A large octupole magnetic trap for research with atomic hydrogen

TL;DR

This paper presents a large, mechanically stable octupole magnetic trap for atomic hydrogen, operating at cryogenic temperatures, with a significantly larger volume than previous traps, enabling advanced research in atomic physics.

Contribution

The design and implementation of a large-volume octupole magnetic trap for atomic hydrogen, combining mechanical stability with high trap depth and accessibility.

Findings

Maximum trap depth of 0.54 K achieved

Effective volume of 0.5 liters at 50 mK

Order of magnitude larger volume than previous traps

Abstract

We describe the design and performance of a large magnetic trap for storing 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 towards 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 liters for hydrogen gas at 50 mK. This is an order of magnitude larger than ever used for trapping atoms.