Search

The MoEDAL (the monopole and exotics detector at the LHC) experiment is located at the interaction point 8 (IP8) of the large hadron collider (LHC). It is an experiment that is dedicated to searches for exotic particles, such as magnetic monopoles and dyons. The experiment is being upgraded with scintillator detectors called as the MAPP (MoEDAL apparatus for penetrating particles). They will extend the physics reach of the experiment by providing sensitivity to millicharged and long-lived exotic particles. The MAPP detectors are planned to be installed, or are already installed in various adjacent tunnels at about 50 to 100 meters from the IP8. To study the physics reach and to support the data analysis of the detectors, we developed a detailed simulation model with Geant4. The model consists of all tunnels, accelerator components between the detectors and the IP8, and of about 100 meters thick ground layer above the tunnels for cosmic ray background studies. In addition to geometry, new physics models that describe the interactions of exotic particles, such as millicharged particles, are implemented into the model. [ABSTRACT FROM AUTHOR]

The Jagiellonian - Positron Emission Tomograph (J-PET) is a multi purpose detector for tests of discrete symmetries and quantum entanglement of photons originating from the decay of positronium atoms. The research is per formed by measurement of angular correlations between photons from the an nihilations of the lightest leptonic bound system. The J-PET detector is the only device which enables determination of polarisation of photons from positronium annihilation together with estimation of positronium spin axis on the event-by-event basis. The novelty of the system is based on a usage of plastic scintil-lators as active detection material and trigger-less data acquisition system. The aim of two independent detection setups currently in use together with different annihilation chambers is to improve limits on C, CP and CPT symmetries and to search for the entanglement of photons originating from electron-positron annihilation. Additionally a precise measurement of ortho-positronium life time would allow to test of non-relativistic quantum electrodynamics and search for Mirror Matter. [ABSTRACT FROM AUTHOR]

Light kaonic atoms spectroscopy provides a unique approach to study the low-energy strong interaction in the strangeness sector. Precise measurements of X-ray emission from light kaonic atoms provide valuable information on kaon-nucleus interaction at threshold without the need for extrapolation as required in scattering experiments. The SIDDHARTA-2 experiment at the DAΦNE collider of INFN-LNF is now poised to perform the challenging measurements of the K−- d 2p → 1s transition to extract the isospin-dependent antikaonnucleon scattering lengths. To achieve this goal, the background reduction is a crucial factor. This paper provides an overview of the SIDDHARTA-2 Veto-1 system, which uses scintillators outside the vacuum chamber to detect charged particles produced by K− absorption by the nucleus. The arrival time of these particles is correlated with the position where the kaonic atom has been created inside the setup, allowing for the rejection of kaons stopped outside the target cell, which is a critical component for reducing the background and improve the accuracy of the measurement. [ABSTRACT FROM AUTHOR]

BINGO is a project dedicated to explore new methods for background reduction in experiments searching for 0ν2β decay. It is based on bolometers, one of the most promising techniques to search for 0ν2β. CUORE and CUPID-Mo/0 are the main bolometric experiments that have illustrated the most relevant limiting factors on sensitivity the bolometers are facing. Surface αs are the main source of background in CUORE, and this contribution has been mitigated in CUPID-Mo/0 using dual heat-light channels, i.e., a main absorber embedding the 2β decay isotope facing a light detector. In this case, surface α rejection is achieved thanks to the lower α light output compared to β/γ. However, there are still other background components that limit the sensitivity of the experiments, such as pile-ups due to random coincidences of physical events, external γ background and β surface radioactivity. BINGO's proposed technology aims at reducing the background index down to 10−5 counts/(keV kg yr) in the region of interest, thus boosting the sensitivity on the effective Majorana neutrino mass. This can be achieved by: (i) having a revolutionary detector assembly with a reduction in the passive materials facing the detector; (ii) increasing the light detector sensitivity thanks to Neganov-Luke amplification; (iii) using an active shield, based on BGO scintillators with bolometric light detector readout to surround the experimental volume. The main text describes the listed approaches in detail, as well as the recent results of prototype tests. [ABSTRACT FROM AUTHOR]

Borexino has been a neutrino detector based on ultrapure liquid scintillator, located at the Laboratori Nazionali del Gran Sasso, Italy. Its main scientific goal was the real-time measurement of solar neutrino fluxes, which play an irreplaceable role for the comprehension of the mechanisms powering our star. Over the past two years, the Borexino collaboration has pursued the improvement of the CNO flux measurement, obtaining further indications about the solar metallicity. In a parallel way, Borexino has demonstrated for the first time the possibility of exploiting the directional Cherenkov information, in a liquid scintillator detector, for the detection of sub-MeV solar neutrinos. [ABSTRACT FROM AUTHOR]

The nuclide 176Lu is one of the few naturally occurring isotopes that are potentially unstable with respect to electron capture (EC). Although experimental evidence for 176Lu EC decay is still missing, this isotope is instead well known to β− decay into 176Hf with an half-life of about 38 Gyr. Previous searches for the 176Lu EC decay were performed by using a passive Lutetium source coupled with an HP-Ge spectrometer. Our approach uses a LYSO crystal both as Lutetium source and as an active detector and the obtained 176Lu EC branching ratio limits are 7 × 10−4 and 4.4 × 10−4 for the capture of the 1s and 2s electron, respectively. Previously known limits for the EC in 176Lu are improved by a factor 3 to 15 depending on the considered EC channel. [ABSTRACT FROM AUTHOR]

Mutual-Shielding Directional Gamma Detector excels at sensitivity and can achieve good angular accuracy and a large field of view. In this paper, we present, in detail, a method to optimize a mutual shielding directional detector array regarding the scintillators positioning for a given number and size of detection units. The optimization goals are improvement of accuracy and sensitivity. The optimization uses two types of fast, non-Monte-Carlo simulations since the simulation needs to generate measurements from all directions for each array formation tested. Both these simulations are explained and demonstrated. The presented method uses the ambiguity function to assess the accuracy and identify directions that may generate errors due to similar responses from other directions. Then, addressing these problematic directions can be fixed by changing the scintillators' positions or adding a partial shield to change the response at one of the similar directions. [ABSTRACT FROM AUTHOR]

Recently, it has been shown through both Monte Carlo simulations and experiments that scintillator-PMT interface reflection coefficients could depend on crystal thickness. It has been argued that the thickness-dependency on the interface reflection coefficient is a result of bulk attenuation and surface reflections. So far, only LYSO:Ce3+ scintillators have been tested to investigate thickness-dependent reflection coefficients. In this work, the simulations and experiments are extended to GAGG:Ce3+ crystals. Moreover, a new experimental technique (the dualPMT setup) has been tested to measure the interface reflection coefficients, and it has been shown through the dual-PMT setup that GAGG:Ce3+-PMT interface reflection coefficients are thickness-dependent with more than 1σ confidence. These results are also supported with extensive Monte Carlo simulations. [ABSTRACT FROM AUTHOR]

The market for SiPMs has grown rapidly in recent years, driven by their increasing use in applications such as medical imaging, nuclear and particle physics. Due to the growing demand, many manufacturers are now offering SiPMs, each of them with unique features and performance characteristics. As a result, it is essential to conduct comparative studies to evaluate and compare the performance of different SiPM arrays. Therefore, this work aims to compare the performance of assembled detectors based on two different SiPM arrays (AdvanSiD-NUV hybrid array ASD-NUV4S-P-4x4TD 17 mm x17 mm and the MPPC Hamamatsu S14161-6050HS-04 25 mm x 25 mm) coupled to two organic scintillators, a liquid scintillator EJ-309 (50 mm diameter x 50 mm thickness) and a plastic scintillator EJ-276G (25 mm diameter x 25 mm thickness). The assessment of the performance was made in terms of their energy resolution, time resolution, and capability to discriminate between γ-rays and fast neutrons. The outcomes show that the Hamamatsu SiPM array performs better for all of the characteristics studied, with the best configuration being when it was coupled to the EJ-309 liquid scintillator, obtaining the lowest energy and time resolutions, (0.108±0.004) and (0.599 ± 0.004) ns respectively, and the highest Figure of Merit (2.04 ± 0.01). A good Figure of Merit value that ensures an effective discrimination between fast neutrons and γ-rays. [ABSTRACT FROM AUTHOR]

In decommissioning of nuclear facilities the presence of activated steel requires the determination, along with other radionuclides, of 55Fe and 63Ni. These can be considered as hard-to-measure-radionuclides because of their low energy beta particles or X radiation emitted. Furthermore, those radionuclides are usually mixed with a relevant fraction of non-radioactive Fe and Ni. This implies that, in those cases involving very low radioactive samples close to background activity level, a significant mass of steel sample must be physically and chemically treated and analyzed to achieve the Minimum Detectable activity Concentration (MDC) required by the Authority for clearance purposes. Due to colour quenching the acquisition time is particularly long. Minimizing the colour effect is therefore important for laboratories that must perform many determinations in a reasonable time, achieving the MDC in accordance with the Authority requests. For this reason, the choice of solvent can be an important information to save analyses time. The intensity of the colour quenching is, in fact, strongly dependent on the type of acid used to solubilize the sample before the mixing with the liquid scintillation cocktail. Some types of acid can even increase the phenomenon while others can drastically reduce such an effect. The aim of this work is to offer, through a correlation study between sample concentration in the LSC vial and type of solvent used in dilution, a reliable method for quantifying 63Ni and 55Fe in steel samples with very low activity, close to the background level. [ABSTRACT FROM AUTHOR]

We present here the main results of an experimental activity aimed at the realization of a prototype of monitor for alpha and beta radioactivity in water exploiting a novel type of contamination-safe scintillation detector developed by our research group. Due to the short path-length of alpha and beta particles in water and the low detection limits needed to be compliant with the international legislations in matter of radiation safety for water, the detectors to be used for such a kind of instruments should have in general large area, very low intrinsic background and avoid any kind of window between the monitored water and the active volume of the detector. Even an extremely low contamination of the surface can therefore destroy the detector performance, while protecting the detector with a layer of passive material will reduce the detection efficiency, in particular for alpha particles, and the passive layer can get contaminated itself, making necessary its substitution and representing an important limitation to the realization of a radioactivity monitor that should work continuously for years. The novel detectors are large-area silicone-based scintillators developed and produced in our laboratories. The technology we propose is a significant step forward in the direction of the realization of radioactivity monitors for water with high sensitivity and reasonable costs, to be used to improve security and quality of the water distributed to European and worldwide citizens. The detection performance for alpha and beta particles was first tested in air with standard sources, showing results very close to similar detectors commercially available. Later a number of tests were carried out in the ENEA-INMRI laboratories with the aim to characterize the contamination and decontamination properties. Initial activity of each detector foil was checked by low background radioactivity measurements, then the detectors were immersed for fixed times and constant procedure in a variety of radioactive reference liquid solutions with different radionuclides in different chemical forms. After rinsing with distilled water the detector foils were again measured for residual radioactivity adsorbed on the foils surface. After this preliminary campaign of contamination measurements carried out on small size samples, several large area detectors were realized and used to build a small demonstrator device for continuous monitoring of the radioactivity in water. The monitor was tested with distilled water (blank) and radioactive aqueous solutions, demonstrating the possibility to realize a new generation of radiation monitors for water with high sensitivity and with the possibility to easily manage the contamination issues. [ABSTRACT FROM AUTHOR]

Orano Mining has relied on Nuclear Measurement Laboratories for several years to estimate calibration factors for borehole radiometric probes. The total gamma count rate recorded with a NaI(Tl) scintillation detector (NGRS probe) is converted into equivalent uranium grade using a calibration coefficient in s-1.ppmU-1 units, estimated thanks to different calibration blocks ranging from 0 to 10,000 ppm of uranium, at Orano CIME calibration facility in Bessines, France. Recently, Orano Mining embarked on an update of its measurement means by associating gamma spectrometry directly in the wellbore. Therefore, Orano Mining has recently tested a CeBr3 probe designed and developed by ALT (Advanced Logic Technology) to qualify a patented borehole spectroscopic method based on energy bands recently developed by CEA and Orano. In this context, we have implemented a fine Monte Carlo modelling of this new probe in order to correct the calibration coefficients as a function of different parameters such as the drilling diameter, the presence of a casing, the density of the mineralization, the distance of the probe with respect to the well or casing walls, etc. In the present work, we have simulated the CeBr3 probe in the concrete calibration blocks of Orano CIME. The MCNP model of the probe has been validated through a comparison with experimental data. The calibration coefficient determined by simulation is 11.6 s-1.ppm -1 > 10 % in total gamma counting, which is in good agreement with the one measured in Bessines, i.e. 10.6 s-1.ppm -1. The calculation vs. experiment agreement is also satisfactory (i.e. within 10 %) for spectroscopic energy bands used to characterize the uranium grade in case of disequilibrium in the uranium chain, when total count rate does not apply. This method recently developed for samples and boreholes will be tested in future work with this new CeBr3 probe. [ABSTRACT FROM AUTHOR]

The leakage neutron spectrum measurements have been done on benchmark spherical assembly-nickel sphere with a diameter of 50 cm and a copper cube (block) with dimensions of 49.5 x 49.5 x 48 cm3 in Research Centre Rez (RC Rez). The 252Cf neutron source was placed into the centre of nickel sphere and copper cube. The proton recoil method was used for the neutron spectrum measurement using spherical hydrogen proportional detectors (HPD) with pressure of 400 and 1000 kPa (diameter of detectors is 4 cm) and scintillation stilbene (ST) detector (diam. of 1 x 1 cm). The neutron energy range of spectrometer is from 0.04 MeV to 1.3 MeV for HPD and from 1 MeV to 12 MeV for ST. The adequate MCNP neutron spectrum calculations based on data libraries ENDF/B-VII.1, ENDF/B-VIII.0, JEFF-3.3, BROND-3.1 were done and compared with the experiment, i.e., calculation to experiment ratio C/E was determined. [ABSTRACT FROM AUTHOR]

The β-delayed neutron emission in the 85As β-decay has been measured at the IGISOL facility of the Accelerator Laboratory of the University of Jyväskylä (JYFL). The complete β-decay has been studied with a setup which consists of a plastic scintillator, the MOdular Neutron time-of-flight SpectromeTER (MONSTER), and two types of γ-rays detectors (HPGe and LaBr3). The, β-delayed neutron energy distribution has been determined by unfolding the TOF spectrum with the iterative Bayesian unfolding method. [ABSTRACT FROM AUTHOR]

The High Energy cosmic-Radiation Detection facility (HERD) is a calorimetric experiment planned to be launched in 2027. It will be operational for at least 10 years on board the China Space Station. With HERD we will measure the energy flux of cosmic protons and heavier nuclei from 30 GeV up to, for the first time in space, a few PeV. We will search for signatures of annihilation and decay products of dark matter in the energy spectrum of cosmic electrons and gamma rays from 10 GeV to 100 TeV. A wide field of view monitoring of the gamma-ray full-sky from 100 MeV will also be performed. The five HERD subdetectors, the calorimeter (CALO), the scintillating fiber tracker (FIT), the plastic scintillator detector (PSD), the silicon charge detector (SCD) and the transition radiation detector (TRD), are currently under development. The design, prospects and expected performance of HERD, as well as its contribution to the multimessenger astronomy will be presented in this contribution. [ABSTRACT FROM AUTHOR]

The 12C(α, y)16O reaction is important in the production of universal 16O, but its cross-section at the relevant energies of static helium burning is complex and uncertain. The total cross-section originates from a sum of resonance tails and direct captures, making the contributions of sub-threshold states difficult to estimate. One proposed method to estimate these contributions involves determining relevant reduced α-widths of the sub-threshold states through indirect measurements. Therefore, 19F(p, αy)16O reaction was used to populate α-unbound states in 16O using a 2.6 MeV proton beam on a CaF2 target. A detection system consisting of single and telescope configurations of Si detectors was used to detect 2α-particles and a 12C particle in coincidence. Scintillator detectors were included in the setup to study the de-excitation of the states populated in 16O to the ground state. Under good event conditions a preliminar indentification of the particles detected has been conducted. [ABSTRACT FROM AUTHOR]

Scintillation, beam wandering, and phase front distortion are the principal impacts of atmospheric turbulence on laser beam propagation. The aperture averaging concept might be used to minimize the effect for the first two, but the third, which is important for high-speed free-space communications, is significantly more challenging. More than ten years ago, the institute of communications and navigation (IKN) of the german aerospace centre (DLR) conducted optical downlink experiments with JAXA's OICETS/Kirari-Japan to study the optical LEO downlink channel and assess the viability of this transmission technology for upcoming applications. The present work will study and give a comparable insight into simulation and experimental results showing a significant relationship elevation dependency for parameters linked to index-of-refraction turbulence. [ABSTRACT FROM AUTHOR]

Tb3+-doped single-crystalline Gd3Ga5O12 layers are grown by Liquid Phase Epitaxy on (111)-oriented undoped substrates, and their structure, composition, morphology and photo- and radioluminescence are studied. Layers doped with 6 at.% Tb3+ with a thickness up to 20 μm appear promising for single crystal film scintillators with a sub-μm spatial resolution and waveguide lasers as they exhibit good quality, uniform distribution of Tb3+ ions, optimized light output (~50% of that for Ce:YAG), weak concentration quenching of luminescence and low afterglow for a 15 bit dynamic range. [ABSTRACT FROM AUTHOR]

We are investigating different micro- and nano-structure approaches to neutron detection based on inorganic scintillators. Specifically, we have been assessing various neutron converter-scintillator configurations through simulations and experiments. One promising inorganic scintillator is ZnO due to its relatively high light yield[1], reasonable optical transparency in the visible region[2], and relatively low refractive index[3] compared to other Zn-based crystals such as ZnS[4]. Accurate optical data and rigid simulation tools are necessary to optimize the dimensions of the neutron converter/scintillator systems. Accurate optical data are necessary since the optical parameters of a material depend on a variety of factors, including but not limited to its morphology, crystal structure, surface quality (surface roughness), as well as the temperature at which it was manufactured. Therefore, literature data show significant discrepancy when it comes to the optical parameters for the material and it is important to accurately measure these quantities for the specific sample of interest. Neutron detection is a complex process that includes neutron transport, charged particle transport, and light transport in the active detection medium. Hence, a rigid simulation tool is required to handle all these different areas of physics with sufficient accuracy. In this work, Geant4 has been chosen to carry out the simulations of these processes. Geant4 (GEometry ANd Tracking) is a toolkit used in various applications including high energy physics, astrophysics, and radiation detection[5]. The optical simulation capabilities of Geant4 have been validated by comparing the transmission and reflection data from UV-Vis spectroscopy to the Geant4 models for different Zn-based crystals. After validating the optical response of single crystals, simulation models were constructed to model more complex structures of ZnS-based alpha detection sheets (EJ-440) from Eljen Technology. Optical parameters validated with experimental results have been used in radiation simulation in Geant4. This study will serve as a basis for our ongoing effort to optimize and manufacture an efficient and compact fast neutron detection module with microand nano-structures. [ABSTRACT FROM AUTHOR]

We have characterized a Cerium doped Lanthanum Bromide (LaBr3(Ce)) crystal coupled with the position-sensitive photo-multiplier system for the gamma-ray imaging application. One can use this detector set-up for the scanning of high purity germanium detectors for pulse shape analysis in gamma-ray spectroscopy experiments and the image formation of an object by Compton back-scattering. The sensor has been tested for energy, timing and position information of the gamma-rays interacting within the detector crystal. The GEANT4 simulation results are consistent with the experimental results. We have reconstructed the image of irradiation spots in different positions throughout the detector crystal. Position resolution is found to be around 3.5 mm with the 2 mm collimated gamma-rays. The 2-d image of hexagonal Bismuth Germanate (BGO) crystal and a cylindrical LaBr3(Ce) crystal have been reconstructed in coincidence technique. The performance of the detector for imaging application has been investigated by coincidence technique in GEANT4 simulation and compared with the experimental data. We have reconstructed the 2-d images of objects with various geometrical shapes by Compton back-scattered events of the gamma-rays. This position-sensitive detector can be used as an absorber of a Compton camera for the image reconstruction of an extended radioactive source. One can also use this kind of set-up as in radiation imaging and many other applications where the energy and source position of the gamma-ray is the main interest. [ABSTRACT FROM AUTHOR]

Proton therapy technique for cancer treatment offers a high selectivity with respect to conventional radiotherapy with X- and γ-rays due to the properties of the interaction of protons with matter. Very accurate and precise treatment plans and a good control on the dose deposition are required to exploit the full potential of the technique. The substitution of the currently used X-ray Computed Tomography (xCT) by proton Computed Tomography (pCT) in the design of treatment plans would allow for a reduction in proton range uncertainties. This would make possible an important improvement in the accuracy and precision of treatment plans. With this aim, a prototype of pCT scanner is under study. It includes two tracking detectors which provide information on the proton trajectories and a residual energy detector to determine the energy loss while traversing the object scanned. A proof-of-concept experiment has been performed using low-energy protons and a simplified prototype with only the two tracking detectors. The results obtained in the measurement are presented and discussed. [ABSTRACT FROM AUTHOR]

This research presents a design of a resilient blind-tube radiometric logging probe, which satisfies key, operational site constraints, for direct in-situ characterization of subsurface radioactivity, particularly caesium-137 and strontium-90. The probe comprises a commercially-available Ø10 mm × 9.5 mm CeBr3 scintillator detector attached to a compact digitizer unit, in a resistant and waterproof housing. The probe is designed to be lowered down into metallic Ø 75 mm blind-tubes by means of a winch system. [ABSTRACT FROM AUTHOR]

This paper presents the concept of an active dosimetry system and its operational regime for pulsed radiation dose rate measurements. The plastic scintillator is suggested to be used for absorbed dose rate measurements. As long as the detector can be considered tissue equivalent, the energy weighting of pile-up events in terms of the dose is achieved. The real-time distinction of pulsed and non-pulsed dose rate contributions is based on the time structure of a single interaction and requires only basic information about the beam time structure (pulses duration and period). The detector connected to a fully digital signal processing board creates an active dosimetry system with adjustable parameters. Such a system was used for absorbed dose rate measurements in pulsed photon field mimicking radiation field outside the bunker of a medical LINAC, but also in the presence of a constant radiation component. The results show a linear dependence of a pulsed radiation contribution on the accelerator current in the investigated range of the total dose rate up to 8 μGy/h. [ABSTRACT FROM AUTHOR]

This work addresses the use of plastic scintillators as an alternative to 3He detectors for radioactive waste drum characterization. The time response of scintillators is three orders of magnitude faster than that of gas proportional counters and they offer similar neutron detection efficiency at lower cost. However, they are sensitive to gamma rays and the commonly used Pulse Shape Discrimination technique is not possible with basic PVT scintillators. This paper reports on an innovative data processing technique allowing to extract spontaneous fission events from parasitic coincidences, such as those from the (α,n) reactions accompanied by correlated gamma rays or from pure gamma-ray sources emitting correlated radiations. The proposed approach makes advantage of differences in the pulse detection times recorded in measurements with the 252Cf, AmBe and 60Co sources. More precisely, a 2D histogram of time delays between the detected 2nd and 1st pulses, on the x-axis, and between the 3rd and 2nd pulses, on the y-axis, is found to allow for selection of a region of interest most relevant to spontaneous fission events. [ABSTRACT FROM AUTHOR]

In this paper we study quality of three types of organic scintillators stilbene, p-terphenyl and EJ-299-33. We used monoenergetic neutron fields with a wide range of neutron energies in PTB Braunschweig. All the tests were carried out with NGA-01 spectrometer. The results of the measurements are evaluated spectra from the spectrometer. We discuss the quality of each scintillator, such as the FWHM of the peaks. [ABSTRACT FROM AUTHOR]

Obtaining directional information is required in many applications such as nuclear homeland security, contamination mapping after a nuclear incident and radiological events, or during the decontamination work. However, many directional radiation detectors are based on directional shielding, made of lead or tungsten collimators, introducing two main drawbacks. The first is the size and weight, making those detectors too heavy and irrelevant for utilization in handheld devices, drone mapping, or space applications. The second drawback is the limited field of view, which requires multiple detectors to cover the whole required field of view or machinery to rotate the narrow field of view detector. We propose a novel 4π directional detector based on a segmented hollow cubic detector, which uses the Compton effect interactions with no heavy collimators. The symmetrical cubical design provides both higher efficiency and 4π detection ability. Instead of traditional two types of detectors (scatterer and absorber) structure, we use the same type of detector, based on GAGG(Ce) scintillator coupled to silicon photomultiplier. Additional advantage of the proposed detector obtained by locating the photon sensors inside the detector, behind the scintillators, which improves the radiation hardness required for space applications. Furthermore, such arrangement flattens the temperature variation across the detector, providing better gain stability. The main advantage of the proposed detector is the ability of 4pi radiation detection for high energy gamma-rays without the use of heavy collimators. [ABSTRACT FROM AUTHOR]

During a severe accident in either sodium-cooled or water-cooled nuclear reactors, jets of molten nuclear fuel may impinge on the coolant resulting in fuel-coolant interactions (FCI). Experimental programs are being conducted to study this phenomenology and to support the development of severe accident models. Due to the optical opacity of the test section walls, sodium coolant, and the apparent optical opacity of water in the presence of intense ebullition, high-speed X-ray imaging is the preferred technique for FCI visualization. The configuration of these X-ray imaging systems, whereby the test section is installed between a fan-beam X-ray source and a scintillator-image intensifier projecting an image in the visual spectrum onto a high-speed camera, entails certain imaging artefacts and uncertainties. The X-ray imaging configuration requires precise calibration to enable detailed quantitative characterization of the FCI. To this end, 'phantom' models have been fabricated using polyethylene, either steel or hafnia powder, and empty cavities to represent sodium, molten fuel and sodium vapor phases respectively. A checkerboard configuration of the phantom enables calibration and correction for lens distortion artefacts which magnify features towards the edge of the field of view. Polydisperse steel ball configurations enable precise determination of the lower limit of detection and the estimation of parallax errors which introduce uncertainty in an object's silhouette dimensions. Calibration experiments at the MELT facility determined lower limits of detection in the order of 4 mm for steel spheres, and 1.7-3.75 mm for vapor films around a molten jet. [ABSTRACT FROM AUTHOR]

Three 1-mm3 miniature fiber-coupled scintillators have been used to perform cm-wise resolution measurements of the thermal neutron flux within experimental channels of the SUR-100 facility, a zero power thermal reactor operated by the Institute of Nuclear Technology and Energy Systems at the University of Stuttgart. The detection system is developed at the École Polytechnique Fédérale de Lausanne in collaboration with the Paul Scherrer Institut. Thermal neutrons count rates were measured along the experimental channels I and II, which cross the reactor at the center and tangentially to the core, respectively. The reactor was modelled with the Monte Carlo neutron transport code Serpent-2.1.31. The comparison of experimental and computed reaction rate distributions showed a good agreement within the core region, with discrepancies within 2σ. An unexpected discrepancy, probably caused by a geometric inconsistency in the computational model of the reactor, was observed in the reflector region of the experimental channel I, where a 20% difference (i.e. 8σ) was found between experimental and simulated results. Significant discrepancies, respectively worth 10σ and 15σ, were noticed at distance, in the lead shielding region, for both experimental channels I and II. In addition, reaction rate gradients across the 2.6 cm and 5.4 cm diameters of both channels were measured. A horizontal reaction rate gradient of (9.09 ± 0.20) % was measured within 2.4 cm across the diameter of the experimental channel II, with a difference from computed results of 2%. The absence of a vertical reaction rate gradient inside the experimental channel I was confirmed by measurements. [ABSTRACT FROM AUTHOR]

We report in the present article on the successful observation using noise analysis of the lateral oscillation of one fuel rod by ±2.5 mm around nominal at 0.1 Hz frequency, using an mm3 miniature neutron scintillator at the rod level, and a BGO gamma detector seven meters away from the reactor core center. The experiment was conducted as part of the COLIBRI program in the CROCUS reactor, which is dedicated to the investigation of reactor noise induced by fuel vibrations. It consists in experiments on rod lateral displacement (static) and oscillation (dynamic) with different rods' numbers at various relevant amplitudes and frequencies. Its main motivation is the increased amplitudes in the neutron noise distributions recorded in ex- and in-core detectors that have been observed in recent years in Siemens pre-Konvoi type of PWR reactors. The obtained experimental data are used for the purpose of code validation, especially within the framework of the European project CORTEX on reactor noise applications. During the first phase of COLIBRI, the observation of a spatial dependence of the perturbation noise, also called neutron modulation, was demonstrated. In the second phase of COLIBRI starting 2021, it is planned to use a core mapping array of neutron detectors to record its propagation. It consists in about 150 miniature scintillators coupled to optical fibers and SiPM readouts, to be distributed in the reactor core. As a feasibility test, experiments were performed using a miniature scintillator prototype placed on a fuel rod, and oscillating the instrumented rod or the one directly adjacent to the detector. In addition, it is theoretically possible to measure branching or perturbation reactor noise using gamma radiation. Following recent developments on gamma measurements in CROCUS, the fuel oscillation was simultaneously recorded with a gamma detection array, LEAF. Its large BGO detectors were used by placing them at the maximum distance to the core, i.e. seven meters away with a clear line of sight using an experimental channel through the shielding of the reactor cavity. [ABSTRACT FROM AUTHOR]

The present article provides an overview of the design of a three-dimensional (3D) full-core mapping system for the CROCUS reactor, operated at the École polytechnique fédérale de Lausanne (EPFL), Switzerland. The system is composed of 149 miniature neutron detectors distributed within the core double lattice at three main axial levels. The miniature detector technology is based on the optimization of the well-proven coupling of a miniature ZnS:6LiF(Ag) scintillator to a state-of-the-art silicon photomultiplier (SiPM) via jacketed optical fibers. The challenges in the mechanical design, the detector optimization, the core criticality, and the development of the acquisition electronics are strongly interconnected and their combination is addressed in this article. The 3D full-core mapping system is foreseen to be installed in CROCUS in autumn 2021 and it will pave the way for the investigation of 3D dynamic phenomena in nuclear reactor cores. [ABSTRACT FROM AUTHOR]

The construction of the portable spectrometer, MULTI, is designed for the measurement of β-γ-neutron coincidences on beams of radioactive exotic nuclei. It will be used in measurements of the β-decay process of neutron-rich nuclei with large Qβ values accessible in radioactive beams facilities. The experimental technique includes the measurement of the ratios between gamma-ray emission and multi-neutron emission, following beta-decay of radioactive nuclei implanted into an active target. The construction of a gamma-ray spectrometer based on high-volume CeBr3+NaI(Tl) phoswich scintillation detectors is introduced. Results of the measurements of its fundamental characteristics – total detection efficiency, peak efficiency and Compton suppression effect with a 60Co source are presented. Design of the neutron counter array, consisting of 40 proportional counters filled with 3He gas, was optimized with Monte Carlo simulations. Results were validated with a 252Cf spectroscopic source, leading to expected detection efficiency of ∼35% for neutrons with energy < 1MeV. Further development plans are discussed. [ABSTRACT FROM AUTHOR]

The Active Target ATS (Active Target for SPES) is a new time-projection chamber designed for reaction and decay studies with nuclei far from stability. The physics cases for the new-generation active target are related to the ongoing developments of facilities for radioactive ion beams. Thanks to its flexibility, this instrument will be capable of taking advantage of the most exotic beams which will become available at the SPES facility under construction at the Legnaro National Laboratories in Italy. Particular attention will be also paid to couple it with ancillary detectors, for both charged and neutral (gamma and neutrons) particles. In particular, in this work, we will focus the attention on the neutron ancillary detectors. The proposed prototype is a compact device able to discriminate, by performing pulse shape analysis, between neutrons and gamma. The device take advantage of recent improvements in silicon photomultiplier (SiPM) technology and the development of new plastic scintillators exhibiting neutron/gamma discrimination capability. Our work is focused on the read-out with silicon photomultipliers arrays of EJ-276 (and its old version EJ-299) and EJ-276G scintillators of several sizes (ranging from 20 mm to 50 mm diameter). Moreover, we will show the comparison of discrimination performances between SiPM and standard photomultiplier read-out configurations. [ABSTRACT FROM AUTHOR]

An effort is underway to develop streaming readout data acquisition system for the CLAS12 detector in Jefferson Lab's experimental Hall-B. Successful beam tests were performed in the spring and summer of 2020 using a 10GeV electron beam from Jefferson Lab's CEBAF accelerator. The prototype system combined elements of the TriDAS and CODA data acquisition systems with the JANA2 analysis/reconstruction framework. This successfully merged components that included an FPGA stream source, a distributed hit processing system, and software plugins that allowed offline analysis written in C++ to be used for online event filtering. Details of the system design and performance are presented. [ABSTRACT FROM AUTHOR]

Generative machine learning models offer a promising way to efficiently amplify classical Monte Carlo generators' statistics for event simulation and generation in particle physics. Given the already high computational cost of simulation and the expected increase in data in the high-precision era of the LHC and at future colliders, such fast surrogate simulators are urgently needed. This contribution presents a status update on simulating particle showers in high granularity calorimeters for future colliders. Building on prior work using Generative Adversarial Networks (GANs), Wasserstein-GANs, and the information-theoretically motivated Bounded Information Bottleneck Autoencoder (BIB-AE), we further improve the fidelity of generated photon showers. The key to this improvement is a detailed understanding and optimisation of the latent space. The richer structure of hadronic showers compared to electromagnetic ones makes their precise modeling an important yet challenging problem. We present initial progress towards accurately simulating the core of hadronic showers in a highly granular scintillator calorimeter. [ABSTRACT FROM AUTHOR]

To sustain the harsher conditions of the high-luminosity LHC, the CMS collaboration is designing a novel endcap calorimeter system. The new calorimeter will predominantly use silicon sensors to achieve sufficient radiation tolerance and will maintain highly-granular information in the readout to help mitigate the effects of pileup. In regions characterised by lower radiation levels, small scintillator tiles with individual on-tile SiPM readout are employed. A unique reconstruction framework (TICL: The Iterative CLustering) is being developed to fully exploit the granularity and other significant detector features, such as particle identification and precision timing, with a view to mitigate pileup in the very dense environment of HL-LHC. The inputs to the framework are clusters of energy deposited in individual calorimeter layers. Clusters are formed by a density-based algorithm. Recent developments and tunes of the clustering algorithm will be presented. To help reduce the expected pressure on the computing resources in the HL-LHC era, the algorithms and their data structures are designed to be executed on GPUs. Preliminary results will be presented on decreases in clustering time when using GPUs versus CPUs. Ideas for machine-learning techniques to further improve the speed and accuracy of reconstruction algorithms will be presented. [ABSTRACT FROM AUTHOR]