Design of the Jefferson Lab IR Upgrade FEL optical cavity

Jefferson Lab is in the process of upgrading the Free-Electron Laser Facility to provide higher output power as well as broader wavelength and timing flexibility. As part of the upgrade, a new optical cavity is being constructed. Using a near-concentric configuration, it will provide high average power (10kW) output using one of three sets of dielectrically coated mirrors. A fourth mirror set will provide broadband tuning throughout the mid-IR, but at a lower average power of 1kW. The new optical cavity offers unique features such as in vacuo active stabilization of the mirror orientation and deformable high-reflector mirrors. The status of the construction of the optical cavity and a review of its capabilities will be presented