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Underground Nuclear Astrophysics Experiment in China (JUNA) has been commissioned by taking the advantage of the ultra-low background in Jinping underground lab. High current mA level 400 KV accelerator with an ECR source and BGO detectors were commissioned. JUNA studies directly a number of nuclear reactions important to hydrostatic stellar evolution at their relevant stellar energies. In the first quarter of 2021, JUNA performed the direct measurements of 25Mg(p,γ)26Al, 19F(p,α)16O, 13C(α,n)16O and 12C(α,γ)16O near the Gamow window. The experimental results reflect the potential of JUNA with higher statistics, precision and sensitivity of the data. The preliminary results of JUNA experiment and future plan are given.

China Institute of Atomic Energy (CIAE) is one of the most important bases for nuclear data measurement in China. In this paper, the nuclear data measurement activities at CIAE in recent years are presented. The secondary neutron emission DX and DDX measurement, the integral experiment for nuclear data benchmarking, the excitation function measurement, the neutron induced fission yields measurement and the gamma production yields measurement carried out in recent years are introduced. Furthermore, the progress of some new facilities and proposed plans (e.g. A Gamma ray Total Absorption Facility (GTAF) for (n,γ) reaction cross section measurement, A 3He detector array for (n,2n) reaction cross section measurement, the back streaming white neutron beam for nuclear data measurement at China Spallation Neutron Source (CSNS)) are also presented.

Jinping Underground lab for Nuclear Astrophysics (JUNA) will take the advantage of the ultralow background in Jinping underground lab, high current accelerator based on an ECR source and highly sensitive detector to study directly a number of crucial reactions to the hydrostatic stellar evolution for the first time at their relevant stellar energies. In its first phase, JUNA aims at the direct measurements of 25Mg(p,γ)26Al, 19F(p,α)16O, 13C(α,n)16O and 12C(α,γ)16O. The experimental setup, which include the accelerator system with high stability and high intensity, the detector system, and the shielding material with low background, will be established during the above research. The current progress of JUNA will be given.

The measurement of (n,2n) reaction cross section induced by fast neutron plays an important role in nuclear reaction mechanism research and nuclear technology applications. Experiments have been carried out over the last several decades. However, most experiments focused on solid samples including 89Y, 151Eu, 203Tl, 232Tl and so on, and there are few reported results about gaseous samples such as xenon and krypton. The 78Kr(n,2n)77Kr reaction cross section was poorly studied, and this work aimed to measure the cross section induced by 148 MeV neutron. The measurement was performed by the activation method, and the experiment was carried out at the Cockcroft Walton Accelerator of China Institute of Atomic Energy (CIAE). A cell made of PMMA was used as the gas container, and the 78Kr gas (enriched to 995% abundance) was injected into the cell using a syringe. The mass of 78Kr gas sample was determined by weighing method. Quasi monoenergetic neutron beams with a yield of about 3×1010 s-1 were produced via the T(d, n)4He reaction (Q=17.6 MeV). The ion beam current was about 250 μA, and the average energy of D+ particles was about 300 keV. The neutron flux determination was accomplished by attaching two 93Nb foils (same diameter as the cell and thickness of 50 μm) with purity of 9999% to the upstream and downstream faces of the cell. The sample was placed at 0° angel relative to the incident D+ beam direction and centered about the TTi target at a distance of about 10 cm, where the neutron flux was 2×107 cm-2·s-1. After irradiation, the activities of 77Kr and 92Nbm were measured by offline gammaray spectrometric technique using a precalibrated HPGe detector on the surface of the detector end cap due to their low activity. To obtain detection efficiencies, another irradiation experiment was carried out individually to produce 77Kr and 92Nbm with high activities, which were used to measure the count rate ratio of the characteristic γray at a distance of 25 cm and on the surface. The efficiencies at the position of 25 cm were obtained by interpolating the efficiency curve which was pre-calibrated using various standard γ sources. Besides, Monte Carlo codes were written to calculate correction factors caused by geometry difference and neutron flux difference. As a result, the cross section was determined to be (464±19) mb, and was compared with the literature data and evaluations. The result of this work is much higher than that of previously reported. The result is helpful to the analysis and evaluation of 78Kr(n,2n)77Kr reaction cross section.

Bismuth is widely used in advanced nuclear reactors such as lead-bismuth eutectic (LBE) fast reactors, space reactors and so on. Its neutron nuclear data, especially the inelastic scattering cross sections have significant impact on safety and economics of these nuclear facilities. A facility for measurement of neutron reaction cross sections using prompt γ ray method based on the HI13 tandem accelerator was established at China Institute of Atomic Energy (CIAE). Neutrons were produced using a D2 gas target bombarded with deuterons at 65, 80 and 95 MeV. The neutron target was positioned in the center of a shielding in size of 2 m×2 m×2 m composed of concrete, iron, lead and borated polyethylene. Neutrons were extracted at 0° with respect to the deuteron beam through a collimator made of copper, iron, polyethylene and lead. Neutron inelastic scattering cross sections at 90, 105 and 120 MeV were measured experimentally for 209Bi with a 209Bi sample in size of 50 mm×4 mm. A natural titanium sample in size of 50 mm×1 mm was used as the reference sample. By measuring production cross sections of the 983.5 keV γ rays produced when neutrons scattered inelastically off 48Ti nuclei, a normalization factor can be determined. 4 Clover detectors were used to measure produced γ rays. They were placed at 30°, 70°, 110° and 150° with respect to the deuteron beam. Lead shielding in thickness of approximately 2 cm was used for detector head to shield scattered γ rays. Timeofflight method was used to determine neutron energy, thus neutrons produced by DD breakup could be discriminated with neutrons produced by DD fusion. The energy and absolute efficiency were calibrated using 152Eu, 60Co, 22Na and 133Ba standard γ sources with known radioactive activities. A 508 cm×508 cm liquid scintillation detector was positioned at the end of neutron beam line to monitor the neutron fluxes passing through the samples. Two specific measurement angles at 110° and 150° were selected to obtain angleintegrated γ production cross sections by performing a simple linear summation of the partial cross sections measured at these angles. Talys 195 code was used to calculate ratios of γ production cross sections and total inelastic scattering cross sections. The experiment results were compared with other experiment data, data retrieved from ENDF/BⅧ0, JEFF33, JENDL40, ROSFOND2010 and CENDL31 evaluated nuclear data libraries as well as calculation by Talys 195 code with the default parameters. The results show that the tendency of these 3 measured energy points is similar to these results. For cross sections measured at 90 and 105 MeV, the results are closer to data calculated with Talys 195 code. For cross section measured at 120 MeV, it fits the ROSFOND2010 evaluated data better.