[6] By 1912, twelve pumps had been created, and the concept was presented to the meeting of the Physical Society in Münster on 16 September of that year, and was generally well received.
[5] Gaede published several papers on the principles of this molecular pump,[7][8] and patented the design.
[9] The working principle is that the gas in the chamber is exposed to one side of a rapidly spinning cylinder.
[10] The compression ratio can be estimated using the kinetic theory of gases by calculating the flow due to collisions with the rotating surfaces, and rate of diffusion in the reverse direction.
This "Gaede molecular pump" was used in an early experiment testing vacuum gauges.
[16] The main difference from the Gaede pump was the addition of a spiral, cut into either to the spinning cylinder, or to the static housing.
Larger, faster pumps of the Siegbahn type began to be made around 1940 for use in a cyclotron.
Secondly, a major issue with these pumps is reliability: with a gap between moving parts in the tens of micrometers, any dust or temperature change threatens to bring the parts into contact and cause the pump to fail.
Many modern turbomolecular pumps contain built-in molecular drag stages, which allows them to operate at higher foreline pressures.
While slower, the Gaede design has the advantage of tolerating a higher inlet pressure for the same compression ratio, and being more compact than the Holweck type.