Back to the line of stability. Chasing mass accuracies below 10-9 using a Penning trap and highly charged ions

The Stockholm Penning trap has been connected to an electron beam ion source named CRYSIS located at the Manne Siegbahn Laboratory. It is combined to a high-resolution isotope separator that can provide singly charged mass selected ions of practically any element. These ions are fed into CRYSIS where it is subject to a very intense electron beam with an energy of 10-20 keV. The mass of the neutral atom is obtained by adding the masses of the missing electrons and subtracting their binding energies. The results on some 16 mass determinations made at an uncertainty from 3 to 0.3 ppb are commented on. In these measurements the mass number varies from 1 to 204 and the ion charges from 1+ to 52+. New mass values are obtained for the 3H, 3He and 4He masses. We have confirmed the Manitoba measurements of the Q-value of the double beta-decay of 76Ge and their mass measurements of the masses of 198Hg and 204Hg reaching the higher accuracy that traps offer. At present the mass uncertainty limit is about 3 x 10-10 which is demonstrated by comparing our results with the most accurately measured masses by other groups. (orig.)