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The relative differential cross sections of the 1 H (n , e l) reaction have been measured at the China Spallation Neutron Source (CSNS) Back-n white neutron source. A low-density polyethylene sample and a graphite foil were prepared for the foreground and background measurements, respectively. The charged particles were detected using the △ E - E telescope array of the Light-charged Particle Detector Array (LPDA) system. With 10 △ E - E telescopes, the relative differential cross sections of the 1 H (n , e l) reaction were obtained from 70 ∘ to 160 ∘ in the center-of-mass system in the neutron energy ( E n ) range from 6.14 to 52.48 MeV (23 energy points). The present work was the first experiment using the △ E - E telescope array of the LPDA system at CSNS. The present results are in good agreement with previous measurements, evaluations and theoretical calculations. Furthermore, this work is the first measurement in the 6.52 MeV ≤ E n ≤ 9.09 MeV, 10.57 MeV ≤ E n ≤ 12.43 MeV, and 18.05 MeV ≤ E n ≤ 20.05 MeV regions. [ABSTRACT FROM AUTHOR]

Highlights • A cable-truss hybrid double-layer deployable mechanical network constructed of equilateral Bennett linkages and planar symmetric four-bar linkages with single degree of freedom is proposed. • A cable-truss hybrid double-layer deployable mechanical network proposed in this study can fit various surfaces. • An offset feed paraboloid antenna was set up using the double-layer deployable mechanical network. • The proposed double-layer deployable mechanical network has the advantages of high deployment ratio of spatial single-loop linkages and normative motion of planar linkages. Abstract This research proposes a single degree of freedom (DOF) cable-truss hybrid double-layer deployable mechanical network (DLDMN) consisting of equilateral Bennett linkages and planar symmetric four-bar linkages. The kinematics of the equilateral Bennett linkage is investigated. Then a single-loop four-bar hybrid linkage is constructed using the equilateral Bennett linkage and planar symmetric four-bar linkage. The original form of the Bennett linkage in the hybrid linkage is replaced by its alternative form and a synchronous mechanism is introduced to obtain a hybrid linkage interlayer vertical pillar with an adjustable height. The interlayer vertical pillar is employed to a single-layer mechanical network consisting of Bennett linkages. Connecting these pillars with cables, a cable-truss hybrid DLDMN that could fit various surfaces is assembled. An offset paraboloid antenna is set up using the DLDMN. A prototype is manufactured to verify the feasibility of the design. The proposed single DOF DLDMN has the advantages of high deployment ratio of spatial single-loop linkages and normative motion of planar linkages. The proposed network can be used to construct a large-scale spaceborne deployable antenna with high stiffness. [ABSTRACT FROM AUTHOR]

232Th/233U fuel cycle is an alternate candidate for future nuclear energy. Neutron-induced fission cross section of 232Th is one of the important nuclear data if using thorium as the fuel in the future. 232Th(n, f) cross sections from 1 to 300 MeV were measured at China Spallation Neutron Source (CSNS) Back-streaming neutron facility (Back-n) relative to 235U(n, f) and n-p scattering. A fast ionization chamber for fission cross section measurement (FIXM) and a proton recoil telescope (PRT) were used to perform the measurement. The neutron energy in this measurement reaches up to 300 MeV which is supposed to be the highest among the current Experimental Nuclear Reaction Data (EXFOR) library. It stands as the only experimental data in the region of 200-300 MeV in EXFOR as well. The experimental and evaluated data of 232Th(n, f) cross section above 60 MeV are scarce, the measurement data of this work will be valuable references for future evaluation in high energy. For the data below 60 MeV, most of our data are more consistent with ENDF/B-VIII.0, excepting in the region of 1-2 MeV where our data are more in favor of CENDL-3.2. [ABSTRACT FROM AUTHOR]

As an advanced neutron imaging technique, nuclide identification radiography (NIR) using neutron resonance or cross-section differences is a promising technique for investigating nuclide spatial distribution inside samples. Since its proposal in 1980s, this technique has advanced very slowly due to many limitations in neutron source, detector efficiency and resolution. At the Back-n white neutron source at China Spallation Neutron Source, the NIR technique based on gated CMOS camera has been developed by taking the advantage of very high neutron flux and suitable energy spectrum of the Back-n neutron beam. Heavy nuclides, medium-mass nuclides and light nuclides have been tested to validate the effectiveness of the technique, covering the resonances from eV to MeV regions. Typical heavy elements such as Ag, In, Au and W, medium-mass elements such Al, Fe and Cu, light elements such as O have been used for experiments. The study shows, that nuclides with resonance peaks in the eV region can be easily identified, while the nuclides with resonance peaks above keV are difficult to be identified individually due to their narrow resonance peaks affecting the signal-to-noise ratio in the camera measurements. However, these nuclides can be differentiated for imaging by using adjacent multiple resonance peaks or distinct cross-section differences over wider energy ranges. The experiments are perhaps the first ones that demonstrate the NIR technique for the identification and imaging of nuclides with cross-section resonances covering from eV to several MeV. [ABSTRACT FROM AUTHOR]

The radar absorbing materials composited of activated carbon fibers (ACF) as wave-absorber and glass fibers (GF) as impedance modifier were successfully prepared. The structure parameters of rectangular ACF felt screen, the influences of GF-piece and the reflection properties were investigated. It was observed that the effective bandwidth (the reflection loss below −10 dB) increased with the aspect ratio ( a / b ) increasing, but decreased with aperture spacing ( δ ) increasing. A double absorption peak (16.1 dB and 14.2 dB) for the optimized configuration ( a / b = 3, δ = 5 mm, a = 30 mm) appeared at 5.8 GHz and 16.9 GHz, and a wide absorption bandwidth (4–17.6 GHz) could be achieved. When a 30 mm × 15 mm rectangular aperture was filled by GF-piece of 20 mm × 10 mm, the effective bandwidth was improved to 12.1 GHz. The composites with a wide absorption bandwidth could be achieved via designing the proper element parameters and adjusting the composition of ACF and GF. [ABSTRACT FROM AUTHOR]

The "fission electron-collection" neutron detector (FECND) is a fission-based neutron detector which has simple structure and could be used as a passive detector. In this work, a FECND prototype is fabricated and studied with thermal neutrons from a reactor. Due to the low sensitivity of FECND, the fission coat with an diameter of 93 mm and a235U mass thickness of 1 mg/cm2 was electroplated on the coated electrode of the prototype to obtain a robust signal. The experimental results indicate that the sensitivity of the prototype to thermal neutrons is 2.8 × 10−18C·cm2 and 1.3 × 10−18C·cm2 without a high voltage when the electrodes gap is 30 mm and 15 mm respectively. The sensitivities for various applied voltages are also provided for the two gaps. The data show that the both sensitivities were increased to about 1.0 × 10−17C·cm2 after a high voltage of one hundred volts was applied, and a higher voltage up to 4 kV would not increase the sensitivity distinctly. The impacts of different electrode gaps and various applied voltages are discussed. • Design and develop a prototype of "fission electron-collection" neutron detector. • Give the validation and verification of the prototype through utilizing thermal neutrons. • Give the sensitivities for different electrode gaps and various applied voltages. • Discuss the impacts of different electrode gaps and various applied voltages. [ABSTRACT FROM AUTHOR]

• Design profiled anodes to improve the uniformity of current distribution in the molecular-plating of actinide compounds. • A finite element model was utilized to optimize the setup of the anodes and the cell for high-quality plating layer. • Based on the simulations, the inhomogeneity of the molecular-plating actinide layer was decreased to 2.08% experimentally. A homogeneous thin film of actinide oxides on a metal substrate is very important for nuclear analysis. Compared with physical deposition methods, molecular plating attracts considerable attention because of its wide applicability, high utilization rate, and low consumption of actinide compounds. Distinct from conventional electroplating, molecular plating is generally performed in an organic solvent without additional supporting electrolyte except for dissolved actinide compounds. The potential distribution and the mass transfer processes are crucial for achieving high purity and uniform thickness. Because actinides are rare resources, it is essential to set up a theoretical model to ensure the controllable fabrication of actinide targets. For these, we design a profiled rotating electrode made using platinum-covered titanium wire (Pt-Ti) as the anode, and we simulate the potential and current distribution between the profiled Pt-Ti anode and the aluminum cathode by finite element analysis, considering factors such as the electrode shape, the rotation rate, the anode-cathode distance, etc. The theoretical model is accurate, and the wafer-scale actinide targets are fabricated with high quality and high efficiency. [ABSTRACT FROM AUTHOR]

The original article can be found online at https://doi.org/10.1140/epja/s10050-021-00513-9. J. A (2021) 57:232 https://doi.org/10.1140/epja/s10050-021-00513-9 In the original article the name of the second author was incorrectly written as Yiwei Zhang. [Extracted from the article]

The Back-n beam line of the China Spallation Neutron Source is the first white neutron facility in China. One of its goals is to perform radiative neutron capture cross-section (σ nγ) measurements. To study the experimental backgrounds of this new facility, a measurement of the σ nγ of 197Au was carried out with a C 6 D 6 detector system at Back-n. Time-dependent backgrounds induced by the scattered neutrons and in-beam gamma-rays were measured and analyzed with nat C and nat Pb samples. The black resonance filter technique was employed to evaluate the shape of the backgrounds and perform the normalization. Besides, Monte Carlo simulations of these backgrounds were carried out with the Geant4 toolkit. The simulated results were compared with the experimental ones and the good agreement found allowed us to validate the background evaluation method. [ABSTRACT FROM AUTHOR]

The Back-n is a high luminosity white neutron beamline at the China Spallation Neutron Source (CSNS). It started running in 2018 for various nuclear data measurements. A Light charged Particle Detector Array (LPDA) is designed for (n , lcp) reaction experiments, which includes a group of detectors and supporting systems. The Δ E - E telescope, consisting of a Low-Pressure Multi-Wire Proportional Chamber (LPMWPC) and a Si-PIN detector, is the core detector of the LPDA. From the beginning of 2018, several measurements have been performed using the Δ E-E telescopes, and the light charged particles such as 1H, 3H, 4He, and 7Li, were identified successfully. At present, the LPMWPC can identify the protons with energy as low as 0.5 MeV. In the near future, combining with CsI(Tl) crystals, a system consisting of sixteen telescopes with an energy acceptance from 0.5 MeV to 100 MeV (proton) will be constructed for general purpose of (n , lcp) measurements. [ABSTRACT FROM AUTHOR]

The Back-n white neutron source at the China Spallation Neutron Source (CSNS) was put into operation in 2018, providing a good platform for the cross-section measurement of neutron induced light charged particle (l c p) emission (n , l c p) reactions. Currently, in order to detect and identify light charged particles produced in (n , l c p) reactions at Back-n, a silicon detector array has been developed as a part of Light-charged Particle Detector Array. Composed of 15 silicon detectors, the array can detect the emitted particles ranging from 19.2°to 160.8°. The energy resolution of each silicon detector unit is better than 1% for 5.499 MeV α particles. Adopting this silicon detector array, several experimental measurements have been completed. Differential cross sections and angle-integrated cross sections in the neutron energy region ranging from the eV to the MeV range are extracted. Compared with previous measurements and evaluations, new results are obtained in the present measurements. These experiments indicate the feasibility of the silicon detector array in (n , l c p) reaction cross-section measurements. [ABSTRACT FROM AUTHOR]

• Measured the 238U/235U fission cross section ratio in 1–20 MeV. • The nonuniformity of the neutron beam profile was considered. • Experimental uncertainties of 2.3%–3.6% in 1.4–20 MeV while 4.1%–11% in 1–1.4 MeV. • Provide information and data support in relevant nuclear data evaluation. Based on the China Spallation Neutron Source (CSNS) – Back-streaming white neutron source (Back-n WNS), the measurement of the U-238/U-235 fission cross section ratio in 1–20 MeV neutron energy region has been carried out by a multi-cell fast fission ionization chamber using the time-of-flight method. The measured resonance peaks of the 235U(n, f) reaction are in good agreement with those of the ENDF/B-8.0 database. The measured six groups of the U-238/U-235 fission cross section ratios in 1–20 MeV neutron energy region agree with those of the ENDF/B-8.0 database in trend, and the average discrepancies between experiment and database are from 1.9% to 2.6%. The relative experimental uncertainties are 2.3%–3.6% (1.4–20 MeV), and the measured data agree with those of database within experimental uncertainties at most energy points. The measured U-238/U-235 fission cross section ratio could provide information and data support in relevant nuclear data evaluation. [ABSTRACT FROM AUTHOR]

The Back-n white neutron beam line, which uses back-streaming white neutrons from the spallation target of the China Spallation Neutron Source, is used for nuclear data measurements. A Micromegas-based neutron detector with two variants was specially developed to measure the beam spot distribution for this beam line. In this article, the design, fabrication, and characterization of the detector are described. The results of the detector performance tests are presented, which include the relative electron transparency, the gain and the gain uniformity, and the neutron beam profile reconstruction capability. The result of the first measurement of the Back-n neutron beam spot distribution is also presented. [ABSTRACT FROM AUTHOR]

Combined photon and neutron radiography can integrate merits of X/gamma-ray radiography and energy-selective neutron radiography and has the potential of simultaneously visualizing objects composed of high-Z materials, low-Z materials and particular isotopes that resonantly absorb neutrons at certain energies. Intense pulsed gamma bursts and wide energy spectrum neutrons at spallation sources provide a unique opportunity to perform such combined radiography research. We present the results of the combined radiography experiments performed at the back-streaming white neutron (back-n) beamline at China Spallation Neutron Source (CSNS). Gamma-ray and energy-selective neutron radiographic images of multi-element samples were taken by an ICCD camera coupled with scintillators using the time of flight (TOF) technique. High-Z (Pb, Au, W, Ta, et al.) components were visualized with the intense gamma-ray bursts. The low-Z (10B) component was confirmed with varied image contrast when neutrons with varied energies were selected. The specific elements ( nat In, 197Au and nat W) were identified with neutrons at corresponding resonant energies. The experimental results prove the potential for simultaneously visualizing and identifying high-Z materials, low-Z materials and particular nuclides via combined X-ray radiography and energy-selective neutron radiography. [ABSTRACT FROM AUTHOR]

A white neutron source for nuclear data measurement has been built and put into operation on China Spallation Neutron Source (CSNS). We developeda beam monitor for real-time online monitoring of neutron flux on the white neutron source. The beam monitor work simultaneously with other nuclear data measurement detectors to provide neutron flux for data analysis. To minimize beam disturbance and reduce the background generated by the monitor, a structure in which neutron conversion layer and Si detectors are separated is employed: A 6LiF film with a mass thickness of 360 μ g/cm 2 was deposited on a 10 μ m aluminum foil and placed inside the beam line. Eight Si-detectors with a size of 20 × 20 mm2 were placed around the film outside the beam to maximize the reception of secondary particles from the conversion layer and to avoid neutron beam irradiation. The simulation of the beam monitor (layout, counting rate, neutron disturbance, etc.), construction and online performance are described in the paper. Good online performance of the monitor was achieved during the CSNS white neutron source flux calibration experiment in March, 2018: The counting rate for the beam line operating at Ф30 mm and Ф60 mm beam pattern modes was normalized to 100 kW proton beam power, and the result is consistent with the simulation. The total uncertainty of the normalized counting rate is less than 1%. Moreover, the measurement of neutron flux in low energy region below 10 keV of the white neutron source by the monitor is discussed. [ABSTRACT FROM AUTHOR]

China Spallation Neutron Source (CSNS) has been built and commissioned successfully in 2018 which is implemented by impinging 1.6 GeV protons onto a tungsten target with 25 Hz repetition frequency. An associated white neutron beam line exploiting the back-streaming neutrons, named Back-n, with a flight path of 55 m in endstation 1 (#ES1) and 76 m in endstation 2 (#ES2) was built mainly for nuclear data measurements. The Back-n beam line started running since the beginning of 2018 and the neutron energy spectrum was measured at the very beginning since it is an essential information for feasibility study and analysis of any measurement. In this paper, the measurement of the neutron energy spectrum of Back-n #ES2 is reported. The first result of the neutron flux from 1 eV to 100 MeV measured by a fission chamber based on the 235U(n, f) reaction is presented. The total neutron flux normalized to the proton beam power of 100 kW is 7. 03 × 10 6 neutrons/cm2/s. The results show a good agreement with that of the Monte Carlo simulation as well. [ABSTRACT FROM AUTHOR]

Non-tumorous skin pigmentation disorders can have a huge negative emotional impact on patients. The correct diagnosis of these disorders is essential for proper treatments to be instituted. In this paper, we present a computerized method for classifying five non-tumorous skin pigmentation disorders (i.e., freckles, lentigines, Hori's nevus, melasma and nevus of Ota) based on probabilistic linear discriminant analysis (PLDA). To address the large within-class variance problem with pigmentation images, a voting based PLDA (V-PLDA) approach is proposed. The proposed V-PLDA method is tested on a dataset that contains 150 real-world images taken from patients. It is shown that the proposed V-PLDA method obtains significantly higher classification accuracy (4% or more with p< 0.001 in the analysis of variance (ANOVA) test) than the original PLDA method, as well as several state-of-the-art image classification methods. To the authors' best knowledge, this is the first study that focuses on the non-tumorous skin pigmentation image classification problem. Therefore, this paper could provide a benchmark for subsequent research on this topic. Additionally, the proposed V-PLDA method demonstrates promising performance in clinical applications related to skin pigmentation disorders., (Copyright © 2018. Published by Elsevier Ltd.)