The ultra-pure Ti for the low background experiments

The constant increase in mass of the cryostats, containment tanks, passive shielding and other mechanical elements of the modern low background detectors put more stringent requirements on their radiopurity levels. In general they have to be ∼1 mBq/kg of {sup 238}U/{sup 232}Th or lower, which means that mass concentration should be < 0.1 ppb for {sup 238}U and < 0.25 ppb for {sup 232}Th. Traditionally, the field relies on specially selected low background stainless steel, electrochemical oxygen-free copper, or a combination of the two. However, the most promising material in terms of physical and mechanical properties is Titanium. Our study of various Ti samples show that the levels of contaminations of commercially available industrial titanium can varies from 0.2 to 100 mBq/kg for U/Th. Therefore, the only possible way to obtain the material with a low and controlled level of contamination is to develop (or improve the existing) the production technology and to build the dedicated manufactory line.