S. Djekic

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

Abstract 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.

Determination of the electron’s mass from g-factor experiments on 12C5+ and 16O7+

Abstract We present a derivation of the electron’s mass from our experiment on the electronic g factor in 12C5+ and 16O7+ together with the most recent quantum electrodynamical predictions. The value obtained from 12C5+ is me=0.0005485799093(3) u, that from oxygen is me=0.0005485799092(5) u. Both values agree with the currently accepted one within 1.5 standard deviations but are four respectively two-and-a-half times more precise. The contributions to the uncertainties of our values and perspectives for the determination of the fine-structure constant α by an experiment on the bound-electron g factor are discussed.

Precision studies in traps: Measurement of fundamental constants and tests of fundamental theories

Experiments on single atomic particles confined in Penning ion traps have contributed significantly to the improvements of fundamental constants and to tests of the theory of Quantum Electrodynamics for free and bound electrons. The most precise value of the fine structure constant as well as the electron mass have been derived from trap experiments. Numerous atomic masses of interest for fundamental questions have been determined with precisions of 10 � 9 or below. Further progress is envisaged in the near future.

The magnetic moment anomaly of the electron bound in hydrogen-like oxygen 16O7+

The measurement of the g-factor of the electron bound in a hydrogen-like ion is a high-accuracy test of the theory of quantum electrodynamics (QED) in strong fields. Here we report on the measurement of the g-factor of the bound electron in hydrogen-like oxygen (16O7+). In our experiment a single highly charged ion is stored in a Penning trap. The electronic spin state of the ion is monitored via the continuous Stern?Gerlach effect in a quantum non-demolition measurement. Quantum jumps between the two spin states (spin up and spin down) are induced by a microwave field at the spin precession frequency of the bound electron. The g-factor of the bound electron is obtained by varying the microwave frequency and counting the number of spin flips. The comparison of our experimental values for the g-factor of the bound electron with the theoretical values shows excellent agreement and confirms the recent non-perturbative QED calculations.

Penning Trap Measurement of the Magnetic Moment of the Antiproton

The measurement of the magnetic moment (or g‐factor) of the antiproton and of the proton is a sensitive test of CPT invariance. In our experiment we will store and detect a single (anti)proton in a cryogenic Penning trap. The g‐factor will be measured by detection of quantum jumps via the continuous Stern‐Gerlach effect. Most of the experimental techniques to be used have been already successfully employed by our group for the measurement of the g‐factor of the bound electron in hydrogen‐like ions. However, the magnetic moment of the proton is smaller than that of the electron by a factor of 658. Our hybrid trap design combines cylindrical electrodes with a toroidal ferromagnetic ring electrode. With this novel trap, spin‐flip transitions of the (anti)proton can be detected by observation of tiny differences in the axial frequency by a phase‐sensitive method. With our apparatus, we envisage to determine the g‐factor of the (anti)proton with an accuracy of 10−9 or better.

Measurement of the g factor of the bound electron in hydrogen-like oxygen 16O7+

The measurement of the g factor of the electron bound in a hydrogen-like ion is a high- accuracy test of the theory of Quantum Electrodynamics (QED) in strong fields. Here we report on the measurement of the g factor of the bound electron in hydrogen-like oxygen 16 O 7+ . In our experiment a single 16 O 7+ ion is stored in a Penning trap. Quantum jumps between the two spin states (spin up and spin down) are induced by a microwave field at the spin precession frequency of the bound electron. The g factor of the bound electron is obtained by varying the microwave frequency and counting the number of spin flips. Our experimental value for the g factor of the bound electron is gexp( 16 O 7+ ) = 2.000 047 026(4). The theoretical prediction from non-perturbative bound-state QED calculations is gth( 16 O 7+ ) = 2.000 047 0202(6).