Noun
Faraday dark space (plural Faraday dark spaces)
The dark space in a glow discharge that is between the negative glow and the positive column.
Crookes found that as he pumped more air out of the tubes, the Faraday dark space spread down the tube from the cathode toward the anode, until the tube was totally dark. Source: Internet
This came to be called the "cathode dark space", "Faraday dark space" or "Crookes dark space". Source: Internet