Refrigeration system comprising a refrigerant circuit in which a total mass flow (G) of a refrigerant is conducted, a heat exchanger arranged in the refrigerant circuit cooling the refrigerant on the high pressure side, an expansion cooling apparatus arranged in the refrigerant circuit which, in the active state, cools the total mass flow (G) of the refrigerant and therein generates a main mass flow (H) of liquid refrigerant and an additional mass flow (Z) of gaseous refrigerant, a collector for the main mass flow (H), at least one normal cooling stage which takes a normal cooling mass flow (N) from the collector and has a normal cooling expansion element and, arranged downstream therefrom, a low pressure-side normal cooling heat exchanger making cooling capacity available for normal cooling, a deep cooling stage which takes a deep cooling total mass flow (TG) from the collector and has a deep cooling expansion element and, arranged downstream, a deep cooling heat exchanger making cooling capacity available for deep cooling, and also having a deep cooling compressor unit arranged downstream of this deep cooling heat exchanger , wherein the deep cooling stage has a deep cooling expansion cooling apparatus for further cooling of the deep cooling total mass flow (TG) which, in the active state, decompresses and cools the deep cooling total mass flow (TG) and therein generates a deep cooling main mass flow (TH) which is fed to the deep cooling expansion element , and also a deep cooling additional mass flow (TZ) and in a deep cooling collector , and at least one refrigerant compressor unit which is arranged in the refrigerant circuit and compresses the refrigerant to high pressure (PH), wherein the refrigerant compressor unit compressing the refrigerant to high pressure (PH) comprises a plurality of refrigerant compressors , wherein each of the refrigerant compressors has a port on the suction side and a port on the pressure side, wherein all the pressure-side ports are aggregated together to one pressure port of the refrigerant compressor unit , wherein the refrigerant compressor unit compresses the main mass flow (H) and the additional mass flow (Z) to a high pressure, characterised in that all the suction-side ports are aggregated together to one suction port of the refrigerant compressor unit , in that in the refrigeration system, the deep cooling additional mass flow (TZ) is fed to the suction port of the refrigerant compressor unit compressing the refrigerant of the main mass flow (H) and of the additional mass flow (Z) to a high pressure (PH), in that the deep cooling main mass flow (TH) compressed by the deep cooling compressor unit is fed by the refrigeration system to the refrigerant compressor unit compressing the refrigerant of the main mass flow (H) and of the additional mass flow (Z) to a high pressure, in that the intermediate pressure (PZ) is adjustable by feeding at least a portion of the additional mass flow (Z) to an additional suction port of the refrigerant compressor unit , to which additional ports of each of the refrigerant compressors are aggregated together, and/or in that the intermediate pressure (PZ) is adjustable by feeding at least a portion of the additional mass flow (Z) to the suction port of the refrigerant compressor unit by means of a throttle element , and in that a controller is provided which, by means of a pressure sensor , detects an intermediate pressure (PZ) of the additional mass flow (Z) in the collector and which feeds the additional mass flow (Z) either to the additional suction port or thereto and partially to the suction port or to the suction port of the refrigerant compressor unit . <EOS>