High energy-resolution x-ray spectroscopy at ultra-high dilution with   spherically bent crystal analyzers of 0.5 m radius
  We present the development, manufacturing and performance of spherically bent crystal analyzers (SBCAs) of 100 mm diameter and 0.5 m bending radius. The elastic strain in the crystal wafer is partially released by a "strip-bent" method where the crystal wafer is cut in strips prior to the bending and the anodic bonding process. Compared to standard 1 m SBCAs, a gain in intensity is obtained without loss of energy resolution. The gain ranges between 2.5 and 4.5, depending on the experimental conditions and the width of the emission line measured. This reduces the acquisition times required to perform high energy-resolution x-ray absorption and emission spectroscopy on ultra-dilute species, accessing concentrations of the element of interest down to, or below, the ppm (ng/mg) level. 
Mauro Rovezzi, Christophe Lapras, Alain Manceau, Pieter Glatzel and   Roberto Verbeni
physics.ins-det