Second generation measurement of the electric dipole moment of the electron using trapped ThF$^+$ ions

ThF$^+$ has been chosen as the candidate for a second generation measurement of the electric dipole moment of the electron (eEDM). Compared to the current HfF$^+$ eEDM experiment, ThF$^+$ has several advantages: (i) the eEDM--sensitive state ($^3\Delta_1$) is the ground state, which facilitates a long coherence time\footnote{D. N. Gresh, K. C. Cossel, Y. Zhou, J. Ye, E. A. Cornell, Journal of Molecular Spectroscopy, 319 (2016), 1-9}; (ii) its effective electric field (38 GV/cm) is 50\% larger than that of HfF$^+$, which promises a direct increase of the eEDM sensitivity\footnote{T. Fleig, M. K. Nayak, Physical Review A 88 (2013) 032514}; and (iii) the ionization energy of neutral ThF is lower than its dissociation energy, which introduces greater flexibility in rotational state--selective photoionization via core--nonpenetrating Rydberg states\footnote{Z. J. Jakubek, R. W. Field, Journal of Molecular Spectroscopy 205 (2001) 197–220.}. Here, we present progress of our experimental setup, preliminary spectroscopic data of multi--photon ionization, and discussions of new features in ion trapping, state preparation and population readout.