Thulium, atomic no. 69, symbol Tm, weight at 168.94, products are mainly used in making crystal and lasers. An important application of the thulium in the Medicine area, and relatively independent of its high cost, is the production of portable X-ray sources. These sources are available for about one year, as tools in medical and dental diagnosis, as well as to detect defects in mechanical and electronic inaccessible components. This type of sources does not need excessive protection. Usually a small cap of lead is enough. Thulium can also be used in magnetic and ceramic materials (ferrite), similar to the yttrium-iron alloys, nowadays used in the microwave technologies.