The neutron irradiation module at the European Spallation Source ESS

The neutron Irradiation Module at the European Spallation Source will make use of the high intensity fast neutron spectrum to study the behaviour of the materials used in the facility, set within the ESS research and development program for the target station. By studying how these materials are affected by radiation, estimates of the material degradation in irrradiated bespoke samples will allow to optimise of the design and lifetime of regularly replaced target components. The general design and a set of results from the neutronics calculations, aimed at estimating proton and neutron flux distributions, displacement damage, heat deposition and activation for the radiological hazard analysis of the Irradiation Module, set within the Italian contributions to the ESS construction phase, are reported. © Published under licence by IOP Publishing Ltd

The HIBEAM program: search for neutron oscillations at the ESS

With the construction of the European Spallation Source, a remarkable opportunity has emerged to conduct high sensitivity searches for neutron oscillations, including a first search for thirty years for free neutrons converting to antineutrons. Furthermore, searches can be made for transitions of neutrons and antineutrons to sterile neutron states. The HIBEAM program provides an increase in sensitivity of an order of magnitude compared to previous work. The HIBEAM program corresponds to baryon number violation by one and two units. The observation of a process satisfying a Sakharov condition addresses the open question of the origin of the matter-antimatter asymmetry in the Universe. Sterile neutron states would belong to a `dark' sector of particles which may explain dark matter. As electrically neutral, meta-stable objects that can be copiously produced and studied, neutrons represent an attractive portal to a `dark' sector. This paper describes the capability, design, infrastructure, and potential of the HIBEAM program. This includes a dedicated beamline, neutron optical system, magnetic shielding and control, and detectors for neutrons and antineutrons.Comment: 41 pages, 12 figure

Lifecycle of the ESS Moderator and Reflector System

The European Spallation Source (ESS) will be a 5 MW class spallation neutron research facility. An important part of the target station is the Moderator and Reflector (MR) System including structure and handling. The primary function of the MR Plugs is to efficiently reflect and moderate fast neutrons from the spallation target to thermal and cold neutrons suitable for the neutron scattering systems. However, the MR System need to fulfil many operational functions as well, which include cooling of radiation heat in liquid and metal bodies, positioning and structural support, capability of handling of active components and confinement, shielding and avoidance of streaming. Depending on the design, the accumulated neutron flux and irradiation induced material degradation mechanism limit the lifetime of the MR Plug. At full beam power of 5 MW, the MR Plugs need to be changed yearly. That imposes high demands on logistics, manufacturing and handling on the system. This paper presents the lifetime criteria of the MR System, in view of radiation induced material degradation. The complete MR System lifecycle is presented, which ranges from purchase of raw materials (aluminium alloy, stainless steel and beryllium), manufacturing, factory acceptance test FAT), transport, delivery control, pre-installation test until a new MR System is ready for installation

Final design, fluid dynamic and structural mechanical analysis of a liquid hydrogen Moderator for the European Spallation Source

The European Spallation Source (ESS) is currently in the construction phase and should have first beam on Target in 2019. ESS, located in Sweden, will be the most powerful spallation neutron source worldwide, with the goal to produce neutrons for research. As an in-kind partner the Forschungszentrum Juelich will among others, design and manufacture the four liquid hydrogen Moderators, which are located above and below the Target. Those vessels are confining the cold hydrogen used to reduce the energy level of the fast neutrons, produced by spallation in the Target, in order to make the neutrons usable for neutron scattering instruments. Due to the requirements [1], a fluid dynamic analysis with pressure and temperature depended hydrogen data, taking into account the pseudo critical phenomena and the pulsed neutronic heating (pressure waves) is necessary. With the fluid dynamic results, a structure mechanical analysis including radiation damage investigation (RCC-MRx code [5]), low temperature properties as well as strength reduction by welding can be realized. Finally, the manufacturing and welding completes the design process