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

Beginning to see the light: Vadim Sajaev leads the effort to get the upgraded Advanced Photon Source up and running

Sajaev and his team are in the midst of commissioning the new electron storage ring at the heart of the Advanced Photon Source


The new ring will generate X-rays that are up to 500 times brighter than the original APS could deliver.

A smiling man in a grey sweater

Like many working at the U.S. Department of Energy’s (DOE) Advanced Photon Source (APS), Vadim Sajaev is very busy.

You wouldn’t know it to talk to him. His demeanor is perpetually calm and even, and if he feels the pressure of his job at the DOE’s Argonne National Laboratory, he never lets on. These are exactly the qualities you want in someone with a central, key role in a gargantuan project, such as commissioning of the new electron storage ring of the APS.

The APS, a DOE Office of Science user facility at Argonne, is in the process of coming back online after a year-long shutdown, which saw the original electron storage ring at its heart removed and replaced with a brand new one. Commissioning of the new storage ring is well underway, a lengthy process that will demonstrate the reach of its enhanced capabilities.

“We feel like we’re on House M.D., diagnosing illnesses and finding cures. Only our patient is a billion-dollar accelerator.” — Vadim Sajaev, Argonne National Laboratory

The man leading this effort is Sajaev, and if that weren’t enough, he also recently assumed the role of interim director of the Accelerator Systems division (ASD) at the APS. That’s the division responsible not only for the new storage ring, but for all of the smaller accelerator systems leading up to it as part of the APS. Together, their job is to accelerate an electron beam up to about the speed of light and generate ultrabright X-ray beams used for the scientific research at the APS.

The new storage ring will create X-ray beams that are up to 500 times brighter than those of the original APS and deliver a vast improvement in a beam quality called coherence, which increases the amount of information scientists can get from their samples. The commissioning process essentially puts the new machine through its paces, slowly bringing it up to full operating power and delivering X-ray beams to the scientific research stations, called beamlines, that encircle the APS facility.

Sajaev calls it ​“getting to know the machine,” and even in these early stages, he’s excited about it. The original APS, he said, ran for more than 25 years, and by the end of its life cycle the operations team had figured out how to solve every problem that arose. For the new storage ring, the ASD team has run thousands of computer simulations, trying to study every possible effect that could deteriorate machine performance.

“We’ve spent so much time simulating it that I almost feel like I’ve worked on it for some time already,” Sajaev said.

But nothing can replace the experience of actually operating the upgraded APS. This is the first new accelerator Sajaev has had the opportunity to commission. He’s been at Argonne for 25 years, most of that time working on the APS after emigrating with his family from Russia in the late 1990s. He received his Ph.D. from Budker Institute of Nuclear Physics in Novosibirsk in 1997.

“It was soon after the collapse of the Soviet Union, and life became challenging,” Sajaev said. ​“Finding a job abroad was a goal for many scientists. I majored in accelerator physics because it promised a fast way out of Russia.”

Following a successful phone interview, Sajaev received an offer to move more than 5,000 miles away from home. ​“We were young,” he said. ​“The prospect of leaving behind everything familiar was daunting. But the promise of a better life and opening professional opportunities were very exciting. This was our goal, so we embraced it.”

His first job at the APS was on the linear accelerator, but an astute group leader deduced that Sajaev’s expertise would be better applied at circular machines such as the APS storage ring. Over the next two decades he moved up the ranks in ASD, becoming an associate division director before taking the interim division director job in April 2024.

Successfully commissioning the upgraded APS will take all of Sajaev’s experience and knowledge. The new storage ring is designed to reduce the electron emittance, keeping the beam as small and tight as possible as it goes around the ring. This means that any obstruction in the vacuum chamber that the beam moves through could affect the quality of the beam, no matter how tiny that obstruction is. ​“If an obstruction is not in the direct beam path but sits on the side and spoils the beam a little, it’s hard to find,” he noted.

As part of the process, Sajaev and his team will demonstrate a technique called swap-out injection, which involves using kicker magnets to replace electrons in the storage ring one tiny bunch at a time. The APS will be the first storage-ring light source to use this technique to replenish the electron beam.

While the physics of the commissioning process are his bread and butter, much of Sajaev’s job is logistical. It’s here that he’s grateful to have several people on the team who were involved with the commissioning of the original APS. He said he tries to learn from the first commissioning process, looking at how the teams exchanged information and how they rotated.

“I’m very grateful to have people who have gone through this on the team,” he said. ​“The current team here is great on a personal and professional level. There’s a lot of experience spread out among the team members, everyone is dedicated and everyone is here anytime they are needed. Support from the APS technical groups is also amazing. If an equipment problem arises in the middle of the night, quick help is just a phone call away. Everybody understands that building and commissioning an accelerator as advanced as ours takes a team effort and a full dedication to the job.”

Sajaev has set a schedule for commissioning, expecting the machine to be running consistently by June. While nothing is ever certain when finding and solving problems on something as complex as the new APS storage ring, Sajaev is confident. And very, very busy.

Unlike many of his colleagues, Sajaev doesn’t think very much about the scientific advancements that will come from the upgraded APS. For him, it’s all about the accelerator itself.

“I’m happy about the useful science that the machine will produce, but what I want is to build advanced accelerators,” he laughed. ​“I like it that our machine serves the most advanced user beamlines in the world, because that requires us to stay at the cutting edge of accelerator science.”

“Tackling problems brings immense satisfaction to accelerator physicists,” he said. ​“We feel like we’re on House M.D., diagnosing illnesses and finding cures. Only our patient is a billion-dollar accelerator.”

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