FRCAB —  Cavities 2   (05-Jul-19   10:30—12:40)
Chair: R.E. Laxdal, TRIUMF, Vancouver, Canada
Paper Title Page
HF-Free Bi-Polar Electropolishing for Application on Multi-Cell Elliptical Cavities  
  • H. Tian, M. Lester, J. Musson, H.L. Phillips, C.E. Reece
    JLab, Newport News, Virginia, USA
  • T.D. Hall, M.E. Inman, R. Radhakrishnan, E.J. Taylor
    Faraday Technology, Inc., Clayton, Ohio, USA
  Funding: Work supported by the U.S. Department of Energy, Office of Science, Office of Nuclear Physics under contract DE-AC0506OR23177
Pulse reversed electropolishing of niobium SRF cavities, using a dilute aqueous H2SO4 electrolyte without HF yields equivalent RF performance with traditional EP. A pulse reversed electropolishing (BPEP) system has been implemented at Jefferson lab, and applied to single cells, a 7-cell CEBAF C100 cavity, and to 9-cell TESLA-style cavities with upgraded pulse system recently. A systematically mechanistic characterization and understanding of the BPEP process through bench top coupons study and cavities directs a system and operational parameter refinement for BPEP. We present 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/industrialization of niobium cavity processing.
slides icon Slides FRCAB1 [4.394 MB]  
Electrodeposition of Copper Applied to the Manufacture of Seamless SRF Cavities  
  • G.J. Rosaz, S. Atieh, S. Calatroni, L.M.A. Ferreira, E. Garcia-Tabares Valdivieso, C. Garion, L. Lain-Amador, A.T. Perez Fontenla, K. Scibor, M. Taborelli, C. Yin Vallgren
    CERN, Geneva, Switzerland
  Nb thin film SRF cavities have demonstrated for many years their strong potential as being an alternative to bulk Nb cavities [1]. However most of the defects observed in the Nb layers originate from defects inherited from the substrate itself [2]. Two routes are used to manufacture Cu cavities. The first one consists of forming the half-cells independently by either spinning or electro-hydroforming. The latter are then joined together and to the cut-offs by electron-beam welding. The second one is a seamless process in which the cell is entirely spun around a mandrel and then electron-beam welded to the cut-offs. Both approaches require welding, leading to potential formation of porosities. We propose an innovative route, inspired from a technology used to form small diameter vacuum chambers [3]. The cavity is formed by electrodeposition of Cu on a sacrificial mandrel whose surface state will determine the inner cavity’s surface quality. The strength of the process relies on the total absence of welding. We present the values obtained for Young Modulus, Ultimate Tensile Stress, roughness and RRR on dedicated samples. We will then discuss the fabrication route of a real cavity.
[1] C. Benvenuti et al., IEEE transactions on applied superconductivity, vol. 9, No. 2, June 1999.
[2] G. Rosaz et al., FCC week 2018
[3] L. Lain Amador et al., JVSTA, vol. 36, pp. 021601, 2018.
slides icon Slides FRCAB2 [9.174 MB]  
FRCAB3 The Design of an Automated High-Pressure Rinsing System for SRF Cavity and the Outlook for Future Automated Cleanroom on Strings Assembly -1
  • 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]  
FRCAB4 Development of High Intensity, High Brightness, CW SRF Gun with Bi-Alkali Photocathode -1
  • T. Konomi, Y. Honda, E. Kako, Y. Kobayashi, S. Michizono, T. Miyajima, H. Sakai, K. Umemori, S. Yamaguchi
    KEK, Ibaraki, Japan
  Superconducting conduction electron guns 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. The surface cleaning methods and tools were developed by using KEK SRF gun cavity #1 and surface peak electric field reached to 75 MV/m without field emission. We will apply this technique to the SRF gun cavity #2 for beam operation. The gun cavity #2 equips the helium jacket, frequency tuner cathode position adjuster to operate the electron beam. The RF structure was designed based on the gun cavity #1. The cathode rod is made of Nb. The photocathode deposited on the cathode rod will be cool down to 2K to minimize thermal emittance. The fabrication of the gun cavity #2 and helium jacket were completed. 4 times vertical tests were carried out. We will report the vertical test results and preparation of the horizontal test.  
slides icon Slides FRCAB4 [10.826 MB]  
FRCAB5 Performance of 112 MHz SRF Gun at BNL -1
  • T. Xin, I. Ben-Zvi, J.C. Brutus, C. Folz, T. Hayes, P. Inacker, Y.C. Jing, D. Kayran, V. Litvinenko, J. Ma, G.J. Mahler, M. Mapes, K. Mernick, T.A. Miller, G. Narayan, P. Orfin, I. Pinayev, S. Polizzo, T. Rao, F. Severino, J. Skaritka, K.S. Smith, R. Than, J.E. Tuozzolo, E. Wang, G. Wang, Q. Wupresenter, B.P. Xiao, W. Xu, A. Zaltsman
    BNL, Upton, Long Island, New York, USA
  • S.A. Belomestnykh
    Fermilab, Batavia, Illinois, USA
  • C.H. Boulware, T.L. Grimm
    Niowave, Inc., Lansing, Michigan, USA
  • K. Mihara
    Stony Brook University, Stony Brook, USA
  • I. Petrushina
    SUNY SB, Stony Brook, New York, USA
  • K. Shih
    SBU, Stony Brook, New York, USA
  Funding: This work is funded by the DOE FOA (No. DE-FOA-0000632) and National Science Foundation (Award No. PHY-1415252).
A 112 MHz SRF electron photoinjector (gun) was developed at Brookhaven National Laboratory to produce high-brightness and high-bunch-charge bunches for the coherent electron cooling proof-of-principle experiment. The gun is designed to deliver electrons with a kinetic energy of up to 2 MeV. Electrons are generated by illuminating a high quantum efficiency (QE) K2CsSb photoemission layer with a green laser operating at a wavelength of 532 nm. The gun was able to generating 3 nC bunches at 1.7 MeV. The design goals, fabrication, performance and operational experience are reported here.
slides icon Slides FRCAB5 [3.984 MB]  
FRCAB6 The Effect of Helium Processing and Plasma Cleaning for Low Beta HWR Cavity -1
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  
FRCAB7 Plasma Processing to Reduce Field Emission in LCLS-II 1.3 GHz SRF Cavities -1
SUSP022   use link to see paper's listing under its alternate paper code  
TUP067   use link to see paper's listing under its alternate paper code  
  • B. Giaccone, J. Zasadzinski
    IIT, Chicago, Illinois, USA
  • P. Berrutti, B. Giaccone, A. Grassellino, M. Martinello
    Fermilab, Batavia, Illinois, USA
  • M. Doleans
    ORNL, Oak Ridge, Tennessee, USA
  • D. Gonnella, G. Lanza, M.C. Ross
    SLAC, Menlo Park, California, USA
  Plasma cleaning for LCLS-II 9-cell 1.3 GHz cavities is under study at Fermilab. Starting from ORNL method, we have developed a new technique for plasma ignition using HOMs. Plasma processing is being applied to contaminated and field emitting cavities, here are discussed the first results in terms of Q and radiation vs E measured before and after treatment. Further studies are ongoing to optimize plasma parameters and to acquire statistics on plasma cleaning effectiveness.  
slides icon Slides FRCAB7 [14.701 MB]  
FRCAB8 Systematic Studies of the Second Sound Method for Quench Detection of Superconducting Radio Frequency Cavities -1
  • L. Steder, B. Bein, D. Reschke
    DESY, Hamburg, Germany
  • W. Hillert
    University of Hamburg, Institut für Experimentalphysik, Hamburg, Germany
  DESY conducts R&D for SRF cavities, part of the manifold activities are vertical performance tests. Besides the determination of accelerating gradient and quality factor, additional sensors and diagnostic methods are used to obtain more information about the cavity behaviour and the test environment. The second sound system is a tool for spatially resolved quench detection via oscillating super-leak transducers, they record the second sound wave, generated by the quench of the superconducting Niobium. The mounting of the sensors was improved to reduce systematic uncertainties and results of a recent master thesis are presented in the following. Different reconstruction methods are used to determine the origin of the waves. The precision, constraints and limits of these are compared. To introduce an external reference and to qualify the different methods a calibration tool was used. It injects short heat pulses to resistors at exact known space and time coordinates. Results obtained by the different algorithms and measurements with the calibration tool are presented with an emphasis on the possible spatial resolution and the estimation of systematic uncertainties of the methods.  
slides icon Slides FRCAB8 [3.039 MB]