The JLab12 Bari group is currently mainly involved in the development of the GEM tracker for 12 GeV Physics at SBS-Hall A. In particular, it is responsible for the gas mixture distribution and control system (GasDCS).
The GEM chambers are feeded with a nominal 70%/30% mixture of Argon (Ar) and Carbon Dioxide "CO<sub>2</sub>", with flows equivalent to 1-3 Volumes/hour with accuracies of 1% of the full scale. The control hardware is based on MKS mass flowmeters which are connected to a central unit MKS MultiGasController 647C. The control software has been developed in the NI-LabVIEW framework and allows the user to set flow parameters through a configuration file; to monitor continuously the flow measured values; to show the data in alphanumeric and graphic displays. The system is also completed with differential pressure transmitters which monitor the pressure status at the gas inlets and outlets of the chamber, as well as the temperature on chambers by means of resistive temperature sensors. The acquired data are stored on disk with timestamps for the record and off-line analysis, and in addition is also broadcast on the local area network and can be accessed by through TCP/IP protocol.