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Stabilization of the Polarization Plane in Traveling Wave Deflectors

New possibilities of the polarization plane stabilization in the traveling hybrid TM11 wave deflectors are considered in this paper. These possibilities are realized in two new structures: DLW with two peripheral recesses in cells and DLW with oval aperture. In terms of electrodynamic parameters, thermal regimes and manufacturing technology these structures as well as a classical structure with two stabilizing holes show some advantages and some disadvantages. The advantages of the new structures are good RF mode separation and effective cooling. The specifics of such structures tuning are also described. INTRODUCTION Nowadays linear electron beams accelerated in the superconducting accelerating structures are often used in free electron lasers as core elements. The brightness of the coherent radiation could be very high in case of high average power of the electron beam. Wide variation of wave length is achievable down to X-ray band. The accelerated beam quality is a concern for advanced free electron lasers and therefore these facilities must be equipped with dedicated beam control and measuring system. The deflecting system deviates selected bunches from train and directs them to bunch length monitor and phase space analyzing equipment. Traveling wave RF deflector with transverse electric field Ed is used for this purpose. Disk loaded waveguide (DLW) operating on hybrid TM11 mode is a good choice for deflector. The field polarization plane is often set by two holes made oppositely in the diaphragm [1,2]. Along with this conventional design new solutions namely DLW with oval beam aperture and DLW with two peripheral recesses at cell equator were considered. The traveling wave RF deflector with the phase advance Θ = 120° = 2π/3 and with relative phase velocity 1 / ph = = c v ph β is the most practical choice to combine electrodynamical performance and reasonable production procedure. ELECTRODYNAMICAL CHARACTERISTICS OF THE DEFLECTING STRUCTURE The deflecting voltage ⊥ V in the constant impedance DLW with the same shape of all cells in the structure is determined by following formula: ( ) α − = = α − ⊥ α − ⊥ ⊥ ∫ l z l e E dz e E V 1 0