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Neutron scattering experiments at three-axes spectrometers (TAS) investigate magnetic and lattice excitations by measuring intensity distributions to understand the origins of materials properties. The high demand and limited availability of beam time for TAS experiments however raise the natural question whether we can improve their efficiency and make better use of the experimenter's time. In fact, there are a number of scientific problems that require searching for signals, which may be time consuming and inefficient if done manually due to measurements in uninformative regions. Here, we describe a probabilistic active learning approach that not only runs autonomously, i.e., without human interference, but can also directly provide locations for informative measurements in a mathematically sound and methodologically robust way by exploiting log-Gaussian processes. Ultimately, the resulting benefits can be demonstrated on a real TAS experiment and a benchmark including numerous different excitations., Main: 24 pages, 6 figures, 1 table | Supplementary Information: 19 pages, 12 figures, 1 table

BornAgain is a free and open-source multi-platform software framework for simulating and fitting X-ray and neutron reflectometry, off-specular scattering, and grazing-incidence small-angle scattering (GISAS). This paper concentrates on GISAS., BornAgain is a free and open-source multi-platform software framework for simulating and fitting X-ray and neutron reflectometry, off-specular scattering, and grazing-incidence small-angle scattering (GISAS). This paper concentrates on GISAS. Support for reflectometry and off-specular scattering has been added more recently, is still under intense development and will be described in a later publication. BornAgain supports neutron polarization and magnetic scattering. Users can define sample and instrument models through Python scripting. A large subset of the functionality is also available through a graphical user interface. This paper describes the software in terms of the realized non-functional and functional requirements. The web site https://www.bornagainproject.org/ provides further documentation.

This paper reports on the formation of large area, self assembled, highly ordered monolayers of stearyl alcohol grafted silica nanospheres of ≈50 nm diameter on a silicon substrate based on the drop-casting method. Our novel approach to achieve improved order uses stearyl alcohol as an assistant by adding it to the colloidal NanoParticle (NP) dispersion from which the monolayers are formed. Additionally, a heat treatment step is added, to melt the stearyl alcohol in the monolayer and thereby give the particles more time to further self-assemble, leading to additional improvement in the monolayer quality. The formation of the monolayers is significantly affected by the concentration of the NPs and the stearyl alcohol, the volume of the drop as well as the time of the heat treatment. A high surface coverage and uniform monolayer film of SiO

The structure and dynamic properties of poly(N-isopropylacrylamide) brushes at solid planar surfaces under good solvent conditions are studied. Polymer brushes with grafting densities in the concentrated and semidilute regime are prepared via surface-initiated atom transfer radical polymerization. The polymer brushes were removed from the substrates to determine the molar mass and molecular dispersity via size-exclusion chromatography to draw conclusions about the grafting density. The structure of the brushes was investigated with ellipsometry and neutron reflectometry measurements. We found an influence of the grafting density on the swelling properties of the poly(N-isopropylacrylamide) brushes. Furthermore, the brush dynamics at different neutron penetration depths was analyzed with neutron spin echo spectroscopy under grazing incidence. The evanescent intensity distribution was modeled with the BornAgain software package, which uses the distorted-wave Born approximation.

Absrtract Adsorbed ethylene glycol based microgel particles on a silicon surface were studied. Neutron reflectometry (NR) and grazing incidence small-angle neutron scattering (GISANS) were performed to investigate their internal structure. Scattering experiments on soft matter systems such as adsorbed microgels often give only partial information about the inner structure of the polymer system. In this contribution, we discuss how the detailed inner structure of adsorbed microgel particles can be reconstructed by a combination of the specular Neutron Reflectivity (NR), Grazing Incidence Small Angle Neutron Scattering (GISANS), Atomic Force Microscopy (AFM) and a simulation in the framework of the Distorted Wave Born Approximation.

The example of a gas flowing through an orifice into the surrounding rarefied space is used to demonstrate the possibility of using clusters for diagnosing gas flows. For the conditions studied (it takes a cluster velocity about the same time to relax to the gas velocity as it does to reach the orifice), information on the flow parameters inside the chamber is obtained from the measurement of the cluster drift velocity after the passage through an orifice for various gas consumptions. Other possible uses of clusters in gas flow diagnostics are discussed as well.

The structure and dynamics of nanostructure films formed by mixtures of soy phosphatidylcholine and glycerol dioleate at the silicon–aqueous interface were studied by grazing incidence neutron spin echo spectroscopy (GINSES), specular and off-specular neutron reflectometry, and small-angle X-ray diffraction. Reverse hexagonal (HII) and micellar cubic phase (Fd3m) layers at the solid–liquid interface have been identified with neutron reflectometry measurements. A preferred orientation of the liquid crystalline (LC) domains was observed only for the anisotropic HII phase. The size of the LC domains was found to be about 1 micrometer as estimated from the width of the diffraction peaks. GINSES revealed that the cubic phase forms rather rigid films. In comparison, the HII film was more flexible, appearing as a modified undulation spectrum of the cylinders due to the interaction with the substrate.

The present work analyzes the cluster relaxation in the gas beam for clusters formed in a gas aggregation nanocluster sources in the framework of the small transition region model. The model applied provides plausible values for cluster velocities which are in a good agreement with measured ones and in the fair agreement with simulated by other researchers. The effect of separation of clusters of different masses in the beam due to dependence of their transversal velocity on the cluster mass is also studied.

The temperature effect of the muon cosmic ray (CR) component is studied using the MUSTANG super telescope data (Greifswald, Germany) from 2007 throughout its period of operation. The original hourly data obtained with the telescope are adjusted for the temperature effect using a vertical atmospheric temperature profile at standard isobaric levels derived from the Global Forecast System (GFS) model. The model’s accuracy and applicability is evaluated using atmospheric sounding data collected over a number of years.

The present paper reports on target erosion as one of the crucial parameters influencing the cluster size distribution. Size distributions of nanosized Cu clusters produced by a DC magnetron sputtering source during the lifetime of several different targets were monitored using a quadrupole mass filter. It is indicated that, during the target lifetime, cluster size distribution continuously shifts towards larger cluster sizes and becomes broader. After a certain operation time the cluster size distribution changes abruptly and the cluster formation is stopped. This happens much earlier than the point at which the erosion groove depth reaches the target thickness. It is suggested that a change in the mass spectra during the target lifetime is caused by the variation of the free metal atom density in the aggregation region. This may be due to the alteration of the sputtering yield. It is shown that the variation of the mass spectra correlates with the angular dependence of the sputtering yield.

A comparison of quadrupole mass spectrometric (QMS) and transmission electron microscopic (TEM) characterization of silver nano-cluster deposition produced by a nano-cluster source consisting of a planar DC magnetron sputter source in a high pressure gas aggregation chamber is presented and discussed. Cluster sizes and size distributions detected by the two different techniques are compared and the differences are discussed. The effects of He to Ar ratio, gas flow and magnetron power on the cluster size distribution are evaluated. The influence of the target erosion and aging effects are mentioned, too (© 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

We report the investigation of morphology and composition of copper nanocluster films deposited on Si substrates. The nanoclusters are formed in an aggregation tube at room temperature and magnetron sputtering source is used to get negatively charged Cu-clusters' beam which is subsequently mass-filtered to get size-selected cluster on the substrates as soft-landing process of deposition. For composition of the films, X-ray photoelectron spectroscopy (XPS) technique is used. For morphological changes of the films both scanning electron microscopy (SEM) and atomic force microscopy (AFM) analyses are carried out. Additionally, Energy Dispersive X-ray (EDX) spectra support the compositional and structural informations of the film. The analysis of Cu nanoclusters' films reveals that initial nucleation of Cu clusters takes place in the form of isolated islands and the arrival of subsequent Cu clusters onto Si substrates has preferential aggregation around the preceding clusters forming a mound structure.

The atmospheric effect correction of the muon flux measured by ground level telescopes is of special importance for further study of cosmic ray variations. The Duperier method is used to correct atmospheric effects on the muon intensity observed by the MuSTAnG telescope. Linear multiple correlation and regression analysis are applied to the data registered during the year 2009. The aerological data are obtained from daily radiosonde balloon flights of Deutscher Wetterdienst. The regression coefficients and total correlation coefficients are calculated for all directional channels. The seasonal variations are eliminated from the MuSTAnG telescope data. The results are compared with theoretical elimination of temperature variations.

The paper reports on an experimental investigation of the ion velocity distribution function (IVDF) for mass-selected copper cluster ions with a diameter in the range 5–10 nm. The cluster ion beam is produced by a dc magnetron-based gas aggregation source. The measurements are carried out by means of a quadrupole mass filter combined with a basic retarding field analyser. The most probable cluster velocities are in the range 80–180 m s−1; decreasing with cluster size and increasing with buffer gas (Ar) flow. Experimental results are compared with the theoretical model of Smirnov et al. Noted discrepancies are explained by the interaction of clusters with buffer gas atoms outside the aggregation chamber during the passage from the orifice towards the detector. This interaction is not included in the theoretical model. Both positively and negatively charged clusters are investigated. The density ratio of positively to negatively charged clusters in the beam is evaluated from the measured IVDFs and compared with the theoretical model.

A research of the temperature effect of the muon cosmic ray (CR) component on the MuSTAnG super telescope data (Greifswald, Germany) for the whole period of its work (from 2007) was carried out. The primary hourly telescope's data were corrected for the temperature effect, using vertical temperature atmospheric profile at the standard isobaric levels obtained from the GFS model. To estimate the model accuracy and applicability the air sounding data for some years were used.

We investigate directional sensitivity of MuSTAnG muon telescope by deriving the distribution of secondary muons, which create the counting rate of telescope, by asymptotic directions of primary protons. This distribution, defined as “directivity function”, allows us to clarify protons appearing from which direction essentially contribute to counting rate of detector. Directivity function has different behavior for the muons falling on the telescope at different zenith and polar angles. Vertical, West, and East fluxes exhibit strong maximums near the asymptotic longitude about 61°, whereas North and South fluxes have larger spread distributions. About 65% of muons, which create the Vertical counting rate of MuSTAnG, are produced by the primary protons, coming in the interval of asymptotic longitudes about (50°, 80°). Using directivity function will allow one to more correctly determine the location of interplanetary disturbances. Analogous analysis, made for other muon detectors, will clarify their directional sensitivities, improving by this the forecasting capability of network of ground-based muon detectors.

A simple and cost effective nanocluster ion source for the deposition of size selected metal nanocluster has been developed based on the dc magnetron discharge (including pulsed dc discharge). The most important and interesting feature of this cluster source is that it is working at room temperature, cooled by chilled water during the experiment. There is no extraction unit in this device and the cluster streams flow only due to the pressure gradient from source chamber to substrate via quadrupole mass filter. It has provision of multiple substrate holders in the deposition chamber, which can be controlled manually. The facility consists of quadrupole mass filter (QMF 200), which can select masses in the range of 2-125 000 atoms depending on the target materials, with a constant mass resolution (M/DeltaM approximately 25). The dc magnetron discharge at a power of about 130 W with Ar as feed/buffer gas was used to produce the Cu nanocluster in an aggregation tube and deposited on Si (100) wafer temperature.