Cavity Control of a Single-Electron Quantum Cyclotron:\\Measuring the Electron Magnetic Moment

Measurements with a one-electron quantum cyclotron determine the electron magnetic moment, given by $g/2 = 1.001\,159\,652\,180\,73\,(28)\,[0.28~\textrm{ppt}]$, and the fine structure constant, $\alpha^{-1}=137.035\,999\,084\,(51)\,[0.37~\textrm{ppb}]$. Brief announcements of these measurements are supplemented here with a more complete description of the one-electron quantum cyclotron and the new measurement methods, a discussion of the cavity control of the radiation field, a summary of the analysis of the measurements, and a fuller discussion of the uncertainties

Reservoir spectroscopy of 5s5p 3^3P2_2 - 5snnd 3^3D1,2,3_{1,2,3} transitions in strontium

We perform spectroscopy on the optical dipole transitions 5s5p $^3$P$_2$ - 5s$n$d $^3$D$_{1,2,3}$, $n \in (5,6)$, for all stable isotopes of atomic strontium. We develop a new spectroscopy scheme, in which atoms in the metastable $^3$P$_2$ state are stored in a reservoir before being probed. The method presented here increases the attained precision and accuracy by two orders of magnitude compared to similar experiments performed in a magneto-optical trap or discharge. We show how the state distribution and velocity spread of atoms in the reservoir can be tailored to increase the spectroscopy performance. The absolute transition frequencies are measured with an accuracy of 2 MHz. The isotope shifts are given to within 200 kHz. We calculate the $A$ and $Q$ parameters for the hyperfine structure of the fermionic isotope at the MHz-level. Furthermore, we investigate the branching ratios of the $^3$D$_{J}$ states into the $^3$P$_{J}$ states and discuss immediate implications on schemes of optical pumping and fluorescence detection.Comment: 15 pages, 7 figures, 4 table

Gravitational wave astronomy

The first decade of the new millenium should see the first direct detections of gravitational waves. This will be a milestone for fundamental physics and it will open the new observational science of gravitational wave astronomy. But gravitational waves already play an important role in the modeling of astrophysical systems. I review here the present state of gravitational radiation theory in relativity and astrophysics, and I then look at the development of detector sensitivity over the next decade, both on the ground (such as LIGO) and in space (LISA). I review the sources of gravitational waves that are likely to play an important role in observations by first- and second-generation interferometers, including the astrophysical information that will come from these observations. The review covers some 10 decades of gravitational wave frequency, from the high-frequency normal modes of neutron stars down to the lowest frequencies observable from space. The discussion of sources includes recent developments regarding binary black holes, spinning neutron stars, and the stochastic background.Comment: 29 pages, 2 figures, as submitted for special millenium issue of Classical and Quantum Gravit

Development of a Digital Feedback System for Advanced Ion Manipulation Techniques within a Penning Trap

The high-precision Penning-trap mass spectrometer Pentatrap aims at measurements of mass ratios of highly charged ions with an uncertainty of a few parts in 10−12. Within the context of this thesis, the development of an active feedback system and its possible applications for the Pentatrap experiment are described. This system allows to electronically feed back the signal from the axial detection electronics to one or multiple electrodes of the Penning trap, enabling the implementation of advanced ion manipulation techniques. It was successfully used to cool the apparent temperature of the detection electronics below the 4.2 K environment of the trap setup, enabling the application of ion feedback cooling. Furthermore, the quality-factor and the center frequency of the resonator, used in the detection system, was shown to be modified by coupling the feedback signal to the resonator. The feedback system was implemented using a novel concept, making use of real-time digital processing algorithms on an FPGA. This leads to very stable feedback operation and allows for highly dynamic variation of the feedback parameters, opening the possibility for new measurement schemes. A phase-sensitive measurements technique for the axial frequency was successfully implemented and tested, which inherently has the potential to achieve better accuracy compared to the commonly used axial dip detection. Additionally, a single-ion self-excited oscillator was realized, enabling the determination of the axial frequency at very high repetition rates. As the precision of the Pentatrap experiment is currently mainly limited by the uncertainty of the axial frequency measurement, the feedback system developed in this thesis will directly contribute to improving the precision of the mass measurements