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The atom-trap facility at the Ion-Guide Isotope Separator On-Line (IGISOL) at the University of Jyväskylä has been developed for cooling and trapping a chain of isotopes and isomers of caesium [1]. This would allow a high-precision spectroscopy from which a nuclear magnetic octupole moment can be deduced, an important parameter which helps validate nuclear theory and reveal insight on the nuclear structure [2]. Moreover, a Bose-Einstein condensate of 135mCs isomers was shown to be a potential candidate for a long-sought coherent gamma-ray source, an intriguing result of the coherent nature of the degenerate ensemble [3]. The Cs isotopes and isomers are produced via proton-induced fission of a natural uranium target in a helium buffer gas filled ion guide, extracted via gas flow, accelerated electrostatically to 30 keV, mass-separated, and finally delivered to a cold-atom chamber. Installed inside the chamber is a thin yttrium foil where implanted Cs ions can be neutralised and released using resistive heating. A special coating applied on the inner surface of the chamber then allows thermalisation of hot Cs atoms, thereby facilitating a magneto-optical trap (MOT), the initial stage of a cooling and trapping scheme. Well-established optical cooling methods such as optical molasses and degenerate Raman sideband cooling (DRSC) are subsequently applied to obtain a temperature suitable for a probing activity of interest, and ultimately reach the quantum degenerate regime of BEC.
[1] A. Giatzoglou et al., Nucl. Instrum. Methods Phys. Res. A 908 (2018) 367–375.
[2] R.P. de Groote et al., Phys. Lett. B 827 (2022) 136930.
[3] L. Marmugi, P.M. Walker, F. Renzoni, Phys. Lett. B 777 (2018) 281–285.
