Status of the microwave inverse FEL experiment

A status report is presented on an inverse free-electron-laser accelerator experiment Operating in the microwave regime (1), This proof-of-principle electron accelerator is powered bq. UP TO 15 MW of RF power at 2.86 GHz, which propagates in a smooth-walled: circular waveguide surrounded by a pulsed bifilar helical undulator; solenoids provide an axial guiding magnetic field. Undulator pitch, which is initially 11.75 cm, is up-tapered to 13.5 cm over the 1-meter length of the structure to maintain acceleration gradient, Numerical computations predict an energy pain of 0.7 MeV using a 6 MeV injected beam from a 2-1/2 cell RF gun, with small energy spread and strong phase trapping. The maximum attainable acceleration gradient with such a design. using 150 MW of RF power at 34 GHz, is estimated to be ar Least 30 MV/m; Results from bench tests of the structure and undulator are presented, along with preliminary brain measurements.