Newswise — NEWPORT NEWS, VA – The project to build the Electron-Ion Collider (EIC) is now underway, and it has reached its first purchasing milestone: A long-lead procurement contract has successfully been completed with the delivery and acceptance of 1,069 lead-tungstate crystals. The crystals will form the main portion of one subsystem of the collider’s new detector.
The EIC will be a U.S. Department of Energy Office of Science user facility for nuclear physicists who are studying the building blocks of our visible universe. It is being built at the DOE’s Brookhaven National Laboratory in Upton, New York, in partnership with DOE’s Thomas Jefferson National Accelerator Facility in Newport News, Virginia.
The EIC will circulate two beams of particles – electrons and ions – in opposite directions. The beams of electrons and ions consist of groups or “bunches” of these particles in a continuous chain. Every ten nanoseconds, an electron bunch and an ion bunch will collide inside the EIC detector, the Electron-Proton/Ion Collider (ePIC) Detector. ePIC is a house-sized system of individual detectors that will capture the aftermath of these collisions.
Alexander Bazilevsky, a physicist at Brookhaven Lab, is the manager for electromagnetic calorimetry for the ePIC detector. He leads three projects to build electromagnetic detectors for ePIC, including the Electron Endcap Electromagnetic Calorimeter (EEEMCAL, pronounced “triple-E-M-cal”), for which the lead-tungstate crystals were purchased.
“The main goal of this calorimeter is to measure beam-scattered electrons, which gives critically important information for all measurements at EIC. Such a calorimeter should be very compact, very precise, very fast, and radiation tolerant,” Bazilevsky said. “And when we formulated all the requirements, we found that basically the only practical technology could be just the one based on these crystals.”
The EEEMCAL will measure the energies of the electrons it collects. The detector requires about 3,000 custom-grown lead-tungstate crystals, which will take several years to make. To ensure the detector would be ready for installation on time, the procurement of these crystals was pegged as a long-lead item.
In April 2024, DOE approved Critical Decision-3A (CD-3A), which cleared the way for long-lead procurements. The first of a three-phase purchase contract soon began. The first order was placed with the U.S. arm of Crytur, a leading producer of synthetic crystals for science and advanced technologies based in Czechia (Czech Republic). Crytur would deliver about a thousand, or one-third, of the crystals needed for the detector in each of the phases.
The next step for the project was then to receive the crystals and begin quality testing each to ensure they meet the detector’s rigorous requirements. Joshua Crafts, a graduate student who is pursuing his Ph.D. at The Catholic University of America, worked on this part of the process with others at CUA.
“Crytur sent an initial pilot batch. We processed that,” Crafts said. “That established the workflow and made sure that everyone was happy with the overall process of how we were testing the crystal quality, and with the back and forth between Jefferson Lab, Brookhaven Lab, and Crytur.”
After that initial batch, about 100-120 crystals per month have been delivered, for a total of 1,069 crystals so far. A delivery in February concluded phase one and the first contract.
“And that’s all been ingested here at Jefferson Lab and then processed, cleared and accepted,” he said. “We have not had to reject any crystals as of this point. There have been no crystals that have failed to meet our overall quality goals.”
The next step will be continuing with the phase two purchase contract, as well as more extensive testing on the crystals delivered in phase one. Additionally, the mechanical design of the full detector unit continues, with fabrication of the frame to follow.
According to Tanja Horn, a professor at The Catholic University of America and Craft’s thesis advisor, this is where other members of the EEEMCAL collaboration will further contribute to the work.
“There are other key properties of the crystals, like the light yield, that are monitored throughout the delivery process. As in the crystal quality testing for acceptance, universities play a key and substantial role in this process. The Catholic University of America has an established test bench, but we have been commissioning additional test benches at James Madison University, the University of Kentucky, and Abilene Christian University. This also ensures that detector skills are propagated and maintained in the field,” Horn said.
Horn and Crafts are no strangers to this particular crystal technology. They both had key roles in the project to build, install, and operate the Neutral Particle Spectrometer in Jefferson Lab’s Continuous Electron Beam Accelerator Facility, another DOE Office of Science user facility.
That detector uses about 1,000 lead-tungstate crystals and was supported by a National Science Foundation Major Research Instrumentation grant. The Laboratoire de Physique des 2 Infinis Irène Joliot-Curie (Laboratory of the Physics of the two infinities Irène Joliot-Curie) (IJCLab) also contributed to the NPS detector build. Each of these institutions, as well as Ohio University, Florida International University, and The A.I. Alikhanyan National Science Laboratory (Yerevan Physics Institute) are all now also contributing to EIC science. For instance, IJCLab is gearing up to produce the mechanical frame and other supporting systems for the EEEMCAL collaboration.
“Tanja’s group suggested building such a calorimeter in the electron-endcap region of the EIC detector. They are highly qualified and highly experienced and know all the possible details to design, build, and operate a lead-tungstate crystal calorimeter. It means that selecting their proposal was very much risk-free, which is critically important for such a challenging and complicated project,” Bazilevsky confirmed.
Meanwhile, the Neutral Particle Spectrometer was successfully installed in 2023 and later commissioned. It is currently in operation at Jefferson Lab, and Crafts and Horn are involved in data analysis from the 2023-2024 experimental run with that detector. This research is also the focus of Crafts’ Ph.D. thesis work.
These physicists are all looking forward to the day when they can begin experiments with EEEMCAL.
“So, my background is spin physics, the polarized proton structure studies with spin polarized beams. Here at Brookhaven with the Relativistic Heavy Ion Collider, we have produced a wealth of remarkable results from polarized proton collisions. Now with EIC, we will continue these studies utilizing the collisions of polarized electrons with polarized protons. It will provide us with a deeper look inside the proton with ultimate precision, bringing us to a qualitatively new level of proton structure studies,” Bazilevsky said.
RHIC, another DOE Office of Science user facility sited at Brookhaven National Laboratory, recently completed its last experimental run and was shut down to make way for the EIC, which will be built by reusing major components of RHIC.
Horn wants to continue her studies of the structures of particles called pions and kaons. These particles are some of the simplest that, like protons and neutrons, are made of quarks and gluons. She has been leading a science program with focus on deepening nuclear physicist’s understanding of charged pions and kaons — in physics terms, that’s detailing their form factors, structure functions, and masses — and to provide measurements to validate the framework for 3D (spatial) hadron imaging.
“The EIC, with an acceptance optimized for far-forward physics, allows for accessing pion and kaon structure functions over a large kinematic region through the Sullivan process. The EEEMCAL provides this high-precision detection of the scattered electron that one needs to detect to study the pion and kaon structures,” Horn said. “I find that a really exciting direction at the EIC — that we have the opportunity to study these processes.”
Further Reading
Electron-Ion Collider Set to Begin Long-Lead Procurements
DOE Approves Next Phase of Funding for Electron-Ion Collider
A Smashing Success: Relativistic Heavy Ion Collider Wraps up Final Collisions
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DOE’s 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, visit https://energy.gov/science
