Like for a gun, you could say a gat but that's quite an old term. Most young people now would say stralley, a tool or a bucky.2011 October 21, Tony Thorne, Dictionary of Contemporary Slang, Bloomsbury Publishing:
Bucky
noun
1
Medicine, SciencesAbbreviation, Ellipsis, Informal Ellipsis of Potter-Bucky diaphragm.
The recipromatic Bucky differs from the manually cocked Bucky in that the grid travels in both directions across the table during the exposure.1960, Charles A. Jacobi, Donald E. Hagen, X-ray Technology, page 74: