The Beamline for European Materials Engineering Research (BEER) is under construction at the European Spallation Source (ESS) in Lund, Sweden. A basic requirement on BEER is to make best use of the long ESS pulse (2.86 ms) for engineering investigations. High-resolution diffraction, however, demands timing resolution up to 0.1% corresponding to a pulse length down to about 70 μs for the case of thermal neutrons (λ ∼ 1.8 Å). Such timing resolution can be achieved by pulse shaping techniques cutting a short section out of the long pulse, and thus paying for resolution by strong loss of intensity. In contrast to this, BEER proposes a novel operation mode called pulse modulation technique based on a new chopper design, which extracts several short pulses out of the long ESS pulse, and hence leads to a remarkable gain of intensity compared to nowadays existing conventional pulse shaping techniques. The potential of the new technique can be used with full advantage for investigating strains and textures of highly symmetric materials. Due to its instrument design and the high brilliance of the ESS pulse, BEER is expected to become the European flagship for engineering research for strain mapping and texture analysis.

The Beamline for European Materials Engineering Research (BEER) will be built at the European Spallation Source (ESS). The diffractometer utilizes the high brilliance of the long- pulse neutron source and offers high instrument flexibility. It includes a novel chopper technique that extracts several short pulses out of the long pulse, leading to substantial intensity gain of up to an order of magnitude compared to pulse shaping methods for materials with high crystal symmetry. This intensity gain is achieved without compromising resolution. Materials of lower crystal symmetry or multi-phase materials will be investigated by additional pulse shaping methods. The different chopper set- ups and advanced beam extracting techniques offer an extremely broad intensity/ resolution range. Furthermore, BEER offers an option of simultaneous SANS or imaging measurements without compromising diffraction investigations. This flexibility opens up new possibilities for in-situ experiments studying materials processing and performance under operation conditions. To fulfil this task, advanced sample environments, dedicated to thermo- mechanical processing, are foreseen.

Process for the production of converters neutrons, in which a transparent to neutrons aluminum or aluminum alloy metal substrate is polished by fine sanding in a first step and, in a second step, is coated with boron carbide by sputtering.

Due to the present shortage of 3He and the associated tremendous increase of its price, the supply of large neutron detection systems with 3He becomes unaffordable. Alternative neutron detection concepts, therefore, have been invented based on solid 10B converters. These concepts require development in thin film deposition technique regarding high adhesion, thickness uniformity and chemical purity of the converter coating on large area substrates. We report on the sputter deposition of highly uniform large-area 10B4C coatings of up to 2 μm thickness with a thickness deviation below 4% using the Helmholtz-Zentrum Geesthacht large area sputtering system. The 10B4C coatings are x-ray amorphous and highly adhesive to the substrate. Material analysis by means of X-ray-Photoelectron Spectroscopy, Secondary-Ion-Mass-Spectrometry, and Rutherford-Back-Scattering (RBS) revealed low impurities concentration in the coatings. The isotope composition determined by Secondary-Ion-Mass-Spectrometry, RBS, and inelastic nuclear reaction analysis of the converter coatings evidences almost identical 10B isotope contents in the sputter target and in the deposited coating. Neutron conversion and detection test measurements with variable irradiation geometry of the converter coating demonstrate an average relative quantum efficiency ranging from 65% to 90% for cold neutrons as compared to a black 3He-monitor. Thus, these converter coatings contribute to the development of 3He-free prototype detectors based on neutron grazing incidence. Transferring the developed coating process to an industrial scale sputtering system can make alternative 3He-free converter elements available for large area neutron detection systems.

Status: 29 September 2014

The development of new large area and high flux thermal neutron detectors for future neutron spallation sources, like the European Spallation Source (ESS) is motivated by the problem of 3He shortage. In the framework of the development of ESS, GEM (Gas Electron Multiplier) is one of the detector technologies that are being explored as thermal neutron sensors. A first prototype of GEM-based thermal neutron beam monitor (bGEM) has been built during 2012. The bGEM is a triple GEM gaseous detector equipped with an aluminum cathode coated by 1μm thick B4C layer used to convert thermal neutrons to charged particles through the 10B(n,7Li)α nuclear reaction. This paper describes the results obtained by testing a bGEM detector at the ISIS spallation source on the VESUVIO beamline. Beam profiles (FWHMx=31mm and FWHMy=36mm), bGEM thermal neutron counting efficiency (≈1%), detector stability (3.45%) and the time-of-flight spectrum of the beam were successfully measured. This prototype represents the first step towards the development of thermal neutrons detectors with efficiency larger than 50% as alternatives to 3He-based gaseous detectors.

The depth-dependent morphology of the microphase separation structure in thin block copolymer films is examined using non-destructive time-of-flight grazing-incidence small-angle neutron scattering. The structure of a cylinder-forming diblock copolymer, polystyrene(deuterated)- block -polyisoprene, in contact with either a low- or a high-energy substrate surface is investigated. A systematic identification of the components of the polymer film at different depths is achieved by utilizing the material characteristic Yoneda peak. For the polymer film attached to the low-surface-energy aminosilane-coated substrate, a morphology transition from lamellar at the substrate–polymer interface, via perforated lamellar in the film bulk, to an ill-defined structure at the polymer–air interface is observed. This phase transition along the film normal is due to the competition between the surface-induced morphological changes and the stable cylindrical bulk morphology of the diblock copolymer. In contrast, on the high-energy surface no pronounced ordering is found for the applied conditions.

The structure of porous TiO2 films and TiO2:poly(N-vinylcarbazole) (PVK) composite films is investigated with time-of-flight grazing incidence small-angle neutron scattering (TOF-GISANS). The TiO2 films have been prepared by application of a sol-gel process with a diblock copolymer as structure directing agent, and the conductive polymer PVK is infiltrated in the porous network by spin coating and solution casting. The films show a hierarchical pore structure with mesopores 52 nm in size and additional large macropores with a diameter of about 180 nm. By matching the scattering contrast of the TiO2 with the polymer information about the penetration of the polymer in the pores is determined. Whereas in the PVK film prepared by solution casting the pores are filled to a high degree; in the spin coated film, PVK wets only the TiO2 pore walls and forms a solid overlying layer. (C) 2010 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 48: 1628-1635,2010

A Gd nanowire grating with a periodicity of approximately 225 nm prepared on a faceted \(\alpha\hbox{-}{\rm Al}_2{\rm O}_3\) substrate was investigated by Time-Of-Flight Grazing Incidence Small Angle Neutron Scattering. These measurements allowed to obtain information on the critical wavelength, the reflected and transmitted intensities and also allowed a reconstruction of large portions of the grating truncation rods in reciprocal space. Results were obtained for various orientations around the sample normal and compared with a theoretical model, showing good agreement.

Grazing incidence small angle neutron scattering (GISANS) overcomes the limitations of conventional small angle scattering with respect to extremely small sample volumes in the thin film geometry. In time of flight (TOF) mode neutrons with a broad range of wavelengths are used simultaneously and recorded as a function of their respective times of flight. The combination of both, TOFGISANS, enables the simultaneous performance of several GISANS measurements, which differ in wavelength. As a consequence, within one measurement a full set of GISANS pattern related to different scattering vectors, different scattering depths and resolutions result. This allows the detection of nanostructures with a chemical sensitivity. The possibilities of TOF-GISANS are demonstrated by the simple example of polymer nano-dots located on top of a silicon surface. As probed with atomic force microscopy (AFM) the nano-dots exhibit a large characteristic nearest neighbour distance of 545 nm and a surface coverage of 28%. From the analysis of the wavelength dependent data in combination with AFM the mass density of the polymer nano-dots is determined to be equal to the bulk value. A comparison to common single wavelength GISANS experiments is shown.

As is well known the Larmor precession of the neutron polarization passing through a range of homogeneous magnetic field can efficiently be used for perfectly harmonic modulation of incoming (or scattered) intensity as a function of neutron wavelength. We show that the Fourier analysis of a few reflection curves obtained at a proper set of Larmor frequencies allows to numerically reconstruct the genuine reflectivity curve in great details even in the case it has been measured with a rather purely monochromatized beam. It is argued that the method can be used to substantially improve wave length resolution with moderate increase in measuring time. Further applications of the method, e.g. to small angle scattering at grazing incidence (GISANS), are briefly discussed.

The horizontal reflectometer REFSANS at FRM-2 in Munich/Germany has successfully been put into operation. It is dedicated to the comprehensive analysis of the air/water interface by means of specular and off-specular reflectivity as well as GISANS measurements [1,2]. In parts, novel components concerning the chopper system, the neutron optics, the detector and the data acquisition system have been developed to meet the requirements of the basic demands on REFSANS. An overview of the status of REFSANS as achieved in 2005 is presented.

Parallax error severely limits the use of gas detectors for neutron and X-ray single-crystal diffractometry. This is particularly the case in Neutron Macromolecule Crystallography (NMC), where a large solid angle is needed. High-resolution cylindrical detectors based on Neutron Image Plates provide a large angular coverage but they are gamma sensitive and do not allow time-resolved measurements. We describe the principle of a gas counter, the multi-blade Microstrip Gas Chamber (MSGC), which has the potential to design parallax-free cylindrical detectors. It contains radial MSGC plates, providing a partitioning of the gas volume and a segmentation of the signal readout. The axial coordinate is measured by reading out the charge signal on the anodes and the trans-axial coordinate is deduced from the electron drift distance measured optically using the time difference between the primary and the avalanche light. Expected characteristics are a sub-millimeter position resolution, a sub-microsecond time resolution, and a global counting rate greater than 107s-1.

A multi-wire proportional counter with delay line readout, a sensitive area of 500×500 mm2 and a spatial resolution of ∼2×2 mm2 is being developed for the reflectometer REFSANS at the new reactor FRM-II in Munich in Germany. The characterization of a prototype of this detector with γ-rays and neutrons is presented.

The reflectometer REFSANS being built at the high flux reactor FRM-II in Munich is dedicated to the analysis of surfaces, interfaces and phase boundaries at the air–water interface of liquid/soft matter. Novel time-of-flight design and neutron optics have been developed to make it a most flexible device for the comprehensive analysis of samples with horizontally aligned surfaces. The potential of REFSANS for measuring low reflectivity and off-specular scattering is outlined.