We present a modular design for large-area, curved, thermal neutron detectors motivated by the requirements of the next generation of neutron-scattering instruments for efficient use of beamtime and high throughput. The base unit of the detector is a 3 He-filled, multi-wire proportional chamber (MWPC) with an individual readout of all cathodes. Mounting multiple of these MWPC segments together inside a common pressure vessel permits the creation of a single, seamless detection area offering simultaneous measurement across a wide angular range and with uniform performance and characteristics. A two-segment prototype detector was built as a proof of principle and successfully tested at the TREFF beamline at FRM II. Subsequently two nine-segment detectors have been produced for the diffractometers ERWIN at FRM II and DMC at PSI. These detectors provide 130° horizontal and 14° vertical coverage (30° and 14° for the prototype) at a sample distance of 800 mm, have position resolution of 1.6 mm in both x and y, corresponding to ~0.1°, and have an efficiency of 75% at 1.8 Å. Event positions are reconstructed from the raw cathode signals in real time by the front-end electronics with a counting rate capability of 200 kHz per segment and event timestamping with 100-ns precision. The detector at DMC has been in user mode since September 2022 and early scattering data will be presented. Finally, we will discuss a planned future development of a vertically orientated detector for the instrument STRESS-SPEC.

We present a modular readout system for the new curved 3He-detectors built for the upcoming powder diffractometer ErwiN at the Forschungs-Neutronenquelle Heinz Maier-Leibnitz (FRM II), Germany and the upgrade of the cold powder diffractometer DMC at the Paul Scherrer Institut (PSI), Switzerland. These detectors are based on multi-wire proportional chambers (MWPC) with individual readout of all cathode wires and stripes. Nine individual curved MWPC segments are mounted inside a 3He-filled common pressure vessel to form a homogenous, seamless detection area. The modular design of the detector is mirrored by the architecture of the readout electronics. This permits to adapt the readout system to similar detector types with an arbitrary number of MWPC segments. The analog Front-end consists of charge sensitive preamplifiers with 350 ns peaking time followed by comparators to deliver a Time-over-Threshold (ToT) signal. The ToT-signals are encoded and timestamped at 80 MHz by an FPGA-based board directly mounted on top of each MWPC segment. The signal processing includes a cluster recognition in x- and y-position as well as in signal arrival time. The neutron impact position is then determined using a centre-of-gravity algorithm based on the ToT-information. A further FPGA-based board gathers and post-processes data from all the segments for reconstructing neutron events occurring at the boundary of two adjacent segments. Finally, the reconstructed events are delivered to the DAQ system with 10-bit position resolution, timestamping with 100 ns precision and total charge deposit with 8-bit resolution.

Multilayer position-sensitive 10B-RPC thermal neutron detectors offer an attractive combination of sub-millimeter spatial resolution and high (>50%) detection efficiency. Here we describe a new position reconstruction method based on a statistical approach. Using experimental data, we compare the performance of this method with that of the centroid reconstruction. Both methods result in a similar image linearity/uniformity and spatial resolution. However, the statistical method allows to improve the image quality at the detector periphery, offers more flexible event filtering and allows to develop automatic quality monitoring procedures for early detection of situations when a change in the detector operation conditions starts to affect reconstruction quality.

We present experimental results on the counting rate measurements for several single-gap $^{10}$B lined resistive plate chambers ($^{10}$B-RPCs) with anodes made from standard float glass, low resistivity glass and ceramic. The measurements were performed at the V17 monochromatic neutron beamline (3.35 Ȧ) at the Helmholtz-Zentrum Berlin. For the $^{10}$B-RPCs with 0.28 mm thick float glass a maximum counting rate density of about $8\times 10^{3}$ $Hz/cm^{2}$ was obtained. In the case of low resistivity glass and ceramic, the counting rate density did not deviate from linear dependence on the neutron flux up to the maximum flux available at this beamline and exceeded a value of $3\times 10^{4}$ $Hz/cm^{2}$.

Resistive plate chambers (RPC) lined with 10B4C neutron converters is a promising cost-effective technology for position-sensitive thermal neutron detection capable to outperform 3He-based detectors in terms of spatial resolution and timing. However, as for the other types of gaseous detectors with a single layer of 10B4C at normal beam incidence, the detection efficiency to thermal neutrons of a single-gap 10B-RPC is only about 6%. Aiming to overcome this limitation, we introduce a multi-layer 10B-RPCs detector with a stack of ten double-gap hybrid RPCs. A description of the detector design and the results of its characterization performed at the TREFF neutron beamline at the FRM II neutron facility are presented. The results demonstrate that the detection efficiency exceeds 60% for neutrons with a wavelength of 4.7 Å and the spatial resolution (FWHM) is about 0.25 mm and 0.35 mm in the X and Y direction, respectively.

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 results of an experimental feasibility study of a position sensitive thermal neutron detector based on a resistive plate chamber (RPC) are presented. The detector prototype features a thin-gap (0.35 mm) hybrid RPC with an aluminium cathode and a float glass anode. The cathode is lined with a 2 mu m thick (B4C)-B-10 neutron converter enriched in B-10. A detection efficiency of 6.2% is measured at the neutron beam (lambda = 2.5 angstrom) for normal incidence. A spatial resolution better than 0.5 mm FWHM is demonstrated.

Spatial resolution of less than 200 mu m is challenging for thermal neutron detection. A novel readout scheme based on the time-projection-chamber (TPC) concept is used in a gaseous electron multiplier (GEM) detector [1]. Thermal neutrons are captured in a single 2 mu m thick Boron-10 converter cathode and secondary Helium and Lithium ions are produced with a combined energy of 2.8 MeV. These ions have sufficient energy to form straight tracks of several mm length. With a time resolving 2-dimensional readout of 400 mu m pitch in both directions, based on APV25 chips, the ions are tracked and their respective origin in the cathode converter foil is reconstructed. Using an Ar-Co-2 93:7% gas mixture, a resolution of 100 mu m (FVVHM 235 mu m) has been observed with a triple GEM-detector setup at the Garching neutron source (FRMII) for neutrons of 4.7 angstrom. (C) 2015 Elsevier B.V. All rights reserved.

A Geant4-based Python/C++ simulation and coding framework, which has been developed and used in order to aid the R&D efforts for thermal neutron detectors at neutron scattering facilities, is described. Built upon configurable geometry and generator modules, it integrates a general purpose object oriented output file format with meta-data, developed to facilitate a faster turn-around time when setting up and analysing simulations. Also discussed are the extensions to Geant4 which have been implemented in order to include the effects of low-energy phenomena such as Bragg diffraction in the polycrystalline support materials of the neutron detectors. Finally, an example application of the framework is briefly shown.

We present a novel design for a macrostructured cathode that can be coated with a thin layer of the 10B solid converter and mounted to replace the Boron-lined flat parallel plates of a proportional counter used for slow neutron detection. The proposed design consists of a 3D regular pattern exhibiting millimeter deep grooves with an opening angle of α=45°, which could be created in the substrate material by milling or forming. When a commonly used coating method like magnetron sputtering is employed to deposit the Boron-layer, due to the line-of-sight distribution of the ions, the thickness of the coating on the side of the grooves will be reduced by a factor ∼sinα/2 with respect to the thickness of the layer deposited on a flat surface normal to the ion flux. The effective neutron absorption film thickness is in this case similar for the sidewalls of the grooves and a surface at normal incidence, yielding comparable absorption efficiencies. However, the escape efficiency for the reaction products is higher for the sidewalls, owing to the thinner coating. This leads to a higher overall detection efficiency for the grooved cathode when compared to a flat cathode with the same surface area and coated with a Boron layer with roughly the same thickness. In this paper we present and discuss the GEANT4 simulations performed to optimize the geometry of the cathode, the manufacturing and coating by magnetron sputtering, as well as the proof-of-principle measurements carried out in order to assess the performance of the proposed design.

We present the results of the measurements of the detection efficiency for a 4.7 \r{A} neutron beam incident upon a detector incorporating a stack of up to five MultiWire Proportional Counters (MWPC) with Boron-coated cathodes. The cathodes were made of Aluminum and had a surface exhibiting millimeter-deep V-shaped grooves of 45°, upon which the thin Boron film was deposited by DC magnetron sputtering. The incident neutrons interacting with the converter layer deposited on the sidewalls of the grooves have a higher capture probability, owing to the larger effective absorption film thickness. This leads to a higher overall detection efficiency for the grooved cathode when compared to a cathode with a flat surface. Both the experimental results and the predictions of the GEANT4 model suggests that a 5-counter detector stack with coated grooved cathodes has the same efficiency as a 7-counter stack with flat cathodes. The reduction in the number of counters in the stack without altering the detection efficiency will prove highly beneficial for large-area position-sensitive detectors for neutron scattering applications, for which the cost-effective manufacturing of the detector and associated readout electronics is an important objective. The proposed detector concept could be a technological option for one of the new chopper spectrometers and other instruments planned to be built at the future European Spallation Source in Sweden. These results with macrostructured cathodes generally apply not just to MWPCs but to other gaseous detectors as well.

The software package ANTS (Anger-camera type Neutron detector: Toolkit for Simulations), developed for simulation of Anger-type gaseous detectors for thermal neutron imaging was extended to include a module for experimental data processing. Data recorded with a sensor array containing up to 100 photomultiplier tubes (PMT) or silicon photomultipliers (SiPM) in a custom configuration can be loaded and the positions and energies of the events can be reconstructed using the Center-of-Gravity, Maximum Likelihood or Least Squares algorithm. A particular strength of the new module is the ability to reconstruct the light response functions and relative gains of the photomultipliers from flood field illumination data using adaptive algorithms. The performance of the module is demonstrated with simulated data generated in ANTS and experimental data recorded with a 19 PMT neutron detector. The package executables are publicly available at http://coimbra.lip.pt/~andrei/

A 2D position sensitive gas scintillation detector for thermal neutrons is under development as part of the European FP7 NMI3 JRA program (Project 226507). The aim of the project is to have a detector with: sub-millimetre position resolution, high rate capability (>1 MHz), high efficiency (>50% for 1 Angstrom neutrons) and an active area of 200×200 mm2. A detector with these characteristics is of interest for retlectometry and micro-focusing SANS instruments at the neutron scattering facilities. The detector under development is a gas scintillation proportional counter (GSPC) that uses the light emitted in the gas avalanche to determine the position of neutrons absorbed inside the detector using the Anger camera principle. The device for the gas multiplication is an MSGC and the gas is a mixture of 3He and CF4, Despite the worldwide shortage of 3He, it still represents a valid option for small detectors that require high efficiency like the one under development in this project. The status of the project will be reported in the following sections.

A custom and fully interactive simulation package ANTS (Anger-camera type Neutron detector: Toolkit for Simulations) has been developed to optimize the design and operation conditions of secondary scintillation Anger-camera type gaseous detectors for thermal neutron imaging. The simulation code accounts for all physical processes related to the neutron capture, energy deposition pattern, drift of electrons of the primary ionization and secondary scintillation. The photons are traced considering the wavelength-resolved refraction and transmission of the output window. Photo-detection accounts for the wavelength-resolved quantum efficiency, angular response, area sensitivity, gain and single-photoelectron spectra of the photomultipliers (PMTs). The package allows for several geometrical shapes of the PMT photocathode (round, hexagonal and square) and offers a flexible PMT array configuration: up to 100 PMTs in a custom arrangement with the square or hexagonal packing. Several read-out patterns of the PMT array are implemented. Reconstruction of the neutron capture position (projection on the plane of the light emission) is performed using the center of gravity, maximum likelihood or weighted least squares algorithm. Simulation results reproduce well the preliminary results obtained with a small-scale detector prototype. ANTS executables can be downloaded from http://coimbra.lip.pt/∼andrei/.

A gas scintillation Anger camera for thermal neutron imaging is being developed in the frame of the NMI3 FP7 Project 226507 collaboration. The detection medium is a high pressure gas mixture of 3 He and CF 4 . An array of photomultiplier tubes (PMTs) registers photons of the CF 4 the PMTs. Several secondary scintillation generated in the electron avalanches at the MSGC (MicroStrip Gas Chamber) plate. The detector is expected to have sub-millimeter spatial resolution, high counting rate (up to 1 MHz) and good (>50%) detection efficiency. A custom and fully interactive Monte Carlo simulation package (ANTS: Anger camera Neutron detector Toolkit for Simulations) was developed to optimize the design of the detector in order to reach the highest possible spatial resolution. The simulation code accounts for all relevant physical processes in the gas: neutron capture, energy deposition, electron drift, electron multiplication and secondary scintillation. Individual photons are tracked through the gas and the output window (wavelength-resolved refraction and transmission are implemented). Photo-detection accounts for the angular response, active area non-uniformity, gain and single-photon spectra of the PMTs. Several PMT read-out patterns and localization algorithms are implemented in the package. The results of simulations reproduce well the preliminary results obtained with small-scale detector prototypes.

HADES is a versatile magnetic spectrometer aimed at studying dielectron production in pion, proton and heavy-ion-induced collisions. Its main features include a ring imaging gas Cherenkov detector for electron-hadron discrimination, a tracking system consisting of a set of 6 superconducting coils producing a toroidal field and drift chambers and a multiplicity and electron trigger array for additional electron-hadron discrimination and event characterization. A two-stage trigger system enhances events containing electrons. The physics program is focused on the investigation of hadron properties in nuclei and in the hot and dense hadronic matter. The detector system is characterized by an 85% azimuthal coverage over a polar angle interval from 18° to 85° , a single electron efficiency of 50% and a vector meson mass resolution of 2.5%. Identification of pions, kaons and protons is achieved combining time-of-flight and energy loss measurements over a large momentum range ( 0.1 < p < 1.0 GeV/c . This paper describes the main features and the performance of the detector system.

HADES is a versatile magnetic spectrometer aimed at studying dielectron production in pion, proton and heavy-ion induced collisions. Its main features include a ring imaging gas Cherenkov detector for electron-hadron discrimination, a tracking system consisting of a set of 6 superconducting coils producing a toroidal field and drift chambers and a multiplicity and electron trigger array for additional electron-hadron discrimination and event characterization. A two-stage trigger system enhances events containing electrons. The physics program is focused on the investigation of hadron properties in nuclei and in the hot and dense hadronic matter. The detector system is characterized by an 85 % azimuthal coverage over a polar angle interval from 18 to 85, a single electron efficiency of 50 % and a vector meson mass resolution of 2.5 %. Identification of pions, kaons and protons is achieved combining time-of-flight and energy loss measurements over a large momentum range. This paper describes the main features and the performance of the detector system.

HADES is a versatile magnetic spectrometer aimed at studying dielectron production in pion, proton and heavy-ion–induced collisions. Its main features include a ring imaging gas Cherenkov detector for electron-hadron discrimination, a tracking system consisting of a set of 6 superconducting coils producing a toroidal field and drift chambers and a multiplicity and electron trigger array for additional electron-hadron discrimination and event characterization. A two-stage trigger system enhances events containing electrons. The physics program is focused on the investigation of hadron properties in nuclei and in the hot and dense hadronic matter. The detector system is characterized by an 85% azimuthal coverage over a polar angle interval from 18◦ to 85◦, a single electron efficiency of 50% and a vector meson mass resolution of 2.5%. Identification of pions, kaons and protons is achieved combining time-of-flight and energy loss measurements over a large momentum range (0.1 < p < 1.0 GeV/c). This paper describes the main features and the performance of the detector system. PACS. 21.65.Jk Mesons in nuclear matter – 25.75.Cj Photon, lepton, and heavy quark production in relativistic heavy ion collisions – 29.30.-h Spectrometers and spectroscopic techniques – 29.85.Ca Data acquisition and sorting The HADES Collaboration (G. Agakishiev et al.): The high-acceptance dielectron spectrometer HADES 245

A multi-filter was installed at the ANTARES facility at FRM II. It consists of four crystal filters single crystal sapphire and bismuth; and polycrystalline bismuth and beryllium, which are embedded in a selector wheel for quick exchange. Each of the four filters can be combined with a lead filter, which is mounted separately. By TOF measurement, the effect of the different filters on the neutron spectrum at the ANTARES facility was investigated. The results of these measurements directly lead to first applications for non-destructive testing.