Advanced Photon Source

An Office of Science National User Facility

APS Leadership

The Photon Sciences directorate consists of the X-ray Science, Accelerator Systems, and Advanced Photon Source Engineering Support divisions, which comprise the Advanced Photon Source (APS) and the APS Upgrade Project.

Stephen K. Streiffer, Associate Laboratory Director, Photon Sciences, and Director of the APS

Stephen Streiffer is the Associate Laboratory Director for Photon Sciences at Argonne. The Photon Sciences directorate consists of the X-ray Science, Accelerator Systems and Advanced Photon Source Engineering Support divisions, which comprise the Advanced Photon Source (APS), and the Argonne Accelerator Institute.

The APS is the brightest source of high-energy x-rays in the Western Hemisphere and is utilized to study the structures of materials and processes at the atomic scale. It is also the largest scientific user facility in the North America, with more than 5,700 users visiting each year.

Dr. Streiffer’s scientific expertise is in nanostructured complex oxides and in structural characterization of materials using x-ray scattering techniques.

Overarching themes in his research program include the development of novel concepts for integration of oxide heterostructures, establishing a fundamental understanding of polar interfaces, and exploring how these interfaces may be manipulated to influence electronic and chemical function. He has authored or co-authored more than 150 scientific publications and holds one patent.

Streiffer holds a Ph.D. degree in materials science and engineering from Stanford University and a B.S. degree in materials science and engineering from Rice University.

Robert O. Hettel, Project Director, Advanced Photon Source Upgrade

Robert Hettel is the Project Director of the Advanced Photon Source (APS) Upgrade Project at Argonne. Hettel will oversee the planning, construction, and implementation  of the upgrade.

He is a veteran accelerator designer and expert on storage-ring light sources. He came to Argonne in November 2017 from the SLAC National Accelerator Laboratory.

Hettel earned his B.S. in physics with departmental honors from Harvey Mudd College in Claremont, California. He has benefited from decades of training in accelerator science and technology from many distinguished mentors at SLAC  and elsewhere.

Dennis M. Mills, Deputy Associate Laboratory Director - X-ray Science

Dennis Mills is a Deputy Associate Laboratory Director for Photon Sciences at Argonne.  His main scientific interests are x-ray optics for synchrotron radiation applications and the use of the unique properties of synchrotron radiation, such as the polarization and modulated time structure, for studying condensed matter physics.

He received his Ph.D. at Cornell University in applied physics in 1979 and worked as a Staff Scientist at the Cornell High Energy Synchrotron Source from 1979 until 1988 when he joined the staff of the Advanced Photon Source at Argonne. 

Awards include a Guggenheim Fellowship (1987), University of Chicago Medal for Distinguished Performance at Argonne (1997), the Advanced Photon Source Arthur H. Compton Award (1998) for work related to x-ray optics, and the University of Chicago Pinnacle of Education Award (2008) for his contributions to the development of the National Neutron and X-ray Scattering School.  He is a Fellow of the American Physical Society and served at the Main Editor for the Journal of Synchrotron Radiation from 2000-2008.

George Srajer, Deputy Associate Laboratory Director - Operations

George Srajer is a Deputy Associate Laboratory Director for Photon Sciences at Argonne.

Dr. Srajer’s scientific expertise is in magnetic multilayers, single crystals, and nanostructured magnetic systems, and in the application of polarization-dependent x-ray scattering and spectroscopy techniques for studies of magnetic materials.

Overarching themes in his research program include studies of phase transitions and structural properties in condensed matter systems. His work contributed to the understanding of charge and charge-magnetic roughness correlations in magnetic multilayers and to the discovery of the Bardeen-Cooper-Schrieffer ground state breakdown at a quantum phase transition in an itinerant antiferromagnet. He has authored or co-authored more than 105 scientific publications, and one book chapter, and holds four patents.

Srajer holds a Ph.D. degree in physics from Brandeis University and a B.S. degree in physics from the University of Belgrade, Serbia. He is a Fellow of the American Physical Society.

John Byrd, Accelerator Systems Division Director

John Byrd

John Byrd is the Director of the Accelerator Systems Division at the Advanced Photon Source and Director of the Argonne Accelerator Institute. He supports the continuous improvement in performance, capability, and reliability of the Advanced Photon Source as well as guiding future directions for accelerator development at Argonne. John received his doctorate in accelerator physics from Cornell University in 1991. He is a Fellow of the American Physical Society. 

John P. Connolly, APS Engineering Support Division Director

John P. Connolly is the Division Director for Argonne’s Advanced Photon Source (APS) Engineering Support Division.

At Argonne since March 2016, Connolly leads a division that provides a broad range of engineering expertise for both APS operations and the APS Upgrade Project, to maintain the world-leading stature of the APS accelerator complex and beamlines, and to ensure that the APS Upgrade Project succeeds in transforming the APS into a next-generation light source.

Connolly received his M.B.A. in finance, international business from Duquesne University - John F. Donahue Graduate School of Business, and his B.S.E., mechanical engineering from the University of Pittsburgh - Swanson School of Engineering. He is also a graduate of the University of Chicago Strategic Laboratory Leadership Program as well as Executive Education Programs at the University of Virginia Darden Graduate School of Business and the Dartmouth College Tuck School of Business.

Connolly started his career at Westinghouse Electric Company, LLC, exclusively in the commercial nuclear industry and held positions of increasing responsibility over 16 years. He was a two-time recipient of the George Westinghouse Signature Award of Excellence and the recipient of a Nuclear Fuel Special Award.

Jonathan C. Lang, X-ray Science Division Director

Jonathan Lang is the Director of the X-ray Science Division.  He oversees a team that develops cutting-edge synchrotron x-ray instrumentation and techniques for addressing the research needs of the U.S. scientific community across a range of physical, materials, chemical, environmental, and life sciences.