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In the silicon drift detectors, the charge produced by the ionizing radiation is brought, with a constant speed, to a small number of collecting electrodes (anodes).
The measurement of the spatial coordinates of the impact point is provided by the time taken by the charge to reach the collecting electrodes (drift time) in a direction, and by the anodes segmentation in the other direction.
The collecting electrodes are small; this allows a low noise level and an excellent energetic resolution as well as a high spatial resolution of 20 µm in the two coordinates employing a small number of channels.
4. Detail of the drift detector near the collecting anodes, the little silver rectangles (pitch 200 µm). The electrodes which set the drift field are also visible
In this type of development, the Laboratory of Trieste is one of the most advanced in the world. Among the different applications of silicon drift detectors, there are experiments with heavy ions (CERN-LHC, BNL-RHIC) which require the capability of analysing a large number of simultaneous tracks unambiguously.
This is also a versatile detector. At present, a collaboration under way with the CARSO Laboratory (Area di Ricerca, Trieste) foresees the application of these detectors to astronomy.