  Intensity interferometry is a well known method in astronomy. Recently, a
related method called incoherent diffractive imaging (IDI) was proposed to
apply intensity correlations of x-ray fluorescence radiation to determine the
3D arrangement of the emitting atoms in a sample. Here we discuss inherent
sources of noise affecting IDI and derive a model to estimate the dependence of
the signal to noise ratio (SNR) on the photon counts per pixel, the temporal
coherence (or number of modes), and the shape of the imaged object. Simulations
in two- and three-dimensions have been performed to validate the predictions of
the model. We find that contrary to coherent imaging methods, higher
intensities and higher detected counts do not always correspond to a larger
SNR. Also, larger and more complex objects generally yield a poorer SNR despite
the higher measured counts. The framework developed here should be a valuable
guide to future experimental design.
