“Stand B” for Studying NPL Characteristics

The RF State Science Center FEI (in Obninsk) began studying problems of NPLs in 1981 at the initiative of V. Ya Pupko [39]. Within the scope of the program to develop a powerful laser amplifier with nuclear pumping, at present an evaluation unit of the laser system has been developed which was called “Stand B” [13, 39, 56]. Here the characteristics of one of the two parts of “Stand B” are examined, the so-called “first workplace,” which was put in operation in 1996, and was intended to study the characteristics of individual laser cells. Information about the “second workplace” of Stand B is provided in Sect. 6.3 of Chap. 6.

The basic element of the laser stand is the BARS-6 dual-core pulsed reactor, made on the basis of the BARS-5 reactor [3, 32] in accordance with the design documentation and technical assistance of VNIITF. The two reactor cores are arranged on a platform that can be moved through the reactor hall depending on the tasks of the experiment. The distance between the axes of the reactor cores is varied between 340 and 1,500 mm, making it possible to irradiate laser cells more uniformly than in the case of a pulsed reactor with a single reactor core. The half­height duration of the reactor pulse is 150-200 ^s.

In one of the positions (“first workplace”) of the reactor core, experiments are carried out to study the characteristics of individual NPLs (see Fig. 2.1e). By way of example, Fig. 2.18 shows a diagram of one of the experiments studying the characteristics of an Ar-Xe laser [13]: the distance between the reactor cores is 70 cm; the cylindrical stainless steel laser cell has a length of 250 cm and internal diameter of 49 mm (wall thickness 0.5 mm). A 5-^m thick layer of 235UO2 was deposited to the internal surface. The distribution of the specific power deposition

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along the length and radius of the laser cell at the reactor pulse maximum for the Ar-Xe mixture (100:1) at a pressure of 0.5 atm is shown in Fig. 2.19.

In experiments in the “first workplace” of Stand B, studies were also carried out on the gain measurements of some laser media [57, 58] and the dynamics of development of optical non-uniformities [59].

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