A Liquid Xenon Radioisotope Camera

Abstract

The increasing availability of short lived gamma and positron emitting isotopes, coupled with the importance of dynamical studies and better imaging, has generated the need for an improved γ-ray camera. We discuss a new type of γ-ray camera which makes use of electron avalanches in liquid xenon. A configuration currently under development is shown in Fig. 1. The successful operation of a liquid xenon proportional counter was recently reported. The liquid xenon camera promises better spatial resolution and higher counting rate than the existing NaI (Tl) scintillation camera. The spatial resolution for γ rays is in principle limited only by the range of photoelectrons in liquid xenon, which is < 0. 2 mm for energies < 1 MeV. A counting rate of 106 C/s or more appears possible. As a result of the better resolution and high counting rate capability, the definition of the picture is improved. In addition, the high counting rate capability makes possible dynamic studies which were previously unfeasible. Although we expect the energy resolution with liquid xenon to be superior to that of NaI (see next section), our preliminary measurements show 17% FWHM for 279 keV γ's. Improvements are expected by using better geometry and smoother wire.