The U.S. Department of Energy’s (DOE) Brookhaven National Laboratory is set to revolutionise our understanding of atomic nuclei and their binding forces.
This transformation will be spearheaded by the Electron-Ion Collider (EIC), a groundbreaking particle accelerator designed in partnership with DOE’s Thomas Jefferson National Accelerator Facility.
By integrating cutting-edge technologies, the EIC promises to unravel mysteries of the subatomic world while advancing the field of accelerator physics.
A new era at Brookhaven: From RHIC to EIC
The EIC builds on the legacy of Brookhaven’s Relativistic Heavy Ion Collider (RHIC), which has been a cornerstone of particle physics research for over two decades.
The transition to the Electron-Ion Collider involves repurposing one of RHIC’s ion accelerator rings and integrating new components, including an electron accelerator ring, a storage ring, and advanced instrumentation.
This hybrid design not only maximises the reuse of existing infrastructure but also paves the way for an unprecedented level of precision and innovation.
Even as RHIC’s operational phase winds down, it plays a pivotal role as a testbed for solving engineering and physics challenges integral to the EIC. The Accelerator Physics Experiment (APEX) program at RHIC has already provided critical insights that have influenced the EIC’s design.
Boosting collision rates
A fundamental goal of the Electron-Ion Collider is achieving high luminosity, a measure of how frequently particle collisions occur. These collisions generate the data necessary for groundbreaking discoveries about the building blocks of matter.
In RHIC, ion beams are shaped to maximise collision rates at specific interaction points. For the EIC, physicists are refining this concept further by flattening proton and ion beams into ribbon-like shapes.
This innovative approach increases the probability of interaction with the oncoming electron beam, thus enhancing the collider’s overall performance.
Keeping particle beams cool and compact
Maintaining ‘cool’ beams is essential for achieving high luminosity. When particles heat up, their motion becomes erratic, causing the beam to expand and reducing collision rates. To counteract this, Brookhaven scientists employ an electron cooling technique.
By introducing relatively cool electron beams to travel alongside the ion beams, they extract heat and counteract the natural repulsion between positively charged ions.
For the Electron-Ion Collider, this cooling process will be extended and optimised. Scientists plan to use a longer cooling section, higher electron intensities, and innovative configurations to keep the ion beams tightly packed and highly efficient.
Synchronising and stabilising particle trajectories
One of the EIC’s unique challenges is synchronising beams of electrons and protons, which travel at different speeds depending on their energy levels.
To ensure collisions occur precisely at the interaction point, Brookhaven researchers have developed advanced magnet systems that dynamically adjust the proton beam’s trajectory. These systems were rigorously tested during RHIC’s APEX studies, paving the way for seamless integration into the EIC.
Stability is another critical factor. As ion beams complete tens of thousands of turns per second within the Electron-Ion Collider, interactions with the accelerator’s environment can lead to instabilities.
To address this, Brookhaven scientists have tested damping systems and coatings, such as amorphous carbon, that mitigate unwanted electron clouds and heat buildup.
Overcoming magnetic interference
The EIC’s complex design includes three distinct accelerator rings: one for ions, one for colliding electrons, and another for accelerating electrons to collision energy.
However, magnetic interference among these rings posed a potential obstacle. Through APEX experiments, researchers discovered that pre-accelerating electrons to higher energy before injection into the EIC mitigates this interference.
This finding has been incorporated into the collider’s design, ensuring smooth operation at all energy levels.
Unlocking neutron secrets
While the Electron-Ion Collider is primarily designed to probe protons, researchers are also keen to explore the structure of neutrons, a key component of atomic nuclei.
Because neutrons lack an electric charge and cannot be accelerated directly, the EIC will instead use simple nuclei like helium-3 to study neutron properties.
Recent experiments at RHIC tested methods to measure the polarisation of helium-3 nuclei, a critical step for understanding neutron spin. These studies have refined the tools and techniques that will be deployed at the Electron-Ion Collider.
Harnessing artificial intelligence for EIC optimisation
Artificial intelligence (AI) is playing an increasingly significant role in advancing accelerator physics. At RHIC, researchers used machine learning to optimise beam parameters and disentangle particle motion, laying the groundwork for AI-driven performance enhancements at the Electron-Ion Collider. These techniques promise to streamline operations and maximise the collider’s scientific output.
EIC: Building the future of science
As Brookhaven National Laboratory transitions from RHIC to the Electron-Ion Collider, it stands at the forefront of scientific innovation.
The EIC will not only advance our understanding of the atomic nucleus but also inspire new generations of scientists and engineers to push the boundaries of technology and knowledge.
With construction underway and groundbreaking experiments on the horizon, the EIC promises to unlock a new era of discovery.
