New articles on Nuclear Experiment

[1] 2311.15591

Overview of the experimental quest for the giant pairing vibration

The search for the giant pairing vibration (GPV) has a long standing history since the 1970's when it was predicted. First experimental measurements focused on (p,t) transfer reactions in the heavy nuclei and did not show convincing evidence. The discovery of a signal compatible with the GPV in the light carbon isotopes has renewed the interest for the GPV. It triggered new theoretical models showing that the GPV in the heavy nuclei might be too wide or too melted to be observed and triggered new experiments with radioactive probes based on ($^{6}$He,$^{4}$He) transfer.

[2] 2311.15935

Study of proton-unbound states in $^{24}{\rm Al}$ relevant for the $^{23}{\rm Mg}(p,γ)$ reaction in novae

Background: The nucleosynthesis of several proton-rich nuclei is determined by radiative proton-capture reactions on unstable nuclei in nova explosions. One such reaction is $^{23}{\rm Mg}(p,\gamma)^{24}{\rm Al}$, which links the NeNa and MgAl cycles in oxygen-neon (ONe) novae. Purpose: To extract $^{23}{\rm Mg}(p,\gamma)^{24}{\rm Al}$ resonance strengths from a study of proton-unbound states in $^{24}{\rm Al}$, produced via the $^{24}$Mg($^{3}$He,$t$) reaction. Methods: A beam of $^3 {\rm He}^{2+}$ ions at 50.7 MeV was used to produce the states of interest in $^{24}$Al. Proton-triton angular correlations were measured with a $K=600$ QDD magnetic spectrometer and a silicon detector array, located at iThemba LABS, South Africa. Results: We measured the excitation energies of the four lowest proton-unbound states in $^{24}$Al and place lower-limits on $\Gamma_p/\Gamma$ values for these four states. Together with USD-C shell-model calculations of partial gamma widths, the experimental data are also used to determine resonance strengths for the three lowest $^{23}{\rm Mg}(p,\gamma)^{24}{\rm Al}$ resonances. Conclusions: The energy of the dominant first $^{23}{\rm Mg}(p,\gamma)$ resonance is determined to be $E_{r} = 481.4 \pm 1.1$ keV, with a resonance strength $\omega \gamma = 18 \pm 6$ meV.

[3] 2309.07083

Fukushima tritiated water release -- What is the polemic all about?

A mere amount of 2.2 grams (780 TBq) of tritium, diluted in $1.25 \cdot 10^6$ m$^3$ water, contained in 1047 tanks at the Fukushima Daiichi nuclear power plant are being released to the Pacific Ocean. The operation is scheduled to last over 30 years, with not more than releasing 62 mg (22 TBq) of tritium annually. The outcry in the world's press and the world's population is huge and countries like e.g. China are protesting aloud and are even banning Japanese seafood being sold in their domestic market. The outcry is real, the perceived fears are real, the havoc created on the Japanese fish market is real, but the danger is non-existing. The panic results from over-regulations initiated by the International Commission on Radiological Protection (ICRP) and similar bodies worldwide, prohibiting a reliable assessment of dangers and are thereby also preventing a solid risk analysis of real dangers.

[4] 2311.14832

Pion and kaon electromagnetic and gravitational form factors

A unified set of predictions for pion and kaon elastic electromagnetic and gravitational form factors is obtained using a symmetry-preserving truncation of each relevant quantum field equation. A key part of the study is a description of salient aspects of the dressed graviton + quark vertices. The calculations reveal that each meson's mass radius is smaller than its charge radius, matching available empirical inferences; and meson core pressures are commensurate with those in neutron stars. The analysis described herein paves the way for a direct calculation of nucleon gravitational form factors.

[5] 2311.14967

Improved determination of the oscillator parameters in nuclei

The oscillator parameter in nuclei is refitted to reproduce the available charge radius data. As an important improvement, we include the Coulomb term evaluated within the assumption of a uniformly charged sphere, and take into account the symmetry effect induced by the difference between N and Z numbers in a straightforward manner using the conventional parameterization. The Coulomb interaction has repulsive effect, causing the wave functions to extend further toward the nucleus exterior, resulting in an effectively larger oscillator length parameter. The symmetry effect is attractive for protons in neutron-rich nuclei and for neutrons in proton-rich nuclei, and repulsive for the other cases. Therefore, three distinct oscillator parameters are determined: one for protons, one for neutrons, and one isospin-invariant version, which is obtained by subtracting the Coulomb and symmetry contributions. Additionally, we explore the direct fit of the harmonic oscillator wave functions to the eigenfunctions of the Hartree-Fock mean field using the Skyrme interaction. Generally, this method agrees well with the others for light nuclei, typically up to $^{40}$Ca. Beyond this nucleus, however, the results begin to diverge over the orbits chosen for the fit. Only the parameters values obtained for the last occupied states agree remarkably well with the conventional ones throughout the mass range under consideration.

[6] 2311.15863

Collinear Laser Spectroscopy of $2\,{}^3\!S_1 \rightarrow 2\,{}^3\!P_{\!J}$ transitions in helium-like $^{12}\mathrm{C}^{4+}$

Transition frequencies and fine-structure splittings of the $2\,{}^3\!S_1 \rightarrow 2\,{}^3\!P_{\!J}$ transitions in helium-like $^{12}\mathrm{C}^{4+}$ were measured by collinear laser spectroscopy on a 1-ppb level. Accuracy is increased by more than three orders of magnitude with respect to previous measurements, enabling tests of recent non-relativistic QED calculations including terms up to $m\alpha^7$. Deviations between the theoretical and experimental values are within theoretical uncertainties and are ascribed to $m\alpha^8$ and higher-order contributions in the series expansion of the NR-QED calculations. Finally, prospects for an all-optical charge radius determination of light isotopes are evaluated.

[7] 2311.15943

Collinear laser spectroscopy of highly charged ions produced with an electron beam ion source

Collinear laser spectroscopy has been performed on He-like C$^{4+}$ ions extracted from an electron beam ion source (EBIS). In order to determine the transition frequency with the highest-possible accuracy, the lineshape of the fluorescence response function was studied for pulsed and continuous ion extraction modes of the EBIS in order to optimize its symmetry and linewidth. We found that the best signal-to-noise ratio is obtained using the continuous beam mode for ion extraction. Applying frequency-comb-referenced collinear and anticollinear laser spectroscopy, we achieved a measurement accuracy of better than 2\,MHz including statistical and systematic uncertainties. The origin and size of systematic uncertainties, as well as further applications for other isotopes and elements are discussed.