Working characteristics of the New Low-Background Laboratory (DULB-4900)

The Baksan Neutrino Observatory of the Institute for Nuclear Research of the Russian Academy of Science is one of the first and biggest underground laboratories in the world specially constructed to carry out different types of experiments in the field of nuclear physics, particle and astroparticle physics. Main technical characteristics of the new low-background laboratory DULB-4900 of the BNO are presented. The laboratory is located at a distance of 3700 m from the main entrance of the observatory tunnel in the hall with dimensions ~6×6×40m3. Thickness of the mountain rock over DULB corresponds to 4900 m w.e. and this deep location provides the cosmic ray flux reduction with the factor of about 107. The methods and results of the background level measurements both in the hall and operating facilities are given. Contamination of the radioactive 222Rn gas has been also measured in the air by using direct detection of γ-radiation of its daughter 214Bi distributed inside the volume of the low-background chamber. The results of the data analysis are presented and discussed.