Thermal influences of the front-end electronics on the Alice TPC readout chamber

The Alice TPC detector will be operated with a gas mixture of 90% Ne and 10% CO₂ at the electric field of 400 V/cm. Recent studies favor a three-component mixture by adding about 5% N₂, which will improve the stability of the gas against discharges. These operating parameters lead to a non-saturated drift velocity for electrons but also impose that all external influences on the drift gas must be reduced to minimum. The most problematic influence is temperature variation, which can lead to local fluctuation in the gas density and therefore directly affects the drift velocity. For the Alice TPC, the aim is to have a temperature stability of 0.1°C over the full drift length (2.5 m). The main heat contribution comes from the readout chambers front-end electronics and one estimates that a total of 30.2 kW must be removed. The test results discussed here give qualitative and quantitative information about the thermal behavior of the chambers for validation of the TPC cooling strategy.