Defining polarised neutron beams in high-precision experiments with PERC

该项目是整个PERC项目的一部分，其目的是定义该仪器内的极化中子束，以研究中子衰变。在这种情况下，术语定义包括中子从极化器转移到衰变体，包括反转光束偏振方向的可能性。在这个过程中，为了保持假设的高极化程度，以及中子与衰变体积的解耦，以及它们在光束停止处的吸收，产生辐射背景和尽可能低的二次粒子量，并允许确定当前的中子通量和透射的极化程度。此外，该提案还包括继续发展在空间变化的磁场中通过中子自旋共振来形成极化中子脉冲的光谱和时间，现在被称为MONOPOL项目。中子束的光谱和时间结构可以用速度选择器和波束斩波器来定义——MONOPOL的替代概念，正处于初始开发阶段，可以代表一个有吸引力的实验机会，它通过解耦中子束的时间和能量分辨率，超出了标准解决方案的能力。就像PERC的测量依赖于高且定义良好的中子极化程度一样，这也是自旋谐振器的基本要求。因此，设计一种能够保持中子束从极化器进入衰变体的高极化的导流装置是至关重要的。这是特别重要的，因为极化矢量在生产和后来的衰减体积是垂直的，因此相关磁场的过渡需要得到特别的考虑。此外，PERC实验需要反转初始中子极化，为此我们将定义一个适当的宽带自旋鳍，并优化其在光束引导中的位置，其中有几个选项可用。在衰变体积的最后，中子束必须被捕获，而不会被散射的中子产生不想要的事件，也不会在随后的探测器和光谱仪中产生伽马辐射和二次粒子。同时，必须在中子飞行路径的末端测量透射中子的极化和强度，以便对这些量的实验得到的衰变数据进行归一化。第一个申请人已经在项目的第一阶段被提名为PERC的“时间和项目经理”，并代表维也纳集团在PERC磁铁系统的采购、制造、质量控制和安装过程中。

This project is part of the overall PERC project and consists of the aim to define the polarised neutron beam inside this instrument for the investigation of the neutron beta decay. The term definition comprises in this context the transfer of the neutron from the polariser into the decay volume including the possibility of inverting the orientation of the beam polarisation, and in the process to preserve the assumed high degree of polarisation as well as the decoupling of the neutrons from the decay volume and their absorption in a beam stop that produces a radiation background and an amount of secondary particles as low as possible and allows for the determination of the current neutron flux and the transmitted degree of polarisation. Additionally, this proposal includes the continuation of a development for the spectral and temporal forming of polarised neutron pulses by means of neutron spin resonance in spatially varying magnetic fields which is now referred to as the MONOPOL project. A neutron beam may be defined in its spectral and temporal structure conventionally with a velocity selector and a beam chopper – the alternative concept of MONOPOL, which is in its initial development phase, could represent an attractive addition to the experimental opportunities which exceeds the capabilities of the standard solution by decoupling the time and energy resolution for the neutron beam. Like the measurements with PERC depend on a high and well defined degree of neutron polarisation, this is also a basic requirement for the spin resonator. Therefore it is essential to design a guiding which is capable to preserve this high polarisation of the neutron beam from the polariser into the decay volume. This is particularly important since the polarisation vectors at production and later in the decay volume are perpendicular whereby the transition of the related magnetic fields needs to receive special consideration. Additionally, it is required for experiments with PERC to reverse the initial neutron polarisation for which we will define an appropriate broad-band spin flipper and optimise its position in the beam guidance where several options are available. At the end of the decay volume, the neutron beam must be caught without producing unwanted events by scattered neutrons or created gamma radiation and secondary particles in the subsequent detectors and spectrometers. At the same time the measurement of the transmitted neutron polarisation and intensity must be made possible at the end of the neutron flight path to enable normalisation of the experimentally obtained decay data on these quantities. The first applicant was nominated “Time and Project Manager” for PERC already in the first phase of the project and represents the Vienna group during procurement, manufacturing, quality control and installation of the PERC magnet system.