Penning Trap (IMAGE) Helmholtz Association Caption The picture shows the Penning trap, which is part of the Shiptrap experiment. A magnetic field parallel to the tube forces the arriving ions onto a spiral course inside the tube. The ions' spiraling frequency is used to directly calculate their atomic mass. The Penning trap is located inside the white tank that can be seen in picture 1. Credit G. Otto, GSI Helmholtzzentrum für Schwerionenforschung Usage Restrictions May be used for all noncommercial releases. Please credit the photographer. License Licensed content Disclaimer: AAAS and EurekAlert! are not responsible for the accuracy of news releases posted to EurekAlert! by contributing institutions or for the use of any information through the EurekAlert system.