The electronic response of 2,2,4,4 tetramethylpentane to minimum ionizing particles

We report an ion chamber measurement of the electron mobility and free ion yield of liquid 2,2,4,4 tetramethylpentane for single minimum ionizing particles. A waveform analysis technique was used to measure clearly systematic effects due to amplifier shaping and electron trapping contaminants. A high degree of purification, corresponding to a free electron lifetime of 121 μs, was achieved by nonchemical means. The mobility and zero field free ion yield obtained are 26.3 ± 0.8 cm2/V s and 0.743 ± 0.029 electrons/100 eV, respectively. The ion yields are discussed in the framework of Onsager's model. (orig.)