Performance of the large-scale TPC system in the CERN heavy ion experiment NA49

The NA49 experiment uses four large volume TPCs with pad readout (182 000 electronics channels) for the large acceptance study of Pb+Pb collisions at the CERN SPS. A new, low-mass technique was developed for the construction of field cage and gasbox. Unconventional gas mixtures like Ne/CO2 (90/10) and Ar/CO2/CH4 (90/5/5) are used at drift velocities of 1.3 and 2.3 cm/μs in the unsaturated regime. Excellent stability of gas amplification and drift velocity has been achieved by putting particular emphasis on the control and understanding of all operational aspects.