Energy resolution in ionization chamber filled with liquefied rare gases at an elevated temperature.

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Ionization chambers filled with liquefied rare gases exhibit good energy resolution and good linearity of output signals to the deposited energy. For example, liquid argon calorimeters have been used in high physics experiments. Theoretically, however, far better energy resolution is expected than those experimentally obtained. The purpose of the present work is to obtain the excellent energy resolution as expected by the theory, or to investigate the disagreement of the theory and the experiment on the energy resolution.We investigated the energy resolution in ionization chambers filled with liquefied rare gases doped with photo-ionizing molecules. We found that the energy resolution is improved by doping liquid rare gases with photo-ionizing molecules only at relatively low electric fields and that the improvement is little at high fields, in contrast to the estimation based on the 'Recombination model' proposed by Thomas et al. We concluded that the 'Recombination model' is not the case [1]. Investigating the ionization yield and scintillation yield in liquefied rare gases, we made a comment [2] on a paper by Seguinot et al. As a typical case of high ionization density, we studied the ionization yield and the energy resolution for relativestic heavy ions in liquid argon calorimeter doped with photo-ionizing molecules [3].The excellent energy resolution as expected by the theoretical estimation is not obtained so far. We, however, have improved the experimental apparatus such as purifier of rare gases. We would like to make more experiments by using improved electronics system.