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The neutron capture cross section of 232 T h has been measured with the time-of-flight technique in the energy range from 10 to 200 keV at the back-streaming white neutron beam-line (Back-n) of China Spallation Neutron Source (CSNS). The pulse height weighting technique (PHWT) was applied with four C 6 D 6 liquid scintillators to measure the prompt gamma-ray energy release following neutron capture. The measurement data, corrected with the PHWT, have been normalized to the saturated resonances at 21.8 eV. The background was determined by a lead sample measurement and detailed Monte Carlo simulations. The 232 T h (n , γ) average cross sections have been determined relative to the 197 A u (n , γ) reaction cross sections. The results are consistent with the evaluation values of CENDL-3.2 and JENDL-5. The total uncertainties, including the PHWT, normalization, background subtraction, corrections, and relative measurement, are in the range of 4.5–4.8%. [ABSTRACT FROM AUTHOR]

Neutron-induced uranium fission reactions play an essential role in advanced nuclear energy research, basic and applied nuclear science. Based on the China Spallation Neutron Source (CSNS) Back-streaming white neutron source (Back-n), the measurement of the 236,238U fission cross sections relative to 235U from the threshold to 200 MeV was carried out by using time-of-flight (TOF) method with a multi-cell fast fission ionization chamber in double-bunch mode. The TOF spectra in double-bunch mode were unfolded by using Bayesian method. The fission cross section ratios of 238U/235U and 236U/235U were obtained. The experimental data of the 236,238U/235U fission cross section ratios measured in single-bunch mode were re-analyzed in high energy region and the upper limit was extended to 200 MeV for comparison. The experimental results in double-bunch mode are in good agreement with those in single-bunch mode and the main evaluation data within experimental uncertainties. The 236,238U(n,f) cross sections were obtained from the measured ratios and the standard 235U(n,f) cross sections and they agree well with the theoretical calculation, previous experiments, main evaluations and IAEA NDS. The experimental results can provide technical support for further experimental researches in double-bunch mode and relevant nuclear data evaluations. [ABSTRACT FROM AUTHOR]

The measurement of the relative differential cross sections of the neutron-deuteron ( n - d) elastic scattering, i.e., the 2 H(n, el) 2 H reaction, for 12 neutron energies from 13.56 MeV to 52.48 MeV has been carried out at the Back-n White Neutron Source of the China Spallation Neutron Source (CSNS). By detection of the recoil deuterons using the light charged particle detector array (LPDA) system, the relative differential cross sections of the neutrons in the center-of-mass frame were obtained and then compared with previous measurements, the theoretical calculations performed using the Nijmegen I nucleon-nucleon potential in the Faddeev formalism, and the evaluated from libraries including the ENDF-B/VIII.0, JEFF-3.3, JENDL-4.0, CENDL-3.2, and FENDL-3.2. The present work was the first measurement relative differential cross sections of the n-d scattering for the 30 MeV < E n ≤ 60 MeV neutron energy range using a white neutron source. [ABSTRACT FROM AUTHOR]

Aluminum and its alloys are widely used in the nuclear industry. Therefore, it is essential to precisely measure and accurately know the neutron total cross section of aluminum in the wider energy region. The measurement is performed by using the transmission method at the Back-n White Neutron Source of CSNS. Two aluminum samples 70 mm in diameter and thicknesses of 40 and 60 mm, respectively, were positioned at 55 m from the neutron source. The transmission detector consisted of a multi-layer fast fission chamber loaded with 235 U and 238 U, and it was located at the 76-m measurement station. By applying the time-of-flight technique, it was possible to extract the n+ 27 Al total cross section in a wide energy region, from 1 eV to 20 MeV, after the correction for the double-bunch mode of the CSNS accelerator. The total cross sections obtained with the two Al samples are consistent and the results obtained with the 235 U fission cells are in good agreement with that with 238 U in the energy range of 1–20 MeV. The uncertainty of neutron total cross section measured with 235 U for 40 mm and 60 mm thick aluminum is 0.7–22.3% and 0.6–12.4% in the energy range of 10 keV–20 MeV. Results are in fair agreement with respect to previous data and evaluations. [ABSTRACT FROM AUTHOR]

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]

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]

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]