Magna-coil

A magna-coil was a magnetic device which was present in the dome of the R-series astromech droid QT-KT. Circa 20–19 BBY, QT-KT used her magna-coil to attract multiple swarm mines in order for D-Squad to help retrieve a Separatist encryption module from the flagship of the tactical droid Aut-O. The magna-coil attracted the swarm mines, then they were safely placed into her dome. Later, the magna-coil was released out of her dome and also released the swarm mines, which then destroyed multiple battle droids.

Behind the scenes
A magna-coil first appeared, albeit unnamed, in "Secret Weapons," the tenth episode of the fifth season of the animated series Star Wars: The Clone Wars, which first aired on December 1, 2012. Magna-coils were identified by name in the accompanying episode guide's episode gallery on StarWars.com.