  The interaction of radiation with liquid xenon, inducing both scintillation
and ionization signals, is of particular interest for Compton-sequences
reconstruction. We report on the development and recent results of a
liquid-xenon time-projection chamber, dedicated to a novel nuclear imaging
technique named "3 gamma imaging". In a first prototype, the scintillation is
detected by a vacuum photomultiplier tube and the charges are collected with a
MICROMEGAS structure; both are fully immersed in liquid xenon. In view of the
final large-area detector, and with the aim of minimizing dead-zones, we are
investigating a gaseous photomultiplier for recording the UV scintillation
photons. The prototype concept is presented as well as preliminary results in
liquid xenon. We also present soft x-rays test results of a gaseous
photomultiplier prototype made of a double Thick Gaseous Electron Multiplier
(THGEM) at normal temperature and pressure conditions.
