Controlled Extraction of Ultracold Ions from a Linear Paul Trap for Nanobeam Production

At ultralow temperatures near absolute zero, a small number of ions confined in a linear Paul trap align alone the trap axis forming a string Coulomb crystal. The emittance of an ideal Coulomb crystal is close to zero, which implies that the Paul trap can be a unique source of extremely high quality ion beams. In this paper we address the results of proof-of-principle experiments that demonstrate the feasibility of the nondestructive extraction and acceleration of string Coulomb crystals from a conventional linear Paul trap for nanobeam production. The Doppler laser-cooling technique is employed first to crystallize a few Ca-40(+) ions and, then, the DC potentials on the end electrodes are switched to launch the ions from the trap. It is confirmed that ultracold ions can be extracted without serious heating. The time interval of adjacent ions and their arrival time at the detector are controllable by changing the electrode potential. Three-dimensional multiparticle simulations are also carried out, which explain the experimental observations fairly well.