  We calculate signals of real photon-photon scattering in the collision of
three laser pulses. Taking goal parameters from the Station of Extreme Light at
the upcoming Shanghai Coherent Light Source, we consider two scenarios: i) the
collision of three optical pulses; ii) the collision of an XFEL with two
optical pulses. Although experimentally more difficult to perform, we find that
colliding three laser pulses offers certain advantages in the detection of
scattered photons by separating their frequency, momentum and polarisation from
the background.

High Energy Physics - Phenomenology;Optics