ALMA sealing technology ensures the highest level of purity in the vacuum
The reliable sealing concept: magnetic fluid seals
The design focus of the ALMA rotary feedthroughs is on tightness and a high level of operational reliability. Our wear-free sealing concept based on magnetic fluid prevents mechanical abrasion, guaranteeing not only a long service life but also a high level of purity in the vacuum application. This benefits the customer, as maintenance downtime is no longer necessary, ensuring maximum system availability.Magnetic fluid seals utilize the reaction of magnetic fluids to an applied magnetic field. In principle, the seal consists of two pole pieces, a magnet, the magnetic fluid, a rotating shaft and a housing. The magnetic fluid is held in place annularly by the magnetic field at the sealing position between the pole pieces and the rotating shaft. The magnetic fluid thus creates a "liquid sealing lip" and seals hermetically.
In standard products, the static seal between the housing and the pole pieces is produced by an elastomer O-ring.
The magnetic fluid sealing technology for a high level of vacuum reliability

High-quality special magnetic fluid for maintenance-free applications
ALMA uses a special magnetic fluid that offers significant technical advantages compared to conventional fluids. Due to its significantly lower outgassing, this fluid excels above all in applications involving thermal loading.
Besides the quality criteria, the pollution control of the vacuum, the ALMA fluid also offers economic advantages: The maintenance costs are lower, as the typical shorter maintenance cycles due to the outgassing of conventional fluids are no longer necessary.
The material-bonded connection for UHV applications
If it is necessary to work in an ultra-high vacuum, leakage rates become a problem (e.g. when wafer-coating). ALMA rotary feedthroughs for use in ultra-high vacuums are designed so that a static sealing point is not required, as material bonding is used rather than an elastomer O-ring.The innovative design concept of material-bonded connections

Advantages of ALMA sealing technologies
- Material-bonded joining technology for UHV rotary feedthroughs
- Special ALMA magnetic fluid for greater vacuum integrity and efficiency
- No particle formation
- 100 % maintenance-free