arXiv subjects

Á. Tóth

Publications and source records attributed to Á. Tóth.

4 recordsLinked to original sources

arXiv2025

Gas-cell development for nuclear astrophysics motivated studies on noble gas targets and the $^3$He($α$,$γ$)$^7$Be reaction

In many astrophysical scenarios, alpha induced reactions on noble gas nuclei play a crucial role. Studying these reactions in the laboratory requires the noble gas atoms to be confined in a sufficient amount to allow the reactions. At Atomki thin-windowed gas-cell targets were developed and improved for studying alpha induced reactions on noble gases. Several stages of the gas-cell design used for activation experiments and lately a version to be used for particle scattering experiments will be presented. A new experimental study of the $^3$He($α$,$γ$)$^7$Be reaction with one of the activation gas-cell targets was performed. This reaction plays an important role both in the solar pp-chains and in big bang nucleosynthesis. The reaction cross section was measured in the past in several works, however, there are still energy regions lacking experimental data, rendering the extrapolations towards the astrophysically relevant energies uncertain. New experimental total cross section of the $^3$He($α$,$γ$)$^7$Be reaction was thus determined here in the energy range of $E_\mathrm{c.m.} = 2600-3000$ keV in about 50 keV energy steps. These results confirm the overall trend, and also the absolute scale set by the only one previous measurement in this energy range. In addition, two pilot experiments with the scattering cell were performed aiming to study the $^4$He($α$,$α$)$^4$He and $^{124}$Xe($α$,$α$)$^{124}$Xe reactions at $E_α= 18$ MeV. These studies benchmark the performance of the cell and detection system both for light and heavy noble gas targets.

physics.ins-det↗

arXiv2023

Experimental $^7$Be production cross section from the $^7$Li(p,n)$^7$Be reaction at E$_p = 3.5-13$ MeV

The $^7$Li(p,n)$^7$Be reaction is widely used as neutron source for neutron induced reaction cross section measurements, and for $^7$Be radioactive source production. There are two prominent structures in the excitation function, a narrow resonance between $E_\mathrm{p}= 2.2-2.3$ MeV, and a broad peak, around $E_\mathrm{p}= 5$ MeV. There are tension between the experimental data sets both in the position and the width of this latter structure, as well as in the absolute scale of the data. In the present work the $^7$Li(p,n)$^7$Be reaction is investigated using the activation technique, with the aim of providing comprehensive cross section data covering the second structure and connecting prior literature data sets. The irradiations were performed with the Atomki cyclotron accelerator with pairs of thin foil targets, thus with precisely controlled reaction energy in the range of E$_\mathrm{p} = 3.5-13$ MeV. After the irradiations the activity of the samples was measured using a high-purity germanium detector. The energy uncertainty of the new data points is much smaller than in any of the previous works, while the cross section uncertainty is comparable with the most precise literature data. A consistent data set was obtained connecting the most recent and most precise literature data sets. With the new data the absolute magnitude of the $^7$Li(p,n)$^7$Be reaction cross section is constrained and became more precise.

nucl-ex↗

arXiv2023

Experimental determination of the $^3$He($α$,$γ$)$^7$Be reaction cross section above the $^7$Be proton separation threshold

The $^3$He($α$,$γ$)$^7$Be reaction plays a major role both in the BBN producing the majority of the primordial $^7$Li, and in the pp-chain, where it is the branching point. As a few-nucleon system, this reaction is often used to validate ab-initio theoretical calculations and/or test R-matrix theory and code implementations. For the latter, experimental data in an extended energy range is of crucial importance to test the fit and extrapolation capabilities of the different codes. The $^3$He($α$,$γ$)$^7$Be reaction cross section has been measured by several groups up to the first resonance ($E_{c.m.} \approx 3$ MeV) in the reaction. However, only one dataset exists above the $^7$Be proton separation threshold measured in a narrow energy range ($E_{c.m.} = 4.0-4.4$ MeV). In this work we extend the available experimental capture cross section database to the energy range of known $^7$Be levels. The activation method was used. The experiment was performed using a thin-window gas cell with two high-purity Al foils as entrance and exit windows. The activity of the $^7$Be nuclei implanted in the exit/catcher foil was measured by detecting the yield of the emitted $γ$~rays using shielded high-purity germanium detectors. New experimental $^3$He($α$,$γ$)$^7$Be reaction cross section data were obtained for the first time in the $E_{c.m.}=4.3-8.3$ MeV energy region. The new dataset with about 0.2 MeV step covers the energy range of known levels and particle separation thresholds. No prominent structures are observer around the $^7$Be levels. The reaction cross section is slowly increasing with increasing energy. Above the $^6$Li$+p_1$ threshold, a decrease starts in the cross section trend. The overall structure of the cross section suggest a broad resonance peaking around $E_x=7.5$ MeV $^7$Be excitation energy, with a width of 8 MeV.

nucl-ex↗

arXiv2020

High precision half-life measurement of $^{95}$Ru, $^{95}$Tc and $^{95m}$Tc with $γ$-spectroscopy

The precise knowledge of the half-life of the reaction product is of crucial importance for a nuclear reaction cross section measurement carried out with the activation technique. The cross section of the $^{92}$Mo($α$,n)$^{95}$Ru reaction was measured recently using this experimental approach. The preliminary results indicated that the literature half-life of $^{95}$Ru, derived about half a century ago, is overestimated. Therefore, the half-lives of $^{95}$Ru and its daughter isotope $^{95}$Tc and $^{95m}$Tc have been measured with high precision using $γ$-spectroscopy. The results are t$_{1/2}$=1.6033 $\pm$ 0.0044 h for $^{95}$Ru, t$_{1/2}$ = 19.258 $\pm$ 0.026 h for $^{95}$Tc and t$_{1/2}$ = 61.96 $\pm$ 0.24 d for $^{95m}$Tc. The precision of the half-life values has been increased, consequently the recently measured $^{92}$Mo($α$,n)$^{95}$Ru activation cross section will become more precise.

nucl-ex↗