Six-circle diffractometer for surface diffraction using an in-vacuum x-raydetector

We report on the design of a diffractometer, which offers improved capabili ties for x-ray experiments in ultrahigh vacuum. Its main features are (i) t he possibility to follow the evolution of diffraction spots in situ during adsorption or film deposition; (ii) the measurement of reflections at high exit angles, i.e., large perpendicular momentum transfer. This goal is achi eved by placing a movable x-ray detector inside the vacuum chamber. (iii) O ther surface analysis equipment, e.g., a low-energy electron diffraction or an electron energy analyzer can be moved in front of the sample and operat ed simultaneously with x-ray diffraction. (iv) A load lock system-currently in preparation-will allow the quick exchange of samples without breaking s ystem vacuum. In addition, a new design of the chi circle used for sample a lignment provides a compact, space-saving design of the diffractometer. (C) 1999 American Institute of Physics. [S0034-6748(99)02608-8].