Credit: SLAC National Accelerator Laboratory
X-ray lasers amplify X-ray pulses (shown within the blue ovals) from electron beams (depicted as arrows) inside magnets known as undulators (left). Top: Each pulse normally contains a spectrum of X-ray colors and intensities that changes from pulse to pulse. Bottom: A technique known as echo-enabled harmonic generation (EEHG) could produce stable pulses containing a single X-ray color that vary very little from shot to shot.