Advanced control and manipulation of neutron beam intensity and polarisation in precsion neutron experiments

控制入射中子能谱对几乎所有的中子实验都是必不可少的。我们提出了一种中子光学元件的发展，它不仅可以控制中子谱，但产生极化中子脉冲的几乎任意的时间结构。这个概念是基于Drabkin中子共振器与移动磁场相结合。该装置应允许仅通过电子手段几乎瞬时地改变关键仪器参数。这一发展的动机是即将到来的PERC项目，需要的入射极化中子束的时间定义和光谱控制。保偏中子导管的实验测试定义了PERC仪器中的中子衰变体积，对于其最终性能至关重要。中子共振器将能够定义脉冲PERC束的时间结构，关于数据采集和背景周期的最佳关系，这在高精度实验中特别重要。背景事件的评估和最小化是这项工作的一个重要方面。我们计划通过蒙特卡罗模拟和实验测试来开发先进的屏蔽概念，并对中子仪器产生一般影响。PERC仪器的另一个关键组成部分是磁场，它将带电中子粒子导向探测器，仪器性能将取决于其优化设计。实验将以连续和脉冲方式利用维也纳的Triga反应堆。

Controlling the incident neutron spectrum is essential for almost every neutron experiment. We propose the development of a neutron optical component which allows not only to control the neutron spectrum but to produce polarised neutron pulses of nearly arbitrary time structure. The concept is based on the Drabkin neutron resonator combined with travelling magnetic fields. This device should allow an almost instantaneous variation of key instrumental parameters by electronic means only. This development is motivated by the upcoming PERC project which requires time definition and spectral control of the incident polarised neutron beam. The experimental test of polarisation preserving neutron guides, which define the neutron decay volume in the PERC instrument, is essential for its ultimate performance. The neutron resonator will enable to define the time structure of the pulsed PERC beam with regard to optimum relation of data taking and background periods which is particularly essential in high precision experiments. Assessment and minimisation of background events is an important aspect of this work. We plan the development of advanced shielding concepts by Monte Carlo simulations and experimental tests with general impact in neutron instrumentation. Another key component of the PERC instrument is the magnetic field which guides the charged neutron particles towards the detector, and the instrument performance will rely on its optimised design. Experiments will utilise the Triga Reactor in Vienna in continuous and pulsed mode.