Evolution of isotropic and anisotropic spatial distribution of large ion clouds during the onset of quasi state equilibrium condition in a Paul trap

A study of variation of large ion cloud spatial density distribution with the applied potential, in a three dimensional (3-d) Paul trap has been conducted. Large ion clouds (ion numbers >106) have been trapped using a combination of static field (DC) and radiofrequency (RF) electric fields and are cooled using buffer gas. Laser scanning across the trap in the x and z directions yielded the spatial density distribution at different applied trap potential well depths. The spatial density distribution of the ion cloud exhibited a good Gaussian fit for all the three set of operating parameters chosen, enabling the study of a near; spherical, oblate and prolate distributions. Using Monte Carlo code theoretical simulations for 1000 ions were carried out and the spatial density distribution of the ion cloud is compared with the experimental values.

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► We report experimental and theoretical work on spatial distribution of ion cloud.
► Near; spherical, oblate and prolate ion cloud distributions is observed.
► Shrinking of the size of ion cloud is observed with time due to loss of ions.
► In a non quasi stationary state the distribution is observed to be nearly isotropic.
► True shape of the ion cloud is realized for less number of ions.