The paper presents the results of research and development of the copper bromide active element with continuous control of the each pulse energy. Distinctive features are the implementation of the continious control mode for a large-volume gas discharge tube (more than 1.5 L) and the radiation formation by an unstable resonator. In this case, a hydrogen-containing additive was used to modify the plasma kinetics in order to increase the radiation power. The control was carried out through the use of an additional preionization pulse. The dependences of the generation power on each line on the preionization pulse energy and the time delay between this pulse and the excitation pulse are obtained. It is shown that in the developed layout, the determining factor in pulse energy controlling is the population of metastable levels of copper atoms.