skip to content

Faculty of Mathematics and Natural SciencesInstitute for Nuclear Physics

6 MV Tandetron AMS unit

graphic slider element

  • How it all begins

    The prepared sample to be measured using AMS is placed in such “targets” (usually made of aluminum or copper).

  • Gaseous samples

    Sometimes it is necessary to measure gaseous AMS samples. For example, it is possible to determine the age of carbon dioxide samples from the permafrost and learn a lot about the Earth's climate history.

  • Ion sources

    In the ion sources, the atoms are released from the targets and an ion beam is formed. An initial selection by atomic mass takes place in a magnet.

  • Accelerator tank

    The ion beam is now guided into the actual accelerator. The tank is filled with sulphur hexafluoride to prevent electric flashovers.

  • Velocity!

    The accelerator is charged to a voltage of up to 6 million volts. This accelerates the atoms to high speeds. In the middle of the accelerator there is a thin foil which strips some of the electrons from the particles and thus “recharges” them. Interfering molecules are also destroyed in the process.

  • The large magnet

    The actual separation of particles by mass takes place in this strong electromagnet.

  • Electrostatic deflectors

    In these modules, the particles are now also selected according to velocity and the ion beam now contains almost only the desired isotope, e.g. carbon-14.

  • Finally at the finish line!

    At the end of the system there are detectors with which the incoming particles can be counted and identified atom by atom.

The 6 MV Tandetron accelerator was built by High Voltage Engineering Europe B. V., Amersfoort, Netherlands. The machine was fully built and tested in Amersfoort before being transported to Cologne.

The accelerator mass spectrometer is built in such a way that both the cosmogenic nuclides(10Be, 14C, 26Al, 36Cl, 41Ca and 129I) and the heavy nuclides 239Pu and 244Pu can be measured.

The accelerator system has two identical ion sources (SO110), each of which can be loaded with 200 samples. While one is used for measurements of solid samples, the second source is connected to a gas handling system and focuses on the measurement of CO2 samples. After the ions are accelerated from the source, they pass through a 54° electrostatic analyzer (ESA) and a 90° magnet for low-energy mass separation. The molecules are then destroyed by the so-called stripping process (either gas or foil stripper) in the accelerator. This 6 MV TANDETRON accelerator is the central element of the mass spectrometer, followed by a 90° switching magnet as a filter element, which is also designed for heavy ions such as 239Pu and 244Pu. The stable isotopes are measured in the following offset Faraday cups. After passing through further electrical filter elements, the rare or unstable isotopes are identified and counted in the detector system, e.g. gas ionization detector.