The Hefei Infrared Free-Electron Laser facility is developed as a user facility dedicated for energy chemistry research and will deliver the infrared laser in the spectral range of 2.5~200 μm to five research stations. It is consisted of an accelerator system and two FEL oscillators.

The accelerator system combines a 100 keV thermionic electron gun, a 476MHz sub-harmonic standing wave prebuncher, a 2856 MHz fundamental frequency traveling-wave buncher, two 2856 MHz fundamental frequency traveling-wave accelerating tubes separated by a magnetic compressor (chicane). The electron beam energy can be accelerated to beyond 60 MeV. In the 476 MHz sub-harmonic micro-bunch repetition rate, the specifications of the accelerator system include rms energy spread(<240 keV), transverse emittance (20~50 mm mrad) and bunch charge(1~2 nC). While the macro-bunch length and repetition rate are usually set to 4~10 μs and 1~10 Hz, respectively.

The MIR branch of oscillator is for wavelength 2.5~50 μm and the FIR branch is for wavelength 30~200 μm. In each oscillator two spherical mirrors with copper base and gold coatings are used to form a symmetrical optical cavity with 5.04 m long. Two planar permanent-magnet undulators are placed in the center of the two optical cavities. The cavity length for both two oscillators is 5.04 m. The infrared radiation is outcoupled from the downstream cavity and transported through the same beam line to the experimental hall.