The source size and the spatial coherence length were derived from an interferometric technique in which a Boron fiber is inserted into the beam in order to produce a Fresnel interference pattern.

From the visibility of interference fringes a vertical source size of 82.1 micrometers was derived.

For details see:
Ref. "Direct Measurement of Transverse Coherence Length of Hard X-Rays from Interference Fringes", V. Kohn, I . Snigireva, A. Snigirev, Phys. Rev. Lett., Vol. 85, Number 13, 25 (2000)