UA's Second AMS Is Up and Running

Rene Siqueiros
Oct. 11, 2000


After two years in the making, the second Accelerator Mass Spectrometer at the University of Arizona is in full swing.

The AMS machine, which was funded by a $1.3 million grant from the National Science Foundation in 1998, is now being used to plunge into the backlog of samples which have been sent for radiocarbon analysis to the NSF-Arizona AMS Laboratory. The lab is a joint facility of the UA departments of physics and geosciences.

"People send samples from all over the world for us to analyze, so we have a reasonable backlog of samples that we're working with," said Douglas Donahue, UA professor emeritus of physics and the lab's director. Applications for the dating technique range from art, history, archaeology and geology to environmental science and space science.

An AMS machine allows scientists to date once-living material such as charcoal, wood, textiles, tissue and bone, and other organic matter by using the radioactive isotope of carbon, carbon-14. All living organisms participate in the carbon cycle. When they die, they no longer add carbon to their tissues. Scientists can precisely measure how much radioactive carbon remains in a sample and, based on the known rate of carbon-14 decay, can determine when an organism lived.

The new machine, intended to complement an older AMS machine at the UA, will expand the lab's research capabilities by allowing scientists to work with other chemical isotopes such as beryllium-10, aluminum-26, and iodine-129 in their dating of samples. These isotopes are produced in the atmosphere and are tracers for various geophysical and cosmic events such as ocean cycles, paleomagnetic-field variations, and solar activities, Donahue said.

The AMS lab has garnered international attention for the university with its dating of the Shroud of Turin and the Dead Sea Scrolls.

The new AMS machine was delivered to the university's Physics and Atmospheric Sciences (PAS) Building in February. It was up and running by May, Donahue said.


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