Progress towards a high-precision measurement of the g-factor of a single, isolated (anti)proton in a double Penning trap
Susanne Kreim (Universität Mainz)

Determining the g-factor of a single, isolated proton in a double Penning trap results from an accurate measurement of its cyclotron and spin precession frequency. This frequency can be determined by inducing radio-frequency transitions between the two spin states in the homogeneous magnetic field region of the first, precision Penning trap. The resulting spin state is detected in another region, namely the magnetic bottle field of the analysis trap. There, the spin direction is monitored by measuring the respective axial frequency shift via the continuous Stern-Gerlach effect. A novel trap design was developed which we call hybrid Penning trap to increase the axial frequency jump to a detectable range.
To achieve a high-precision measurement, the experiment is performed in a 4K cryogenic environment providing an ultra-high vacuum as well as long storage times of the particle.
This environment bears great challenges for the electronics needed to non-destructively detect the trapped proton, however, it leads to a low electronic noise. In addition, the use of superconducting resonant circuits increases the signal-to-noise ratio of the detection system by some orders of magnitude. Since the sealed system requires an in-trap creation of protons, a newly developed cryogenic electron gun will function as an electron beam ion source permitting the creation of protons inside the magnetic field and at 4K.
Commissioning experiments will be presented.