Double bent channel of the IR-8 reactor for experiments with very slow neutrons

Special neutron guide aimed at very slow neutron extraction and also the source of ultracold neutrons with distilled water converter are described. Efficiency of ultracold neutron extraction is presented, velocity spectrum of the extracted neutrons is determined. The guide consists of two horizontally bent 12Kh18N10T stainless steel tubes 159x4 mm in diameter. The tubes are placed one above the other and are mutually joined by a short inclined section, approximately 30 cm far from the end of lower tube, that enters in the reactor core berillium reflector. The upper tube is horizontal, the lower is slightly inclined to the horizon. Vertical distance between tubes in attaching point is ∼ 25 cm, and at the outlet from biological shielding is ∼ 50 cm. Prospects for the guide application are bound up with changes to low-temperature converters, in particular, to parahydrogen one. Gaseous helium cooled cryogenic loop aimed at cooling such converter is designed, produced and tested. The above-mentioned specialized guide was erected during recostruction of IRT-M reactor