On 6 November, the seminar of the Nuclear Physics Department of the Laboratory of Neutron Physics was held at which Valentina Semkova (Institute for Nuclear Research and Nuclear Energy BAS, Sofia) made a report “Neutron-induced cross-section measurements by activation technique and gamma-ray spectrometry in the energy range up to 20 MeV. Compilation of experimental nuclear reaction data in EXFOR database”.

She presented cross-section data measured on Ni, Co, Zr, Mo, Pb, W and ²⁴¹Am isotopes. The measurements were carried out at the Van de Graaff accelerator in the Joint Research Centre-Geel (Belgium), the compact cyclotron in Braunschweig (Germany) and at the cyclotron in Debrecen (Hungary). The radioactivity of the reaction products in the samples was determined by gamma-ray spectrometry using HPGe detector. Both analytical and Monte Carlo methods were applied to determine the detectors’ efficiencies using standard sources calibration measurements. Special attention was paid to the calculation and uncertainty propagation of true coincidence summing correction applied in gamma spectrometry at closed geometry. V. Semkova introduced the EXFOR library of experimental nuclear reaction data and associated information that has been systematically expanded and developed as a product of the international collaboration of nuclear reaction data centres.

Head of the FLNP Sector of Neutron-Nuclear Investigations Yu. N. Kopach was an active listener of the seminar: “We have good long-lasting contacts with the Institute for Nuclear Research and Nuclear Energy. Staff members from this Institute constantly work at our laboratory. Natalia Yaneva has long worked at FLNP. She was an expert and then a chairman of the PAC for Nuclear Physics. This cooperation continues now thanks to her efforts. Another INRNE employee Elmir Dermendzhiev has long worked at FLNP. Now, Ivan Ruskov supports active contacts who has recently concluded his work at the Laboratory and turned to Bulgaria.

Yuri Kopach and Valentina Semkova, discussion after the seminar

Valentina Semkova spoke about the activation method of cross-section measurements at various facilities with various energies. There are prospects for using this method in our Laboratory. Our unique neutron sources, namely IREN and IBR-2, do not fully fit this method as far as they produce neutrons in a wide range of energies, and the measurement of neutron energy is carried out by time-of-flight method. The activation analysis needs quasi-monoenergetic neutrons because we are mainly interested in cross-sections for particular neutron energy. The TANGRA facility may be applied to the method; it produces neutrons with the energy of 14 MeV. EG-5, which now has weak intensity, may also be used for this method, but we expect to increase its intensity and produce neutrons close to monoenergetic ones, with various energies.

In fact, the neutron activation analysis is well developed in our Laboratory. However, particularly this field of its application has not been used yet although, as we have seen at the seminar, it has been widely spread in the world. Moreover, this method is used to measure not only neutron cross-sections but also the cross-sections of charged particles interactions.”

Valentina Semkova: “Our long-term cooperation with FLNP continues, and now the staff of our Institute come to this Laboratory for short-term and long-term business trips, conduct experiments. It enriches us and provides an opportunity to expand our contacts. Discussions with our colleagues from JINR and an opportunity to carry out measurements here are very useful to us.”

Olga Tarantina, JINR Weekly Newspaper