Developments in mirror cooling via thermoelectric Peltier module in LNLS/Sirius

Abstract The development of X-ray mirrors has been stated in three major areas: optical, mechanical, and thermal designs. The last topic deals with modelling and controlling thermal expansion due to the absorption of the incident beam, as well as heat transfer through radiation and contact among the parts. Such control is important ensuring the mirror surface deformation caused by the power load remains within specification. Peltier devices are reliable and user-friendly thermal control actuators coping with smaller total power load, which were developed for the CARCARÁ, MOGNO, and SABIÁ beamline mirrors as an alternative to designs such as cryogenic or water/vacuum interfaces. The Peltier effect is a well-known thermoelectric phenomenon occurring when an electrical current flows through a p-type and an n-type junction. This effect can be used to transfer heat from one side of the junction to the other, resulting in a temperature difference. A Peltier dispositive was integrated in a PID control-loop associated with platinum resistance temperature sensors attached to the mirror mechanism. Here we describe the thermal design process and modelling established for a mirror mechanism and some commissioning results are discussed in terms of temperature and mechanical stability and minimized thermal deformation.