Development of a compact 325 MHz proton interdigital H -mode drift tube linac with high shunt impedance

This paper describes the construction, rf measurement and tuning, rf conditioning, and beam commissioning of a compact 325 MHz interdigitalH-mode (IH) drift tube linac (DTL) with modified KONUS (Kombinierte Null Grad Struktur, combined zero-degree structure) beam dynamics at Tsinghua University. This IH-DTL accelerates a proton beam from 3 MeV to 7 MeV in about 1 m. With a high rf frequency of 325 MHz, the cavity is designed to be compact while retaining a high average gradient of4MV/m. The efficient shunt impedanceZT2is101MΩ/m. The beam test results show good agreement with the beam dynamics design. The developed compact IH-DTL can be applied to the injectors of medical proton machines.