HIGH-RESOLUTION IN THE SOFT-X-RAY RANGE FROM A TOROIDAL GRATING MONOCHROMATOR

A resolving power, E/DELTAE, of greater-than-or-equal-to 13 000 has be en achieved with the modified 6 m/160-degrees toroidal grating monochr omator (TGM) installed on Beam Line 8-1 at the Stanford Synchrotron Ra diation Laboratory. The resolving power of the TGM was increased by re placing the entrance and exit slits with high-precision slits, masking the horizontal part (short radius) of the grating, and improving the TGM scanning mechanisms. To determine the performance of the monochrom ator, we measured the dependences of resolution and photon flux on the entrance- and exit-slit widths, the exit-slit position, and the maski ng of the grating. The monochromator resolution in the energy range of 25-65 eV was derived from photoionization measurements of extremely n arrow core-excitation resonances in He and Ne. With 10-mum vertical en trance- and exit-slit widths and 32% mask opening of the grating, the monochromator has a resolution (full-width at half maximum) of 5.0+/-0 .7 meV at a photon energy of 64.5 eV and a flux of 2 X 10(7) photons/s /100 mA. The results suggest a simple procedure for converting a TGM w ith moderate resolution into a high-resolution monochromator with a mo derate reduction in photon flux due to masking the grating, beyond the reduction attributable to the slit widths.