Cryogenic control system of the large COMPASS polarized target

The dilution refrigerator used to cool the large COMPASS polarized target is monitored through a PC running <f>LabVIEWTM</f> 6.1 under Windows <f>2000TM</f>. About 60 parameters of the target (temperatures, pressures, flow rates) are continuously plotted and checked. They are periodically recorded in an <f>OracleTM</f> database and in a data file. An alarm for every parameter can be individually activated and optionally connected to a GSM (Global System for Mobile Communication) delivery message system. A web server receives and publishes the online status of the target with online tables and graphics on a dedicated COMPASS polarized target information web site. A Siemens programmable logic controller (PLC) powered by an uninterruptable source keeps the cryogenic system safe and stable during the long beam periods by controlling valves and interlocks. This safety feature protects the dilution refrigerator against potential damages in case of power failure. [Copyright &y& Elsevier]