GANIL

The $^{46}$Ar($^3$He,d)$^{47}$K reaction was performed in inverse kinematics using a radioactive $^{46}$Ar beam produced by the SPIRAL1 facility at GANIL and a cryogenic $^{3}$He target. The AGATA-MUGAST-VAMOS setup allowed the coincident measurement of the $\gamma$ rays, deuterons and recoiling $^{47}$K isotopes produced by the reaction. The relative cross sections towards the proton-addition states in $^{47}$K point towards a depletion of the $\pi s_{1/2}$ shell. The experimental findings are in good agreement with ab initio calculations, which predict that $^{46}$Ar exhibits a charge density bubble associated with a pronounced proton closed-shell character.

A Bayesian analysis aimed at tuning two parameters of the AMD model, one of them related to the in medium nucleon nucleon cross-section and the other to the clustering, has been performed. Experimental data collected with four blocks of the FAZIA setup have been compared with simulated data built with different values of the investigated parameters.

A new method, based on comparing isotopic yield ratios measured at forward and sideward polar angles and on cross-bombarding heavy nuclei with different neutron-to-proton ratios, is used to quantify the stopping power of nuclear matter in heavy-ion collisions. For central collisions of isotopically separated $^{124,129}$Xe+$^{112,124}$Sn at 100~MeV/nucleon bombarding energy, measured with the 4$\pi$ multidetector INDRA at GSI, a moderate transparency is deduced for hydrogen isotopes, whereas for heavier fragmentation products with atomic number $Z \ge 3$ a high transparency exceeding 50\% is observed. An anomalously large transparency is found for alpha particles, and possible explanations are presented.

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Low-lying excited states in $^{93}\mathrm{Tc}$ and $^{94}\mathrm{Ru}$ were populated using the two fusion-evaporation reactions $^{90}\mathrm{Zr}(^{6}\mathrm{Li},3n)^{93}\mathrm{Tc}$ and $^{92}\mathrm{Mo}(\ensuremath{\alpha},2n)^{94}\mathrm{Ru}$ at the Cologne FN Tandem accelerator and their lifetimes were measured using a hybrid setup of high-purity germanium and fast cerium doped lanthanum bromide detectors for $\ensuremath{\gamma}\text{\ensuremath{-}}\ensuremath{\gamma}$ fast-timing. The measured lifetimes fill gaps in the experimental data for electromagnetic transition probabilities $B(\ensuremath{\sigma}\ensuremath{\lambda})$ along the $N=50$ isotonic chain and provide more insight for ambiguous cases, such as the lifetime of the ${4}_{1}^{+}$ state in $^{94}\mathrm{Ru}$. The experimental data are compared with theoretical $B(E2)$ values from a single-$j$ approximation, with state-dependent effective charges derived from $^{92}\mathrm{Mo}$ and with the results from shell-model calculations performed using the SR88MHJM interaction in the $\ensuremath{\pi}(1{p}_{1/2},\phantom{\rule{0.16em}{0ex}}0{g}_{9/2})$ model space.

BackgroundPencil Beam Scanning proton therapy has many advantages from a therapeutic point of view, but raises technical constraints in terms of treatment verification. The treatment relies on a large number of planned pencil beams (PB) (up to thousands), whose delivery is divided in several low‐intensity pulses delivered a high frequency (1 kHz in this study).PurposeThe purpose of this study was to develop a three‐dimensional quality assurance system allowing to verify all the PBs’ characteristics (position, energy, intensity in terms of delivered monitor unit—MU) of patient treatment plans on a pulse‐by‐pulse or a PB‐by‐PB basis.MethodsA system named SCICOPRO has been developed. It is based on a 10 × 10 × 10 cm3 scintillator cube and a fast camera, synchronized with beam delivery, recording two views (direct and using a mirror) of the scintillation distribution generated by the pulses. A specific calibration and analysis process allowed to extract the characteristics of all the pulses delivered during the treatment, and consequently of all the PBs. The system uncertainties, defined here as average value + standard deviation, were characterized with a customized irradiation plan at different PB intensities (0.02, 0.1, and 1 MU) and with two patient's treatment plans of three beams each. The system's ability to detect potential treatment delivery problems, such as positioning errors of the treatment table in this work (1° rotations and a 2 mm translation), was assessed by calculating the confidence intervals (CI) for the different characteristics and evaluating the proportion of PBs within these intervals.ResultsThe performances of SCICOPRO were evaluated on a pulse‐by‐pulse basis. They showed a very good signal‐to‐noise ratio for all the pulse intensities (between 2 × 10−3 MU and 150 × 10−3 MU) allowing uncertainties smaller than 580 µm for the position, 180 keV for the energy and 3% for the intensity on patients treatment plans. The position and energy uncertainties were found to be little dependent from the pulse intensities whereas the intensity uncertainty depends on the pulses number and intensity distribution. Finally, treatment plans evaluations showed that 98% of the PBs were within the CIs with a nominal positioning against 83% or less with the table positioning errors, thus proving the ability of SCICOPRO to detect this kind of errors.ConclusionThe high acquisition rate and the very high sensitivity of the system developed in this work allowed to record pulses of intensities as low as 2 × 10−3 MU. SCICOPRO was thus able to measure all the characteristics of the spots of a treatment (position, energy, intensity) in a single measurement, making it possible to verify their compliance with the treatment plan. SCICOPRO thus proved to be a fast and accurate tool that would be useful for patient‐specific quality assurance (PSQA) on a pulse‐by‐pulse or PB‐by‐PB verification basis.

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.

High-precision mass measurements of exotic $^{95-97}$Ag isotopes close to the $N = Z$ line have been conducted with the JYFLTRAP double Penning trap mass spectrometer, with the silver ions produced using the recently commissioned inductively-heated hot cavity catcher laser ion source at the Ion Guide Isotope Separator On-Line facility. The atomic mass of $^{95}$Ag was directly determined for the first time. In addition, the atomic masses of $\beta$-decaying 2$^+$ and 8$^+$ states in $^{96}$Ag have been identified and measured for the first time, and the precision of the $^{97}$Ag mass has been improved. The newly measured masses, with a precision of $\approx$ 1 keV/c$^2$, have been used to investigate the $N =$ 50 neutron shell closure confirming it to be robust. Empirical shell-gap and pairing energies determined with the new ground-state mass data are compared with the state-of-the-art \textit{ab initio} calculations with various chiral effective field theory Hamiltonians. The precise determination of the excitation energy of the $^{96m}$Ag isomer in particular serves as a benchmark for \textit{ab initio} predictions of nuclear properties beyond the ground state, specifically for odd-odd nuclei situated in proximity to the proton dripline below $^{100}$Sn. In addition, density functional theory (DFT) calculations and configuration-interaction shell-model (CISM) calculations are compared with the experimental results. All theoretical approaches face challenges to reproduce the trend of nuclear ground-state properties in the silver isotopic chain across the $N =$50 neutron shell and toward the proton drip-line.

Fusion enhancement for neutron-rich isotopes of oxygen on carbon nuclei was probed. To measure the fusion cross section a $^{20}\mathrm{O}$ beam accelerated to ${E}_{\mathrm{lab}}/A=2.7$ MeV bombarded the active-target detector MuSIC@Indiana with a fill gas of ${\mathrm{CH}}_{4}$. Examination of the average fusion cross section over the interval $0.5\ensuremath{\le}({E}_{\mathrm{c}.\mathrm{m}.}\ensuremath{-}{V}_{B})/{V}_{B}\ensuremath{\le}1.2$ for $^{16--20}\mathrm{O}+^{12}\mathrm{C}$ reveals that while even isotopes of oxygen exhibit essentially the same cross section, the cross section for odd isotopes can be either enhanced or suppressed relative to the even $A$ members of the isotopic chain. Theoretical models fail to explain the observed experimental results.

David Rowe was a highly respected theoretical physicist who made seminal contributions that improved our understanding of the atomic nucleus, in particular of the collective behaviour of its constituent nucleons - results he often obtained with the use of sophisticated group-theoretical methods. He will also be remembered as the (co-)author of monographs on nuclear physics, written with the scientific rigour that was characteristic of his research.