Mapping device for INTEGRAL/SPI single detectors

The INTEGRAL gamma-ray spectrometer SPI being a system of 19 HPGe detectors combined with a coded mask aperture will provide sky images. In order to m ake possible the deconvolution of these images, the response of the detecti on plane must be well known. A first experiment of a single detector effici ency mapping revealed great variations. Then it is clear that a detailed st udy of the local efficiency of the detectors as a function of position and angle of incident photons is needed. In this paper we present a setup allow ing such studies. Performance and limitations of this mapping system are pr esented, illustrated by the first results obtained for one SPI detector. We present also results of the Monte Carlo simulation of the experiment.