Faraday Dark Space also known as a Glow Discharge Tube.
The pressure is reduced on a large tube while high voltage DC is applied to the electrodes.
Turn on the vacuum pump and submit the tube to a 1000V potential difference under direct current to start the demo. Turn off the lights and observe as gas inside the tube turns to plasma. As the pressure in the tube decreases, striations will begin to be visible in the plasma, becoming progressively brighter and more distinct. After a few minutes, however, the striations will begin to move laterally down the tube, becoming less distinguishable, and eventually unnoticeable to the naked eye. They can still be observed, however, under any kind of strobe effect – if the observer rapidly waves his hand in front of their eyes, or if they shake their head rapidly, the striations will become viable again.
The voltage will drop to around 800V once the plasma fires. If the current is too high it will be hard to see the striations.
Location: Tube K1-1, Vacuum Pump O1-5 , DC Power Supply Q1-1