How the Vacuum Becomes the Pacemaker for High-tech

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Leybold GmbH

Laws of physics change in high vacuum

The large free path length of remaining molecules in a high vacuum (10 cm to 1 km) “changed” the known physics at the time. Hence, the possibility of a “molecular air pump”, which required a prevacuum. Ultimately, a molecular air pump is a rotary pump in with the cylinder entrains the molecules, which accumulate in a groove in the housing. Gaede demonstrated that the particularities of a high vacuum cause an accumulation of gas molecules on the walls (“gas skin”). The inventor utilised the principle of friction. A molecular pump does not require a piston shutting off a certain amount of gas from the space that is to be evacuated. Rather, the molecules are entrained by adhesion to the wall.

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This enabled a completely new type of high vacuum pump. Gaede’s inventions of the molecular pump and the diffusion pump were important products for the company, which eventually specialised in vacuum technology. But many other companies developed diffusion pumps of similar design. The Langmuir-patent for a mercury diffusion pump, held by General Electric, prevented Leybold from selling their pumps abroad and in Germany, they had to deal with a patent by Max Volmer, whose vacuum pump operated several stages with the same steam. Luckily, a patent dispute ended positively for E. Leybold’s Nachfolger and it came to an agreement under which the company was allowed to distribute a multistage diffusion pump constructed by Gaede.

The company's managing director at the time, Alfred Schmidt, even opened up the international market by purchasing licenses of Langmuir patents. Product development remained Gaeden's responsibility for a long time. In 1932, the company against his opposition acquired licenses for the oil diffusion pump, an English invention with which Leybold further extended their high vacuum offering. Gaede once again proved his worth for vacuum technology with his invention of the gas ballast principle, which is still relevant today and allows to remove steam from the vacuum pump by replacing it with a non-condensing gas. However, this patent expired before the company could capitalize on it.

The years following World War 2 saw rapid progresses in vacuum technology, led by effective development teams probably inspired by the meanwhile deceased Gaede. The economic boom of the time and many new fields of application led to various improvements. Leybold continued to be a leading supplier of vacuum components, perfected and expanded their range of rotary piston pumps and introduced fractionated oil diffusion pumps.

In 1957, the company already supplied their oil diffusion pumps to CERN, the European Organization for Nuclear Research. In the same year, the company introduced an innovation in the field of measurement technology with a combination of thermal conductivity and penning vacuum gauges. This was followed by partial pressure measuring instruments and in the early 1960s finally by titanium sublimation pumps, i.e. pumps in which titanium is sublimated in a high vacuum. It then coats the surrounding walls of the pump and binds gas molecules. Ion sputter pumps, another invention of that time, are based on a similar principle. Here, gas discharges are used to ionise evaporated titanium in a magnetic field in order to improve efficiency. Cryogenic pumps were also introduced in the early 1960s, and in 1965, Leybold marketed the first helium leak detector.

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