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

控制入射中子谱对几乎每一个中子实验都是必不可少的。我们建议发展一种中子光学元件，它不仅可以控制中子谱，而且可以产生几乎任意时间结构的极化中子脉冲。这个概念是基于结合了行磁场的Drabkin中子谐振器。该装置应允许仅通过电子手段对关键仪器参数进行几乎瞬时的变化。这一发展受到即将到来的PERC项目的推动，该项目需要对入射偏振中子束进行时间定义和光谱控制。保极化中子导片的实验测试决定了PERC仪器中中子的衰变体积，对其最终性能至关重要。中子谐振器可以根据数据采集和背景周期的最佳关系来确定脉冲PERC束流的时间结构，这在高精度实验中尤为重要。评估和最小化背景事件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中子仪器中具有一般影响的实验测试来发展先进的屏蔽概念。PERC仪器的另一个关键部件是引导带电中子粒子走向探测器的磁场，仪器的性能将依赖于其优化设计。实验将利用维也纳的Triga反应堆在连续和脉冲模式下进行。

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.