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The global degree of coherence (black line) and the focal size (red line) as functions of the beam-defining aperture size 
in the horizontal (a) and vertical (b) directions. The dashed line indicates a highly coherent beam with the coherence length in the focus being twice as large as the r.m.s. beam size, 
= 
. (c) The increase in the flux density 
as a function of the beam-defining aperture size in the horizontal (blue dashed line) and vertical (green dotted line) directions.
