Synchrotron Produces Femtosecond Pulses

A team at Lawrence Berkeley National Laboratory's Advanced Light Source in Berkeley, Calif., reported in the March 24 issue of Science that it had produced 300-fs x-ray pulses with the facility's 1.5-GeV synchrotron. Improved designs should produce 100-fs pulses for directly probing the atomic-scale structural dynamics of condensed matter.

The researchers injected a femtosecond pulse from a Ti:sapphire laser into a resonantly tuned wiggler magnet with a 30-ps electron bunch. Bend magnets separated the x-rays from the energy modulation produced in the electrons.

Plans are under way to decrease the distance between the magnets, a move that is expected to yield 100-fs pulses. Replacing the bend magnets with an undulator should increase the flux to 10⁷ photons per second for studies using time-resolved x-ray diffraction and extended x-ray absorption fine structure.