The quality of x-ray spectra and images obtained from plasmas with spherically bent crystals
depends in part on the crystal's x-ray diffraction across the entire crystal surface. We employ
the energy selectivity and high intensity of synchrotron radiation to examine typical spherical
crystals from alpha-quartz for their diffraction quality, in a perpendicular geometry that is
particularly convenient to examine sagittal focusing. The crystal's local diffraction is not ideal:
the most noticeable problems come from isolated regions that so far have failed to correlate …