Figure 2
Histograms of single pattern speckle contrast estimates β1,2 and βV, obtained from measured X-ray fluorescence photons. (a) Iron nano-stars, measured with 3 fs pulses, with the sample variance Var(β1,2) = 708 and Var(βV) = 6253. (b) Iron nano-stars, measured with 15 fs pulses, with Var(β1,2) = 11 and Var(βV) = 485. Note the long-tailed distribution with many entries at −1 and some quite high β estimates, along with the high sample variance. (c) Histogram of mean photon counts [equivalent to Fig. 1(d)], divided into four parts as indicated by four colors. (d) Histograms of speckle contrast estimates for different regions of mean photon counts. Note the transition from a long-tailed distribution with large peak at β = −1 at low 〈I〉 (blue) to a more Gaussian-like distribution for higher 〈I〉 (red). |