Penning traps beamline

To achieve the aim of ion-ion coupling, a Penning traps beamline has been constructed in the Ion Traps laboratory at the UGR. The beamline is similar to those installed in many facilities devoted to the study of exotic elements (ISOLTRAP, SHIPTRAP, IGISOL).

Figure 1 shows an overview of the setup. The ions are created by means of the laser desorption process, where a high-power pulsed Nd:YAG laser hits a target placed inside a MALDI-TOF source. The ions are guided to the Penning traps by electrostatic lenses and deflectors through the so-called transfer section. The Penning traps are immersed in a homogeneous 7 T magnetic field, produced by a superconducting magnet, where the cooling and separation of the ions take place. Finally, the ions are ejected to the time of flight (TOF) section and enter into a microchannel plate (MCP) detector that pick ups the ion signal for identification purposes.

the_beamline

Figure 1: The Penning traps beamline at the University of Granada. The ions from the MALDI-TOF ion source enter from the right. The subsequent vacuum chambers form the transfer section to the 7T superconducting magnet. The magnet houses both Penning traps. On the left end of the setup, the MCP detector for the TOF-ICR method is mounted (Click for bigger version).

The beamline is entirely operative and several identification measurements have been made for different ion species, including 40Ca+. At present time, the efforts are focused on the study of laser-cooled ions in 7 T in order to perform Penning trap mass spectrometry by monitoring the axial fluorescence distributions of laser-cooled 40Ca+ ions. Figure 2 shows the measured fluorescence spectra for a two-ion crystal of 40Ca+ stored in a Paul trap, as well as the expected spectra for a two-ion crystal of 40Ca+ and 187Re+ stored in a Penning trap. In this way, the fluorescence-based determination of the oscillation frequency of the crystal will allow for high precision mass measurements to any ion species, regardless its mass-to-charge ratio.

sympathetic

Figure 2: Dipolar response for the axial fluorescence distribution of different ionic species. a) Measured motional spectra for an ion crystal formed by two 40Ca+ ions. b) Detailed region marked with dashed lines. We observe that the oscillation frequency of the crystal is 79.7 kHz. c) Predicted motional spectra for a crystal of 40Ca+ and 187Re+. d) Detailed region marked with dashed lines. In this case, the oscillation frequency is lower than the 40Ca+ - 40Ca+ case. Click for bigger version.

References:

  • F. Domínguez, M. J. Gutiérrez, I. Arrazola, J. Berrocal, J. M. Cornejo, J. J. Del Pozo, R. A. Rica, S. Schmidt, E. Solano and D. Rodríguez. “Motional studies of one and two laser-cooled trapped ions for electric-field sensing applications”
    Journal of Modern Optics 65, 613-621 (2018).