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E. Jericha, H. Abele, W. Mach:
"Defining the polarised neutron beam in high-precision experiments with PERC";
Talk: 2nd Status Meeting - DFG Priority Programme 1491, Wildbad Kreuth, Germany; 11-03-2015 - 11-06-2015.

In the core of the PERC instrument the neutrons solely play a passive role. We simply wait for them to decay and to disintegrate into an electron and a proton which we meticulously take care of and an anti-neutrino which we unavoidable have to let escape. All the neutrons which do not fulfil our desire to disappear need to be eliminated appropriately before we can extract the characteristics of the charged decay products of their more complying companions. This all the more so since the electrons and protons are guided out of the neutron beam axis in a defined region of the magnet system but have to be bent back eventually, owing to the now fixed design of PERC. We will discuss the requirements for the aforementioned region with respect to absorb the neutron beam, to characterise the background produced and to allow for a determination of the beam's degree of polarisation. The formation of the polarised neutron beam which enters the decay volume of PERC is matter in its own right. This holds true for its spectral distribution, its temporal properties and its degree of polarisation. We will discuss their mutual dependencies with respect to PERC and present the beauty of spatial magnetic spin resonance in this context.