One of the chief parameters of NPLs is the lasing energy (power), which is unambiguously associated with the parameter e, the share of kinetic energy of fission fragments absorbed in the gas mixture with respect to their total kinetic energy released in the uranium layers. The thickness of the active layer usually is comparable with the fragment range in the material making up this layer. The methods developed by now [14—17] make it possible, for given parameters of laser cells (geometric dimensions, material of active layer, composition of gas mixture), to calculate e as a function of gas density and thickness of the active layer, which is assumed constant. Within this approach the structure of the layer is considered to be uniform. But in fact, using the presently existing methods of thin layer’s manufacturing, the above conditions (thickness invariability and uniformity) are difficult to achieve. A real layer is non-inform, and its surface is rough [24, 25]. The amplitude of the deviations in layer inhomogeneities from the average value of its thickness, and the frequency of their repetition, can depend directly on the tech­nology of deposition of the fissile material on the substrates, and on the resistance of the layers to external environment factors, such as ejection of fuel micro-particles, erosion, corrosion and the like.

Study [26] showed that the presence of inhomogeneities in the uranium layer must lead to a reduction in the resultant efficiency in comparison with a uniform layer. This reduction must occur independently of whether the roughness of the active layer surfaces exerts a screening effect on the escape of fragments into the gas or not.