SRF2019 - List of Authors (Geng, R.L.)

Paper	Title	Page
MOP064	Performance of First Prototype Multi-Cell Low-Surface-Field Shape Cavity	222
	R.L. Geng JLab, Newport News, Virginia, USA Y. Fuwa, Y. Iwashita Kyoto ICR, Uji, Kyoto, Japan H. Hayano KEK, Ibaraki, Japan H. Ito Sokendai, Ibaraki, Japan Z. Li SLAC, Menlo Park, California, USA
	The idea of cavity shaping for higher ultimate acceleration gradients has been proposed for some time, Low Loss/Ichiro and Re-entrant being examples, both seeking a lower Hpk/E_acc at the expense of a higher Epk/E_acc. While experimental verification in single-cell cavities of those shapes was very successful including the record gradient of 59 MV/m, pushing multi-cell cavities of those shapes to higher gradients was prevented by field emission. The Low-Surface-Field (LSF) shape seeks not only a lower Hpk/E_acc but also a lower Epk/E_acc, therefore it has the advantage of raising ultimate gradient at reduced field emission. The first multi-cell LSF shape prototype cavity was built using the standard forming and welding techniques. RF tests have been carried out, following standard ILC TDR baseline surface processing and treatment recipe. Three out of five cells achieved Hpk values corresponding to E_acc 50 MV/m. The current limit is the field emission in end cells. Instrumented testing following end-cell wiping and HPR with larger nozzles is in progress. We will present detailed experimental results and preparation procedures.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2019-MOP064
About •	paper received ※ 24 June 2019 paper accepted ※ 30 June 2019 issue date ※ 14 August 2019
Export •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

TUP053	Optimal Thermal Gradient for Flux Expulsion in 600°C Heat-treated CEBAF 12 GeV Upgrade Cavities	550
	R.L. Geng, F. Marhauser, P.D. Owen JLab, Newport News, Virginia, USA
	We will present results on measurement of flux expulsion in CEBAF 12 GeV upgrade cavities and original CEBAF cavities and the search for optimal thermal gradient for reducing the trapped flux in cavities installed in CEBAF linacs. Preliminary measurements of one C100 cavities has shown that a nearly perfect flux expulsion can be achieved at an optimal thermal gradient - a surprising result contrary to the expectation of zero flux expulsion for 600°C heat treated niobium cavities. These results could lead to a cost-effective path for improving the quality factor of cavities installed in CEBAF and ultimately saving accelerator operation cost.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2019-TUP053
About •	paper received ※ 24 June 2019 paper accepted ※ 29 June 2019 issue date ※ 14 August 2019
Export •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

Paper

Title

Page

Performance of First Prototype Multi-Cell Low-Surface-Field Shape Cavity

222

R.L. Geng
JLab, Newport News, Virginia, USA
Y. Fuwa, Y. Iwashita
Kyoto ICR, Uji, Kyoto, Japan
H. Hayano
KEK, Ibaraki, Japan
H. Ito
Sokendai, Ibaraki, Japan
Z. Li
SLAC, Menlo Park, California, USA

The idea of cavity shaping for higher ultimate acceleration gradients has been proposed for some time, Low Loss/Ichiro and Re-entrant being examples, both seeking a lower Hpk/E_acc at the expense of a higher Epk/E_acc. While experimental verification in single-cell cavities of those shapes was very successful including the record gradient of 59 MV/m, pushing multi-cell cavities of those shapes to higher gradients was prevented by field emission. The Low-Surface-Field (LSF) shape seeks not only a lower Hpk/E_acc but also a lower Epk/E_acc, therefore it has the advantage of raising ultimate gradient at reduced field emission. The first multi-cell LSF shape prototype cavity was built using the standard forming and welding techniques. RF tests have been carried out, following standard ILC TDR baseline surface processing and treatment recipe. Three out of five cells achieved Hpk values corresponding to E_acc 50 MV/m. The current limit is the field emission in end cells. Instrumented testing following end-cell wiping and HPR with larger nozzles is in progress. We will present detailed experimental results and preparation procedures.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2019-MOP064

About •

paper received ※ 24 June 2019 paper accepted ※ 30 June 2019 issue date ※ 14 August 2019

Export •

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

TUP053

Optimal Thermal Gradient for Flux Expulsion in 600°C Heat-treated CEBAF 12 GeV Upgrade Cavities

550

R.L. Geng, F. Marhauser, P.D. Owen
JLab, Newport News, Virginia, USA

We will present results on measurement of flux expulsion in CEBAF 12 GeV upgrade cavities and original CEBAF cavities and the search for optimal thermal gradient for reducing the trapped flux in cavities installed in CEBAF linacs. Preliminary measurements of one C100 cavities has shown that a nearly perfect flux expulsion can be achieved at an optimal thermal gradient - a surprising result contrary to the expectation of zero flux expulsion for 600°C heat treated niobium cavities. These results could lead to a cost-effective path for improving the quality factor of cavities installed in CEBAF and ultimately saving accelerator operation cost.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2019-TUP053

About •

paper received ※ 24 June 2019 paper accepted ※ 29 June 2019 issue date ※ 14 August 2019

Export •

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