WaterFEL Facility Description

The entire basement level of WaterFEL is designated as a NEW area and houses the accelerator vault and associated infrastructure that generate the infrared free electron laser beam. Additional NEW-designated spaces include the main control rooms and the optics base (calibration laboratory) on the first floor, where beam diagnostics, optical alignment, and precision calibration are performed. These controlled areas ensure safe operation of the accelerator and laser systems while supporting continuous experimental optimization.

WaterFEL’s first floor also contains a suite of advanced laboratories specifically designed to couple infrared FEL radiation with complementary experimental platforms. These include laboratories for ultrafast electron diffraction, ion mobility–mass spectrometry, velocity map imaging, cryogenic spectroscopy, infrared and Raman microscopy, atomic force microscopy, and ultrafast femtosecond laser systems. Together, these capabilities enable multimodal investigations spanning gas-phase molecular dynamics, condensed-matter physics, biomolecular structure, chemical reaction mechanisms, and nanoscale materials characterization.

The second floor of the facility provides collaborative and operational support spaces, including meeting rooms for scientific exchange, a kitchenette area, an open-plan workspace for students and postdoctoral researchers, and private offices for staff and visiting principal investigators. The mechanical room—also located on this level—houses critical building systems, including a dedicated de-ionized water plant that supports accelerator and laboratory operations.

By integrating a CNSC-licensed accelerator facility with state-of-the-art experimental laboratories and collaborative spaces, WaterFEL serves as a secure, internationally accessible hub for cutting-edge infrared photonics research.

The electron beam in a free electron laser (FEL) is delivered in a hierarchical pulse structure designed to optimize laser gain and temporal control. The linear accelerator produces discrete macrobunches separated by approximately 100 milliseconds. Each macrobunch consists of a pulse train about 10 microseconds in duration. Within this train are roughly 10,000 individual micropulses, each representing a tightly compressed electron packet approximately 1 picosecond long. These micropulses are spaced by about 1 nanosecond, forming a precisely timed sequence of ultrashort electron bursts. This structured timing enables efficient interaction between the electron beam and the optical field in the undulator, allowing coherent radiation to build up within each macropulse while maintaining controlled repetition at the macrobunch level.

Infrared laser light in a free electron laser (FEL) is generated when a high-energy electron beam, accelerated to near the speed of light, passes through a periodic magnetic structure known as an undulator. The alternating north and south magnetic poles force the electrons to oscillate transversely, causing them to emit synchrotron radiation at a wavelength determined by the electron energy and the undulator parameters. Within an optical cavity formed by mirrors, this initially spontaneous radiation interacts with the oscillating electron beam, inducing an energy modulation that evolves into microbunching of the electrons at the radiation wavelength. As these microbunched electrons emit in phase, the radiation grows coherently and amplifies on each pass through the cavity. The result is intense, tunable, and coherent infrared laser light, with the output wavelength readily adjustable by changing the electron beam energy or the magnetic field strength of the undulator.