Developments in nEXT turbomolecular pumps based on compact metal spring damping

A new range of turbomolecular pumps based on a Compact Metal Spring Damper (CMSD) system is described. The CMSD is essentially a support mechanism for the lower mechanical bearing which takes the form of a three-armed radial leaf spring. The result is that the design allows for small radial movement but has very high axial stiffness. The impact the CMSD has on the design of a new drag stage is described as is the constant very low vibration signature. Pumps fitted with a CMSD achieve such low vibration without the need for high-speed balancing and are fully end-user serviceable.

► A new patented bearing mechanism has been introduced into turbomolecular pumps.
► The Compact Metal Spring Damper is a radial leaf spring for the lower mechanical bearing.
► The CMSD allow for no balancing during manufacture and end-user service.
► The CMSD achieves a very low vibration signature which is kept after bearing change.
► The CMSD allows Siegbahn and regenerative drag stages which give a 20 mbar backing pressure.