Preliminary Results on the Simultaneous Excitation of the Tm010and Te011Modes in a Single Cell Niobium Cavity

Simultaneous excitation of both TM010and TE011mode has been carried out on a CEBAF single cell cavity. The cavity has two beam pipe side-ports for each mode for input and pick-up couplers. Coupling to the TE011mode is done by magnetic loop couplers while for the TM010mode coaxial antennas are used. Simultaneous excitation of both TM and TE modes has been proposed recently for superconducting photoinjector applications to take advantage of the accelerating electric field of the TM mode, combined with the focusing magnetic field of the TE mode. The TE011mode has the property of having zero surface electric field, surface magnetic field orthogonal to the one in the TM010mode and concentrated in the iris/wall regions of the cavity. The presence of both modes in the cavity at the same time can also be used to investigate the so-called high field Q-drop in the TM010mode. This paper will present some preliminary result on the test of the single cell cavity at 2 K.