Design, fabrication, and test of a parallel-coupled slow-wave high-gradient structure for short input power pulses

Tsinghua University has designed an X-band (11.424 GHz) slow-wave parallel-coupled ten-cell standing-wave accelerator structure, operated it at a high gradient with 40-ns-long rf pulses. Unexpected bead-pull results were observed during the cold testing, which we attribute to intercavity coupling. To explain these results, a multicell coupling circuit model was developed and used to analyze the data. High-power testing was conducted on the TPOT-X platform, achieving a highest gradient of <a:math xmlns:a="http://www.w3.org/1998/Math/MathML" display="inline"><a:mrow><a:mn>130</a:mn><a:mtext> </a:mtext><a:mtext> </a:mtext><a:mi>MV</a:mi><a:mo>/</a:mo><a:mi mathvariant="normal">m</a:mi></a:mrow></a:math> after <d:math xmlns:d="http://www.w3.org/1998/Math/MathML" display="inline"><d:mn>1.1</d:mn><d:mo>×</d:mo><d:msup><d:mn>10</d:mn><d:mn>7</d:mn></d:msup></d:math> conditioning pulses. Compared to conventional multicavity high-gradient structures, the distributed power feeding system offers a shorter conditioning period and demonstrates the potential to achieve higher accelerating gradients under short-pulse operation.