Ultrapure materials for alpha particle-sensitive applications

Materials used in applications where alpha particle radiation can produce “soft” or transitory errors are commonly specified and characterized in terms of uranium and thorium content, often by glow discharge mass spectrographic analysis. Analytical results indicate that low levels of uranium and thorium do not adequately reflect the alpha flux potential of some materials, especially in cases where radioactive isotopes are not in equilibrium or where a dominant decay parent other than uranium or thorium is present. An additional characterization technique—highly sensitive, surface alpha particle flux measurement—has been developed. Alpha particle counting, when used in conjunction with trace metal analysis, allows more optimum selection of low-alpha-radiation materials.