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)¹, a device developed in the late 1980s for the effective production and trapping of highly-charged ions (HCIs). The original EBIT used superconducting magnets to intensify the electron beam, a costly setup to build and operate. In recent years, rare-earth permanent magnets have facilitated 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 soft-iron drift tubes 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. In this work, the architecture is redesigned along the lines of a similar compact Penning trap⁴ which embeds three pairs of radially magnetized rings within yoking electrode structures to yield a higher axial field approaching about 700 mT at the trap center. We report on the progress in building this device, which can operate at electron beam energies up to 5 kV. Possible applications include the calibration of advanced quantum sensors, and the extraction/isolation of mid-Z, mid-q ions for spectroscopy of long-lived states.

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

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

³Manuscript in Preparation, A. S. Naing, E. B. Norrgard, B. C. Foo, and J. N. Tan

⁴Chapter 5 in Ph.D. Thesis of A. S. Naing, Physics Department, University of Delaware (2021)