Nuclear Engineering Grad Student Builds Analysis Facility

Story Posted: Thu, Jan 22, 2009

At first glance, the Robinson farm in Cave Junction looks pretty much like what you would expect: barns, tractors, sheep and cattle. But look closer and you'll see it's a bit more interesting than your typical family farm.

Farmer Robinson is a PhD chemist and one of the barns houses a Fourier transform mass spectrometry facility. In another barn are thousands of Geiger counters and radiation meters -- more than 10,000 of them.

So it's not too surprising that Robinson's son, Joshua, is a graduate student in nuclear engineering at OSU.

Working on his master's thesis, Robinson has designed and built a Prompt Gamma Activation Analysis facility at the OSU Triga Reactor. "I had close guidance and help from [former OSU professor] Dr. Hartman," says Robinson.

Prompt gamma activation analysis (PGAA) is used to determine the presence and quantity of boron, hydrogen, carbon, or other trace elements that are difficult to detect with other analytic methods. In PGAA, isotopes are subjected to a neutron beam resulting in the formation of an unstable compound nucleus. The nucleus immediately decays producing a series of gamma rays, whose energies are distinctive to each element. Robinson's PGAA utilizes a high purity germanium detector to measure the gamma rays emitted from a sample.

Unlike other analysis methods, the PGAA changes the sample so slightly it is insignificant in most cases. That makes it especially valuable to scientists working with rare samples. For example, an archeologist can study the chemistry of ancient pottery shards without damaging them.

Robinson and Hartman plan to adapt the facility to do Neutron Depth Profiling (NDP), a process which measures the concentration of elements as a function of depth. One possible application for NDP is to test the quality of semiconductors by measuring for uniform depth in boron layers.

With plans to pursue a PhD, Robinson still goes home occasionally to help out on the farm. "They need the help," he says, "and I enjoy working with my family." The 10,000 Geiger counters and radiation meters are still in the barn. "Most of them are owned by the State of Oregon," says Robinson, "My dad worked in Civil Defense and he offered to store them for the state."