In the field of nuclear engineering

Nuclear engineering

Nuclear engineering is the branch of engineering concerned with the application of the breakdown as well as the fusion of atomic nuclei and/or the application of other sub-atomic physics, based on the principles of nuclear physics...

, a rabbit refers to a pneumatically controlled tool used to insert small samples of material inside the core of a nuclear reactor usually for the purpose studying the effect of irradiation on the material. Some rabbits have special linings to screen out certain types of neutrons. (For example, the Missouri University of Science and Technology

Missouri University of Science and Technology

Missouri University of Science and Technology is an institution of higher learning located in Rolla, Missouri, United States, and part of the University of Missouri System...

 research reactor uses a cadmium

Cadmium

Cadmium is a chemical element with the symbol Cd and atomic number 48. This soft, bluish-white metal is chemically similar to the two other stable metals in group 12, zinc and mercury. Similar to zinc, it prefers oxidation state +2 in most of its compounds and similar to mercury it shows a low...

-lined rabbit to allow only high-energy neutrons through to samples in its core.)