Electron-Ion Collider in China

Electron-Ion Collider in China. The Electron-Ion Collider in China (EicC) is a major proposed nuclear physics facility under development by the Institute of Modern Physics at the Chinese Academy of Sciences. Designed as a high-luminosity, medium-energy electron-ion collider, it aims to probe the internal structure of hadrons and the properties of QCD matter. The project represents a cornerstone of China's strategy to become a global leader in fundamental physics research, complementing international efforts like the Electron-Ion Collider at Brookhaven National Laboratory.

Overview

The EicC is conceived as a next-generation facility to investigate the fundamental building blocks of atomic nuclei and the force that binds them, described by the theory of Quantum chromodynamics. Located in China, the project is spearheaded by leading scientists from the Institute of Modern Physics and involves a broad coalition of domestic research universities. Its scientific program is positioned to address key unanswered questions in nuclear physics that are beyond the reach of existing machines like the Relativistic Heavy Ion Collider or the Continuous Electron Beam Accelerator Facility. By colliding polarized electron beams with polarized proton and light ion beams, as well as heavier nuclei, the EicC will provide a unique three-dimensional map of hadron structure.

Scientific Goals

The primary scientific mission centers on achieving a deep understanding of the spin structure of the proton and neutron, seeking to resolve the long-standing "proton spin crisis" by precisely measuring the contributions of gluons and sea quarks. A major focus is the exploration of the spatial and momentum distributions of partons inside nucleons and nuclei, a field known as generalized parton distributions and transverse-momentum-dependent distributions. Furthermore, the EicC will study the formation and properties of exotic hadron states and the transition of normal nuclear matter to a dense gluon-dominated state, often referred to as the Color Glass Condensate. This research has implications for understanding the conditions of the early universe and the interiors of neutron stars.

Design and Technical Specifications

The baseline design envisions a double-ring collider with a circumference of approximately 1.3 kilometers, utilizing advanced superconducting radio frequency technology for beam acceleration. It is designed to collide polarized electron beams with energies ranging from 3 to 20 GeV with polarized proton beams from 15 to 25 GeV, and heavier ion beams, such as carbon or calcium, with energies up to 100 GeV per nucleon. Achieving a high luminosity up to 10³⁴ cm⁻²s⁻¹ is a critical technical goal, requiring innovations in cryogenics, beam cooling, and interaction region design. The detector concepts, influenced by those at the COMPASS experiment and HERA, will incorporate high-precision silicon trackers, calorimeters, and particle identification systems to capture the complex final states from collisions.

Project Development and Timeline

The project originated from a series of national workshops and strategic planning exercises organized by the Chinese Academy of Sciences following the 2015 International Workshop on Electron-Ion Collider in China. A key milestone was the completion of a comprehensive conceptual design report, which underwent rigorous international peer review. The current phase involves extensive R&D on critical components, including the superconducting magnet system and the polarized electron source. Pending final approval and funding from the National Development and Reform Commission, the construction phase could begin in the late 2020s, with commissioning and first physics runs anticipated in the mid-2030s. The timeline is coordinated with other major Chinese projects like the High Intensity Heavy-ion Accelerator Facility.

International Context and Collaboration

The EicC is a pivotal component of the global landscape in nuclear physics, operating in a complementary energy regime to the high-energy Electron-Ion Collider under construction at the Brookhaven National Laboratory in the United States. It fosters extensive international collaboration, with scientific input and potential hardware contributions from institutions like GSI Helmholtz Centre for Heavy Ion Research, CERN, and KEK. Chinese scientists actively participate in global forums such as the International Committee for Future Accelerators and the Asian Committee for Future Accelerators. These partnerships ensure the EicC integrates into the worldwide effort to advance the field of QCD, sharing expertise and data with facilities like the Large Hadron Collider and the future Facility for Antiproton and Ion Research.

Category:Particle accelerators Category:Nuclear physics Category:Science and technology in China