Charge radii of neutron-deficient Ca isotopes*

Nucleon shell closures are generally associated with a local minimum in mean-square charge radii, $\left$, along an isotopic chain. The $\left$ of $_{18}$Ar and $_{19}$K isotopes, however, do not show this signature at the $N = 20$ neutron shell closure. To gain a microscopic understanding of this abnormal behavior, measurements of $\left$ of neutron-deficient Ca isotopes below $N = 20$ have been proposed at the BEam COoling and LAser spectroscopy (BECOLA) facility at NSCL/MSU. Preliminary results will be presented and the deduced charge radii will be compared to theoretical calculations and the trends in the nearby isotopic chains.