Method for background reduction in an experiment devoted to WIMP searches with a liquid-xenon (liquid-argon) ionization chamber

A method for detecting ultraviolet photons from Xe-2(*) deexitation with an efficiency of nearly 100% is proposed. This method allows a reliable discrimination between Xe (Ar) recoil nuclei and background electrons. As a result, the beta and gamma background is almost completely suppressed. The neutron background can be reduced by water shielding and by selection of events involving only one recoil nucleus. The developed grid screen will remove the photon feedback. The small prototype TPC with a preliminary multiplication of ionization electrons in a proportional gap and a subsequent detection of the multiplied charges in the induction gap is constructed. The shape of an electron component of the proportional signal is obtained in this chamber For Penning mixtures. A chamber 636 mm long is now being prepared for WIMP searches. A background of about 10(-5) event/(keV kg d) can be obtained in this experiment. (C) 2000 MAIK "Nauka/Interperiodica".