Much ado about vacuum

Much ado about vacuum
by Denise Yazak for BNL News
Upton NY (SPX) Nov 16, 2024

When a cutting-edge facility like the National Synchrotron Light Source II (NSLS-II), a U.S. Department of Energy (DOE) Office of Science user facility at DOE's Brookhaven National Laboratory, is running, its operations can seem almost effortless. It's easy to overlook the vast number of people and processes that come together to produce NSLS-II's ultra-bright X-ray light that scientists from around the world rely on for their research. There are entire groups of technicians and engineers dedicated to the unique and complex systems, utilities, and instruments that work in harmony to help produce world-leading science.

Robert Todd leads one of these indispensable teams, the NSLS-II Vacuum Group. While the word "vacuum" may conjure up images of Hoovers and air-tight packages, the high-tech vacuum system this team builds and maintains serves a unique purpose. In physics, a "vacuum" is a space devoid of matter. And without a vacuum system, researchers at NSLS-II would lose the electron beams and X-ray photons they rely on to perform their experiments. Today, Todd explains why that is and how he got involved in such a specialized field.

Why is a vacuum system so important to a light source facility?

Vacuum can easily be taken for granted until you don't have it. It can greatly affect the quality of the beam. The air we breathe is actually full of different gases - primarily oxygen and nitrogen, with a little bit of argon - and electrons and photons generated in NSLS-II's accelerator would be lost to those gases if we couldn't remove them. Either the electrons would interact with the gases and be removed from circulation or photons would be scattered and attenuated. To prevent this and enable electrons and photons to move freely, all gas must be evacuated from the electron storage ring and X-ray beamlines using ultra-high vacuum. The operating pressure must be below one trillionth of atmospheric pressure. In other words, we need an incredibly low pressure that's about a trillion times less than the air pressure around us. But that still leaves over 35 million gas molecules per cubic centimeter. Achieving this vacuum level is not easy and requires special equipment and designs.

How does the vacuum system at NSLS-II differ from the kinds of vacuums people are more familiar with?

A household vacuum cleaner reduces atmospheric pressure - the air pressure we're used to here on Earth, which is about 760 torr at sea level - to about 600 torr. We reduce the pressure down to an ultra-high vacuum, about one hundred-billionth of a torr. Those values are closer to levels you'd find in outer space. Because of this, there is a whole field of vacuum science that focuses on different kinds of pumps that operate in specific pressure regimes compared to others. We use a whole host of different pumps to get from atmospheric pressure to ultra-high vacuum. At this level, 90% to 99% of the gas is removed from the vacuum chamber, and then the remaining gas is managed by a capture pump. The capture pump doesn't remove the gas from the system directly; instead, it traps and retains it. There are a lot of different pumps that we use along with specialized equipment to check for atmospheric leaks, either through cracks or material defects, and to measure the constituents of the gas and see what the composition is under vacuum. Ultra-high vacuum cleaning of chambers and components is also extremely important to the overall operation and vacuum level, so we have specialized cleaning facilities as well.

In a large, complex light source facility, what are some of the biggest challenges that you and your group face?

When I took over as group leader, I actually found that there weren't many significant operational challenges. I attribute this to the sound design of the original vacuum systems and the excellent team of 11 engineers and technicians who have helped build and maintain them. This allows us to focus on design work for the new beamlines being planned and constructed and to start thinking about a future accelerator upgrade. We've also collaborated on projects with other light sources at other national laboratories, like the Advanced Photon Source at DOE's Argonne National Laboratory and the Advanced Light Source at DOE's Lawrence Berkeley National Laboratory. Here at Brookhaven, we've started assisting the team working on the Electron-Ion Collider (EIC) project as well. Being involved in all of these different facilities and projects is definitely an exciting part of the job; it's juggling several at once that can sometimes pose a challenge.

This is such a unique and interesting field. How did you get involved in vacuum science?

I came to Brookhaven Lab in 1987 as a technician in the Superconducting Magnet Division immediately after graduating from SUNY Binghamton with a bachelor's degree in mechanical engineering. This was after earning an associate's degree in internal combustion engines from SUNY Alfred, where I studied different types of engines and thermodynamic cycles. When I saw some of the different types of vacuum pumps here at the Lab, like rotary piston pumps and turbomolecular pumps, I immediately recognized their similarity to engines, which sparked my interest in this field. Vacuum is used in a whole host of industries, not just particle accelerators. It's essential in the manufacturing of decorative hard glass coatings, semiconductors, and even potato chip bags. I pursued this interest in vacuum during the Relativistic Heavy Ion Collider (RHIC) project in the early '90s. I was one of the original members of their vacuum group and helped in both the design and construction of those systems. In 2013, I came over to NSLS-II to help as they were finishing construction of their first few beamlines. When the team's group leader, Charles Hetzel, moved over to the EIC in 2020, I took on the role of NSLS-II vacuum systems group leader.

You've had a long, interesting career here at the Lab. What would you say to someone who is just starting their career here?

I came to visit Brookhaven on a field trip in high school, and I thought it was really cool. I had no idea I would be working here 10 years later. I started as a technician and worked my way up. I wound up getting my master's degree in environmental science along the way. I've learned that there's a lot of different avenues you can take, and you can find places to grow within the Lab community. Don't be afraid to explore the things that interest you and pursue those projects. Brookhaven Lab is a phenomenal place to work. I don't think it's a place that you have to leave to advance; this can be your home forever if you want it to be. As much as I enjoy what I do, though, it's the community that continues to make me feel at home here. The particle accelerator is neat, but the people are the real draw. I have had some great mentors along the way, including Kimo Welch and Dick Hseuh. Charles Hetzel, our former group leader, taught me a lot about the unique field of synchrotron vacuum. The Lab has tremendous people who can encourage and help you as your career develops.

What are your interests outside of the work you do at NSLS-II?

I have always had an interest in cars. I like getting an understanding of how things work, whether it's a car, motorcycle, or particle accelerator. I also enjoy pursuing more athletic hobbies like running, biking, swimming, and even competing in triathlons. I enjoy spending time with my family as well. My daughter actually did an internship here at NSLS-II when she was in high school, which was pretty awesome. She graduated from Stony Brook University with a degree in economics and is now working in her field. My son is going back for his MBA after graduating from the University of Scranton, so we've had a lot of nice milestones to celebrate.

Are there any interesting projects coming up at NSLS-II?

At some point, we hope to upgrade our accelerator. When we built NSLS-II, it was one of the last third-generation light sources. It was cutting edge then, and it's still an amazing facility now. Moving towards a fourth-generation machine, or beyond, with world-leading emittance is exciting, and we're already exploring the technology to build and support that kind of accelerator.