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Development of a seven-cell S-band standing-wave RF-deflecting cavity for Tsinghua Thomson scattering X-ray source

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Nuclear Science and Techniques 2021年第4期32卷 20-29页

作者： Xian-Cai Lin Hao Zha Jia-Ru Shi Liu-Yuan Zhou Shuang Liu Jian Gao huai-bi chen Department of Engineering Physics Tsinghua UniversityBeijing 100084China Key Laboratory of Particle and Radiation Imaging(Tsinghua University) Ministry of EducationBeijing 100084China

A 2856-MHz,π-mode,seven-cell standingwave deflecting cavity was designed and fabricated for bunch length measurement in Tsinghua Thomson scattering X-ray source(TTX)*** cavity was installed in the TTX and provided a deflecting voltage of 4.2 MV with an input power of 2.5 *** length diagnoses of electron beams with energies up to 39 MeV have been *** this article,the RF design of the cavity using HFSS,fabrication,and RF test processes are ***-power operation with accelerated beams and calibration of the deflecting voltage are also presented.

关键词： Deflecting RF cavity Standing wave Bunchlength measurement Thomson X-ray source

A compact X-band backward traveling-wave accelerating structure

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Nuclear Science and Techniques 2024年第5期35卷 13-29页

作者： Xian-Cai Lin Hao Zha Jia-Ru Shi Qiang Gao Fang-Jun Hu Qing-Zhu Li huai-bi chen Department of Engineering Physics Tsinghua UniversityBeijing 100084China Key Laboratory of Particle and Radiation Imaging(Tsinghua University) Ministry of EducationBeijing 100084China

Very high-energy electrons(VHEEs)are potential candidates for FLASH radiotherapy for deep-seated *** proposed a compact VHEE facility based on an X-band high-gradient high-power *** this study,we investigated and realized the first X-band backward traveling-wave(BTW)accelerating structure as the buncher for a VHEE facility.A method for calculating the parameters of single cell from the field distribution was introduced to simplify the design of the BTW ***-domain circuit equations were applied to calculate the transient beam parameters of the buncher in the unsteady state.A prototype of the BTW structure with a thermionic cathode-diode electron gun was designed,fabricated,and tested at high power at the Tsinghua X-band high-power test *** structure successfully operated with 5-MW microwave pulses from the pulse compressor and outputted electron bunches with an energy of 8 MeV and a pulsed current of 108 mA.

关键词： Backward traveling-wave accelerating structure Equivalent circuit model High-power test Very high-energy electron radiotherapy

Design,fabrication,and testing of an X-band 9-MeV standing-wave electron linear accelerator

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Nuclear Science and Techniques 2023年第7期34卷 219-230页

作者： Jian Gao Hao Zha Jia-Ru Shi Qiang Gao Xian-Cai Lin Fang-Jun Hu Qing-Zhu Li huai-bi chen Department of Engineering Physics Tsinghua UniversityBeijing 100084China Key Laboratory of Particle and Radiation Imaging(Tsinghua University) Ministry of EducationBeijing 100084China

In this study,an X-band standing-wave biperiodic linear accelerator was developed for medical radiotherapy that can accel-erate electrons to 9 MeV using a 2.4-MW *** structure works atπ/2 mode and adopts magnetic coupling between cavities,generating the appropriate adjacent mode separation of 10 *** accelerator is less than 600-mm long and constitutes four bunching cells and 29 normal *** optimizations,full-scale radiofrequency(RF)simulations,and beam dynamics calculations were *** accelerator was fabricated and examined using a low-power RF *** cold test results showed a good agreement with the simulation and actual measurement *** the high-power RF test,the output beam current,energy spectrum,capture ratio,and spot size at the accelerator exit were *** the input power of 2.4 MW,the pulse current was 100 mA,and the output spot root-mean-square radius was approximately 0.5 *** output kinetic energy was 9.04 MeV with the spectral FWHM of 3.5%,demonstrating the good performance of this accelerator.

关键词： Standing-wave accelerating structure RF analysis Thermal DC gun Low-power RF test High-power experiment

A non-invasive diagnostic method of cavity detuning based on a convolutional neural network

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Nuclear Science and Techniques 2022年第7期33卷 25-35页

作者： Liu-Yuan Zhou Hao Zha Jia-Ru Shi Jia-Qi Qiu Chuan-Jing Wang Yun-Sheng Han huai-bi chen Department of Engineering Physics Tsinghua UniversityBeijing100084China Key Laboratory of Particle and Radiation Imaging Tsinghua UniversityBeijing100084China

As modern accelerator technologies advance toward more compact sizes,conventional invasive diagnostic methods of cavity detuning introduce negligible interference in measurements and run the risk of harming structural *** overcome these difficulties,this study developed a non-invasive diagnostic method using knowledge of scattering parameters with a convolutional neural network and the interior point *** construction and training of the neural network led to remarkable results on three typical acceleration structures:a 13-cell S-band standing-wave linac,a 12-cell X-band traveling-wave linac,and a 3-cell X-band RF *** trained networks significantly reduced the burden of the tuning process,freed researchers from tedious tuning tasks,and provided a new perspective for the tuning of side-coupling,semi-enclosed,and total-enclosed structures.

关键词： Cavity detuning Convolutional neural network Equivalent circuit

Analytic RF design of a linear accelerator with a SLED-Ⅰ type RF pulse compressor

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Nuclear Science and Techniques 2020年第11期31卷 12-22页

作者： Jia-Yang Liu Jia-Ru Shi Hao Zha Alexej Grudiev Ping Wang Ying-Chao Du huai-bi chen Department of Engineering Physics Tsinghua UniversityBeijing 100084China Key Laboratory of Particle and Radiation Imaging(Tsinghua University) Ministry of EducationBeijing 100084China European Organization for Nuclear Research(CERN) 1211 GenevaSwitzerland

This study presents the RF design of a linear accelerator(linac)operated in single-bunch *** accelerator is powered by a compressed RF pulse produced from a SLED-I type RF pulse *** compressed RF pulse has an unflattened shape with a gradient distribution which varies over the structure *** analytical study to optimize the accelerating structure together with the RF pulse compressor is *** optimization aims to maximize the efficiency by minimizing the required RF power from the generator for a given average accelerating *** study shows that,owing to the compressed RF pulse shape,the constant-impedance structure has a similar efficiency to the optimal structure using varying iris *** constant-impedance structure is easily fabricated and is favorable for the design of a linac with a pulse *** utilize these findings to optimize the RF design of a X-band linac using the constant-impedance accelerating structure for the Tsinghua Thomson X-ray source facility.

关键词： X-band linac High gradient structure RF pulse compressor Thomson X-ray source Single-bunch mode

Laser-RF synchronization based on digital phase detector

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Nuclear Science and Techniques 2017年第4期28卷 97-102页

作者： Jin Yang Ying-Chao Du Li-Xin Yan Gang Huang Qiang Du Yi-Lun Xu Wen-Hui Huang huai-bi chen Department of Engineering Physics Tsinghua UniversityBeijing 100084 China Key Laboratory of Particle and Radiation Imaging (Tsinghua University) Ministry of Education Beijing 100084 China Lawrence Berkeley National Laboratory BerkeleyCA 94720 USA

Laser oscillator synchronization with RF reference signal is ultra-important for a modern light source based on the *** Tsinghua Thomson scattering X-ray source,we have synchronized the mode-locked laser oscillator to RF reference signal with 48.2 fs RMS relative *** fundamental and harmonic signals derived from photo diode detection are used for laser-RF synchronization in our *** fundamental signal is for coarse laser-RF synchronization and multiple laser oscillator *** harmonic signal is for high precise phase *** digital phase detector is implemented in the synchronization scheme for less noise,replacing the mixing to DC phase detection *** digital processing algorithm for synchronization is commonly used in low-level RF control *** order to test the phase locking loop logic without damaging the real laser oscillator,a laser oscillator emulator was developed for phase *** paper will report the laser-RF synchronization scheme and its *** laser oscillator emulator system will also be introduced here.

关键词： Laser oscillator Synchronization RF LLRF Emulator

Design, fabrication, and testing of low-group-velocity S-band traveling-wave accelerating structure

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Nuclear Science and Techniques 2022年第11期33卷 133-143页

作者： Xian-Cai Lin Hao Zha Jia-Ru Shi Liu-Yuan Zhou Yi-Fan Liang Jian Gao Qiang Gao huai-bi chen Chuan-Xiang Tang Department of Engineering Physics Tsinghua UniversityBeijing 100084China Key Laboratory of Particle and Radiation Imaging(Tsinghua University) Ministry of EducationBeijing 100084China

To implement the Tsinghua Thomson Scattering X-ray Source upgrade plan and the Very Compact Inverse Compton Scattering Gamma-ray Source (VIGAS) program, a new 1.5-m traveling-wave accelerating structure was designed to replace the old 3-m SLAC-type structure with the aim of increasing the accelerating gradient from15 to 30 MV/m. The new type of structure works in the 3π/4 mode with a comparatively low group velocity varying from 0.007c to 0.003c to increase the accelerating gradient at a given power. An elliptical iris was employed to reduce the surface field enhancement. The filling process of the low-group-velocity structure was analyzed using a circuit model. After fabrication, the structure was precisely tuned using the non-contact tuning method, followed by detailed low-power radiofrequency measurements. The structure was first installed and utilized at a beamline for the terahertz experiment at Tsinghua University. After 120 h of conditioning, it is now operating at a gradient of 24.2 MV/m and a 20.7-MW input power, with the klystron operating at its full power. It is expected to generate an accelerating gradient of 30 MV/m when the klystron power is upgraded to 30 MW in the near future.

关键词： Traveling-wave accelerating structure Cavity optimization Tuning method High-power test

Fabrication,tuning,and high-gradient testing of an X-band traveling-wave accelerating structure for VIGAS

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Nuclear Science and Techniques 2022年第8期33卷 77-88页

作者： Xian-Cai Lin Hao Zha Jia-Ru Shi Qiang Gao Jia-Yang Liu Liu-Yuan Zhou Jian Gao huai-bi chen Chuan-Xiang Tang Department of Engineering Physics Tsinghua UniversityBeijing 100084China Key Laboratory of Particle and Radiation Imaging(Tsinghua University) Ministry of EducationBeijing 100084China

X-band high-gradient linear accelerators are a challenging and attractive technology for compact electron linear-accelerator *** Very Compact Inverse Compton Scattering Gamma-ray Source(VIGAS)program at Tsinghua University will utilize X-band high-gradient accelerating structures to boost the electron beam from 50 to 350 MeV over a short distance.A constant-impedance traveling-wave structure consisting of 72 cells working in the 2π/3 mode was designed and fabricated for this *** tuning and detailed measurements were successfully applied to the *** 180 h of conditioning in the Tsinghua high-power test stand,the structure reached a target gradient of 80 MV/*** breakdown rate versus gradient of this structure was measured and analyzed.

关键词： Traveling-wave accelerating structure X-band high gradient Tuning method High-power test

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 *** 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 *** thus concluded that the high-gradient two-half linear accelerator is cost-effective,especially in high-frequency RF linear ***,we suggest that silverbased alloy brazing can further reduce costs.

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