Searching for the γ decay from the near-neutron threshold 2+ state in 14C: A probe of collectivization phenomena in light nuclei

The γ decay from the 2+2 near-threshold resonance in 14C, located 142 keV above the neutron emission threshold, was searched for in a fusionevaporation experiment at Argonne National Laboratory with the GODDESS setup, comprising the GRETINA γ-ray spectrometer coupled to the ORRUBA charged particle detector. The Shell Model Embedded in the Continuum predicts a significant enhancement of the 2+2 → 0 transition probability, owing to a collectivization of the near-threshold state. The corresponding γ branch is expected to be of the order of 5 × 10−5, which is comparable with the sensitivity of this experiment

Searching for the double γ-decay of the X(17) particle

The e−e+ decay of the candidate new particle X(17) has already been confirmed by previous experiments. However, theoretical models give different predictions for the spin and the parity of this particle. The double γ-decay process could be an appropriate probe to shed light on such properties. Thus, for the first time, we searched for the γγ decay of X(17) created in nuclear transitions. In this paper, we report preliminary results of two experiments on the Jπ = 0− → 0+ transition in 4He

Proton radiographs using position-sensitive silicon detectors and high-resolution scintillators

Proton therapy is a cancer treatment technique currently in growth worldwide. It offers advantages with respect to conventional X-ray and $\gamma$-ray radiotherapy, in particular, a better control of the dose deposition allowing to reach a higher conformity in the treatments. Therefore, it causes less damage to the surrounding healthy tissue and less secondary effects. However, in order to take full advantage of its potential, improvements in treatment planning and dose verification are required. A new prototype of proton Computed Tomography scanner is proposed to design more accurate and precise treatment plans for proton therapy. Here, results obtained from an experiment performed using a 100-MeV proton beam at the CCB facility in Krakow (Poland) are presented. Proton radiographs of PMMA samples of 50-mm thickness with spatial patterns in aluminum were taken. Their properties were studied, including reproduction of the dimensions, spatial resolution and sensitivity to different materials. They demonstrate the capabilities of the system to produce images with protons. Structures of up to 2 mm are nicely resolved and the sensitivity of the system was enough to distinguish thicknesses of 10 mm of aluminum or PMMA. This constitutes a first step to validate the device as a proton radiography scanner previous to the future tests as a proton CT scanner.Comment: 7 pages, 11 figures, submitted to IEEE TNS ANIMMA 2021 Conference Proceeding

Intermediate-energy Coulomb excitation of 104 Sn: Moderate E2 strength decrease approaching 100 Sn

International audienceThe reduced transition probability B(E2)↑ of the first excited 2 + state in the nucleus 104 Sn was measured via Coulomb excitation in inverse kinematics at intermediate energies. A value of 0.173(28) e 2 b 2 was extracted from the absolute cross section on a Pb target. Feeding contributions in 104 Sn from higher lying states were estimated by a reference measurement of the stable 112 Sn. Corresponding only to a moderate decrease of excitation strength relative to the almost constant values observed in the proton-rich, even-A 106−114 Sn isotopes, present state-of-the-art shell-model predictions, which include proton and neutron excitations across the N = Z = 50 shell closures as well as standard polarization charges, underestimate the experimental findings

Measurement of 19Ne spectroscopic properties via a new method of inelastic scattering to study novae

The accuracy of the predictions of the γ flux produced by a classical nova during the first hours after the outburst is limited by the uncertainties on several reaction rates, including the 18F(p,α)15O one. Better constraints on this reaction rate can be obtained by determining the spectroscopic properties of the compound nucleus 19Ne. This was achieved in a new inelastic scattering method using a 19Ne radioactive beam (produced by the GANIL-SPIRAL 1 facility) impinging onto a proton target. The experiment was performed at the VAMOS spectrometer. In this article the performances (excitation energy range covered and excitation energy resolution) and limitations of the new technique are discussed. Excitation energy resolution of σ = 33 keV and low background were obtained with this inverse kinematics method, which will allow extracting the spectroscopic properties of 19Ne

Isospin mixing at finite temperature in 80Zr

The degree of isospin mixing in the hot compound nucleus 80Zr has been extracted by statistical-model analysis of the γ-decay spectrum emitted in fusion reactions 40Ca+40Ca at Ebeam = 200 MeV and 37Cl+44Ca at Ebeam = 153 MeV. In the case of 40Ca+40Ca reaction an hindrance of first-step γ-decay is expected because in self-conjugate nuclei the E1 selection rules forbid the decay between states with isospin I=0. The results obtained at finite temperature (T ~ 2 MeV) have been used to extrapolate the degree of mixing at zero temperatur

Searching for the double gamma-decay of the X particle

The e−e+ decay of the candidate new particle X(17) has already been confirmed by previous experiments. However, theoretical models give different predictions for the spin and the parity of this particle. The double gamma-decay process could be an appropriate probe to shed light on such properties. Thus, for the first time, we searched for the gamma-gamma decay of X(17) created in nuclear transitions. In this paper, we report preliminary results of two experiments on the Jπ= 0− -> 0+ transition in 4He

Study of the γ decay of high-lying states in 208Pb via inelastic scattering of 17O ions

High-lying states in 208Pb nucleus were populated via inelastic scattering of a 17O beam at bombarding energy of 20 MeV/u. Their subsequent gamma decay was measured with the detector system AGATA Demonstrator based on HPGe detectors, coupled to an array of large volume LaBr3:Ce scintillators. Preliminary results in comparison with (γ,γ′) data, for states in the 5–8 MeV energy interval, seem to indicate that in that region the states belong to two different groups one with a isoscalar character and the other with a isovector nature. This is similar to what was observed in other stable nuclei with (α,α′γ) experiments. The multipolarity of the observed gamma transitions is determined with remarkable sensitivity thanks to angular distribution measurements. Data aiming at studying the neutron decay of the Giant Quadrupole Resonance in the 208Pb by the high resolution measurement of the following gamma decay are also presented in their preliminary form