  The XENON experiment aims at the direct detection of dark matter in the form
of WIMPs (Weakly Interacting Massive Particles) via their elastic scattering
off Xenon nuclei. With a fiducial mass of 1000 kg of liquid xenon, a
sufficiently low threshold of ~16 keV recoil energy and an un-rejected
background rate of 10 events per year, XENON would be sensitive to a
WIMP-nucleon interaction cross section of 10^(-46) cm^2, for WIMPs with masses
above 50 GeV. The 1 tonne scale experiment (XENON1T) will be realized with an
array of ten identical 100 kg detector modules (XENON100). The detectors are
time projection chambers operated in dual (liquid/gas) phase, to detect
simultaneously the ionization, through secondary scintillation in the gas, and
primary scintillation in the liquid produced by low energy recoils. The
distinct ratio of primary to secondary scintillation for nuclear recoils from
WIMPs (or neutrons), and for electron recoils from background, is key to the
event-by-event discrimination capability of XENON. A 3kg dual phase detector
with light readout provided by an array of 7 photomultipliers is currently
being tested, along with other prototypes dedicated to various measurements
relevant to the XENON program. We present some of the results obtained to-date
and briefly discuss the next step in the phased approach to the XENON
experiment, i.e. the development and underground deployment of a 10 kg detector
(XENON10) within 2005.
