Thirty years of turbomolecular pumps: A review and recent developments

The history of turbomolecular pumps (TMP’s) will be reviewed and the principle of the pumping action will be explained. Some of the theoretical considerations for TMP’s yield an easy check of the pumping speed data for a given TMP. After highlighting the rapid development of the technique, the actual technical status of TMP’s will be given in detail. Some of the applications (e.g., in magnetic fields, plasma etching, radioactive gases) demonstrate that the ‘‘standard’’ TMP has some shortcomings which have to be overcome by dedicated adaptation. The recent combination of a TMP with molecular pumping stages shifts the useful foreline pressure to higher values, and enables the use of smaller dry backing pumps. Future trends in the field of TMP will be mentioned.