Modifications of THOR for IR FEL

The goal of the proposed program is to perform a feasibility study and develop a design for modifying the THOR electron accelerator at NSWC. The modification is required to enable THOR to drive a high-power free-electron laser (FEL) in the infrared. Research is underway to use THOR to drive a 94-GHz high-power FEL. If this program is successful, the 94 GHz radiation could be used as a wiggler field for a second stage interaction that could generate powerful, coherent IR radiation. However, a very high quality electron beam is required for the second stage of the FEL. During Phase I, we propose to use detailed measurements of the electron beam quality on THOR (both voltage flatness, which is determined largely by the Marx circuitry, and beam emittance, which is controlled by the beam diode and transport system) along witgh FEL simulations to quantify the degree of improvement that is required. Modifications to the Marx will be analyzed using a SPICE model. Beam diode modifications will be guided by numerical simulations, using MAGIC and E-Gun. The designs will maintain compatibility with an optimized two-stage or dual-mode FEL that can couple out either the first stage output (millimeter wave) or the second stage output (IR). The fabrication and testing of these modiications and their installations at NSWC will be performed during Phase II.