A hybrid dielectric and iris loaded periodic accelerating structure

摘要

One disadvantage of conventional iris-loaded acceleratingstructures is the high ratio of the peak surface electric field to thepeak axial electric field useful for accelerating a beam. Typically thisratio E_s/E_a ⩾ 2. The high surface electricfield relative to the accelerating gradient may prove to be a limitationfor realizing technologies for very high gradient accelerators. In thispaper, we present a scheme that uses a hybrid dielectric and iris loadedperiodic structure to reduce E_s/E_a, to near unity,while the shunt impedance per unit length r and the quality factor Qcompare favorably with conventional metallic structures. The analysisbased on MAFIA simulations of such structures shows that we can lowerthe peak surface electric field close to the accelerating gradient whilemaintaining high acceleration efficiency as measured by r/Q. Numericalexamples of X-band hybrid accelerating structures are given