In order to figure out the migration and deposition of impurities on the first wall of HL-2A/2M tokamak, Peking University and Southwestern Institute of Physics are co-developing a deuteron RFQ as part of the in situ ion-beam diagnostic for the material. The RFQ, which operates at 162.5 MHz, is designed to accelerate a 10-mA deuteron beam from 40 keV up to 1.5 MeV. Key design considerations and the final design parameters are presented. The RFQ has been conditioned at a 1% duty factor for 80 h at RF cavity power of 55 kW. The specific shunt impedance of the cavity is 221 kΩ·m by measuring the bremsstrahlung spectrum. The intrinsic Q-value after the high-power tests measured by the Ring-Down method is 13,780. Beam commissioning has been taken place during the first half of 2021, and the beam measurements include beam current and energy of ²H⁺ ion. A 10 mA ²H⁺ beam was successfully accelerated through the RFQ.

Based on the latest design requirements proposed by the Beijing On-Line Isotope Separation (BISOL) project, a new ${\mathrm{Sn}}^{22+}$-based, 81.25 MHz CW radio frequency quadrupole (RFQ) with external bunching has been designed. This RFQ can accelerate ${\mathrm{Sn}}^{22+}$ to 0.5 MeV/u with an output longitudinal-normalized rms emittance of 0.20 keV/u·ns over a length of 5.6 m. The tolerance and error analysis results indicate that this RFQ can handle a wide range of non-ideal beams while maintaining relatively lower longitudinal emittance growth and higher transmission efficiency. To maintain the beam intensity, the RFQ will simultaneously accelerate three kinds of high-charge-state mixed ions (${}^{132}{\mathrm{Sn}}^{21+}$, ${}^{132}{\mathrm{Sn}}^{22+}$ and ${}^{132}{\mathrm{Sn}}^{23+}$), the simulation results given by Impact-T show that the RFQ can achieve high transmission of the mixed beam. Compared with the previous ${\mathrm{Sn}}^{21+}$-based internal bunching RFQ scheme, this RFQ has a shorter length and smaller output emittance, which is beneficial to the designs of subsequent Medium-energy Beam Transport (MEBT) and Drift Tube Linac (DTL). In electromagnetic design, a four-vane structure with 48 tuners and 16 $\pi$-mode stabilizers (PSLs) were chosen. The results of the multi-physics analysis show that the maximum temperature rise and the maximum deformation of the cavity are 13.6 K and 40.3 µm, respectively. The results simulated with CST Microwave Studio (CST) and HFSS software were consistent.

This paper presents the design of a compact injector linac for heavy ion medical therapy, based on a 200 MHz radio frequency quadrupole (RFQ) and two 200 MHz interdigit H-mode drift tube linac (IH-DTL) tanks using the KONUS beam dynamics scheme. In this system, the RFQ accelerates a ¹²C⁴⁺ beam from 10 keV/u to 0.6 MeV/u, after which it is further accelerated to 7 MeV/u by two IH-DTL tanks. The design specifically aims to improve transmission efficiency, minimize emittance growth, and reduce the overall system length. A three-bunching-cell structure at the RFQ exit provides longitudinal beam focusing, effectively eliminating the need for a separate re-buncher and significantly shortening the MEBT section. The linac achieves a compact total length of approximately 8.6 m and requires a total peak RF power of 774 kW. The peak surface field in the IH-DTL cavities reaches 2.0 Kp, while the effective shunt impedances are 110 MΩ/m and 126 MΩ/m for the first and second tanks, respectively. End-to-end simulations confirm high transmission and good beam quality at the linac exit, demonstrating the suitability of the design for synchrotron injection in medical applications.