XRF in Archaeology

X-ray fluorescence (XRF) spectrometry is a prevalent means of non-destructive elemental analysis in archaeology, the earth and environmental sciences, cultural heritage and museum studies, and other fields. A few universities have specialized “archaeological XRF laboratories” outfitted with a benchtop XRF spectrometer, vacuum pump or gas tanks, desktop computers, and support equipment in a dedicated space. We are fundamentally different.

The Yale Archaeological XRF ExoLab (YAXX) is not a laboratory in the traditional sense. That is, our XRF instruments are not restricted to a particular room on campus. Instead, we use portable XRF instruments that can analyze artifacts or other objects in our Archaeomaterials Suite or Clean Lab, across campus at the Peabody Museum or Yale University Art Gallery, on a mountainside, or in an archaeological field house on the opposite side of the world. We work outside (“exo-”) the lab – hence, an “exolab.” This eliminates shipping or exporting artifacts, soils, and other specimens, and it improves collaborations with our colleagues around the world, enabling us to better integrate chemical analysis into projects.

Director 

Dr. Ellery Frahm • 16+ years of X-ray spectrometry experience

Instrumentation

YAXX uses state-of-the-art Olympus “Vanta” portable XRF (pXRF) instruments. The VMR model has a Rh anode in a 4-W X-ray tube, which is capable of voltages up to 50 kV.  When operated in the “GeoChem” or “GeoChem REE” mode, the X-ray tube’s current and voltage vary in combination with built-in beam filters to better fluoresce the heavier and lighter parts of the periodic table. The characteristic X-rays are measured using a large-area silicon drift detector and Olympus’ new Axon technology, that is, ultra-low-noise signal-processing electronics that allow high count rates (>100,000 counts/sec) with excellent spectrum resolution (<140 eV). High count rates correspond to better repeatability, lower uncertainties, and shorter measurement times. This model has a built-in GPS receiver to automatically geo-tag measurements in the field, and a built-in barometer corrects for altitude and air density, which is particularly important when measuring light elements near sea level in New Haven or at a Peruvian archaeological site.

Logo

Yes, that is a yak in the YAXX logo – yaks, YAXX, get it? And, yes, it is carrying a portable XRF case on its back. For millennia, yaks have been important pack animals in alpine regions, transporting traders’ goods through mountain passes and climbers’ supplies for trekking expeditions. It is a fitting mascot for our endeavors to bring XRF instruments into the field.

Support

YAXX was founded in 2017 thanks to generous awards from the Anthropology Department and the Offices of the Vice Provost for Research, Dean of Science, and Dean of Social Science.