IPAC2015 - List of Authors (Vuskovic, L.)

Paper	Title	Page
WEPWI033	Effects of Plasma Processing on Secondary Electron Yield of Niobium Samples	3558
	M. Basovic, S. Popović, M. Tomovic, L. Vušković ODU, Norfolk, Virginia, USA F. Čučkov, A. Samolov University of Massachusetts Boston, Boston, Massachusetts, USA
	Impurities deposited on the surface of Nb during both the forming and welding of accelerator cavities add to the imperfections of the sheet metal, which then affects the overall performance of the cavities. This leads to a drop in the Q factor and limits the maximum acceleration gradient achievable per unit length of the cavities. The performance can be improved either by adjusting the fabrication and preparation parameters, or by mitigating the effects of fabrication and preparation techniques used. We have developed the experimental setup to determine Secondary Electron Yield (SEY) from the surface of Nb samples. Our aim is to show the effect of plasma processing on the SEY of Nb. The setup measures the secondary electron energy distribution at various incident angles as measured between the electron beam and the surface of the sample. The goal is to determine the SEY on non-treated and plasma treated surface of electron beam welded samples. Here we describe the experimental setup, plasma treatment device, and fabrication and processing of the Nb samples.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-WEPWI033
Export •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

WEPWI040	Experiment and Results on Plasma Etching of SRF Cavities	3581
	J. Upadhyay, J.J. Peshl, S. Popović, L. Vušković ODU, Norfolk, Virginia, USA D.S. Im Old Dominion University, Norfolk, Virginia, USA H.L. Phillips, A-M. Valente-Feliciano JLab, Newport News, Virginia, USA
	The inner surfaces of SRF cavities are currently chemically treated (etched or electro polished) to achieve the state of the art RF performance. We designed an apparatus and developed a method for plasma etching of the inner surface for SRF cavities. The process parameters (pressure, power, gas concentration, diameter and shape of the inner electrode, temperature and positive dc bias at inner electrode) are optimized for cylindrical geometry. The etch rate non-uniformity has been overcome by simultaneous translation of the gas point-of-entry and the inner electrode during the processing. A single cell SRF cavity has been centrifugally barrel polished, chemically etched and RF tested to establish a baseline performance. This cavity is plasma etched and RF tested afterwards. The effect of plasma etching on the RF performance of this cavity will be presented and discussed.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-WEPWI040
Export •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

Paper

Title

Page

Effects of Plasma Processing on Secondary Electron Yield of Niobium Samples

3558

M. Basovic, S. Popović, M. Tomovic, L. Vušković
ODU, Norfolk, Virginia, USA
F. Čučkov, A. Samolov
University of Massachusetts Boston, Boston, Massachusetts, USA

Impurities deposited on the surface of Nb during both the forming and welding of accelerator cavities add to the imperfections of the sheet metal, which then affects the overall performance of the cavities. This leads to a drop in the Q factor and limits the maximum acceleration gradient achievable per unit length of the cavities. The performance can be improved either by adjusting the fabrication and preparation parameters, or by mitigating the effects of fabrication and preparation techniques used. We have developed the experimental setup to determine Secondary Electron Yield (SEY) from the surface of Nb samples. Our aim is to show the effect of plasma processing on the SEY of Nb. The setup measures the secondary electron energy distribution at various incident angles as measured between the electron beam and the surface of the sample. The goal is to determine the SEY on non-treated and plasma treated surface of electron beam welded samples. Here we describe the experimental setup, plasma treatment device, and fabrication and processing of the Nb samples.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-WEPWI033

Export •

reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

WEPWI040

Experiment and Results on Plasma Etching of SRF Cavities

3581

J. Upadhyay, J.J. Peshl, S. Popović, L. Vušković
ODU, Norfolk, Virginia, USA
D.S. Im
Old Dominion University, Norfolk, Virginia, USA
H.L. Phillips, A-M. Valente-Feliciano
JLab, Newport News, Virginia, USA

The inner surfaces of SRF cavities are currently chemically treated (etched or electro polished) to achieve the state of the art RF performance. We designed an apparatus and developed a method for plasma etching of the inner surface for SRF cavities. The process parameters (pressure, power, gas concentration, diameter and shape of the inner electrode, temperature and positive dc bias at inner electrode) are optimized for cylindrical geometry. The etch rate non-uniformity has been overcome by simultaneous translation of the gas point-of-entry and the inner electrode during the processing. A single cell SRF cavity has been centrifugally barrel polished, chemically etched and RF tested to establish a baseline performance. This cavity is plasma etched and RF tested afterwards. The effect of plasma etching on the RF performance of this cavity will be presented and discussed.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-WEPWI040

Export •

reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)