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The unstable N=42 nucleus $^{72}$Zn has been studied using multiple safe Coulomb excitation in inverse kinematics. The experiment was performed at the REX-ISOLDE facility at CERN making first use of the silicon detector array C-REX in combination with the γ-ray spectrometer Miniball. The high angular coverage of C-REX allowed to determine the reduced transition strengths for the decay of the yrast 01+, 21+ and 41+ as well as of the 02+ and 22+ states in $^{72}$Zn. The quadrupole moments of the 21+, 41+ and 22+ states were extracted. Using model independent quadrupole invariants, the ground state of $^{72}$Zn was found to have an average deformation in the γ degree of freedom close to maximum triaxiality. In comparison to experimental data in zinc isotopes with N<40, the collectivity of the 41+ state in neutron-rich $^{72}$Zn is significantly larger, indicating a collective yrast band based on the ground state of $^{72}$Zn. In contrast, a low experimental B(E2;02+→21+) strength was determined, indicating a different structure for the 02+ state. Shell-model calculations propose a 02+ state featuring a larger fraction of the (spherical) N=40 closed-shell configuration in its wave function than for the 01+ ground state.The results were also compared with beyond mean field calculations which corroborate the large deformation in the γ degree of freedom, while pointing to a more deformed 02+ state. These experimental and theoretical findings establish the importance of the γ degree of freedom in the ground state of $^{72}$Zn, located between the $^{68,70}$Ni nuclei that have spherical ground states, and $^{76}$Ge, which has a rigid triaxial shape.

The PUMA experiment was accepted at CERN in 2021. PUMA is in its construction phase. This document summarises the work performed in 2022 and focuses mainly on the design, construction and installation of the experiment.

International audience; 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.

Antiprotons as a probe to study short-lived isotopes remain unexploited despite past pioneering works with stable nuclei. In particular, 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. Such studies with short-lived nuclei and low-energy antiprotons are the first motivation of the proposed antiProton Unstable Matter Annihilation (PUMA) experiment. Today, no facility provides a collider of low-energy radioactive ions and low-energy antiprotons: PUMA aims at transporting one billion antiprotons from CERN/ELENA to CERN/ISOLDE to perform the capture of low-energy antiprotons by short-lived nuclei, and probe in this way the so-far unexplored isospin composition of the nuclear-radial-density tail of radioactive nuclei.

The first 2^{+} and 3^{-} states of the doubly magic nucleus ^{132}Sn are populated via safe Coulomb excitation employing the recently commissioned HIE-ISOLDE accelerator at CERN in conjunction with the highly efficient MINIBALL array. The ^{132}Sn ions are accelerated to an energy of 5.49 MeV/nucleon and impinged on a ^{206}Pb target. Deexciting γ rays from the low-lying excited states of the target and the projectile are recorded in coincidence with scattered particles. The reduced transition strengths are determined for the transitions 0_{g.s.}^{+}→2_{1}^{+}, 0_{g.s.}^{+}→3_{1}^{-}, and 2_{1}^{+}→3_{1}^{-} in ^{132}Sn. The results on these states provide crucial information on cross-shell configurations which are determined within large-scale shell-model and Monte Carlo shell-model calculations as well as from random-phase approximation and relativistic random-phase approximation. The locally enhanced B(E2;0_{g.s.}^{+}→2_{1}^{+}) strength is consistent with the microscopic description of the structure of the respective states within all theoretical approaches. The presented results of experiment and theory can be considered to be the first direct verification of the sphericity and double magicity of ^{132}Sn. ispartof: PHYSICAL REVIEW LETTERS vol:121 issue:25 ispartof: location:United States status: published

The first 2(+) and 3(-) states of the doubly magic nucleus Sn-132 are populated via safe Coulomb excitation employing the recently commissioned HIE-ISOLDE accelerator at CERN in conjunction with the highly efficient MINIBALL array. The Sn-132 ions are accelerated to an energy of 5.49 MeV/nucleon and impinged on a Pb-206 target. Deexciting gamma rays from the low-lying excited states of the target and the projectile are recorded in coincidence with scattered particles. The reduced transition strengths are determined for the transitions 0(g.s)(+) -> 2(1)(+), 0(g.s)(+) -> 3(1)(-), and 2(1)(+) -> 3(1)(-) in Sn-132. The results on these states provide crucial information on cross-shell configurations which are determined within large-scale shell-model and Monte Carlo shell-model calculations as well as from random-phase approximation and relativistic random-phase approximation. The locally enhanced B(E2; 0(g.s)(+) -> 2(1)(+)) strength is consistent with the microscopic description of the structure of the respective states within all theoretical approaches. The presented results of experiment and theory can be considered to be the first direct verification of the sphericity and double magicity of Sn-132.

6 pags., 4 figs., 1 tab. -- Open Access funded by Creative Commons Atribution Licence 4.0, The first 2(+) and 3(-) states of the doubly magic nucleus Sn-132 are populated via safe Coulomb excitation employing the recently commissioned HIE-ISOLDE accelerator at CERN in conjunction with the highly efficient MINIBALL array. The Sn-132 ions are accelerated to an energy of 5.49 MeV/nucleon and impinged on a Pb-206 target. Deexciting gamma rays from the low-lying excited states of the target and the projectile are recorded in coincidence with scattered particles. The reduced transition strengths are determined for the transitions 0(g.s)(+) -> 2(1)(+), 0(g.s)(+) -> 3(1)(-), and 2(1)(+) -> 3(1)(-) in Sn-132. The results on these states provide crucial information on cross-shell configurations which are determined within large-scale shell-model and Monte Carlo shell-model calculations as well as from random-phase approximation and relativistic random-phase approximation. The locally enhanced B(E2; 0(g.s)(+) -> 2(1)(+)) strength is consistent with the microscopic description of the structure of the respective states within all theoretical approaches. The presented results of experiment and theory can be considered to be the first direct verification of the sphericity and double magicity of Sn-132., The research leading to these results has received funding from the European Union’s Horizon 2020 research and innovation program under Grant Agreement No. 654002. This work was supported by the German BMBF under Contract No. 05P15PKCIA and Verbundprojekt No. 05P2015, in part by the High Performance Computing Infrastructure Strategic Program (Grant No. hp150224), in part by MEXT and Joint Institute for Computational Fundamental Science and a priority issue (elucidation of the fundamental laws and evolution of the universe) to be tackled by using the Post “K” Computer (Grants No. hp160211 and No. hp170230), in part by the HPCI system research project (Grant No. hp170182), by the CNS-RIKEN joint project for large-scale nuclear-structure calculations, in part by the Spanish Ministry of Economy, Industry and Competitiveness through Project No. FPA2017-87568-P, by FWO-Vlaanderen (Belgium), by GOA/2010/010 (BOF KU Leuven), and by the Interuniversity Attraction Poles Programme initiated by the Belgian Science Policy Office (BriX network P7/12). A. V. and L. K. thank the Bonn-Cologne Graduate School of Physics and Astronomy for financial support. J. P. and D. M. C. acknowledge the Academy of Finland (Contract No. 265023). G. R. acknowledges support by Bulgarian National Science Fund under Grant No. DN08/23/16. L. P. G. has received funding from the European Union’s Horizon 2020 research and innovation program under the Marie Skłodowska- Curie Grant Agreement No. 665779.

The HIE-ISOLDE project represents a major upgrade of the ISOLDE nuclear facility with a mandate to significantly improve the quality and increase the intensity and energy of radioactive nuclear beams produced at CERN. The project will expand the experimental nuclear physics programme at ISOLDE by focusing on an upgrade of the existing Radioactive ion beam EXperiment (REX) linac with a 40 MV superconducting linac comprising thirty-two niobium-on-copper sputter-coated quarter-wave resonators housed in six cryomodules. The new linac will raise the energy of post-accelerated beams from 3 MeV/u to over 10 MeV/u. The upgrade will be staged to first deliver beam energies of 5.5 MeV/u using two high-$\beta$ cryomodules placed downstream of REX, before the energy variable section of the existing linac is replaced with two low-$\beta$ cryomodules and two additional high-$\beta$ cryomodules are installed to attain over 10 MeV/u with full energy variability above 0.45 MeV/u. An overview of the project including a status summary of the different R&D activities and the schedule will outlined., Comment: 7 pages, 12 figures, submitted to the Heavy Ion Accelerator Technology conference (HIAT) 2012, in Chicago

Beam design and beam optics studies for the HIE-ISOLDE transfer lines [1] have been carried out in MadX [2], and benchmarked against Trace3D results [3, 4]. Magnet field errors and alignment imperfections leading to deviations from design parameters have been treated explicitly, and the sensitivity of the machine lattice to different individual error sources was studied. As a result, the tolerances for the various error-contributions have been specified for the different equipment systems. The design choices for the expected magnet field and power supply quality, alignment tolerances, instrument resolution and physical aperture were validated. The methodology and results of the studies are presented.

We propose to install a storage ring at an ISOL-type radioactive beam facility for the first time. Specifically, we intend to setup the heavy-ion, low-energy ring TSR at the HIE-ISOLDE facility in CERN, Geneva. Such a facility will provide a capability for experiments with stored secondary beams that is unique in the world. The envisaged physics programme is rich and varied, spanning from investigations of nuclear ground-state properties and reaction studies of astrophysical relevance, to investigations with highly-charged ions and pure isomeric beams. The TSR might also be employed for removal of isobaric contaminants from stored ion beams and for systematic studies within the neutrino beam programme. In addition to experiments performed using beams recirculating within the ring, cooled beams can also be extracted and exploited by external spectrometers for high-precision measurements. The existing TSR, which is presently in operation at the Max-Planck Institute for Nuclear Physics in Heidelberg, is well-suited and can be employed for this purpose. The physics cases as well as technical details of the existing ring facility and of the beam and infrastructure requirements at HIE-ISOLDE are discussed in the present technical design report.

The High Intensity and Energy (HIE)-ISOLDE project aims at several important upgrades of the present ISOLDE radioactive beam facility at CERN. The main focus lies in the energy upgrade of the post-accelerated radionuclide beams from 3 MeV/u up to 10 MeV/u through the addition of superconducting cavities. This will open the possibility of many new types of experiments including transfer reactions throughout the nuclear chart. The first stage of this upgrade involves the design, construction, installation and commissioning of two high-β cryomodules downstream of REX-ISOLDE, the existing post-accelerator. Each cryomodule houses five high-β superconducting cavities and one superconducting solenoid. Prototypes of the Nb-sputtered Quarter Wave Resonators (QWRs) cavities for the new superconducting linear accelerator have been manufactured and are undergoing RF cold tests. The project also includes a design study of improved production targets to accommodate to the future increase of proton intensity delivered by the new LINAC4 proton driver. This improvement combined with the recently installed solid state lasers of the RILIS laser ion source and the radiofrequency quadrupole cooler and buncher ISCOOL will lead to an increase of the radioactive beam intensities of up to an order of magnitude. The project has been approved by CERN and its implementation started in January 2010. An overview of the project and the timeline will be given here.