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The Brookhaven Plan

Adding an electron ring to Brookhaven's existing accelerator complex would be a cost-effective, practical strategy for achieving the scientific goals of an electron-ion collider

eRHIC: Colliding Electrons with Ions at RHIC

There are many compelling reasons to build an Electron-Ion Collider at Brookhaven National Laboratory, including the Lab’s rich physics history, accelerator expertise, and the existence of a fully functional and productive proton/heavy-ion accelerator/collider—the Relativistic Heavy Ion Collider (RHIC)—and its international collaborations of physicists eager to continue their explorations of matter. Adding an electron ring and other accelerator components to the existing RHIC accelerator complex would be a cost-effective, practical strategy for achieving the scientific goals of an Electron-Ion Collider.

The current proposed design for an EIC integrated with RHIC—dubbed eRHIC—calls for the addition of an electron ring inside the existing RHIC tunnel, capable of reaching energies up to 18 billion electron-volts (GeV). Both the ion and electron beams would be polarized to allow physicists to study the details of nuclear spin and how it is related to nuclear structure. Thus, eRHIC would be the world's first spin-polarized electron-nucleus collider. It would have the flexibility to change the nuclear ion species as well as the beam energies — both crucial for the systematic study of the “glue” postulated to dominate the internal structure of nuclear matter.

schematic of eRHIC

1. Ion Source

One of Brookhaven Lab’s polarized ion sources will inject bunches of ions into the Lab’s existing chain of accelerators to bring the particles up to higher and higher energy—starting with the circular Booster, then the Alternating Gradient Synchrotron, and finally, into one of RHIC’s existing superconducting magnet ion storage rings (shown in gold).

2. Electron Cooling

The electron cooler keeps the velocity of heavy ions/protons highly uniform and tightly bunched to achieve the high collision rates required for much of the EIC physics program.

3. Electron Source

Electrons produced in a polarized electron gun would be accelerated to 18 billion electron volts (GeV) by a rapid-cycling synchrotron (red) in the RHIC tunnel. From there they would be injected into a second storage ring (green) for collisions with the ions. Collisions occur at the point where the two storage rings intersect with the action captured by one or more detectors.

Strengths of eRHIC

Building eRHIC would enable the full science plan envisioned for an EIC. The fact that protons and ions in RHIC reach very high energy will be important especially to some aspects of that program. The eRHIC facility would be built by reusing the entire existing RHIC complex—including the RHIC machine, its chain of injector accelerators, the tunnel, and other infrastructure. Only a modest amount of civil construction would be required to accommodate this design, making it economically attractive and minimizing its environmental impact.

Transforming RHIC to eRHIC will lead to novel particle cooling schemes to keep beams tightly bunched. Such beam-cooling systems will be essential to achieve the highest collision rates required for a considerable fraction of the EIC physics program.

The project will also lead to advances in superconducting magnet and radiofrequency technologies.

For details on Brookhaven’s EIC design see the eRHIC Pre-conceptual Design Report.

Building an EIC at Brookhaven Lab would also enable the continued operations of two key facilities with widespread benefit beyond the Laboratory:

Building an EIC will bring additional benefits to science and society.

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Brookhaven National Laboratory advances fundamental research in nuclear and particle physics to gain a deeper understanding of matter, energy, space, and time; applies photon sciences and nanomaterials research to energy challenges of critical importance to the nation; and performs cross-disciplinary research on climate change, sustainable energy, and Earth’s ecosystems.