LINAC2016 - List of Authors (Marhauser, F.)

Paper	Title	Page
MOPLR026	Material Qualification of LCLS-II Production Niobium Material Including RF and Flux Expulsion Measurements on Single Cell Cavities	199
	A.D. Palczewski, F. Marhauser JLab, Newport News, Virginia, USA A. Grassellino, S. Posen Fermilab, Batavia, Illinois, USA
	Funding: Work at JLab is supported by the U.S. Department of Energy under contract DE-AC05-06OR23177 and Fermilab is operated by Fermi Research Alliance, LLC under Contract No. De-AC02-07CH11359. It has been shown that cooldown details through transition temperature can significantly affect the amount of trapped magnetic flux in SRF cavities, which can lead to performance degradation proportional to the magnitude of the ambient magnetic field.[] It has also more recently been shown that depending on the exact material properties - even when the material used originated from the same batch from the same vendor - and subsequent heat treatment, the percent of flux trapped during a cool-down could vary widely for identical cool-down parameters.[] For LCLS-II, two material vendors have produced half of the niobium used for the cavity cells (Tokyo Denkai Co., Ltd. (TD) and Ningxia Orient Tantalum Industry Co., Ltd. (NX)). Both vendors delivered material well within specifications set out by the project (according to ASTM B 393-05), which allows yet some variation of material characteristics such as grain size and defect density. In this contribution, we present RF and magnetic flux expulsion measurements of four single cell cavities made out of two different niobium batches from each of the two LCLS-II material suppliers and draw conclusions on potential correlations of flux expulsion capability with material parameters. We present observations of limited flux expulsion in cavities made from the production material and treated with the baseline LCLS-II recipe. [] A. Romanenko et al J. Appl. Phys. 115, 184903 (2014) [**] S. Posenet et al., Journal of Applied Physics 119, 213903 (2016).
	Poster MOPLR026 [0.861 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-LINAC2016-MOPLR026
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MOPLR030	Electromagnetic Design of a Superconducting Twin Axis Cavity	203
	S.U. De Silva, J.R. Delayen, H. Park ODU, Norfolk, Virginia, USA A. Hutton, F. Marhauser, H. Park JLab, Newport News, Virginia, USA
	The twin-axis cavity is a new kind of rf superconducting cavity that consists of two parallel beam pipes, which can accelerate or decelerate two spatially separated beams in the same cavity. This configuration is particularly effective for high-current beams with low-energy electrons that will be used for bunched beam cooling of high-energy protons or ions. The new cavity geometry was designed to create a uniform accelerating or decelerating fields for both beams by utilizing a TM110 dipole mode. This paper presents the design rf optimization of a 1497 MHz twin-axis single-cell cavity, which is currently under fabrication.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-LINAC2016-MOPLR030
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THPLR037	Development of a Superconducting Twin Axis Cavity	932
SPWR031	use link to see paper's listing under its alternate paper code
	H. Park, A. Hutton, F. Marhauser JLab, Newport News, Virginia, USA S.U. De Silva, J.R. Delayen, H. Park ODU, Norfolk, Virginia, USA
	Superconducting cavities with two separate accelerating axes have been proposed in the past for energy recovery linac applications. While the study showed the advantages of such cavity, the designs present serious fabrication challenges. Hence the proposed cavities have never been built. The new design, elliptical twin cavity, proposed by Jefferson Lab and optimized by Center for Accelerator Science at Old Dominion University, allows similar level of engineering and fabrication techniques of a typical elliptical cavity. This paper describes preliminary LOM and HOM spectrum, engineering and fabrication processes of the twin axis cavity.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-LINAC2016-THPLR037
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Paper

Title

Page

Material Qualification of LCLS-II Production Niobium Material Including RF and Flux Expulsion Measurements on Single Cell Cavities

199

A.D. Palczewski, F. Marhauser
JLab, Newport News, Virginia, USA
A. Grassellino, S. Posen
Fermilab, Batavia, Illinois, USA

Funding: Work at JLab is supported by the U.S. Department of Energy under contract DE-AC05-06OR23177 and Fermilab is operated by Fermi Research Alliance, LLC under Contract No. De-AC02-07CH11359.
It has been shown that cooldown details through transition temperature can significantly affect the amount of trapped magnetic flux in SRF cavities, which can lead to performance degradation proportional to the magnitude of the ambient magnetic field.[*] It has also more recently been shown that depending on the exact material properties - even when the material used originated from the same batch from the same vendor - and subsequent heat treatment, the percent of flux trapped during a cool-down could vary widely for identical cool-down parameters.[**] For LCLS-II, two material vendors have produced half of the niobium used for the cavity cells (Tokyo Denkai Co., Ltd. (TD) and Ningxia Orient Tantalum Industry Co., Ltd. (NX)). Both vendors delivered material well within specifications set out by the project (according to ASTM B 393-05), which allows yet some variation of material characteristics such as grain size and defect density. In this contribution, we present RF and magnetic flux expulsion measurements of four single cell cavities made out of two different niobium batches from each of the two LCLS-II material suppliers and draw conclusions on potential correlations of flux expulsion capability with material parameters. We present observations of limited flux expulsion in cavities made from the production material and treated with the baseline LCLS-II recipe.
[*] A. Romanenko et al J. Appl. Phys. 115, 184903 (2014)
[**] S. Posenet et al., Journal of Applied Physics 119, 213903 (2016).

Poster MOPLR026 [0.861 MB]

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-LINAC2016-MOPLR026

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MOPLR030

Electromagnetic Design of a Superconducting Twin Axis Cavity

203

S.U. De Silva, J.R. Delayen, H. Park
ODU, Norfolk, Virginia, USA
A. Hutton, F. Marhauser, H. Park
JLab, Newport News, Virginia, USA

The twin-axis cavity is a new kind of rf superconducting cavity that consists of two parallel beam pipes, which can accelerate or decelerate two spatially separated beams in the same cavity. This configuration is particularly effective for high-current beams with low-energy electrons that will be used for bunched beam cooling of high-energy protons or ions. The new cavity geometry was designed to create a uniform accelerating or decelerating fields for both beams by utilizing a TM110 dipole mode. This paper presents the design rf optimization of a 1497 MHz twin-axis single-cell cavity, which is currently under fabrication.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-LINAC2016-MOPLR030

Export •

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

THPLR037

Development of a Superconducting Twin Axis Cavity

932

SPWR031

use link to see paper's listing under its alternate paper code

H. Park, A. Hutton, F. Marhauser
JLab, Newport News, Virginia, USA
S.U. De Silva, J.R. Delayen, H. Park
ODU, Norfolk, Virginia, USA

Superconducting cavities with two separate accelerating axes have been proposed in the past for energy recovery linac applications. While the study showed the advantages of such cavity, the designs present serious fabrication challenges. Hence the proposed cavities have never been built. The new design, elliptical twin cavity, proposed by Jefferson Lab and optimized by Center for Accelerator Science at Old Dominion University, allows similar level of engineering and fabrication techniques of a typical elliptical cavity. This paper describes preliminary LOM and HOM spectrum, engineering and fabrication processes of the twin axis cavity.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-LINAC2016-THPLR037

Export •

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