Towards a magnetic field stabilization at ISOLTRAP for high-accuracy mass measurements on exotic nuclides

The field stability of a mass spectrometer plays a crucial role in the accuracy of mass measurements. In the case of mass determination of short-lived nuclides with a Penning trap, major causes of fluctuations are temperature variations in the vicinity of the trap and pressure changes in the liquid helium cryostat of the superconducting magnet. Thus systems for the temperature and pressure stabilization of the Penning trap mass spectrometer ISOLTRAP at the ISOLDE facility at CERN have been installed. A reduction of the temperature and pressure fluctuations by at least an order of magnitude down to Δ T ≈ ± 5 mK and Δ p ≈ ± 5 Pa has been achieved, which corresponds to a relative magnetic field change of Δ B / B = 2.7 × 10 - 9 and 1.1 × 10 - 10 , respectively.