Accuracy studies with carbon clusters at the Penning trap mass spectrometer TRIGA-TRAP

Extensive cross-reference measurements of well-known frequency ratios using various sizes of carbon cluster ions 12 C n + (10≤n≤23) were performed to determine the effects limiting the accuracy of mass measurements at the Penning-trap facility TRIGA-TRAP. Two major contributions to the uncertainty of a mass measurement have been identified. Fluctuations of the magnetic field cause an uncertainty in the frequency ratio due to the required calibration by a reference ion of u f (ν ref )/ν ref = 6(2) × 10 -11 /min × Δt. A mass-dependent systematic shift of the frequency ratio of epsilon m (r)/r = -2.2(2) × 10 -9 × (m-m ref )/u has been found as well. Finally, the nuclide 197 Au was used as a cross-check since its mass is already known with an uncertainty of 0.6 keV.