Cristian Boffo, project director for Fermilab’s PIP-II project, discusses the progress made so far in Fermilab’s major upgrade to Accelerator Complex, and what this means for future discoveries.
Set for decades of new discovery, Proton Improvement Plan II (PIP-II) is an essential upgrade to the Fermi National Accelerator Laboratory (Fermilab) Accelerator Complex in Illinois, USA. The PIP-II is a journey from Illinois to a distant detector in the deep underground neutrino experiment (sand dunes) in South Dakota, taking a distance of 1,300 km (800 miles) into the world’s most intense high-energy neutrino beam. Additionally, the upgrade to the existing accelerator complex allows for a wide range of physics research programs, opening up a vast range of experimental possibilities that were previously unreachable.
Since construction began in 2022, the project has already secured many important results. We are currently ready to begin assembly of our pre-production SSR2 (single spoke resonator 2) cryomodule at Fermilab. At the same time, British and French collaborators will assemble two types of frozen polarization: the HB650 and the LB650. The new linear accelerator consists of a total of 23 freeze modules that use five different cry modules and power the beam.
More details on the project, past results and next steps were discussed by editor Georgie Purcell to PIP-II Project Director Cristian Boffo.
Please tell me more about the background of PIP-II.
The PIP-II is a substantial upgrade to Fermilab’s acceleration facility. People usually call the PIP-II a new linear accelerator (LINAC) that replaces the existing ones built in the 1960s. In fact, part of the project is more than that, as it is also an upgrade to an existing accelerator complex consisting of boosters, main injectors and recycling. New linear accelerators employing new technology have been built to superconduct the radio frequency (SRF) cavity, and have also upgraded the complete system.
The main goal of the PIP-II is to have a better injection system that can produce proton beams of more than 1 megawatt. A key component of deep underground neutrino experiments, PIP-II powers a beam that allows neutrino fire from Fermilab, Illinois to the Long Baseline Neutrino Facility (LBNF) currently being constructed at the Sanford Metro Research Facility in South Dakota. Dune is the largest project in the U.S. Energy Sciences Agency’s High Energy Physics program, and aims to unlock neutrino mystery.
In summary, Fermilab needs PIP-II to enable the neutrino physics we are aiming for. Additionally, upgrading the accelerator system allows for future experiments that are currently impossible.
What are the main achievements of the project so far?
PIP-II received full funding for the project in 2022 and has been in the construction phase of the system ever since. The PIP-II actually started many years ago and had an early concept known as the “proton driver” that was conceived in 2005. This was a much larger project, and evolved under several different names until “PIP-II” was chosen.
PIP-II is funded by an investment of approximately $1 billion from the US Department of Energy (DOE) with an additional $300 million contribution from international partners. This is the first US-led particle physics project to make substantial international contributions from countries including Italy, France, the UK, India and Poland. Not only financially, the project also benefits greatly from the shared knowledge of international partners, particularly in key areas such as SRF. If there is a problem, our overseas partners are positioned very well to assist us. International collaboration is extremely important to the project. For example, we are currently building similar tools and facilities for three productions: Fermirab, one in the UK and the other in France. We discuss each other, exchange knowledge to ensure that our thoughts and processes match. If we experience hiccups, we see what the other teams are doing and establish why they don’t have the same problem.
Civil engineering construction is underway. So far, the tunnels have been completely excavated and our polar buildings are complete. Ownership of this has already been granted to Fermilab, and the building is filled with cold boxes and warm compressors that make up the freezer plant. This device cools the superconducting relack to two Kelvins. These components have made a huge contribution from India’s Ministry of Atomic Energy, and discussions on this began in 2012. Many people are extremely proud to have worked on this collaboration and received the equipment last December. This has been installed in collaboration with my Indian colleagues and the commissioning phase will begin early next year.
There is a lot of work in progress in the SRF cavity. Before receiving full budget approval, we were able to demonstrate the top edge of the PIP-II frontend at the PIP-II injector Test (PIP2IT) facility. That is, from the gallium nitride (GAN) transistor to the first two SRF freeze layers, the beam could be accelerated to the LBNF parameters. This was a major risk mitigation for projects that helped to convince the DOE to release budgets for all projects as it showed that it would achieve the goal at least up to the first two freeze modules. This is followed by another 21 freezing modules with four different flavors, which is a good start. We currently have industry contracts for all flavors of the SRF cavity. As I mentioned, we have completed pre-production cryogenic temperatures again this year, so next year we can start producing all flavors of all the PIP-II cre modules in France, the UK, India and Fermirab.
©Ryan Postel, Fermilab
There is also all the work in progress with the upgrade. For example, we provided collimators to the accelerator department to improve the performance of our current accelerator systems. PIP-II already helps improve the current acceleration chain by delivering hardware and helping to improve the machine.
Could you please explain the freeze modules and the pre-production stage in detail?
Superconducting linacs like the European XFEL and SLAC’s LCLS-II are electronic machines, and use only one type of frozen type. PIP-II accelerates H ions that are much heavier than electrons, so it requires the use of different types of freeze modules and cavities. PIP-II is complicated. This is because we need to deal with five new Cryomodules developed by the Fermilab team and international partners.
The first prototype creo module known as the Single Spoke Resonator 1 (SSR1) was tested in Fermilab after many years of production and is now machine-compatible. Use the prototype as the first unit of the full machine. This is a great achievement.
The second Cry module, the prototype high beta 650 Cry module, was built in Fermilab and shipped to Luxembourg via cargo aircraft. From here it was a track down the channel to a British partner near Manchester. When it was returned to the US and tested here, the same performance was achieved, indicating that the freeze pole can be transported over the Atlantic Ocean without degradation. This was another mammoth achievement.
The RF cavity comes in five flavors. All of them push the boundaries of SRF technology beyond the latest technology in a variety of ways.
We also pursue plasma cleaning in cavities, which allows us to fix any cavity that is problematic during the installation process or operation of the Cry Module. Previously, if any issues occurred, you had to remove the Cry modules from the machine and secure them in order to completely lower them and reach the cavity. Now we don’t need to break it all down, we’re working on ways to repair them on the spot.
What does success at this stage mean for your project in the long run?
Now, success is on schedule and remains on budget.
Every day, around 400 people from Fermilab are involved in the project in one way or another, with at least 200 people being involved overseas through international partners. It is a big, continuous effort, so staying within your schedule and budget is important.
We are in a very dynamic situation and there are many changes in the world and the market. We are actively on the market to buy from all over the world, but this can be a challenge. Our partners also face the same challenges and are completely committed to supporting PIP-II and offering the promises they made years ago. Adjusting this is important. The goal is to deliver what we said so that scientists can later provide the experiments they want to pursue.
What will be next for this pre-production Cryomodule project?
The goal is the complete production of solid-state amplifiers used to power not only the Fermilab but parts of the Italian cavity, French low-beta frozen balls, British high-beta polar machines, and Indian cavity. This is a very important phase of the project and is expected to start next year. The first important step is to demonstrate that these three production frozen polarizations meet the performance requirements of the project. If this is successful, full production can begin. This critical step requires working together to maintain performance, ensure that the process is stable across all five countries, and to maintain the required quality to achieve optimal performance with these critical components. If this does not happen, production should be suspended to understand and resolve the problem before it progresses.
Another important milestone scheduled for next year is to enter into a contract for booster connections. This is a connection to the new Linack tunnel and the Boott tunnel. This involves removal of structure and equipment, and for safety reasons, operation must be stopped at this stage. This important stage of the project should be carried out in close coordination with the rest of the lab to minimize confusion.
About Christian Bofour
Currently Christian is the project director for PIP-II. Christian was a mechanical engineer and began his career at Fermirab in the late 1990s. He moved to German industry for 12 years, gaining experience as a project manager, while still working in the same field of superconducting magnets and accelerators. In 2019, Christian returned to Fermirab to participate in the PIP-II project.
This article will also be featured in the 22nd edition of Quarterly Publication.
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