Construction and Commissioning of Mid-Infrared SASE FEL at cERL

TL;DR

This paper reports the successful construction and operation of a mid-infrared SASE FEL at cERL, demonstrating its potential as a tunable, high-power light source despite space charge challenges.

Contribution

It is the first demonstration of a mid-infrared SASE FEL in an ERL layout, highlighting its advantages and feasibility for future applications.

Findings

FEL emission observed at 20 μm wavelength

Beam conditions successfully established at undulators

Potential for cERL as a mid-infrared light source

Abstract

The mid-infrared range is an important spectrum range where materials exhibit a characteristic response corresponding to their molecular structure. A free-electron laser (FEL) is a promising candidate for a high-power light source with wavelength tunability to investigate the nonlinear response of materials. Although the self-amplification spontaneous emission (SASE) scheme is not usually adopted in the mid-infrared wavelength range, it may have advantages such as layout simplicity, the possibility of producing a single pulse, and scalability to a short-wavelength facility. To demonstrate the operation of a mid-infrared SASE FEL system in an energy recovery linac (ERL) layout, we constructed an SASE FEL setup in cERL, a test facility of the superconducting linac with the ERL configuration. Despite the adverse circumstance of space charge effects due to the given boundary condition of the facility, we successfully established the beam condition at the undulators, and observed FEL emission at a wavelength of 20 $\mu$m. The results show that the layout of cERL has the potential for serving as a mid-infrared light source.