IPAC2012 - List of Authors (Kelley, M.J.)

Paper	Title	Page
WEEPPB011	Analysis of High Field Non-Linear Losses on SRF Surfaces Due to Specific Topographic Roughness	2188
	C. Xu The College of William and Mary, Williamsburg, USA M.J. Kelley, C.E. Reece, C. Xu JLAB, Newport News, Virginia, USA
	Funding: This work is authored by Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC05-06OR23177. The high-field performance of SRF cavities will eventually be limited by the realization of fundamental material limits, whether it be Hc1 or Hsh, or some derivative thereof, at which the superconductivity is lost. Before reaching this fundamental field limit at the macro level, it must be encountered at localized, perhaps microscopic, sites of field enhancement due to local topography. If such sites are small enough, they may produce thermally stabilized normal-conducting regions which contribute non-linear losses when viewed from the macro resonant field perspective, and thus produce degradation in Q0. We have undertaken a calculation of local surface magnetic field enhancement from specific fine topographic structure by conformal mapping method and numerically. A solution of the resulting normal conducting volume has been derived and the corresponding RF ohmic loss simulated.

THPPC093	SRF Cavity Surface Topography Characterization Using Replica Techniques	3497
	C. Xu, M.J. Kelley The College of William and Mary, Williamsburg, USA C.E. Reece JLAB, Newport News, Virginia, USA
	Funding: This work is authored by Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC05-06OR23177. To better understand the roll of topography on SRF cavity performance, we seek to obtain detailed topographic information from the curved practical cavity surfaces. Replicas taken from a cavity interior surface provide internal surface molds for fine Atomic Force Microscopy (AFM) and stylus profilometry. In this study, we confirm the replica resolution both on surface local defects such as grain boundary and etching pits and compare the surface uniform roughness with the aid of Power Spectral Density (PSD) where we can statistically obtain roughness parameters at different scales. A series of sampling locations are at the same magnetic field chosen at the same latitude on a single cell cavity to confirm the uniformity. Another series of sampling locations at different magnetic field amplitudes are chosen for this replica on the same cavity for later power loss calculation. We also show that application of the replica followed by rinsing does not adversely affect the cavity performance.

Paper

Title

Page

Analysis of High Field Non-Linear Losses on SRF Surfaces Due to Specific Topographic Roughness

2188

C. Xu
The College of William and Mary, Williamsburg, USA
M.J. Kelley, C.E. Reece, C. Xu
JLAB, Newport News, Virginia, USA

Funding: This work is authored by Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC05-06OR23177.
The high-field performance of SRF cavities will eventually be limited by the realization of fundamental material limits, whether it be Hc1 or Hsh, or some derivative thereof, at which the superconductivity is lost. Before reaching this fundamental field limit at the macro level, it must be encountered at localized, perhaps microscopic, sites of field enhancement due to local topography. If such sites are small enough, they may produce thermally stabilized normal-conducting regions which contribute non-linear losses when viewed from the macro resonant field perspective, and thus produce degradation in Q0. We have undertaken a calculation of local surface magnetic field enhancement from specific fine topographic structure by conformal mapping method and numerically. A solution of the resulting normal conducting volume has been derived and the corresponding RF ohmic loss simulated.

THPPC093

SRF Cavity Surface Topography Characterization Using Replica Techniques

3497

C. Xu, M.J. Kelley
The College of William and Mary, Williamsburg, USA
C.E. Reece
JLAB, Newport News, Virginia, USA

Funding: This work is authored by Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC05-06OR23177.
To better understand the roll of topography on SRF cavity performance, we seek to obtain detailed topographic information from the curved practical cavity surfaces. Replicas taken from a cavity interior surface provide internal surface molds for fine Atomic Force Microscopy (AFM) and stylus profilometry. In this study, we confirm the replica resolution both on surface local defects such as grain boundary and etching pits and compare the surface uniform roughness with the aid of Power Spectral Density (PSD) where we can statistically obtain roughness parameters at different scales. A series of sampling locations are at the same magnetic field chosen at the same latitude on a single cell cavity to confirm the uniformity. Another series of sampling locations at different magnetic field amplitudes are chosen for this replica on the same cavity for later power loss calculation. We also show that application of the replica followed by rinsing does not adversely affect the cavity performance.