1 MV Tandetron - Accelerator Mass Spectrometry (AMS)

1 MV Tandetron

Accelerator Mass Spectrometry (AMS) is today's most sensitive isotopic analysis method known. Using a particle accelerator, usually a Tandem type, the AMS spectrometer measures one by one the ions of the investigated species. This method uses a Tandem type accelerator due to its ability to break the molecules having the same mass as the analysed atom and thus remove the unwanted molecular interference from the measurement.

The AMS sensitivity can reach 10-15 scarce isotope / abundant isotope, in other words, AMS allows determination of the existence of a single atom in a torrent of one million billion other foreign atoms. So, AMS is an analytical technique for measuring low levels of long-lived radionuclides and rare trace elements. Due to its exceptional sensitivity, this method has opened a very wide range of applications in various fields: medicine, archaeology, palaeogeomorphology, geology, atmospheric physics, paleoclimatology, astrophysics, nuclear physics, nuclear pollution tracking, etc.

1MV TANDETRON accelerator now allows the applications using the following isotopes: 10Be, 14C, 26Al, 41Ca, 129I. Also, measurements of 2H and 3H are performed routinely at the AMS facility from 9MV tandem accelerator at IFIN-HH. A specialized chemistry laboratory performs the samples preparation for all AMS analysis.

1 MV Tandetron
What is AMS?

Accelerator Mass Spectrometry (AMS) is a technique for measuring long-lived radionuclides that occur naturally or anthropogenically in our environment. AMS uses a particle accelerator in conjunction with ion sources, large magnets, and detectors to separate out interferences and count single atoms in the presence of 1x1015 (a thousand million million) stable atoms. At RoAMS we measure different cosmogenic and anthropogenic radionuclides (14C, 10Be, 26Al, 129I, 239,240Pu). They are used for a wide variety of dating and tracing applications in the geological and planetary sciences, archaeology, and biomedicine.

Cs sputtering ion source with 50 samples carousel
Cs sputtering ion source with 50 samples carousel

The ion source produces a beam of ions (with -1 electrical charge) from a few milligrams of solid material. Atoms are sputtered from the sample by 133Cs ions which are produced on a hot spherical ionizer. Very few samples are directly measured into the AMS spectrometer, usually they have to suffer a chemical pre-treatment and conversion into graphite. In case of 14C, the CO2 from the solid/liquid sample is converted into graphite after a combustion or digestion into a specific apparatus, function of the sample type. We have two 50 samples ion sources, one dedicated only to radiocarbon dating and the second for the other isotopes. Negative ions produced on the surface of the sample are extracted from the ion source and sent downstream to the first electrostatic analyser (ESA).

1 MV Cockroft-Walton Tandetron Accelerator

This is a type of electrostatic linear accelerator that accelerates ions in a uniform electrostatic field with a maximum electric potential of +1MV supplied by a Cockroft-Walton high voltage generator. In a Tandem system the high positive potential is applied to a central electrode in the middle of the accelerator tank. Negative ions are injected into the accelerator and gain energy towards the middle positive potential. Arriving here, negative ions are stripped of electrons by collisions with a stripping gas (argon) and turn positive. Once positive they are further pushed by the high positive potential and exit the accelerator, gaining energy function of their charge state.

Find more on RO-AMS website