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Specialized microscope aids in research and teaching

Robert Horton

Professor Robert Horton has
used the scanning electron
microscope to study west-central
San Joaquin Valley oil reservoirs.

It’s helping one student find the source of obsidian tools and deciphering trade routes among ancient Native Americans.

One professor is using it to investigate the types of foods being eaten by prehistoric peoples by studying the micro wear on the chewing surfaces of human teeth.

Another professor is using it to examine petroleum-bearing rocks, and yet another is studying sediments from Kern County’s groundwater aquifers.

CSUB’s Hitachi S-3400 variable pressure scanning electron microscope, or SEM, has such sophisticated capabilities it is able to view objects or structures as small as 50 nanometers. A nanometer is one-billionth of a meter. “To get an idea how small 50 nanometers is, a human hair has a diameter of around 100 micrometers, or about 2,000 times as large,” explained Dirk Baron, geology professor.

The microscope is equipped with two detectors, an Oxford Inca energy dispersive X-ray spectrometer (EDS) and a Gitan ChromaCL live color cathodeluminescence (CL) imaging system. The EDS detector measures the elemental composition of samples and the CL detector shows subtle, otherwise invisible textures such as zonation in crystals.

CSUB was the first university in California to receive a live color cathode luminescence system.

Baron said because of the high cost, there are not many electron microscope laboratories. “The only other one in the Bakersfield area that I am aware of is in the Forensic Science Lab of the District Attorney’s office.

“There are two features that make our instruments special: First, normally samples for SEM analysis need to be completely dry. However, the variable pressure capability of our microscope also allows examination of samples that contain some moisture. This is useful for biological samples such as tissue or plant parts. Second, only very few electron microscopy labs have a live-time color cathode luminescence detector.”

The microscope has been a great tool in the classroom. In CSUB’s mineralogy classes students have used the imaging and microanalysis systems to study complex compositional zoning in carbonates and other minerals. Environmental geology students have looked at well samples from the Kern Water Bank to see how arsenic behaves in groundwater systems.

The instruments have been used for a number of research projects as well. Geology professor Robert Horton has used the SEM to study digenetic mineralogy and porosity development in west-central San Joaquin Valley oil reservoirs. Results of this study were included in a manuscript accepted for publication.

The SEM is assisting those outside the university as well, including researchers from the University of Calgary and Pomona College. Baron said CSUB also has several projects in collaboration with Chevron and the Kern Water Bank Authority.

The cost of the instruments was $230,000, which was funded through a grant from the U.S. Department of Defense to professors Horton, Baron and anthropology professor Robert Yohe.