The quasifission process is a close relative of fusion-fission. In both reaction channels, two nuclei collide to form a system that splits into two fragments. However, while fully equilibrated compound systems are formed during fusion-fission reactions, in quasifission, the system is out of equilibrium during the process. In this paper, we show that the experimental measurement of the atomic number of quasifission fragments reveals a strong even-odd staggering in the isotopic yields, which, in turn, can be used as a marker for nucleon dynamics. The measured data demonstrate the action of two distinct nucleon drift flows, which can be associated with the initial isospin equilibration and the subsequent mass drift.
The single-neutron transfer reaction ^19O(d,pγ)^20O has been performed at GANIL, populating states up to and above the neutron separation energy. Bound states populated by s-wave and d-wave transfer have been observed with improved experimental angular distributions. Critically, several unbound states between 7.6 MeV and 9.8 MeV have been accessed for the first time through the 19O(d,p) channel, and isolated via particle-γ spectroscopy.
The single-neutron transfer reaction 19 O(d,pγ) 20 O has been performed at GANIL, populating states up to and above the neutron separation energy. Bound states populated by s -wave and d -wave transfer have been observed with improved experimental angular distributions. Critically, several unbound states between 7.6 MeV and 9.8 MeV have been accessed for the first time through the 19 O(d,p) channel, and isolated via particle-γ spectroscopy.
The integration of the upgraded Recoil Filter Detector (RFD) with the EAGLE gamma-ray spectrometer at the Heavy Ion Laboratory, University of Warsaw, provides new opportunities for high-resolution in-beam spectroscopy. The modernization of the RFD aims to enhance performance under high-rate conditions by replacing traditional photomultiplier tubes with segmented silicon photomultiplier (SiPM) matrices and implementing a state-of-the-art FERS-5200 digital readout system. Dedicated Geant4 simulations of scintillation light distribution, induced by a 20 keV electron beam, demonstrate that individual SiPM elements operate independently, thereby improving the system’s counting-rate capability. These advancements will enable more accurate selection of evaporation residues, improved Doppler correction, and effective suppression of background contributions. The combined RFD–EAGLE-DIAMANT setup establishes a versatile experimental platform for exploring nuclear collective excitations, superdeformation, shape transitions, and the spectroscopy of heavy and exotic nuclei produced with very low cross sections.
Here we report on the measurements of the gamma -ray strength functions and nuclear level densities of 112,114Sn performed for the first time at the 9-MV Tandem accelerator facilities at Horia Hulubei Institute for Physics and Nuclear Engineering using the Oslo method. We extract thermodynamic properties and gross and fine properties of the pygmy dipole resonance for systematic comparison in the chain of Sn isotopes. The results are compared with microscopic models implemented in the TALYS reaction code and the fully microscopic quasiparticlephonon model for the underlying nuclear structure of the dipole strength in 112,114Sn. The quasiparticle-phonon model results show the importance of complex configurations to the low-energy dipole response in the pygmy dipole resonance energy region. The experimental data are further included in the cross section and reaction rate calculations for the (n, gamma ) reaction of the p-process nuclei 112,114Sn showing a significant increase in reaction rates at high temperatures compared to existing nuclear databases.
The ^46Ar(^3He,d)^47K reaction was performed in inverse kinematics using a radioactive ^46Ar beam produced by the SPIRAL1 facility at GANIL and a cryogenic ^3He target. The AGATA-MUGAST-VAMOS setup allowed the coincident measurement of the γ rays, deuterons and recoiling ^47K isotopes produced by the reaction. The relative cross sections towards the proton-addition states in ^47K point towards a depletion of the πs_1/2 shell. The experimental findings are in good agreement with ab initio calculations, which predict that ^46Ar exhibits a charge density bubble associated with a pronounced proton closed-shell character.
Ultraperipheral collisions are a source of various interesting phenomena based on photon-induced reactions. We calculate cross sections for single and any number of n, p, alpha, and gamma rays in ultraperipheral heavy-ion collision for Large Hadron Collider energies. We analyze the production of a given number of neutrons relevant for a recent ALICE experiment, for ./sNN = 5.02 TeV. In our approach, we include both single and multiple photon exchanges as well as the fact that not all photon energies are used in the process of equilibration of the residual nucleus. We propose a simple two-component model in which only part of photon energy E gamma is changed into the excitation energy of the nucleus (Eexc not equal E gamma ) and compare its results with outcomes of HIPSE and EMPIRE codes. The role of high photon energies for small neutron multiplicities is discussed. Emission of a small number of neutrons at high photon energies seems to be crucial to understand the new ALICE data. All effects work in the desired direction, but the description of the cross section of four- and five-neutron emission cross sections from first principles is rather demanding. The estimated emission of charged particles such as protons, deuterons, and alpha is briefly discussed and confronted with very recent ALICE data, obtained with a proton zero degree calorimeter.
The isospin mixing was deduced in the compound nucleus 72Kr at a low nuclear temperature around 1.3 MeV, from the gamma decay of the giant dipole resonance. The gamma rays from two compound-nucleus reactions were measured: from the 32 S + 40Ca at bombarding energy of 90 MeV characterized by isospin I = 0, and from the 31 P + 40Ca at 82 MeV used as a reference. The ELIFANT array was employed at the Bucharest Tandem Laboratory, consisting of Compton-suppressed scintillator detectors. The statistical-model analysis of the measured spectra provided a mixing parameter of (3.5 +/- 0.8)%. This new point, being at the lowest temperature compared with the few other existing ones, can validate the predictions of the temperature dependence of the isospin mixing. The isospinsymmetry-breaking correction, delta c, used for the Fermi super-allowed transitions was extracted from the present result of the isospin mixing and found to be consistent with beta decay data, theoretical predictions, and previous experimental results.
The Gamow-Teller strength distribution covering the entire beta-decay window, up to 10.312(4) MeV, of 80g+mGa was measured for the first time in photofission of UCx induced by a 50 MeV electron beam. The new data show significant enhancement in the high-energy region with a jump structure. Simultaneously, the gamma deexciting behavior of beta-populated states presents a competition between deexcitation to 2+1 [beta 2 = 0.155(9)] and to 2+2 [beta 2 = 0.0530.008 0.009)] in 80Ge. To understand these data, we performed a realistic shell-model calculation and systematic analysis of log ft ratios between precursors' beta decay to 2+2 and to 2+1 of Ga isotopes. We conclude that these phenomena evidence simultaneous impacts of nuclear shell structure and collectivity on B(GT) distribution and therefore the half-life of the precursor.
We present the first measurement of the ^{47}K(d,pγ)^{48}K transfer reaction, performed in inverse kinematics using a reaccelerated beam of ^{47}K. The level scheme of ^{48}K has been greatly extended, with nine new bound excited states identified and spectroscopic factors deduced. Uniquely, the ^{47}K(d,p) reaction gives access to nuclear states that are sensitive to the interaction of protons and neutrons in the widely spaced 1s and fp orbitals, respectively. Detailed comparisons with SDPF-U and SDPF-MU shell-model calculations reveal a number of discrepancies between theory and experiment. Intriguingly, a systematic overestimation of spectroscopic factors and a poor reproduction of the energies for 1^{-} states suggests that the mixing between the πs_{1/2}^{1}d_{3/2}^{4} and πs_{1/2}^{2}d_{3/2}^{3} proton configurations in ^{48}K is not correctly described using current interactions, challenging our description of light nuclei around the N=28 island of inversion.
The NEEDLE setup is designed and built to study exotic neutron-deficient nuclei. It allows for increased sensitivity to explore the nuclear structure close to the proton drip line. This detector setup combines the EAGLE gamma-ray spectrometer and the capabilities of the NEDA array to identify the events in which a number of neutrons were emitted from the compound nucleus. Within this contribution, the first NEEDLE campaign and future plans are discussed.
The pygmy dipole resonance (PDR) has been the subject of numer-ous studies, both experimental and theoretical. Indeed, the study of the PDR has been and still is of great interest since it allows to constrain the symmetry energy, an important ingredient of the equation of state of nuclear matter that describes the matter within neutron stars. Moreover, the PDR is predicted to play a key role in the r-pro cess via the increase of the neutron capture rate. However, despite numerous experiments dedicated to the study of the PDR, a consistent description is still missing. In this context, we have proposed to study the PDR using a new probe: the neutron inelastic scattering reaction (n,n'-y). An experiment to study the pygmy resonance in 140Ce using the (n,n'-y) reaction has been performed in Septem-ber 2022. This experiment has been made possible thanks to the high-intensity proton beam of the new accelerator SPIRAL2 at GANIL and the NFS (Neutron For Science) facility. The experimental setup was composed of the new generation multi-detectors PARIS, for the detection of-y-rays coming from the de-excitation of the PDR, and MONSTER, for the detection of scattered neutrons. In this article, the experiment motivation and description are presented.
Treatment planning systems at proton-therapy centres entirely use X-ray computed tomography (CT) as primary imaging technique to infer the proton treatment doses to tumour and healthy tissues. However, proton stopping powers in the body, as derived from X-ray images, suffer from important proton-range uncertainties. In order to reduce this uncertainty in range, one could use proton-CT images instead. The main goal of this work is to test the capabilities of a newly-developed proton-CT scanner, based on the use of a set of tracking detectors and a high energy resolution scintillator for the residual energy of the protons. Different custom-made phantoms were positioned at the field of view of the scanner and were irradiated with protons at the CCB proton-therapy center in Krakow. We measured with the phantoms at different angles and produced sinograms that were used to obtain reconstructed images by Filtered Back-Projection. The obtained images were used to determine the capabilities of our scanner in terms of spatial resolution and proton Relative Stopping Power (RSP) mapping and validate its use as proton-CT scanner. The results show that the scanner can produce medium-high quality images, with spatial resolution better than 2 mm in radiography, below 3 mm in tomography and resolving power in the RSP comparable to other state-of-the-art pCT scanners.
The DIAMANT 4 pi light-charged-particle detector array has been recently commissioned at the Heavy Ion Laboratory, University of Warsaw, and began a physics campaign there, for the first time coupled to NEEDLE: EAGLE (central European Array for Gamma Levels Evaluations) and NEDA (NEutron Detector Array) detector systems. Properties of this experimental setup and its performance during commissioning are discussed.
The emission of the pre-equilibrium particles during nuclear collisions at moderate beam energies is still an open question. This influences the properties of the compound nucleus but also changes the interpretation of the quasi-fission process. A systematic analysis of the data obtained by the FAZIA collaboration during a recent experiment with a neutron rich projectile is presented. The full range of charged particles detected in the experiment is within the limit of isotopic resolution of the FAZIA detector. Quasi-projectile (QP) fragments were detected in majority thanks to the forward angular acceptance of the experimental setup which was confirmed by introducing cuts based on the HIPSE event generator calculations. The main goal was to compare the experimental results with the HIPSE simulations after introducing these cuts to investigate the influence of the n-rich entrance channel on the QP fragment properties. More specifically, the lowering of N/Z of QP fragments with beam energy was found to be present since the initial phase of the reaction. Thus, pre-equilibrium emissions might be a possible candidate to explain such an effect.
The properties of the 2(1)(+) and 2(2)(+) excited states in C-14 were studied in an experiment conducted at the Argonne National Laboratory. A Be-9(Li-6, p gamma) fusion-evaporation reaction and the GRETINA-ORRUBA setup were employed to populate states of C-14 and detect gamma-particle coincidence events. The precise determination of the 2(1)(+) level energy, complemented by the estimation of the gamma-ray branch of the 2(2)(+) near-threshold state, will serve as a benchmark to test the Shell Model Embedded in the Continuum calculations.
. - The high-energy gamma-rays from the GDR decay of 56,60,62Ni* nuclei at finite temperature, produced in the reactions 32,34,36S + 24,26Mg at bombarding energies between 78 , 90 MeV, were measured and analyzed with statistical model using a Monte Carlo approach. It is found that the present analysis gives some evidence on the presence of an extra yield on the tail of the Giant Dipole Resonance which may be attributed to a Pygmy Dipole Resonance in an excited nucleus.
A systematic analysis of the data obtained by the FAZIA collaboration during a recent experiment with a neutron rich projectile is presented. The main goal was to compare the experimental results with the HIPSE event generator simulations to investigate the influence of the neutron rich entrance channel on the quasi-projectile fragment properties. The full isotopic range of charged particles detected in this experiment was within the limit of the resolution of the FAZIA detector. A majority of quasi-projectile fragments were detected thanks to the forward angular acceptance of the experimental setup which was confirmed through the HIPSE calculations. Essentially, the lowering of N/Z of quasi-projectile fragments with the beam energy was found to be present since the initial phase of the reaction. Thus, pre-equilibrium neutron emissions might be a possible candidate to explain such an effect.