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From the Director of the Photon Science Directorate: Photon Science at SLAC–What, Why and Where to?

(Photo - Keith Hodgsonl)SLAC's outstanding reputation is built upon seminal scientific discovery, much of it enabled and facilitated by advanced accelerator-based tools for which SLAC has so often pioneered new ground. This is true in Particle Physics and Astrophysics. It is also true in the area we call photon science at SLAC—that is, the use of X-rays to study and understand the structure and behavior of matter down to the atomic scales of space and time, with relevance to fundamental scientific challenges, and important societal problems related to energy, the environment and human health.

The roots of photon science at SLAC can be traced back to the founding of the Stanford Synchrotron Radiation Project in 1973, where a group of Stanford University faculty partnered with SLAC faculty and senior staff to conceive and create one of the first X-ray synchrotron user facilities in the world, parasitic on the SPEAR storage ring. Looking back, a key reason for success came from the intellectual leadership provided by faculty and scientific staff who developed new instrumentation, developed innovative new methodologies and analysis techniques, trained young scientists and rapidly engaged the outside academic and industrial user communities in what became a worldwide model for how to operate a synchrotron user facility. That beginning led to what we know of today as the Stanford Synchrotron Radiation Laboratory (SSRL) and from it came the Sub-Picosecond Pulse Source (SPPS) and the beginning of the Linac Coherent Light Source (LCLS). SSRL, with its integrated portfolio of photon science research, strongly helped catalyze the remarkable growth in synchrotron science worldwide that has now come to serve tens of thousands of users worldwide at dozens of synchrotron facilities.

The Photon Science Directorate at SLAC has been organized to meet the scientific challenges of tomorrow. We are increasingly focused on understanding larger and very complex interacting systems, such as high-temperature superconductors, complex catalysts or the molecular machines that drive living cells. Discovery and breakthrough science in such challenging areas requires a multi-disciplinary approach, utilizing multiple experimental techniques, sophisticated sample preparation and modifications, and simulations and theory. We need organizational structures that cut across the traditional boundaries, enabling and facilitating this paradigm in the scientific areas where we have chosen to focus and excel. SLAC has outstanding expertise and tools and Stanford has world-class research faculty and staff in many of the relevant areas. Through our new Centers of Excellence we can take maximum advantage of the synergy between SLAC and Stanford University departments to provide world-leading programs that both deliver outstanding science and couple strongly to our accelerator-based facilities at SLAC—SSRL and LCLS—to enable science and help keep them at the very forefront.

This Centers of Excellence strategy has been implemented for two areas—advanced materials sciences (XLAM) and ultrafast x-ray science (PULSE). We are making plans for a third center focused on biocomplexity. A central element of all the centers is their close coupling to Stanford. There is a “dual report” to SLAC Photon Science and the Stanford Vice Provost and Dean of Research, Ann Arvin. The research portfolio of the centers is led by faculty and senior scientific staff. Many of the faculty hold joint appointments between the SLAC Photon Science Department and relevant main campus departments in the Schools of Humanities and Sciences, Engineering, Earth Sciences or Medicine. This model (also used by Kavli) offers a flexible and adaptable structure to respond to changing scientific priorities. We are able to attract and retain the very best faculty and scientific and technical staff, leveraging on the strong synergy between SLAC and Stanford. The research agenda of the centers helps lead the development of the instruments and methods on SLAC’s operating facilities. The structure allows us to seed new initiatives, bring in additional resources and catalyze new scientific directions.

Let me briefly comment on the two current Centers of Excellence in SLAC’s Photon Science Directorate and plans being made for a third initiative.

The first of the Centers of Excellence in photon science to be created was the X-ray Laboratory for Advanced Materials (XLAM). XLAM is directed by Professor Z.-X. Shen who has a joint appointment between Photon Science at SLAC and Applied Physics and Physics on the main campus. XLAM’s research portfolio seeks to answer questions like how the properties of materials emerge from their atomic and electronic constituents, how energy conversion and transport processes work and how interfaces function. Some specific focus areas include superconductivity, magnetism/spintronics, novel material systems that are important to organic semiconductors, battery and energy storage technology, organic solar cells and solid-state lighting.

In recognition of the broadening research agenda, the increasing relevance to energy-related processes and the interplay between energy and the environment, the name of XLAM is being changed to the Stanford Institute for Materials and Energy Sciences (SIMES). The broadened SIMES research portfolio will continue to utilize and help develop the resources at SSRL and become engaged in LCLS science, while also coupling to Stanford initiatives in energy and environmental policy and technology. SIMES will engage strongly in the DOE mission agenda related to grand scientific challenges, and to the energy challenge, including development of a proposal for the DOE’s new program that will create a series of "Frontier Energy Research Centers."

The more recent addition to the photon science portfolio is the Photon Ultrafast Laser Science and Engineering Center (PULSE), directed by Professor Phil Bucksbaum (who holds a joint appointment between Photon Science at SLAC and Applied Physics and Physics on the main campus). A central mission of PULSE is to carry out world-leading research in the emerging area of ultrafast science—enabling innovative opportunities at LCLS, the first light source capable of simultaneously probing the natural length scale, time scale, and field strength scale of the atomic constituents of all matter. Such ultrafast, atomic-scale research will unravel mysteries that control complex phenomena, from photosynthesis to catalysis to superconductivity. Extremely high spatial and temporal resolution can separate and simplify fundamental dynamics in correlated materials, track the course of atoms undergoing phase transitions and view bond motion within biomolecules. The relevance to our modern society is immense—nature converts sunlight to energy using sub-picosecond mechanisms, the ultimate speed of information transfer and limits of computer data storage are determined by ultrafast processes in materials, and chemical changes that are critical for catalysis are rooted in ultrafast processes. PULSE creates important new opportunities for Stanford and SLAC to pioneer and drive the emerging field of ultrafast X-ray science and LCLS, much in the way that they did for conventional synchrotron sources three decades ago.

We are actively engaged in planning for a third Center focused on structure and function of complex biological systems—utilizing a multidisciplinary strategy engaging experimental methodology, bioinformatics and simulations/theory. The new Center, which we hope to launch later this year, will seek to understand the structure of macromolecules and their complexes, and how the interactions between macromolecules in these larger assemblies confer and control function (i.e., the workings of “molecular machines”). Ultimately, how these assemblies are organized and networked at the cellular and tissue level is the overarching goal. Establishing the fundamental physical bases of selected life processes would contribute to transforming medicine, renewable energy research, environmental remediation and other fields that are informed by or harness biological systems. As this concept evolves, we again envision solid connections with the main campus, especially through the Bio-X program. There will also be strong overlap with research programs in SIMES and PULSE and coupling to both the SSRL and LCLS programs.

I deeply believe that with a visionary photon science program as outlined above, SLAC can be the world’s leader in its areas of chosen foci. This can only be accomplished in close partnership with our two premier photon-providing programs SSRL and LCLS, together with Stanford, and with continuing support from DOE Office of Science and other federal sponsors including NIH and NSF. Achieving and sustaining simultaneous excellence across the three SLAC elements—Photon Science, SSRL through SPEAR3 and its evolution to a next generation light source on PEP, and the LCLS and its evolution with new capabilities that take advantage of the full linac, provides SLAC and Stanford with a truly unique, internationally competitive opportunity for scientific discovery. We will contribute to solving tomorrow’s challenging societal problems in energy, the environment and health and will attract and train the next generation of scientific leaders.

Keith Hodgson, SLAC Today, April 4, 2008   

Keith Hodgson is SLAC’s Director of Photon Sciences