Measurement of the positive ions drifting in liquid or gaseous xenon

Several tests on injection and transport of positive ions were made in liquid and gaseous Xe, which are parts of our research program of double beta decay of 136Xe. In measurements a event of double beta decay is identified by detecting a couple of electrons emitted at the decay and the daughter isotope 136Ba with resonance ionization spectrometry, where we believe that we are almost free from the backgrounds in the measurements. The injection efficiency and drift velocity of positive ions are key parameters in the program. We initiated an experiment of injection and transport of 208Tl ions in liquid and gaseous Xe. At present, we obtained reliable results of the injection and transportation. However the drift velocity of the positive ions was not determined yet because of the statistical error in 208Tl decay counts. We here report the methods of the experiments and the results obtained so far. (J.P.N.)