Long-term variations in the natural thermal neutron flux at 4300 m above sea level

Abstract

Long-term variations in the natural thermal neutron flux in Tibet at an altitude of 4300 m above sea level are studied using scintillation en-detectors developed at the Institute for Nuclear Research, Russian Academy of Sciences. Substantial growth (on the level of several per cent each year over the last three years) in both the thermal neutron flux and the background recorded by the detectors is observed. This growth is associated with the intensity of cosmic rays. The effect is explained by an increase in the low-energy cosmic ray flux, due to reduced solar activity in the current solar cycle.