Delta wave augmenter
A delta wave augmenter was a device that induced a deep, restful sleep in humans and humanoids. 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. (TV: Kinda)
The Doctor later used his delta wave augmenter on Nyssa again as part of his plan to defeat Nephthys. (PROSE: The Sands of Time) She later seemed to use it of her own accord in her bedroom aboard the TARDIS, to augment her sleep. It was "the one thing that [gave her] peace", allowing her to control her thoughts. (AUDIO: Dream Team [+]Loading...["Dream Team (audio story)"])
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. (PROSE: Timewyrm: Apocalypse)
By the time of the Thirteenth Doctor, the TARDIS itself was equipped with a delta wave augmenter. The Doctor used parts of it to try to communicate with the ghosts on the Powell Estate. (AUDIO: Salvation)
