SEMINAR      Monday, 22 November 2004 - h. 15:00  Auditorium B. Touschek     A. Longoni (Politecnico, Milano ) Silicon Drift Detectors for X and Gamma ray spectroscopy and imaging.   Abstract The principle of Silicon Drift Detectors (SDDs) was introduced and experimented by E.Gatti and P.Rehak in 1983. Their aim was to develop an advanced position sensitive detector for minimum ionizing particle. After the magic moment of the invention, an international cooperation of several researchers worked for years to bring the SDDs from a beautiful concept to the reliable and versatile detector of today. During these years new devices, based on the original concept of the SDD, have been conceived: the Single Side Drift Detector for X-ray spectroscopy, the Controlled Drift Detector and the PN Charge-Coupled Detector for X-ray spectroscopy and imaging, the Scintillator-Coupled Multi-element Drift Detector for Gamma-ray imaging. Most of the existing devices concern nowadays X-ray detection, while a few large area arrays of Position Sensitive SDDs have been applied, or will be applied, in high energy heavy ions experiments. In particular, SDDs are nowadays the best detector for X-ray Fluorescence Spectrometers. Their application ranges from the fundamental science to the applied technology, from the archaeometry to the forensic investigations. After a review of the principles of the SDDs, the basic structures of the modern devices based on the SDD concept are introduced in the Seminar and their performances and applications discussed.