High-density ultracold neutron sources for the WWR-M and PIK reactors
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RACTION AND SCATTERING OF NEUTRONS
High-Density Ultracold Neutron Sources for the WWR-M and PIK Reactors A. P. Serebrova, A. K. Fomina, A. G. Kharitonova, V. A. Lyamkina, D. V. Prudnikova, S. A. Ivanova, A. N. Erykalova, M. S. Onegina, and K. A. Gridnevb a
Petersburg Nuclear Physics Institute, National Research Centre “Kurchatov Institute”, Gatchina, Leningrad oblast, 188300 Russia b St. Petersburg State University, St. Petersburg, 199034 Russia e-mail: [email protected] Received March 6, 2015
Abstract—It is proposed to equip the PIK and WWR-M research reactors at the Petersburg Nuclear Physics Institute (PNPI) with high-density ultracold neutron (UCN) sources, where UCNs will be obtained based on the effect of their accumulation in superfluid helium (due to the specific features of this quantum fluid). The maximum UCN storage time in superfluid helium is obtained at temperatures on the order of 1 K. These sources are expected to yield UCN densities of 103–10 4 cm–3, i.e., approximately three orders of magnitude higher than the density from existing UCN sources throughout the world. The development of highest intensity UCN sources will make PNPI an international center of fundamental UCN research. DOI: 10.1134/S1063774516010211
INTRODUCTION It is proposed to develop a series of high-intensity ultracold neutron (UCN) sources based on the operating WWR-M research reactor and PIK research reactor complex, which is under construction, for studies in fundamental physics and investigations of nanostructures [1]. A technological complex with a UCN source based on superfluid helium has been developed. The complex includes the following components: UCN source, cryogenic unit, helium vapor evacuation system, compressor system, and system for storing and distributing helium. The parameters and modes of the equipment are mutually matched. It is planned to carry out a program of studies of fundamental interactions on the new UCN source. This program includes the search for neutron electric dipole moment (EDM) and the precise measurement of neutron lifetime. Both these problems are of fundamental importance for physics of elementary particles and cosmology [2]. The PNPI WWR-M reactor provides good conditions for solving this problem. It is equipped with a thermal column: a channel with a large diameter (1 m), adjacent to the reactor core. Due to the large diameter, this channel can accommodate a thick lead shielding (absorbing γ rays from the reactor core), a liquid deuterium premoderator operating at a temperature of 20 K (to generate cold neutrons), and a UCN source (based on superfluid helium at a tem-
perature of 1.2 K). It is planned to obtain UCN densities as high as 10 4 n/cm3. Currently, there are no such high-density UCN sources in the world, and this hinders progress in fundamental and applied research. The PIK reactor is one of the highest density neutron sources in the world.The horizontal channels of this reactor, GEK-3 and GEK-4, will be equipped with liquid-deuterium cold neutron sources, and the plan is to
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