By the late 1970s and early 1980s a generation of accelerators had been made obsolete by newer machines in terms of being useful for leading edge research. Still useful for other tasks, these older machines were turned to a wide variety of new studies. One particularly active area of research is collisions between higher mass particles, instead of fundamental particles like electrons or protons. Although the total energy of the reaction is the same, or lower, than it would be using lighter elementary particles, using heavier elements increases the number of products from the reactions, revealing low-frequency reactions that might otherwise go unnoticed. Noble gasses are particularly useful for these experiments because they are easy to handle, unreactive and relatively inexpensive.