Guest Editors' Introduction: Special issue on high resolution X‐ray diffraction and imaging

The XTOP conference, held every other year at a different location in Europe, is one of the central scientific platforms for methods and instrumentation in synchrotron-based high resolution X-ray diffraction methods, phase contrast imaging and microtomography. XTOP 2006, the 8th Biennial Conference on High Resolution X-ray Diffraction and Imaging, was held in Baden-Baden (Germany), 19–22 September 2006. The conference brought together experts in the fields of X-ray diffractometry, diffraction imaging/topography, X-ray phase contrast imaging, radiography and microtomography. The event included a visit to the synchrotron ANKA at Forschungszentrum Karlsruhe. We have dedicated the XTOP 2006 conference to the memory of Gerhard Borrmann (1908–2006) and Gerhard Hildebrandt (1922–2005). Both have contributed outstanding theoretical and experimental results to our present understanding of dynamical diffraction and X-ray topography. Examples are the discoveries of the phenomena known today as the Borrmann effect and the Borrmann fan, the first observation of Pendellosung fringes in the Bragg case, and manifold studies of X-ray absorption and X-ray diffraction topography. The XTOP 2006 audience in Baden-Baden was pleased to hear Helmut Klapper and Andre Authier present a review of the scientific life and contributions of those two excellent scientists. More than 200 scientists from many European countries as well as Armenia, Australia, Brazil, China, India, Israel, Japan, Korea, the USA, South Africa, and other countries came to the Black Forest and contributed to a fascinating, open and friendly atmosphere with scientific exchange and genuine discussion about the latest experimental discoveries, theoretical results and instrumental developments. Following the tradition of previous conferences, XTOP 2006 was preceded by a series of tutorials with the theme “Putting high-resolution X-ray methods into context ”. The aim of these lectures was to give beginners an introduction to X-ray scattering and imaging methods, and to provide experienced scientists with an overview of the state of the art. Eight tutorial lectures highlighted the common aspects and trends in the quickly developing and mutually interacting fields of modern X-ray physics and its scientific applications. XTOP 2006 spanned a domain of 6 dimensions, analyzed by X-ray methods that image structures and correlation properties on the micro-, nano- and atomic scale in real as well as in reciprocal space. One focus was on the common issues of high resolution scattering methods such as grazing-incidence small angle scattering (GISAXS), X-ray reflectometry, high resolution diffraction and reciprocal space mapping. The increasing use of anomalous and coherent scattering in measurements of correlation properties of density distributions and crystalline properties, e.g. of interfaces, thin layers and nanostructures, was also reflected in the presentations. A second main subject area, X-ray imaging methods, ranged from diffraction imaging such as X-ray topography, microbeam imaging and full-field microdiffraction imaging to absorption, fluorescence and phase contrast imaging in two and three dimensions. The borders between imaging and scattering methods are becoming increasingly blurred. Profiting from outstanding beam properties, scattering and imaging techniques work together today to solve common questions of phase retrieval for 2D and 3D reconstruction of object structure properties. We also observed an increasing number of reports about in-situ measurements with sophisticated sample environments to characterize structure evolution under different thermal, mechanical or other loads, as well as enhanced structural information by advanced combinations of methods. The evening talk by paleontologist Paul Tafforeau led the participants into a prehistoric world made transparent by X-ray absorption and phase contrast tomography on fossils. All together, XTOP attendees exchanged their scientific views in and around 35 regular and 11 invited talks, 8 tutorials, 130 posters and countless discussions during the days and late nights of the conference. The town of Baden-Baden with its spa waters, gardens and promenades provided a wonderful and stimulating ambiance including visits to historical casinos, art exhibitions, concerts and the scenery of the Black Forest. The Karlsruhe Cornet Quartet brought melodies of the German Romantic era into the peristyle of the conference hotel. Another highlight for ears and eyes was the concert during the conference dinner, with fine Jazz and Bossa Nova music by the “Bethree” band from Berlin. As part of the conference programme, the Forschungszentrum Karlsruhe GmbH invited the participants to visit its research campus and especially the national synchrotron facility ANKA (Angstromquelle Karlsruhe), just one day before the centre's 50th anniversary celebration on 23 September 2006. Afterwards the BRUKER AXS company gave participants the possibility to tour the manufacturing halls of this provider of X-ray instruments resident in Karlsruhe. Following the tradition of the conference series started in 1992, XTOP 2006 continues to publish a collection of high-level original contributions and invited review papers rather than standard “conference proceedings”. This includes a refereeing process following the usual standards of peer-reviewed scientific journals. For the first time, we present the results of XTOP as a special issue of physica status solidi (a). We would like to thank once again all the members of the programme committee, the local committee and all other individuals who contributed to the success of this conference. Our special thanks go to the referees and to Tatjana Litvina for the efficient administration of the reviewing process. We are sure that all participants of XTOP 2006 and readers of this volume are looking forward to the next XTOP conference, organized by Johannes Kepler University in Linz (Austria) in 2008. (© 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)