Mechanical design aspects of a soft X-ray plane grating monochromator

A plane grating monochromator based on the SX-700 concept has been construc ted for the Materials Science Beamline, Elettra, which is attached to a ben ding magnet. The tuning range is from 35 to 800 eV with calculated spectral resolving power epsilon/Delta epsilon better than 4000 in the whole range. The optical elements consist of a toroidal prefocusing mirror, polarizatio n aperture, entrance slit, plane pre-mirror, single plane grating (blazed), spherical mirror, exit slit and toroidal refocusing mirror. The plane grat ing is operated in the fixed focus mode with C-ff = 2.4. Energy scanning is performed by rotation of the plane grating and simultane ous translation and rotation of the plane pre-mirror. A novel solution is a pplied for the motion of the plane pre-mirror, namely by a translation and mechanically coupling the rotation by a cam. The slits have no moving parts in vacuum to reduce cost and increase ruggedness, and can be fully closed without risk of damage. In the first tests, a resolving power of at least 4 000 has been achieved at energies of 400 eV. The calculated photon flux at the sample is compared with measured values. (C) 2001 Elsevier Science B.V. All rights reserved.