Preserving the high finesse of X-ray undulator beams from perfect water-jet-cooled diamond monochromators

A perfect single crystal of isotopically enriched diamond is shown to be an excellent X-ray monochromator for future undulator beams when jet-cooled with water. Unprecedented power densities, up to 260 W/mm2 with 63 W total X-ray power are provided by the focussed X-ray beam from a 27 pole hybrid wiggler on beamline X25 at NSLS. Double crystal rocking curves have full widths at half maximum intensity of 3-4 arc sec which are determined by mounting strain and coolant pressure effects rather than the thermal strainfield. (orig.)