Design of EPU oscillator cavity in femtosecond accelerator

We adopt the groove guide as the cavity of the undulator to reduce the diffraction effect. The groove guide has the advantages of lower surface energy loss, larger power capacity, less modes, and larger structure dimension over the traditional method waveguide. The attenuation calculation is given in this paper including the cavity optimization. And the dispersive character indicates that the oscillator can work in different modes with the change of the electron beam energy.