Tutorials

Monday 24 May 2004

FLEXURES
One of the major tasks in third generation synchrotron radiation facilities, as well as in the future light sources based on free electron lasers or recirculating linacs, is the ultra-high precision positioning of optical and other elements with resolutions, accuracies and precisions in the nanometric and mrad ranges. Given the need to comply also with ultra-high vacuum and radiation environments, this goal is essentially met by using positioning mechanisms based on compliant (flexure) structures.
This choice allows then to achieve a whole series of advantages, amongst which is particularly important the absence of several mechanical non-linearities. This makes in turn possible to use simple control typologies.
The flexures tutorial will cover the basic characteristics of mechanical elements based on compliant structure. The analytical and experimental characterisation of such mechanisms will be described. The examples of their usage in synchrotron radiation, as well as in the general field of mechanical engineering will be given.

COOLING
Synchrotron radiation facilities use megawatts of power to produce highly intense x-ray beams with power densities exceeding 100 kw/mrad2. The accelerator and beamline components must be efficiently cooled to meet the stringent requirements on temperature stability, thermal distortions and vacuum compatibility.
This tutorial will cover various cooling schemes that utilize process deionised water, liquid nitrogen, liquid metal, gaseous helium and Peltier effect, as well as cooling enhancement techniques such as channel inserts, pin-post and micro-channels.
Key words: cooling techniques, process water, liquid nitrogen, helium, Peltier, channel inserts

OPTO-MECHANICS
This presentation will emphasise the application of mechanical-engineering principles to the design fabrication and measurement of x-ray-optical surfaces suitable for use in synchrotron-radiation beam lines. This will include the design process for mirrors in which the principle issues that must be addressed are (i) specification writing, (ii) polishing, and shaping the surface (perhaps by bending) (iii) cooling, (iv) materials issues, (v) methods of manufacture (vi) non-distorting methods for holding an optic (vii) mechanisms (especially flexural ones) for controlling positions of optics. During and after construction of an optic the surface figure and finish must be measured for compliance with specification and to enable the performance of the optic to be modelled. We discuss the both the measurement and analysis parts of this work. In discussing these principles we draw examples from a wide range of x-ray optical systems including grating and crystal monochromators, x-ray microscopes and interferometers and a "zoo" of different applications of flexures.

VIBRATION-STABILITY
This lecture presents the mechanical effects on beam stability, starting from the introduction of the phenomenon of beam instabilities, their frequency domain and the most concerned issues of the users. The sources of mechanical instability, their transfer routes and the sensitivities to the fluctuations of beam orbit and beam size are elucidated. Some methods, such as temperature control, vibration isolation, and mechanical structure improvement, to stabilize the mechanical stability are discussed. The principle of major sensors and the setup for the measurement of mechanical stability are also introduced.

It has been decided that two topics: "Thermo mechanical analysis" and "Positioning" will be presented by Invited Speakers at the Workshop.