Unlike the schemes presented previously, which use the NOC principle, some studies [65—68] consider the possibility of creating a powerful pulsed-periodic RL with direct conversion of the kinetic energy of the fission fragments into laser radiation. It is proposed that this RL may be used in inertial confinement fusion facilities as a final amplifier for the laser driver [65, 66].

A schematic of a pulsed-periodic RL based on the separation of the reactor and subcritical laser block is shown in Fig. 11.15. The laser block is a cylindrical longitudinal cavity containing the core of the IBR-type “start-up” pulsed reactor

[64] with a reactivity modulator. It is filled with a laser medium containing fissile material and includes elements of the neutron moderator. Neutron calculations [67, 68] have shown that the system operating at a frequency <5 Hz with about 8 MJ of energy release in the laser block over one pulse can provide ~1 kW/cm3 of specific power deposition in the laser medium at a duration of 1-5 ms. Some parameters for this RL are given in Table 11.6.

Upon evaluation of the energy characteristics of the laser radiation, it was supposed that the conversion efficiency of the nuclear energy absorbed in the laser medium into the laser emission is щ = 2.0 %. It was proposed in studies [65, 66] that the laser medium could use inorganic aprotonic liquids (for example, POCl3-ZrCl4:Nd3+) with uranium dissolved in them (see the first section of this chapter). In the authors’ opinion [65, 66], the possibility of also using gas laser media in the design under consideration is not ruled out. However, in this case, at least the problem of effective energy deposition to the gas medium must be solved, and a laser medium must be found that not only has a high nI, but a long upper laser level lifetime (~1 ms).