  Inverse Compton Scattering (ICS) has gained much attention recently because
of its promise for the development of table-top-size X-ray light sources.
Precise and fast simulation is an indispensable tool for predicting the
radiation property of a given machine design and to optimize its parameters.
Instead of the conventional approach to compute radiation spectra which
directly evaluates the discretized Fourier integral of the Li\'enard-Wiechert
field given analytically (referred to as the frequency-domain method), this
article focuses on an approach where the field is recorded along the observer
time on a uniform time grid which is then used to compute the radiation spectra
after completion of the simulation, referred to as the time-domain method.
Besides the derivation and implementation details of the proposed method, we
analyze possible parallelization schemes and compare the parallel performance
of the proposed time-domain method with the frequency-domain method. We will
characterize scenarios/conditions under which one method is expected to
outperform the other.
