Author: Reece, C.E.
Paper Title Page
SUPB001 Analyzing Surface Roughness Dependence of Linear RF Losses 1
 
  • C. Xu, M.J. Kelley
    The College of William and Mary, Williamsburg, USA
  • C.E. Reece
    JLAB, Newport News, Virginia, USA
 
  Funding: Authored by Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC05-06OR23177.
Topographic structure on Superconductivity Radio Frequency (SRF) surfaces can contribute additional cavity RF losses describable in terms of surface RF reflectivity and absorption indices of wave scattering theory. At isotropic homogeneous extent, Power Spectrum Density (PSD) of roughness is introduced and quantifies the random surface topographic structure. PSD obtained from different surface treatments of niobium, such as Buffered Chemical Polishing (BCP), Electropolishing (EP), Nano-Mechanical Polishing (NMP) and Barrel Centrifugal Polishing (CBP) are compared. A perturbation model is utilized to calculate the additional rough surface RF losses based on PSD statistical analysis. This model will not consider that superconductor becomes normal conducting at fields higher than transition field. One can calculate the RF power dissipation ratio between rough surface and ideal smooth surface within this field range from linear loss mechanisms.
 
 
MOPB018 Analyzing Surface Roughness Dependence of Linear RF Losses 210
 
  • C. Xu
    The College of William and Mary, Williamsburg, USA
  • M.J. Kelley, C.E. Reece
    JLAB, Newport News, Virginia, USA
 
  Funding: Authored by Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC05-06OR23177.
Topographic structure on Superconductivity Radio Frequency (SRF) surfaces can contribute additional cavity RF losses describable in terms of surface RF reflectivity and absorption indices of wave scattering theory. At isotropic homogeneous extent, Power Spectrum Density (PSD) of roughness is introduced and quantifies the random surface topographic structure. PSD obtained from different surface treatments of niobium, such as Buffered Chemical Polishing (BCP), Electropolishing (EP), Nano-Mechanical Polishing (NMP) and Barrel Centrifugal Polishing (CBP) are compared. A perturbation model is utilized to calculate the additional rough surface RF losses based on PSD statistical analysis. This model will not consider that superconductor becomes normal conducting at fields higher than transition field. One can calculate the RF power dissipation ratio between rough surface and ideal smooth surface within this field range from linear loss mechanisms.
 
 
MOPB030 Performance of First C100 Cryomodules for the CEBAF 12 GeV Upgrade Project 237
 
  • M.A. Drury, A. Burrill, G.K. Davis, J. Hogan, L.K. King, F. Marhauser, H. Park, J.P. Preble, C.E. Reece, A.V. Reilly, R.A. Rimmer, H. Wang, M. Wiseman
    JLAB, Newport News, Virginia, USA
 
  Funding: This manuscript has been authored by Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC05-06OR23177.
The Thomas Jefferson National Accelerator Facility is currently engaged in the 12 GeV Upgrade Project. The goal of the project is a doubling of the available beam energy of CEBAF from 6 GeV to 12 GeV. This increase in beam energy will be due primarily to the construction and installation of ten “C100” cryomodules in the CEBAF linacs. The C100 cryomodules are designed to deliver an average 108 MV each from a string of eight seven-cell, electropolished superconducting RF cavities operating at an average accelerating gradient of 19.2 MV/m. The new cryomodules fit in the same available linac space as the original CEBAF 20 MV cryomodules. Cryomodule production started in September 2010. Initial acceptance testing started in June 2011. The first two C100 cryomodules were installed and tested from August 2011 through October 2011, and successfully operated during the last period of the CEBAF 6 GeV era, which ended in May 2012. This paper will present the results of acceptance testing and commissioning of the C100 style cryomodules to date.
 
 
MOPB060 RF Surface Impedance Characterization of Potential New Materials for SRF-based Accelerators 312
 
  • B. P. Xiao, G.V. Eremeev, H.L. Phillips, C.E. Reece
    JLAB, Newport News, Virginia, USA
  • M.J. Kelley, B. P. Xiao
    The College of William and Mary, Williamsburg, USA
 
  Funding: Authored by Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC05-06OR23177.
In the development of new superconducting materials for possible use in SRF-based accelerators, it is useful to work with small candidate samples rather than complete resonant cavities. The recently commissioned Jefferson Lab rf Surface Impedance Characterization (SIC) system* can presently characterize the central region of 50 mm diameter disk samples of various materials from 2 to 40 K exposed to RF magnetic fields up to 14 mT at 7.4 GHz. We report the measurement results from bulk Nb, thin film Nb on Cu and sapphire substrates, and thin film MgB2 on sapphire substrate provided by colleagues at JLab and Temple University. We also report on efforts to extend the operating range to higher fields.
* B.P. Xiao, et al., RSI, 2011. 82: p. 056104
 
 
MOPB061 The New 2nd Generation SRF R&D Facility at Jefferson Lab: TEDF 315
 
  • C.E. Reece, A.V. Reilly
    JLAB, Newport News, Virginia, USA
 
  Funding: Authored by Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC05-06OR23177.
The US Department of Energy has funded a near-complete renovation of the SRF-based accelerator research and development facilities at Jefferson Lab. The project to accomplish this, the Technical and Engineering Development Facility (TEDF) Project has completed the first of two phases. An entirely new 3,300 m2 purpose-built SRF technical work facility has been constructed and is being occupied in summer of 2012. All SRF work processes with the exception of cryogenic testing has been relocated into the new building. All cavity fabrication, processing, thermal treatment, chemistry, cleaning, and assembly work is collected conveniently into a new LEED-certified building. An innovatively designed 750 m2 cleanroom/chemrooms suite provides long-term flexibility for support of multiple R&D and construction projects as well as continued process evolution. The detailed characteristics of this perhaps first 2nd-generation SRF facility will be described.
 
 
MOPB062 A New Internal Optical Profilometry System for Characterization of RF Cavity Surfaces – CYCLOPS 318
 
  • C.E. Reece, A.D. Palczewski, H. Tian
    JLAB, Newport News, Virginia, USA
 
  Funding: Authored by Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC05-06OR23177.
Jefferson Lab has received and commissioned a new interferometric optical profilometer specifically designed to provide internal surface mapping of elliptical rf cavities. The CavitY CaLibrated Optical Profilometry System – CYCLOPS – provides better than 2 micron lateral resolution and 0.1 micron surface height resolution of programmatically selected locations on the interior surface of multi-cell cavities. The system is being used to provide detailed characterization of surface topographic evolution as a function of applied surface treatments and to investigate particular localized defects. We also intend to use the system for 3D mapping of actual interior rf surface geometry for feedback to structure design model and fabrication tooling. First uses will be illustrated. CYCLOPS was developed and fabricated by MicroDynamics Inc., Woodstock, GA, USA.