The invention belongs to the field of quantum electronics and can be applied in fast-flow gas lasers. The invention aims at increasing durability and reliability of the discharge cabinet. The cathode board consists of separate cathodes, the construction of which includes elongated emitters projecting the cathode case. In case of potential difference between the adjacent cathodes caused by inhomogeneity of the gaseous atmosphere in the principal discharge gap, the probability of breakdown in the gaseous atmosphere between emitters is much higher, than in the large space between the cases of the cathodes. Thus between the projections of emitters the discharge is ignited which shunts this potential difference and, therefore, protects the gap between electrodes from breakdown and insulating material from fracture.