On the optical design of heat-loaded double-crystal monochromators for synchrotron radiation

It is shown that a suitably curved second crystal can compensate for the thermal distortion of the first crystal in synchrotron-radiation double monochromators. It is further shown that the compensation can work at very high heat loads. The reflection efficiency can be fully restored and, because of increased reflectivity in a curved crystal, even enhanced. The rocking-curve width can also be restored to the value for two flat crystals at moderate heat loads for silicon monochromators and at any heat load for germanium monochromators.