Abstract:

LXeGRIT is a balloon-borne Compton telescope based on a liquid xenon time projection chamber (LXeTPC) for imaging cosmic gamma-rays in the energy band of 0.2- 20 MeV. The detector, with 400~cm² area and 7 cm drift gap, is filled with high purity LXe. Both ionization and scintillation light signals are detected to measure the energy deposits and the three spatial coordinates of individual gamma -ray interactions within the sensitive volume. The TPC has been characterized with repeated measurements of its spectral and Compton imaging response to gamma -rays from radioactive sources such as Na, Cs, Y and Am-Be. The detector shows a linear response to gamma -rays in the energy range 511 keV -4.4 MeV, with an energy resolution (FWHM) of Delta E/E=8.8% : sqrt(1MeV /E). Compton imaging of Y gamma -ray events with two detected interactions is consistent with an angular resolution of ~ 3 degrees (RMS) at 1.8 MeV.