A large octupole magnetic trap for research with atomic hydrogen

: Ahokas J, Semakin A, Järvinen J, Hanski O, Laptiyenko A, Dvornichenko V, Salonen K, Burkley Z, Crivelli P, Golovizin A, Nesvizhevsky V, Nez F, Yzombard P, Widmann E, Vasiliev S

Publisher: AIP Publishing

: 2022

: Review of Scientific Instruments

: REVIEW OF SCIENTIFIC INSTRUMENTS

: REV SCI INSTRUM

: 023201

: 93

: 2

: 10

: 0034-6748

: 1089-7623

DOI: https://doi.org/10.1063/5.0070037(external)

: https://aip.scitation.org/doi/10.1063/5.0070037(external)

: https://arxiv.org/abs/2108.09123(external)

We describe the design and performance of a large magnetic trap for storage and cooling of atomic hydrogen (H). The trap operates in the vacuum space of a dilution refrigerator at a temperature of 1.5 K. Aiming at a large volume of the trap, we implemented the octupole configuration of linear currents (Ioffe bars) for the radial confinement, combined with two axial pinch coils and a 3 T solenoid for the cryogenic H dissociator. The octupole magnet consists of eight race-track segments, which are compressed toward each other with magnetic forces. This provides a mechanically stable and robust construction with a possibility of replacement or repair of each segment. A maximum trap depth of 0.54 K (0.8 T) was reached, corresponding to an effective volume of 0.5 l for hydrogen gas at 50 mK. This is an order of magnitude larger than ever used for trapping atoms.