@article {Keenan:1975:0003-7028:63,
	author = "Keenan, Joseph A.",
	title = "The Determination of Parts per Million Levels of Thorium in Optical Components by X-ray Fluorescence",
	journal = "Applied Spectroscopy",
	volume = "29",
	number = "1",
	year = "1975",
	abstract = "A nondestructive technique for the determination of thorium in optical glass has been devised using tube-excited x-ray fluorescence with an energy-dispersive detector. Capability for full calibration and sample analysis has been incorporated into a computer-coupled system. Bulk thorium concentrations as low as 87 ppm have been detected with a coefficient of variation of 27.2% at 95% confidence using NBS-certified standards. At 466 ppm the coefficient of variation was 5.6% at the 95% confidence level. Qualitative determination of thorium in optical coatings has been demonstrated also.",
	pages = "63-67",
	url = "http://www.ingentaconnect.com/content/sas/sas/1975/00000029/00000001/art00011",
	doi = "doi:10.1366/000370275774455392",
	keyword = "Analysis, for thorium, Crystal, glass, X-ray fluorescence, Computer applications"
}