The distortion of the accelerating field distribution in compensated structures due to steady-state beam loading

Using a general electrodynamic approach and particular properties of compensated accelerating structures, the effect of distortions in an accelerating field distribution due to RF power losses in surfaces and for beam acceleration is considered. Consideration shows, that for proton linacs of `meson facility´ type (impulsive beam current I_b ≃50 mA, acceleration rate U_a~2÷6 MV/m) this effect is not important for all accelerating structures known. When the beam current I_b~100-300 mA and U_a~1 MV/m (like linacs for accelerator-driven transmutation technologies), in the structures with small group velocity (β_g≈0.04) significant distortions will arise and the efficiency of the structure for beam acceleration will drop. For structures with a large group velocity (β_g≈0.4) such effects will arise at a beam current of several amperes