  The CMS tracker consists of 206 square meters of silicon strip sensors
assembled on carbon fibre composite structures and is designed for operation in
the temperature range from -25 to +25 degrees C. The mechanical stability of
tracker components during physics operation was monitored with a few micron
resolution using a dedicated laser alignment system as well as particle tracks
from cosmic rays and hadron-hadron collisions. During the LHC operational
period of 2011-2013 at stable temperatures, the components of the tracker were
observed to experience relative movements of less than 30 microns. In addition,
temperature variations were found to cause displacements of tracker structures
of about 2 microns/degree C, which largely revert to their initial positions
when the temperature is restored to its original value.
