Spatial and temporal detection of ions ejected from Coulomb crystals using Timepix3 Jake Diprose, Vincent Richardson, Paul Regan, Adam Roberts, Sergey Burdin, Andriana Tsikritea, Brianna Heazlewood Department of Physics, University of Liverpool, UK Coulomb crystals provide a convenient environment to study ion—molecule reactions under cold and controlled conditions.[1-2] In order to better understand the content of Coulomb crystals, the fluorescence of the laser-cooled species is monitored using a charge-coupled device (CCD) camera and time-of-flight methods are used to identify and quantify the number of trapped ions. At the University of Liverpool, a phosphor-screen and microchannel plate (MCP) detector are employed in conjunction with a Timepix3 camera to spatially and temporally analyse Coulomb crystals. Timepix3 provides nanosecond resolution detection of pixels highlighted on the phosphor screen when ions hit the MCPs,[3] enabling the differentiation between ions arriving at different times on the detector. Here results are presented of Ca + /Kr + /H 2 O + multicomponent Coulomb crystals analysed using Timepix3, compared against the trapped ion structures obtained from CCD images and Coulomb crystal molecular dynamics simulations. Through analysis of the electric fields and ion trajectories using SIMION, the Timepix3 detection technique enables direct observation of fluorescent and non-fluorescent ions with Coulomb crystals. In addition, comparison of SIMION and experimental measurements highlighted how different trapping parameters, ejection fields and crystal sizes all affect ion flights and positions on the detector. Of particular note is of the effect of ejection fields, where the method of transfer from trapping to repeller and extractor fields can strongly influence the spatial distribution of the ions on the detector. In summary, we have used a combination of complementary detection methods to probe the spatial distribution of different ionic species in ejected Coulomb crystals. These findings are important, as non-laser-cooled species cannot be directly observed with a CCD camera. References 1. B. R. Heazlewood, & H. J. Lewandowski., “Chemistry Using Coulomb Crystals. Emerging Trends in Chemical Applications of Lasers” 389-410 (2021) 2. A. Tsikritea et al., “Charge transfer reactions between water isotopologues and Kr+ ions” ACS Physical Chemistry Au, 2, 3, 199-205 (2022) 3. T. Poikela., “Timepix3: a 65K channel hybrid pixel readout chip with simultaneous ToA/ToT and sparse readout” Journal of instrumentation, 9, 05, C05013 (2014)
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