Eur. Phys. J. D (2025) 79: 23
https://doi.org/10.1140/epjd/s10053-025-00976-1

Regular Article - Atomic Physics

Cold source of atomic hydrogen for loading large magnetic traps

¹ Department of Physics and Astronomy, University of Turku, 20014, Turku, Finland
² Laboratoire Kastler Brossel, Sorbonne Université, CNRS, ENS-PSL Université, Collège de France, 75252, Paris, France
³ Institut Max von Laue - Paul Langevin, 71 Avenue des Martyrs, 38042, Grenoble, France
⁴ Stefan Meyer Institute for Subatomic Physics, Austrian Academy of Sciences, Dominikanerbastei 16, 1010, Vienna, Austria
⁵ Institute for Particle Physics and Astrophysics, ETH Zurich, 8093, Zurich, Switzerland

^a assema@utu.fi

Received: 19 December 2024
Accepted: 28 February 2025
Published online: 26 March 2025

Abstract

We present a design and performance tests of an intense source of cold hydrogen atoms for loading large magnetic traps. Our source is based on a cryogenic dissociator of molecular hydrogen at 0.6 K followed by a series of thermal accommodators at 0.5, 0.2 and 0.13 K with inner surfaces covered by a superfluid helium film. All components are thermally anchored to corresponding stages of a dilution refrigerator. The source provides a continuous flux of $7\times {10}^{13}$ H atoms/s in a temperature range of 130–200 mK. We have successfully used the source for loading a large Ioffe–Pritchard magnetic trap recently built in our laboratory (Ahokas et al. in Rev Sci Instrum 93(2):023201, 2022). Calorimetric measurements of the atomic recombination heat allow reliable determination of the atomic flux and H gas density in the trap. We have tested the performance of the source and loading of H atoms into the trap at various configurations of the trapping field, reducing the magnetic barrier height to 75$\%$ and 50$\%$ of the nominal value of 0.8 T (0.54 K) as well as at the open configuration of the trap at its lower end, when the atoms are in contact with the trapping cell walls covered by a superfluid helium film. In the latter case, raising the trapping cell temperature to 200–250 mK, the low-field seeking atoms at densities exceeding 10$_{}^{11}$ ${\text{cm}}^{-3}$ can be stored for the time over 10$_{}^3$ s, sufficiently long for experiments on precision spectroscopy of cold H gas.