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X-ray analyzer gun mounted in a holder with a rock sample sitting on the x-ray window.
X-ray Fluorescence Analyzer
X-ray Fluorescence Analyzer
It looks like a ray gun from an old-time sci-fi movie. I believe that was Bruker Technologies' intention. Their newest version of the Tracer portable XRF looks more like Thor's Hammer. The gun-shaped design was chosen because the XRF is meant to be taken out into the field for use. It's battery powered and has an old-timey PDA for an interface (for readers under 30, a PDA = Personal Data Assistant, which was like the computer function on your cell phone, but with limited wifi access to the internet).
We never got the PDA work well, so we've always used the system in a benchtop setup connected to a laptop. It wasn't what we'd hoped, but it's still been a fine tool.
Diagram of insides of the x-ray analyzer gun. An x-ray source generates x-rays that shine through a hole on the end of the gun. The x-rays interact with the sample, causing it to glow different color x-rays that shine down onto the x-ray detector. A computer in the main body of the gun counts the signal from the detector.
Liam Doyle did an outstanding research experiment studying ways to improve the accuracy of analyzing rock drill core with the XRF. I loved his creativity in problem-solving when figuring out ways to optimize the analytical protocol. He presented his results at the national Geological Society of America meeting in Seattle 2017.
A professional snow-boarder, Liam is also now a successful exploration geologist.
Vacuum - Analyzer - Computer
Vacuum - Analyzer - Computer
There are three components to the system.
XRF analyzer gun - this has an x-ray generating tube that shoots a very weak x-ray beam at the sample, then analyzes the types and amounts of x-rays that glow (fluoresce) from the sample. For elements on the periodic table that are lighter than aluminum (Z=13), the x-rays are too weak to pass through air. In most applications, being able to measure magnesium (12) and sodium (11) is important, so we have part 2:
Vacuum pump (to left of XRF analyzer gun in this image) that sucks the air out of the XRF gun so weak x-rays like those from magnesium and sodium can get to the detector. When users are only interested in detecting heavier elements (e.g., compositions of metal alloys), no vacuum is necessary.
Laptop computer that takes input from the XRF analyzer gun. The computer compares the intensity or brightness of each wavelength of x-ray glowing from the mystery sample with the measured intensities from other samples for which we know the concentrations of elements (called "standards"), and interprets the data from your mystery sample as concentrations.
X-ray spectrum = graph of the data
X-ray spectrum = graph of the data
The computer graphs the raw data as a "spectrograph" with the range (spectrum) of x-ray colors (energy levels measured in kiloelectron volts) on the horizontal axis, and the brightness (intensity measured in counts per second) on the vertical axis.
Each element on the periodic table glows (fluoresces) characteristic colors, so the spikes form a sort of chemical fingerprint. Each sample has a different chemical composition, so the XRF measures the characteristic fingerprint of each sample.
The Geology Club has plans to use our XRF to measure lead (Pb) in paint, dishes, toys, etc. as a public service. Our first trial run of the program examined some antique dishes I had (plenty of lead) and some glassware Julie Fiorini had. This is the spectrograph of one of Julie's green glass bowls. Note the silicon peak (labeled SiKa1) and calcium (CaKa1) that make up the bulk of the glass. There is also some iron (FeKa1), titanium (TiKa1), nickel (NiKa1), and copper (CuKa1) that add color to the glass. There is also a big arsenic peak (AsKa1) - arsenic was added to glass to reduce bubbling during the melting process (please visit this page for an excellent summary of ingredients in glass).
(The Ka1 next to each element symbol is the XRF's way of indicating the specific peak in the element's fingerprint - Ka1 stands for first peak from the K-shell alpha electron transition. TMI? Sorry about that.)
Julie Fiorini's arsenic-bearing glass bowl sitting on the XRF x-ray analyzer gun's window. The spectrum shown here is the data from this sample (0.4 Mb image). Thank you, Julie, for the photo!
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