Diamond monochromators for APS undulator-A beamlines

There has been considerable interest in the use of diamonds in high heat load monochromators (HHLMs) in the last several years. The superb thermal and mechanical properties of single crystal diamonds serve to minimize distortions caused by a given thermal load, while the low x-ray absorption cross-section reduces both the total power deposited in the crystal as well as the peak (volumetric) power density. The primary obstacle for the widespread use of diamonds at present is a lack of ready availability of perfect single crystals of the desired size and orientation. Although it is possible to obtain near-perfect natural diamonds of the size and orientation required for use on an undulator beamline, the selection process is generally one of trial and error. Near perfect synthetic diamonds can currently be obtained in the minimum necessary size (typically 4-5 mm on a side). A collaborative agreement has been made between the staff of the Advanced Photon Source (APS), the European Synchrotron Radiation Facility (ESRF), and the Super Photon Ring-8 GeV (SPring-8) to explore the use of diamonds as high heat load monochromators and is on-going. One of the avenues of research is to push for improved perfection and size of synthetic diamonds. Sumitomo Electric Corporation of Japan has agreed to work with staff from SPring-8 to grow [100] oriented perfect single crystal diamonds of 10 x 10 x 1 mm{sup 3} size by 1996/1997 (from which one could also cut pieces with the large face parallel to the (111) planes). They have taken the first step in producing an essentially perfect 4 x 4 x 1 mm{sup 3} type II diamond with less than 5 {mu}rad (1 arc second) strain (measured over the entire surface). The authors believe progress in the production of synthetic diamonds, as well as improvement in ties with suppliers of natural diamonds, should make available a relatively large number of high quality diamonds of moderate size within the next several years.