The evolution of synchrotron radiation and the growth of its importance in crystallography
The author's 2011 British Crystallographic Association Lonsdale Lecture included a tribute to Kathleen Lonsdale followed by detailed perspectives relevant to the title, with reference to the Synchrotron Radiation Source (SRS) and European Synchrotron Radiation Facility (ESRF). Detector initiatives have also been very important as have sample freezing cryomethods. The use of on-resonance anomalous scattering, smaller crystals, ultra-high resolution as well as the ability to handle large unit cells and the start of time-resolved structural studies have allowed a major expansion of capabilities. The reintroduction of the Laue method became a significant node point for separate development, and has also found wide application with neutron sources in biological and chemical crystallography. The UK's SRS has now been superseded by Diamond, a new synchrotron radiation source with outstanding capabilities. In Hamburg we now have access to the new ultra-low emittance PETRA III, the ultimate storage ring in effect. The ESRF Upgrade is also recently funded and takes us to sub-micrometre and even nanometre-sized X-ray beams. The very new fourth generation of the X-ray laser gives unprecedented brilliance for working with nanocrystals, and perhaps even smaller samples, such as the single molecule, with coherent X-rays, and at femtosecond time resolution.