High-precision mass measurements of neutron-deficient Tl isotopes at ISOLTRAP and the development of an ultra-stable voltage source for the PENTATRAP experiment

Atomic masses and hence binding energies of nuclides are of great importance for studies of nuclear structure since they reflect all effective interactions in a nucleus. Within this thesis the masses of seven nuclides, namely ¹⁹⁴Au, ¹⁹⁴Hg, ^190,193,198Tl and ^202,208Pb, were determined at the Penning-trap mass spectrometer ISOLTRAP at ISOLDE/CERN. The thallium region in the chart of isotopes is of special interest due to the occurrence of nuclear structure effects like low-lying isomers, level inversion, shape coexistence and deformations. These effects are investigated by applying finite-difference mass formulas, such as the two-neutron separation energies or the so-called empirical pairing gaps. The second topic addressed within the present thesis is an ultra-stable voltage source, called StaReP (Stable Reference for Penning Trap Experiments), which was developed at the Max-Planck-Institut f¨ur Kernphysik. It is one of the key components of the high-precision mass spectrometer PENTATRAP, containing a tower of five Penning traps. A 25-channel voltage source with a relative stability of few 10⁻⁸ over a period of 10 minutes in the range of 0 to −100V is mandatory for PENTATRAP aiming for mass measurements with relative mass uncertainties of ≤ 10⁻¹¹. Mass values with such a high precision allow for stringent tests of quantum electrodynamics in strong electric fields, testing Einstein’s mass-energy relation E = mc² as well as measurements of decay energies (Q-values) with applications in neutrino physic