The Penning Trap
In a Penning trap charged particels (ions) can be stored with a superposition of a magnetic field and a static electric field. The magnetic field prevent the charged particel to escape perpendicular to the magnetic field lines (The ion travels on a cyclotron-like orbit). For the confinement in the direction of the magnetic field we apply voltages to electrodes and create so in this direction a minimum in the electrostatic potential.
The resulting ion motion can be described by three uncoupled harmonic oscillations (reduced cyclotron, axial, and magnetron oscillation):
the cyclotron oscillation: 24 MHz
the axial oscillation: 360 kHz
the magnetron oscillation: 2.5 kHz
The magnetic field is produced by a superconducting magnet (B=3.765T). The electric field is produced by a set of cylindrical electrodes:
For storing positive ions Uring has to be negative. We use the Voltage Ukorr to tune our trap, so that we archive a very hamonic potential (C4<10-6). The right picture shows a photograph of our trap(s): We use two traps of the type shown in the left picture. Therefore we can optimize the traps for different purposes (see the sketch below). One trap is equipped with a nickel-ring, which produces an inhomogeneity in the magnetic field. This enables us to detect spin-flips of the electron (respectively the ion). In the other trap the magnetic field is left homogeneous. This guaranties narrow linewidths of the Larmor- and the cyclotron-resonance.