Investigating Deuterium destruction in BBN with Felsenkeller accelerator

The Big Bang Nucleosynthesis (BBN) began as the universe cooled below 0.1 MeV, about 3 seconds after the Big Bang, creating the first light elements in the universe. The primordial deuterium formed in this process is highly sensitive to the baryon density of the early universe and is therefore an excellent indicator of the same. Direct observations of the Cosmic Microwave Background (CMB) by PLANCK have constrained the baryon density at high precision (< 1%). The observations of primordial clouds provide an independent approach to constrain the cosmological parameters, but this requires accurate knowledge about the reaction rates affecting the primordial deuterium abundance. In this thesis, the focus is on the 2H(p,γ)3He reaction which is the dominant reaction that destroys the primordial deuterium. Previous studies of the reaction by the LUNA collaboration at LNGS in the BBN energy range (30 to 260 keV) found the S factor at high precision (≈ 1%). A follow-up experiment at HZDR in the higher energy range (265 to 1094 keV) found a 10% discrepancy with the LUNA S factor fit. The new 2H(p,γ)3He campaign described in this thesis aims to confirm the findings of LUNA as well as the constrain the existing tension in the S factor between these two previous measurements using an independent setup. The experiment is performed in the energy range 300 to 800 keV (lab energy) using a proton beam, solid deuterated targets and a High Purity Germanium (HPGe) detector setup. The photons produced in the reaction (Q = 5.493 MeV) are measured by the HPGe detectors, which are placed at different angles around the target chamber to facilitate a study of the angular distribution of the cross-section as well. In this thesis, all the steps performed for the measurement of the preliminary S factor for the 2H(p,γ)3He reaction are described, starting from the detector characterization, target analysis and finally the analysis of the 2H(p,γ)3He spectra to arrive at the S factor of the reaction. The preliminary results are shown, in comparison with the LUNA and HZDR measurements and the angular distribution is also discussed. Keywords: BBN, CMB, S factor, Felsenkeller