Many attempts have been made to understand the processes occurring in the HCD since Friedrich Paschen's pioneering work in 1916 . Despite the fact that the hollow cathode effect and conventional glow discharge (GD) are two distinct electrical processes, some of their properties were assumed to be the same. In fact, the nature of the processes that occur in the HCD and conventional GC was poorly understood. For the first time, Little and von Engel (1954) demonstrated that HCD causes photoelectric effect while conventional GD emits UV light . used experimental evidence to clarify the problematic assumptions about HCD and conventional GD . For equivalent size and gas characteristics, the breakdown voltage of gaseous substances in the HCD is lower than in a conventional GD. Furthermore, the current created in the HCD is several orders of magnitude greater than that produced in the glow discharge. The HCD is an extremely effective electron generator. One of the most significant advantages of the HCD is that electrons emitted from the emitter surface can accelerate to the opposing emitter surface, which is in the shape of a hollow cylinder, and ionize gas. The energetic electron reaches the opposing surface in the HCD, causing the electric field to slow and the electrons to return to their original position.