The upgraded ISOLDE yield database - A new tool to predict beam intensities

At the CERN-ISOLDE facility a variety of radioactive ion beams are available to users of the facility. The number of extractable isotopes estimated from yield database data exceeds 1000 and is still increasing. Due to high demand and scarcity of available beam time, precise experiment planning is required. The yield database stores information about radioactive beam yields and the combination of target material and ion source needed to extract a certain beam along with their respective operating conditions. It allows to investigate the feasibility of an experiment and the estimation of required beamtime. With the increasing demand for ever more exotic beams, needs arise to extend the functionality of the database and website not only to provide information about yields determined experimentally, but also to predict yields of isotopes, which can only be measured with sophisticated setups. For the prediction of yields, in-target production and information about release properties of target materials must be known. While the former were estimated in a simulation campaign using FLUKA and ABRABLA codes, the latter is available from measurement data as already stored in the database. We have compiled the information necessary to predict yields, and made available a yield prediction tool as web application. This currently undergoes extensive testing and will be available as powerful tool to the ISOLDE user community.Peer reviewe

Smooth crack-free targets for nuclear applications produced by molecular plating

Vascon A, Santi S, Isse AA, et al. Smooth crack-free targets for nuclear applications produced by molecular plating. Nuclear Instruments and Methods in Physics Research A. 2013;714:163-175.The production process of smooth and crack-free targets by means of constant current electrolysis in organic media, commonly known as molecular plating, was optimized. Using a Nd salt, i.e., [Nd(NO3)(3)center dot 6H(2)O], as model electrolyte several constant current density electrolysis experiments were carried out to investigate the effects of different parameters, namely the plating solvent (isopropanol and isobutanol mixed together, pyridine, and N,N-dimethylformamide), the electrolyte concentration (0.11, 0.22, 0.44 mM), the applied current density (0.17, 0.3, 0.7, and 1.3 mA/cm(2)), and the surface roughness of the deposition substrates (12 and 24 nm). Different environments (air and Ar) were used to dry the samples and the effects on the produced layers were investigated. The obtained deposits were characterized using gamma-ray spectroscopy for determining Nd deposition yields, X-ray photoelectron spectroscopy for chemical analysis of the produced surfaces, radiographic imaging for surface homogeneity inspection, atomic force microscopy for surface roughness evaluation, and scanning electron microscopy for surface morphology investigation. The results allowed identifying the optimum parameters for the production of smooth and crack-free targets by means of molecular plating. The smoothest layers, which had an average RMS roughness of ca. 20 nm and showed no cracks, were obtained using 0.22 mM [Nd(NO3)(3)center dot 6H(2)O] plated from N,N-dimethylformamide at current densities in the range of 0.3-0.7 mA/cm(2) on the smoothest deposition substrate available. (c) 2013 Elsevier B.V. All rights reserved

The Electron Capture 163^{163}Ho Experiment ECHo: an overview

The determination of the absolute scale of the neutrino masses is one of the most challenging present questions in particle physics. The most stringent limit, $m(\bar{\nu}_{\mathrm{e}})<2$eV, was achieved for the electron anti-neutrino mass \cite{numass}. Different approaches are followed to achieve a sensitivity on neutrino masses in the sub-eV range. Among them, experiments exploring the beta decay or electron capture of suitable nuclides can provide information on the electron neutrino mass value. We present the Electron Capture $^{163}$Ho experiment ECHo, which aims to investigate the electron neutrino mass in the sub-eV range by means of the analysis of the calorimetrically measured energy spectrum following electron capture of $^{163}$Ho. A high precision and high statistics spectrum will be measured with arrays of metallic magnetic calorimeters. We discuss some of the essential aspects of ECHo to reach the proposed sensitivity: detector optimization and performance, multiplexed readout, $^{163}$Ho source production and purification, as well as a precise theoretical and experimental parameterization of the calorimetric EC spectrum including in particular the value of $Q_{\mathrm{EC}}$. We present preliminary results obtained with a first prototype of single channel detectors as well as a first 64-pixel chip with integrated micro-wave SQUID multiplexer, which will already allow to investigate $m(\nu_{\mathrm{e}})$ in the eV range.Comment: Contribution to the LTD15 Conference Proceeding

Precision Measurement of the First Ionization Potential of Nobelium

One of the most important atomic properties governing an element’s chemical behavior is the energy required to remove its least-bound electron, referred to as the first ionization potential. For the heaviest elements, this fundamental quantity is strongly influenced by relativistic effects which lead to unique chemical properties. Laser spectroscopy on an atom-at-a-time scale was developed and applied to probe the optical spectrum of neutral nobelium near the ionization threshold. The first ionization potential of nobelium is determined here with a very high precision from the convergence of measured Rydberg series to be 6.626   21 ± 0.000   05     eV . This work provides a stringent benchmark for state-of-the-art many-body atomic modeling that considers relativistic and quantum electrodynamic effects and paves the way for high-precision measurements of atomic properties of elements only available from heavy-ion accelerator facilities

Probing Sizes and Shapes of Nobelium Isotopes by Laser Spectroscopy

Until recently, ground-state nuclear moments of the heaviest nuclei could only be inferred from nuclear spectroscopy, where model assumptions are required. Laser spectroscopy in combination with modern atomic structure calculations is now able to probe these moments directly, in a comprehensive and nuclear-model-independent way. Here we report on unique access to the differential mean-square charge radii of 252, 253, 254No, and therefore to changes in nuclear size and shape. State-of-the-art nuclear density functional calculations describe well the changes in nuclear charge radii in the region of the heavy actinides, indicating an appreciable central depression in the deformed proton density distribution in 252, 254No isotopes. Finally, the hyperfine splitting of 253No was evaluated, enabling a complementary measure of its (quadrupole) deformation, as well as an insight into the neutron single-particle wave function via the nuclear spin and magnetic moment

Fusion reaction 48Ca+249Bk leading to formation of the element Ts (Z=117)

The heaviest currently known nuclei, which have up to 118 protons, have been produced in 48Ca induced reactions with actinide targets. Among them, the element tennessine (Ts), which has 117 protons, has been synthesized by fusing 48Ca with the radioactive target 249Bk, which has a half-life of 327 d. The experiment was performed at the gas-filled recoil separator TASCA. Two long and two short α decay chains were observed. The long chains were attributed to the decay of 294Ts. The possible origin of the short-decay chains is discussed in comparison with the known experimental data. They are found to fit with the decay chain patterns attributed to 293Ts. The present experimental results confirm the previous findings at the Dubna Gas-Filled Recoil Separator on the decay chains originating from the nuclei assigned to Ts

Excitation energy dependence of fragment-mass distributions from fission of Hg-180,Hg-190 formed in fusion reactions of Ar-36+Sm-144,Sm-154

Mass distributions of fission fragments from the compound nuclei 180Hg and 190Hg formed in fusion reactions 36 Ar + 144 Sm and 36 Ar + 154 Sm, respectively, were measured at initial excitation energies of E∗(180Hg) = 33–66 MeV and E∗(190Hg) = 48–71 MeV. In the fission of 180Hg, the mass spectra were well reproduced by assuming only an asymmetric-mass division, with most probable light and heavy fragment masses A ̄L/A ̄H =79/101. The mass asymmetry for 180Hg agrees well with that obtained in the low-energy β+/EC-delayed fission of 180Tl, from our earlier ISOLDE(CERN) experiment. Fission of 190Hg is found to proceed in a similar way, delivering the mass asymmetry of A ̄L/A ̄H =83/107, throughout the measured excitation energy range. The persistence as a function of excitation energy of the mass- asymmetric fission for both proton-rich Hg isotopes gives strong evidence for the survival of microscopic effects up to effective excitation energies of compound nuclei as high as 40 MeV. This behavior is different from fission of actinide nuclei and heavier mercury isotope 198Hg.status: publishe

COMPASS-A COMPAct decay spectroscopy set-up

© 2018 Elsevier B.V. A compact silicon detector array with high spatial granularity and fast, fully digital data recording has been developed and commissioned for the investigation of heavy and superheavy nuclear species. The detector array can be combined in close geometry with large volume germanium detectors. It offers comprehensive particle and photon coincidence and correlation spectroscopy by highly efficient evaporation residue, α γ conversion electron and X-ray detection supported by the high granularity of the implantation chip. Access to fast decay events in the sub-microsecond region is made possible by the fast timing properties of the digital signal processing. A novel Si-chip support design allows direct cooling of the Si-chips and short signal transport. The compact and modular mechanical design equipped with a standard flange facilitates its transport and connection to different separators at different ion beam facilities. After initial tests, first α-γ coincidence spectroscopy experiments have been performed at the LISE separator of GANIL in Caen, France, in FULIS (velocity filter) mode and at the velocity filter SHIP of GSI in Darmstadt, Germany.status: publishe

The Ca-48+Ta-181 reaction: Cross section studies and investigation of neutron-deficient 86 <= Z <= 93 isotopes

© 2019 Fusion-evaporation reactions with the doubly magic projectile 48 Ca were used to access neutron-deficient nuclei around neptunium at the velocity filter SHIP, and investigated using the COMPASS decay spectroscopy station. With the use of digital electronics, several isotopes produced via neutron, proton, and α evaporation channels were identified by establishing correlated α-decay chains with short-lived sub-μs members. Data are given on decay chains stemming from 225,226 Np, 225 U, and 222,223 Pa. New information on the isotopes 225,226 Np and 222 Pa was obtained. Production cross sections of nuclei in the region using a variety of projectiles are discussed. The measured production cross-sections indicate that the usual advantages of using 48 Ca as a beam projectile to produce nuclei Z>100 are absent in the production of these slightly lighter nuclei.status: publishe

RECENT UPGRADES OF THE SHIPTRAP SETUP: ON THE FINISH LINE TOWARDS DIRECT MASS SPECTROSCOPY OF SUPERHEAVY ELEMENTS

With the Penning-trap mass spectrometer SHIPTRAP at GSI, Darmstadt, it is possible to investigate exotic nuclei in the region of the heaviest elements. Few years ago, challenging experiments led to the direct measurements of the masses of neutron-deficient isotopes with Z = 102,103 around N = 152. Thanks to recent advances in cooling and ion-manipulation techniques, a major technical upgrade of the setup has been recently accomplished to boost its efficiency. At present, the gap to reach more rare and shorter-lived species at the limits of the nuclear landscape has been narrowed.status: publishe