We present the first measurements of the electroluminescence response to the emission of single electrons in a two-phase noble gas detector. Single ionization electrons generated in liquid xenon are detected in a thin gas layer during the 31-day background run of the ZEPLIN-II experiment, a two-phase xenon detector for WIMP dark matter searches. Both the pressure dependence and magnitude of the single-electron response are in agreement with previous measurements of electroluminescence yield in xenon. We discuss different photoionization processes as possible cause for the sample of single electrons studied in this work. This observation may have implications for the design and operation of future large-scale two-phase systems.
@article{arxiv.0708.0768,
title = {Measurement of single electron emission in two-phase xenon},
author = {B. Edwards and H. M. Araujo and V. Chepel and D. Cline and T. Durkin and J. Gao and C. Ghag and E. V. Korolkova and V. N. Lebedenko and A. Lindote and M. I. Lopes and R. Luscher and A. St. J. Murphy and F. Neves and W. Ooi and J. Pinto da Cunha and R. M. Preece and G. Salinas and C. Silva and V. N. Solovov and N. J. T. Smith and P. F. Smith and T. J. Sumner and C. Thorne and R. J. Walker and H. Wang and J. T. White and F. L. H. Wolfs},
journal= {arXiv preprint arXiv:0708.0768},
year = {2008}
}