A NEVI 1'AONOCHROMATOR FOR HIGH HEAT LOAD SYNCHROTRON X-RAY RADIATION* Abstract

Ali Khounsary Advanced Photon Source Argonne National Laboratory Argonne,IL60649 The high heat load associated with the powerful and concentrated x-ray beams generated by insertion devices (IDs) at a number of present and many of the future (planned or under construction) synchrotron radiation facilities poses a formidable engineering challenge for the design of monochromators and other optical devices. Successful utilization of the intense x-ray beams from insertion devices depends critically on the development, design, and availability of optical elements that will provide acceptable performance under high heat load. Present mono chroma tors can handle, at best, heat load levels that are an order of magnitude lower than those generated by these IDs. The monochromator described here, and referred to as the "inclined" monochromator, can provide a solution to the high heat load problem. The inclined monochromator is different in a number of aspects from other conventional monochromators. Its primary differentiating characteristic is in the orientation of the diffracting planes. In the inclined geometry, the crystal surface normal and the normal to the diffracting crystal planes make an angle close to 90°. This leads to a number of interesting effects including spreading of the beam over a very large area (effectively reducing the incident heat flux), and also rendering a much smaller effective slope error. Thus, a substantial enhancement in the performance of the monochromator is realized. The preliminary results of a comparative numerical simulation of the performance of the inclined monochromator under the 5 kW power APS Undulator A beam are encouraging and provide a quantitative estimate of the expected enhancement. . * A version of this paper has been submitted for publication in the Rev. Sci. Instrum., 1991 The submitted manuscript has been authored by a contractor of the U. S. Government under contract No. W-31-109-ENG-38. Accordingly, the U. S. Government retains a nonexclusive, royalty~free license to publish or reproduce the published form of this contribution, or allow others to do so, for U. S. Government purposes.