Keyword: niobium
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MO1A02 An Overview of Recent Developments in SRF Technology cavity, SRF, cryomodule, linac 6
 
  • R.E. Laxdal
    TRIUMF, Vancouver, Canada
 
  Superconducting Radio-Frequency (SRF) is now the technology of choice for both large and small linac projects. Several challenging projects are in progress or planned that are pushing SRF technology and/or are enabled by SRF technology. This paper gives an overview of the present status of the field.  
slides icon Slides MO1A02 [4.202 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-LINAC2018-MO1A02  
About • paper received ※ 16 September 2018      issue date ※ 18 January 2019  
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MOPO130 Magnetic Flux Generated by Thermal Current in CEBAF 5-Cell Cavity System cavity, cryomodule, experiment, operation 273
 
  • R.L. Geng
    JLab, Newport News, Virginia, USA
  • S.C. Huang
    IMP/CAS, Lanzhou, People’s Republic of China
 
  The unloaded quality factor Q0 of many 5-cell CEBAF cavities were lowered by a factor of ~2 from their vertical qualification testing to their beam operation in CEBAF tunnel. Causes of this Q0 degradation were studied previously, including a more recent one addressing static fluxes arising from magnetic components near a 5-cell cavity. This paper reports on a preliminary study of the dynamic fluxes generated by a thermal current. Such a thermal current arises from the Seebeck effect and flows in closed loops formed by a niobium cavity and its surrounding tuner rods and liquid helium vessel that are made of stainless-steel. The behaviors of magnetic fluxes in response to various thermal profiles on a 5-cell CEBAF cavity with integrated tuner rods were studied in a JLAB VTA dewar. An outcome of this study is a proposed cool-down procedure for eliminating the thermal current generated magnetic fluxes around 5-cell cavities placed in CEBAF tunnels. This procedure may be useful to improve cavity Q0 in a cost-effective manner, which in turn saves cryogenic expenditures for sustaining CEBAF operation.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-LINAC2018-MOPO130  
About • paper received ※ 01 September 2018      issue date ※ 18 January 2019  
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TU1A05 Seamless Quarter Wave Resonators for HIE ISOLDE cavity, ISOL, linac, cryomodule 292
 
  • W. Venturini Delsolaro, A. Miyazaki
    CERN, Geneva, Switzerland
 
  The HIE-ISOLDE post accelerator consists of 4 cryomodules with 5 niobium-coated Quarter Wave Reso-nators (QWR) each. The standard manufacturing tech-nique was to machine the inner and outer conductor sepa-rately, to shrink-fit the 2 pieces and to apply an electron beam welding at the interface. Due toμcracks, ob-served on some of the cavities around the welds, we took the decision to explore the possibility of a seamless de-sign. First cavities became available in late 2017 and were then cold-tested in the vertical cryostat. These seam-less coated quarter wave resonators have shown some of the highest Q-values of all HIE-ISOLDE cavities in the acceptance tests. Furthermore, we studied the cavity per-formance with different compensations of the earth mag-netic field and different temperature gradients upon cool down. These tests have demonstrated record-breaking RF surface fields for the Nb/Cu technology. This paper re-views the design and fabrication and reports on the cold tests results of seamless quarter wave resonators, and of possible future applications  
slides icon Slides TU1A05 [30.518 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-LINAC2018-TU1A05  
About • paper received ※ 11 September 2018      issue date ※ 18 January 2019  
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TUPO009 Heat Treatment for a Prototype Half-Wave Resonator Cavity cavity, vacuum, SRF, lattice 339
 
  • Y. Jung, B.H. Choi, J. Joo, H.C. Jung, H. Kim, J.W. Kim, Y. Kim, J. Lee, S. Lee
    IBS, Daejeon, Republic of Korea
 
  Heat treatment, 650C for 10hrs, was carried out to improve the performance of a half-wave resonator cavity. In this presentation, we report how the heat treatment was performed. X-ray diffraction analysis and residual gas analysis were performed to investigate the effect of the heat treatment on the cavity performance.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-LINAC2018-TUPO009  
About • paper received ※ 12 September 2018      issue date ※ 18 January 2019  
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TUPO031 Investigation of the Surface Resistance of Niobium Between 325 MHz and 1300 MHz Using a Coaxial Half-wave Cavity cavity, SRF, electromagnetic-fields, distributed 395
 
  • H. Park, S.U. De Silva, J.R. Delayen
    ODU, Norfolk, Virginia, USA
 
  The Center for Accelerator Science at Old Dominion University has built a half-wave coaxial cavity (*) to measure the surface resistance of niobium as a function of frequency, temperature, rf field, preparation techniques, over a wide range of frequencies of interest for particle accelerators. The characteristics of the half-wave coaxial cavity provide these information on a same surface. The preliminary results showed clearly the frequency dependence of residual surface resistance (**). After establishing baseline, we have conducted a study of low temperature baking effect on the surface resistance under controlled environment. This paper will describe the details of the test procedure, results and we will explore underlying physics of the phenomenon.
* H. Park et al., MOPB003, Proc. SRF2015, http://jacow.org/
** H. Park et al., THPB080, Proc. SRF2017, http://jacow.org/
 
slides icon Slides TUPO031 [0.966 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-LINAC2018-TUPO031  
About • paper received ※ 17 September 2018      issue date ※ 18 January 2019  
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TUPO032 First Test Results of Superconducting Twin Axis Cavity for ERL Applications cavity, HOM, SRF, linac 398
 
  • H. Park, S.U. De Silva, J.R. Delayen
    ODU, Norfolk, Virginia, USA
  • A. Hutton, F. Marhauser, H. Park
    JLab, Newport News, Virginia, USA
 
  Superconducting cavities with two beam pipes had been proposed in the past for energy recovery linac applications. The relatively complex geometry of those cavities presented a serious challenge for fabrication and surface processing. Main concerns have now been overcome with the production and successful RF testing of a new elliptical twin-axis cavity proposed by Jefferson Lab and optimized by the Center for Accelerator Science at Old Dominion University in the frame of a DoE accelerator stewardship program. The cavity design provides uniform accelerating or decelerating fields for both beams. This paper describes the cavity design, fabrication experience, and the first cold RF test results and explores potential applications especially for Jefferson Lab s EIC (JLEIC).  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-LINAC2018-TUPO032  
About • paper received ※ 20 September 2018      issue date ※ 18 January 2019  
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TUPO038 Several Experimental Phenomena of Sn Nucleation on Nb Surface Observed at IMP cavity, experiment, SRF, HOM 412
 
  • Z.Q. Yang, Y. He, F. Pan
    IMP/CAS, Lanzhou, People’s Republic of China
 
  Nucleation process is an important step that affects the quality of Nb3Sn films coated by vapor diffusion method. A uniform distribution of nucleation centers is essential to the uniformity of Nb3Sn films. In this paper we report several experimental phenomena on the Sn nucleation on Nb surface. Better nucleation in the downstream of the pumping direction was observed. Influence of SnCl2 partial pressure inhomogeneity was studied. Samples with higher SnCl2 partial pressure have denser nucleation, which means homogeneous SnCl2 pressure is a critical factor to the uniform nucleation. Less-nuclear zones, mainly distributed at cracks, grain boundaries and even some whole grain surfaces, were found on the surfaces of all samples. The less-nuclear zones may result in the low tin regions of the Nb3Sn cavities. The specific solution to the less-nuclear problem was proposed. These studies help to better understanding of the mechanism underlying the nucleation process and will be useful foundation for the follow-up Nb3Sn/Nb project at IMP.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-LINAC2018-TUPO038  
About • paper received ※ 12 September 2018      issue date ※ 18 January 2019  
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TUPO040 Tests of Multi-frequency Coaxial Resonators cavity, TRIUMF, rf-amplifier, controls 420
 
  • Z.Y. Yao, J.J. Keir, P. Kolb, A. Kong, R.E. Laxdal, B. Matheson, E. Thoeng, B.S. Waraich, Q. Zheng, V. Zvyagintsev
    TRIUMF, Vancouver, Canada
 
  A significant issue in low beta resonators is medium field Q-slope (MFQS) at 4K. To study the MFQS and the field dependence of surface resistance in low beta resonators, a quarter-wave resonator (QWR) and a half-wave resonator (HWR) were designed to be tested at integer harmonic frequencies of 200MHz, and up to 1.2GHz. A series of chemistry and heat treatments are proposed to these cavities. A systemic study on the surface resistance of the coaxial resonators associating with post-processing, RF field, and frequency is in progress. The cavities were designed and fabricated. The cold test results will be discussed in this paper.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-LINAC2018-TUPO040  
About • paper received ※ 17 September 2018      issue date ※ 18 January 2019  
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TUPO042 RF Results of Nb Coated SRF Accelerator Cavities via HiPIMS cavity, SRF, site, superconductivity 427
 
  • M.C. Burton, A.D. Palczewski, H.L. Phillips, C.E. Reece, A-M. Valente-Feliciano
    JLab, Newport News, Virginia, USA
  • R.A. Lukaszew
    The College of William and Mary, Williamsburg, Virginia, USA
 
  Funding: Work supported by the U.S. Department of Energy, Office of Science, Office of Nuclear Physics under contract DE-AC05-06OR23177.
Bulk Niobium (Nb) SRF (superconducting radio frequency) cavities are currently the preferred method for acceleration of charged particles at accelerator facilities around the world. Since the SRF phenomena occurs within a shallow depth of 40 nm (for Nb), a proposed option has been to deposit a superconducting Nb thin film on the interior of a cavity made of a suitable alternative material such as copper or aluminum. While this approach has been attempted in the past using DC magnetron sputtering (DCMS), such cavities have never performed at the bulk Nb level. However, new energetic condensation techniques for film deposition offer the opportunity to create suitably thick Nb films with improved density, microstructure and adhesion compared to traditional DCMS. One such technique that has been developed somewhat recently is ’High Power Impulse Magnetron Sputtering’ (HiPIMS). Here we report early results from various thin film coatings carried out on 1.3 GHz Cu Cavities, a 1.5 GHz Nb cavity and small Cu coupon samples coated at Jefferson Lab using HiPIMS.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-LINAC2018-TUPO042  
About • paper received ※ 12 September 2018      issue date ※ 18 January 2019  
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TUPO043 New Progress with HF-free Chemical Finishing for Nb SRF Cavities cavity, SRF, controls, ECR 431
 
  • H. Tian, J. Carroll, C.E. Reece, B. Straka
    JLab, Newport News, Virginia, USA
  • T.D. Hall, M.E. Inman, R. Radhakrishnan, E.J. Taylor
    Faraday Technology, Inc., Clayton, Ohio, USA
 
  Funding: This material is based upon work supported by the U.S. Department of Energy, Office of Science, Office of Nuclear Physics under contract DE-AC05-06OR23177.
Jefferson Lab has implemented a bipolar pulsed electropolishing system for final chemical processing of niobium SRF cavities. This FARADAYIC bi-polar electropolishing (BPEP) has been applied to single cells, a 7-cell CEBAF C100 cavity, and to 9-cell TESLA-style cavities.* As a mechanistic characterization of the process emerges, the critical role played by the local current density during each cathodic pulse is becoming clear. This influences system and operational parameter refinement. We present current process parameters, removal characterization, and rf performance of the processed cavities. This is the fruit of collaborative work between Jefferson Lab and Faraday Technology, Inc. directed toward the routine commercialization and industrialization of niobium cavity processing. We also present supporting data from controlled-parameter coupon studies
* E.J. Taylor, et al. "Electrochemical system and method for electropolishing superconductive radio frequency cavities" U.S. Pat. No. 9,006, 147 (& international counterparts) issued April 14, 2015.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-LINAC2018-TUPO043  
About • paper received ※ 12 September 2018      issue date ※ 18 January 2019  
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TUPO048 Study Progress of Pulse Laser Annealing for Niobium Film on Copper laser, ECR, experiment, cavity 438
 
  • Y. Yang, B.T. Li, X.Y. Lu, W.W. Tan, L. Xiao, D. Xie, D.Y. Yang
    PKU, Beijing, People’s Republic of China
 
  Funding: Work supported by Major Research Plan of National Natural Science Foundation of China (No. 91026001).
The recent studies of laser annealing on niobium films on copper are reported. Annealing is normally used to deal with the surface, reducing defects and even chang-ing the microstructure of the coating film. Short pulse laser can produce a sharp step temperature field on the film thickness scale (μm), which anneals the surface without substrate heated. The laser annealing experi-ments of niobium thin film sample have been carried out, and according to SEM and FIB results, Nb films melted and recrystallization occurred. Grains growing up can be observed while the power density of laser pulse in-creased.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-LINAC2018-TUPO048  
About • paper received ※ 12 September 2018      issue date ※ 18 January 2019  
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TUPO049 Nitrogen Doping Study With 1.3 GHz Single Cell Superconducting Cavities cavity, vacuum, accelerating-gradient, experiment 442
 
  • S. Chen, M. Chen, L.W. Feng, J.K. Hao, L. Lin, K.X. Liu, S.W. Quan, F. Wang, F. Zhu
    PKU, Beijing, People’s Republic of China
 
  Nitrogen doping studies were carried out at Peking University. A series of 1.3 GHz single cell cavities fabricated with OTIC large grain niobium material were annealed and doped in the furnace of Peking University, and electropolished by a simple EP device. Light doping recipe and heavy doping recipe are both adopted for comparison. The results and analysis are presented in this paper.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-LINAC2018-TUPO049  
About • paper received ※ 12 September 2018      issue date ※ 18 January 2019  
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TUPO054 Fundamental Studies of Impurity Doping in 1.3 GHz and Higher Frequency SRF Cavities cavity, SRF, radio-frequency, electron 458
 
  • J.T. Maniscalco, P.N. Koufalis, M. Liepe
    Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA
 
  As the demand for more powerful, more efficient, and smaller superconducting RF accelerators continues to increase, both impurity doping and high-frequency cavities (> 1.3 GHz) have become hot topics for fundamental research because of their potential to significantly decrease surface losses and cost respectively. In this report, we present recent experimental and theoretical results on undoped and nitrogen-doped high-frequency cavities and on alternative doping agents in traditional 1.3 GHz cavities, with a focus on understanding the fundamental science of impurity doping.  
slides icon Slides TUPO054 [1.956 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-LINAC2018-TUPO054  
About • paper received ※ 16 September 2018      issue date ※ 18 January 2019  
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TUPO059 Latest Results of Salt Based Bipolar Electro-polishing R&D at Cornell cavity, SRF, cathode, radio-frequency 473
 
  • M. Ge, F. Furuta, T. Gruber, J.J. Kaufman, M. Liepe, R.D. Porter
    Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA
  • T.D. Hall, R. Radhakrishnan, S.T. Snyder, E.J. Taylor
    Faraday Technology, Inc., Clayton, Ohio, USA
 
  Acid free electropolishing would be safer to use and friendlier to the environment. A collaboration, sup-ported by the DOE SBIR Phase-II program, between Faraday Technology Inc. and Cornell University focused on salt-based bipolar electropolishing (BEP). In this paper, we present the latest salt-based BEP results. The superconducting performance of a single-cell 1.3GHz cavity has been carefully analyzed, showing that salt-based BEP is promising, but still has large room for improvement.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-LINAC2018-TUPO059  
About • paper received ※ 19 September 2018      issue date ※ 18 January 2019  
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TUPO064 Pre-study of CEPC SRF Cavity cavity, SRF, cryomodule, collider 476
 
  • P. Sha
    Institute of High Energy Physics (IHEP), Chinese Academy of Sciences, Beijing, People’s Republic of China
  • J. Dai, C. Dong, H.F.S. Feisi, S. Jin, Z.Q. Li, B.Q. Liu, Z.H. Mi, J.Y. Zhai, X.Y. Zhang, H.J. Zheng
    IHEP, Beijing, People’s Republic of China
  • J.K. Hao, F. Wang
    PKU, Beijing, People’s Republic of China
 
  Funding: This study was supported by National Key Programme for S&T Research and Development (Grant NO.: 2016YFA0400400) and National Natural Science Foundation of China (Grant NO.:11505197).
CEPC will use 650 MHz cavities for the collider and 1.3 GHz cavities for the Booster. Each booster cryomod-ule contains eight 1.3 GHz 9-cell cavities, which is simi-lar as LCLS-II, E-XFEL and ILC. Each collider cryo-module contains six 650 MHz 2-cell cavities, which is totally new. Therefore, the pre-study mainly focuses on the 650 MHz 2-cell cavity. N-doping and vertical tests of 650 MHz 1-cell and 2-cell cavities have been carried out at IHEP, which have achieved good results. A test cryomodule, which consists of two 650 MHz 2-cell cavities, has also begun as the first step to the full-scale cryomodule.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-LINAC2018-TUPO064  
About • paper received ※ 31 August 2018      issue date ※ 18 January 2019  
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TUPO067 Study on New Removal Thickness Distribution Improvement Methods for Niobium 9-cell Cavity Vertical Electropolishing with Ninja Cathode cathode, cavity, experiment, status 488
 
  • K.N. Nii, V. Chouhan, Y.I. Ida, T.Y. Yamaguchi
    MGH, Hyogo-ken, Japan
  • H. Hayano, S. Kato, H. Monjushiro, T. Saeki, M. Sawabe
    KEK, Ibaraki, Japan
 
  Marui Galvanizing Co., Ltd. has been developing niobium 9-cell cavity vertical electropolishing (VEP) technologies with Ninja cathode in collaboration with KEK. Conventional 9-cell cavity VEP had a serious problem, which was asymmetry of removal thickness distribution. Usually removal thickness of upper side became larger than lower side in case of both in-cell and inter-cell. So far, as one solution, we proposed bubble diffusion prevention method and proved it was effective for uniform removal. This time, as other new solution, we tried cavity flip upside down and Ninja cathode masking VEP methods. In this article we will report the purpose, intention and VEP experiment result of these methods.  
poster icon Poster TUPO067 [0.858 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-LINAC2018-TUPO067  
About • paper received ※ 13 September 2018      issue date ※ 18 January 2019  
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TUPO068 Vertical Electropolishing of 1.3 GHz Niobium Nine-cell SRF Cavity: Bulk Removal and RF Performance cavity, cathode, target, SRF 491
 
  • V. Chouhan, Y.I. Ida, K.N. Nii, T.Y. Yamaguchi
    MGH, Hyogo-ken, Japan
  • H. Hayano, S. Kato, H. Monjushiro, T. Saeki, M. Sawabe
    KEK, Ibaraki, Japan
  • H. Ito
    Sokendai, Ibaraki, Japan
  • H. Oikawa
    Utsunomiya University, Utsunomiya, Japan
 
  Vertical electropolishing (VEP) technique have been successfully developed for 1.3 GHz niobium (Nb) single cell cavity to achieve a smooth surface with uniform removal and better RF performance as achieved after horizontal EP (HEP) process. VEP parameters for 1.3 GHz Nb nine-cell cavities are being studied using a nine-cell coupon cavity and our unique Ninja cathode. The investigated VEP parameters heretofore were applied on a 1.3 GHz Tesla shape nine-cell superconducting RF cavity for bulk removal of 100 µm followed by fine removal of 20 and 10 µm. The interior surface was found to be smooth and shiny after the VEP process. Our recently developed dual flow technique, in which the EP acid is flown separately in the Ninja cathode housing and cavity, yielded lower asymmetry in removal along the cavity length. The cavity was tested in a vertical cryostat after the final VEP process. The cavity achieved 28.3 MV/m at Q0 value of 6.7x109. The cavity performance was almost the same as in the baseline vertical test performed after the HEP process.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-LINAC2018-TUPO068  
About • paper received ※ 13 September 2018      issue date ※ 18 January 2019  
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TUPO069 Development of Vertical Electropolishing Facility for Nb 9-cell Cavity (2) cavity, controls, cathode, experiment 494
 
  • Y.I. Ida, V. Chouhan, K.N. Nii
    MGH, Hyogo-ken, Japan
  • T. Akabori, G.M. Mitoya, K. Miyano
    HKK, Morioka, Japan
  • Y. Anetai, F. Takahashi
    WING. Co.Ltd, Iwate-ken, Japan
  • H. Hayano, S. Kato, H. Monjushiro, T. Saeki, M. Sawabe
    KEK, Ibaraki, Japan
 
  In IPAC18 (Vancouver, Canada), we reported our first step of development of niobium 9-cell cavity vertical electropolishing (VEP) facility. In this article, we will report the method, system for uniform polishing for niobium 9-cell cavities and the current situation of our 9-cell cavity VEP facility (The result of polishing uniformity, vertical test will be presented in other posters of this conference). In addition, we will show the movie of experiments of VEP-3 with Ninja cathode. This facility aims not only for test VEP but also for mass production and long-time operation.  
poster icon Poster TUPO069 [0.316 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-LINAC2018-TUPO069  
About • paper received ※ 13 September 2018      issue date ※ 18 January 2019  
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TUPO072 First Trial of the In-situ Nitrogen Infusion at KEK cavity, vacuum, controls, SRF 503
 
  • T. Konomi, T. Dohmae, E. Kako, S. Michizono, H. Sakai, K. Umemori
    KEK, Ibaraki, Japan
  • T. Okada
    Sokendai, Ibaraki, Japan
 
  The nitrogen infusion is the new surface treatment technique for improving the RF loss and the maximum accelerating gradient of superconducting cavity. In this process, it is important to be carried out continuously both the 800 C annealing in vacuum and 120 C nitrogen infusion without exposure to the atmosphere. The annealing serves activation process by removing the oxide layer. The in-situ nitrogen infusion system was prepared to investigate whether nitrogen infusion effect or something changes happen in the case of applying nitrogen infusion technique without removing the oxide layer. It can only introduce nitrogen into a cavity during 120 C low temperature baking and transport a cavity to the vertical test system without exposure to the atmosphere. We tried to infuse nitrogen to a single cell by keeping 120 C and 48 hours with 3 Pa nitrogen. The cavity was annealed in another furnace and applied high pressure rinsing before nitrogen infusion. The vertical test result was same Q as the normal 120 C baking without nitrogen. It suggests that oxide layer prevents infusion of nitrogen. In this poster, the in-situ nitrogen infusion system and vertical test results will be reported.  
poster icon Poster TUPO072 [4.653 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-LINAC2018-TUPO072  
About • paper received ※ 12 September 2018      issue date ※ 18 January 2019  
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TUPO073 Niobium Sample Analysis for Nitrogen Infusion and Doping cavity, vacuum, injection, ECR 506
 
  • T. Konomi, E. Kako, S. Michizono, H. Sakai, K. Umemori
    KEK, Ibaraki, Japan
  • T. Nagata
    ULVAC, Inc., Tsukuba, Japan
  • T. Nojima
    Tohoku University, Sendai, Japan
 
  KEK has been investigating the better conditions of the heat treatment in nitrogen, which are called as nitrogen doping and nitrogen infusion. We have tried to understand the high gradient performance of the cavity from the analyses of samples which were prepared in the same conditions for the cavity. The main tools are D-SIMS for the depth profile of the elemental concentration, XPS for composition analysis and SQUID magnetometry for the critical DC magnetic field measurement. The difference in the depth profiles of the nitrogen, carbon and oxygen between the heat treatment conditions was observed in vacuum and furnace temperature of nitrogen infusion by D-SIMS and XPS. Such a difference correlates with the vortex penetration field measured by SQUID. In particular, that of nitrogen doping sample was greatly degraded, while that of nitrogen infusion sample was slightly improved. The tendency is similar to the RF high gradient test results. Details of the sample analysis are shown in this presentation.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-LINAC2018-TUPO073  
About • paper received ※ 18 September 2018      issue date ※ 18 January 2019  
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TUPO074 Design and Fabrication of KEK Superconducting RF Gun #2 cathode, gun, SRF, cavity 510
 
  • T. Konomi, Y. Honda, E. Kako, Y. Kobayashi, S. Michizono, T. Miyajima, H. Sakai, K. Umemori, S. Yamaguchi, M. Yamamoto
    KEK, Ibaraki, Japan
 
  Superconducting RF gun can realize high acceleration voltage and high beam repetition. KEK has been developing the 1.3 GHz elliptical type 1.5 cell superconducting RF gun to investigate fundamental performance. A surface cleaning method and tools are developed by using KEK SRFGUN #1 and high surface peak gradient 75 MV/m was achieved without field emission. SRFGUN #2 which equips the helium jacket and can be operated with electron beam was designed based on the SRFGUN #1. It can be operated with transmit type photocathode which include superconducting transparent material. The cathode plug is cooled by thermal conducting from the 2 K helium jacket and photocathode will be kept around 2K to maintain superconductivity. Bulk niobium photocathode plug and substrate will used for the fundamental performance test. In parallel, the photocathode deposition chamber for multi-alkali photocathode will be prepared.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-LINAC2018-TUPO074  
About • paper received ※ 12 September 2018      issue date ※ 18 January 2019  
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TH2A01 Nitrogen Infusion R&D for CW Operation at DESY cavity, FEL, operation, SRF 652
 
  • M. Wenskat, A.D. Dangwal Pandey, B. Foster, T.F. Keller, D. Reschke, J. Schaffran, S. Sievers, N. Walker, H. Weise
    DESY, Hamburg, Germany
  • C. Bate, G.D.L. Semione, A. Stierle
    University of Hamburg, Hamburg, Germany
  • B. Foster
    University of Hamburg, Institut für Experimentalphysik, Hamburg, Germany
  • B. Foster
    Oxford University, Physics Department, Oxford, Oxon, United Kingdom
 
  The European XFEL cw upgrade requires cavities with reduced surface resistance (high Q-values) for high duty-cycle while maintaining high accelerating gradient for short-pulse operation. To improve on European XFEL performance, a recently discovered treatment is investigated: The so called Nitrogen-infusion. The recent test results of the cavity based R&D and the progress of the relevant infrastructure is presented. The aim of this approach is to establish a stable, reproducible recipe and to identify all key parameters for this process. In parallel, advanced surface analyses, such as SEM/EDX, TEM, XPS, XRR, GIXRD and TOF-SIMS, of samples after in-situ treatment, cut-outs of cavities and samples treated together with cavities are done. The aim of this approach is to understand the underlying processes of the material evolution, resulting in the improved performance. Results of these analyses, their implications for the cavity R&D, and next steps are presented.  
slides icon Slides TH2A01 [4.597 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-LINAC2018-TH2A01  
About • paper received ※ 12 September 2018      issue date ※ 18 January 2019  
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THPO002 Investigation of SRF Elliptical Cavities Made by New Nb Materials in KEK cavity, superconducting-RF, linear-collider, collider 676
 
  • T. Dohmae, K. Umemori, Y. Watanabe, M. Yamanaka
    KEK, Ibaraki, Japan
  • T. Okada
    Sokendai, Ibaraki, Japan
 
  Cost reduction for cavity fabrication is currently main issue to realize international linear collider. Cavity fabrication facility (CFF) in KEK is approaching this issue from a point of view of materials for cavities. CFF had fabricated SRF elliptical cavities made by two types of niobium; one is high tantalum contained and low RRR (< 100) fine grain niobium, and the other is high tantalum contained and RRR < 300 large grain (LG) niobium. Former was melted two times (normally five times) which results RRR recovery up to around 300, and used for cell parts. Two 3-cell cavities were fabricated for each material respectively and vertical tested. One of these cavity made by LG achieved accelerator gradients of more than 40 MV/m. In this report, cavity materials and vertical test results are presented in detail.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-LINAC2018-THPO002  
About • paper received ※ 12 September 2018      issue date ※ 18 January 2019  
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THPO069 The Electromagnetic Optimization of TE-sample Host Cavity at IMP cavity, SRF, linac, electron 852
 
  • S.C. Huang, Y. He, T. Tan, S.X. Zhang
    IMP/CAS, Lanzhou, People’s Republic of China
 
  As a part of the research and development work of thin-film materials for superconducting radio frequency(SRF) application in future accelerators at IMP, a 3.9GHz TE sample host cavity is being developed for the purpose of characterizing the RF Property and the loss mechanism of thin-film materials, which operates in the TE011 mode and accommodates disk sample with 110mm diameter, theoretically, the maximum magnetic field on sample surface will go up to 100mT, the resolution of surface resistance on sample will below nOhm by using thermometry technique( T-Mapping). In this paper, the electromagnetic optimization result of TE-sample host cavity will be presented, and the design consideration of hook tip style coupler and T-mapping system are also discussed.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-LINAC2018-THPO069  
About • paper received ※ 12 September 2018      issue date ※ 18 January 2019  
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