• H. S. Marks, J. Dadoun, O. Faingersh, Kh. Garb, A. Gover
  University of Tel-Aviv, Faculty of Engineering, Tel-Aviv
• B.Yu. Kapilevich, B. Litvak
  Ariel University Center of Samaria, Faculty of Engineering, Ariel

The design, operating principles, and results of characterization for a novel resonator are outlined. Measurements were conducted prior to insertion into the Wiggler cavity for future testing under lasing. The W-band (75-110 GHz) resonator consists of two Talbot splitters and two confocal cylindrical mirrors for decoupling the electron beam from the radiation, a corrugated waveguide, and an adjustable three grid reflector system. Two degrees of freedom have been built into the grid system, firstly, the central grid can be rotated via remote control to alter the out-coupling coefficient, and secondly, also using a motor it is possible to remotely move the grid system back and forth altering the length of the resonator. Allowing continuous tuning of the longitudinal mode resonant frequencies (spaced about 100MHz apart). The radiation pattern of the resonator mode is nearly a Gaussian. The round trip reflectivity and its Q factors where measured by matching the S parameters of the device (measured with a Scalar VNA) to the theoretical Fabry-Perot resonator reflection and transmission curves. Based on this estimate the roundtrip losses of the tunable resonator are less than 35%.

• H. S. Marks, E. Dyunin, A. Gover, M. Volshonok
  University of Tel-Aviv, Faculty of Engineering, Tel-Aviv
• Y. Lasser, R. Shereshevsky, A. Yahalom
  Ariel University Center of Samaria, Faculty of Engineering, Ariel

Deviations in the electron beam trajectory through the planar wiggler of the Israeli Electrostatic Accelerator FEL were found to be primarily caused by small variations in the strength and angle of polarisation of lateral focussing bar magnets which are positioned on both sides of the wiggler, and provide a quadrupole guiding field on axis. The field of the wiggler on axis was measured using a Labview controlled automated system built in our lab, based on a 2-axis Hall Effect magnetic sensor driven by a stepper motor. Polarisation field components of the individual focussing magnets were measured separately. Then, using an algorithm, the focussing magnets were paired, such that their non-uniformities were utilised to not only cancel out each other's error, but also to cancel out the field errors on axis due to variation in strength and polarisation angle of the wiggler magnets. The quality of the predicted electron beam transport was evaluated by 3-D simulation with the General Particle Tracer code which allowed the input of all the measured fields.