The U.S. Department of Energy's Brookhaven National Laboratory is preparing for the development of the Electron-Ion Collider (EIC), a new facility aimed at exploring the atomic nucleus and fundamental forces. The EIC will be built in collaboration with DOE’s Thomas Jefferson National Accelerator Facility and will integrate components from Brookhaven's existing Relativistic Heavy Ion Collider (RHIC). Prior to its transition, RHIC serves as a testing ground for various EIC-related technologies.
Haixin Huang, an accelerator physicist leading these tests known as APEX studies, explained, “We run accelerator physics experiments, or APEX studies, at RHIC every other week for about 16 hours.” These studies have been pivotal in advancing both RHIC's performance and future EIC designs. Since 2020, when Brookhaven was chosen as the site for the EIC, there has been a focus on EIC-related topics.
One major goal is to achieve high luminosity by flattening particle beams. Yun Luo, who leads this effort, stated that flattening beams increases collision likelihood: “The overlapping region for the electron and proton in the EIC collisions will be much smaller than in RHIC collisions.”
Keeping beams cool is essential to maintain their density and increase luminosity. According to Luo, cooling involves injecting relatively cool electrons to extract heat from ion beams: “We need cooling to make the beams smaller — the bunches of particles smaller and more tightly packed together at the interaction point — to create higher luminosity.”
Synchronizing electron and ion beams presents another challenge due to varying speeds at different energies. Adjustments are made by steering proton beams through different trajectories. Guillaume Robert-Demolaize’s team demonstrated precision steering during APEX studies.
Stability of beams is crucial given that interactions within accelerators can destabilize them. Luo noted that future EIC conditions could exacerbate these challenges: “This will be a particular challenge at the EIC because its proton beams will have many more bunches and three times more total particles compared with those at RHIC.”
To mitigate issues like electron clouds which can affect beam stability, measures such as beam screens coated with amorphous carbon are being tested under Silvia Verdu Andres' leadership.
Magnetic interference among multiple rings was identified as a potential issue but resolved through design adjustments allowing electrons to enter at higher energies.
The exploration of neutron characteristics through collisions involving helium-3 nuclei forms part of EIC’s objectives. Accurate polarization measurements are vital for studying neutron spin.
Machine learning has also been employed to enhance collider performance by optimizing beam parameters and disentangling particle motion dimensions.
These ongoing developments highlight significant progress toward realizing the capabilities envisioned for the future Electron-Ion Collider at Brookhaven National Laboratory.