Delta wave augmenter

A delta wave augmenter was a device that induced a deep, restful sleep in humans and near-humans. The Fifth Doctor constructed one on Deva Loka using the sonic screwdriver as a component, and used it to help Nyssa sleep after her collapse. (DW: Kinda)

The Doctor later used his delta wave augmenter on Nyssa again as part of his plan to defeat Nephthys. (MA: The Sands of Time)

On Kirith, Raphael used a delta wave augmenter to stop dreaming about Darien, but it was only effective for a few months and the dreams returned. (NA: Timewyrm: Apocalypse)