A Double Multilayer Monochromator at an ESRF Undulator for Microbeam Experiments

A water‐cooled double W/Si‐multilayer monochromator has been operated at an ESRF low‐ β undulator beam. For a fixed distance of the two multilayers the first‐order Bragg reflection was at ~8 keV. The peak power density of the beam at the exit of the multilayers was ~1 W mm −2 and the flux density of the first order after a 10 μm collimator was 4 × 10 5 photons s −1 μm −2 mA −1. The performance of the beam in microbeam diffraction has been tested on a 20 μm W wire. The observed pseudo‐Laue pattern is discussed with respect to the multilayer spectrum.