High-accurcay Penning trap mass measurements for nuclear structure and fundamental studies

Like few other parameters, the mass of an atom, and its inherent connection with the atomic and nuclear binding energy is a fundamental property, a unique fingerprint of the atomic nucleus. For short-lived exotic atomic nuclei the importance of its mass ranges from the verification of nuclear models, nucleosynthesis studies, to a test of the Standard Model, in particular with regard to the weak interaction and the unitarity of the Cabibbo-Kobayashi-Maskawa quark mixing matrix [1]. The introduction of Penning traps into the field of mass spectrometry has made this method a prime choice for high-accuracy measurements on short-lived and stable nuclides. This is reflected in the large number of traps in operation, under construction, or planned world-wide. With the development and application of proper cooling and detection methods the trapping technique has the potential to provide the highest sensitivity and accuracy, even for very short-lived nuclides far from stability. The limits of mass measurements of exotic nuclei have been extended considerably by improving and developing on-line Penning trap mass spectrometers as, e.g., CPT at Argonne, ISOLTRAP at ISOLDE/CERN, JYFLTRAP at IGISOL/Jyv\"askyl\"a, LEBIT at MSU/East Lansing, and SHIPTRAP at GSI/Darmstadt. The precise determination of nuclear binding energies far from stability includes nuclei that are produced at rates of 100 ions/s and with half-lives well below 100\,ms. The mass resolving power reaches $10^7$ and the uncertainty of the resulting mass values has been pushed down to below $10^{-8}$. The presentation will describe the basics and recent progress made in ion trapping, cooling, and detection for high-accuracy Penning trap mass measurements. Special attention is devoted to the applications of accurate mass values for nuclear structure and fundamental studies. [1] K. Blaum, Phys.Rep. 425 (2006) 1.