Effect of gas heating on the generation of an ultrashort avalanche electron beam in the pulse-periodic regime

The generation of an ultrashort avalanche electron beam (UAEB) in nitrogen in the pulse-periodic regime is investigated. The gas temperature in the discharge gap of the atmospheric-pressure nitrogen is measured from the intensity distribution of unresolved rotational transitions $(C^3\Pi_u, v'=0)\to(B^3\Pi_g,v''=0)$ in the nitrogen molecule for an excitation pulse repetition rate of 2 kHz. It is shown that an increase in the UAEB current amplitude in the pulse-periodic regime is due to gas heating by a series of previous pulses, which leads to an increase in the reduced electric field strength as a result of a decrease in the gas density in the zone of the discharge formation. It is found that in the pulse-periodic regime and the formation of the diffuse discharge, the number of electrons in the beam increases by several times for a nitrogen pressure of 9 $\times$ 10$^3$ Pa. The dependences of the number of electrons in the UAEB on the time of operation of the generator are considered.