Abstract
This paper describes the construction, rf measurement and tuning, rf conditioning, and beam commissioning of a compact 325 MHz interdigital $H$-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 of $4\text{ }\text{ }\mathrm{MV}/\mathrm{m}$. The efficient shunt impedance $Z{T}^{2}$ is $101\text{ }\text{ }\mathrm{M}\mathrm{\ensuremath{\Omega}}/\mathrm{m}$. 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.
Highlights
The interdigital H-mode drift tube linac (IH-DTL) was first proposed by J
This paper describes the construction, rf measurement and tuning, rf conditioning, and beam commissioning of a compact 325 MHz interdigital H-mode (IH) drift tube linac (DTL) with modified KONUS (Kombinierte Null Grad Struktur, combined zero-degree structure) beam dynamics at Tsinghua University
The tuning target of the IH-DTL cavity is to acquire a resonant frequency of 325 Æ 0.01 MHz under operating conditions (25 °C, vacuum) and a relative error of the field distribution compared with the designed value within Æ3%
Summary
The interdigital H-mode drift tube linac (IH-DTL) was first proposed by J. The 200 MHz IH-DTL at NIRS (the National Institute of Radiological Sciences) is designed with alternating-phase-focusing (APF) beam dynamics [14,28,29,30,31] It can accelerate a 12C4þ or proton beam from 0.6 MeV=u to 4 MeV=u in 3.44 m with a ZT2 of 110 MΩ=m. 325 MHz proton IH-DTL with modified KONUS beam dynamics has been designed at Tsinghua University, taking account of the multiturn injection requirements for a medical synchrotron [34,35]. No internal focusing magnetic lens is needed be installed in the cavity With this kind of KONUS—beam dynamics, a high operating frequency could be employed and a compact and cost-effective injector system could be designed. This paper describes the construction, rf measurement and tuning, high-power conditioning, and beam commissioning of the 325 MHz IH-DTL.
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