I am working with a set of alloys that must first be ground up in a ball mill at cryogenic temperatures. It is important that no contamination makes it into the material and careful steps are taken to ensure this end. Unfortunately when we ran a set of samples through our RBS lab and then again through PIXE we saw that we had Fe and Cr contamination. At first it was thought that it came from the cutting tools used to prepare the samples so we ran another sample that was cut using EDM. The results were the same. The only other contact the material has with a stainless steel is from the ball milling step. We have been using a 440C for the cup and balls but it would seem a 316L may be a better fit for this application. I know 440C does not typically do well at cryo-temps but that is what other labs have been using so we didn't expect for there to be problems of this type. Some things to consider for the new cup and ball material are machinability, cost, availability, cryogenic properties, vibration and fatigue resistance, and ability to be sealed (cups are filled in an inert Ar atmosphere). Another possibility is a heat treatment of the current 440C materials, however I am unsure what the best approach would be in that regard.