Robert S. Van Dyck

Stable voltage source for Penning trap experiments

A voltage reference has been developed to bias ring electrodes of two Penning traps between -90 and 0 V. For output voltages near -90 V, the Allan deviation of the systems voltage instability is less than 1 part in 10(8) over all time scales shorter than 10(4) s. For averaging times longer than several seconds, the systems stability is determined almost completely by the noise, drift, and aging of the zener diodes in the array of voltage reference integrated circuits. For shorter averaging times, active filters built into the new system significantly reduce the intrinsic noise of the zener diodes. The system makes it possible to continuously adjust the ring voltages for frequency locking the axial motion in the two Penning traps. By keeping electrical noise highly correlated between the two traps, measurement uncertainty should be reduced for precision experiments such as Penning trap mass spectrometry.

Experiments with Single Electrons

A basic description of past geonium experiments is given and the modifications which allow positron geonium to be formed is described. The use of compensated Penning traps produces a harmonic axial frequency which has a resolution of 10 ppb. By using synchronous detection and a magnetic bottle for coupling, the magnetic resonances become observable. Stability of the radial position in this magnetic bottle is provided by motional (magnetron) sideband cooling. The corresponding magnetic line shapes are primarily determined by the Brownian statistical (axial) motion through this bottle. Finally the beat-note between the nearly degenerate cyclotron and spin precession frequencies defines the anomaly resonance and its value can be determined to ~1 ppb statistical precision by fitting to the noise-modulated Brownian lineshape. Present accuracy has produced the most precise determination of the α−1(QED) and the positron/electron g-factor comparison. Results of new measurements using a phosphor bronze trap are also described which show consistency with previous results using all-molybdenum traps.

High Resolution Penning Trap as a Precision Mass-Ratio Spectrometer

The compensated Penning trap1 with characteristic dimensions RO and ZO is a D.C. electric potential cage located in a strong axial magnetic field and as such is an ideal apparatus for isolating long lived charged particles, nearly at rest (thermalized by a cryogenic environment) and essentially free of other-particle interactions (due to the ultra-high vacuum used, ≪10-10 Torr). The ability to determine mass arises from the inverse mass dependence of the various motions in the trap. The first such motion is the axial electric resonance (motion along axis of symmetry) at

Practical positron catching in a Penning trap

{v_{z}} = (1/2\pi ){(e{V_{0}}/mZ_{0}^{2})^{{\frac{1}{2}}}}

Determination of the electron's atomic mass and the proton/electron mass ratio via Penning trap mass spectroscopy.

which is often used to monitor the presence of the trapped charge, but is only appropriate for very low precision mass measurements since the effective applied D.C. potential, VO will often depend on parameters which are difficult to control (i.e. thermal emf’, contact potentials, patch effects, time varying dimensions, dielectric polarization, unstable power supply, etc.). In contrast to the axial resonance, the magnetic cyclotron frequency at

Progress with the MPIK/UW-PTMS in Heidelberg

{v_{c}} = (1/2\pi )(e{B_{0}}/mc)