  In the storage ring of PLS-II, we reduced mechanical displacement of electron
beam position monitors (e-BPMs) that is caused by heating during e-beam
storage. The orbit feedback system intends that the electron beam pass through
the center of the BPM, so to provide stable photon beam into beamlines the BPM
pickup itself must be stable to sub-micrometer precision. Thermal deformation
of the vacuum chambers on which the BPM pickups are mounted is inevitable when
the electron beam current is changed by unintended beam abort. We reduced this
deformation by improving the vacuum chamber support and by enhancing the water
cooling. We report the thermo-mechanical analysis and displacement measurements
of BPM pickups after the improvements.
