Motional frequency spectroscopy in a Penning trap via a single laser-cooled ion

Résumé

This thesis reports on the use of laser cooling and manipulation techniques for the determination of the motional frequencies in a Penning trap. The optical detection of the motional state of the system has the advantages of being universal, demanding only one ion of interest, and being robust against imperfections of the trapping fields. In this work, the first experimental results, as well as several technical improvements are presented: a novel optical system, a customized cryogenic pump, and two ion sources. 40Ca+ has been characterized as a radiofrequency detector at the Doppler limit, developing a laser-pulsed measurement protocol to read out the ion’s oscillation amplitude from an EMCCD and a PMT. The alternating determination of the cyclotron frequency of two individual calcium isotope ions (40Ca+ vs ACa+ with A = 42, 44, 48) has yielded the first mass ratio measurements of the optical method. Experiments on balanced (40Ca+ - 40Ca+) and unbalanced (42Ca+ - 40Ca+) Coulomb crystals have been used to study the validity of the generalized invariance theorem. These measurements constitute the first implementation of the method on a universal platform. To bring the accuracy of the technique to a competitive level, it will be necessary to cool the crystal down to its ground state of motion.