Department of Physics, Engineering Physics & Astronomy

Department of Physics, Engineering Physics & Astronomy
Department of Physics, Engineering Physics & Astronomy

On the Use of Penning Traps in Fundamental Physics

Ingmar Bergstrom
Swedish Academy of Sciences

Monday, September 18, 2006
10:30 AM @ Stirling 201


The 1989 Nobel Prize in Physics was awarded to Norman Ramsey, Wolfgang Paul and Hans Dehmelt. The trap that Dehmelt developed was inspired by a vacuum gauge invented by Penning who worked at the Dutch Philips company. In such a trap the spin flip frequency of free particles like the electron and proton can be measured as well as their cyclotron frequencies, which gives the g-factor. The g-factor is related to the fine structure constant, α, and can be determined with a very high accuracy. Dehmelt's pioneering measurement has recently been improved by a factor 6 by Gabrielse et al. The g-factor of bound electrons in hydrogen-like ions provides a further test of QED. This leads to a formula that includes the masses of such ions which we have determined in a few strategic cases. The Penning traps can also determine atomic masses with an accuracy in the region 10-9 to 10-11. There is now a great interest in the Q-values of the tritium beta decay and the 76Ge neutrinoless double beta decay. In the latter case the expected monochromatic electron peak is exactly given by the Q-value. Influenced by the planned experiments at SNO-lab we have measured the mass of 76Se25+ ions using Ramsey 3-pulse excitation and confirmed the old value with an improved accuracy by a factor 1.5. Since in a short time the 2006 Nobel prizes will be announced I shall comment on the prize procedure in the Swedish Academyof Sciences