A facility for direct measurements for nuclear astrophysics at IFIN-HH - a 3 MV tandem accelerator and an ultra-low background laboratory

Abstract

We present a facility for direct measurements at low and very low energies typical for nuclear astrophysics. The facility consists of a small and robust tandem accelerator where irradiations are made and an ultra-low background laboratory located in a salt mine where very low radio-activities can be measured. Both belong to "Horia Hulubei" National Institute for Physics and Nuclear Engineering (IFIN-HH), but are situated 120 km apart. Their performances are shown using a few cases where they were used. We argue that this facility is competitive for the study of nuclear reactions induced by alpha particles and by light ions at energies close to or down into the Gamow windows. A good case study was the 13 C+ 12 C fusion reaction, where the proton evaporation channel leads to an activity with T 1/2 =15 h, appropriate for samples' transfer to the salt mine. Measurements were done using the thick target method down into the Gamow window for energies from E c.m. = 2.2 MeV, which is the lowest energy ever reached for this reaction, up to 5.3 MeV, using 13 C beams from the 3 MV Tandetron. The activation method allowed us to determine a cross section of the order of 100 pb. Reactions induced by alphas were also measured. Proton induced resonant reactions were used to calibrate the accelerator terminal voltage. Some results of the experiments characterizing the assembly are shown and discussed.

New metrology for radon at the environmental level

“…Its unique characteristics provide great environmental conditions for ultralow background dose rate monitor calibrations. According to [35], the average underground dose rate was found to be (1.17 ± 0.14) nSv h -1 .…”

Joint research activities at the 3 MV Tandetron™ from IFIN-HH

“…Activation spectra (offline) can be afterward measured locally at GammaSpec [39] or in the nuclear astrophysics laboratory with BEGA. In order to increase the sensitivity of our measurements through background reduction, the irradiated samples can be taken to the MicroBecquerel (μBq) laboratory [40] that is located 210 m underground, inside the Slanic Salt mine [22].…”

“…The first tests with this method were done in 2013, and since then, a number of reactions have been studied successfully [21,22,41,42], with more currently ongoing or planned for the future. Given that proton and alpha capture reactions represent an important proxy in nucleosynthesis, two of the reactions that were studied are α + 64 Zn [41] and α + 58 Ni (paper in preparation).…”