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

## TL;DR

This paper describes a new facility combining a tandem accelerator and an ultra-low background lab for direct nuclear astrophysics measurements at very low energies, enabling studies of reactions within Gamow windows.

## Contribution

It introduces a novel combined facility at IFIN-HH for low-energy nuclear astrophysics experiments, including a tandem accelerator and a low-background lab separated by 120 km, capable of measuring reactions down to the Gamow window.

## Key findings

- Achieved the lowest energy measurement for the 13C+12C fusion reaction at 2.2 MeV.
- Measured cross sections as low as 100 pb using the activation method.
- Validated the facility's performance with reactions induced by alpha particles and light ions.

## Abstract

We present a facility for direct measurements at low and very low energies typical for nuclear astrophysics (NA). 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 are 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 or down into the Gamow windows. A good case study was the 13C+12C fusion reaction, where the proton evaporation channel leads to an activity with T1/2 = 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 Ecm=2.2 MeV, which is the lowest energy ever reached for this reaction, up to 5.3 MeV, using 13C 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 experiemnts characterizing the assembly are sown and discussed.