We report on the initial test of undulator tuning for the beamline BL10XU at Spring-8. The optics of BL10XU is quite simple, i.e., major optical components are a rotated-inclined double crystal monochromator designed by Ishikawa and a double flat mirror. One of a standard in-vacuum type undulator (U032V) is used. Since a typical energy range of - 1 keV is required as a routine EXAFS scan, both monochromator and undulator gap should be controlled during a scan; an undulator gap is varied so that a monochromator acceptance can track the undulator peak. On varying an undulator gap from 9.6 mm to 22 mm, a wide energy range (5-30 keV) is covered. We demonstrate that undulator tuning can provide glitch-free transmission spectra with a high energy resolution (1.5 eV at 9 keV) .
