Design, fabrication, and low-power rf measurement of an X-band dielectric-loaded accelerating structure

This paper presents the design, fabrication, and low-power rf measurement of an externally powered <math display="inline"><mi>X</mi></math>-band dielectric-loaded accelerating (DLA) structure with a dielectric constant <math display="inline"><mrow><msub><mi>ϵ</mi><mi mathvariant="normal">r</mi></msub><mo>=</mo><mn>16.66</mn></mrow></math> and a loss tangent <math display="inline"><mrow><mi>tan</mi><mi>δ</mi><mo>=</mo><mn>3.43</mn><mo>×</mo><msup><mrow><mn>10</mn></mrow><mrow><mo>−</mo><mn>5</mn></mrow></msup></mrow></math>. A dielectric matching section for coupling the rf power from a circular waveguide to an <math display="inline"><mi>X</mi></math>-band DLA structure consists of a compact dielectric disk with a width of 2.035 mm and a tilt angle of 60°, resulting in a broadband coupling at a low rf field which has the potential to survive in the high-power environment. Based on simulation studies, a prototype of the DLA structure was fabricated. Results from low-power rf measurements and the comparison with simulated values are presented. A significant discrepancy was found between measurements and simulations. The detailed analysis on the fabrication errors which may cause the discrepancy is also discussed.