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The High Brilliance Neutron Source (HBS) is expected to be the next-generation neutron facility, which uses low proton energy (70MeV) to achieve high neutron brilliance. As the moderator-reflector unit is correlated to the neutron moderation, reflection, and transportation, designing a suitable moderator-reflector unit is one of the important issues for achieving the “high brilliance” of the thermal neutron cloud. In this research, the optimization of the thermal moderator-reflector of the 24Hz target station will be conducted to optimize pulse shape and intensity. The Monte Carlo simulation is applied to the design. PHITS and Diffmod are used. In this presentation, at first, the proof-of-principle simulation to reduce the absorption of hydrogenous moderator material is introduced. The time and energy characteristic of candidate material and structure are simulated and analyzed. Then, according to the neutron transportation simulation of different moderator-reflector unit, the specific design is presented. And we will show the result of thermal behavior and neutronic characteristics of this moderator-reflector unit.This work is part of the collaboration within ELENA and LENS on the development of HiCANS.

The advent of high-current accelerator systems launched the development of high -currentaccelerator-driven neutron sources (Hi-CANS) utilizing low energy nuclear reactions. Thisdevelopment can counteract the increasing shutdown of existing fission -based neutron sources and aresulting decline in available neutron beam days as well as establishing Hi-CANS as the nextgeneration of national neutron sources.A main component of a Hi-CANS is the target station used to convert protons into neutrons, tomoderate the neutrons to the required energy in the meV range, extract the neutrons to the instrumentswith the proper phase space volume as well as to shield the surrounding equipment .Within the High-Brilliance neutron Source (HBS) project, we are developing three target stationsoperated with a short pulse, medium pulse, and long pulse proton beam. The target stations have target/ moderator / reflector geometries optimized to the specific proton beam structure allowing to providetailored neutron beams to each individual neutron instrument. For this, a basic target station setup isused where just the core is modified to fulfill the specific requirements. Such a base layout of the targetstation reduces cost and effort and allows interchangeable composts making it highly modular andversatile.At UCANS 9, we will present the general design ideas of such a Hi-CANS target station and showthe flexibility it offers.

Long-wavelength neutrons for the investigation of nano-scale materials are an indispensable tool in neutronresearch. With the decommissioning of several European nuclear research reactors in recent times compactaccelerator-driven neutron sources (CANS) are of interest in providing scientists with the necessary capacityof neutrons to conduct experiments.At the High Brilliance Neutron Source (HBS) project, multiple cold moderators will be positioned inside thesame Target-Moderator-Reflector unit (TMR), each providing its own instrument with cold or even verycold neutrons. All of these moderators can therefore be optimized in terms of material, operating temperatureand geometry, depending on the requirements of the instrument.In a first approach, two cryogenic moderator systems for a prototype TMR have been designed and arecurrently being manufactured at Forschungszentrum Jülich. While one is a closed-cycle liquid parahydrogensystem, the other one allows the batch-wise production of solid moderators, e. g. frozen methane. Bothmoderators are positioned as close to the target as possible by using so-called moderator plugs (MPs). Theseconsist of a vacuum-insulated cryostat with a detachable fluid transfer and moderator section, a neutronguide and surrounding radiation shielding.The planned operation of these cryogenic moderator prototypes from summer 2022 will enable theexperimental investigation of different cold moderator geometries, as well as various options for thesurrounding thermal moderator and reflector. The obtained results can then be used to validate andcomplement nuclear simulations, proof efficient operation and will allow more reliable future designs ofsuch cold neutron sources.

Proceedings of the 13th International Particle Accelerator Conference, IPAC2022, Bangkok, Thailand 13th International Particle Accelerator Conference, IPAC2022, Bangkok, Thailand, 12 Jun 2022 - 17 Jun 2022; JACoW Publishing, Geneva, Switzerland 4 pages (2022). doi:10.18429/JACOW-IPAC2022-MOPOST016, Due to the decommissioning of several reactors, only about half of the neutrons will be available for research in Europe in the next decade despite the commissioning of the ESS. High-Current Accelerator-driven Neutron Sources (HiCANS) could fill this gap. The High Brilliance Neutron Source (HBS) currently under development at Forschungszentrum Jülich is scalable in terms of beam energy and power due to its modular design. The driver linac will accelerate a 100 mA proton beam to 70 MeV. The linac is operated with a beam duty cycle of up to 13.6 % (15.3 % RF duty cycle) and can simultaneously deliver three pulse lengths (208 µs, 833 µs and 2 ms) for three neutron target stations. In order to minimize the development effort and the technological risk, state-of-the-art technology of the MYRRHA injector is used. The HBS linac consists of a front end (ECR source, LEBT, 2.5 MeV double RFQ) and a CH-DTL section with 44 room temperature CH-cavities. All RF structures are operated at 176.1 MHz and are designed for high duty cycle. Solid-state amplifiers up to 500 kW are used as RF drivers. Due to the beam current and the high average beam power of up to 952 kW, particular attention is paid to beam dynamics. In order to minimize beam losses, a quasi-periodic lattice with constant negative phase is used. This paper describes the conceptual design and the challenges of a modern high-power and high-current proton accelerator with high reliability and availability., Published by JACoW Publishing, Geneva, Switzerland

Magnetoelectric (ME) coupling in La0.7Sr0.3MnO3/Pb(Mg1/3Nb2/3)0.7Ti0.3O3 (LSMO/PMN–PT (001)) has been probed in the past years to identify the underlying mechanism behind it. PMN–PT, which is well known for its excellent piezoelectric properties, also exhibits ferroelectricity. This motivates our interest to differentiate which effect is dominant for this 'voltage control of magnetism'. Here, we present results for the ME coupling at different temperatures: 300 K and 80 K. In this article we discuss and explain, how the nature of ME coupling is influenced by different parameters such as magnetic field, electric field, directional dependence (hard axis, easy axis) and temperature. Owing to large lattice mismatch between LSMO and PMN–PT, the strain-mediated coupling is strongly prevalent, however the change in strain behaviour from butterfly loop to linear loop is observed as a function of temperature. ME measurements are performed along hard axis [100] and easy axis [110] of LSMO in the presence of remanent magnetic field which showcases the pure influence of electric field on the system, resulting in a combination of strain- and charge-mediated coupling. The magnetic depth profile is probed by polarized neutron reflectometry as a function of electric field which demonstrates the existence of an interlayer with reduced nuclear scattering length density and reduced magnetic scattering length density at the interface. From transmission electron microscopy, stoichiometric variations are observed due to the presence of Mn3O4 particles at the interface.

Nanoscale horizons 5(7), 1065 - 1072 (2020). doi:10.1039/D0NH00117A, The self-assembly of nanoparticles into highly ordered crystals is largely influenced by variations in the size and shape of the constituent particles, with crystallization generally not observed if their polydispersity is too large. Here, we report on size selectivity in the self-assembly of rounded cubic maghemite nanoparticles into three-dimensional mesocrystals. Different X-ray scattering techniques are used to study and compare a nanoparticle dispersion that is used later for self-assembly, an ensemble of mesocrystals grown on a substrate, as well as an individual mesocrystal. The individual μm-sized mesocrystal is isolated using a focused-ion-beam-based technique and investigated by the diffraction of a micro-focused X-ray beam. Structural analysis reveals that individual mesocrystals have a drastically smaller size dispersity of nanoparticles than that in the initial dispersion, implying very strong size selectivity during self-assembly. The small size dispersity of the nanoparticles within individual mesocrystals is accompanied by a very narrow lattice parameter distribution. In contrast, the lattice parameter distribution within all mesocrystals of an ensemble is about four times wider than that of individual mesocrystals, indicating significant size fractionalization between mesocrystals during self-assembly. The small size dispersity within each mesocrystal has important implications for their physical properties., Published by Royal Society of Chemistry, Cambridge

RSC Advances 10(31), 18339 - 18347 (2020). doi:10.1039/D0RA00936A, Published by RSC Publishing, London

Proceedings of the 10th Int. Particle Accelerator Conf., IPAC2019, Melbourne, Australia 10th International Particle Accelerator Conference, IPAC2019, Melbourne, Australia, 19 May 2019 - 24 May 2019; JACoW Publishing, Geneva, Switzerland 4 pages (2019). doi:10.18429/JACOW-IPAC2019-MOPTS027, Due to the decommissioning of several research reactors there will be a severe drop in available neutrons for research in Europe in the next decade despite the commissioning of the European Spallation Source (ESS). Compact accelerator-based neutron sources (CANS) could close this gap. The High Brilliance Neutron Source (HBS) currently under development at Forschungszentrum Jülich is scalable in terms of beam energy and power due to its modular design. The driver Linac for HBS at will accelerate a 100 mA proton beam to 70 MeV. The Linac is operated with a beam duty cycle of up to 6% (11% RF duty cycle) and can simultaneously deliver three proton pulse lengths (384 Hz@52 mu-s, 96 Hz@208 mu-s and 24 Hz@832 mu-s) for three neutron production targets. In order to minimize the development effort and the technological risk, state-of-the-art technology of the MYRRHA injector is used. The front end of the HBS Linac consists of an ECR source, LEBT and a 2.5 MeV RFQ followed by a CH-DTL with 35 room temperature CH-cavities. All RF structures are operated at 176.1 MHz and are designed for high duty cycle. Solid-state amplifiers up to 500 kW are used as RF drivers. Due to the beam current and the high average beam power of up to 420 kW, particular attention is paid to beam dynamics. In order to minimize losses, a quasi-periodic lattice with constant negative phase is used. The contribution describes the conceptual design and the challenges of such a modern high power proton accelerator with high reliability and availability., Published by JACoW Publishing, Geneva, Switzerland