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Conceptual design of a 714-MHz RFQ for compact proton injectors and development of a new tuning algorithm on its aluminium prototype

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Nuclear Science and Techniques 2024年第1期35卷 45-58页

作者： Yi-Xing Lu Wen-Cheng Fang Yu-Sen Guo Zhen-Tang Zhao Shanghai Institute of Applied Physics Chinese Academy of Sciences Shanghai 201800China University of Chinese Academy of Sciences Beijing 101408China Shanghai Advanced Research Institute Chinese Academy of Sciences Shanghai 201204China Shanghai Key Laboratory of Cryogenics&Superconducting RF Technology Shanghai 201800China ShanghaiTech University Shanghai 201210China

Radio frequency quadrupoles(RFQs),which are crucial components of proton injectors,significantly affect the performance of proton accelerator facilities.An RFQ with a high frequency of 714 MHz dedicated to compact proton injectors for medi-cal applications is designed in this study.The RFQ is designed to accelerate proton beams from 50 keV to 4 MeV within a short length of 2 m and can be matched closely with the downstream drift tube linac to capture more particles through a preliminary optimization.To develop an advanced RFQ,challenging techniques,including fabrication and tuning method,must be evaluated and verified using a prototype.An aluminium prototype is derived from the conceptual design of the RFQ and then redesigned to confirm the radio frequency performance,fabrication procedure,and feasibility of the tuning algorithm.Eventually,a new tuning algorithm based on the response matrix and least-squares method is developed,which yields favorable results based on the prototype,i.e.,the errors of the dipole and quadrupole components reduced to a low level after several tuning iterations.Benefiting from the conceptual design and techniques obtained from the prototype,the formal mechanical design of the 2-m RFQ is ready for the next manufacturing step.

关键词： Compact proton injector RFQ IH-DTL high gradient Tuning

Development and high-gradient test of a two-half accelerator structure

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Nuclear Science and Techniques 2021年第6期32卷 54-62页

作者： Mao-Mao Peng Jia-Ru Shi Hao Zha Xian-Cai Lin Ze-Ning Liu Yu-Liang Jiang Jian Gao Liu-Yuan Zhou Fo-Cheng Liu Xiang-Cong Meng Huai-Bi Chen Department of Engineering Physics Tsinghua UniversityBeijing 100084China Key Laboratory of Particle and Radiation Imaging Tsinghua UniversityMinistry of EducationBeijing 100084China

This paper reports on the design,fabrication,RF measurement,and high-power test of a prototype accelerator—such as 11.424 GHz with 12 cells—and a traveling wave of two halves.It was found that the unloaded gradient reached 103 MV/m during the high-power test and the measured breakdown rate,after 3.17×10^(7) pulses,was 1.62×10^(-4)/pulse/m at 94 MV/m and a 90 ns pulse length.We thus concluded that the high-gradient two-half linear accelerator is cost-effective,especially in high-frequency RF linear acceleration.Finally,we suggest that silverbased alloy brazing can further reduce costs.

关键词： Two-half structure Silver-based alloy brazing Low cost high gradient

Design,fabrication,and cold test of an S-band high-gradient accelerating structure for compact proton therapy facility

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Nuclear Science and Techniques 2021年第4期32卷 38-48页

作者： Yu Zhang Wen-Cheng Fang Xiao-Xia Huang Jian-Hao Tan Cheng Wang Chao-Peng Wang Zhen-Tang Zhao Shanghai Institute of Applied Physics Chinese Academy of SciencesShanghai 201800China University of Chinese Academy of Sciences Beijing 100049China ShanghaiTech University Shanghai 201210China Shanghai Advanced Research Institute Chinese Academy of SciencesShanghai 201204China

An S-band high-gradient accelerating structure is designed for a proton therapy linear accelerator(linac)to accommodate the new development of compact,singleroom facilities and ultra-high dose rate(FLASH)radiotherapy.To optimize the design,an efficient optimization scheme is applied to improve the simulation efficiency.An S-band accelerating structure with 2856 MHz is designed with a low beta of 0.38,which is a difficult structure to achieve for a linac accelerating proton particles from 70 to 250 MeV,as a high gradient up to 50 MV/m is required.A special design involving a dual-feed coupler eliminates the dipole field effect.This paper presents all the details pertaining to the design,fabrication,and cold test results of the S-band high-gradient accelerating structure.

关键词： S-band high gradient Accelerating structure Compact Single-room facility Dual-feed coupler Cold test

Design and preliminary test of the LLRF in C band high-gradient test facility for SXFEL

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Nuclear Science and Techniques 2020年第10期31卷 43-54页

作者： Cheng-Cheng Xiao Jun-Qiang Zhang Jian-Hao Tan Wen-Cheng Fang Shanghai Advanced Research Institute Chinese Academy of SciencesShanghai 201210China

This paper describes the design and preliminary test of the low-level radio frequency(LLRF)part of the C band high-gradient test facility for the Shanghai Soft X-ray Free-Electron Laser(SXFEL)-Linear Accelerator(LINAC).Before installation,the accelerating structures should be tested and conditioned.During the conditioning process,breakdown detection is needed to protect the accelerating structures and klystron from damage.The PCI extensions for instrumentation-based LLRF system and auto-conditioning algorithm are designed and applied in the LLRF part of the C band high-gradient test facility.Three C band accelerating structures and 1 pulse compressor have completed conditioning and were installed in the SXFEL-LINAC.

关键词： Accelerating structure high gradient C band Breakdown LLRF Conditioning

INCIPIENT MOTION OF COARSE PARTICLES IN high gradient RIVERS

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International Journal of Sediment Research 2006年第3期21卷 220-229页

作者： Shengfa YANG1, Jiang HU2 and Xingkui WANG31 Assoc. Prof., Department of River and Ocean, Chongqing Jiaotong University, and Department of Hydraulic Engineering, Tsinghua University. Chongqing, 400074, China. 2 Instructor, Department of River and Ocean, Chongqing Jiaotong University. Chongqing, 400074, China. 3 Prof., Department of Hydraulic Engineering, Tsinghua University, Beijing 100084, China. Department of River and Ocean Chongqing Jiaotong University and Department of Hydraulic Engineering Tsinghua University. Chongqing 400074 China Department of River and Ocean Chongqing Jiaotong University. Chongqing 400074 China Department of Hydraulic Engineering Tsinghua University Beijing 100084 China

In Northwest China, there are many inland rivers that are characterized by high a gradient, coarse particles, a thick pebble and gravel layer, and small discharge and shallow water depth during the flood season. In these rivers, the motion of coarse particles has an important influence on the construction of various structures related to these rivers. In this study, the law of the motion of coarse particles is investigated in high gradient rivers. First, according to the rolling mode of particle motion, the forces acting on coarse particles were analyzed, and a formula was deduced to represent the incipient drag force for uniform coarse particles in a high gradient river. The flow velocity near the river bed, resistance coefficient, and weight of a coarse particle were taken into account to obtain the formula, which indicated that the incipient drag force is not related to the sediment Reynolds number, but closely related to the Froude number, which was also true for the Maxwell formula. Next, after comparing the various criteria for incipient motion of sediment, experiments were done to obtain data and determine the incipient motion of coarse particles. Based on the experiments, it was concluded that the motion type of “embedded” coarse material belongs to the motion of contact load, and the nondimensional unit-width sediment transport rate, which was put forward by Taylor in 1971, was chosen as the criterion in this study. Finally, based on the experimental data, the drag force formula was calibrated. The computed drag force agreed well with the measured values. Moreover, the formula derived in this study was compared with the Maxwell formula, another formula to study the incipient motion of particles in step-shaped mountainous rivers. The comparison indicates that the slope is the key factor in the two formulas, and the weight is an important force on the incipient motion of coarse particles in the current formula, but not in the Maxwell formula.

关键词： River bed high gradient Coarse particle Incipient motion formula Froude number

Some aspects in accelerator structure studies at SLAC

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Chinese Physics C 2009年第S2期33卷 96-101页

作者：王聚文 SLAC Menlo Park CA 94025

Recent progress in the accelerator structure studies at SLAC is reported. This paper covers the room temperature accelerator structures for the ILC e+/e- sources; RF structures for some photon science projects including RF deffectors and the LCLS RF gun; the high gradient accelerator R&D in a global CLIC collaboration for the future multi-TeV linear colliders.

关键词： e+ sources e- sources RF deffector RF gun light source linear collider high gradient

Semi-analytic Solution of Steady Temperature Fields During Thin Plate Welding

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Chinese Journal of Aeronautics 2006年第B12期19卷 248-251页

作者： DAI Yao TAN Wei SUN Qi SUN Chang-qing Department of Mechanical Engineering Armored Force Engineering College Beijing 100072 China Department of Materials Science and Engineering Armored Force Engineering College Beijing 100072 China

Usually, it is very difficult to find out an analytical solution to thermal conduction problems during high temperature welding. Therefore, as an important numerical approach, the method of lines （MOLs） is introduced to solve the temperature field characterized by high gradients. The basic idea of the method is to semi-discretize the governing equation of the problem into a system of ordinary differential equations （ODEs） defined on discrete lines by means of the finite difference method, by which the thermal boundary condition with high gradients are directly embodied in formulation. Thus the temperature field can be obtained by solving the ODEs. As a numerical example, the variation of an axisymmetrical temperature field along the plate thickness can be obtained.

关键词： steady temperature field method of lines thin plate welding semi-analytic solution high gradient

Beam dynamics design for uranium drift tube linear accelerator

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Chinese Physics C 2014年第7期38卷 97-101页

作者：窦为平何源陆元荣 Institute of Modern Physics China Academy of Sciences University of Chinese Academy of Sciences State Key Lab of Nuclear Physics and Technology Peking University

KONUS beam dynamics design of uranium whose current is 5.0 emA, is accelerated from injection DTL with LORASR code is presented. The 238U34＋ beam, energy of 0.35 MeV/u to output energy of 1.30 MeV/u by IH-DTL operated at 81.25 MHz in HIAF project at IMP of CAS. It achieves a transmission efficiency of 94.95% with a cavity length of 267.8 cm. The optimization aims are the reduction of emittance growth, beam loss and project costs. Because of the requirements of CW mode operation, the designed average acceleration gradient is about 2.48 MV/m. The maximum axial field is 10.2 MV/m, meanwhile the Kilpatrick breakdown field is 10.56 MV/m at 81.25 MHz.

关键词： drift tube linear accelerator beam dynamics high gradient continuous wave

Study of a magnetic alloy-loaded RF cavity for bunch compression at the CSR

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Chinese Physics C 2010年第12期34卷 1879-1882页

作者：殷达钰刘勇夏佳文李朋赵永涛杨磊齐新 Institute of Modern Physics Chinese Academy of Sciences Graduate University of Chinese Academy of Sciences

The Heavy Ion Research Facility and Cooling Storage Ring（HIRFL-CSR）accelerator in Lanzhou offers a unique possibility for the generation of high density and short pulse heavy ion beams by non-adiabatic bunch compression longitudinally,which is implemented by a fast jump of the RF-voltage amplitude.For this purpose,an RF cavity with high electric field gradient loaded with Magnetic Alloy cores has been developed.The results show that the resonant frequency range of the single-gap RF cavity is from 1.13 MHz to 1.42 MHz,and a maximum RF voltage of 40 kV with a total length of 100 cm can be obtained,which can be used to compress heavy ion beams of 238U72＋ with 250 MeV/u from the initial bunch length of 200 ns to 50 ns with the coaction of the two single-gap RF cavity mentioned above.

关键词： magnetic alloy high permeability bunch compression high gradient broadband cavity