Beijing Electron-Positron Collider

Did the Cultural Revolution impact scientific advancements like the Beijing Electron-Positron Collider? Absolutely. The Beijing Electron-Positron Collider II (BEPC II) stands as a testament to China’s re-emergence onto the global scientific stage. Its story is one of resilience, innovation, and a relentless pursuit of knowledge. The original Beijing Electron-Positron Collider, BEPC, was approved in 1983. This marked a pivotal moment as China began to rebuild its scientific infrastructure after the Cultural Revolution. The importance of this project was underscored by Vice-Premier Deng Xiaoping’s presence at both the groundbreaking ceremony in 1984 and the near-completion ceremony in 1988. The initial BEPC, shaped like a tennis racquet, operated from 1989 to 2004. It consisted of a linac injecting particle beams into a storage ring, achieving collision energies ranging from 3.0 to 5.6 GeV. BEPC was instrumental in investigating tau-charm physics using the Beijing Spectrometer, and made significant contributions, including a precise measurement of the Tau mass. In 2004, the BEPC was decommissioned to make way for its successor, the BEPC II. This upgrade represented a giant leap forward, transforming the original single-ring collider into a double-ring marvel. This was a challenging feat, given the constraints of the existing tunnel’s small size and short circumference. The BEPC II began operations in 2009 and achieved its design luminosity of 1 x 10^33 cm^-2s^-1 in 2016, a world record for its energy range. The BEPC II isn’t just a collider; it’s also a versatile facility. It operates in two modes: collision mode and synchrotron radiation mode. In collision mode, it works with the BES III detector to collect data, producing massive samples of J/ψ and ψ’ events, leading to the discovery of “XYZ” states like the Zc(3900). In synchrotron radiation mode, it powers the Beijing Synchrotron Radiation Facility, supporting experiments from institutions worldwide. This has resulted in over 15,000 hours of dedicated synchrotron radiation light and almost 2,500 publications by the end of 2016. The BES III detector, at the heart of BEPC II’s collision mode, is a technological marvel. It uses a large superconducting solenoid to create a 1-tesla magnetic field and features a helium-based tracking chamber and a caesium iodide crystal electromagnetic calorimeter. The Beijing Electron-Positron Collider II is more than just a machine. It’s a symbol of China’s scientific ambition and a hub for international collaboration, propelling our understanding of the universe at the subatomic level.