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Nuclide production cross sections for proton-induced reactions on Mn and Co at incident energies of 1.3, 2.2, and 3.0 GeV were measured by the activation method at the Japan Proton Accelerator Research Complex (J-PARC). In total, 143 production cross sections of reaction products with half-lives ranging from 1.8 h to 2.6 yr were obtained. Among them, the cross sections of 55Mn(p,x)38S, 55Mn(p,x)41Ar, and 59Co(p,x)38S reactions were measured for the first time. The stable proton beam and well-established beam profile-motoring system contributed to the reduction of the systematic uncertainties to typically less than 5%, which was better than those of the previous data (typically ∼ 10%). To examine the prediction capabilities of spallation reaction models and evaluated nuclear data library, the measured data were compared with the spallation reaction models in PHITS (INCL4.6, Bertini, and JAM as intranuclear cascade models, and GEM as an evaporation model), INCL++/ABLA07, and the JENDL/HE-2007 library. The comparison of the mean square deviation factors indicated that both INCL4.6/GEM and JENDL/HE-2007 showed better agreement with the measured data than the others.

The general performance of diffractometers at the first long pulse spallation source ESS, is compared with their counterparts at J-PARC, a short pulse spallation source. The difference in the inherent pulse structure of these neutron sources presents opportunities for new concepts for instrumentation, where performance does not scale simply with source power. The article describes advantages and disadvantages of those diffractometers, adapting to the very different source characteristics. We find that the two sources offer comparable performance in flux and resolution when operating in high-resolution mode. ESS offers significant advantages in tunability and flexibility, notably in the ability to relax resolution in order to increase flux for a given experiment. The slow repetition rate of ESS favors long instruments. On the other hand, J-PARC instruments perform very well in spite of the lower source power and allow better access to epithermal neutrons, of particular interest for PDF analysis of diffraction data.

Canada’s access to neutron beams for neutron scattering was significantly curtailed in 2018 with the closure of the National Research Universal (NRU) reactor in Chalk River, Ontario, Canada. New sources are needed for the long-term; otherwise, access will only become harder as the global supply shrinks. Compact Accelerator-based Neutron Sources (CANS) offer the possibility of an intense source of neutrons with a capital cost significantly lower than spallation sources. In this paper, we propose a CANS for Canada. The proposal is staged with the first stage offering a medium neutron flux, linear accelerator-based approach for neutron scattering that is also coupled with a boron neutron capture therapy (BNCT) station and a positron emission tomography (PET) isotope production station. The first stage will serve as a prototype for a second stage: a higher brightness, higher cost facility that could be viewed as a national centre for neutron applications.

The purpose of this paper is to present the Monte-Carlo calculations performed to design a special element called gamma blocker (GB), necessary to stop the gamma radiation in the Accelerator-to-Target (A2T) section of European Spallation Source (ESS) linac. Very high levels of gamma radiation emitted backward from the activated target through the beam pipe could effectively block any human intervention close to the beam transport system. The residual dose rate in the linac tunnel was calculated without and with different GBs as a function of time. The final GB material and dimensions are proposed.

The properties of materials applied in fission and fusion reactors and targets of spallation neutron sources can be greatly degraded by radiation-induced transmutants. A precise prediction of the production of transmutants is highly important for the safety assessment of these facilities. The prediction is normally made using neutronic calculations. Experimental validation of the calculation results is essentially necessary, but usually very challenging. In the present work, a quantitative analysis of transmutants in ferritic-martensitic (FM) steels F82H, Eurofer 97, and ODS Eurofer after irradiation at 9.6 and 19.6–21 dpa in the SINQ targets was performed using Atom Probe Tomography (APT). The results indicate that solid transmutants Ti, Sc, Ca, K, Cl, and S can be precisely measured and a gas element Ar could also be detected. The difference between the measured concentrations and that calculated with the MCNPX code is less than 30% for most of detectable nuclides of the transmutants. This work demonstrates that the neutronic calculations applied to STIP irradiation experiments are reliable.

Gas electron multiplier (GEM) detectors and activation foils have been used for dosimetry of thermal beamlines of a pulsed neutron source. The first is an active detector that performs measurements using the time-of-flight technique, taking advantage of the pulsed nature of the source. The same detector has been used successfully to measure the profiles of the beams. The second is a passive irradiation method that independently confirms the measured fluxes of equipment materials and mechanics analyzer (EMMA) and rotating analyzer crystal (X) spectrometer (ROTAX) beamlines of the ISIS neutron source. They feature different thermal spectra, the first being moderated with water (300 K) and the second with liquid methane (100 K). These two characterized beamlines have been used for the irradiation of microelectronics for single-event effect testing using a reference static random access memory (SRAM) module. It is shown that results are consistent and that a correction factor must be applied to scale the results on the cold beamline to the one at room temperature.

A promising method for the production and extraction of 52Fe utilizing near-symmetric, heavy-ion fusion-evaporation reactions is presented. A 28Si beam was used to bombard a 27Al target, producing 52Fe through the reaction: 27Al (28Si, p2n)52Fe. After irradiation, the aluminum target was dissolved, and the 52Fe was separated from the aluminum matrix and other reaction products through the use of a cationic-exchange column. It was possible to recover the 52Fe (t1/2 = 8.3 h) with high specific activity, higher than can be achieved with the high energy proton spallation reactions currently used to produce this isotope, which has significance in medical research. The production yields for this reaction were measured and compared to PACE4 calculations. These results demonstrate the potential for dedicated accelerator production of 52Fe using heavy-ion beams, which will result in higher specific activities with robust radiochemical purification techniques.

A number of neutronics of JNIR big uranium target are simulated towards the planning of experimental investigations aimed to the transmutation of radioactive waste. Integral data of the neutron yield and energy spectra are given for several homogeneous spallation targets which are planned to be used as insertions in uranium blanket. Combined spallation targets are also of interest, because it can help to obtain an optimal neutron energy spectrum for effective burning of long-lived fission products and minor-actinides. For this purpose, uranium-beryllium dual insertion was also considered and described in this work.

A thick target neutron yield (TTNY) for a mercury target at an angle of 180°from the incident beam direction was measured with the time-of-flight method using a 3-GeV proton beam at the Japan Proton Accelerator Research Complex (J-PARC). Comparison of the experimental results with a Monte Carlo particle transport simulation by the Particle and Heavy Ion Transport code System (PHITS) shows that the default spallation model of PHITS, the Liege intranuclear cascade model version 4.6 coupled with the generalized evaporation model (INCL4.6/GEM) reproduces the measured TTNY fairly well, whereas apparent overestimation is observed for the former default model, the Bertini intranuclear cascade model coupled with GEM (Bertini/GEM). These trends are consistent with the experimental results of neutron-induced reaction rates obtained using indium and niobium activation foils.

Beryllium reflectors are used at spallation neutron sources in order to enhance the low-energy flux of neutrons emanating from the surface of a cold and thermal moderator. The design of such a moderator/reflector system is typically carried out using detailed Monte-Carlo simulations, where the beryllium reflector is assumed to behave as a poly-crystalline material. In reality, however, inhomogeneities in the beryllium could lead to discrepancies between the performance of the actual system when compared to the modeled system. The dependence of the total cross-section in particular on crystallite size, in the Bragg scattering region, could influence the reflector performance, and if such an effect is significant, it should be taken into account in the design of the moderator/reflector system. In this paper, we report on the preliminary results of using cross-section libraries, which include corrections for the crystallite size effect, in spallation source neutronics calculations.

The European Spallation Source being constructed in Lund, Sweden will provide the user community with a neutron source of unprecedented brightness. By 2025, a suite of 15 instruments will be served by a high-brightness moderator system placed above the spallation target. The ESS infrastructure, consisting of the proton linac, the target station, and the instrument halls, allows for implementation of a second source below the spallation target. We propose to develop a second neutron source with a high-intensity moderator able to (1) deliver a larger total cold neutron flux, (2) provide high intensities at longer wavelengths in the spectral regions of Cold (4–10 Å), Very Cold (10–40 Å), and Ultra Cold (several 100 Å) neutrons, as opposed to Thermal and Cold neutrons delivered by the top moderator. Offering both unprecedented brilliance, flux, and spectral range in a single facility, this upgrade will make ESS the most versatile neutron source in the world and will further strengthen the leadership of Europe in neutron science. The new source will boost several areas of condensed matter research such as imaging and spin-echo, and will provide outstanding opportunities in fundamental physics investigations of the laws of nature at a precision unattainable anywhere else. At the heart of the proposed system is a volumetric liquid deuterium moderator. Based on proven technology, its performance will be optimized in a detailed engineering study. This moderator will be complemented by secondary sources to provide intense beams of Very- and Ultra-Cold Neutrons.

The neutron Time-Of-Flight (n_TOF) facility at the European Laboratory for Particle Physics (CERN) is a pulsed white-spectrum neutron spallation source producing neutrons for two experimental areas: EAR1, located 185 m downstream of the spallation target, and EAR2, located 20 m above the target. The facility is based on a lead target impacted by a high-intensity 20 GeV/c proton beam. It is designed to study neutron-nucleus interactions for neutron kinetic energies from a few meV to several GeV, with applications in nuclear astrophysics, nuclear technology, and medical research. The facility is undergoing a major upgrade in 2019–2020, which will include the installation of the new third-generation target. The second-generation target consists in a water-cooled lead cylinder, while the new target will be cooled by nitrogen to avoid erosion-corrosion phenomena and contamination of the cooling water with radioactive lead spallation products. The new design will be optimized also for the vertical flight path. The operation of the new spallation target will start in 2021. This paper presents an overview on the evolution of the design and on the related R&D activities (including beam irradiation tests) carried out to ensure the best performance for both experimental areas and avoid the contamination issues of the previous targets.

At the ISIS Spallation Neutron Source at the Rutherford Appleton Laboratory in the UK, lifetimes of tantalum-clad tungsten targets on the Second Target Station (TS-2) have not been as long as expected. Analyses of gamma-ray spectra accumulated in the target services area suggest that erosion within the target is characterised by two exponentially increasing functions of time, one tentatively identified with initial erosion of the tantalum cladding, and the other identified with subsequent leaching of tungsten.

Failures (or upsets) of complementary metal-oxide-semiconductor (CMOS) devices, due to direct ionization from protons, were first predicted in 1982 and subsequently realized in 2007 for low-energy (1 MeV) protons (LEPs). For terrestrial applications, secondary LEPs, generated during collision events, may cause upsets, especially in cells far away from the initial strike location than their heavier spallation-fragment cousins. However, direct ionization may be more important in space and high-altitude environments due to the large flux of primary high-energy protons impinging on nearby spacecraft (and local device) shielding. In this article, a brief review of the relevant literature will be followed by a discussion of the sensitivity to direct ionization of typical CMOS devices. It will be shown that a significant number of LEPs are generated by cosmic radiation spallation events, suggesting that track structures and exact device hit locations need to be understood and effectively modeled, especially for modern devices. Also, the rate of multiple cell upsets, and hence multiple bit upsets, in these environments will be explored, with possible mitigation techniques discussed. The published work on muons and delta electrons, in addition to LEPs, will be reviewed as potential single-event upset (SEU) sources with the future scaling of CMOS devices.

Deposition of plasma energy during off-normal fusion reactor operational events delivers a transient heat flux of up to 100 MJ/m 2 to the plasma-facing materials (PFMs). Understanding the exact material response to the extreme energy loading conditions plays a key role in establishing a realistic computational tool that simulates the fusion plasma-material interaction. Surface damage can occur due to vaporization, melting, spallation, and liquid splatter. However, splashing mechanisms such as boiling and splattering, which result from various liquid instabilities, appear to be the main mechanism contributing to the melt layer erosion. The primary focus of this article is melting and resolidification and the effect of redeposition of the eroded material on surface erosion. A set of selected PFMs was exposed to a plasma heat flux of up to 40 GW/m 2 over a deposition duration of 200 μs. The source of the high energy plasma used in this article is the Surface InteRaction Experiment at North Carolina State (SIRENS) plasma source, which used to simulate disrupted plasma conditions. The underlying erosion mechanisms involved in the formation, ejection, and solidification of molten droplets are investigated using the basic plasma equations and a plasma fluid model implemented in the simulation code. The net erosion and redeposition thickness due to erosion of the vapor and melt layer have been evaluated post-plasma exposure and compared to the experimental measurements.

The energy deposition spectra in a silicon detector have been measured at chip irradiation (ChipIr) and Cern High energy AcceleRator Mixed field (CHARM) facilities. The measurement was possible thanks to a fast electronic chain that can cope with high instantaneous fluxes. A computational study of the energy deposition in a silicon detector allows for the comparison of high-energy spallation facilities dedicated to the irradiation of microelectronics and for the validation of radiation transport models. The measured time structure of the facilities pulses is also presented with an example on how to use this result to correct in the case of large dead times (DTs).

A new facility, the N = 126 factory, is currently under construction at Argonne National Laboratory. It will use multi-nucleon transfer reactions to create neutron-rich isotopes of very heavy elements for studies of interest to the formation of the A ∼ 195 abundance peak in the r-process. This region of the nuclear chart is difficult to access by standard fragmentation or spallation reactions and as a result has remained mostly unexplored. The nuclei of interest, very neutron-rich isotopes around Z = 70–95, will be produced by multi-nucleon exchange of a high intensity 10 MeV/u heavy-ion beam on the most neutron-rich stable isotopes of heavy elements such as 198 Pt and 238 U . This reaction mechanism can transfer a large number of neutrons and create very neutron-rich isotopes with larger than mb cross-section. The reaction mechanism is a nuclear surface process and the reaction products come out close to the grazing angle, which makes them very difficult to collect. The N = 126 factory circumvents this difficulty by using a unique large high-intensity RF gas catcher, similar to the one currently in operation at CARIBU, to collect the target-like reaction products and transform them into a low-energy beam that will then be mass separated with a medium resolution electromagnetic separator ( Δ M/M ≃ 1/1500), followed by an RFQ buncher and an MR-TOF ( Δ M/M ≃ 1/100,000) system. The extracted radioactive beams will be essentially pure and available at low-energy for mass measurements with the CPT mass spectrometer or decay study with the X-array.

The production of high intensity and isobarically pure neutron-rich fission fragments is of high importance for the physics research program of the ISOLDE facility at CERN. This is typically done in a two-step method where a tungsten converter, positioned parallel and below the UCx target, is irradiated with 1.4 GeV protons. This will produce spallation neutrons which irradiate a UCx target producing the isotopes of interest. Currently, the in-target production is limited by the geometrical overlap of the neutron fluence and the target material and suffers from low production yield. In this work, a prototype is proposed where the tungsten converter is positioned in the center of an annular UCx target. FLUKA simulations were conducted to optimize the geometry, maximizing the production of isobarically pure neutron-rich fission fragments which determined that a large diameter target is necessary (5 cm). Thermo-electric ANSYS® simulations were conducted in order to develop a large Ta target oven which can reach 2000 °C and tests were conducted to benchmark the simulations. A prototype design was validated, for ISOLDE operation, with offline tests which shows that the tungsten-graphite-tantalum assembly is fully stable up to 2200 °C.

The JSNS^2 (J-PARC Sterile Neutrino Search at J-PARC Spallation Neutron Source) experiment aims to search for oscillations involving a sterile neutrino in the eV^2 mass-splitting range. The experiment will search for the appearance of electron antineutrinos oscillated from muon antineutrinos. The electron antineutrinos are detected via the inverse beta decay process using a liquid scintillator detector. A 1MW beam of 3 GeV protons incident on a spallation neutron target produces an intense and pulsed neutrino source from pion, muon, and kaon decay at rest. The JSNS^2 detector is located 24 m away from the neutrino source and began operation from June 2020. The detector contains 17 tonnes of gadolinium (Gd) loaded liquid scintillator (LS) in an acrylic vessel, as a neutrino target. It is surrounded by 31 tonnes of unloaded LS in a stainless steel tank. Optical photons produced in LS are viewed by 120 R7081 Hamamatsu 10-inch Photomultiplier Tubes (PMTs). In this paper, we describe the JSNS^2 detector design, construction, and operation., 41 pages, 29 figures

The transmutation of long-lived fission products through spallation induced by light nuclides was investigated for the purpose of determining the feasibility of this approach for long-lived fission products, in both economic and environmental terms. The cross-section data were obtained from the TALYS Evaluated Nuclear Data Library (TENDL). A thick target model was used to study the consumption of the target isotopes in the transmutation process. The transmutation yield was calculated using the highest beam intensity available with the China initiative accelerator-driven system. It was found that the light nuclide-induced spallation reaction can significantly reduce the radio toxicity of the investigated long-lived fission products. Using the transmutation target made of elemental LLFP and the proton beam with an intensity of 5 mA, the consumption of $${}^{90} \mathrm {Sr}$$ , $${}^{93} \mathrm {Zr}$$ , $${}^{107} \mathrm {Pd}$$ , or $${}^{137} \mathrm {Cs}$$ can reach approximately 500 g per year.

Deuteron-driven spallation targets have garnered attention recently because they can provide high-energy neutrons to transmute long-lifetime fission products. In this study, the Geant4 toolkit was used to simulate the interaction between a deuteron beam at 500 MeV and a composite target composed of alternating lead-bismuth eutectic (LBE) and water. The water was used because it may be employed as a target coolant. The energy spectrum, neutron yield, average energy, and total energy of the emitted neutrons were calculated for different thicknesses and thickness ratios between the LBE and water. For a constant target thickness, the neutron yield increases with an increasing thickness ratio of LBE to $$\hbox {H}_2\hbox {O}$$ , while the average energy of the emitted neutrons decreases with an increasing in the aforementioned thickness ratio . These two aspects support the use of a pure target, either LBE or water. However, with an increasing LBE-to- $$\hbox {H}_2\hbox {O}$$ thickness ratio, the total energy of the emitted neutrons increases and then decreases. This result supports the addition of water into the LBE target. The angular distributions of the emitted neutrons show that the rear of the target is suitable for loading nuclear waste containing minor actinides and long-lifetime fission products.

This paper presents an approach to uncertainty estimation of spallation particle multiplicity of lead (natPb), primarily focusing on proton-induced spallation neutron multiplicity (xpn) and its pro...

The robustness of the linear combination method to neutron source is demonstrated in the pulsed neutron source (PNS) experiment. The linear combination method reduces the spatial higher-mode (HM) c...

The microstructure of EUROFER and ODS-EUROFER has been characterized by means of positron annihilation spectroscopy (PAS) with a particular focus on the effect of irradiation conditions. Two different irradiation experiments have been used to introduced helium-filled cavities in the studied materials. Materials irradiated in spallation neutron target SINQ have been investigated by conventional positron annihilation spectroscopy, while helium-implanted samples of the same materials have been investigated by slow positron beam technique. With this approach, we were able to obtain a significant amount of positron lifetime and Doppler broadening data and evaluate them with respect to the dpa, irradiation temperature and helium concentration effects. Both types of irradiation experiments confirm a more pronounced creation of growing open-volume defects for the Eurofer steel, comparing to its ODS variant. The bubble-to-void transformation was indirectly but clearly confirmed by the Eurofer specimens. In the case of the ODS Eurofer, the coalescence of helium bubbles, accompanied by saturation of positron mean-lifetime and/or S parameter, was not so evident. This present study provides the first experimental positron annihilation data, showing the onset of void formation in ODS steels.

For enhancing accident tolerance in current operating LWRs, Zr-based claddings with a protective layer, which have outstanding resistance to high-temperature oxidation, are selected as strong candidates for accident-tolerant fuel claddings. One of the key factors determining the successful application of these coated claddings is their ability to maintain their coating layer during normal operation without significant damage. This study aimed to verify the scratch and fretting wear behaviors of coated Zircaloy-4 claddings deposited with a Cr–10Al binary alloy target (CrAl) by the arc ion plating method. In the scratch tests, the commercial Zircaloy-4 samples showed accumulated scratch grooves with ductile chipping caused by adhesive failure. However, there was no gross spallation, except for well-developed scratch traces caused by plastic deformation, on the entire stroke length of the CrAl-coated Zircaloy-4. The wear resistance of the CrAl-coated Zircaloy-4 against the as-received Zr grid was improved significantly because of its high load support capability owing to the coating layer and the formation of a load-bearing layer by the material transfer when compared with the results of the uncoated Zircaloy-4. Furthermore, when the Zr grid was pre-oxidized, the wear amount of the CrAl-coated Zircaloy-4 became negligible owing to the formation of a glaze layer by the interaction with the surface oxide of the Zr grid. According to the results of the high-temperature steam oxidation tests, the defected region of the CrAl coating layer caused by the scratch and fretting wear showed no further significant damage and still acted as a protective layer for enhancing the accident tolerance of the fuel cladding.

Multiple-cell upset (MCU) in static random access memory (SRAM) is a major concern in radiation effects on very large scale integration (VLSI) since it can spoil error correcting codes (ECCs). Neutron-induced MCUs have been characterized for terrestrial environment. On the other hand, negative muon-induced MCUs, which are caused by secondary ions generated through muon capture process, were recently reported. Neutron- and negative muon-induced MCUs are both caused by secondary ions, and hence, they are expected to have some similarity. In this paper, we compare negative muon- and neutron-induced MCUs in 65-nm bulk SRAMs at the irradiation experiments using spallation and quasi-monoenergetic neutrons and monoenergetic negative muons. The measurement results show that the dependencies of MCU event cross section on operating voltage are almost identical. The high operating voltage makes both negative muon- and neutron-induced MCU cross sections larger due to parasitic bipolar action. Consequently, large-bit MCUs are observed under the irradiation using both neutrons and muons. On the other hand, at 0.4 V, neutrons induce larger-bit MCUs (> 12 bits) whereas negative muons cause up to 11-bit MCUs. Upsets of 3 or larger bits along word line (WL) are observed at spallation neutron beams. To explain the similarity of MCUs induced by neutrons and negative muons, the Monte Carlo simulation is conducted to investigate the deposited charge. The distributions of deposited charge obtained by the simulation are consistent with the above-mentioned experimental observations.

Thermal power from radioactive decay (‘decay heat’) in an ISIS proton-driven spallation neutron target has been measured in a carefully controlled and consistent way as a function of cooling time between 1 minute and 2 weeks. Overall, results are in good agreement with calculations made with the Monte Carlo program MCNPX.

In an accelerator driven critical or sub-critical system (ADS), a spallation target is irradiated by high-power proton beam to drive a reactor. To continuously produce very intense neutrons, it is very important to ensure that the target operates in a setting temperature environment. This paper reports several techniques of temperature control for the spallation target in China initiative ADS system, where tungsten granules in the target container are used as both coolant and target materials. In order to avoid high temperatures at the target center due to the Gaussian distribution of beam intensity, the proton beam should be scanned on the surface of the target to provide a high degree of uniformity in energy deposition. The target temperature can be controlled by adjusting automatically the speed of the coolant. If the speed attains the maximum setting value, the beam intensity will be decreased for a given value to reduce the heat generation. To evaluate the proposed control techniques, the heat transfer model of particles has been employed to investigate the spatio-temporal variations of the target temperatures. The simulation results indicate that the beam scanning technique reduces dramatically the temperatures. The target temperatures can be controlled by adjusting automatically both the granular speed and the beam intensity. The target can operate normally in the setting working temperature range even if the target is irradiated by the proton beam with the maximum power.

We have performed extensive testing and qualification of different commercial fast neutron scintillator screens in camera-based imaging detectors. These include organic scintillators and a ZnS:Cu scintillator mixed in a polypropylene (PP) matrix. Furthermore, we have developed simple and inexpensive in-house ZnS-based fast neutron imaging screens and their performance has been tested and compared to the aforementioned commercial ones. Furthermore, ZnS:Ag was mixed with high viscosity glycerol to create suspension type imaging screen. The ZnS concentration and the screen thickness have been optimized experimentally using sample screen pieces. The screens have been tested in spallation and fission spectra. The plastic scintillator performed the worst mainly due to its low light output, while the PP/ZnS screen the best. The in-house ZnS–epoxy screens produced about 60% of light intensity of its commercial counterpart, which is mainly due to the lower hydrogen density of the optical epoxy compared to polypropylene. A simple model of the converter/ZnS screen type was developed to help understand its properties and to optimize its performance. Some fast neutron radiographic images are shown to illustrate the capabilities of the screens.

The Rapid Cycling Synchrotron (RCS) of the China Spallation Neutron Source (CSNS) accelerates beam from 80 MeV to 1.6 GeV to strike a solid metal target to produce spallation neutrons with a repetition rate of 25 Hz. In this kind of high bunch intensity synchrotrons, to suppress the space-charge effect, the large acceptance is always required. For CSNS, with the design acceptance of 540 π mm ⋅ mrad, the apertures of quadrupoles are quite large, which are comparable to the effective magnet lengths. In this case, the fringe field effect cannot be neglected. For some quadrupoles, the interval between the quadrupole and its neighbor magnet is comparable to the aperture of quadrupole, and the effect of field interference need to be considered. The fringe field and field interference effects have been studied, and by including these effects, the lattice was re-matched based on slicing model of quadrupoles to include these effects. After the re-matched lattice was applied to the beam commissioning of the RCS of CSNS, the measured twiss parameters are very close to the design parameters.

ESS, the European Spallation Source, will adopt a single family of double spoke cavities for accelerating the beam from the normal conducting section to the first family of the elliptical superconducting cavities. It will be the first double spoke cavities in the world to be commissioned for a high power proton accelerator. The first double spoke cavity for the ESS project was tested with high power in the HNOSS cryostat at Uppsala University. A pulse-mode test stand based on a self-excited loop was used in this test. The qualification of the cavity package involves a double-spoke superconducting cavity, a fixed fundamental power coupler, tuner, a low-level radiofrequency (LLRF) system and a high-power radiofrequency (RF) station. The test represents an important verification milestone before the module assembly. This cavity had unfortunately a high dynamic loss of 12 W @ 9 MV/m, where potential causes for such a high value have been studied and corresponding suggestions are listed. This paper presents the test configuration, RF conditioning history, first high power performance and experience of this cavity package.

In search to identify extremely stable materials to perform the collimation function of the 7-TeV proton beam halo at the Large Hadron Collider (LHC), oxide dispersion strengthened (DS) copper alloys were explored. These internally oxidized copper alloys known as GlidCop are also leading candidates for high heat flux applications in fusion reactors and as divertor and first wall structure in ITER. These considerations have led to an extensive body of research on neutron-induced changes in the microstructure and physio-mechanical properties. This study focused primarily on the damage induced by 200 MeV protons on as wrought and cold-worked GlidCop Al15 DS copper ally selected as a candidate material of the LHC beam collimation structure to damage levels up to ∼10 displacements-per-atom (dpa) and irradiation temperatures up to ∼600 °C. For reference, low dose spallation neutron damage at sub-zero irradiation temperature was included in the study. Proton irradiation effects on dimensional stability, mechanical behavior, electrical resistivity and X-ray diffraction-based microstructural changes are presented in the paper. GlidCop Al15 exhibited excellent thermal stability and superior to pure Cu resistance to conductivity loss. Proton irradiation-induced hardening and embrittlement at distinct irradiation temperature regimes were shown to follow similar trends to what was reported under neutron exposure to even higher dpa damage. At T$_{\tt{irr}}$ ∼600 ± 20 °C the cold-worked DS copper alloy exhibited softening accompanied by elongation reduction while at T$_{\tt{irr}}$ ∼200 ± 10 °C the as-wrought experienced hardening with elongation increase. High resolution X-ray diffraction revealed that even low-dose neutron irradiation has a strong influence on the size and distribution of dispersed Al$_2$O$_3$ particles.

The 6th SINQ Target Irradiation Program (STIP VI) was conducted in SINQ Target 9 during 2011 and 2012. A radiation damage assessment based on a simulation using the MCNPX code was performed to obtain the irradiation parameters of displacement damage, helium and hydrogen concentrations in each specimen rod placed in the target. The gamma mapping performed on the proton beam entrance window after irradiation provided the proton fluence distribution used for implementing the source definition in the simulation. The proton and neutron fluences along the target as well as the energy deposition were calculated. Corresponding to the average beam current of 1.42 mA, the maximum neutron flux obtained is 5.95 × 1014 n/(cm2 ⋅ s) and the maximum energy deposition in the Zircaloy-2 cladding tubes is 568 W/cm3 . The irradiation parameters of selected materials in each specimen rod were calculated by multiplying the proton and neutron fluences with the corresponding cross section data. The maximum displacement damage was obtained for Zircaloy-2 in Row 2 with a value of 72.1 dpa (displacement per atom). The maximum helium concentration was obtained for tantalum in Row 1 with a value of 3630 appm and the maximum hydrogen concentration was obtained for tungsten in Row 1 with a value of 17590 appm. All these values are the highest for the corresponding materials ever reached in a spallation target irradiation environment. The helium concentrations are also the highest ever obtained in bulk specimens.

In this work, 3-point bending tests and micro-hardness measurements were performed on pure tungsten irradiated with high-energy protons and spallation neutrons in a target of the Swiss Spallation Neutron Source (SINQ). The specimens were irradiated to doses in the range of 1.3–3.5 dpa, with 37–140 appm He, at temperatures between 75 and 110 °C. During 3-point bending tests performed at temperatures up to 500 °C, all the irradiated specimens fractured in the elastic regime at stresses much below those for the unirradiated reference specimens. The micro-hardness measurements indicate significant irradiation induced hardening under all irradiation conditions. Observation of the fracture surfaces of tested irradiated specimens shows brittle fracture behaviour in general, whereas detailed features depend strongly on irradiation dose and test temperature.

Thirty-three years of operational history of the accelerator and target aspects of the ISIS Spallation Neutron and Muon Source are summarised. Data on overall percentages of lost time and distributions of lost time amongst different equipment categories are presented. Areas of difficulty are also described, along with measures taken to overcome the difficulties. Further, on the basis of hard-won experience, recommendations for managing operations are made. Altogether, much valuable operational information spanning several decades is presented, and this should be of interest to designers and operators of large accelerator-based facilities.

The concept of gravity-driven Dense Granular Target (DGT) has been proposed and tungsten granule is one of the candidate target materials. With the increase of DGT diameter, the source efficiency is significantly reduced, which is not conducive to the design of high-power. Low density porous tungsten particles are proposed as the target material of DGT instead of the natural tungsten. First, the neutronics of the bare target have been studied with porous tungsten granule density using Monte Carlo code. An ADS model was then set up to evaluate the neutron sources performance caused by density variation of porous tungsten granule. The results show that there is an optimal combination of tungsten granular density and target diameter to make the utmost of leakage neutrons. In the ADS driven by tungsten DGT, an appropriate density porous tungsten as the target material can effectively increase the source efficiency, reduce the beam requirement and the thermal deposition on the target.

The spallation material at ESS is pure tungsten, which is cooled by gaseous helium flow. To study the behaviour of tungsten under dynamic beam conditions at ESS, pure tungsten specimens have been i ...

The fixed-energy window scan approach, for both elastic and inelastic modes, is a valuable tool to discriminate between motions activated when dynamical phase transitions occur in a sample as a function of time, temperature, pressure, electrical field or illumination. Considering that, on one hand, such variations can generate a weak signal, and on the other, high data throughput makes it possible to screen many samples during a beam time, pulse multiplication is an ideal strategy to optimize the intensity of the analyzed signal. To ensure this capability, a proposal for a future upgrade of MIRACLES, the neutron time-of-flight backscattering spectrometer at the European Spallation Source (ESS) under construction in Lund, is reported in this article. The concept for a new chopper layout relies on the extraction of several elastic pulses, ensuring an increase in the neutron total elastic intensity hitting the sample. This proposal can be extended to the inelastic counterpart. The premise is to maintain the original beamline layout without modification, either of the guide sections or of the current chopper layout of MIRACLES, thereby guaranteeing that minimal changes and impact will occur during the proposed upgrade. However, this also presents a significant challenge, namely, to achieve an efficient pulse multiplication within the width and the length of the guide and within the rising/decay time of the pulses. With the concept presented here, an increase in elastic intensity by a factor of 2.8 was obtained. This is analogous to performing elastic fixed window (EFW) measurements with an ESS source operating at 14 MW, widening considerably the performance capabilities of MIRACLES. The knowledge generated here is also valuable for the design of scientific instruments for the next generation of low-energy, accelerator-driven neutron sources.

Low Energy accelerator-driven Neutron Facilities have the potential to become competitive to research reactors and spallation sources to generate neutron beams for scattering experiments. A low energy accelerator-driven neutron facility is developed at the Julich Centre for Neutron Science. This source is expected to provide thermal and cold neutrons with high brilliance and is therefore called “High Brilliance neutron Source” (HBS). In this work, we study the performance of neutron guide systems at HBS by using neutron ray-tracing simulations. Elliptical and ballistic guides with elliptic diverging/converging section have been used in simulations for various moderator-to-guide distances and guide entrance cross-sections. Results show that the beam properties have a strong dependence on the distance between guide entry and moderator. We demonstrate that the ballistic guide system can achieve a comparable neutron flux and brilliance transfer as the true elliptical guide for thermal neutrons if a proper distance between guide entrance and moderator is chosen. For low-divergence cold neutrons, the selected ballistic guide is showing even better performance than the elliptical one.

Transport calculations for neutronic design require accurate nuclear data and validated computational tools. In the Spallation Physics Group, at the European Spallation Source, we perform shielding and neutron beam calculations to help the deployment of the instrument suite for the current high brilliance (top) moderator, as well for the design of the high intensity bottom moderator, currently under study for the facility. This work includes providing the best available nuclear data in addition to improving models and tools when necessary. In this paper we present the status of these activities, which include a set of thermal scattering kernels for moderator, reflector, and structural materials, the development of new kernels for beryllium considering crystallite size effects, nanodiamonds, liquid hydrogen and deuterium based on path integral molecular dynamics, and the use of the software package NCrystal to assist the development of nuclear data in the framework of the new HighNESS project., Comment: UCANS-Web 2020

Back-streaming neutrons from the spallation target of the China Spallation Neutron Source (CSNS) that emit through the incoming proton channel were exploited to build a white neutron beam facility (the so-called Back-n white neutron source), which was completed in March 2018. The Back-n neutron beam is very intense, at approximately 2*10^7 n/cm^2/s at 55 m from the target, and has a nominal proton beam with a power of 100 kW in the CSNS-I phase and a kinetic energy of 1.6 GeV and a thick tungsten target in multiple slices with modest moderation from the cooling water through the slices. In addition, the excellent energy spectrum spanning from 0.5 eV to 200 MeV, and a good time resolution related to the time-of-flight measurements make it a typical white neutron source for nuclear data measurements; its overall performance is among that of the best white neutron sources in the world. Equipped with advanced spectrometers, detectors, and application utilities, the Back-n facility can serve wide applications, with a focus on neutron-induced cross-section measurements. This article presents an overview of the neutron beam characteristics, the experimental setups, and the ongoing applications at Back-n., Comment: 11 pages, 9 figures

We model the effect of ground movement, based on empirical experience, on the transport properties of long neutron guides by ray-tracing simulations. Our results reproduce the large losses found by an earlier study for a simple model, while for a more realistic engineering model of guide mounting, we find the losses to be significantly smaller than earlier predicted. A detailed study of the guide for the cold neutron spectrometer BIFROST at the European Spallation Source shows that the loss is 7.0(5) % for wavelengths of 2.3-4.0 {\AA}; the typical operational wavelength range of the instrument. This amount of loss does not call for mitigation by overillumination as suggested in the previous work. Our work serves to quantify the robustness of the transport properties of long neutron guides, in construction or planning at neutron facilities worldwide., Comment: 8 pages, 12 figures

Coherent Elastic neutrino-Nucleus Scattering (CEνNS), a process recently measured for the first time at ORNL’s Spallation Neutron Source, is directly sensitive to the weak form factor of the nucleus. The European Spallation Source (ESS), presently under construction, will generate the most intense pulsed neutrino flux suitable for the detection of CEνNS. In this paper we quantify its potential to determine the root mean square radius of the point-neutron distribution, for a variety of target nuclei and a suite of detectors. To put our results in context we also derive, for the first time, a constraint on this parameter from the analysis of the energy and timing data of the CsI detector at the COHERENT experiment., This work was supported by the MINECO grants FPA2016-76005-C2-1-P and FIS2017-87534-P, by the MINECO FEDER/UE grants FPA2015-65929-P, FPA2016-78645-P and FPA2017-85985-P, by PROMETEO/2019/083, by U.S.A.-NSF grants PHY-1620628, by AGAUR (Generalitat de Catalunya) grant 2017-SGR-929, and by the European ITN project HiDDeN (H2020-MSCA-ITN-2019//860881-HIDDeN). IE acknowledges support from the FPU program fellowship FPU15/0369. PC and JM acknowledge support from the Spanish MICINN through the \Ramón y Cajal" program with grants RYC2018-024240- I (PC) and RYC-2017-22781 (JM). The authors acknowledge the support of the Spanish Agencia Estatal de Investigacion through the grant \IFT Centro de Excelencia Severo Ochoa SEV-2016-0597".

Six cylindrical lead bismuth eutectic (LBE) targets having fixed diameter of 6 mm and varying lengths of 8–50 mm were irradiated with a 1.4 GeV proton beam at CERN-ISOLDE. Both short-lived ( $$5\hbox { h } {}5\hbox { days}$$ ) radionuclides were identified by off-line $$\upgamma $$ -spectrometry and their activities at the end of bombardment (EOB) were determined. Total 80 $$\upgamma $$ -emitting radionuclides, ranging from $$^{7}\hbox {Be}$$ to $$^{209}\hbox {At}$$ , were identified in the 50 mm long LBE target. The yields of all the radioisotopes were compared with the Monte Carlo Code FLUKA. The spallation reaction was the dominant mode whereas fission induced reactions had no significant contribution. The high energy proton irradiated LBE target may act as a large source of several clinically important and other exotic radionuclides.

The isotope used in this research was supplied by the United States Department of Energy Office of Science by the Isotope Program in the Office of Nuclear Physics., The neutron capture cross section of 154Gd was measured from 1 eV to 300 keV in the experimental area located 185 m from the CERN n_TOF neutron spallation source, using a metallic sample of gadolinium, enriched to 67% in 154Gd. The capture measurement, performed with four C6D6 scintillation detectors, has been complemented by a transmission measurement performed at the GELINA time-of-flight facility (JRC-Geel), thus minimising the uncertainty related to sample composition. An accurate Maxwellian averaged capture cross section (MACS) was deduced over the temperature range of interest for s process nucleosynthesis modelling. We report a value of 880(50) mb for the MACS at kT = 30 keV, significantly lower compared to values available in literature. The new adopted 154Gd(n,γ ) cross section reduces the discrepancy between observed and calculated solar s-only isotopic abundances predicted by s-process nucleosynthesis models., EUFRAT open access programme of the Joint Research Centre at Geel

The European Spallation Source (ESS), presently well on its way to completion, will soon provide the most intense neutron beams for multi-disciplinary science. Fortuitously, it will also generate the largest pulsed neutrino flux suitable for the detection of Coherent Elastic Neutrino-Nucleus Scattering (CE$\nu$NS), a process recently measured for the first time at ORNL's Spallation Neutron Source. We describe innovative detector technologies maximally able to profit from the order-of-magnitude increase in neutrino flux provided by the ESS, along with their sensitivity to a rich particle physics phenomenology accessible through high-statistics, precision CE$\nu$NS measurements., Comment: 21 pages, 15 figures. v2: Minor changes, typo corrected in Fig 6. Version accepted for publication in JHEP

The transport of neutrons in long beamlines at spallation neutron sources presents a unique challenge for Monte-Carlo transport calculations. This is due to the need to accurately model the deep-penetration of high-energy neutrons through meters of thick dense shields close to the source and at the same time to model the transport of low-energy neutrons across distances up to around 150 m in length. Typically, such types of calculations may be carried out with MCNP-based codes or alternatively PHITS. However, in recent years there has been an increased interest in the suitability of Geant4 for such types of calculations. Therefore, we have implemented supermirror physics, a neutron chopper module and the duct-source variance reduction technique for low-energy neutron transport from the PHITS Monte-Carlo code into Geant4. In the current work, we present a series of benchmarks of these extensions with the PHITS software, which demonstrates the suitability of Geant4 for simulating long neutron beamlines at a spallation neutron source, such as the European Spallation Source, currently under construction in Lund, Sweden., ICANS-XXIII

Fast neutron measurements have been performed with silicon and diamond detectors at nTOF, ChipIr, and CHARM facilities. The detectors have been used in pulse mode; the deposited energy and time stamp is measured event by event for each signal above threshold. The pulsed nature of the spallation sources gives high instantaneous counting rates that dictate the use of a fast electronic chain including a current preamplifier and digital acquisition. The energy-dependent response functions of these detectors to fast neutrons can be extracted from nTOF data using time-of-flight to provide energy tagging. These measured response functions can then be used both to benchmark Monte Carlo simulations of the response functions and to interpret the measurements at ChipIR and CHARM, facilities used for the irradiation of microelectronics, where time-of-flight energy measurement at these neutron energies is not possible.

To provide essential beam diagnostics for the spallation target and for the tuning dump of the European Spallation Source (ESS) with its high-power, low-emittance proton beam, optical imaging systems have been developed allowing remote viewing of the beam profiles, using scintillation light from coatings on the proton beam window (PBW) at the accelerator exit and the target entry window (TW), and insertable interceptive screens at the tuning dump (TD). In this paper, we present the techniques used and the main parameters in the design of the TD system, including the optical configurations modelled in the software Zemax OpticStudio (ZOS). We also present the design principles for reflective optics which can transmit high-quality images, showing the performance of the imaging systems as predicted by ZOS and by prototyping. We take account of the requirements for initial alignment and ongoing maintenance of the optical system. Studies of the radiation and thermal environments, which impact on sensitive optical components such as cameras and mirrors, are also described, as are mechanical considerations for the vacuum vessels and screen actuators. Finally, comments are made on the applicability of similar optics to diagnostic systems at other neutron sources and accelerators.

Fragments productions in spallation reactions are key infrastructure data for various applications. Based on the empirical parameterizations {\sc spacs}, a Bayesian-neural-network (BNN) approach is established to predict the fragment cross sections in the proton induced spallation reactions. A systematic investigation have been performed for the measured proton induced spallation reactions of systems ranging from the intermediate to the heavy nuclei and the incident energy ranging from 168 MeV/u to 1500 MeV/u. By learning the residuals between the experimental measurements and the {\sc spacs} predictions, the BNN predicted results are in good agreement with the measured results. The established method is suggested to benefit the related researches in the nuclear astrophysics, nuclear radioactive beam source, accelerator driven systems, and proton therapy, etc., Comment: 7 figures, accepted by Chinese Physics C