Whether he is on the side of a mountain or working at the Fermilab Quantum Institute, Cristián Peña likes to explore the unknown and tackle new challenges. Although he spends most of his time working on quantum communication systems for FIQ, Peña dedicates time to work on the CMS experiment. His work between the two experiments, while different in practice, are conceptually similar. Photo: Cristián Peña
What do you work on at the U.S. Department of Energy’s Fermi National Accelerator Laboratory?
I am with the Fermilab Quantum Institute. I work on various aspects of high-energy physics and quantum information science. I work on what we call quantum communication systems; that’s using the properties of quantum entanglement to distribute information.
On the other side, I also work for the Compact Muon Solenoid experiment. In CMS, I work on precision-timing detectors, and I also look for new physics in what we call long-lived particles.
How did Fermilab become part of your career path?
I was an electrical engineer as an undergrad in Chile until I switched to physics at some point close to finishing my undergrad degree. Then I came to Fermilab as an undergrad from Chile to work on neutrino physics.
In the U.S., I applied to graduate school and got into Caltech. There, I did my Ph.D. in particle physics with the CMS experiment. I applied for a postdoc at many places and decided to join Fermilab as a Lederman Fellow.
As a Lederman Fellow, you have the freedom to choose what you do, which is great. I decided to work partly on the CMS, and in parallel, develop a new program to perform quantum communication experiments, which at the time was quantum teleportation. Now, the novel experiment that we are running at the Fermi Quantum Institute is called entanglement swapping.
How does your work overlap between the Fermi Quantum Institute and CMS?
I tend to think of ways to connect the dots. For example, ultra-precision timing is something that we’ve worked on extensively in CMS, and it also turns out that it underpins our quantum communications projects. Ultra-precision timing detectors are key to achieving our ambitions scientific goals, as well as electronics systems that can read out timing information with high accuracy. These are all aspects in which Fermilab is a leader in the field, which makes it very rewarding to be involved in such a vibrant community.
For example, recording the time of arrival of a long-lived particle in the CMS detector and the time of arrival of a photon in quantum teleportation or entanglement swapping experiments both need very precise time measurements. It’s not the same detector that we use, but it is the same concept. There’s a lot of information encoded in the time of arrival of a particle, and measuring it as accurately as possible enables us to conduct our experiments. By working at the frontier of time-precision detectors, I can transfer knowledge from one community to the other and run experiments seamlessly between the two.
How do outside collaborations play a role in your experience as a Fermilab scientist?
As a Fermilab scientist, I have the opportunity to interact with experts from different fields who come here to use our expertise. We have very fruitful and active collaborations that are really pushing the envelope.
People from all backgrounds come here. We have students, postdoctoral fellows and professors who set up their experiments at Fermilab. We have a very fluid collaboration with them so that’s something that I enjoy a lot.
It also feels like you’re not always grinding the same thing over and over again. There’s always something new, something unique, and there’s always a new challenge. It’s refreshing to have new students, to train new people, and to learn from them as well. So it’s very, very unique.
“As a Fermilab scientist, I have the opportunity to interact with experts from different fields who come here to use our expertise. We have very fruitful and active collaborations that are really pushing the envelope.”
Can you tell me about specific projects you are working on that require collaboration?
The Illinois Express Quantum Network is an experiment where we collaborate closely with Northwestern University, Argonne National Lab and Caltech. The project is to communicate or connect, through the use of optical fiber and single photons, various quantum nodes across the Chicagoland area with Argonne and Northwestern. For the Fermilab Quantum Network (FQNET), although it has the name “Fermilab” in it, we collaborate very closely with Caltech. This original collaboration was the seeding experiment for the more complex Illinois Express Quantum Network.
What do you like to do when you are not at work?
I grew up next to the Andes mountains. In physics, you explore new things as much as possible, and that’s what mountains give you. There’s this sense of exploration of new things and challenges. Now that I have kids, my free time is more family-focused, but mountains are always a part of our family trips.
The Fermilab Quantum Institute is supported by the DOE Office of Science.
Fermilab is the host laboratory in the United States that facilitates participation of hundreds of U.S. physicists from more than 50 institutions in the CMS experiment at CERN. Fermilab CMS plays a leading role in detector construction and operations, computing and software, and data analysis.
Fermi National Accelerator Laboratory is supported by the Office of Science of the U.S. Department of Energy. The Office of Science is the single largest supporter of basic research in the physical sciences in the United States and is working to address some of the most pressing challenges of our time. For more information, please visit science.energy.gov.
For several years, three U.S. Department of Energy national labs have worked together to further improve state-of-the-art particle accelerator technology. First tests of a prototype built at Fermi National Accelerator Laboratory show the effort has paid off, with a new component setting records.
The technology under development is called a superconducting radio-frequency cryomodule, a high-tech piece of equipment that efficiently speeds up particles. It is a key building block of modern particle accelerators and X-ray lasers. All supported by the DOE Office of Science, Fermilab, Thomas Jefferson National Facility and SLAC National Accelerator Laboratory have pooled their expertise for research and development on cryomodules that will enhance SLAC’s X-ray laser, known as the Linac Coherent Light Source.
Assembly of vCM cold mass prior to insertion into the cryomodule vacuum vessel. Photo: APS-TD process engineering group
LCLS produces very bright X-ray beams used to provide researchers insights into the atomic structures of cells, materials and biochemical pathways. An upgrade of LCLS to LCLS-II is currently underway. The cryomodules now in development will be part of a future high-energy update, called LCLS-II-HE, that will enable even more precise atomic X-ray mapping.
Researchers in biomedical and materials science fields can use LCLS-II and LCLS-II-HE, for example, to study how energy flows in tiny molecules and biochemical systems; how light penetrates and interacts with synthetic materials; and how materials might behave in extreme environments. Importantly, scientists also can use LCLS technology to study the properties of electric fields and how factors such as pressure and magnetism might govern particle interactions.
vCM in the cantilever fixture for insertion of the coldmass into the vacuum vessel. Photo: APS-TD process engineering group
To produce X-rays, LCLS-II accelerates electrons using superconducting radio-frequency technology. After reaching close to the speed of light, the electrons fly through a series of magnets, called an undulator, which forces them to travel a zigzag path and give off energy in the form of X-rays that are then used for research.
From prototype to production
The high-energy upgrade of LCLS-II is the solution to a seemingly impossible task. Researchers wanted to double the energy of the X-ray laser, but the upgrade has to be squeezed into a relatively small area between the existing accelerator and another experiment. Current state-of-the-art technology would have required too much room — so the teams had to invent a way to pack more particle punch into their equipment.
Accelerator experts improved the cryomodules in several ways. They used a process called “nitrogen doping” to optimize the molecular makeup of the walls of the superconducting accelerator cavities, the components that accelerate the particle beam. They also developed new procedures to assemble and finish the components. Improving the cleanliness reduces unwanted effects from any contamination on the surface, including errant dust particles.
“We are starting LCLS-II-HE with the proven success from LCLS-II experience. We will leverage from our successes and also from our unwanted outcomes and adapt the lessons learned to LCLS-II-HE.”
Fermilab’s prototype is a “verification cryomodule.” It’s proof that the design works as expected, the improved cryomodules will successfully fit in the constrained space, and that final production can begin. It’s a strong start to the upgrade that will take place over the next several years and will require 24 new cryomodules: 13 produced at Fermilab and 11 at Jefferson Lab. Researchers improved the cryomodules far beyond current specifications, and the new equipment should result in a 30 percent improvement to LCLS-II’s performance.
“Structurally, if you’re looking at the cryomodules from the outside, you won’t be able to tell the difference,” said John Hogan, senior team lead at Jefferson Lab. “But if we’re able to maintain that test performance throughout the whole production, it will give the machine much more energy.”
vCM cavity assembly in the semiconductor grade cleanroom at MP9. Photo: APS-TD process engineering group
Experts pay attention to quality factor, called Q0, which measures a cryomodule’s efficiency — basically, how much excess heat it generates. Superconducting cavities generate about 10,000 times less heat than normal conducting cavities made out of copper. But they have to be kept at cryogenic temperatures (usually around 2 Kelvin, or negative 456 degrees Fahrenheit), requiring a cryogenic plant. To keep the cryogenic requirements reasonable, many accelerators are operated in a “pulsed mode,” with pauses between pulses to reduce the cryogenic load. The nitrogen doping process increases the Q0 so much that it allows the cryomodules in LCLS-II to operate at full tilt without stopping, a feature called “continuous wave mode.”
The verification cryomodule achieved a record in this continuous mode; electrons passing through the module will have their energy increased by an incredible 200 million electronvolts. The rapid acceleration within a single cryomodule is what will enable the high-energy LCLS-II to reach higher energies in a shorter distance while using fewer cryomodules. The team was also able to maintain the high-quality factor, meaning faster acceleration with minimal excess heat.
Fermilab senior team lead Tug Arkan said the prime focus of the high-energy upgrade is quality and performance, building on the labs’ experience working together. “For LCLS-II, we designed; we procured parts; we assembled the parts into the cryomodules; we tested the cryomodules; and then we successfully delivered them to SLAC,” said Arkan. “We are starting LCLS-II-HE with the proven success from LCLS-II experience. We will leverage from our successes and also from our unwanted outcomes and adapt the lessons learned to LCLS-II-HE.”
Jefferson Lab and Fermilab are now assembling the needed cryomodules, which should be complete in 2024. The equipment will be shipped to SLAC and stored until scientists are ready to move them into their positions at the end of the LCLS-II accelerator chain.
The vCM at the Fermilab Cryomodule Test Facility. Photo: APS-TD process engineering group
Once the team at SLAC installs and commissions the LCLS-II-HE, researchers in everything from biomedical science and molecular physics to renewable energy will find the facility useful.
“LCLS-II-HE will enable higher X-ray energies and better tools and capabilities for the science community,” said Greg Hays, the LCLS-II-HE project director at SLAC. “Increased gradient with reduced heat loads will cut the number of required liquid helium refrigeration plants in half and reduced the length of the overall accelerator, allowing it more than double the energy of LCLS-II by making it only 50 percent longer.”
The advances in cryomodule fabrication, installation and operation will also be useful for future particle accelerators both big and small. Many particle accelerators use the same superconducting radio-frequency technology as LCLS-II to accelerate particles, so applying the engineering principles from the LCLS-II-HE upgrade will allow other research teams to create high-performing accelerator cryomodules that create little excess heat and can operate efficiently.
“Higher-gradient performance with lower heat generation will dramatically improve future particle accelerators,” Hays said. “It translates to lower construction and operation costs.”
Fermi National Accelerator Laboratory is supported by the Office of Science of the U.S. Department of Energy. The Office of Science is the single largest supporter of basic research in the physical sciences in the United States and is working to address some of the most pressing challenges of our time. For more information, please visit science.energy.gov.