The linac coherent light source: Concept development and design considerations

Abstract

The Linac Coherent Light Source (LCLS) is the world’s first hard X-ray freeelectron laser. First proposed in 1992, the LCLS concept immediately attracted the interest of accelerator physicists in the synchrotron light source community. Interest among x-ray researchers grew slowly until about 1996, when scientists at DESY produced a concept for a large x-ray laser research facility (now the European XFEL). The US Department of Energy (DOE) conducted formal assessments of the science potential of accelerator-based x-ray lasers between 1992 and 2001 when DOE officially acknowledged that such a device should be built. The DOE assessments and their conclusions demonstrate how a young researcher can have a preview, over seven years in advance, of important new science facilities and their capabilities. In 2002, SLAC National Accelerator Laboratory prepared a conceptual design of LCLS. By this time, the LCLS concept had grown from a minimum-cost test to a versatile facility supporting the research of thousands of x-ray experimenters. Groundbreaking for construction of LCLS began in 2006, and first lasing at 8 keV was observed in April 2009. This chapter describes some of the most significant physics and engineering problems and solutions: performance of the electron source, such as the potential deleterious effects of coherent synchrotron radiation instabilities, precision control of magnetic fields in the undulators.