A facility for production and laser cooling of cesium isotopes and isomers

Abstract

We report on the design, installation, and test of an experimental facility for the production of ultra-cold atomic isotopes and isomers of cesium. The setup covers a broad span of mass numbers and nuclear isomers, allowing one to directly compare chains of isotopes and isotope/isomer pairs. Cesium nuclei are produced by fission or fusion-evaporation reactions using primary proton beams from a 130 MeV cyclotron impinging upon a suitable target. The species of interest is ejected from the target in ionic form, electrostatically accelerated, mass separated, and routed to a science chamber. Here, ions are neutralized by implantation in a thin foil, and extracted by thermal diffusion. A neutral vapor at room temperature is thus formed and trapped in a magneto-optical trap. Real-time fluorescence imaging and destructive absorption imaging provide information on the number of trapped atoms, their density, and their temperature. Tests with a dedicated beam of 133 Cs + ions at 30 keV energy confirm neutralization, evaporation, and laser cooling to 150 µK, with an average atomic density of 10 10 cm −3 . Availability of cold and dense atomic samples of Cs isotopes and isomers opens new avenues for high-precision measurements of isotopic and isomeric shifts thereby gaining deeper insight into the nuclear structure, as well as for sensitive measurements of isotopes' concentration ratios in trace quantities. The facility also constitutes the core for future experiments of many-body physics with nuclear isomers.

Opportunities for Fundamental Physics Research with Radioactive Molecules

“…RAPTOR connects to the JYFLTRAP beamline and thus is available for laser-assisted mass measurements of either isotopically or isomerically pure beams, or for laser-assisted decay spectroscopy. Lastly, the IGISOL facility hosts an atom trap dedicated for trapping of radioactive Cs isotopes and isomers (Giatzoglou et al, 2018). In 2022 the MORA experiment was installed, a trap-based experiment to search for a signature of CP violation in the nuclear beta decay of radioactive nuclei produced at IGISOL (Delahaye et al, 2019).…”

A new off-line ion source facility at IGISOL

“…This enabled the laser spectroscopy work in [2] by making 89 Y 2+ ions available where they would not have been previously and made possible the Penning trap mass measurement campaign, see [3], conducted fully off-line using both beamlines. Additionally, the ion source station has been used to provide well-known and identified reference ions for the on-line Penning trap mass measurements in [4] and to provide 133 Cs + for demonstrating the operation of a new laser cooling and trapping facility for the production of ultra-cold atomic samples of caesium [5]. The new station has been proven to be a useful tool in preparing for on-line experiments through allowing initial tuning of both Penning trap and collinear laser systems without disrupting preparation of the IGISOL front end.…”

Decay microscope for trapped neon isotopes

“…The static (ground or long lived isomeric) properties of stable and short-lived nuclei, are especially useful for such investigations. The isotopic masses, which grant access to Q-values and separation energies, are routinely extracted using ion traps [7], and multiple reflection massspectrometry [8]; and the long interrogation times in a magneto-optical-trap (MOT) enable to identify trace amounts of isotopes for radiometric dating [9,10], and preform laser spectroscopy of ultracold short-lived samples, which is useful for studying nuclear structure [11][12][13], measurement of atomic parity violation [14], and searches for a permanent electron electric dipole moment (EDM; [15][16][17][18]).…”