Development and status of protection functions for the normal conducting LINAC at ESS

The European Spallation Source faces a great challenge in succeeding with its ambitious availability goals. The aim is to construct a machine that allows for 95% availability for neutron beam production. This goal requires a robust protection system that allows for high availability by continuously monitoring and acting on the machine states, in order to avoid long facility downtimes and optimize the operation at any stage. The normal conducting section consists of the first 48 meters of the machine, and performs the initial acceleration, bunching, steering, and focusing of the beam, which sets it up for optimal transition into the superconducting section. Through a fit-for-purpose risk management process, a set of protection functions has been identified. The risk identification, analysis, and treatment were done in compliance with modern safety and ISO standards. This ensures that the risks, in this case downtime and equipment damage, are properly prevented and mitigated. This paper describes this process of defining the protection functions for the normal conducting LINAC at ESS

Measuring the Michel parameter xi'' in polarized muon decay

International audienceThe study of pure leptonic electroweak processes, such as muon decay, is appropriate to test the Standard Model of the electroweak interactions as well as some of its extensions since the radiative corrections are negligible (and understood) at this level of precision. Unlike most of the Michel parameters used to describe muon decay, the uncertainty on the experimental value of xi[double-prime] that fits the Standard Model V-A interaction, is large (xi[double-prime]=0.65±0.36) [1]. In order to improve the accuracy of this value, we have measured the longitudinal polarization, PL, of positrons emitted in the decay of polarized muons as a function of the positron energy. In fact, the value of PL, at the positron endpoint energy equal to unity in the Standard Model, decreases for high energy positrons emitted antiparallel to the muon spin if the combination of Michel parameters xi[double-prime]/xixi[prime]-1 deviates from the Standard Model value, i.e. from zero. We plan to improve the precision on xi[double-prime] to 0.5%. Preliminary results are described

A precision measurement of the Michel parameter xi'' in polarized muon decay

The present form of the Standard Model (SM) describes weak process in terms of vector and axial-vector type interaction, with fully left-handed massless neutrons. Any experimental deviation from the SM predictions will in special cases reveal the need for extensions to the SM. The longitudinal polarization of the positron emitted from polarized muon present a simple and sensitive case. We present hereafter the status of a longitudinal polarization measurement of these positrons