Author: Chen, H.B.
Paper Title Page
TUPAB010 High-Gradient Breakdown Studies of X-Band Choke-Mode Structures 1322
SUSPSIK005   use link to see paper's listing under its alternate paper code  
 
  • X.W. Wu, H.B. Chen, J. Shi, H. Zha
    TUB, Beijing, People's Republic of China
  • T. Abe, T. Higo, S. Matsumoto
    KEK, Ibaraki, Japan
 
  As an alternative design for Compact Linear Collider (CLIC) main accelerating structures, X-band choke-mode damped structures had been studied for several years. However, the performance of choke-mode cavity under high power is still in lack of research. Two standing-wave single-cell choke-mode damped accelerating structures working at 11.424 GHz and one reference structure without choke were designed, manufactured, low-power measured, and tuned by accelerator group at Tsinghua University. High-power test had been done on them to study the breakdown phenomenon in high gradient and how the choke affects high-gradient properties. A max gradient of 75 MV/m were achieved by the choke-mode structure and the choke breakdown limited further increasing of the gradient. Inner surface inspection of the choke-mode structures indicates that the axial part of the choke limits the performance of the structure. Based on this observation, three new choke-mode structures were designed and being manufactured.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-TUPAB010  
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TUPAB070 S-Band Accelerating Structure for High-Gradient Upgrade of TTX 1485
 
  • D.Z. Cao, H.B. Chen, Y.-C. Du, W. Gai, W.-H. Huang, X.C. Meng, J. Shi, C.-X. Tang, X.W. Wu, H. Zha
    TUB, Beijing, People's Republic of China
 
  Thomson scattering x-ray source is an indispensable scientific X-ray imaging tool in various research fields. The 3-meter S-band linac in Tsinghua Thomson scatter-ing X-ray source (TTX) has been running at an accelerat-ing gradient of 15 MV/m so far. The gradient will be upgraded to 30MV/m by replacing the old structure with a shorter linac. Detailed optimization of the RF design of the new S-band linac structure is presented in this paper. Finally, further research on energy upgrade with X-band structures are also discussed.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-TUPAB070  
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TUPAB076 Design of an X-Band Photocathode for Tsinghua Thomson Scattering X-Ray Source 1497
 
  • L.Y. Zhou, H.B. Chen, Y.-C. Du, W. Gai, W.-H. Huang, J. Shi, C.-X. Tang, D. Wang, Z. Zhang, Z. Zhou
    TUB, Beijing, People's Republic of China
 
  Compared with S-band and C-band accelerating structures, X-band structures can run at a higher accelerating gradient and are more compact in size. In order to obtain higher electron energy in a limited space, a new X-band photo-injector operating at 11.424GHz has been designed at the Accelerator Laboratory of Tsinghua University. The structural design of the X-band photo-cathode RF gun and the accelerating structures as well as the beam dynamics simulation are presented in this paper, followed by the optimization of the structure based on the dispersed optimization experiment method(DOE). The results show that the design satisfies the working requirements with a small space occupied and a high beam quality.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-TUPAB076  
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THPAB031 Study of Beam Break Up in Irradiation Linacs 3767
SUSPSIK056   use link to see paper's listing under its alternate paper code  
 
  • X.C. Meng, H.B. Chen, W. Gai, J. Shi, S.X. Zheng
    TUB, Beijing, People's Republic of China
  • G.H. Li, J.S. Liu, Y.H. Liu
    NUCTECH, Beijing, People's Republic of China
  • F.H. de Sá
    LNLS, Campinas, Brazil
 
  Many recent experiments of the irradiation linacs produced at Tsinghua University indicate that beam power is limited by beam break up (BBU). Limits exist while the beam current or the pulse width is increased. In this paper, we illustrate the bream break up (BBU) phenomenon in the cases of both the 10MeV travelling-wave linac and 10MeV backward travelling-wave linac. The higher order modes in the linacs are analysed and the wake fields are calculated both with theoretical analysis and numerical simulation. Also, the beam dynamics is studied on the basis of the wakefield results to find a BBU threshold in these structures.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-THPAB031  
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THPIK054 The X-Band Pulse Compressor for Tsinghua Thomson Scattering X-Ray Source 4214
 
  • Y.L. Jiang, H.B. Chen, C. Cheng, W. Gai, J. Shi, P. Wang, X.W. Wu, H. Zha
    TUB, Beijing, People's Republic of China
 
  An X-band (11.424 GHz) high-power RF station is being built for Tsinghua Thomson scattering X-ray Source (TTX). The station aims to feed several X-band accelerating structures working at a high gradient of 80 MV/m. An X-band pulse compressor is designed to compress the RF pulse from 1.5 us to 100 ns and to generate more than 250 MW peak power from a 50MW klystron. This pulse compressor implements a resonate cavity housing the HE11-mode as the energy storage cavity, with a high quality factor Q of more than 105. The detailed design of the high-Q cavity as well as the dedicate couplers of this pulse compressor are present in this work.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-THPIK054  
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THPIK056 Design of a C-Band High-Efficiency Multi-Beam Klystron 4221
 
  • Z.N. Liu, H.B. Chen, M.M. Peng, J. Shi
    TUB, Beijing, People's Republic of China
 
  A multi-beam klystron at 5.712GHz has been designed with efficiency of more than 80%. It can generate a pulse with output power of about 3MW and a pulse length of 5 us. Space charge effect and large signal theory, which both increase the accuracy theoretically, are considered in the simulation. A series of parameters of cavities are given after optimizing, including the frequency, R/Q, Q0 and Qe. This paper describes the beam dynamics design of the klystron as well as a preliminary machenical design.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-THPIK056  
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THPIK057 Development of a High-Power X-Band RF Rotary Joint 4224
 
  • J. Liu, H.B. Chen, J. Shi, X.W. Wu, H. Zha
    TUB, Beijing, People's Republic of China
 
  RF rotary joints allow the independent movement be-tween the RF power source and the accelerating tube of a linear accelerator (linac). In this paper, the design of a compact X-band (9.3 GHz) high-power RF rotary joint is presented. Simulation results illustrate that RF parameters (the scattering matrix) of this rotary joint keep stable in the arbitrary rotation angle. The maximum return loss is about -30 dB, the insert loss is less than 0.11 dB, and the variance of output phase shifts is below 1 degree while rotating the joint. RF measurement on the rotary joint using Vector-Network analyser is also conducted and presented in this paper.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-THPIK057  
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THPIK058 Development of a S-Band Pulse Compressor 4227
 
  • P. Wang, H.B. Chen, C. Cheng, J. Shi, X.W. Wu, H. Zha
    TUB, Beijing, People's Republic of China
 
  We designed and fabricated a pulse compressor for S-band high power test stand at Tsinghua University. This pulse compressor is made up of a sphere resonant cavity with quality factor of 100000 and a rf polarizer. It has the ability of compressing a pulse from 3.6 us to 300 ns with the power gain of 7. A short description of the pulse compressor is presented, together with the RF design and low level RF measurement.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-THPIK058  
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THPIK059 Experimental Study on PM-AM Method in Pulse Compression System 4230
 
  • P. Wang, H.B. Chen, C. Cheng, M.M. Peng, J. Shi, X.W. Wu, J. Yang, H. Zha
    TUB, Beijing, People's Republic of China
 
  We experimentally demonstrate the PM-AM method (Phase Modulation to Amplitude Modulation) at the S-band high power test stand, which consists of two S-band klystrons, a SLED type pulse compressor and two high power stainless steel RF loads, in Tsinghua University. A LLRF (low level RF) system has been developed to modulate the phases of the two klystrons in real time such that pulse compressor could generate a flat output pulse. Experimental results presents that the efficiency of the pulse compression system is 45% and the power gain is 2.9.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-THPIK059  
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THPIK060 Tuning of an S-Band 10 MeV Traveling-Wave Accelerating Structure with a Non-uniform Section 4233
 
  • J.H. Shao, H.B. Chen, C. Gong, J. Shi, X.W. Wu, S.X. Zheng
    TUB, Beijing, People's Republic of China
 
  A tuning method of nonuniform travelling wave structures has been developed based on non-resonant perturbation measurement at Tsinghua University. The filed distribution is normalized with the shunt impedance and attenuation of each cell. Then their internal reflection can be deduced and corrected by cavity deforming. This method has been applied to an S-band 10 MeV travelling wave structure successfully. In this paper, the detailed tuning method and cold test results will be presented.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-THPIK060  
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