Magnetically coupled 2-axis drive for XY positioning

 

The construction allows a 2-axis positioning of components in a hermetically sealed chamber without using feed-throughs. For this purpose, a motor-driven 2-axes linear system is assembled from outside into the vacuum chamber. This system is coupled with magnets and positions the guided linear table inside the chamber. Through a clever arrangement of the guide components inside the chamber, it is possible to integrate two independent positioning systems inside the chamber.

Application field

In this particular case, beam stops and other components such as sample holders or beam position monitors should be accurately and reproducibly positioned within a synchrotron beam with the help of the equipment.

Problem

To avoid background radiation, the entire synchrotron beam has to run in vacuum during X-ray experiments. For this reason, all the components, which are being hit by the beam, should be positioned in a vacuum chamber within the beam. For this purpose, various positioning options, which have disadvantages in some cases, are being used.
The disadvantages of using systems sealed with edge welded bellows are primarily, that the large vacuum forces require a very solid and stable design, a stiff guidance and a strong drive. Secondly, the limited mobility of the bellows and the mechanical stress restrict the linear position. In addition, the bellows are sensitive to dust and dirt and a pressure change within the system, caused by ventilation, for example, has a direct impact on the stress of the guides and the drives.
When using drives inside the vacuum chambers, disadvantages have also been revealed. Expensive linear axes and motors (suitable for vacuum) and electrical vacuum feed-throughs as well are necessary. The delivery time of these components are very long and the maintenance of the drives is very difficult. The vacuum chambers enlarge when being used and the axes are not always accessible.

Practice

A prototype chamber, which enables the independent positioning of two components inside a chamber, has currently been produced for the MiNaXS beamline at PETRA III. Here, a beam stop and a sample holder shall be accurately and reproducibly positioned inside a synchrotron beam with the help of the equipment. This equipment should be very light and compact.

Advantages

The magnetic coupling between the outer linear axes and the inner linear guides enables a transfer of linear movements into the interior of the chamber, which is free from external influences.
The magnetic coupling enables the use of very light and precise linear axes. The system can be built extremely compactly. Through a clever interlace of the drives, two positioning systems can be installed and moved independently in a very small vacuum chamber. In a vacuum, only relatively simple linear guides are being used, through a clever material selection, a UHV-compatible system can even be built.