How the Vacuum Becomes the Pacemaker for High-tech

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KNF Neuberger GmbH

Redaktionsbüro Reutner Dr. Ulla Reutner

Leybold GmbH

Turbo pump enables pure ultra-high vacuum

NIt would take until the 1970s for Leybold to add the turbomolecular pump to their portfolio. The principle of molecular flow
discovered by Professor Gaede is also applied in this pump, which had been invented in 1956 by Willi Becker, head of development at Pfeiffer, a competitor of Leybold’s. Rotor and stator discs alternate in the pump housing, with the rotor discs acting like flat blades that are slightly tilted, like fan blades. The stator discs are mounted to the cylindrical housing and inversely tilted. A vacuum flange provides the connection to the recipient. When the rotor blades move with the average speed of the gas molecules, they transfer a pulse to the molecules and cause a molecular flow in the direction of rotation - provided that the prevacuum was high enough that the free path length of the gas particles about equals the dimensions of the active parts.

Gallery

This molecular pump, whose interior is similar to a turbine, could be operated more stable than Gaede’s machine, and provided a “pure high vacuum” that could not be contaminated by oil or other particles. Over the years, turbomolecular pumps have become increasingly powerful, robust and smaller and formed the basis for progress in electronics and analytics. Depending on the design, they can achieve ultimate pressures of up to
10^-10 hPa. Further optimisations, like maintenance- and wear-free magnetic suspensions and increasing ease of use opened up further fields of application for the new pump type since the turn of the last century. Today, Leybold offers various versions of this pump type, including a plug and play model with magnetic suspension, integrated frequency converter and power supply. The magnetic rotor suspension reduces noise and vibration and ensures that the system is largely free of hydrocarbons.

Application becomes a driver for development

Other pump principles also benefited from further developments. In 2001, the Leybold development team designed dry compressing backing pumps based on the screw principle. For industrial applications, these are also available in an explosion-proof design. Generally, the adaptation of a pump type for its application can be viewed as a key driver for further developments in the first decade of the 21st century.

There are for example screw pumps, which are particularly well suited for short cycles in locks or for evacuating large recipients. There are also pumps specifically designed for media typically used in photovoltaics or flat screen production. Even though Prof. Gaede died in 1945 and had no direct part in perfecting vacuum technology as we know it today, his inventions, particularly the diffusion and the molecular pumps, have been the foundation for it all. His inventiveness is still particularly present in his old company, Leybold.

Ultimately, the applications of vacuum technology made possible by his discoveries have become the key drivers for today’s developments. In 2017, Leybold again plans an innovation addressing customer demands: a dry compressing multistage backing pump for the analytics market. The roots pump works significantly quieter than other pumps in the size of 40 to 60 m³/h; it is also compact, low-maintenance and equipped with a gas ballast valve. Together with the turbomolecular pump series introduced in 2014 and the high vacuum turbo pump system launched in 2016, it was specifically designed for applications like mass spectrometry and electron microscopy. There is no doubt that the high demands of laboratory and analytical customers will continue to drive innovation in the company.

* Dr. U. Reutner: Fachjournalistin Technik & Wissenschaft, 86916 Kaufering

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