The basic elements of ARGO-YBJ are single-gap RPCs made of bakelite (volume resistivity >5 1011ohm cm) with a 128 X 282 cm2 area. The RPCs read-out is performed by means of Al strips 6.7 cm wide and 62 cm long at the edge of which the front-end electronics is connected.
The pads are the basic element ("pixel") which defines the time pattern of the shower. The pick-up strips define the space pattern inside the pad.
The RPCs are operated in streamer
mode with a gas mixture of Argon (15 %), Isobutane (10 %) and Tetrafluoroethane
( 75 %), at ~ 7400 V, ~ 500 V above the plateau knee.