Abstract: A device for leak detection on a test specimen, comprising a mass spectrometer (12), an at least three-stage turbomolecular pump (14), the input stage (18) of which is connected to the mass spectrometer (12) and which has a first intermediate gas inlet arranged between the input pump stage and the intermediate pump stage (26) and a second intermediate gas inlet arranged between the intermediate pump stage (26) and the output pump stage (24), an at least two-stage booster pump, the input pump stage (46) of which can be connected to the test specimen to be examined and which has an intermediate gas outlet (54) arranged between the input pump stage (46) and the output pump stage (48) and a pre-vacuum pump (22) which is connected to the outlet (20) of the output pump stage (24) of the turbomolecular pump (14) and is configured to generate a pre-vacuum pressure of less than 50 mbar at the outlet (20) of the turbomolecular pump (14) and to evacuate it against atmospheric pressure, characterized in that the intermed