Scientists at the U.S. Department of Energy’s Brookhaven National Laboratory have reached a landmark achievement by designing and testing the world’s highest-voltage polarized electron gun.
This groundbreaking technology is a critical stepping stone toward building the Electron-Ion Collider (EIC), the first facility of its kind to fully utilize polarized electrons for investigating the core components of matter.
The exciting development took place at Brookhaven in collaboration with the DOE’s Thomas Jefferson National Accelerator Facility.
The EIC is poised to enhance our understanding of the internal structure of protons by colliding electrons and protons at nearly light speed.
By doing so, scientists aim to unravel the mysterious origins of proton spin—a fundamental property influencing the behavior of visible matter.
The polarized electron gun, developed and spearheaded by physicist Erdong Wang, achieved an acceleration of electrons to 80% of the speed of light within a mere two-inch distance.
The acceleration speed equates to a startling 500 million miles per hour in a split second, marking a significant stride towards high-speed electron collisions with protons and ions in the EIC’s 2.4-mile-circumference collider ring.
Producing short, tightly packed bunches of electrons where spins are aligned in uniform directions is a crucial feature of this electron gun.
These characteristics allow the electrons to effectively explore the internal structures of protons when accelerated by radiofrequency cavities, which provide the necessary energy boosts.
To achieve such precise electron alignment, the scientists made use of nanostructured gallium arsenide photocathodes that emit highly polarized electron beams in response to laser stimulation.
The innovative photocathode structure—developed with collaboration from Old Dominion University and Jefferson Lab—features a superlattice layer designed to enhance photoelectric efficiency while maintaining high polarization of the electron beam.
Critical to the electron gun’s success is its high-voltage performance.
Instead of traditional insulating gases, which may pose environmental hazards, the team innovated a novel high-vacuum enclosure and used a specialized dielectric fluid to prevent voltage leakage.
The focus on environmentally friendly practices not only bolstered efficiency but also eliminated greenhouse gas emissions typically associated with older systems.
The project not only overcame technical challenges associated with vacuum systems and high-voltage electron extraction but also dealt with issues like hydrogen gas interference.
The successful operation of the electron gun, having reached 350 kilovolts within 23 hours, was maintained successfully for six months without maintenance, confirming its reliability and performance.
Now, efforts are underway to develop further stages of electron acceleration and potential higher-voltage electron guns, as research continues to push the boundaries of particle physics and deepen our comprehension of the universe’s most fundamental particles, quarks, and gluons.
The findings from this research have been published in the journal Applied Physics Letters, showcasing the continuous innovation at the intersection of nuclear physics and engineering.
As the Electron-Ion Collider nears completion, it promises to unfold new chapters in the understanding of particle physics and the forces governing the universe.