A cloud chamber triggered by the electroluminescence of its He+Xe filling mixture a new instrument for investigating double beta-decay

The features and possibilities of a ''self-triggered'' cloud chamber are described. The instrument is essentially an expansion cloud chamber, filled with He and Xe (Xe acts as condensable vapour), which works at nearly 150 K, and which can be triggered by the electroluminescence of its filling mixture when a ionizing event occurs within. We report the results obtained in several investigations undertaken to answer the various problems which arise when facing the design of a self triggered cloud chamber. In particular a prototype of He+Xe cloud chamber, which operated successfully between 140 K and 165 K, is described, and several data on the electroluminescence of He+Xe mixtures are given. The features of a ''self-triggered'' cloud chamber are discussed considering its possibilities as an instrument for investigating the double beta decay of 136Xe