Session V2: Facilities for Meeting Grand Challenges

A Green Field Fourth Generation Light Source

The success of energy recovering linac technology has opened up new opportunities for the development of light sources to satisfy grand challenges in fundamental physics and materials research. A number of laboratories around the world have proposed extensions or upgrades to existing 2$^{nd}$ or 3$^{rd}$ generation light source facilities to take advantage of the higher brightness and short pulse lengths that 4$^{th}$ generation facilities could offer. Ideas range from multiple synchronized coherent sources in the THz to UV range to Compton X-ray sources, synchrotron emission, and on to achievement of multi-particle coherence in amplifiers or even oscillators at short wavelengths. Such proposals are exciting and begin to show the range of performance that such systems can provide. In this talk I will examine the possibilities for light source development unconstrained by existing physical layouts i.e., on a ``green field'' site. I will then address a set of photonic goals to be achieved and the technological path of development desirable to achieve the full benefits of this next generation of user facilities. In particular, there are specific technical achievements and engineering developments with great leverage on the cost and performance of future machines. I will point toward a development path to set the stage for optimization of technical performance and cost/benefit of this system.   

Science Driven the Parameters of 4th Generation Light Sources

The scientific challenges that can be best addressed with x-rays and the evolution of accelerator based x-ray sources has focused the attention of the x-ray community on new concepts: using the electron beam once rather than storage rings. We will describe this approach and the photon source properties that result with emphasis on peak and average brightness for the study of structure and dynamics in the chemical, materials and biological sciences. Examples from 4th generation sources planned and under construction will be presented.   

The Science Motivating the UK's Fourth Generation Light Source Project

The UK is committed to developing a proposal for a long wavelength (THz - soft X-ray) 4$^{th}$ generation light source that will provide short-pulse synchronised beams to be used in combination. Some of the science motivating the development of this facility is described. The facility will probe ultra-fast dynamics in a wide range of fields. `Pump-probe' experiments will allow the study of chemical reactions and short-lived intermediates on the timescale of bond formation, even for very dilute species. Circularly polarised light sources in a variety of frequency regimes will be used for example to manipulate and monitor carrier charge and spin transport in device structures. The high intensity of the free electron laser (FEL) radiation will allow high resolution in imaging and the opportunity to probe nonlinear regimes and new states of matter. Lower intensity, high repetition rate spontaneous radiation will provide ideal sources for ultra-high energy resolution spectroscopy, especially in the solid state. Around {\pounds}22 M funding has been obtained for the first stages of the project (construction of a prototype energy recovery linac (ERL) source, science demonstrations and design study work, currently underway at STFC Daresbury Laboratory).   

The proposed BigLight fourth-generation light source at the National High Magnetic Field Laboratory

``BigLight'' is a compact fourth-generation light source planned for the National High Magnetic Field Laboratory's (NHMFL) quasistatic-field facility at Tallahassee. Designed by George Neil and his team at the Jefferson Laboratory, it is based on an RF superconducting accelerator system driving three free-electron lasers (FELs) that cover the wavelength range from 1 mm to 1.5 microns, plus a broadband THz source. BigLight's specification was derived in a series of five workshops covering potential applications in condensed matter physics, nanoscience, biophysics, chemistry, material processing, microscopy, astrophysics and other disciplines; participants included scientists from current FEL laboratories, potential users and international experts on light sources and high magnetic fields. Consequently, in addition to the robustness and user-friendliness demanded of a user facility, the source has several unique features, including the possibility of running the near- and mid-infrared FELs and the broadband THz source simultaneously; this will allow a wide variety of multi-color, time-resolved, pump-probe and pump-probe-probe experiments with an extremely small timing jitter between pulses. BigLight will also be able to produce either a continuous stream of micropulses ($\sim$1 ps time resolution) or flexible macropulse configurations. Co-location with the world’s highest quasistatic fields presents some unique experimental possibilities; potential users have proposed novel ultra-high-field time-resolved EPR measurements, dynamic nuclear polarization, nonlinear cyclotron resonance, interband magneto-optics, FTICR and many other techniques with very general applicability. In the talk, I will outline the scientific desiderata that have shaped the design of BigLight, and describe some of the proposed experiments.