Studies of gas volumes current density in the ATLAS RPC detector during 2018 data taking at Large Hadron Collider

The ATLAS Resistive Plate Chamber (RPC) detector is a tracking trigger, used to primarily select high momentum muons in the ATLAS barrel region ($|\eta|<$1.05) at the 40 MHz collision rate, and to provide muons azimuthal coordinates. The RPC system consists of about 3700 gas volumes covering a sensitive surface of about 4000 m$^{2}$. It is arranged in three concentric double layers distributed on a radial distance of about 5m and operating at approximately 0.5 Tesla toroidal magnetic field. RPCs provide 6 points along the muon track with a space-time resolution of about 1 cm$^{2}\times$1 ns. This work studies systematically gas volumes current as a function of the electric field applied on the gas, and environmental parameters both without/with the Large Hadron Collider (LHC) beam induced background and up to an instantaneous luminosity L$_\text{inst}$ =2$\times$10$^{34}$ cm$^{-2}$ s$^{-1}$ (twice larger the design LHC luminosity). These measurements have been used to study the RPC working condition and to extrapolate the detector response to High Luminosity LHC regime with L$_\text{inst}$=7.5$\times$10$^{34}$ cm$^{-2}$ s$^{-1}$.