Showing papers by "Lutz Schweikhard published in 2022"

The NEXT Project: Towards Production and Investigation of Neutron-Rich Heavy Nuclides

Abstract: The heaviest actinide elements are only accessible in accelerator-based experiments on a one-atom-at-a-time level. Usually, fusion–evaporation reactions are applied to reach these elements. However, access to the neutron-rich isotopes is limited. An alternative reaction mechanism to fusion–evaporation is multinucleon transfer, which features higher cross-sections. The main drawback of this technique is the wide angular distribution of the transfer products, which makes it challenging to catch and prepare them for precision measurements. To overcome this obstacle, we are building the NEXT experiment: a solenoid magnet is used to separate the different transfer products and to focus those of interest into a gas-catcher, where they are slowed down. From the gas-catcher, the ions are transferred and bunched by a stacked-ring ion guide into a multi-reflection time-of-flight mass spectrometer (MR-ToF MS). The MR-ToF MS provides isobaric separation and allows for precision mass measurements. In this article, we will give an overview of the NEXT experiment and its perspectives for future actinide research.

Direct high-precision mass spectrometry of superheavy elements with SHIPTRAP

Abstract: Direct mass measurements in the region of the heaviest elements were performed with the Penning-trap mass spectrometer SHIPTRAP at GSI Darmstadt. Utilizing the phase-imaging ion-cyclotron-resonance mass-spectrometry technique, the atomic masses of No251 (Z=102), Lr254 (Z=103), and Rf257 (Z=104) available at rates down to one detected ion per day were determined directly for the first time. The ground-state masses of No254 and Lr255,256 were improved by more than one order of magnitude. Relative statistical uncertainties as low as δm/m≈10−9 were achieved. Mass resolving powers of 11 000 000 allowed resolving long-lived low-lying isomeric states from their respective ground states in No251,254 and Lr254,255. This provided an unambiguous determination of the binding energies for odd-A and odd-odd nuclides previously determined only indirectly from decay spectroscopy.Received 24 June 2022Accepted 28 September 2022DOI:https://doi.org/10.1103/PhysRevC.106.054325Published by the American Physical Society under the terms of the Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article's title, journal citation, and DOI. Open access publication funded by the Max Planck Society.Published by the American Physical SocietyPhysics Subject Headings (PhySH)Research AreasBinding energy & massesNuclear structure & decaysPropertiesA ≥ 220TechniquesMass spectrometryPenning trapsRadioactive beamsNuclear Physics

PUMA, antiProton unstable matter annihilation

Abstract: Abstract PUMA, antiProton Unstable Matter Annihilation, is a nuclear-physics experiment at CERN aiming at probing the surface properties of stable and rare isotopes by use of low-energy antiprotons. Low-energy antiprotons offer a very unique sensitivity to the neutron and proton densities at the annihilation site, i.e. in the tail of the nuclear density. Today, no facility provides a collider of low-energy radioactive ions and low-energy antiprotons: while not being a collider experiment, PUMA aims at transporting one billion antiprotons from ELENA, the Extra-Low-ENergy Antiproton ring, to ISOLDE, the rare-isotope beam facility of CERN. PUMA will enable the capture of low-energy antiprotons by short-lived nuclei and the measurement of the emitted radiations. In this way, PUMA will give access to the so-far largely unexplored isospin composition of the nuclear-radial-density tail of radioactive nuclei. The motivations, concept and current status of the PUMA experiment are presented.

A versatile setup for studying size and charge-state selected polyanionic nanoparticles.

Abstract: Using the example of metal clusters, an experimental setup and procedure is presented, which allows for the generation of size and charge-state selected polyanions from monoanions in a molecular beam. As a characteristic feature of this modular setup, the further charging process via sequential electron attachment within a three-state digital trap takes place after mass-selection. In contrast to other approaches, the rf-based concept permits access to heavy particles. The procedure is highly flexible with respect to the preparation process and potentially suitable for a wide variety of anionic species. By adjusting the storage conditions, i.e., the radio frequency, to the change in the mass-to-charge ratio, we succeeded in producing clusters in highly negative charge states, i.e., Ag800 7-. The capabilities of the setup are demonstrated by experiments extracting electronic and optical properties of polyanionic metal clusters by analyzing the corresponding photoelectron spectra.

Disentangling polycationic fullerenes produced from glassy carbon with multireflection time-of-flight mass spectrometry

Abstract: Carbon-cluster ions are produced by laser irradiation of glassy carbon in high vacuum. In the case of positively charged species, a bimodal cluster distribution including fullerenes with cluster-size-to-charge ratios of up to a few hundred is observed. Resolving isotopologues by use of a multireflection time-of-flight mass spectrometer allows the detection and abundance determination of multiply charged clusters. It is found that mono-, di-, and tricationic fullerenes are produced, have similar size-over-charge-state ranges, and follow log-normal distributions known to be characteristic of an underlying coalescent growth. A statistical simulation is shown to reproduce the results.

Doppler and sympathetic cooling for the investigation of short-lived radioactive ions

Abstract: At radioactive ion beam (RIB) facilities, ions of short-lived radionuclides are cooled and bunched in buffer-gas-filled Paul traps to improve the ion-beam quality for subsequent experiments. To deliver even colder ions, beneficial to RIB experiments' sensitivity or accuracy, we employ Doppler and sympathetic cooling in a Paul trap cooler-buncher. The improved emittance of ${\mathrm{Mg}}^{+}$, ${\mathrm{K}}^{+}$, and ${\mathrm{O}}_{2}^{+}$ ion beams is demonstrated by a reduced time-of-flight spread of the extracted ion bunches with respect to room-temperature buffer-gas cooling. Cooling externally-produced hot ions with energies of at least 7 eV down to a few Kelvin is achieved in a timescale of $O$(100 ms) by combining a low-pressure helium background gas with laser cooling. This is sufficiently short to cool short-lived radioactive ions. As an example of this technique's use for RIB research, the mass-resolving power in a multireflection time-of-flight mass spectrometer is shown to increase by up to a factor of 4.6 with respect to buffer-gas cooling. Simulations show good agreement with the experimental results and guide further improvements and applications. These results open a path to a significant emittance improvement and, thus, unprecedented ion-beam qualities at RIB facilities, achievable with standard equipment readily available. The same method provides opportunities for future high-precision experiments with radioactive cold trapped ions.

Simulation studies of a 30-keV MR-ToF device for highly sensitive collinear laser spectroscopy

Abstract: The Multi Ion Reflection Apparatus for Collinear Laser Spectroscopy (MIRACLS) seeks to extend the reach of high-resolution collinear laser spectroscopy (CLS) to more exotic radionuclides. In this novel technique, ion bunches of short-lived radioisotopes are trapped between two electrostatic mirrors of a Multi-Reflection Time-of-Flight (MR-ToF) device at 30-keV kinetic energy. The same ion bunch can be probed by a spectroscopy laser for thousands of times compared to a single probing in the traditional CLS measurement scheme. Thus, the experimental sensitivity is increased by more than one to two orders of magnitude. Extensive simulations are presented, demonstrating the feasibility of high-resolution collinear laser spectroscopy (CLS) in the newly envisioned MR-ToF apparatus operating at ion energies of 30 keV. Once the mechanical design and operational parameters are optimized for the requirements of CLS, the spectral line is neither significantly broadened nor distorted by the combination of CLS and MR-ToF operation. According to the simulations, the storage efficiency and the ion–laser overlap are suitable for laser excitation of the majority of the trapped ions. In summary, >90% injection and storage efficiency, >75% ion–laser overlap and a line width approaching the natural line width of the transition of interest are reached in the simulation.

0 70 10 30 v 1 2 2 Ja n 20 07 Direct mass measurements beyond the proton drip-line

Abstract: C. Rauth, ∗ D. Ackermann, K. Blaum, M. Block, † A. Chaudhuri, S. Eliseev, 4 R. Ferrer, D. Habs, F. Herfurth, F. P. Heßberger, S. Hofmann, 6 H.-J. Kluge, G. Maero, A. Mart́ın, G. Marx, M. Mukherjee, ‡ J. B. Neumayr, W. R. Plaß, W. Quint, S. Rahaman, § D. Rodŕıguez, ¶ C. Scheidenberger, L. Schweikhard, P. G. Thirolf, G. Vorobjev, 4 C. Weber, 2, § and Z. Di GSI, Planckstr. 1, 64291 Darmstadt, Germany Institut für Physik, Johannes Gutenberg-Universität, 55099 Mainz, Germany Institut für Physik, Ernst-Moritz-Arndt-Universität, 17489 Greifswald, Germany St. Petersburg Nuclear Physics Institute, Gatchina 188300, Russia Department für Physik, Ludwig-Maximilians-Universität München, 85748 Garching, Germany Institut für Physik, Johann Wolfgang Goethe-Universität Frankfurt, 60438 Frankfurt, Germany II. Physikalisches Institut, Justus-Liebig-Universität, 35392 Gießen, Germany IN2P3, LPC-ENSICAEN, 6 Bd. Marechal Juin, 14050 Caen Cedex, France (Dated: March 30, 2022)

Producing gold at ISOLDE-CERN

Abstract: The yield of 18 ion beams of radioactive gold nuclei produced in the thick uranium target at ISOLDE (CERN) by 1.4-GeV protons was measured. The production-efficiency dependence on the half-life (efficiency curve) was derived using the in-target production calculations by the FLUKA-CERN code. The irregularities in the efficiency curve for long-lived high-spin gold isomers (187,191,193Aum) were found. Three release models were tested for the efficiency-curve description.

Metal cluster plasmons analyzed by energy-resolved photoemission.

Abstract: The optical response of size-selected metal clusters is studied by wavelength-dependent photoemission and energy-resolved photoelectron detection. Relative photodetachment cross sections giving information on the plasmon are determined for the example of closed-shell Ag91-. Notably, the peak energy of this anion (3.74 eV) is higher than the small particle limit in Mie theory of 3.5 eV. Different methods to extract cross sections from the spectra are applied. In particular, we compare the results obtained by integrating the full electron yields to analyses based on evaluating specified binding energy windows. The approach opens up new possibilities to conduct studies on Landau fragmentation as a result of multielectron excitations.