ENVIRONMENTAL LOW ENERGY NEUTRONS MEASUREMENTS NEAR GROUND LEVEL IN SÃO JOSÉ DOS CAMPOS, SP, BRAZIL

In this study are presented measurements of cosmic ray induced neutrons near ground level in the region of São José dos Campos, SP, Brazil ~ (22⁰12´S, 45⁰50´W), during 2008 to January 2018. It was used to perform these measurements two tubes of He-3, with250 cm²ofsensitive area and with ~4atmospheres of internal pressure in each tube. The measurements were performed in one-minute interval and in free environmental situation above earth surface. It was thus given the background in count rate per minute of the region over time, which is a function of dry land, wet land and presence of electrical discharges (lightning)in the area. Taking in account efficiency of 0.60 to measure neutrons pulses in the tube, the sensitive area and energy range of 10 eV to 10.0 MeV. During dry period, the background measured were (1, 1 x 10^-4 neutrons/cm² MeV. s). During wet and rainfall period this background changing mostly due to water density increasing on ground. The lightning presence in that region also induces neutrons in same direction of the ray and with great intensity. In this period of measurements 2008 to 2018 and in that region the environmental neutrons fluxes measured shows increases during strong rainfalls and one day periodicity during dry surface and warms days.