Design Optimization of a High-Power Coupler for a Continuous-Wave Radio-Frequency Quadrupole Accelerator
Design Optimization of a High-Power Coupler for a Continuous-Wave Radio-Frequency Quadrupole Accelerator
Xiao, Mr. Wenhao 1Li, Ms. Xiaoxiao 2Jin, Ms. Xiaofeng 2zhang, Mr. Shenghu 2He, Prof. Yuan 何源 3Wang, Dr. Zhi-Jun 2Zhang, Mr. Zhouli 4Gao, Mr. Shilong 5Zhao, Ms. Yujuan 2Xin, Mr. Yuqi 6Li, Mr. Chenxing 2wang, Mr. ruoxu 2Xianbo, Mr. Xu 2dou, Dr. weiping 5Qin, Dr. Wei2
作者信息
- 1. Institute of Modern Physics Chinese Academy of Sciences;Lanzhou University
- 2. Institute of Modern Physics Chinese Academy of Sciences
- 3. Advanced Energy Science and Technology Guangdong Laboratory;Institute of Modern Physics Chinese Academy of Sciences;UCAS
- 4. UCAS
- 5. Institute of Modern Physics Chinese Academy of Sciences;UCAS
- 6. Advanced Energy Science and Technology Guangdong Laboratory
- 折叠
摘要
The Institute of Modern Physics (IMP) has developed a family of high-power couplers for continuous-wave (CW) radio-frequency quadrupole (RFQ) accelerators and bunchers. Two ceramic-window failures in 2026 exposed weaknesses in the existing designs. In February, a brazed window on the High Intensity Heavy-ion Accelerator Facility (HIAF) RFQ coupler operated for about 30 min while the medium-energy beam transport (MEBT) vacuum was degraded and the machine-protection interlocks had failed to trip; the pressure rose from 2.5×10⁻⁶ to 2.5×10⁻¹ Pa. Multipacting and arcing melted the Ag-Cu-Pd filler metal, and the resulting copper layer metallized the window, which subsequently cracked. In May, an O-ring-sealed window on the Accelerator-Based Medical Isotope Pharmaceutical R&D Platform (IP-SAFE) buncher failed by thermal runaway. Multipacting heat and Joule heating of the inner-conductor bolts softened the inner O-ring and cracked the window on its vacuum side. The weak links differ: filler-metal migration and inadequate machine protection at HIAF; insufficient multipacting suppression and heat removal at IP-SAFE. We describe a design strategy based on derating, process simplification, and multipacting suppression. The coupler power is reduced from 60 to 40 kW; the brazed joint is replaced by a Viton O-ring seal; the cooling circuit is reduced to two channels; and the window receives a titanium nitride (TiN) coating plus a periodic triangular texture. Electromagnetic simulations give S₁₁ = −45.5 dB at 81.25 MHz and a −30 dB bandwidth of about 4.35 MHz, with 41.5 W total radio-frequency (RF) loss at 40 kW. The two-channel cooling keeps the window at or below 25.7 °C and the whole coupler below 30 °C, while the maximum coupler temperature at 60 kW reaches about 32 °C. Particle-in-cell simulations show an average secondary electron yield (SEY) peak of 2.6 at 5–7 kW, falling to 1.22 at 60 kW; the triangular texture reduces the saturated electron population by about 31%. The design is expected to improve reliability, maintainability, and manufacturability without degrading RF transmission, and offers a practical route for upgrading the power-feeding systems of the China Initiative Accelerator Driven System (CiADS), HIAF, and similar facilities.
Abstract
The Institute of Modern Physics (IMP) has developed a family of high-power couplers for continuous-wave (CW) radio-frequency quadrupole (RFQ) accelerators and bunchers. Two ceramic-window failures in 2026 exposed weaknesses in the existing designs. In February, a brazed window on the High Intensity Heavy-ion Accelerator Facility (HIAF) RFQ coupler operated for about 30 min while the medium-energy beam transport (MEBT) vacuum was degraded and the machine-protection interlocks had failed to trip; the pressure rose from 2.510 to 2.510 Pa. Multipacting and arcing melted the Ag-Cu-Pd filler metal, and the resulting copper layer metallized the window, which subsequently cracked. In May, an O-ring-sealed window on the Accelerator-Based Medical Isotope Pharmaceutical R&D Platform (IP-SAFE) buncher failed by thermal runaway. Multipacting heat and Joule heating of the inner-conductor bolts softened the inner O-ring and cracked the window on its vacuum side. The weak links differ: filler-metal migration and inadequate machine protection at HIAF; insufficient multipacting suppression and heat removal at IP-SAFE. We describe a design strategy based on derating, process simplification, and multipacting suppression. The coupler power is reduced from 60 to 40 kW; the brazed joint is replaced by a Viton O-ring seal; the cooling circuit is reduced to two channels; and the window receives a titanium nitride (TiN) coating plus a periodic triangular texture. Electromagnetic simulations give S = 45.5 dB at 81.25 MHz and a 30 dB bandwidth of about 4.35 MHz, with 41.5 W total radio-frequency (RF) loss at 40 kW. The two-channel cooling keeps the window at or below 25.7 C and the whole coupler below 30 C, while the maximum coupler temperature at 60 kW reaches about 32 C. Particle-in-cell simulations show an average secondary electron yield (SEY) peak of 2.6 at 57 kW, falling to 1.22 at 60 kW; the triangular texture reduces the saturated electron population by about 31%. The design is expected to improve reliability, maintainability, and manufacturability without degrading RF transmission, and offers a practical route for upgrading the power-feeding systems of the China Initiative Accelerator Driven System (CiADS), HIAF, and similar facilities.关键词
High-power coupler/Ceramic window/Multipacting/O-ring seal/TiN coating/Multiphysics simulationKey words
High-powercoupler/Ceramicwindow/Multipacting/Multiphysics simulation引用本文复制引用
Xiao, Mr. Wenhao,Li, Ms. Xiaoxiao,Jin, Ms. Xiaofeng,zhang, Mr. Shenghu,He, Prof. Yuan 何源,Wang, Dr. Zhi-Jun,Zhang, Mr. Zhouli,Gao, Mr. Shilong,Zhao, Ms. Yujuan,Xin, Mr. Yuqi,Li, Mr. Chenxing,wang, Mr. ruoxu,Xianbo, Mr. Xu,dou, Dr. weiping,Qin, Dr. Wei.Design Optimization of a High-Power Coupler for a Continuous-Wave Radio-Frequency Quadrupole Accelerator[EB/OL].(2026-10-23)[2026-10-26].https://chinaxiv.org/abs/202610.00196.学科分类
真空电子技术
