Time delay compensating monochromator based on reflection zone plates

We present the sequential combination of two identical reflection zone plates (RZPs) placed in opposite orders of diffraction (+1st and −1st). The scheme compensates for the time elongation of monochromatized (E/∆E ≲ 500), femtosecond (fs) soft X-ray pulses with an energy E ~ (0.1 − 1) keV down to ≈ 10 fs or less.