From: Chiara Guazzoni <>
Newsgroups: milano.seminari
Subject: 25-10-04 Review of Semiconductor Drift Detectors
Date: Fri, 15 Oct 2004 14:59:11 +0200
 Milano - Piazza Leonardo da Vinci, 32 - 20133 Milano - Italy
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Il giorno 25 ottobre 2004
alle ore 10:15 nella Sala Alfa
Dip. Elettronica e Informazione
Politecnico di Milano
Via Golgi, 40 - Piano Terra

Il Dr. Pavel REHAK
del Brookhaven National Laboratory
(co-inventore dei Semiconductor Drift Detectors insieme al Prof. Emilio 

terra' un seminario dal titolo


About 20 years ago a new charge transport scheme for signal carriers in 
semiconductor detectors was suggested. Soon after, the first working 
example of the Silicon Drift Detector was presented. The unusual 
features of silicon drift detectors and similar structures was a 
controlled transport of signal charge carriers in a direction parallel 
to large surface of the wafer. At that time almost all radiation 
detectors made from high resistivity silicon wafer transported the 
signal charge in the ditrection perpendicular to the detector surface. 
Position sensing in these traditional detectors was accomplished by the 
division of electrodes, that is, by granularity of the readout. The main 
ideas behind this charge transport in semiconductor drift detectors will 
be shortly presented. Due to this transport mechanism the signal charge 
finally arrives to a very small electrode, called anode. The traveling 
time of signal carriers from the position of their creation to the anode 
provides the positional information for drift detectors. A single 
collecting strip-like electrode of the linear drift detector provides 
equivalenty information to all channels  of a well known single -sided 
strip detector, however, having substantially longer read-out time. When 
this strip-like electrode is divided into shorter segments a detector 
which provides an unambiguous two coordinate readout is obtained. Such a 
drift detector with a modest number of readout channels is equivalent to 
a full blown pixel detector. Examples of vertex detectors based on 
silicon drift technology will be given.
The most important application of silicon drift detectors is in the 
neighbor field of X-ray spectroscopy. The maximum advantage is taken 
from a very small capacitance of the collecting electrode which has a 
point-like shape. The small capacitance together with an improved 
technology of the production of detectors created a room temperature 
spectroscopy with the performance traditionally limited to detectors 
cooled down to liquid nitrogen temperature (77K).

Per informazioni: Chiara Guazzoni - - 
Tel. 02 - 23996147.