Author: Li, C.L.
Paper Title Page
MOFAB4
Overview and SRF Requirements of the CiADS Project  
 
  • Y. He, Q. Chen, Z. Gao, H. Guo, G. Huang, Y.L. Huang, T.C. Jiang, C.L. Li, S.H. Liu, T. Tan, Y.Q. Wan, F.F. Wang, J.Q. Wu, W.M. Yue, B. Zhang, J.H. Zhang, S.H. Zhang, S.X. Zhang
    IMP/CAS, Lanzhou, People’s Republic of China
  • J.P. Dai, F.S. He, Z.Q. Li, W.M. Pan
    IHEP, Beijing, People’s Republic of China
  • T.C. Jiang
    University of Chinese Academy of Sciences, Beijing, People’s Republic of China
 
  Chinese initiative Accelerator Driven System started constructing in 2018. It consists a superconducting linac with 500 MeV and 5 mA; an LEB coolant fast reactor with 7.5 MW. The first beam coupling with reactor will be in 2024. The sc linac employed 5 families of superconducting resonators, two types of HWRs (β=0.1 and β=0.19), one type of double spokes (β=0.42) and two types of ellipticals (β=0.62 and β=0.82). The whole system will operate in 2 K. A space has been reserved for future upgrading to 1 GeV. As a demo of front-end of ADS, the CAFe (China ADS Front-end demo linac) has been developed and commissioned to verify the SRF techniques, high power CW beam and RAMI. 45 kW proton beam has been delivered to the dump and lasted more than 100 hours at the beginning of 2019. According to the operation experience, the challenge is the stability and performance of cavities under the heavy beam loading, some phenomenas have been observed. Up to now, the design of bulk Nb cavities have been finished and the prototype fabrication is on going. The techniques of Nb/Cu cavity and Nb3Sn are also developed in IMP for the future project of ADS.  
slides icon Slides MOFAB4 [12.465 MB]  
Export • reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)  
 
MOP003 Development of Nb3Sn Cavity Coating at IMP 21
 
  • Z.Q. Yang, H. Guo, Y. He, C.L. Li, Z.Q. Lin, M. Lu, T. Tan, P.R. Xiong, S.H. Zhang, S.X. Zhang
    IMP/CAS, Lanzhou, People’s Republic of China
 
  The A15 superconductor Nb3Sn is one of the most promising alternative materials to standard niobium for SRF applications. In this paper, we report our progress in the development of Nb3Sn cavity coating by vapor diffusion method at IMP. The evolutionary process of nucleation was analyzed. Influence of SnCl2 partial pressure inhomogeneity was studied. Less-nuclear zones were found on the surfaces of nucleation samples. The Nb3Sn film structure and composition were investigated and analyzed. In light of knowledge obtained above, the coating process was optimized. Finally, both 1.3 GHz and 650 MHz single cell cavities were coated and vertically tested both at 4 K and 2 K. Effect of low temperature baking (1000°C for 48 hs) on the RF performance of Nb3Sn cavity was studied. After baking, the Q drop in the low field region was eliminated and the Q in the intermediate field region was increased 8 times. The Q was 10 times larger than that of the Nb cavity at 4.2 K even in the case of the ambient field larger than 20 mGs. This study shows that the low temperature baking is an effective enrichment to the post treatment of the Nb3Sn cavity.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2019-MOP003  
About • paper received ※ 23 June 2019       paper accepted ※ 03 July 2019       issue date ※ 14 August 2019  
Export • reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)  
 
MOP073 The Study of High Power Couplers for CIADS 241
SUSP007   use link to see paper's listing under its alternate paper code  
 
  • Z.Q. Lin, Y. He, S.C. Huang, Y.L. Huang, T.C. Jiang, C.L. Li, Y.M. Li, M. Lu, F. Pan, T. Tan, R.X. Wang, Z. Xue, Z.Q. Yang, S.X. Zhang
    IMP/CAS, Lanzhou, People’s Republic of China
 
  High power couplers with high operation reliability are needed for the superconducting cavities used in the Linac of CiADS project at IMP. This paper will report two works on high power coupler. The DC bias structure of the coupler was optimized to suppress the multipacting effect, where the series resistors were introduced to the wire of the DC bias to reduce the field propagating along the DC bias’s wire. For the purpose of significantly decreasing the power needed to condition the coupler, we designed a new RF conditioning scheme, in which the coupler served as a standing wave resonator, and the positions of the crests and troughs of the wave were tunable. The details of the design mentioned above will be depicted.  
poster icon Poster MOP073 [14.677 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2019-MOP073  
About • paper received ※ 25 June 2019       paper accepted ※ 30 June 2019       issue date ※ 14 August 2019  
Export • reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)  
 
MOP085 The Destructive Effects to the RF Coupler by the Plasma Discharge 285
 
  • A.D. Wu, Q.W. Chu, H. Guo, Y. He, S.C. Huang, T.C. Jiang, C.L. Li, Z.Q. Lin, F. Pan, Y.K. Song, T. Tan, W.M. Yue, S.H. Zhang, H.W. Zhao
    IMP/CAS, Lanzhou, People’s Republic of China
 
  The low temperature RF plasma was proved an effec-tive method to clean the niobium surface and relieve the field emission effect for the SRF cavities. In the case of half-wave resonators, these cavities were usually powered via the fundamental coupler with the electric coupling. Thus, coupler antennas were fixed in the intense electric field region, and this region was where the plasma rou-tinely ignited. Therefore, the ceramic window of coupler taken the risk of breakdown under the sputtering of ions and heating loads that may be caused by the plasma drift and diffusion from the electric field region. In this paper, the plasma ignition for surface cleaning on the HWR cavity and its coupler was investigated, and the power transmission, temperature raising and vacuum degradation were tested to characterize the adverse impacts on the ceramic window. Finally, the solution was proposed to figure these issues.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2019-MOP085  
About • paper received ※ 22 June 2019       paper accepted ※ 02 July 2019       issue date ※ 14 August 2019  
Export • reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)  
 
TUP075 New Progress for Nb Sputtered 325 MHz QWR Cavities in IMP 621
 
  • F. Pan, H. Guo, Y. He, T.C. Jiang, C.L. Li, M. Lu, T. Tan
    IMP/CAS, Lanzhou, People’s Republic of China
 
  Comparing with bulk niobium cavities, the Nb/Cu cavities feature a much better stability at 4.5 K. Last year, two 325 MHz QWR copper cavities coated with biased DC diode sputterred Nb for CiADS has been accomplished at IMP. But vertical tests showed the cavities had low Q0 at 4 K. To solve the issue, a new coating system was designed and built. The sputtering target was redesigned and manufactured. The coating parameters were selected again and auxiliary heating was used to control the coating temperature in the process of sputtering. The power and Ar pressure during coating were also carefully selected. The paper covers resulting film characters, vertical tests with the evolution of the sputtering process, and improvements we made since last year.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2019-TUP075  
About • paper received ※ 22 June 2019       paper accepted ※ 14 August 2019       issue date ※ 14 August 2019  
Export • reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)  
 
THP064 The Cryostat Results of Carbon Contamination and Plasma Cleaning for the Field Emission on the SRF Cavity 1038
 
  • A.D. Wu, Q.W. Chu, H. Guo, Y. He, S.C. Huang, C.L. Li, F. Pan, Y.K. Song, T. Tan, P.R. Xiong, W.M. Yue, S.H. Zhang, H.W. Zhao
    IMP/CAS, Lanzhou, People’s Republic of China
 
  The field emission effect is the mainly limitation for the operating of SRF cavities in higher gradient with stability. In this paper, the experiments were performed to evaluate the impact of the carbon contaminants and plasma cleaning on the performance of SRF cavity. Contamination mechanism was classified into cryogenic adsorption with weak strength and chemical deposition with strong strength. For the weak strength condition, the methane was injected into the SRF cavity during vertical test to make a cryogenic adsorption layer on the inner surface of the cavity. The results revealed that the performance of SRF cavity degraded by methane physical adsorption, but the performance can be recovered by thermal cycle the cavity to 300K and pump methane out. For the strong strength condition, the chemical deposited dirty layer of carbon contamination was produced by using of Ar/CH4 mixed PECVD method, and the SRF cavity performance was deteriorated by the severe field emission. Finally, carbon deposited cavity was treated by the Ar/O2 plasma, and its results revealed that the field emission removed greatly and the gradient was increased.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2019-THP064  
About • paper received ※ 20 June 2019       paper accepted ※ 01 July 2019       issue date ※ 14 August 2019  
Export • reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)  
 
FRCAB3 The Design of an Automated High-Pressure Rinsing System for SRF Cavity and the Outlook for Future Automated Cleanroom on Strings Assembly 1216
 
  • H. Guo, Q.W. Chu, Y. He, C.L. Li, Y.K. Song, T. Tan, Z.M. You
    IMP/CAS, Lanzhou, People’s Republic of China
 
  High-pressure rinsing (HPR) and cavity assembly are two critical steps in cavity post-processing. Traditionally, high-pressure rinsing processing is based on ultra pure water system, pump, rinsing wand and simple-functional control system; cavity assembly processing is based on simple fixtures, wrenches, bolts and nuts. Beside the equipments, at least two operators are required in either of these two processing. Operators and their actions could bring mistakes and cause extra airborne particle contamination in cleanroom. To avoid the risk from labors, a robot has been introduced in IMP cleanroom for HPR assisting and assembly assisting. Labor cost and cavity RF test results are compared between the circumstances with and without robot assisting. In this work, an automated HPR system that has been designed and will be installed in IMP cleanroom will be presented. In addition, a future automated cleanroom on strings assembly will be discussed as well.  
slides icon Slides FRCAB3 [6.203 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2019-FRCAB3  
About • paper received ※ 03 July 2019       paper accepted ※ 12 July 2019       issue date ※ 14 August 2019  
Export • reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)  
 
FRCAB6 The Effect of Helium Processing and Plasma Cleaning for Low Beta HWR Cavity 1228
THP065   use link to see paper's listing under its alternate paper code  
 
  • S.C. Huang, Q.W. Chu, Y. He, C.L. Li, A.D. Wu, S.X. Zhang
    IMP/CAS, Lanzhou, People’s Republic of China
 
  The commissioning of the 25 MeV high power and high intensity proton Linac demo for CiADS showed that the performance of the SRF cavities was mainly limited by field emission inside the cavities. Therefore, the techniques of helium processing and reactive oxygen plasma cleaning have been developed to mitigate field emission issues. We performed an experiment with a low beta HWR cavity exposed to air directly and processed by helium and reactive oxygen. In this paper, the details of the experiment will be described, the efficiency of helium processing and plasma cleaning will be compared and discussed  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2019-FRCAB6  
About • paper received ※ 23 June 2019       paper accepted ※ 01 July 2019       issue date ※ 14 August 2019  
Export • reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)