  The idea of searching for gravitational waves using cavities in strong
magnetic fields has recently received significant attention. Most concepts
foresee moderate magnetic fields in rather small volumes, similar to those
which are currently employed for axion-like particle searches. We propose to
use the magnet system of the Compact Muon Solenoid (CMS) experiment after the
high luminosity phase of the LHC as a key component for a future detector for
gravitational waves in the MHz frequency range. In this paper we briefly
discuss a possible cavity concept which can be integrated into CMS and
additionally provide a first estimation of its possible sensitivity.
