  We reinvestigate the gravitational waves (GWs) induced by charged particles
in storage rings. There are two major components in such GWs. One is the
gravitational synchrotron radiation (GSR), i.e., the direct emission by the
bending of the trajectory of a relativistic charged particle, much like the
conventional electromagnetic synchrotron radiation (EMSR), albeit with
characteristic difference in their radiation spectra. While the conventional
EMSR spectrum peaks at the critical frequency,
$\omega_c=\gamma^3\omega_0\gg\omega_0$, the spectrum of GSR peaks at the
storage ring fundamental frequency $\omega_0$, which is much lower. The other
is the resonant conversion of EMSR to GWs at the same frequency through the
storage ring bending magnets, i.e., the Gertsenshtein effect. Invoking LHC at
CERN as a numerical example, we found that the spacetime perturbation
associated with GSR, $h\sim 5\times 10^{-40}$, falls far below the sensitivity
of GW detectors based on the LIGO-type Michelson interferometry approach. On
the other hand, the GWs induced by the resonant conversion of EMSR have much
higher frequencies and thus much localized, so it is conceivable to detect them
through the reverse conversion, the so-called `light shining through a wall',
process.
