IPAC2012 - List of Authors (Valente-Feliciano, A-M.)

Paper	Title	Page
WEPPC096	Exploring the Effect of AL2O3 ALD Coating on a High Gradient ILC Single-Cell Cavity	2441
	G.V. Eremeev, A-M. Valente-Feliciano, A.T. Wu JLAB, Newport News, Virginia, USA D. Gu ODU, Norfolk, Virginia, USA
	Funding: Authored by Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC05-06OR23177. Encouraged by work at Argonne National Lab, we investigated atomic layer deposition technique for high gradient superconducting RF cavities at JLab with an ALD coating system of Old Dominion University located on the JLab site. The goal of this study was to look into the possibility of coating a dielectric layer on top of RF niobium surface at a lower temperature of 120 C as compared to ANL coatings at 200 C in order to preserve niobium pentooxide on niobium surface. The initial coatings showed complete, but non-uniform coatings of the surface with several areas exhibiting discoloration, which was probably due to the temperature variation during coatings. The initial coating showed a high RF losses, which were improved after discolored areas on the beam tubes were removed with HF rinse of the beam tubes only. The best result was 2·10⁹ low field Q0 and Eacc = 18 MV/m limited by available power.

WEPPC097	Development of Nb and Alternative Material Thin Films Tailored for SRF Applications	2444
	A-M. Valente-Feliciano, H.L. Phillips, C.E. Reece, J.K. Spradlin, X. Zhao JLAB, Newport News, Virginia, USA B. 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. Avenues for the production of thin films tailored for Superconducting RF (SRF) applications are showing promise with recent developments in vacuum deposition techniques using energetic ions. JLab is using energetic condensation via Electron Cyclotron Resonance and High Power Impulse Magnetron Sputtering (HiPIMS) for the development of Nb films and multilayer SIS (superconductor-insulator-superconductor) structures to reach bulk Nb performance and beyond. Nb films with RRR comparable to bulk values are readily produced. The influence of the deposition energy on the material and RF properties of the Nb thin film is investigated with the characterization of their surface, structure, superconducting properties and RF response. Nucleation studies are investigating the best conditions to create a favorable template for growing the final SRF surface. This paper presents results on surface impedance measurements correlated with surface and material characterization for Nb and multilayered SIS films produced on a variety of substrates.

WEPPC105	Study of Etching Rate Uniformity in SRF Cavities	2462
	J. Upadhyay, S. Popović, L. Vušković ODU, Norfolk, Virginia, USA H.L. Phillips, A-M. Valente-Feliciano JLAB, Newport News, Virginia, USA
	Plasma based surface modification is a promising alternative to wet etching of superconducting radio frequency (SRF) cavities. The crucial aspect of the technology development is dependence of the etching rate and surface roughness on the frequency of the power supply, pressure, power level, driven electrode shape and chlorine concentration in gas mixture during plasma processing. To optimize the plasma parameters, we are using a single cell cavity with 20 sample holders symmetrically distributed over the cell. These holders are used as diagnostic ports for the measurement of the plasma parameters and as holders for the samples to be etched. The plasma properties are highly correlated with the shape of the driven electrode and the percentage of chlorine concentration in Argon/chlorine gas mixtures. The effect of the plasma parameters and chlorine gas concentration are investigated at RF (100 MHz) and microwave (2.45 GHz) frequencies.

Paper

Title

Page

Exploring the Effect of AL2O3 ALD Coating on a High Gradient ILC Single-Cell Cavity

2441

G.V. Eremeev, A-M. Valente-Feliciano, A.T. Wu
JLAB, Newport News, Virginia, USA
D. Gu
ODU, Norfolk, Virginia, USA

Funding: Authored by Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC05-06OR23177.
Encouraged by work at Argonne National Lab, we investigated atomic layer deposition technique for high gradient superconducting RF cavities at JLab with an ALD coating system of Old Dominion University located on the JLab site. The goal of this study was to look into the possibility of coating a dielectric layer on top of RF niobium surface at a lower temperature of 120 C as compared to ANL coatings at 200 C in order to preserve niobium pentooxide on niobium surface. The initial coatings showed complete, but non-uniform coatings of the surface with several areas exhibiting discoloration, which was probably due to the temperature variation during coatings. The initial coating showed a high RF losses, which were improved after discolored areas on the beam tubes were removed with HF rinse of the beam tubes only. The best result was 2·10⁹ low field Q0 and Eacc = 18 MV/m limited by available power.

WEPPC097

Development of Nb and Alternative Material Thin Films Tailored for SRF Applications

2444

A-M. Valente-Feliciano, H.L. Phillips, C.E. Reece, J.K. Spradlin, X. Zhao
JLAB, Newport News, Virginia, USA
B. 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.
Avenues for the production of thin films tailored for Superconducting RF (SRF) applications are showing promise with recent developments in vacuum deposition techniques using energetic ions. JLab is using energetic condensation via Electron Cyclotron Resonance and High Power Impulse Magnetron Sputtering (HiPIMS) for the development of Nb films and multilayer SIS (superconductor-insulator-superconductor) structures to reach bulk Nb performance and beyond. Nb films with RRR comparable to bulk values are readily produced. The influence of the deposition energy on the material and RF properties of the Nb thin film is investigated with the characterization of their surface, structure, superconducting properties and RF response. Nucleation studies are investigating the best conditions to create a favorable template for growing the final SRF surface. This paper presents results on surface impedance measurements correlated with surface and material characterization for Nb and multilayered SIS films produced on a variety of substrates.

WEPPC105

Study of Etching Rate Uniformity in SRF Cavities

2462

J. Upadhyay, S. Popović, L. Vušković
ODU, Norfolk, Virginia, USA
H.L. Phillips, A-M. Valente-Feliciano
JLAB, Newport News, Virginia, USA

Plasma based surface modification is a promising alternative to wet etching of superconducting radio frequency (SRF) cavities. The crucial aspect of the technology development is dependence of the etching rate and surface roughness on the frequency of the power supply, pressure, power level, driven electrode shape and chlorine concentration in gas mixture during plasma processing. To optimize the plasma parameters, we are using a single cell cavity with 20 sample holders symmetrically distributed over the cell. These holders are used as diagnostic ports for the measurement of the plasma parameters and as holders for the samples to be etched. The plasma properties are highly correlated with the shape of the driven electrode and the percentage of chlorine concentration in Argon/chlorine gas mixtures. The effect of the plasma parameters and chlorine gas concentration are investigated at RF (100 MHz) and microwave (2.45 GHz) frequencies.