SRF2011 - List of Authors (Clemens, W.A.)

Paper	Title	Page
TUPO029	Gradient Improvement by Removal of Identified Local Defects	436
	R.L. Geng, W.A. Clemens JLAB, Newport News, Virginia, USA C.A. Cooper Fermilab, Batavia, USA H. Hayano, K. Watanabe KEK, Ibaraki, Japan
	Funding: This work was authored by Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC05-06OR23177 Recent experience of ILC cavity processing and testing at Jefferson Lab has shown that some 9-cell cavities are quench limited at a gradient in the range of 15-25 MV/m. Further studies reveal that these quench limits are often correlated with sub-mm sized and highly localized geometrical defects at or near the equator weld. There are increasing evidence to show that these genetic defects have their origin in the material or in the electron beam welding process (for example due to weld irregularities or splatters on the RF surface and welding porosity underneath the surface). A local defect removal method has been proposed at Jefferson Lab by locally re-melting the niobium material. Several 1-cell cavities with known local defects have been treated by using the JLab local e-beam re-melting method, resulting in gradient and Q0 improvement. We also sent 9-cell cavities with known gradient limiting local defects to KEK for local grinding and to FNAL for global mechanical polishing. We report on the results of gradient improvements by removal of local defects in these cavities.

TUPO037	Study on Electro-Polishing Process by Niobium-Plate Sample With Artificial Pits	461
	T. Saeki, H. Hayano, S. Kato, M. Nishiwaki, M. Sawabe KEK, Ibaraki, Japan W.A. Clemens, R.L. Geng, R. Manus JLAB, Newport News, Virginia, USA P.V. Tyagi Sokendai, Ibaraki, Japan
	The Electro-polishing (EP) process is the best candidate of final surface-treatment for the production of ILC cavities. Nevertheless, the development of defects on the inner-surface of the Superconducting RF cavity during EP process has not been studied by experimental method. We made artificial pits on the surface of a Nb-plate sample and observed the development of the pit-shapes after each step of 30um-EP process where 120um was removed by EP in total. This article describes the results of this EP-test of Nb-sample with artificial pits.

Paper

Title

Page

Gradient Improvement by Removal of Identified Local Defects

436

R.L. Geng, W.A. Clemens
JLAB, Newport News, Virginia, USA
C.A. Cooper
Fermilab, Batavia, USA
H. Hayano, K. Watanabe
KEK, Ibaraki, Japan

Funding: This work was authored by Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC05-06OR23177
Recent experience of ILC cavity processing and testing at Jefferson Lab has shown that some 9-cell cavities are quench limited at a gradient in the range of 15-25 MV/m. Further studies reveal that these quench limits are often correlated with sub-mm sized and highly localized geometrical defects at or near the equator weld. There are increasing evidence to show that these genetic defects have their origin in the material or in the electron beam welding process (for example due to weld irregularities or splatters on the RF surface and welding porosity underneath the surface). A local defect removal method has been proposed at Jefferson Lab by locally re-melting the niobium material. Several 1-cell cavities with known local defects have been treated by using the JLab local e-beam re-melting method, resulting in gradient and Q0 improvement. We also sent 9-cell cavities with known gradient limiting local defects to KEK for local grinding and to FNAL for global mechanical polishing. We report on the results of gradient improvements by removal of local defects in these cavities.

TUPO037

Study on Electro-Polishing Process by Niobium-Plate Sample With Artificial Pits

461

T. Saeki, H. Hayano, S. Kato, M. Nishiwaki, M. Sawabe
KEK, Ibaraki, Japan
W.A. Clemens, R.L. Geng, R. Manus
JLAB, Newport News, Virginia, USA
P.V. Tyagi
Sokendai, Ibaraki, Japan

The Electro-polishing (EP) process is the best candidate of final surface-treatment for the production of ILC cavities. Nevertheless, the development of defects on the inner-surface of the Superconducting RF cavity during EP process has not been studied by experimental method. We made artificial pits on the surface of a Nb-plate sample and observed the development of the pit-shapes after each step of 30um-EP process where 120um was removed by EP in total. This article describes the results of this EP-test of Nb-sample with artificial pits.