The Advanced Photon Source
a U.S. Department of Energy Office of Science User Facility

Introduction to APS

What is the APS?


The Advanced Photon Source is a synchrotron light source that produces high-energy, high-brightness x-ray beams. The source is optimized to put large quantities of high-energy photons into a very small area in a very short time.

The x-ray beam is customized at each beamline to meet particular needs. With more than 60 beamlines already operational, and more under development, the APS offers an exceptionally broad range of experimental conditions at a single facility. It is also conveniently located at Argonne National Laboratory, 30 miles southwest of Chicago, Illinois, with two nearby airports offering many travel options.

Scientists from around the world come to the APS to conduct forefront basic and applied research in the fields of materials science; biological science; physics; chemistry; environmental, geophysical, and planetary science; and innovative x-ray instrumentation.

The APS is one of several leading user facilities located at Argonne. These facilities, which include capabilities in nanoscience, electron microscopy, and high-performance computing, are also available to support your research, and many of the access procedures are shared with APS.

What experimental conditions and techniques are available?


Each beamline at the APS offers a unique combination of capabilities, but some of the main considerations are energy range and tunability, special sample environments, time structures, and beam size. Specifics for each beamline and a directory of techniques can be found in the Beamlines section; however, the techniques and capabilities evolve continually. The following are some highlights.
  • The energies used range from relatively "soft" x-rays (3-5 keV) to "hard" x-rays at 100 keV and sometimes higher. At many beamlines, the energy can be tuned with relative ease.
  • Samples can be examined under extreme conditions of temperature and pressure, and several facilities are available for samples requiring special handling (e.g., biohazards, radioactive samples).
  • Many experiments involve timing, through correlation with a pulsed laser or with the time structure of the x-ray pulses, for example. In the typical operating mode, the x-rays come in evenly spaced bunches or pulses, with 0.31 mA per pulse and 11.37 nanoseconds between pulses.
  • Some beamlines employ additional optics to narrow the already tight beam into even smaller spots, offering spatial resolution into the 50-nm range.
How is beam time made available?


The machine operates for 3 three-month runs (or cycles) each year, with a one-month shutdown between runs. The runs typically span February to April, June to August, and October to December.

Many beamlines are managed directly by the APS. Others are managed by Collaborative Access Teams (CATs), which are made up of scientists from universities, industry, and research laboratories. All beamlines offer time to the international scientific community.

In general, the APS makes beam time available in three ways. Specific requirements govern each mode of access.

  • General Users: The General User mode is the primary means of access for external users. There are two categories of General User access: macromolecular crystallography (MX) and all other science. The proposal form and the review and allocation process are tailored to meet the different needs of these communities.
  • Partner Users: The Partner User mode provides access for projects that (1) require guaranteed beam time over multiple cycles and (2) will ultimately benefit the General User community, for example, by providing new instrumentation or capabilities that will be available to all users or by creating or expanding a user community. Any beamline operated by the APS is open to Partner User proposals.
  • Collaborative Access Teams (CATs) are one type of large-scope partnership. A user whose home institution is a member of a CAT may be eligible to request beam time through the CAT. To see which sectors are operated by CATs, see the Beamlines Directory.
What are the requirements?

Publication. For General User research that will be published in the open literature, there is no charge for beam time. Users are expected to notify the APS of publications resulting from work conducted here. For proprietary work that will not be published, an hourly fee is charged to recover facility costs.

Compliance with regulations. Because Argonne National Laboratory is a controlled-access site operated by the U.S. Department of Energy (DOE), APS users must follow DOE requirements regarding permission to enter the site, training, safety practices for experiments, shipping of samples and equipment, etc. APS and beamline staff work very closely with users to help them fulfill these requirements.

How do I get started?
  1. Decide where you want to work. Read about APS science and communicate with beamline staff to decide which beamlines are suitable for your purposes.
    • See the Beamlines section, where you will find a techniques directory and a beamline directory. Consult the techniques directory to see which beamlines support the techniques you need (additional techniques may be available to CAT members). The beamline directory will point you to detailed specifications and contact information.
    • Find recent work done at the beamlines that interest you by searching by beamline in our publications database.
  2. See the new user checklist. This guide gives step-by-step instructions for users.

If you have any questions about working at the APS or finding the right beamline, please contact the User Office at 630-252-9090 or


To comment on the contents, please contact or 630-252-9090.