<p>Lots of evidence, some priceless, has gone up in smoke at the University of Arizona since April 26, 1982. <br /><br />That's when the National Science Foundation - Arizona Accelerator Mass Spectrometry (AMS) Lab officially dated its first sample by the radiocarbon dating technique. <br /><br />On Thursday, April 26 -- exactly a quarter-century and roughly 75,000 radiocarbon measurements later -- more than 100 scientists will celebrate the pioneering facility's 25th anniversary with a mini workshop and reception at the Westward Look Resort, 245 E. Ina Road. The workshop and reception are open by invitation only. <br /><br />In the radiocarbon dating technique, researchers burn the sample and convert the carbon dioxide given off by combustion to graphite. They use a huge machine, the accelerator mass spectrometer, to measure how much radioactive carbon, or carbon 14, is present in the graphite sample. Radioactive carbon decays at a known rate, giving scientists the object's radiocarbon age. They convert radiocarbon years to known calendar years by using the calibrated tree-ring record.<br /><br />Among the most publicized individual objects dated at the UA lab are the Shroud of Turin, the Vinland Map, the Dead Sea Scrolls, the Gospel of Judas. <br /><br /> </p><p> But the bulk of the lab's work is in geosciences, said Professor and AMS Lab Director A. J. Tim Jull. "Sediments and oceanographic samples, followed by anthropological and archaeological samples, are most of what we date," Jull said. He was one of three who initially staffed the lab in 1982.<br /><br />The facility now has the capability to study a wide range of climatic, geologic and archaeological records using three other isotopes, beryllium 10, aluminum 26 and iodine 129, as well as carbon 14. The laboratory is jointly run by the UA geosciences and physics departments.In 2005, the Arizona AMS Lab dated objects for 265 scientists from more than 100 universities, 27 government laboratories and dozens of museums in the United States and abroad. <br /><br />UA scientists on the lab's staff of 20 rely on the facility for their research on ocean corals, cave deposits, lake sediments and, increasingly, in tracing groundwater supplies. Some of the earliest dating was done for air pollution studies, Jull said. Future projects might include tracing nuclear materials for homeland security reasons, he added. <br /><br /> </p><p> Not the least of its mission, the Arizona AMS Lab is an educational training ground for students and scientists. The Arizona lab's student education and public outreach mission sets it apart from the commercial laboratories that aim to provide analyses for profit, Jull said. For many years the Arizona AMS Facility has run a student intern program which provides free, hands-on training for graduate students doing research. The lab has also trained scientists from all over the world. As a result, places like China and Eastern Europe have recently established their own new isotope dating facilities, Jull added.<br /><br />Scientists scheduled to talk at the 1 p.m. - 4 p.m. mini workshop include: <ul><li>A.J. Tim Jull and College of Science Dean Joaquin Ruiz, welcome and opening remarks</li><br /><li>UA physics Professor Emeritus Douglas J. Donahue, co-founding director of the Arizona AMS Lab, "A brief review of 25 years of AMS and remembrance of AMS colleagues"</li><br /><li>Walter Kutschera, University of Vienna, "Carbon 14 - a unique gift of nature"</li><br /><li>Lloyd Currie, National Institute of Standards and Technology, Gaithersburg, M.D., "Early measurements of C14 using AMS"</li><br /><li>Wolfgang Kretschmer, University of Nurnberg, Erlangen, "AMS measurements of microgram samples"</li><br /><li>Devindra Lal, University of California, San Diego, "Deconvolution of the atmospheric radiocarbon record in the last 50,000 years"</li><br /><br /></ul><br /></p><p><br /></p>