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Silicon photomultiplier demonstrates its capabilities
A team from the Moscow Engineering and Physics Institute together with
Pulsar Enterprise in Moscow have developed a silicon photomultiplier
(SiPM), which promises a wide range of applications. The device is
basically a large number (103/mm2)
of microphoton counters, which are located on a common silicon
substrate and have a common output load. Each photon counter is a small
(20-30 µm square) pixel with a depletion region of 2 µm. They are
decoupled by polysilicon resistors and operate in a limited Geiger mode
with a gain of 106. This means that the SiPM is sensitive to
a single photoelectron, with a very low noise level of less than 0.1
photoelectron. Although each SiPM pixel operates digitally as a binary
device, as a whole the SiPM is an analogue detector that can measure
light intensity within a dynamic range of about 103/mm2 and has excellent photon capability.
The photon detection efficiency of the SiPM is at the level of
photomultiplier tubes (PMTs) in the blue region (20%), and is higher in
the yellow-green region. The device has very good timing resolution (50
ps r.m.s. for one photoelectron) and shows very good temperature
stability. It is also insensitive to magnetic fields. These
characteristics mean that the SiPM can compete with other known
photodetectors (e.g. PMT, APD, HPD, VLPC) and may prove useful for many
applications, from very low light intensity detection in particle
physics and astrophysics, through fast luminescence and fluorescence
studies with low photon numbers in chemistry, biology and material
science, to fast communication links.
Further reading
www.slac.stanford.edu/pubs/icfa/fall01.html
B Dolgoshein Int. Conf. on New Developments in Photodetection (Beaune, France) June 2002.
Article 7 of 20.
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