The AGILE Silicon Tracker: testbeam results of the prototype silicon detector

AGILE (Light Imager for Gamma-ray Astrophysics) is a small scientific satellite for the detection of cosmic gamma-ray sources in the energy range 30 MeV-50 GeV with a very large field of view (1/4 of the sky). It is planned to be operational in the years 2003-2006, a period in which no other gamma-ray mission in the same energy range is foreseen.
The heart of the AGILE scientific instrument is a silicon-tungsten tracker made of 14 planes of single sided silicon detectors for a total of 43 000 readout channels. Each detector has a dimension of 9 5 x 9 5 cm(2) and a thickness of 410 mum.
We present here a detailed description of the performance of the detector prototype during a testbeam period at the CERN PS in May 2000. The Tracker performance is described in terms of position resolution and signal-to-noise ratio for on and off-axis incident charged particles. The measured 40 pm resolution for a large range of incident angles will provide an excellent angular resolution for cosmic gamma-ray imaging.