  Gamma-ray and fast-neutron imaging was performed with a novel liquid xenon
(LXe) scintillation detector read out by a Gaseous Photomultiplier (GPM). The
100 mm diameter detector prototype comprised a capillary-filled LXe
converter/scintillator, coupled to a triple-THGEM imaging-GPM, with its first
electrode coated by a CsI UV-photocathode, operated in Ne/5%CH4 cryogenic
temperatures. Radiation localization in 2D was derived from
scintillation-induced photoelectron avalanches, measured on the GPM's segmented
anode. The localization properties of Co-60 gamma-rays and a mixed
fast-neutron/gamma-ray field from an AmBe neutron source were derived from
irradiation of a Pb edge absorber. Spatial resolutions of 12+/-2 mm and 10+/-2
mm (FWHM) were reached with Co-60 and AmBe sources, respectively. The
experimental results are in good agreement with GEANT4 simulations. The
calculated ultimate expected resolutions for our application-relevant 4.4 and
15.1 MeV gamma-rays and 1-15 MeV neutrons are 2-4 mm and ~2 mm (FWHM),
respectively. These results indicate the potential applicability of the new
detector concept to Fast-Neutron Resonance Radiography (FNRR) and
Dual-Discrete-Energy Gamma Radiography (DDEGR) of large objects.
