First operation of the HAP/MOPA traveling wave structure at Boeing FEL

The first of six 1.3-GHz, 18-cell, constant impedance, traveling wave linac structures has been placed under RF power and used to accelerate an electron beam. The design of the structures and low power measurements of insertion loss and group delay are described. The observed voltage gain under high power is compared with predictions based on low power measurements and URMEL calculations for the accelerator mode in a single cell.