Control System Design of the CERN/CMS Tracker Thermal Screen

The Tracker is one of the CMS (Compact Muon Solenoid experiment) detectors to be installed at the LHC (Large Hadron Collider) accelerator, scheduled to start data taking in 2007. Since it will be operated at a temperature of –10°C, a thermally insulated environment has to be provided by means of a thermal screen. The control system design of the thermal screen has been accomplished via a formal description of the process both with a thermodynamic model and the electrical equivalence. A PID (Proportional Integral Derivative) controller has been designed and evaluated using MatLab, along with the finite state machine. The controller has been implemented on a PLC (Programmable Logic Controller). The results achieved so far prove that this methodology is rigorous, effective and time saving; every step of the procedure is well defined, simplifying the debugging and updating. Besides, the field tests show a good agreement between the model and the real system.