The image in the background exhibits a fascinating property of superfluid helium-4 known as the fountain effect. The fountain effect can be demonstrated using thin-necked flask filled with superfluid He-4 and sealed at the bottom with very fine powder, across which only superfluid can flow. The flask is placed into a superfluid helium bath and heated, causing superfluid helium to flow through the powder plug and into the flask. Helium within the flask is ejected, creating a fountain as demonstrated here.

To learn more about superfluid helium-4 and its use in the DELight experiment, click here.