First Ramsey-type mass measurements with ISOLTRAP and design studies of the new PENTATRAP project

The application of Penning traps for mass spectrometry has led to a major step in the mass precision. Consequently, atomic masses became more and more important as input parameters in different research fields. This exploitation is still ongoing in line with a steady development of Penning trap mass spectrometers to even higher accuracies. Penning trap mass spectrometry is based on the determination of the free cyclotron frequency νc = qB/(2πm) of an ion confined in a homogeneous magnetic field B. In principle two different measurement techniques are available: By applying the destructive time-of-flight detection method (TOF-ICR) the trap content is lost after the measurement. Since it is a fast measurement method it is usually used for mass determinations of short-lived radionuclides, whereas a relative mass uncertainty δm/m of a few parts in 10−9 is routinely reached even for nuclides with half-lives well below 500ms. This has been achieved by the implementation of the Ramsey method in Penning trap mass spectrometry within this work. By contrast the non-destructive Fourier Transform-Ion Cyclotron Resonance detection method (FT-ICR) determines the frequency of the image current introduced in the trap electrodes by the ion motion. Thus, the ion remains in the trap and can be used for further measurement cycles. This method is often applied for measurements of stable nuclides reaching a relative mass uncertainty of less than δm/m = 10−11. One part of this thesis was the application of time-separated oscillatory fields, called Ramsey method, for resonant ion motion excitation in order to improve the time-of- flight detection method. It was used to measure the nuclides 26,27Al and 38,39Ca with the Penning trap mass spectrometer ISOLTRAP. The mass values have been included in the “Atomic Mass Evaluation” (AME). Furthermore, the nuclides 26Al and 38Ca serve as input parameters for stringent tests of the Standard Model. Additionally, damping effects in a Penning trap due to collisions between trapped ions and residual gas atoms as well as their impact on the time-of-flight detection method have been extensively investigated. To exploit precise mass values to test fundamental symmetries or to study quantum electrodynamics (QED) in extreme fields a new Penning trap project (PENTATRAP) for mass measurements on highly-charged ions has recently been started. The main contribution within this thesis was the design of the Penning traps. For the first time so called “monitor traps” has been developed in order to observe permanently the magnetic field B and its time-dependent fluctuations