutron resonance absorption.

为了研究中子共振吸收反应中宇称破坏效应大幅度增强的原因，测量了In、Ag、Pd、Sb、Cs、Xe、Th和U靶在1 eV到350 eV能区的p波共振纵向不对称性。我们制作了一个极化质子滤光器来极化中子束，并制作了一个自旋反转装置来反转中子自旋的方向。我们还使用了液体闪烁体阵列作为中子探测器。编制了一个新的计算机程序，其中使用多能级公式计算中子截面，发现了47个具有大螺旋度不对称性的p波共振，其统计意义大于3δ。不对称的迹象被发现是随机的。实验表明，宇称破坏效应的大幅增强是纵波共振的一个普遍特征。从不对称性的实验值确定了原子核(Γィイ，D2w，ィエ，D2)的弱扩散宽度。得到的ΓィイD2wィエD2‘S与基于统计观点的估计值一致。此外，在高于77开尔文的温度下，我们用染料激光在掺并五苯的萘晶体中观察到了质子的极化。用这种极化质子靶可以获得极化中子。我们用动态极化方法获得了LaAlOィイD23ィエD2单晶中La核50%的极化。极化的La靶对于测量中子共振吸收中的时间反转破坏将是至关重要的。