Upgraded Advanced Photon Source Delivers First Light

The Advanced Photon Source (APS) has completed its upgrade and delivered its first X-ray light beams to a scientific beamline. Operations had been suspended over the past year while its original electron storage ring, responsible for producing X-ray beams, was removed to make way for the new one.

This new storage ring is made up of 1321 powerful electromagnets, thousands of power supply units, and a thin, but lengthy vacuum system that connects it all. It runs on 32 miles of power cable, eight miles of diagnostic cable, and 20 miles of optical fiber.

The storage ring pioneers the use of multi-bunch swap-out injection, a method of periodically replenishing electrons in the beam as it circulates. Previously, the APS utilized a technique developed in the 1990s, called top-up injection, which provides nearly constant stored beam current to X-ray experiments by “topping up” electron bunches that have lost electrons.

Mohan Ramanathan, associate project manager of the APS Upgrade, opens the shutter at the 27-ID beamline, letting in light for the first time since the facility paused operations in April 2023. Courtesy of Jason Creps/Argonne National Laboratory.

Because of the very strong nonlinear focusing fields in the newly upgraded APS, top-up injection is no longer possible. Instead, bunches of electrons will be injected directly onto the nominal stored-beam trajectory, completely replacing the stored bunches. This swap-out method uses fast kicker magnets to extract and dump the stored bunch while bringing the beam from injectors and placing it in the stored bunch’s place, all in a span of a few nanoseconds. The process will repeat every few dozens of seconds to keep the beam current constant.

According to Argonne National Laboratory, the APS is the first modern synchrotron X-ray light source in the world to make use of the technique. Argonne’s accelerator team rolled out the method in April of this year.

“The upgraded APS storage ring is performing exactly as we had hoped it would,” said Jim Kerby, director of the APS Upgrade Project.

After more than a month of commissioning the new storage ring, the APS team has begun the process of bringing each of the 71 beamlines into operation. The first scientific beamline to receive X-rays was 27-ID, home of the resonant inelastic X-ray scattering program at the APS. Researchers will be able to use the line to study complex materials that could be used to power future technologies.

Over the next year, all of the APS beamlines will return to operations, allowing researchers to resume work.

“I’m excited to see what the international science community will do with the increased capabilities of the upgraded APS,” said Paul Kearns, Argonne laboratory director. With more powerful X-ray beams, enhanced beamlines, and assistance from Argonne’s Aurora supercomputer, Kearns expects the upgrade to facilitate discoveries at a greatly accelerated pace.