Experimental investigation of models of the flow-through part of a liquid-metal target of an electronuclear setup

Abstract

An important element of an accelerator-controlled electronuclear setup is the liquid-metal target, where neutron production due to nuclear-physical reactions on the nuclei of the liquid-metal coolant occurs and the bulk of the energy of the particles from the accelerator is released.At present there are two basic concepts of the construction of a liquid-metal target: with and without a dense rigid stopper. In the first case the target cavity either is in direct communication with the volume of the liquid-metal coolant or it is separated from this volume by a barrier that is "transparent" for the particles and prevents vapor-and gas-like products of the interaction of the coolant nuclei with the particles in the accelerator from entering the accelerator cavity but is not in contact with its surface. Theoretical and experimental investigations have been performed with our participation on models of the flow-through part of such a liquid-metal target with vertical and horizontal arrangement of the branch pipe delivering particles from the accelerator. For a vertical (top to bottom) arrangement of the branch pipe, it was shown theoretically and experimentally that it is possible to obtain flow hydrodynamics in the flow-through part with a free-surface geometry of the liquid-metal coolant in the target such that the flow is prevented from the entering the accelerator cavity, which is under a deep vacuum. In the case of a horizontal arrangement of the branch pipe the optimal technical implementation, from the standpoint of the construction of a powerful accelerator, taking account of the start and stop regimes of coolant circulation through the target, is more complicated. This concept differs advantageously from the concept with a dense rigid stopper separating the coolant from the accelerator cavity in that it eliminates the complicated scientific-technical problem of producing a dense rigid stopper, which the coolant reaches, with possible local temperature pulsations and allowing for prolonged operation of the stopper material in a high-energy particle flux and limited absorption of particles in the stopper naaterial.For the promising power levels (100 MW and higher) of the liquid-metal targets, the variant without the stopper will probably be the only possible one. The variant with a dense rigid stopper may turn out to be acceptable for low-power liquidmetal targets with a limited service life. To analyze and give a scientific-technical substantiation for the construction of the strong part of the target for testing target constructions in water, we proceeded from the following considerations:1. It was determined on the basis of physical calculations that irrespective of other conditions, including power released in the target (with constant particle energy), the interaction of particles with nuclei and the bulk of the energy release occur over an actually constant distance in the working cavity of the target (400-600 mm). The particle distribution in the transverse cross section in the branch pipe is Gaussian (no...