Zhen-Dong An

The cross sections of ¹²⁷ I( n , γ ) ¹²⁸ I and ¹³³ Cs( n , γ ) ¹³⁴ Cs play a critical role in the s -process of nuclear astrophysics, the iodine–xenon chronometer on early meteorite evolution, and understanding the performance of CsI crystal detectors for Dark Matter Detection Experiment and Coherent Elastic Neutrino-Nucleus Scattering (CE ν NS) experiments. The neutron capture cross sections of ¹²⁷ I and ¹³³ Cs were measured from 1 eV to 1 MeV using the time-of-flight method at China Spallation Neutron Source Back-n facility. The neutron capture yield was derived via the pulse-height weighting technique based on the total energy detection principle of C ₆ D ₆ detectors. In the resolved resonance region (RRR), some new resonance peaks of ¹³³ Cs( n , γ ) were observed for the first time. Resonance parameters for the neutron capture cross section were extracted using the SAMMY code from 1 eV to 4 keV, while averaged capture cross sections in the unresolved resonance region (URR) from 4 keV to 1 MeV were analyzed with TALYS. Results were compared with evaluated libraries and previous work in both RRR and URR. Astrophysical Maxwellian-averaged cross sections (MACS) were calculated for kT = 5–100 keV. At kT = 30 keV, the MACS of both ¹²⁷ I( n , γ ) ¹²⁸ I and ¹³³ Cs( n , γ ) ¹³⁴ Cs were slightly higher than those of the KADoNiS v0.3 recommended value. And the reaction rates were derived over the astrophysically relevant temperature range of s -process nucleosynthesis models. The uncertainties of present reaction rates are significantly reduced.

The neutron capture cross sections of copper play a crucial role in the s process of stellar nucleosynthesis, the production of the medical isotope ⁶⁴ Cu for PET imaging and radiotherapy, and Neutron Resonance Capture Analysis for determining the elemental and isotopic compositions of archaeological and cultural heritage materials. The Cu(n,γ) cross section was measured from 1 eV to 700 keV at the Back-n facility of the Chinese Spallation Neutron Source using the time-of-flight method. Prompt γ-rays were detected by four C ₆ D ₆ liquid scintillator detectors, and the data were analyzed using the pulse height weighting technique. The results are generally consistent with the evaluated data in the major library; however, some discrepancies were observed, offering valuable insights into the differences between five prominent evaluated data libraries. The R -matrix SAMMY code was used to extract the resonance parameters for ^63,65 Cu in the resolved resonance region. Maxwellian-averaged cross sections were calculated within the temperature range relevant to the s process nucleosynthesis model, spanning kT =5-100 keV, based on the averaged cross sections in the unresolved resonance region. At kT =30 keV, the MACSs values for ⁶³ Cu (88.1±8.8 mb) and ⁶⁵ Cu (42.1±4.2 mb) were higher than the corresponding recommendations in the Karlsruhe Astrophysical Database of Nucleosynthesis in Stars.

The ( n , γ ) cross section of silver is crucial for the nucleosynthesis process of nuclear astrophysics, the design of silver-indium-cadmium absorber rod in the nuclear reactors, and neutron resonance capture analysis for determining the elemental and isotopic composition of cultural heritage. The high-precision Ag ( n , γ ) cross section was measured from 1 eV to 1 MeV at the Back-n facility of the Chinese Spallation Neutron Source using the time-of-flight method and pulse height weighting technique. The resonance parameters were accurately extracted in the resolved resonance region by the multilevel multichannel R -matrix code . The code was used to describe the average cross sections in the unresolved resonance region, and the Maxwellian-averaged cross sections (MACSs) of Ag 107 and Ag 109 were further given in the 5–100 keV range. The MACS values at k T = 30 keV for Ag 107 ( 887 ± 89 mb ) and Ag 109 ( 903 ± 90 mb ) are slightly higher than the recommended values in the Karlsruhe Astrophysical Database of Stellar Nucleosynthesis.

The cross sections of 103Rh(n,gamma) and 103Rh(gamma,n) play a crucial role in the stellar nucleosynthesis, rhodium-based self-powered neutron detectors, and nuclear medicine. The cross sections of 103Rh(n,gamma) was measured by the time-of-flight(TOF) method from 1 eV to 1000 keV at the Back-n facility of the Chinese Spallation Neutron Source. In the resolved resonance region, the data reported multiple new resonance structures for the first time. And some discrepancies were observed, offering valuable insights into the differences between the evaluated libraries. Maxwellian-averaged cross sections (MACSs) were calculated within the temperature range of the s process nucleosynthesis model, based on the averaged cross sections in the unresolved resonance region. Meanwhile the cross sections of 103Rh(gamma,n) within the range of p process nucleosynthesis were measured using laser Compton scattering (LCS) gamma rays and a new neutron flat efficiency detector (FED) array at the Shanghai Laser Electron Gamma Source (SLEGS), Shanghai Synchrotron Radiation Facility (SSRF). Using an unfolding iteration method, 103Rh(gamma,n) data were obtained with uncertainty less than 5%, and the inconsistencies between the available experimental data and the evaluated libraries were discussed. This study provides a reliable benchmark for nuclear data evaluation and model optimization, and lays a solid foundation for Rh medical isotope applications and astrophysical research.