Idaho Accelerator Center
Image Credit: ISU Photographic Services

ZAP!

Idaho Accelerator Center Tracking Ancient Tools' Origins

© Idaho State Journal
Reprinted with permission

Idaho State University anthropologists are retracing American Indian trade routes by zapping arrowheads and other stone tools with radiation at the Idaho Accelerator Center.

The process, called photon activation analysis, allows researchers to measure trace elements in the objects and use the data to match the artifacts with their places of origin.

Herb Maschner, Ph.D., an ISU anthropology professor, said while the same results can be gained by drilling holes into the artifacts and irradiating them inside nuclear reactors, they have to be treated as radioactive waste afterward. An important aspect of photo activation is that it causes no damage.

"This is the only accelerator center in the world doing this kind of work," Maschner said.

The collaboration between the Idaho State University physics and anthropology departments began more than two years ago.

Maschner wanted to trace the origins of the artifacts found by anthropologists and tribal members in the Aleutian Islands, where Maschner studies indigenous people and their history. The former director of the accelerator center, Frank Harmon, Ph.D., contacted Maschner and said he had a technique that could work without destroying the objects.

German scientist Christian Segebade pioneered the technology in the 1970s and 1980s to authenticate medieval armor and swords.

Doug Wells, Ph.D., the accelerator center's current director, said the technology has a wide variety of possible applications, ranging from analyzing water for lead content to authenticating art.

Maschner and Harmon began their project by irradiating rocks to see if they could get an elemental fingerprint. The experiment worked as planned. Since then, the process has been fine-tuned and quality controls have been added.

Maschner's assistant, master's degree student Buck Benson, said they know the obsidian the arrowheads are made of came from particular volcanoes in Alaska, but they are still trying to figure out which arrowheads correspond with which volcanoes.

He said they have experimented with samples from the lava flows in southeastern Idaho because of their proximity to the accelerator center. The researchers can now accurately match the samples to particular flows.

"We're trying to get to that point in Alaska," Benson said. Physics doctoral student Jaromy Green is assisting with the project.

The project uses a medical-grade accelerator designed for cancer therapy. It shoots 25 million volts of electricity into a block that converts the current into gamma rays before it passes through the stone artifacts, which rotate in small containers on a turntable for a period of four hours.

"It changes the composition slightly to make them radioactive so we can measure the elements," Masher said.

Afterward, the objects are set aside for a few days until they are radiation free. They can then be returned to the tribes.

Maschner said the technique, which is accurate enough to detect trace elements in concentrations as low as a few parts per billion, could also be used on Native American pottery.

Casey Santee
Idaho State Journal