A Compact 0.7 T Electron Beam Ion Trap Using Radial NdFeB Magnets

The study of multiply-ionized atoms has been greatly facilitated by the invention of the electron beam ion trap (EBIT), a device developed in the late 1980s¹ for the effective production and trapping of highly-charged ions (HCIs). To produce very high charge states, an EBIT typically uses a superconducting magnet to intensify the electron beam, a costly setup to build and operate. In recent years, rare-earth permanent magnets have been used to build compact, room-temperature EBITs that are better suited for atomic clock research and other applications requiring ions with low ionization thresholds. Based on early efforts² at NIST, a prototype miniaturized EBIT³ employed a pair of axially-magnetized NdFeB rings yoked by drift tubes of soft iron to produce a peak field of 290 mT at the trap center, demonstrating production of various highly charged ions such as Ne⁸⁺, Ar⁹⁺, Ar¹³⁺, Kr¹⁷⁺ and other species of HCIs with ionization potential up to 900 eV. The current work seeks to improve the performance of such miniaturized devices as sources of multiply-charged ions in the mid-Z and mid-q regime which can be extracted and subsequently recaptured for spectroscopy measurements. Simulations reveal that high electron current density and beam transmission through a permanent magnet structure⁴ with a peak field of 700 mT is attainable by embedding three pairs of radial ring magnets within the two end-cap drift tubes using appropriate materials.

¹M. A. Levine, et al, Physica Scripta Volume T 22, 157-163 (1988)

²S. F. Hoogerhide, et al, Atoms 3, 367-391 (2015)

³A Miniaturized Dual-Anode Electron Beam Ion Trap Using Rare-Earth Magnets, A. S. Naing, E. B. Norrgard, B. C. Foo, and J. N. Tan, (to be published)

⁴A mini-EBIT for Studying Highly Charged Ions with Low Ionization Threshold, A. S. Naing, et al, at the 2^nd North American Conference on Trapped Ions (NACTI), University of Maryland, College Park, MD USA