Device for refrigerating and/or liquefying a working gas containing helium or consisting of pure helium, the device comprising a working circuit in the form of a loop for the working gas and comprising, in series: - a working gas compression station provided with at least one compressor (11, 12), - a cold box for cooling the working gas, comprising a plurality of heat exchangers positioned in series and at least one member for expanding the working gas, - a system for the exchange of heat between the cooled working gas and a user, - at least one return pipe for returning to the compression station the working gas that has passed through the heat exchange system, the return pipe comprising at least one heat exchanger for reheating the working gas, the device further comprising an additional pre-cooling system for pre-cooling the working gas leaving the compression station, the pre-cooling system comprising at least one volume of auxiliary cryogenic fluid such as liquid nitrogen, the volume being connected to the working circuit via at least one heat exchanger in order to selectively transfer frigories from the auxiliary fluid to the working gas, the cold box comprising a first working-gas cooling stage comprising a first heat exchanger positioned at the output of the compression station in addition to a second heat exchanger, characterised in that the pre-cooling system comprises a third heat exchanger, the first heat exchanger being of the aluminium plate-fin type, the second heat exchanger being of the tube or welded-plate type, said second heat exchanger being immersed in an auxiliary cooling fluid bath, the second and third heat exchangers being connected both in series and in parallel to the working circuit downstream of the first heat exchanger, i.e. the working gas cooled in the first heat exchanger can be admitted selectively to the second and/or to the third heat exchanger, and in that the second heat exchanger is immersed in the first volume of auxiliary liquefied gas. - a working gas compression station provided with at least one compressor (11, 12), - a cold box for cooling the working gas, comprising a plurality of heat exchangers positioned in series and at least one member for expanding the working gas, - a system for the exchange of heat between the cooled working gas and a user, - at least one return pipe for returning to the compression station the working gas that has passed through the heat exchange system, the return pipe comprising at least one heat exchanger for reheating the working gas, the device further comprising an additional pre-cooling system for pre-cooling the working gas leaving the compression station, the pre-cooling system comprising at least one volume of auxiliary cryogenic fluid such as liquid nitrogen, the volume being connected to the working circuit via at least one heat exchanger in order to selectively transfer frigories from the auxiliary fluid to the working gas, the cold box comprising a first working-gas cooling stage comprising a first heat exchanger positioned at the output of the compression station in addition to a second heat exchanger, characterised in that the pre-cooling system comprises a third heat exchanger, the first heat exchanger being of the aluminium plate-fin type, the second heat exchanger being of the tube or welded-plate type, said second heat exchanger being immersed in an auxiliary cooling fluid bath, the second and third heat exchangers being connected both in series and in parallel to the working circuit downstream of the first heat exchanger, i.e. the working gas cooled in the first heat exchanger can be admitted selectively to the second and/or to the third heat exchanger, and in that the second heat exchanger is immersed in the first volume of auxiliary liquefied gas.