Speaker
Description
Super-heavy elements (Z > 103) owe their existence to nuclear shell effects and deformations of the nucleus, which stabilize the nucleus against Coulomb repulsion [1]. Direct mass measurements of isotopic and isobaric chains of these nuclides using Penning traps [2] can quantify the strength of these nuclear shell effects, allowing us to map nuclear shell evolution. Additionally, precise mass measurements can complement decay spectroscopy studies by measuring the excitation energy of low-lying, long-lived isomeric states.
The SHIPTRAP experiment studies transuranic nuclei produced via fusion-evaporation reactions at rates below one particle per hour. These measurements are possible thanks to technical developments carried out in the last few years such as a cryogenic buffer-gas stopping cell and the high-precision phase-imaging ion-cyclotron-resonance technique. These have already enabled the study of exotic nuclides with production cross sections on the order of 10 nb with SHIPTRAP [3]. To complement previous measurements, mass measurements of long-lived isotopes in Cm-Fm region can contribute to asses the size of the deformed neutron shell gap at N=152 as a function of the proton number. These can be accessed using a recoil ion source.
In this contribution, the development of a new recoil-ion source branch for SHIPTRAP, dedicated to the offline study of long-lived isotopes will be discussed. It consists of a compact gas cell that uses nonlinear electric fields to stop and transport recoil ions, coupled to a cooler-buncher RFQ to provide cooled ions for Penning trap mass spectrometry.
[1] O.R. Smits et al, Nat. Rev. Phys. 6, 86-98 (2024)
[2] M. Block, Nucl. Phys. A 944 471-491 (2015)
[3] O. Kaleja et al, Phys. Rev. C 106 054325 (2022)