A resolving power,E/Dgr;E, of ge;13thinsp;000 has been achieved with the modified 6 m/160deg; toroidal grating monochromator (TGM) installed on Beam Line 8hyphen;1 at the Stanford Synchrotron Radiation Laboratory. The resolving power of the TGM was increased by replacing the entrance and exit slits with highhyphen;precision slits, masking the horizontal part (short radius) of the grating, and improving the TGM scanning mechanisms. To determine the performance of the monochromator, we measured the dependences of resolution and photon flux on the entrancehyphen; and exithyphen;slit widths, the exithyphen;slit position, and the masking of the grating. The monochromator resolution in the energy range of 25ndash;65 eV was derived from photoionization measurements of extremely narrow corehyphen;excitation resonances in He and Ne. With 10hyphen;mgr;m vertical entrancehyphen; and exithyphen;slit widths and 32percnt; mask opening of the grating, the monochromator has a resolution (fullhyphen;width at half maximum) of 5.0plusmn;0.7 meV at a photon energy of 64.5 eV and a flux of 2times;107photons/s/100 mA. The results suggest a simple procedure for converting a TGM with moderate resolution into a highhyphen;resolution monochromator with a moderate reduction in photon flux due to masking the grating, beyond the reduction attributable to the slit widths.
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