Thermal Regulation of the CMS Preshower Windows

A prototype Preshower ( SE) `window' has been used to test the viability of a thermal regulation scheme whose final purpose is to maintain the inside of the Preshower at a low temperature ( -10 degrees C) whilst presenting an ambient ( 18 degrees C) temperature to neighbouring detectors. A simple control layout with coarse segmentation was found to be sufficient, foregoing the need for a complex multivariable controller. The measurements are in agreement with simulation and confirm that a stabilization in time of the SE external faces within a few tenths of a degree can be achieved, as required by the Endcap ECAL.