Gas Gain Stabilisation System prototype for the TRT

The TRT closed-loop gas system needs a special control and monitoring functionality which should maintain a stability of gas gain in spite of unavoidable changes in gas composition and variation of environmental conditions (temperature, pressure etc.). We describe a prototype set-up for the Gas Gain Stabilisation System build and tested at CERN on which basic ideas for algorithms and functionalities were tested. The system is based on special counter - reference straw, where X-ray 55Fe spectrum is measured. Preliminary results of the prototype reaction to rapid changes in working gas pressure and temperature are presented.