An overview of our experimental setup is shown in Figure 4.1.
The system consists of two main parts. The external ion source (top) and the two hyperbolic Penning traps (bottom). In the ion source, the 3He- or 3H-gas is ionized by collisions with electrons emitted from a cathode filament. The ions then travel through the ion optics (see Figure 4.2) to the Penning trap section.
The ion cloud is stored above the hyperbolic Penning traps (see Figure 4.1) in the ion
capture segment. There, it is trapped by the magnetic field and an additional electric
potential. When the electric potential is reduced for a short time, parts of the ion cloud
reach the first hyperbolic trap, called capture trap (see Figure 4.4). (Further information
can be found in Marius Tremer's diploma thesis .)
The hyperbolic Penning traps are located in a superconducting 6 T magnet and are cooled by liquid helium to a temperature of 4 K. Due to manufacturing tolerances, holes in the endcaps for ion injection and truncated size electrodes, they slightly deviate from the ideal shape (see Figures 3.1 and 4.3).
In addition the ring- and endcap-electrodes, there are two correction electrodes, which are intended to tune anharmonicities and are used for exciting the ion with radiofrequency electric fields.
Actually, even one hyperbolic Penning trap would suffice for the measurement of a mass ratio of two ions, because two ions can be stored easily in a Penning trap. But in this case, the two charged particles interact with each other and thus interfere with the measurement. Therefore, it is advantageous to store one ion in the upper trap, while the frequency of the other ion is measured in the precision trap (see figure 4.4). In addition, the ion in the upper trap can be used to monitor fluctuations of the magnetic field or the ring voltage. A fast exchange of the ions reduces the effect of long-term fluctuations of the electric and magnetic field.