Antoine C.

Paper	Title	Page
TU204	Review of SRF Materials Workshop	94
	G. Wu, L. Cooley, H. Edwards Fermilab C. Antoine CEA-Saclay
	The performance of niobium cavities has approached the theoretical hard limit. Yet the consistent achievement of higher performing cavities remains the greatest challenge. To further understand the basic materials science, a workshop was held at Fermilab in May 2007 to present and discuss the fundamental and experimental limitations, and propose new ideas.
	Slides(PDF)
TUP49	ECR Plasma Cleaning: An In-situ Processing Technique for RF Cavities	243
	G. Wu, H. Jiang, T. Khabiboulline, I. Pechenezhskiy, T. Koeth, J. Reid, W. Muranyi, B. Tennis, E. Harms, Y. Terechkine, H. Edwards, D. Mitchell, A. Rowe, C. Boffo, C. Cooper, L. Cooley, R. Schuessler Fermilab W. -D. Moeller DESY Hamburg C. Antoine CEA-Saclay A. Romanenko Cornell University
	A condition for Electron Cyclotron Resonance (ECR) can be established inside a fully assembled RF cavity without the need for removing high-power couplers. As such, plasma generated by this process can be used as a final cleaning step, or as an alternative cleaning step in place of other techniques. We will describe the current effort to study plasma cleaning by ECR in a 3.9GHz cavity.
TUP64	Initial Tests of Atomic Layer Deposition (ald) in Superconducting RF Systems	285
	M. Pellin, J. Elam, J. Moore, J. Norem ANL C. Antoine CEA-Saclay L. Cooley Fermilab T. Prolier, J. Zasadzinski IIT R. Rimmer JLab
	Atomic Layer Deposition (ALD) is a method of synthesizing materials in single atomic layers. We are studying this technique as a method of producing highly controlled surfaces for superconducting RF systems. We have begun tests of ALD coatings of single cells that will involve RF measurements of a cell before and after coating at Argonne. In addition to the tests on complete cells, we are also beginning a program of point contact tunneling measurements to determine the properties of the superconductors at the interface between the bulk niobium and the oxide layer. We describe the method, and tests we are beginning with single cell resonators and small samples.
TUP80	Single Cell Electro-Polishing at CEA Saclay: First Results	343
	F. Eozenou, M. Bruchon, Y. Gasser, Y. Boudigou, B. Visentin, J. P. Charrier, S. Berry, C. Antoine CEA-Saclay D. Reschke DESY Hamburg
	The goal of the Work Package 5.1 of the CARE SRF program is to study electro-polishing (EP) of niobium and thus isolate an ideal set of parameters for 1.3 GHz single cell cavity treatment that should be applied to industry. The more challenging aspect concerns acid composition's optimisation, made of a mixture of hydrofluoric (HF) and sulfuric (H2SO4) acids with possible additional water. Preliminary experiments have been carried out on samples to guide the program on single-cell cavities. In that way, a set-up for horizontal EP has been installed in our laboratory. This set-up has been successfully qualified with the standard recipe used at DESY since the first EP on TESLA-shaped cavity has reached an excellent gradient above 42 MV/m. The search for new parameters makes then sense. Different configurations have been investigated: higher temperature, lower voltage and new acids' concentrations. Dummy cavities have been electropolished with a new mixture: 1vol HF(40w%) - 2vol H2SO4(95w%) - 7vol H2O, (1-2-7) with high water content. Different cavities have also been electro-polished and results including surface aspect, RF measurements and impurities forming will be related.
WE105	An Investigation of the influence of grain boundaries on flux penetration in high purity large grain niobium for particle accelerators
	Z. H. Sung, P. J. Lee, A. Gurevich, A. A. Polyanskii, D. C. Larbalestier NHMFL, FSU C. Antoine Saclay C. Boffo, H. T. Edwards Fermilab
	Grain boundaries (GBs) in niobium cavities may be one of the important causes of extra power dissipation by reducing the field of first vortex penetration because the superconducting gap and the local depinning current density Jb on the GB are reduced. It is therefore important to measure the critical current density Jb and investigate the microstructure at grain boundaries to better understand whether or how grain boundary weakness can affect SRF cavity performance. Our experiments are currently correlating the global (by magnetometer) and local magnetization (by magneto-optical imaging), transport critical current density and atomic scale structure of Nb samples so that a DC analog of the RF surface currents can be developed for real Nb surfaces prepared using cavity optimization treatments. To measure Jb we apply transport current as a function of perpendicular magnetic field on BCP-treated bi-crystals of as-received, high-purity, large-grain niobium sheet. After measurement, we thin the very same grain boundary so that we image the microstructure of the external surface adjoining each GB by scanning transmission electron microscopy (STEM) in conjunction with EELS (Electron Energy Loss Spectroscopy). EELS has shown the presence of stoichiometric niobium oxide on the topmost layers, well within the typical superconducting niobium penetration depth (~ 50nm). 1. now at SACLAY
	Slides(PDF)