The HEPS Linac, with a total length of about 49 m, is an s-band normal conducting electron linear accelerator with a very high bunch charge and a large bunch charge range. As the source and first-stage accelerator of electrons, the Linac mainly comprises an electron gun, a bunching system, and a main accelerator.  

 

A number of Linac technological innovations have been developed. Physics-based beam commissioning applications were developed based on the python accelerator physics application set (Pyapas)—a new architecture framework. The accelerating gradient of the S-band accelerating structures with a symmetrical coupler and internal water-cooling system was measured at 33 MV/m. The pulse-to-pulse stability of the solid-state modulator based on insulated gate bipolar transistors was measured at better than 0.02%, improved by about an order of magnitude than the pulse-forming network (PFN) type modulator. The electron gun, with its cathode grid assembly developed in-house, can provide a 14.7-nC beam current for 1 ns at 50 Hz and is the first piece of accelerator equipment installed in the accelerator tunnels. 

 

As one of China's key scientific and technological infrastructure projects during the 13th Five-year Plan, HEPS will not only be the first high energy light source in China but also one of the brightest fourth-generation synchrotron radiation facilities in the world. HEPS began construction in Huairou Science City on June 29, 2019. Over the past nearly four years, installation and RF conditioning of the Linac, along with installation of the booster and the first two beamline hutches, were completed. With building acceptance completed on Dec. 12, and girder installation at the storage ring begun on Feb. 1, HEPS had entered the large-scale equipment installation phase. 

 

Linac online RF conditioning completed on Sept. 23, 2022 (Image by IHEP)

 

HEPS members celebrate the first electron beam accelerated to 500 MeV on March 14, 2023 (Image by IHEP)