Performance of Beryllium Crystals Exposed to High X-Ray Power Density

High quality beryllium single crystals are currently proposed for several applications in synchrotron radiation X-ray optics, in particular as the first element which will have to take the high power of the beam generated by insertion devices. Beryllium has the advantage that much of this incident radiation is transmitted, especially higher energy wiggler radiation. Therefore, it is important to know how Be crystals behave under high X-ray power. For test measurements the focused wiggler beam of the beamline X25 at the National Synchrotron Light Source, Brookhaven, that provides a powder of 75 W at 230 mA ring current and a peak power density > 200 W/mm exp 2 was used. A Be crystal was positioned in this white beam and its reflection properties were studied using a perfect Si analyzer crystal. An "ideal mosaic" type rocking curve 58 arcsec wide was obtained with a strongly attenuated beam increasing to 73 arcsec at 200 W/mm exp 2 . No deterioration of the crystal was observed. Much better performance is expected for thinner crystals. It can be concluded that presently available Be single crystals have the properties required for currently proposed applications as first optical element.