SF6 quenched gas mixtures for streamer mode operation of RPCs at very low voltages

In the present paper we describe a search for gases that allow to reduce the energy of the electrical discharge produced in Resistive Plate Chambers (RPCs) operated in streamer mode, by reducing both the operating voltage and the released charge. This can be achieved, with current gas mixtures of argon, tetrafluoroethane (TFE) and isobutane, by reducing the total amount of quenching components (TFE+isobutane) down to 10–15% and compensating for the lower gas quenching power with the addition of small amounts of SF6. We show here that SF6, even for concentrations as low as 1% or less, has a strong effect in reducing the delivered charge in low quenched gases and allows to achieve a proper working mode of the RPC even at voltages as low as 4–5 kV over a 2 mm gas gap.