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Objective. This work aims to develop a graphics processing unit (GPU)-accelerated Monte Carlo code for the coupled transport of photon, electron/positron and neutron over a broad range of energies for medical applications. Approach. By separating the MC evolution of radiation into source, transport, and interaction kernels, the branch divergence was alleviated. The memory coalescence was achieved by vectorizing the access pattern in which the secondary particles were archived. To accelerate further particle tracking, ray-tracing hardware acceleration in the Nvidia OptiXTM framework was applied. For photon and electron/positron, the EGSnrc interaction modules were ported as a GPU-optimized configuration. For neutron, a group-wised transport based on NJOY21 preprocessed data was implemented. The developed code was validated against CPU-based FLUKA. Neutron, x-ray and electron beams incident on water and ICRP phantoms were simulated. The neutron energy group and the transport parameters of photon and electron were set to be the same in both codes. A single Nvidia RTX 4090 card was used in this code while all 20 threads of a single Intel Core i9-10900K node were used in FLUKA. Main results. The number of histories was set to ensure that statistical uncertainties lower than 2% for all voxels whose doses were larger than 20% of the maximum. In all cases, the dose differences in the voxels between the codes were within 2.5%. For photons and electrons, the developed code was 150 – 300 times faster than FLUKA in both geometries. For neutrons, the code was respectively 80 and 135 times faster in the water and ICRP phantoms than FLUKA. Significance. This study offers an appropriate solution for uncoalesced memory access and branch divergence commonly encountered in coupled MC transport on the GPU architecture. The formidable acceleration in computing times and accuracy shown in this study can promise a routine clinical use of MC simulations. [ABSTRACT FROM AUTHOR]

Deuterium-tritium fusion reactions produce energy in the form of 14.1 MeV neutrons, and hence fusion reactor components will be exposed to high energy neutron irradiation while also being subjected to thermal, mechanical and magnetic loads. Exposure to neutron irradiation has numerous consequences, including swelling and dimensional changes, comparable in magnitude to the peak transient thermal deformations occurring in plasma-facing components. Irradiation also dynamically alters the various thermo-mechanical properties, relating temperature, stress and swelling in a strongly non-linear way. Experimental data on the effect of neutron exposure spanning the design parameter space are very sparse and this highlights the relevance of computer simulations. In this study we explore the equivalence between the body force/surface traction approach and the eigenstrain formalism for treating anisotropic irradiation-induced swelling. We find that both commercial and massively parallelised open source software for finite element method (FEM) simulations are suitable for assessing the effect of neutron exposure on the mechanically loaded reactor components. We demonstrate how two primary effects of irradiation, radiation swelling and the degradation of thermal conductivity, affect the distributions of stress and temperature in the divertor of the ITER tokamak. Significant uncertainties characterising the magnitude of swelling and models for treating it suggest that on the basis of the presently available data, only an order of magnitude estimate can be given to the stress developing in reactor components most exposed to irradiation during service. [ABSTRACT FROM AUTHOR]

For the problem of two or more nuclear reactions producing the same product nucleus in the actual cross-section measurements of nuclear reactions, a method is given for subtracting the effect of interference reactions that produce the same product nucleus on the cross-section measurements of the target nuclear reaction. The cross-section values were measured for the 183W(n,p)183Ta reaction at four different neutron energies from 13.5 to 14.8 MeV using the activation technique. In the process of calculating the cross-section data, the effects of the interference reactions 184W(n,d)183Ta and 184W(n,n+p)183Ta were subtracted using the above method. At the same time, the effect of the 186W(n, α)183Hf → β − 183Ta process was also subtracted by using the previously developed method. Analysis and comparison show that our experimental cross-section values for the 183W(n,p)183Ta reaction agree with the previous results in the case of using the samples of enriched 183W at close energies. Discrepancies in the previous cross-section data of the 183W(n,p)183Ta reaction are clarified, and the recommendation excitation function curve for the 183W(n,p)183Ta reaction is given by adopting the nuclear theoretical model program system TALYS-1.95. [ABSTRACT FROM AUTHOR]

Fast ions in the MeV-range can be diagnosed by neutron emission spectroscopy (NES) and gamma-ray spectroscopy (GRS). In this work, we present orbit weight functions for one-step fusion reactions, using NES and GRS diagnostics on perpendicular and oblique lines-of-sight (LOS) at Joint European Torus (JET) as examples. The orbit weight functions allow us to express the sensitivities of the diagnostics in terms of fast-ion (FI) orbits and can be used to swiftly reproduce synthetic signals that have been computed by established codes. For diagnostically relevant neutron energies for the D(D, n)3He reaction, the orbit sensitivities of the NES diagnostics follow a predictable pattern. As the neutron energy of interest increases, the pattern shifts upwards in FI energy. For the GRS diagnostic and the T(p, Îł)4He reaction, the orbit sensitivity is shown to be qualitatively different for red-shifted, blue-shifted and nominal gamma birth energies. Finally, we demonstrate how orbit weight functions can be used to decompose diagnostic signals into the contributions from different orbit types. For a TRANSP simulation of the JET discharge (a three-ion ICRF scenario) considered in this work, the NES signals for both the perpendicular and oblique LOS are shown to originate mostly from co-passing orbits. In addition, a significant fraction of the NES signal for the oblique LOS is shown to originate from stagnation orbits. [ABSTRACT FROM AUTHOR]

The emission of Be, C, O, and Ne clusters from seven parent nuclei with neutron numbers around the neutron magicities N = 82 and 126 are considered. The universal decay law (UDL) formula, as well as the double-folding model derived from the Michigan three-range Yukawaâ€"Paris NN interaction with zero- and finite-range exchange components, are utilized to compute the half-life time for 23 cluster decay processes. The calculations utilizing the UDL formula show satisfactory agreement with the experimental data. The reliable UDL formula is used to calculate log  T c for more than 1500 cluster emitters and its variation with the neutron number, N d, of the daughter nuclei is presented. The behavior of log  T c with neutron number variation is studied and correlated to the energy levels of the daughter nuclei. For a neutron number N d larger than the neutron magic number, log  T c increases almost linearly with increasing N d, leaving the daughter nuclei in most cases with the same nuclear spin value. This linear behavior of log  T c results from equal nuclear spin values of the daughter nuclei. At the magic neutron number, the nuclear spin changes strongly and as a result log  T c increases as N d decreases. Log T c reaches to a maximum value when all the neutrons in the cluster are emitted from levels below the neutron gap. Leaving the daughter nuclei in the same spin produces almost linear variation of log  T c. For protons in various clusters emitted from the same level or the same group of levels, log  T c has almost the same value and the same behavior of variation with N d. Also, the values of log  T c for specific types of cluster depend on the N to Z ratio for different isotopes of this cluster. From the available nuclear spin values, the neutron energy levels around the magic numbers are presented. [ABSTRACT FROM AUTHOR]

A time-of-flight polarized neutron imaging setup was realized by integrating an in situ pumped polarized 3He spin filter and energy dispersive neutron camera on the neutron technique development beamline (BL-20) of the China Spallation Neutron Source (CSNS). Test experiments were performed with a solenoid with aluminum wire as a sample. These demonstrated that polarized radiography with a field of view in diameter 2.0 cm at different wavelengths can be obtained. The wavelength-dependent polarization was used to distinguish the neutron polarization behavior for different positions inside and outside the solenoid. The results of this work show the possibility of applying the technique at CSNS and marks a milestone for future polarized neutron imaging developments. [ABSTRACT FROM AUTHOR]

Neutron beams have been providing indispensable tools for a wide range of fields in modern science and engineering. Recently, a new type of pulsed neutron source has been developed, known as laser-driven neutron source (LDNS). The LDNSs utilize laser-accelerated ions, including protons and deuterons as a primary beam and generate neutrons from a secondary target (lithium, beryllium, etc) via a nuclear reaction. Applying an additional moderator part, LDNSs can provide a broad energy range of neutrons (meV ∼ MeV). This paper aims to introduce the current status of LDNS and the results of application-oriented experiments implemented at the Institute of Laser Engineering (ILE) of Japan. [ABSTRACT FROM AUTHOR]

Objective. The purpose of this study is to estimate the energy and angular distribution of secondary neutrons inside a phantom in hadron therapy, which will support decisions on detector choice and experimental setup design for in-phantom secondary neutron measurements. Approach. Dedicated Monte Carlo simulations were implemented, considering clinically relevant energies of protons, helium and carbon ions. Since scored quantities can vary from different radiation transport models, the codes FLUKA, TOPAS and MCNP were used. The geometry of an active scanning beam delivery system for heavy ion treatment was implemented, and simulations of pristine and spread-out Bragg peaks were carried out. Previous studies, focused on specific ion types or single energies, are qualitatively in agreement with the obtained results. Main results. The secondary neutrons energy distributions present a continuous spectrum with two peaks, one centred on the thermal/epithermal region, and one on the high-energy region, with the most probable energy ranging from 19 up to 240 MeV, depending on the ion type and its initial energy. The simulations show that the secondary neutron energies may exceed 400 MeV and, therefore, suitable neutron detectors for this energy range shall be needed. Additionally, the angular distribution of the low energy neutrons is quite isotropic, whereas the fast/relativistic neutrons are mainly scattered in the down-stream direction. Significance. It would be possible to minimize the influence of the heavy ions when measuring the neutron-generated recoil protons by selecting appropriate measurement positions within the phantom. Although there are discrepancies among the three Monte Carlo codes, the results agree qualitatively and in order of magnitude, being sufficient to support further investigations with the ultimate goal of mapping the secondary neutron doses both in- and out-of-field in hadrontherapy. The obtained secondary neutron spectra are available as supplementary material. [ABSTRACT FROM AUTHOR]

Using the notion of eigenstrain produced by the defects formed in a material exposed to high energy neutron irradiation, we develop a method for computing macroscopic elastic stress and strain arising in components of a fusion power plant during operation. In a microstructurally isotropic material, the primary cause of macroscopic elastic stress and strain fields is the spatial variation of neutron exposure. We show that under traction-free boundary conditions, the volume-average elastic stress always vanishes, signifying the formation of a spatially heterogeneous stress state, combining compressive and tensile elastic deformations at different locations in the same component, and resulting solely from the spatial variation of radiation exposure. Several case studies pertinent to the design of a fusion power plant are analysed analytically and numerically, showing that a spatially varying distribution of defects produces significant elastic stresses in ion-irradiated thin films, pressurised cylindrical tubes and breeding blanket modules. [ABSTRACT FROM AUTHOR]

The impact of quadrupole and octupole collectivity in the dynamic of low-lying collective states is discussed for a set of Xe, Ba, Ce and Nd isotopes with neutron numbers 54 â©˝ N â©˝ 96. Mean field based methods including pairing are used in our microscopic description along with the Gogny D1M force. Starting with a set of Hartreeâ€"Fockâ€"Bogoliubov constrained states we consider dynamic fluctuations of the collective variables by using the generator coordinate method. Related quantities like reduced electromagnetic transition probabilities B (E 1) and B (E 3) and negative-parity excitation energies and their behavior with neutron number are discussed and compared with the available experimental data. The coupling between the quadrupole and octupole degrees of freedom is found to be rather weak in all the considered nuclei and therefore the properties of the negative parity states can be reasonably well described in terms of the octupole degree of freedom alone. The results of the calculations point towards dynamically enhanced octupole correlations around the ‘octupole magic’ neutron numbers N = 56 and N = 88. [ABSTRACT FROM AUTHOR]

Dose equivalent limits for single organs are recommended by the ICRP (International Commission for the Radiological Protection publication 103). These limits do not lend themselves to be measured. They are assessed by convoluting conversion factors with particle fluences. The Fluence-to-Dose conversion factors are tabulated in the ICRP literature. They allow assessing the organ dose of interest using numerical simulations. In particular, the literature lacks the knowledge of local skin equivalent dose (LSD) coefficients for neutrons. In this article, we compute such values for neutron energies ranging from 1 meV to 15 MeV. We use FLUKA, MCNP and GEANT4 Radiation transport Monte-Carlo simulation codes to perform the calculations. A comparison between these three codes is performed. These calculated values are important for radiation protection studies and radiotherapy applications. [ABSTRACT FROM AUTHOR]

Time-of-flight (ToF) neutron imaging offers complementary attenuation contrast to x-ray computed tomography, coupled with the ability to extract additional information from the variation in attenuation as a function of neutron energy (ToF) at every point (voxel) in the image. In particular, Bragg edge positions provide crystallographic information and therefore enable the identification of crystalline phases directly. Here we demonstrate Bragg edge tomography with high spatial and spectral resolution. We propose a new iterative tomographic reconstruction method with a tailored regularisation term to achieve high quality reconstruction from low-count data, where conventional filtered back-projection (FBP) fails. The regularisation acts in a separated mode for spatial and spectral dimensions and favours characteristic piece-wise constant and piece-wise smooth behaviour in the respective dimensions. The proposed method is compared against FBP and a state-of-the-art regulariser for multi-channel tomography on a multi-material phantom. The proposed new regulariser which accommodates specific image properties outperforms both conventional and state-of-the-art methods and therefore facilitates Bragg edge fitting at the voxel level. The proposed method requires significantly shorter exposures to retrieve features of interest. This in turn facilitates more efficient usage of expensive neutron beamline time and enables the full utilisation of state-of-the-art high resolution detectors. [ABSTRACT FROM AUTHOR]

A pulsed DD neutron generator based on the plasma focus (PF) device has been developed. The PF device was assembled using a single energy storage capacitor (10 µF) and a triggerable spark gap switch in a compact geometry. The anode of the PF device was made of SS304 material with its tip modified using a high purity tungsten insert. Excluding the power supply, the size of the overall system was 0.6 × 0.6 × 1.0 m and the weight was less than 100 kg. A maximum DD neutron yield of (3.1 ± 0.2) × 108 neutrons/pulse and average DD neutron yield of (2.24 ± 0.16) × 108 neutrons/pulse (pulse duration = 35 ± 4 ns) into 4π sr were observed at a capacitor bank energy of 3.1 kJ (25 kV) and at 4.5 mbar D2 gas filling pressure. The experimentally observed average neutron yield was found to be around 30% more than the estimated yield obtained using scaling laws for neutrons (Yn ≈ 1.7 × 10−10I03.3; I0 is the peak discharge current in A). For a peak discharge current of 258 kA at 3.1 kJ, the neutron yield was estimated to be 1.23 × 108 neutrons/pulse. The higher neutron production was attributed to the efficient design of the PF device as well as to the low erosion of the anode tip because of the tungsten insert. Using the time-of-flight method, maximum neutron energy was calculated to be 3.91 ± 0.16 MeV in the radial direction at 4.5 mbar filling pressure. Numerical parametrization using the five-phase Lee model code was performed and found to be similar to PF devices developed across the world. [ABSTRACT FROM AUTHOR]

Three-dimensional integrated circuits (3D ICs) have entered into the mainstream due to their high performance, high integration, and low power consumption. When used in atmospheric environments, 3D ICs are irradiated inevitably by neutrons. In this paper, a 3D die-stacked SRAM device is constructed based on a real planar SRAM device. Then, the single event upsets (SEUs) caused by neutrons with different energies are studied by the Monte Carlo method. The SEU cross-sections for each die and for the whole three-layer die-stacked SRAM device is obtained for neutrons with energy ranging from 1 MeV to 1000 MeV. The results indicate that the variation trend of the SEU cross-section for every single die and for the entire die-stacked device is consistent, but the specific values are different. The SEU cross-section is shown to be dependent on the threshold of linear energy transfer (LETth) and thickness of the sensitive volume (Tsv). The secondary particle distribution and energy deposition are analyzed, and the internal mechanism that is responsible for this difference is illustrated. Besides, the ratio and patterns of multiple bit upset (MBU) caused by neutrons with different energies are also presented. This work is helpful for the aerospace IC designers to understand the SEU mechanism of 3D ICs caused by neutrons irradiation. [ABSTRACT FROM AUTHOR]

The boron-10 based multi-grid detector is being developed as an alternative to helium-3 based neutron detectors. At the European Spallation Source, the detector will be used for time-of-flight neutron spectroscopy at cold to thermal neutron energies. The objective of this work is to investigate fine time- and energy-resolved effects of the Multi-Grid detector, down to a few µeV, while comparing it to the performance of a typical helium-3 tube. Furthermore, it is to characterize differences between the detector technologies in terms of internal scattering, as well as the time reconstruction of ∼ µs short neutron pulses. The data were taken at the Helmholtz Zentrum Berlin, where the Multi-Grid detector and a helium-3 tube were installed at the ESS test beamline, V20. Using a Fermi-chopper, the neutron beam of the reactor was chopped into a few tens of µs wide pulses before reaching the detector, located a few tens of cm downstream. The data of the measurements show an agreement between the derived and calculated neutron detection efficiency curve. The data also provide fine details on the effect of internal scattering, and how it can be reduced. For the first time, the chopper resolution was comparable to the timing resolution of the Multi-Grid detector. This allowed a detailed study of time- and energy resolved effects, as well as a comparison with a typical helium-3 tube. [ABSTRACT FROM AUTHOR]

A practical neutron energy dependent RBE model has been developed, based on the relationship between a mono-energetic neutron energy and its likely recoil proton energy. Essentially, the linear energy transfer (LET) values of the most appropriate recoil proton energies are then used to modify the linear quadratic model radiosensitivities (α and β) from their reference LET radiation values to provide the RBE estimates. Experimental neutron studies published by Hall (including some mono-energetic beams ranging from 0.2 to 15 MeV), Broerse, Berry, and data from the Clatterbridge and Detroit clinical neutron beams, which all contain some data from a spectrum of neutron energies, are used to derive single effective neutron energies (NEeff) for each spectral beam. These energies yield a recoil proton spectrum, but with an effective mean proton energy (being around 50% of NEeff). The fractional increase in LET is given by the recoil proton LET divided by the proton (LETU) value which provides the highest RBE. This ratio is then used to determine the change in the linear-quadratic model α and β parameters, from those of the reference radiation, to estimate the RBE. The predicted proton recoil RBE is then reasonably close to the experimental neutron RBE values found when taking into account the variation inherent in biological experiments. The work has some important consequences. The data of Hall et al (1975 Radiat. Res. 64 245–55) shows that the highest RBE values are found with neutron energies around 0.3–0.4 MeV, but this energy cannot possibly generate recoil proton energies which are higher, as necessary for a 0.68 MeV proton with a 30.5 keV μm−1 LETU (the LET value which provides the maximum obtainable RBE for a specified ion). For 0.4 MeV neutrons with proton recoil energies of around 0.2 MeV, the latter have a LET of around 62.88 keV μm−1. This could have an impact on proton beam RBE modelling. However, this is compensated by finding that the maximum radiosensitivity for mono-energetic neutrons was around 1.7 times larger than previously suggested from experimental ion beam studies, probably due to the necessary spreading out of Bragg peaks for ion beam experimental purposes, sampling errors and particle range considerations. This semi-empirical model can be used with minimal computer support and could have applications in ionic beams and in radioprotection. [ABSTRACT FROM AUTHOR]

The recently developed directional relativistic spectrum simulator (DRESS) code has been validated for the first time against numerical calculations and experimental measurements performed on the Mega Ampere Spherical Tokamak. In this validation, the neutron emissivities and rates computed by DRESS are benchmarked against TRANSP/NUBEAM predictions while the neutron energy spectra provided by DRESS taking as input TRANSP/NUBEAM and ASCOT/BBNBI in Gyro-Orbit mode fast ion distributions are validated against proton pulse height spectra measured by the neutron flux monitor. Excellent agreement was found between DRESS and TRANSP/NUBEAM predictions of local and total neutron emission. [ABSTRACT FROM AUTHOR]

The influence of low-mode-driven asymmetry on yield degradation in shaped-pulse indirect-drive implosions has been investigated at the 100 kJ laser facility. In this work, P2- and P4-driven asymmetries were tuned by varying hohlraum gas-fill density and capsule diameter. The measured neutron yield varied from 2.1 × 109 to 7.6 × 109 and the yield measured by a 1D simulation (YOC1D) was increased from 3% to 16%. Meanwhile, considering the temporal P2- and P4-driven asymmetries, the yields measured by 2D simulations (YOC2D) were from 26% to 81% (the YOC2D of the majority of the shots was higher than 50%). Furthermore, both the ion temperature and neutron bang-time showed good agreement between the measurements and the 2D simulations. The simulations demonstrated that the temporal P2- and P4-driven asymmetries can decrease the efficiency of PdV work and increase the energy loss due to electron thermal conduction. In addition, the internal energy of the deuterium (DD) fuel clearly decreased and the neutron yield was degraded by low-mode asymmetry. In a future work, we will enlarge the cylindrical hohlraum diameter or use an I-hohlraum to improve the low-mode-driven symmetry, along with measurement of the hot-spot shape. [ABSTRACT FROM AUTHOR]

The incident neutron energy dependence on the neutron multiplication rate constant α is studied for 235U- and 239Pu-based nuclear explosions. At high neutron energy, α comes out to be about 10 generations/shake for both 235U and 239Pu. In addition, the photon gas model seems to hold well for the very early stage of a nuclear explosion as one is able to reproduce the yield (20.4 ± 2.4) kiloton for the Trinity test. [ABSTRACT FROM AUTHOR]

Thermalized neutrons arising at the surface of solar planets are produced from the interaction of cosmic rays with the nucleus consisting of surficial materials. The neutron energy spectrum in the range between thermal and epithermal regions at the lunar surface was investigated based on the combination of the isotopic variations of Sm and Gd caused by the thermal neutron-capture reactions in our previous study, with those of Dy, Er, and Yb caused by the epithermal neutron-capture reactions in this study. The detailed comparison of the systematic isotopic variations among Sm, Gd, Dy, Er, and Yb helps to construct a neutron energy spectrum at the surface of the Moon. Seven kinds of lunar soils at different depths of the drill core recovered from the Apollo 15 landing site (A-15) were used in this study. Isotopic variations of 164Dy/161Dy, 168Er/167Er, and 168Yb/174Yb were newly found in the A-15 samples, and showed the depth dependence caused by the interaction with cosmic-ray irradiation. In particular, the combination of the isotopic shifts of 168Er/167Er and 150Sm/149Sm could be effectively used to evaluate the epithermal neutron fluences of 5.4–8.1 × 1017 n cm−2 that were more than 10 times higher than thermal neutron fluences of 0.48–0.69 × 1017 n cm−2 reestimated in this study. [ABSTRACT FROM AUTHOR]

The superheavy nuclei have been examined systematically in the region 158 ⩽ N ⩽ 218, 162 ⩽ N ⩽ 212 for Z = 122 and 128, respectively. The explicit density-dependent meson-exchange (DD-ME) and point-coupling (DD-PC) models within the framework of covariant density functional theory (CDFT) have been used to study the structural and decay properties of the isotopic series which includes the separable form of a finite range of pairing interaction. From the potential energy curves, the ground state properties of nuclei are predicted. Due to the importance of the shell effect in the superheavy region, the Strutinsky shell correction method has been employed for a better understanding of the extra stability of nuclei. The results from neutron pairing energy, two-neutron separation energy (S2n), single-particle energy levels, and total shell-correction energy strongly support N = 168, 174, and 178 as deformed neutron-magic numbers from both the force parameter, in both the isotopic series. N = 172 and 184 are predicted as spherical magic with DD-ME2 interaction in the Z = 122 isotopic series. Using three different semi-empirical approaches named UNIV2, SemFIS2, and ImSahu, the α-decay properties are studied and compared with available experimental data, FRDM2012 and the WS4 mass model. The stability of synthesized superheavy nuclei can be determined by comparing spontaneous fission half-lives with α-decay half-lives. [ABSTRACT FROM AUTHOR]

Neutron-impact single and double ionization cross sections of the He atom are calculated near the neutron-alpha particle collision resonance. Calculations using the time-dependent close-coupling method for total and differential cross sections are made at 8 incident neutron energies ranging from 250 to 2000 keV. At the resonance energy peak the double ionization cross sections unexpectedly become larger than the single ionization cross sections. This finding appears to be related to the high velocity of the recoiling alpha particle, which makes it unlikely that the atomic electrons can recombine with the alpha particle nucleus, enhancing the double ionization cross section. [ABSTRACT FROM AUTHOR]

Acceleration of ions to multi-MeV energies is investigated in various plasma devices to better understand processes in astrophysical plasmas and to develop efficient accelerators for a variety of applications. This paper reports the production of proton, deuteron, and electron beams in a z-pinch—a cylindrically symmetric plasma column that is compressed by its own magnetic field. For this work, the GIT-12 pulsed-power generator was used to drive a novel configuration of z-pinch that dramatically enhanced ion acceleration associated with disruption of the current by instabilities in the compressed plasma. During the disruption of 3 MA current, hydrogen ions were accelerated up to at least 50 MeV, which is almost a hundred-times the ion energy provided by the generator driving voltage of 0.6 MV. Under optimal conditions, the total numbers of hydrogen ions with energies above 20 and 50 MeV were 4 × 1013 and 1011, respectively. Accelerated deuterons produced one 20 ns (full width at half maximum) pulse of fast neutrons via D(d, n)3He and other nuclear reactions. A maximum neutron output of (1.0 ± 0.2) × 1012 neutrons/sr was observed downstream, i.e., in the anode to cathode direction. In this direction, the maximum neutron energy reached 58 ± 7 MeV. Both ion and neutron beams in our experiment reached an end-point energy of about 60 MeV, which is the highest value observed in pulsed-power devices. A localized peak voltage of ≳60 MV was driven by the inductive energy that was stored around the plasma column and that was extracted during a sub-nanosecond current drop. Considering the natural occurrence of current-carrying columns in laboratory and space plasmas, the current interruption observed in z-pinches could represent a more general physical process that contributes to the efficient conversion of magnetic energy into the energy of particle beams in various plasmas. [ABSTRACT FROM AUTHOR]

In order to shield neutron and gamma rays efficiently, a multilayer model is designed with metal hydrides and heavy metals and is analysed based on Monte Carlo simulations. In terms of shielding performance, the hydrogen in metal hydrides acts as a moderator to slow down the neutron energy and heavy metals are good for absorbing gamma rays. A simulation and calculational analysis are carried out with various parameters such as spectrum change, shield thickness, and number of multilayers. In addition, the rate of DPA (displacement per atom) is analysed to estimate both the lifetime and radiation resistance with the MCNP code. From lots of simulations, ZrH2 and W couples are the best candidate especially for shielding gamma rays, while TiH2 with W is good for neutron shielding. The concept of multilayer metal hydride such as TiH2 and ZrH2 coupled with W could be one of best combinations to shield both neutron and gamma-rays in many nuclear facilities such as nuclear reactor, fusion reactor and other applications. [ABSTRACT FROM AUTHOR]

The University of Washington (UW) Clinical Neutron Therapy System (CNTS) has been used to treat over 3300 patients. Treatment planning for these patients is currently performed using an MV x-ray model in Pinnacle® adapted to fit measurements of fast neutron output factors, wedge factors, depth-dose and lateral profiles. While this model has provided an adequate representation of the CNTS for 3D conformal treatment planning, later versions of Pinnacle did not allow for isocentric gantry rotation machines with a source-to-axis distance of 150 cm. This restriction limited the neutron model to version 9.0 while the photon and electron treatment planning at the UW had moved on to newer versions. Also, intensity modulated neutron therapy (IMNT) is underdevelopment at the UW, and the Pinnacle neutron model developed cannot be used for inverse treatment planning. We have used the MCNP6 Monte Carlo code system to develop Collapsed Cone (CC) and Singular Value Decomposition (SVD) neutron scattering kernels suitable for integration into the RayStation treatment planning system. Kernels were generated for monoenergetic neutrons with energies ranging from 1 keV to 51 MeV, i.e. the energy range most relevant to the CNTS. Percent depth dose (PDD) profiles computed in RayStation for the CC and SVD kernels are in excellent agreement with each other for depths beyond the beam's dose build-up region (depths greater than about 1.7 cm) for open 2.8 × 2.8 cm2, 10.3 × 10.3 cm2, and 28.8 × 32.8 cm2 fields. Lateral profiles at several depths, as well as the PDD, calculated using the CC kernels in RayStation for the full CNTS energy spectrum pass a 3%/3 mm gamma test for field sizes of 2.8 × 2.8 cm2, 10.0 × 10.3 cm2, and 28.8 × 32.8 cm2. [ABSTRACT FROM AUTHOR]

Laser-plasma x-ray sources have garnered interest from various communities due to their ability to generate high photon-energies from a small source size. The passive imaging of high energy x-rays and neutrons is also a useful diagnostic in laser-driven fusion capsules as well as laboratory astrophysics experiments which aim to study small samples of transient electron-positron plasmas. Here we study a coded aperture with scatter and partial attenuation included, which we call a 'CASPA', and compare them to the more common method of pinhole imaging. As well as discussing the well-known increased throughput of coded apertures, we also show that the decoding algorithm relaxes the need for a thick substrate. We simulate a 511 keV x-ray source through ray-tracing and Geant4 simulations to show how incomplete attenuation of the source by the mask may be less detrimental to imaging using a CASPA than to using a standard pinhole system. [ABSTRACT FROM AUTHOR]

The cross-sections of 153Eu(n,p)153Sm and 153Eu(n,α)150Pm reactions have been measured experimentally. Monoenergetic neutron beams were produced via the 3H(d,n)4He reaction using the K-400 neutron generator at China Academy of Engineering Physics (CAEP). The activity of the reaction products were measured using high-resolution gamma-ray spectroscopy. Using the 27Al(n,α)24Na reaction as the neutron fluence standard, the experimental cross-sections of the reactions 153Eu(n,p)153Sm and 153Eu(n,α)150Pm were obtained and the results are 3.6 ± 0.5, 3.8 ± 0.6, 4.5 ± 0.7 mb and 1.25 ± 0.07, 1.46 ± 0.08, 1.71 ± 0.11 mb at neutron energies 13.5 ± 0.2, 14.1 ± 0.2, 14.8 ± 0.2 MeV, respectively. These experimentally measured cross-sections were discussed and compared with some previously reported experimental results from the literature and with the evaluation data obtained from ENDF/B-VIII.0, JEFF-3.3, JENDL-4.0, RUSFOND and CENDL-3, in addition to the theoretical results obtained by using the nuclear-reaction modeling tool TALYS-1.95. [ABSTRACT FROM AUTHOR]

In the present work, we have done a comprehensive study of the low-lying energy spectrum for oxygen and fluorine chains using an ab initio no-core shell model. We have used an inside-nonlocal outside-Yukawa (INOY) potential, which is a two-body interaction but also has the effect of three-body forces via short range and nonlocal character. Also, we have performed calculations with N3LO and N2LOopt interactions and compared corresponding results with the experimental data and phenomenological USDB interaction. We have reached up to Nmax = 6 for and F, Nmax = 4 for other oxygen and fluorine isotopes, respectively. We have also discussed the binding energy of oxygen and fluorine chains. Over binding in the ground state (g.s.) energy in neutron rich oxygen isotopes is observed in our largest model space calculations. [ABSTRACT FROM AUTHOR]

In view of the fact that the fast-neutron experimental cross-section data of hafnium which is an important structural material of fusion reactor are few and there are the great differences in their evaluation values, several activation cross sections of (n, 2n), (n, p), (n, a) and (n, n′) reactions on hafnium isotopes have been investigated by neutrons generated from the T(d, n)4He reaction at the K-400 Neutron Generator at China Academy of Engineering Physics (CAEP). The gamma activities of the product nuclei were measured by a high-resolution gamma-ray spectrometer with a coaxial high-purity germanium detector. The 93Nb(n, 2n)92mNb reaction was used as neutron fluence standard, these experimental cross sections of the 174Hf(n, 2n)173Hf, 176Hf(n, 2n)175Hf, 178Hf(n, α)175m+gYb, 178Hf(n, p)178gLu, 178Hf(n, p)178mLu, 180Hf(n, 2n)179m2Hf, 180Hf(n, α)177m+gYb and 180Hf(n, n′)180mHf reactions were obtained in the neutron energy range of 13.5–14.8 MeV. These measured cross sections were discussed and compared with some previous experimental results from the literature and with the evaluation data from ENDF/B-VIII.0, CENDL-3.1, JEFF-3.3 and the theoretical results by using the computer code system Talys-1.9. [ABSTRACT FROM AUTHOR]

This paper presents new neutron-induced single event upset (SEU) data on the SRAM devices with the technology nodes from 40 nm to 500 nm due to spallation, reactor, and monoenergetic neutrons. The SEU effect is investigated as a function of incident neutron energy spectrum, technology node, byte pattern and neutron fluence rate. The experimental data show that the SEU effect mainly depends on the incident neutron spectrum and the technology node, and the SEU sensitivity induced by low-energy neutrons significantly increases with the technology downscaling. Monte–Carlo simulations of nuclear interactions with device architecture are utilized for comparing with the experimental results. This simulation approach allows us to investigate the key parameters of the SEU sensitivity, which are determined by the technology node and supply voltage. The simulation shows that the high-energy neutrons have more nuclear reaction channels to generate more secondary particles which lead to the significant enhancement of the SEU cross-sections, and thus revealing the physical mechanism for SEU sensitivity to the incident neutron spectrum. [ABSTRACT FROM AUTHOR]