Ulmer Initiative Research Unit

Initiative Research Scientist

Stefan Ulmer

  • Ph.D.
  • Stefan Ulmer
  • Brief resume
    Physics Department, Doctoral Studies, Ruprecht-Karls University of Heidelberg, Germany
    Foreign Postdoctoral Researcher, Atomic Physics Laboratory, RIKEN
    Initiative Research Scientist, Ulmer Initiative Research Unit, RIKEN


Ulmer Initiative Research Unit

We are developing an experiment for the high-precision determination of the magnetic moment of the proton and the antiproton. The magnetic moment of the antiproton is currently known at a level of only 10-3. We are aiming at a millionfold improved measurement of this fundamental quantity.

To this end we set up a new apparatus, where a single antiproton will be stored in a cryogenic double Penning trap for arbitrarily long time. Performing quantum-jump spectroscopy by application of the continuous Stern-Gerlach effect, the magnetic moment of the particle can be determined with high precision.

Recently we observed spin flips with a single trapped proton, which is an important milestone towards this challenging aim. Based on that success the magnetic moment of the particle was determined with a relative precision of 8x10-6. Thus, applying our technique to the antiproton would improve the number by two orders of magnitude already. Experimental efforts for an improvement of our technique towards 10-9 are under way.

In addition to this main project, we are involved in the ASACUSA-CUSP trap experiment, which aims at a high precision measurement of the antihydrogen hyperfine structure. Furthermore we contribute highly sensitive detection systems to several storage ring and Penning trap experiments.

Selected Publications

  1. S. Ulmer, et al. Direct Measurement of the Free Cyclotron Frequency of a Single Particle in a Penning Trap, Phys. Rev. Lett. 2011, 107, 103002.
  2. S. Ulmer, et al. Observation of spin flips with a single trapped proton, Phys. Rev. Lett. 2011, 106, 253001.
  3. S. Ulmer, et al. The quality factor of a superconducting rf resonator in a magnetic field, Phys. Rev. Lett. 2009, 80, 123302.

Core Members

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