Thermal Effects in Precision Systems Design Considerations, Modelling, Compensation and Validation Techniques

Dr Theo Ruijl, FEI Company

Abstract
In common high end precious systems, thermal effects play in general a very important role with respect to the final performance of the system. A variety of topics has to be dealt with to tackle the variety of problems. Starting with the design itself, (1) design with reduced thermal sensitivity is a crucial point of departure. Knowledge regarding inherent stable design, controlling conductivity, insulation and shielding and thermal design methodologies for non standard conditions (e.g. vacuum, cryogenic) is important to be developed. To steer the design in an objective way, (2) modeling tools and techniques are necessary (model reduction, model validation and error compensation algorithms). (3) Active control of the thermal state of a system and its environment are ways to reduce the amount of thermal distortion. Knowledge about control algorithms for thermal systems, identification of thermal systems and thermal actuator design are required. To apply an active control or to indentify or verify a thermal system, (4) measurement methods and experimental techniques are necessary. To enable this one needs fast and accurate temperature sensing, accurate temperature calibration methodologies, reconstruction techniques of thermal states and sensor placement optimization. In the paper some highlights and current status are given regarding the above listed topics.