Precision UHV compatible Mirror mounting mechanism for Beamline

S.M. Chaudhari, D.M. Phase, A.D. Wadikar.

Inter University Consortium for DAE Facilities, Indore.452 017,India.

              The overall performance of beamline depends on factors such as alignment of the optical components with respect to synchrotron beam, the quality of optical elements (surface roughness, tangent error, coating etc.) and mechanical design. A good alignment scheme can effectively reduce the complications of mechanical design and also help to improve performance of the instrument. From the ray tracing studies it is clear that the pre-mirror alignment with respect to SR beam and other components of the beamline is very important. To achieve better image quality not only pre-alignment of pre-mirror is needed but also fine-tuning has to be done online necessarily. The motions involved in alignment of pre-mirror are three translational motions in X-Y-Z directions, two tilt motions in the parallel and perpendicular direction to SR beam and one rotational motion around the perpendicular to mirror surface.  The explicit values of tolerances required for these motions are estimated from ray tracing studies of complete beamline. The mechanical design (figure-1) of ultra high vacuum (UHV) compatible mirror holder along with precision motions consist of three parts viz. I) Mirror holder; II) X-Y-Z mount; and III) tilt and rotary motion mechanism, all assembled in 6-way cross. The entire assembly is conflat^R flange mounted and can be directly inserted in ultra high vacuum mirror chamber. The main mechanical features of this mirror mount system are: a) All motions are independent and centre of mirror remains fixed during angular movement of mirror with respect to beam; b) In this design gears are avoided and spring loaded motion feedthroughs are employed to achieve backlash free precision motion.
 

An identical mechanical design of that of pre mirror is adopted for post mirror chamber and holder. Both the mirror chambers along with mirror mount system are fabricated indigenously. For details please see the article “Precision mirror mounting system for UHV compatible synchrotron radiation beamline” S.M. Chaudhari, D.M. Phase, G.R. Kulkarni, and A.V. Pimpale. Proceedings of International conference on “ Vacuum Science and SRS Vacuum systems”; Vol.-1, P-283, 1995, Eds. N. Venkatramoni and A.K. Sinha.

 Fig.1 Mechanical design of precision motion mechanism