The Multi-Blade (MB) Boron-10-based neutron detector is the chosen technology for three instruments at the European Spallation Source (ESS): the two ESS reflectometers, ESTIA and FREIA, and the Test Beam Line. A fourth MB detector has been built, installed and commissioned for the user operation of the reflectometer Amor at PSI (Switzerland). Amor can be considered a downscaled version of the ESS reflectometer ESTIA. They are based on the same Selene guide concept, optimized for performing focusing reflectometry on small samples. The experience gained at Amor is invaluable for the future deployment of the MB detector at the ESS. This manuscript describes the MB detector construction and installation at Amor along with the readout electronics chain based on the VMM3a ASIC. The readout chain deployed at Amor is equivalent of that of the ESS, including the readout master module (RMM), event-formation-units (EFUs), Kafka, FileWriter and live visualisation tools.

The development of detectors for the European Spallation Source is an important parallel element to the effort put into the design and construction of the neutron source and instruments. The 10Boron-film-based detector developments that started over a decade ago as basic detector concepts have now reached technical maturity after intense prototyping work and numerous testing campaigns. Several of the ESS beamlines that will soon enter the commissioning phase started welcoming the detector systems built with the 10B-film converter technology. The real-size demonstrators evolved in the last 2–3 years into a diverse suite of gas proportional counters for use in diffraction, reflectometry and small-angle scattering studies in spite of the operational complexity posed by the requirements for large-area coverage, low material budget and robustness for operation in the high-flux and high-radiation environment of ESS. The detectors are now being shipped to ESS or undergoing the last performance and calibration tests before being handed over to the instrument teams for installation in the host beamlines. A common feature of these detector systems is the very large number of readout channels that they are instrumented with in order to fulfill the demanding requirements for sensitivity, spatial resolution and count-rate capability. Across all of the detector types that will operate at ESS, the integration, testing and commissioning of the read-out technologies and software tools for data reduction, calibration and analysis are the focus of the detector and integration teams. These will yield a wealth of knowledge about their operation as well as initial results on the in-situ performance, a very important asset to ensure rapid commissioning of the detectors when neutrons from the ESS source become available. In this paper we will give an overview of the 10B-film-based detector technologies included in the ESS detector suite that are currently facing the transition from the production phase to installation and integration with the other beamline components, which comes with its own specific challenges of both organizational and technical nature.

In the field of neutron scattering science, a large variety of instruments require detectors for thermal and cold neutrons. Helium-3 has been one of the main actors in thermal and cold neutron detection for many years. Nowadays, neutron facilities around the world are pushing their technologies to increase the available flux delivered at the instruments; this enables a completely new science landscape. Complementary with the increasing available flux, a better signal-to-background (S/B) ratio enables to perform new types of measurements. For instance, in neutron reflectometry, the time resolution for kinetic studies is limited by the available S/B. An improved S/B opens the possibility of sub-second kinetic studies. To this aim, this manuscript re-examines the background sensitivity of today’s “gold standard” neutron detection. Fast neutrons and gamma rays are the main background species in neutron scattering experiments. The efficiency (sensitivity) of detecting fast neutrons, cosmic rays and gamma rays, for a Helium-3-based detector is studied here through the comparison with Helium-4 counters. The comparison with Helium-4 allows to separate the thermal (and cold) neutron from the fast neutron contributions in Helium-3-based counters which are otherwise entangled, verifying previous results from an indirect method. A relatively high sensitivity is found. Moreover, an estimate for the cosmic neutron fluence, also a source of background, at ground level at ESS is presented in this manuscript.

The Multi-Blade is a Boron-10-based neutron detector designed for neutron reflectometers and developed for the two instruments (Estia and FREIA) planned for the European Spallation Source in Sweden. A demonstrator has been installed at the AMOR reflectometer at the Paul Scherrer Institut (PSI - Switzerland). AMOR exploits the Selene guide concept and can be considered a scaled-down demonstrator of Estia. The results of these tests are discussed. It will be shown how the characteristics of the Multi-Blade detector are features that allow the focusing reflectometry operation mode. Additionally the performance of the Multi-Blade, in terms of rate capability, exceeds current state-of-the-art technology. The improvements with respect to the previous prototypes are also highlighted; from background considerations to the linear and angular uniformity response of the detector.

In the field of neutron scattering science, a large variety of instruments require detectors for thermal and cold neutrons. Helium-3 has been one of the main actors in thermal and cold neutron detection for many years. Nowadays, neutron facilities around the world are pushing their technologies to increase the available flux delivered at the instruments; this enables a completely new science landscape. Complementary with the increasing available flux, a better signal-to-background (S/B) ratio enables to perform new types of measurements. For instance, in neutron reflectometry, the time resolution for kinetic studies is limited by the available S/B. An improved S/B opens the possibility of sub-second kinetic studies. To this aim, this manuscript re-examines the background sensitivity of today’s “gold standard” neutron detection. Fast neutrons and gamma rays are the main background species in neutron scattering experiments. The efficiency (sensitivity) of detecting fast neutrons, cosmic rays and gamma rays, for a Helium-3-based detector is studied here through the comparison with Helium-4 counters. The comparison with Helium-4 allows to separate the thermal (and cold) neutron from the fast neutron contributions in Helium-3-based counters which are otherwise entangled, verifying previous results from an indirect method. A relatively high sensitivity is found. Moreover, an estimate for the cosmic neutron fluence, also a source of background, at ground level at ESS is presented in this manuscript.

Neutron-based experimental techniques have been continuously improved, refined and strengthened since the pioneering experiments conducted by Clifford Shull and Bertram Brockhouse in the mid twentieth century. The possibility to reveal structure and dynamics at different scales of distances and times, provided a deep insight into the microscopic nature of condensed matter systems. The advent of scattering techniques, firmly linked to instrument development (diffractometers, spectrometers), made neutron science attractive for scientists working in different fields, such as physics, biology, chemistry and engineering. Together with the development of intense sources and sophisticated instruments, the role of neutron detection techniques is instrumental for an effective use of the intense fluxes of neutron beams that became available in the last three decades. Detectors are then essential for the development of new and effective instrumentation that in turn can trigger new ideas for science. Neutrons made available at large scale facilities extend from ultra-cold to fast neutrons. Sources providing monochromatic fast neutron beams, such as DD or DT sources (also in the form of portable devices) are used for many applications, including at industrial level. Thus, the unique properties of neutrons in terms of their interaction with matter are related to the extended range of energies or (equivalently) wavelengths over which they can be produced at both compact and/or large scales facilities. The scope of this review is, starting from the main physical mechanism for neutron detection, to provide a survey on well assessed and newly developed neutron detection systems using both passive and active methods and their applications. It will provide an overview of the current state of neutron detection by describing different approaches and pointing out open problems to be faced.

The 3He-based neutron detectors are no longer the default solution for neutron scattering applications. Both the inability of fulfilling the requirements in performance, needed for the new instruments, and the shortage of 3He, drove a series of research programs aiming to find new technologies for neutron detection. The characteristics of the new detector technologies have been extensively tested to prove their effectiveness with respect to the state-of-the-art technology.Among these, the background rejection capability is crucial to determine. The signal-to-background ratio is strongly related to the performance figure-of-merit for most instruments. These are designed to exploit the high flux expected from the new high intensity neutron sources. Therefore, an inadequate background rejection could significantly affect the measurements, leading to detector saturation and misleading events. This is of particular importance for the kind of techniques in which the signals are rather weak.For the first time, the sensitivity of 3He detectors to fast neutrons, up to En=10 MeV, has been estimated. Two independent measurements are presented: a direct calculation based on a subtraction method used to disentangle the thermal and the fast neutron contribution, while a further evidence is calculated indirectly through a comparison with the recently published data from a 10B-based detector. Both investigations give a characterization on the order of magnitude for the sensitivity. A set of simulations is presented as well in order to support and to validate the results of the measurements. A sensitivity of 4·10−3 is observed from the data. This is two orders of magnitude higher than that previously observed in 10B-based detectors.

The Multi-Blade detector has been designed to be used on the reflectometry instruments at the upcoming European Spallation Source. It is a  10B-based gaseous detector, built as a modular stack of multi-wire proportional chambers organised on a circle around the sample. The detector has been fully characterised. The gamma and fast-neutron sensitivity has been measured at the Source Testing Facility in Lund University, Sweden; the working capability in a reflectometry instrument has been demonstrated with measurements at CRISP in ISIS, UK; and the count-rate capability of the detector will be measured the summer of 2018 at the Budapest Neutron Centre, Hungary.

In the last few years many detector technologies for thermal neutron detection have been developed in order to face the shortage of He-3, which is now much less available and more expensive. Moreover the He-3-based detectors can not fulfil the requirements in performance, e.g. the spatial resolution and the counting rate capability needed for the new instruments. The Boron-10-based gaseous detectors have been proposed as a suitable choice. This and other alternative technologies are being developed at ESS. Higher intensities mean higher signals but higher background as well. The signal-to-background ratio is an important feature to study, in particular the gamma-ray and the fast neutron contributions. This paper investigates, for the first time, the fast neutrons sensitivity of B-10-based thermal neutron detector. It presents the study of the detector response as a function of energy threshold and the underlying physical mechanisms. The latter are explained with the help of theoretical considerations and simulations.

The European Spallation Source (ESS) is the world's next generation spallation-based neutron source. The research conducted at ESS will yield in the discovery and development of new materials including the fields of manufacturing, pharmaceuticals, aerospace, engines, plastics, energy, telecommunications, transportation, information technology and biotechnology. The spallation source will deliver an unprecedented neutron flux. In particular, the reflectometers selected for construction, ESTIA and FREIA, have to fulfill challenging requirements. Local incident peak rate can reach 10(5) Hz/mm(2). For new science to be addressed, the spatial resolution is aimed to be less than 1 mm with a desired scattering of 10(-4) (peak-to-tail ratio). The latter requirement is approximately two orders of magnitude better than the current state-of-the-art detectors. The main aim of this work is to quantify the cumulative contribution of various detector components to the scattering of neutrons and to prove that the respective effect is within the requirements set for the Multi-Blade detector by the ESS reflectometers. To this end, different sets of geometry and beam parameters are investigated, with primary focus on the cathode coating and the detector window thickness.

The Detector Efficiency Calculator (DECal) is a series of Python functions and tools designed to analytically calculate, visualise and optimise the detection efficiency of thermal neutron detectors, which are based on thin-film converters. The implementation presented in this article concerns 10B-based detectors in particular. The code can be run via a graphical user interface, as well as via the command line. The source code is openly available to interested users via a GitHub repository.

European Spallation Source (ESS) will deliver neutrons at high flux for use in diverse neutron scattering techniques. The neutron source facility and the scientific instruments will be located in Lund, and the Data Management and Software Centre (DMSC), in Copenhagen. A number of detector prototypes are being developed at ESS together with its European in-kind partners, for example: SoNDe, Multi-Grid, Multi-Blade and Gd-GEM. These are all position sensitive detectors but use different techniques for the detection of neutrons. Except for digitization of electronics readout, all neutron data is anticipated to be processed in software. This provides maximum flexibility and adaptability and allows deep inspection of the raw data for commissioning which will reduce the risk of starting up new detector technologies. But it also requires development of high performance software processing pipelines and optimized and scalable processing algorithms. This report provides a description of the ESS system architecture for the neutron data path. Special focus is on the interface between the detectors and DMSC which is based on UDP over Ethernet links. The report also describes the software architecture for detector data processing and the tools we have developed, which have proven very useful for efficient early experimentation, and can be run on a single laptop. Processing requirements for the SoNDe, Multi-Grid, Multi-Blade and Ge-GEM detectors are presented and compared to event processing rates archived so far.

The data refers to the measurements performed on the CRISP neutron reflectometer at ISIS with the Multi-Blade detector. The data for the direct beam and three samples: Iridium, Silicon and Fe/Si supermirror, are reported. The raw data from the read-out electronics is reduced to a matrix structure (X,Y,T,λ) which identifies a single neutron event. X and Y are the spatial coordinates of the strips and wires, respectively, in the detector. T is the time of flight of the neutron that reach the detector, while λ is the associated neutron wavelength determined by the time and geometry of the instrument. The data are collected for each digitizer, six in total, and each one corresponds to a cassette of the detector.The specular reflectivity measurement on the Iridium sample were performed tilting the sample position in step of 0.1 degree in the 0.2-0.8 degrees range.The specular reflectivity measurement on the Silicon sample were performed using both a collimated and divergent beam, at three and four angle respectively: 0.2, 0.3 and 0.8 degrees in the former configuration and 0.2, 0.3, 0.8 and 1.2 degrees in the latter configuration.The off-specular measurement on the Fe/Si supermirror sample were performed tilting the sample position in step of 0.01 degree in the 0.2-0.8 degrees range.The analyzed data for the Iridium and Silicon sample are reduced in (qz, R), where qz is the wave vector transfer and R is the reflected intensity, using the conventional analysis and the θ-corrected reduction. The latter is applied considering both the spatial resolution of the Multi-Blade detector (~0.6 mm) and the state-of-art detectors spatial resolution (~2 mm). The off-speculardata are reduced to a matrix structure (pi, pf, I, pi-pf, pi+pf) where pi and pf are the projections of the initial and final wave vectors, obtained encoding the neutron wavelengths and the incident and reflected angles and I represents the reflected intensity.The available scripts allow to reduce the initial matrix data (X,Y,T,λ) into the (qz, R) for the Iridium and Silicon sample and (pi, pf, I, pi-pf, pi+pf) for the Fe/Si sample and to plot the final results.

The Multi-Blade is a boron-10-based gaseous detector developed for neutron reflectometry instruments at the European Spallation Source in Sweden. The main challenges for neutron reflectometry detectors are the instantaneous counting rate and spatial resolution. The Multi-Blade has been tested on the CRISP reflectometer at the ISIS Neutron and Muon Source in the UK. A campaign of scientific measurements has been performed to study the Multi-Blade response in real instrumental conditions. The results of these tests are discussed in this paper.

The Multi-Blade is a Boron-10-based gaseous thermal neutron detector developed to face the challenge arising in neutron reflectometry at neutron sources. Neutron reflectometers are challenging instruments in terms of instantaneous counting rate and spatial resolution. This detector has been designed according to the requirements given by the reflectometers at the European Spallation Source (ESS) in Sweden. The Multi-Blade has been installed and tested on the CRISP reflectometer at the ISIS neutron and muon source in U.K.. The results on the detailed detector characterization are discussed in this manuscript.

The European Spallation Source (ESS), presently under construction in Lund, Sweden, is designed to be the world’s brightest neutron source. When it will be in operation, ESS will deliver an instantaneous neutron flux on detectors that will be without precedent. A down side of the high brightness will be the increase of background, especially from gamma-rays and fast-neutrons.Considering that scattering cross-sections of many samples tend to be relatively low and that the gamma- and fast-neutronbackgrounds tend to be considerable high at spallation facilities [Che +14], the signal-to-noise ratio of a measurement needs to be maximised. The sensitivity of a thermal-neutron detector to gamma-rays and to fast-neutrons is a very important characteristic, as it defines the best achievable signal-to-noise ratio for the measurement. It is therefore crucial to measure the gamma- and fast-neutron- sensitivities of all detectors that will be installed on the instruments at ESS.

The Multi-Grid detector technology has evolved from the proof-of-principle and characterisation stages. Here we report on the performance of the Multi-Grid detector, the MG.CNCS prototype, which has been installed and tested at the Cold Neutron Chopper Spectrometer, CNCS at SNS. This has allowed a side-by-side comparison to the performance of 3He detectors on an operational instrument. The demonstrator has an active area of 0.2 m2. It is specifically tailored to the specifications of CNCS. The detector was installed in June 2016 and has operated since then, collecting neutron scattering data in parallel to the He-3 detectors of CNCS. In this paper, we present a comprehensive analysis of this data, in particular on instrument energy resolution, rate capability, background and relative efficiency. Stability, gamma-ray and fast neutron sensitivity have also been investigated. The effect of scattering in the detector components has been measured and provides input to comparison for Monte Carlo simulations. All data is presented in comparison to that measured by the 3He detectors simultaneously, showing that all features recorded by one detector are also recorded by the other. The energy resolution matches closely. We find that the Multi-Grid is able to match the data collected by 3He, and see an indication of a considerable advantage in the count rate capability. Based on these results, we are confident that the Multi-Grid detector will be capable of producing high quality scientific data on chopper spectrometers utilising the unprecedented neutron flux of the ESS.

Over the last decades, the field of thermal neutron detection has overwhelmingly employed He-3-based technologies. The He-3 crisis together with the forthcoming establishment of the European Spallation Source have necessitated the development of new technologies for neutron detection. Today, several promising He-3-free candidates are under detailed study and need to be validated. This validation process is in general long and expensive. The study of detector prototypes using neutron-emitting radioactive sources is a cost-effective solution, especially for preliminary investigations. That said, neutron-emitting sources have the general disadvantage of broad, structured, emitted-neutron energy ranges. Further, the emitted neutrons often compete with unwanted backgrounds of gamma-rays, alpha-particles, and fission-fragments. By blending experimental infrastructure such as shielding to provide particle beams with neutron-detection techniques such as tagging, disadvantages may be converted into advantages. In particular, a technique known as tagging involves exploiting the mixed-field generally associated with a neutron-emitting source to determine neutron time-of-flight and thus energy on an event-by-event basis. This allows for the definition of low-cost, precision neutron beams. The Source-Testing Facility, located at Lund University in Sweden and operated by the SONNIG Group of the Division of Nuclear Physics, was developed for just such low-cost studies. Precision tagged-neutron beams derived from radioactive sources are available around-the-clock for advanced detector diagnostic studies. Neutron measurements performed at the Source Testing Facility are thus cost-effective and have a very low barrier for entry. In this paper, we present an overview of the project.

1D or 2D neutron imaging detectors with individual wire or strip readout using discriminators have the advantage of being able to treat several neutron impacts partially overlapping in time, hence reducing global dead time. A single neutron impact usually gives rise to several discriminator signals. In this paper, we introduce an information-theoretical definition of image resolution. Two point-like spots of neutron impacts with a given distance between them act as a source of information (each neutron hit belongs to one spot or the other), and the detector plus signal treatment is regarded as an imperfect communication channel that transmits this information. The maximal mutual information obtained from this channel as a function of the distance between the spots allows to define a calibration-independent measure of resolution. We then apply this measure to quantify the power of resolution of different algorithms treating these individual discriminator signals which can be implemented in firmware. The method is then applied to different detectors existing at the ILL. Center-of-gravity methods usually improve the resolution over best-wire algorithms which are the standard way of treating these signals.