  NEXT-DEMO is a high-pressure xenon gas TPC which acts as a technological
test-bed and demonstrator for the NEXT-100 neutrinoless double beta decay
experiment. In its current configuration the apparatus fully implements the
NEXT-100 design concept. This is an asymmetric TPC, with an energy plane made
of photomultipliers and a tracking plane made of silicon photomultipliers
(SiPM) coated with TPB. The detector in this new configuration has been used to
reconstruct the characteristic signature of electrons in dense gas.
Demonstrating the ability to identify the MIP and "blob" regions. Moreover, the
SiPM tracking plane allows for the definition of a large fiducial region in
which an excellent energy resolution of 1.82% FWHM at 511 keV has been measured
(a value which extrapolates to 0.83% at the xenon Qbetabeta).
