High-sensitive spectrometer of fast neutrons and the results of fast neutron background flux measurements at the Gallium-Germanium Solar Neutrino Experiment

摘要

The principle of operation, design, registration system and main characteristics of a fast neutron spectrometer are described. The spectrometer is intended for direct measurements of ultra low fluxes of fast neutrons. It is sensitive to neutron fluxes of 10(-7)cm(-2)s(-1) and lower. The detection efficiency of fast neutrons with simultaneous energy measurement was determined from Monte-Carlo simulation to be equal to 0.11+/-0.01. The background counting rate in the detector corresponds to a neutron flux of (6.5+/-2.1) x 10(-7) cm(-2) s(-1) in the range 1.0-11.0 MeV. The natural neutron flux from the surrounding mine rock at the depth of 4600m of water equivalent was measured to be (7.3+/-2.4) x 10(-7) cm(-2)s(-1) in the range 1.0-11.0MeV. The flux of fast neutrons in the SAGE main room was measured to be < 2.3 x 10(-7) cm(-2)s(-1) in 1.0-11.0 MeV energy range. (C) 2002 Published by Elsevier Science B.V. References: 4