The Photoelectron Corporation, located in Lexington, MA, makes miniature x-ray technology. This is primarily used for cancer treatment - a minimally invasive needle is stuck into a cancer patient, and the tip of the needle emits radiation at the exact source of the tumor, or the spot where a tumor once was. This minimizes irradiation of any parts that don't need it, and makes sure the unhealthy tissues get a good strong dose.
thanks to:
http://www.nottingham.ac.uk/~pczwww/physical/kr.html
http://www.chem.vt.edu/chem-ed/spec/material/xps.html
http://www.analytical.org/xps.html
www.photoelectron.com
Trevize's writeup on spectroscopy