Confinement in a cryogenic penning trap of highest charge state ions from EBIT

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Abstract
The retrapping of highly charged Xe44+ and Th68+,72+ ions extracted from an ‘‘electron‐beam ion trap’’ (EBIT) is demonstrated after injection of the ions into RETRAP, a cryogenic Penning trap (up to 6 T magnetic field) currently with an open cylinder design. Ion extraction in a short pulse (5–20 μs) from EBIT, essential for efficient retrapping, is employed. The ions are slowed down upon entering a deceleration tube mounted above the trap within the magnetic field. The potential is then rapidly (100 ns) decreased, enabling low‐energy ions to enter the trap. Capture efficiencies up to 25% are observed via detection of the delayed ion release pulse with a detector below the trap. Signal voltages induced in a tuned circuit due to single and multiple ions have been observed by tuning the ion resonant axial oscillation frequencies for different ions. Results from transporting and retrapping of the ions, as well as their detection, are described and the trapping efficiency is discussed. The motivation for these studies is to cool the trapped very highly charged ions to low temperatures (<4 K) in order to perform ultrahigh‐resolution precision spectroscopy, collision studies at ultralow energies, and to observe phase transitions in Coulomb clusters of highly charged ions.